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Human Neuroanatomy--J. Nolte chs 1-15,17


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Define: white matter
a collection of myelinated fibers (surrounds gray matter in the spinal cord)
Define: gray matter
collections of cell bodies and dendrites
Define: nucleus
discrete collection of cell bodies
Define: ganglion
collection of neuronal cell bodies outside of the CNS
Define: cortex
extensive surface layer of cell bodies (like cerebral cortex)
Define: tract

what does the two-part name indicate?
discrete collection of fibers (in the white matter)

first part of name indicates where tract originated and second part indicates where it terminates
Indicate whether each term is a collection of neuronal cell bodies or collection of axons: fasciculus, lemniscus, peduncle
all three are collections of fibers (axons)
List major subdivisions of CNS.
brain and spinal cord
List major subdivisions of brain.
cerebrum, cerebellum, brainstem
what does the cerebellum do?
uses sensory input to design movement and to correct movements once initiated
What are the three major subdivisions of the brainstem?
midbrain, pons, medulla
What are the primary functions of the brainstem?
initial processing of information from cranial nerves 3-12 which it then sends to thalamus, cranial nerve reflexes (ex. eye blink), getting motor commands out through cranial nerves, long tract functions, regulating consciousness & sleep/wake cycles (via RAS)
What are the two major subdivisions of the cerebrum?
2 cerebral hemispheres & diencephalon
What are the two major subdivisions of the diencephalon?
thalamus, hypothalamus
What are the three major subdivisions of each cerebral hemisphere
cerebral cortex, basal ganglia, hippocampus & amygdala
What do the hypothalamus and thalamus do?
hypothalamus- control center for autonomic nervous system, controls drive related behavior

thalamus- major relay station for all information (except olfactory) to reach the cerebral cortex
list the 5 lobe divisions of the cerebral cortex
frontal lobe, temporal lobe, limbic lobe, parietal lobe, occipital lobe
list the two major subdivisions of the basal ganglia
caudate nucleus, lenticular nucleus
what is the major function of the basal ganglia
involved in motor function, initiating and stopping movement, muscle tone, involuntary movement
what are the major functions of the hippocampus and amygdala?
part of limbic system, involved in drives, emotions, memory
what are the primary functions of the frontal lobe?
motor control (motor cortex), expressive language (Broca's Area), EF
What are the primary functions of the temporal lobe?
auditory processing (auditory cortex), Receptive language (wernicke's area), visual association (cortex), learning & memory
What are the primary functions of the parietal lobe?
primary sensory (somatosensory cortex), spatial orientation & perception, helps with receptive language
What are the primary functions of the occipital lobe?
vision processing (primary visual cortex)
What are the primary functions of the limbic lobe/system?
emotional responses, drive related behavior, memory
What are the major sulci dividing each of the lobes (both laterally and medially)?
outside view of brain (laterally): frontal--parietal (central sulcus), front-parietal--temporal (lateral sulcus)
interior view of brain (medially): parietal--occipital (parietooccipital sulcus), temporal--parietal--limbic (calcarine sulcus), frontal--limbic (cingulate sulcus)
List the location of the motor, somatosensory, auditory, and visual cortex.
motor-frontal lobe, somatosensory-parietal lobe, auditory-temporal lobe, visual-occipital lobe
List the general functions of the spinal cord.
processes info coming in from periphery (body) and sends it on to places like thalamus, contains motor neurons controlling skeletal muscle, involved in spinal reflex loop, contains long tract origination and/or termination
Where do afferent fibers enter and where do efferent fibers leave?
afferent fibers enter dorsal roots, efferent fibers leave ventral roots
What does white matter contain? What does gray matter contain?
white matter contains long ascending and descending tracts and fibers interconnecting different spinal levels. Gray matter contains synaptic processing areas, interneurons, cells of origin of tract and ventral root fibers
List the effects of damage to primary afferents (in terms of side affected, strength, reflexes, sensation)
side = ipsilateral
strength = no change
reflexes = diminished
sensation = diminished or lost
List the effects of damage to lower motor neurons (in terms of side affected, strength, reflexes, sensation)
side = ipsilateral
strength = diminished
reflexes = diminished
sensation = no change
List the effects of damage to sensory pathways/sensory cortex (in terms of side affected, strength, reflexes, sensation)
side = contralateral
strength = no change
reflexes = no change
sensation = diminished
List the effects of damage to cerebellum (in terms of side affected, strength, reflexes, sensation)
side = ipsilateral
strength = no change
reflexes = no change
sensation = no change
List the effects of damage to basal ganglia (in terms of side affected, strength, reflexes, sensation)
side = contralateral
strength = no change
reflexes = no change
sensation = no change
List the effects of damage to upper motor neurons (in terms of side affected, strength, reflexes, sensation)
side = contralateral
strength = diminished
reflexes = increased
sensation = no change
define: primary afferent
neurons with cell bodies in the PNS and axons that project to ipsilateral CNS, only way to convey sensory information from PNS to CNS, end on second order neurons
define: motor neurons
leave CNS in ventral roots or cranial nerves and innervate ipsilateral skeletal muscle (lower motor neurons), cell bodies and central process end ipsilateral
3 things that sensory information from PNS to CNS (via primary afferent) does:
feed into reflex arcs, distributed to contralateral cerebral cortex (via relay in thalamus), distributed to ipsilateral cerebellum (via second order neuron)
which fibers cross midline? primary afferents, second order neurons, thalamocortical pathways
second order neurons (at entry to CNS for spinothalamic tract, and at medulla for touch and position tract)
describe cerebellar pathways
each side of cerebellum related to ipsilateral side of body, no relay in thalamus necessary from cord to cerebellum
sensory systems other than somatosensory (what do their pathways look like?)
some project bilaterally to thalamus (ex. ears)
upper motor neurons: what tract is this, where does it cross?
important for voluntary movement, this is corticospinal tract, crosses at pyramidal decussation (so contralateral cortex controls motor movement in PNS)
cerebellar pathways
influences motor control, related to ipsilateral side of body but no direct output to spinal cord, projects to contralateral cortex (via relay in contralateral thalamus), also receives input from cortex via pons)
basal ganglia pathways
connected to thalamus and cortex on same side (all related to contralateral side of body)
Describe origin of neural crest cells and indicate fate of these cells
neural crest cells grow at apex of each neural fold (neural fold turns into neural tube which zips up and detaches), neural crest cells become detached layer between neural tube and surface ectoderm, go on to form neurons and glial cells of PNS (sensory ganglion, postganglionic autonomic neurons, schwann cells, satellite cells in ganglia, meningeal cells)
name the primary and secondary vesicle from which each of the following are derived: medulla, pons, midbrain, cerebellum, thalamus, hypothalamus, pineal gland, retina, cerebral cortex, hippocampus, caudate nucleus, putamen, amygdala
prosencephalon-telencephalon (cerebral cortex, caudate nucleus, putamen, amygdala), prosencephalon-diencephalon (thalamus, hypothalamus, retina), mesencephalon (remains undivided)(midbrain), rhombencephalon-metencephalon (pons, cerebellum), rhombencephalon-myelencephalon (medulla)
which primary and secondary vesicles give rise to the ventricles of the brain?
prosencephalon-telencephalon (lateral ventricles), prosencephalon-diencephalon (third ventricle), mesencephalon (undivided)(cerebral aqueduct), rhombencephalon-metencephalon & myelencephalon (fourth ventricle)
describe the relationship among the alar and basal plate, sulcus limitans and sensory and motor nuclei of the central nervous system
sulcus limitans is groove in middle of spinal cord and brainstem, separates neuronal cell bodies into alar plate (dorsal horn of cord) where sensory neurons terminate, and basal plate (ventral horn) where cell bodies of motor neurons live
how is dorsal/ventral relationship of the spinal alar and basal plates altered during development of brainstem?
at level of brainstem, alar plates move lateral to basal plate (from dorsal-ventral relationship in spinal cord)
describe the sequence of events leading to the formation of a C-shaped cerebrum from a linear tube
telencephalon folds down alongside diencephalon until two fuse, telencephalic surface overlying area of fusion turns into insula which becomes more and more hidden as cortex continues to grow completely encircling the insula
describe the development of the choroid plexus
formed where inner lining (ependyma) and outer covering (pia) of CNS are directly applied to each other, ependymal cells form a secretory epithelium, adjacent cells joined by tight junctions for diffusion barrier, vascular tissue invaginates pia-ependyma membrane
describe the cellular composition of the choroid plexus, the kinds of spaces adjacent to it, and its location in the nervous system
made of ependyma cells up against pia mater, near choroid fissre (subarachnoid space), located in roof of 3rd ventricle, roof of 4th ventricle, follows C-shape of lateral ventricles too
what are come CNS abnormalities resulting from defective neural tube closure?
fatal deformity (complete failure to close)-craniorachischisis, failure of tail end closure (spina bifida--myleomeningocele) cord and meninges in sac-like cavity on back (often accompanied by Arnold Chiara malformation- cerebellum and caudal brainstem pushed down into foramen magnum), head end of tube fails to close = anenecephaly: much of each cerebral hemisphere is absent
what are some CNS abnormalities resulting from defective differentiation of the forebrain?
holoprosencephaly (failure of prosencephalon to separate into diencephalon and paired telencephalic vesicles, defects associated with marked facial abnormalities
what are some CNS abnormalities resulting from defective neuronal proliferation or migration?
malformed gyri and sulci, misplaced gray matter
list the parts of a typical neuron and assign a function to each part
cell body supports the metabolic and synthetic needs of the cell, dendrites are sites that receive info from other neurons via synapses, axon conducts info away from cell body, axon terminals form synapses on other neurons
describe the role of the major cytoskeletal components of the neuron
microtubules, neurofilaments, and microfilaments help neurons maintain shape, microtubules also transport things (mitochondria, lyosomes, vesicles of neurotransmitter precursors, etc) around cell via axonal transport
identify the cells that make myelin, what is the role of myelin in conduction of electrical signals
schwann cells in PNS wrap around axon (nodes of ranvier are spaces between schwann cells where action potentials are regenerated), myelin allows action potentials to be conducted rapidly, in CNS oligodendrocytes form myelin sheaths
indicate differences between cells that make myelin in the CNS and PNS
in PNS they are schwann cells, in CNS they are oligodendrocytes
name and describe the locations and functions of non-myelin producing glial cells in the CNS
Astrocytes buffer the ionic composition of extracellular fluids, support neuronal metabolism and repair injured areas of nervous system, microglia help clean up after injury, ependymal cells line ventricles and are specialized in certain places as choroid epithelium to make CSF
compare and contrast equilibrium potentials and steady state potentials
equilibrium requires no energy, the same amount of one ion is flowing in as flowing out, no concentration changes, steady state potential is when small inflow of Na+ is balanced by small outflow of K+, opposite current flows of different ions result in concentration changes, membrane potential = -65mv
describe how the nernst equation predicts the value of the equilibrium potential and how the goldman equation predicts the steady state potential
potassium equilibrium potential can be calculated by nernst equation knowing the intra and extracellular K+ concentrations, the temperature and some physical constants, the goldman equation predicts the steady state potential by describing a weighted average of the K+, Na+, and Cl- with permeability as the weighting factor, as permeability to a particular ion increases, the membrane potential will move closer to the equilibrium potential for that ion
describe the determinants of spatial and temporal summation
temporal summation- time constant is how long it takes current to reach final voltage, depends on membrane # of open channels (conductance and resistance), many inputs close together in time summate. spatial summation- space constant is length traveled before current reaches 37% of its initial value, signal becomes smaller with distance, conductance determines how much current leaks out over space, mutliple inputs spatially near each other will summate
indicate the implications for spatial and temporal summation for the spread and interaction of slow potentials
slow potential currents near each other spatially or temporally can summate and if they add up to exceed threshold then will turn into action potential to send current over long distances
describe the changes in ion channel configurations that underlie action potentials. How do these produce absolute and relative refractory periods and the role of refractory periods in determining the directionality and frequency of action potentials
Na+ channels open and begin to depolarize membrane, outward flow of K+ ions balances inward flow of Na+ at first but then Na+ begins to exceed, so much that membrane hits threshold and action potential occurs. Na+ channels inactivate and close (absolute refractory), K+ channels remain open causing hyperpolarization, Na+ channels begin to return to resting state, some ready to open again (relative refractory period), another action potential cannot occur during absolute refractory period, action potentials spread actively away from cell body and passively back toward cell body
compare and contrast the propagation of action potentials in myelinated and unmyelinated axons
myelin allows action potentials to be propagated faster down axon and are regenerated at nodes of ranvier (space between myelinated oligodendrocytes/schwann cells) so do not diminish over space & time
describe the structure and function of a typical chemical synapse
presynaptic terminals hold chemical messengers (neurotransmitters) ready for release with action potential, postsynaptically neurotransmitter receptor sites are anchored by microfilaments ready to take up NT that has traveled across synaptic cleft
list the major neurotransmitters and their typical post-synaptic effects
post-synaptic impact determined by receptor site but acetylcholine- both excitatory and inhibitory, glutamate- usually excitatory, GABA- usually inhibitory, aspartate- usually excitatory, glycine- usually inhibitory
compare and contrast the synthesis, release, and post-synaptic effects of small molecule and peptide neurotransmitters
small molecule made in synaptic endings, peptides made in cell body and transported to synaptic endings, peptides mediate rapid point to point transmission in PNS, small molecules do rapid pt to pt transmission in CNS
describe the structure and function of a typical electrical synapse
electrical synapses (gap junctions) where neurons are very close together spatially so current flows directly from one to another (not common in humans)
define: adequate stimulus, transduction, receptor potential
adequate stimulus- the kind of stimulus a receptor best responds to, transduction- process of turning physical stimulus into electrical signal that can be passed along, receptor potential- slow, graded electrical potential resulting from transduction process
how do receptors encode the nature, location, intensity, and duration of stimuli
receptor responds to adequate stimulus (if responds then can know the nature of the stimulus), know location from receptive field, intensity is known from sensory threshold (lowest stimulus intensity that can be detected), duration known by duration of receptor potential (slow and rapidly adapting receptors)
describe the anatomical organization of sensory receptors
zone for receiving stimuli, zone where info is passed on toward CNS, zone w/ mitochondria that support the energy requirements of transduction process
compare and contrast the properties of receptors with and without long axons
those without long axons synapse on primary afferents (can either depolarize or hyperpolarize in response to stimulus), long axon receptors produce receptor potential that spreads to trigger zone and causes action potential (all depolarizing)
compare and contrast mechanisms used by sensory receptors and postsynaptic membranes to generate electrical signals
sensory receptors are sensitive to some stimulus rather than to transmitter released by another neuron(post-synaptic membrane). Some are directly ion gated and some are G-protein coupled channel gated.
compare and contrast the functional properties of muscule spindles and golgi tendon organs (include a description of the role of gamma motor neurons)
muscle spindles keep track of muscle length (stretching), associated with gamma motor neurons that keep muscle spindles in their most sensitive state regardless if starting out stretched or contracted, golgi tendon organs respond to muscle tension (contracting muscle against some resistance) not stretching
tabulate the roman numeral/greek letter classification system for fibers of cutaneous nerves and muscle nerves
-Large-myelin [muscle spindles Ia, golgi tendon organs Ib]
-Medium-myelin [fine touch, muscles, joints II (AB)
-Small-myelin [pain, cool, touch delta]
-small-unmyelinated [pain, warmth, touch C]
-large-myelin [skeletal muscle alpha]
-medium-myelin [muscle spindles gamma]
-small-myelin [preganglionic autonomic]
-small-unmyelinated [postganglionic myelinated]
list the relationships between peripheral nerve fiber function, diameter, conduction velocity and degree of myelination
larger axons with more myelin = faster signal travels, smaller ones take care of pain, touch, temperature, larger take care of muscle stretch and tension and etc
describe the location of the conus medullaris, cauda aquina, the number of each type of cord segment, the position of enlargements and relative position of spinal nerves and vertebral segments
conus medullaris in an adult is at the L1-L2 position (surrounded by spinal nerves), cauda aquina is the group of spinal nerves surrounding the conus medullaris, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal, cervical enlargement located at C5-T1, lumbosacral enlargement from L2-S3
where do the following terminate in the dorsal horn of the spinal cord: small myelinated fibers, small unmymelinated fibers, large myelinated fibers
small myelinated and unmyelinated fibers enter in Lissauer's Tract, large myelinated fibers enter in the posterior funiculus
discuss the circuitry of the stretch reflex and the flexor (withdrawal) reflex
stretch reflex--primary afferent (muscle spindle Ia) synapses directly on motor neurons that innervate the muscle

flexor reflex--involves multiple muscles and multiple spinal levels, involves primary afferent, interneuron, and synapse on neuron which connects to muscle fibers
describe the arterial blood supply of the spinal cord. Indicate the area supplied by the anterior spinal artery
spinal cord blood from 3 arteries (2 anterior arteries fuse to form the anterior spinal artery), this goes on to supply anterior 2/3 of cord (includes spinothalamic tract and most/all of lateral corticospinal tract), 2 posterior arteries supply posterior columns, posterior horns, and part of lateral corticospinal tracts
describe the pathway by which information from the body about touch and limb position reaches consciousness
large diameter fibers (primary afferents) enter ipsilateral posterior funiculus, branches ascend to the medulla and synapse on second order neurons in posterior column nuclei, (fibers from below cervial enlargement travel in medial part (fasciculus gracilis) and end in nucleus gracilis, and those from cervical and upper thoracic travel ascend laterally (fasciculus cuneatus) and end laterally in nucleus cuneatus. All axons cross the midline and form bundle (medial lemniscus) which travels through brainstem to thalamus and from there to somatosensory cortex
describe the pathway by which information from the body about pain and temperature reaches consciousness
primary afferents of spinothalamic tract enter CNS and synapse immediately on ipsilateral second order neurons (via substantia gelatinosa interneuron), axons of second order neurons cross the midline, form spinothalamic tract and travel up to thalamus and from there to somatosensory cortex
describe the pathway by which voluntary movements of the trunk and limbs are mediated
corticospinal tract begins in motor cortex and descends through internal capsule and brainstem, fibers cross midline at pyramidal decussation (spinomedullary junction), synapse on lower motor neuron which leaves CNS and directly innervates muscle
compare and contrast the sites and consequences of lower motor neuron and upper motor neuron damage. Include an indication of the significance of Babinski's sign and a description of spinal shock
damage to lateral corticospinal tract causes ipsilateral spastic weakness, weakness of voluntary movement, increased tone, exaggerated reflexes, and Babinski's sign, if damage occurs above pyramidal decussation then contralateral side would be affected, spinal shock occurs post injury when most parts of cord below injury stop working
compare and contrast the sympathetic, parasympathetic, and enteric parts of the ANS
enteric--has its own afferent, efferents and interneurons rather than having projections directly from CNS

sympathetic--fight or flight, has preganglionic in spinal cord (use acetylcholine)(intermediolateral column), postganglionic close to spinal cord in sympathetic chain ganglia (use norepinephrine)

parasympathetic-- energy absorption and storage, preganglionic in brainstem and sacral spinal cord, postganglionic in ganglia near or in target organs (both use acetylcholine)
describe the physical substrates and neural circuitry underlying the storage mode and elimination mode of the bladder
storage mode maintained by sympathetic inputs, postganglionics promote relaxation of detrusor, urethtral pressure maintained by tonic contraction of external sphincter (innervated by LMN),urethra elasticity, bladder fills with little rise in pressure

elimination mode-- parasympathetics take over, destrusor contraction, pressure raises, urethral pressure falls (LMN are inhibited)
describe the neural pathways involved in normal micturition reflex
turns on elimination mode, collects information about status of bladder and social situation (is it an appropriate time to switch to elimination mode), spinal-brainstem reflex that can be consciously controlled
compare and contrast the effects on bladder function of damage to cauda equina, conus medullaris, midthoracic spinal cord, and cerebral hemispheres
cauda equina or conus medullaris damage-- bladder fills beyond normal size because cannot accurately detect pressure, fills until exceeds urethral pressure and overflow incontinence occurs (prone to UTIs)

midthoracic spinal cord-- bladder automatically tries to empty itselfo, external sphincter never gets signal to relax, pressure builds until overcomes sphincter and reflex incontinence results (high pressure sends urine back to kidneys...infection)

cerebral hemispheres- normal micturition reflex possible, but if other inputs missing then incontinence can result (either difficulty suppressing urination or diminished social awareness)
identify the dividing lines between the rostral and caudal medulla, pons, and midbrain
caudal medulla extends from pyramidal decussation to caudal end of 4th ventricle

rostral medulla extends from bottom of 4th ventricle to where the inferior cerebellar peduncle turns to enter the cerebellum

caudal pons extends from lateral recess of 4th ventricle to rostral edge of middle cerebellar peduncle

rostral pons extends from rostral edge of middle cerebellar peduncle to beginning of cerebral aqueduct

caudal midbrain extends from point of emergence of trochlear nerve to intercollicular groove

rostral midbrain extends from intercollicular groove to posterior commissure
describe the course of the medial lemniscus, spinothalamic tract, and corticospinal tract as they transverse the brainstem
spinothalamic tract always ventrolateral in tegmentum to thalamic relay

corticospinal tract always most ventral part of brainstem to thalamic relay

medial lemniscus (continuation of posterior column) starts out medially and then moves progressively closer to spinothalamic tract, adjacent to each other in midbrain
indicate the brainstem locations of the posterior column nuclei, inferior olivary nucleus, middle and superior cerebellar peduncles, inferior and superior colluculi, periaqueductal gray, red nucleus, substantia nigra, fourth ventricle, and cerebral aqued
posterior column nuclei- caudal medulla (posterior half of stem)

inferior olivary nucleus- rostral medulla ventrolateral

middle cerebellar peduncles- surround caudal pons laterally

superior cerebellar peduncles- rostral pons dorsal

inferior colliculi- caudal midbrain dorsal

superior colliculi- rostral midbrain dorsal

periaqueductal gray- rostral midbrain surrounding aqueduct

red nucleus- rostral midbrain, ventromedial

substantia nigra- rostral midbrain between medial lemniscus and corticospinal

fourth ventricle- rostral medulla, caudal pons, rostral pons (all dorsomedial)

cerebral aqueduct- rostral pons, caudal midbrain, rostral midbrain (all dorsomedial)
describe the location and major functions of the brainstem reticular formation
central core of brainstem, functions include control of movement through connections with spinal cord and cerebellum, transmission of pain information, autonomic reflex circuitry, and control of arousal and consciousness (regulation of sleep-wake cycles)
indicate the CNS locations of the diffusely projecting neurons that use each of the following neurotransmitters: acetylcholine, dopamine, norepinephrine, and serotonin
locus ceruleus extends through rostral pons and contains norepinephrine

raphe nuclei located at midline throughout RF, contains serotonin

substantia nigra (strip in between medial lemniscus and corticospinal in the rostral midbrain) contains dopamine

ventral tegmental area in rostral midbrain contain dopamine

base of cerebrum above optic chiasm in basal nucleus and septal nuclei contain acetylcholine
list the attachment points and the general functions of the cranial nerves I-XII (also indicate Ventral, Dorsal, Lateral)
CN-I (olfactory) attaches directly to olfactory bulb

CN-II (optic) proceed thru optic chiasm and tract

CN-III (oculomotor) V rostral midbrain [eye movement, pupil, lens]

CN-IV (trochlear) D pons midbrain junction [superior oblique, eye movement]

CN-V (Trigeminal)L midpons [facial sensation, chewing]

CN-VI (abducens) V pontomedullary junction [lateral eye movement]

CN-VII (facial) V/L pontomedullary junction [facial expression, posterior 2/3 taste]

CN-VIII (vestibulocochlear) V/L pontomedullary junction [hearing, equilibrium]

CN-IX (glossopharyngeal) L rostral medulla [anterior 1/3 taste, swallowing]

CN-X (Vagus) L rostral medulla [preganglionic sympathetic, speaking, swallowing, taste, other visceral]

CN-XI (Accessory) L caudal medulla, upper cervical spinal [head and shoulder movement]

CN-XII (Hypoglossal) V/L rostral medulla [tongue movement]
List the cranial nerves involved in taste and smell
Taste: CN-VII (facial), CN-IX (glossopharyngeal), CN-X (vagus)

Smell: CN-I (olfactory)
describe the sensory systems involved in the perception of flavor, and indicate the role of each
gustatory & olfactory combine to form perception of flavor, general chemical (stinging, coolness, spice, etc), and somatosensory (texture of food)
describe the anatomy of the receptor organs for taste and smell
tongue covered in bumps and folds (fungiform papillae, foliate papillae, vallate papillae) contain tastebuds. Each taste bud contains epithelial cells (taste receptor cells). Chemicals come in, receptor cells synapse on endings of facial, glossopharyngeal, or vagal nerve fibers. Taste receptor cells use several transduction methods (all result in depolarizing receptor potentials)

layer of olfactory receptor neurons in roof and wall of nasal cavity. Thin unmyelinated axons collect and form cranial nerve I, pass through cribriform plate of ethmoid bone to reach olfactory bulb. Produce depolarizing receptor potentials (increase frequency of action potentials). All use G-coupled protein transduction
compare and contrast the pathways taken by olfactory and taste information into the brainstem and cortex
taste information enters through taste buds, depolarizing receptor potential, fibers innervating taste buds have central processes that enter solitary tract, second order fibers convey info to gustatory cortex (insula) by relay in thalamus (uncrossed)

olfactory receptors group together, pass through cribriform, find olfactory bulb, projected to primary olfactory cortex (near uncus) without relay in thalamus, then projects to olfactory assoc. cortex
Differentiate between the bony and membranous labyrinth and the fluids that fill various parts of them
bony labyrinth--outer tube, continuous channel in temporal bone, contains bony cochlea (anterior), semicircular channels (posterior), vestibule in between, filled with perilymph (like CSF)

membranous labyrinth--continuous closed system, contains cochlear and semicircular canals, suspended within bony labyrinth, also vestibule (utricle and saccule), filled with endolymph (like intracellular fluid)
describe the mechanical arrangement of receptors and accessory structures in the semicircular ducts that determine the kind of stimuli they respond to
enlargement at one end = ampulla, contains crista which hair cells live on, gelantinous flap (cupula) forms diaphragm across ampulla, most sensitive to angular acceleration (like spinning, rolling, flipping), but maintained rotation has no impact (endolymph catches up)
describe the mechanical arrangement of receptors and accessory structures in the utricle that determine the kind of stimuli they respond to
contains macula (patch of hair cells), project stereocilia (pointing up) into otolithic membrane (crystals), respond to linear acceleration (forward, backward motion)
describe the mechanical arrangement of receptors and accessory structures in the saccule that determine the kind of stimuli they respond to
contains macula (patch of hair cells), project stereocilia (pointed sideways) into otolithic membrane (crystals), respond to linear acceleration (up and down motion)
name the principal routes through which the vestibular system can influence posture and eye movements. Indicate the origin and course of the vestibulospinal tracts
fibers travel bilaterally through RF near MLF and reach thalamic nucleus (several areas of vestibular cortex)

2 vestibulospinal tracts that help us to make postural adjustments in response to vestibular stimulation:
- medial vestibular nucleus projects a bilateral medial vestibulospinal tract to cervical spinal cord through MLF [coordinate head and eye movements]

- lateral vestibular nucleus sends uncrossed lateral vestibulospinal tract to all levels of cord [makes postural adjustments to antigravity muscles]
explain optokinetic nystagmus including directionality
effort to keep images on retina stable, caused by moving objects, eyes movement in direction opposite movement of object
explain rotary nystagmus including directionality
induced by rotation, eyes move in direction of rotation
explain postrotary nystagmus including directionality
occurs when rotation stops, eyes want to continue movement so direction is opposite of what direction rotation was in (brainstem is fooled into thinking the rotation has been reversed)
explain caloric nystagmus including directionality
same as rotationally induced nystagmus (induced by instilling cool or warm water into ear, causes endolymphic convection currents), direction is opposite of what ear water is added to
explain the relevance of the retina and neck proprioceptors to the integrated functioning of the vestibular system
semicircular canals can only signal maintained rotation for little while, vestibular nuclei receive vestibular, somatosensory, cerebellar and visual inputs to help know when to make postural adjustment and maintain balance
name the three tissue layers of the eye. describe the function of each. Indicate which of these layers give(s) rise to the cornea, ciliary body, and iris
1. cornea/sclera layer (outermost, thick, maintain eye shape)

2. uveal tract (middle layer, pigmented & vascular, consists of choroid lining, ciliary body, and iris)

3. retinal pigment epithelium/neural retina (double innermost layer)
describe the lens and its mechanical suspension within the eye, indicate the arrangement of muscles and the way in which they allow the shape of the lens to change
lens suspended from ciliary body by strands of connective tissue (zonular fibers) arranged like spokes around a wheel

at rest, lens is flattened out (radial tension by zonular fibers) focus is at distance

contraction of ciliary muscle relieves this radial tension and lens gets fatter under its own elasticity (focus on near objects)

oculomotor nerve-->ciliary ganglion-->short ciliary nerves-->ciliary muscle
describe the muscles and innervation that control the size of the pupil
pupillary sphincter constricts pupil

pupillary dilator (radially arranged) widen pupil

both arise from pigment epithelium layer of iris
define: anterior chamber
space between iris and cornea, filled with aqueous humor (which gets secreted into posterior chamber but pushed through pupil into anterior chamber)
define: posterior chamber
space behind the iris and in front of the lens (aqueous humor produced here by ciliary body)
define: ciliary body
produces aqueous humor, contains ciliary muscle (involved in changing shape of lens)
define: aqueous humor
fluid secreted by the ciliary body, fills anterior chamber of eye, helps eye maintain shape (through maintained fluid pressure)
(eye) define: vitreous humor
fluid in interior of eyeball (behind the lens), helps eye maintain shape
name the major cell types of the retina and their synaptic relationships
1. photoreceptors (rods & cones)[outer nuclei layer]
2. bipolar cells [inner nuclei layer]
3. horizontal cells [outer plexiform layer]
4. ganglion cells [ganglion cell layer]
5. amacrine cells [inner plexiform layer]

light shines into eye all way back to photoreceptors (rods and cones) then informationt travels forward again, they synapse on bipolar cells and horizontal cells (communicate between rods & cones for comparison of visual information), bipolar cells synapse on amacrine cells (like horizontal cells) and ganglion cells whose axons join together forming optic nerve
describe the distinguishing anatomical features of the fovea and optic disk (indicate the function of these features)
optic disk:
-located posteriorly inside eye, slightly medial to midline of eye
-contains no photoreceptors (corresponds to blind spot)
- ganglion cells converge here to form optic nerve and exit back of eye

-small retinal region in middle of pigmented layer (macula)
-packed with cones, no rods
-specialized for high spatial acuity and volor vision (only at moderate to high levels of illumination)
discuss transduction in vertebrate photoreceptors. Differentiate between rod and cone photoreceptors in terms of structure and function
photosensitive pigment catches photon, photoisomerization,activation of cGMP, closing cation channels, hyperpolarization

our photoreceptors are really dark receptors (receptor potentials are depolarizing events)

-function at lower level light than cones
-made up of stack of free-floating, flattened vesicles
-contain rhodopsin (photosensitive pigment)
-only work up to moderate moonlight, then get saturated

-work at moderate to high levels of illumination, for color vision
-made up of connected disks (not as many as cones)
-contain "cone pigments"
explain why multiple cone populations are required to encode color information
any cone cannot tell the wavelength of particular photon it has absorbed, has to compare against nearby cones to distinguish difference

cones are sensitive to relative differences not ultimate levels of illumination
compare and contrast the receptive fields of retinal photoreceptors, bipolar cells, and ganglion cells (include basic description of cell types and connections that account for receptive fields
photoreceptor receptive field: light falls on receptor or on part of outside world whose image lands on that receptor causes it to hyperpolarize, increasing size of stimulus has no effect

ganglion cells: two kinds = on-center cells and off-center cells

on-center cells: fires faster when light hits center of field rather than periphery (diffuse illumination = no response)

off-center cells: fire faster when more illumination falls on periphery of field rather than center (diffuse illumination = no response)

so, cells sensitive not to overall brightness but to contrasts between different parts of visual world (detect edges of things)

bipolar cells: also come in on-center & off-center varieties. Don't make action potentials (only receptor potentials) get information from photoreceptors (which hyperpolarize and release glutamate) exciting off-center bipolar cells and inhibiting on-center bipolar cells
describe the pathway leading from the retina to visual cortex
visual information travels from ganglion cell axons along retina, exit back of eye as optic nerve, half of visual field of each eye crosses at optic chiasm, and travels down respective optic tract and terminate in lateral geniculate nucleus (thalamic relay spot), these geniculate fibers travel through optic radiation (with divergence of superior field information in Meyer's Loop in temporal lobe before converging again in visual cortex) to visual cortex
describe the retinotopic map in the visual cortex
entire visual field mapper out with fovea information near occipital lobe, superior and inferior parts of field below and above calcarine sulcus and peripheral part most anterior
compare and contrast the receptive field properties of neurons in the retina, lateral geniculate nucleus, and visual cortex
retinal cell receptive fields:
-photoreceptors respond to light falling on them (light falling on spot on outside world they respond to)
-ganglion cells (on-center respond to light on center of field, off-center respond to light on periphery of field, no response to diffuse light)
-bipolar cells have on-center and off-center types too, respond to information received from photoreceptors

lateral geniculate nucleus receptive field:
-similar to ganglion cells, input from only one eye, center/surround antagonism, some care about color, some care about black-white contrast, project to visual cortex

visual cortex receptive fields:
-those concerned with contrast rather than color don't respond much to diffuse illumination, receptive fields NOT circular shaped and don't repond to small spots of light anywhere
-sensitive to stripes or edges with particular orientation
- those concerned with color have circular receptive fields (with center-surround properties)
-others pay attention to motion, or retinal disparities (for depth perception)
in general, what cortical areas are involved in further processing of information about form, color, location, and movement of visual stimuli
form & color: ventral parts of occipital and temporal lobes

location & movement: dorsal parts of occipital and parietal lobes
what structures and pathways influence pupil size
light shone in either eye should cause both pupils to constrict

-information about one retina distributed bilaterally to optic chiasm, reaches pretectal area which projects bilaterally to Edinger-Westphal nucleus (in oculomotor nucleus)

also projections from pupil size (dilation due to less light), to hypothalamus...involved in circadian rhythms
describe the major landmarks and the innervation of the external ear
auricle/pinna- skin covered cartilage flap with ridges and depressions (tunes sound waves for efficient transmission)

concha-depression in middle of auricle (leads sound into external auditory canal)

external auditory canal-neck of the funnel

innervation of auricle:
-trigeminal and upper cervical nerves are very important
-facial, vagus, and sometimes hypoglossal are also important
describe the path taken by a sound wave from the outer to the inner ear. (indicate role of outer ear, tympanic membrane, middle ear ossicles in transferring sound energy efficiently into the fluids of the inner ear)
1. outer ear fine tunes sound waves and channels them into external ear canal
2. sounds continue down ear canal and are conducted to tympanic membrane (ear drum) which causes it to vibrate
3. vibrations are transmitted to middle ear
4. (ossicles of middle ear) malleus is vibrated directly by tympanic membrane
5. malleus is articulated with incus and transmits vibrations to stapes (attached to oval window)
6. oval window and stapes transmit vibrations to inner ear
7. combination of the tympanic membrane and oval window 15X size differential changes low-pressure airborne vibrations into high-pressure fluid vibrations (inner ear)
name the muscles associated with the middle ear cavity, give their innervation, and explain their actions
stapedius & tensor tympani are middle ear muscles

stapedius innervated by CN-V (trigeminal), attaches to head of stapes, contraction stiffens ossicular chain and damps the oscillation.

tensor tympani innervated by CN-VII (facial), attaches to handle of malleus, when contracts pulls in on tympanic membrane and decreases transmission of vibration
list the components of the bony and membranous labyrinths, and describe the orientation of the bony labyrinth
bony labyrinth is outer tube (channel in temporal bone) filled with perilymph
-contains cochlea (which contains the organ of hearing) and semicircular canals
-meeting point of these two is the vestibule
-orientation: 3 planes (anterior, posterior, and horizontal)

membranous labyrinth is inner tube (within bony labyrinth) and is filled with endolymph
-contains cochlear duct and semicircular ducts and vestibule
-vestibule made up of utricle and saccule (related to vestibular function)
-is continuous closed system that communicates with itself but not with perilymph
describe the mechanical arragement of receptors and accessory structures in the cochlea that specialize it for responding to sound. Indicate the relative functions of inner and outer hair cells, and describe the mechanism of otoacoustic emissions
-cochlear duct is partition stretched across cochlear part of bony labyrinth
-has hole at apex (helicotrema) which allows perilymphatic space to communicate
-stapes pushes inward causes perilymph movement and cochlear duct deformation
-hair cells located in Organ of Corti are embedded in gelatinous membrane
-deformation of cochlear duct causes deflection of hair cells which opens or closes cation channels and causes depolarizing or hyperpolarizing receptor potential, causing release of NT onto CN-8 fibers and action potentials to CNS

populations of cochlear hair cells:

-inner hair cells (heavily innervated by 8th nerve), critically involved in conveying sound information to CNS

-outer hair cells (sparsely innervated), involved in amplifying local vibrations of basilar membrane

-portions of cochlear duct near oval window more sensitive to higher frequencies, portions nearer helicotrema more sensitive to lower frequencies

-push on oval window creates traveling wave up basilar membrane

-otoacoustic emissions involve direct control of outer hair cells of the cochlea via neurons that arise from the medial superior olivary complex
describe the central auditory pathway, indicating the principal nuclei and fiber bundles in the ascending and descending systems
1. cochlear nerve fibers end ipsilateral in cochlear nuclei (junction of pons & medulla)
2. cochlear nuclei project bilaterally in the brainstem (all levels rostral-each ear represented bilaterally)
3. auditory pathway rostrally includes superior olivary nucleus (crossing fibers reach it through trapezoid body), inferior colliculus (by way of lateral lemniscus), medial geniculate nucleus of the thalamus (by way of inferiour brachium), and auditory cortex (superior surface of temporal lobe)
describe functions of major components of the ascending auditory pathway
superior olivary nucleus important for sound localization
List the contents of the trigeminal nerve
motor root is motor nerve for chewing muscles and tensor tympani

sensory roots feed into reflexes, pathways to cerebellum, and pathways to thalamus

mesencephalic nuclei & tract
indicate the location within the brainstem of the nuclei associated with the trigeminal nerve
main sensory nucleus in pons (where trigeminal enters brainstem), merges with spinal nucleus of trigeminal

spinal nucleus starts in caudal pons and extends to cervical spinal cord

mesencephalic extends rostral from main sensory nucleus, reaches rostral midbrain
describe the central pathways by which information from the head about pain, touch, and temperature reach consciousness
1. pain and temp fibers enter pons, turn caudally traveling as spinal trigeminal tract

2. terminate in caudal medulla where second order neurons cross midline and join spinothalamic tract which projects to thalamus

1. touch & position fibers end in main sensory nucleus (midpons level)

2. second order neurons cross midline, join medial lemniscus which projects to thalamus
indicate the location within the brainstem and the function of the facial motor nucleus, and describe the course taken by facial nerve fibers after they leave this nucleus
facial motor nucleus located near spinothalamic tract in caudal pons

it is a collection of lower motor neurons for muscles of facial expression and stapedius

axons wrap around the abducens nucleus to form the interal genu of the facial nerve before leaving brainstem
indicate location within the brainstem of motor neurons for the larynx and pharynx, and the cranial nerves through which these motor neurons distribute their axons
motor neurons for larynx and pharynx located within the brainstem tegmentum near the spinothalamic tract (diffuse column known as nucleus abiguus), extends through medulla

most rostral sends axons through glossopharyngeal nerve
indicate the principal locations within the brainstem of preganglionic parasympathetic neurons, and the cranial nerves through which these neurons distributes their axons
preganglionic parasympathetic neurons in dorsal motor nucleus of the vagus or in the nucleus ambiguus (medulla) and project axons out through either vagus, or CN-IX,VII, or III
list the cranial nerves through which the visceral afferent information reaches the brainstem. Indicate where these afferents travel within the brainstem and where they terminate
visceral afferents reach brainstem through the facial nerve (enter in solitary tract and end in nucleus of solitary tract , somewhere between rostral medulla and caudal pons)

through glossopharyngeal nerve (enter in solitary tract, end caudally in nucleus of solitary tract)

through the vagus nerve (enter solitary tract and end in caudal parts of nucleus of solitary tract)
list the cranial nerves through which information from taste buds reaches the brainstem. Describe the route through which gustatory information reaches consciousness
anterior 2/3 of tongue reaches brainstem via facial nerve (enter solitary tract, synpase in nucleus of solitary tract onto second order neurons, relay in thalamus, info sent to taste cortex (insula)

posterior 1/3 of tongue enters solitary tract via glossopharyngeal nerve, end just below facial nerve afferents (nucleus of solitary tract), synapse on second order neurons, relay in thalamus, project to taste cortex (insula)
describe the neural circuitry involved in the jaw-jerk and blink reflexes
trigeminal motor and mesencephalic nuclei involved

Jaw jerk:
masseter stretch reflexes have cell bodies in mesencephalic nucleus, central processes synapse on masseter motor neurons (completing reflex arc)

eye blink:
spinal trigeminal nucleus is interneuron, project bilaterally to facial motor nucleus which projects to orbicularis oculi (causing blink)
compare and contrast the effects of damage to the trigeminal motor nucleus and damage to the corticobulbar fibers to that nucleus
damage to trigeminal motor nucleus: upper motor neuron damage will cause heightened jaw reflex

damage to corticobulbar chewing motor neurons:
weakness of contralateral masseter
compare and contrast the effects of damage to the facial motor nucleus or nerve and damage to the corticobulbar fibers to that nucleus
facial motor nucleus damage:
paralysis of entire ipsilateral face and ipsilateral stapedius is unable to contract (so things sound unnaturally loud in ipsilateral ear)

corticobulbar fiber damage:
weakness most prominent in contralateral lower facial muscles
compare and contrast the effects of damage to the nucleus ambiguus and damage to the corticobulbar fibers to that nucleus
nucleus ambiguus damage:

corticobulbar damage: often larynx and pharynx are fine because projections are bilateral
compare and contrast the effects of damage to the hypoglossal nucleus or nerve and damage to the corticobulbar fibers to that nucleus
hypoglossal nucleus damage:
ipsilateral weakness and atrophy of tongue (bilateral damage can cause difficulty speaking and eating)

corticobulbar damage:
contralateral tongue weakness
explain arrangment of sensory/motor, visceral/somatic fibers in brainstem and spinal cord
in spinal cord--
distal from sulcus limitans: concerned with somatic functions

proximal to sulcus limitans: concerned with visceral function

in brainstem--
(medial to lateral) somatic-motor, visceral-motor, visceral-sensory, somatic-sensory
what type of nerve are they and at what brainstem/spinal cord level do CNs 3-12 enter?
CN-III (oculomotor):
rostral midbrain

CN-IV (trochlear):
somatic motor
caudal midbrain

CN-V (trigeminal):
somatic motor/sensory

CN-VI (abducens):
somatic motor
caudal pons

CN-VII (facial):
visceral sensory/motor
caudal pons (medulla junction)

CN-VIII (vestibulocochlear):
special sensory
pons-medulla junction

CN-IX (glossopharyngeal):
visceral sensory
rostral medulla

CN-X (vagus):
branchial motor, visceral motor/sensory
mid medulla

CN-XI (accessory):
branchial motor
cervical spinal cord

CN-XII (hypoglossal):
somatic motor
mid medulla
list the three meningeal coverings of the cerebrum, cerebellum and brainstem and indicate in a general sense their histological structures
1. dura mater (outermost,thick, double layered though no distinct barrier)
2. arachnoid (middle, thin, attaches to dura and pia via arachnoid trebaculae connective tissues)
3. pia mater (innermost, thin, firmly attached to brain, follows all contours)
define real and potential spaces within and around the meningeal coverings and indicate the location and general configuration of the major dural septa
real spaces in/around brain:
subarachnoid (between arachnoid and pia) large spaces called cisterns

potential space in/around brain:
epidural space (between dura and cranium)
subdural space (between dura and arachnoid)

real space in/around spinal cord:
subarachnoid space
epidural space (between dura and vertebral periosteum)

potential space in/around spinal cord:
subdural space
describe the way in which the meninges function together to maintain the shape and position of the CNS
dura attached to inside of skull, arachnoid attached to dura and arachnoid trabeculae (connective tissue strips), arachnoid trabeculae strips attach on other end to pia which is firmly attached to every contour of brain/cord
what are the three most common sites of brain herniation and the likely clinical consequences of each
under falx cerebri: no serious neurological consequences

through tentorial notch: coma and death

through the foramen magnum: rapidly fatal
describe the typical mechanisms resulting in epidural and subdural hematoma
epidural: meningeal artery rupture

subdural: tear in vein where it enters venous sinus
compare and contrast the cranial and spinal meninges
cranial and spinal meninges very similar (dura, arachnoid, pia) but epidural space normal in spinal cord not in cranial meninges, arachnoid trabeculae in cranial are dentate ligaments in cord
describe the cellular composition of choroid plexus and indicate where choroid plexus is located within the ventricular system
forms between border of ventricular system and subarachnoid space

3 cell layers thick (capillary endothelium, pia, and ependymal lining)

found in both lateral ventricles (curves around), in interventricular foramen, roof of third ventricle, roof of part of fourth ventricle
describe the mechanism of production of CSF and indicate in a general sense its composition
ependyma are specialized as secretory epithelium (choroid epithelium)-makes CSF

solutes leak out of choroidal capillaries, cross pial layer, get stopped at or transported across choroid epithelium, resulting in CSF

CSF composition: isotonic like plasma but low in protein
describe the path of circulation of CSF, from its site of production to its site of absorption, describe the mechanism by which CSF is returned to the venous system
1. CSF produces in choroid epitheliuem (choroid plexus in ventricles and interventricular foramen)
2. moves through ventricular system
3. escapes into subarachnoid space through median and lateral apertures of 4th ventricle
4. reaches venous system by passing through arachnoid villi
define communicating and noncommunicating hydrocephalus, and give two examples of conditions causing each
obstruction outside ventricular system

blockage of flow through tentorial notch

obstruction within ventricular system (up to and including apertures of 4th ventricle)

occlusion of apertures of fourth ventricle
describe the general pattern of arterial circulation of the cerebral hemispheres, diencephalon, brainstem, and cerebellum, describe the circle of willis and its general functional significance
cerebral hemispheres:
internal carotid artery (two branches = posterior communicating artery, anterior choroidal artery), then divides into middle cerebral artery and anterior cerebral artery, all give rise to ganglionic arteries (tiny)

diencephalon: supplied by vertebral/basilar system, vertebral artery gives rise to anterior spinal artery, spinal artery, and PICA, then vertebral artery fuses into midline basilar artery, basilar artery splits into AICA and superior cerebellar artery

brainstem:supplied by vertebral/basilar system

cerebellum: supplied by vertebral/basilar system

circle of willis: confluence of anterior communicating artery, internal carotid artery, anterior cerebral artery, middle cerebral artery, posterior communicating artery, and posterior cerebral artery (important for maintaining blood flow despite blockage of one or more artery branches
discuss the three principal mechanisms that regulate global or regional blood flow to the brain
1. autoregulation
2. autonomic innervation of cerebral vessels
3. local changes in metabolite concentrations
describe the general pattern of venous return from the brain and its drainage via the venous sinuses
superficial veins-->superior saggital sinus-->confluence of sinuses-->tranverse sinus

deep veins-->great vein-->straight sinus-->confluence of sinuses-->transverse sinus
list the anatomical barriers interposed between the extracellular spaces around the CNS neurons and the general extracellular spaces of the body
1. blood-brain barrier
2. arachnoid barrier
3. choroid epithelium
describe the way in which the barriers (bt extracellular space around CNS neurons and general extracellular space of body) in combination isolate the extracellular spaces of the nervous system from the extracellular spaces outside the nervous system
network of tight junctions between capillary endothelium cells within the CNS

whatever gets out of capillaries has to diffuse through or get pumped across endothelial cells

astrocyte processes surrounding CNS important for formation and maintenance of blood-brain barrier

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