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Neuroscience Part II


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What type of vestibular receptor can be found in the semicircular canals?
What type of vestibular receptor can be found in the utricle and saccule?
What are the functions of the vestibular system?
1. maintaining equilibrium
2. postural maintenance
3. stabilization of eyes during head movement
What is the function of the cristae in the semicircular canals?
They are kinetic receptors that respond to angular accelerations and head rotations
What is the function of the maculae in the utricle and saccule?
They are static receptors that respond to linear accelerations
What occurs when the cilia is bent in the direction of the kinocilium? Away from the knocilium?
What happens when a cilium is bent perpendicularly to the kinocilium?
What determines the magnitude of the response of the hair cells?
The angle at which is it bent
Where are the maculae horizontal? Where are they vertical?
The utricles have horizontal maculae.
The saccules have vertical maculae.
What causes the hair cells to tilt?
The otolithic membrane slides due to gravity
What pair compliments the left horizontal semicircular canal?
The right horizontal semicircular canal
What compliments the left posterior semicircular canal?
The right superior semicircular canal
What compliments the left superior semicircular canal?
The right posterior semicircular canal
How is the direction of rotation signaled?
Increase in firing of one semicircular canal hair cells and decrease in firing of its complimentary pair
Describe the path of fibers arising from the semicircular canals, utricle and saccule.
Vestibular nucleus -->
Either spinal cord, cerebellum, or oculomotor nuclei
What is the function of the lateral vestibulospinal tract?
Excites motor neurons that control antigravity muscles of limbs and trunk and contributes to posture
What is the function of the medial vestibulospinal tract?
Coordinates visual info from medial longitudinal fasciculus to contribute to head and neck reflexes
Describe the vestibular projections to the oculomotor nuclei.
medial/superior vestibular nuclei -->
projects bilaterally through MLF -->
oculomotor nuclei of CN III, IV, and VI
What happens when you turn your head to the left?
Stimulates left horizontal semicircular canal -->
Excites left VN -->
Crosses to excite right CN VI nucleus -->
innervates right lateral rectus, and cross to excite oculomotor nucleus on left side -->
innervation of left medial rectus

Left horizontal semicircular anal stimulates inhibitory neurons in VN -->
excite left abducens nucleus through MLF -->
project to right oculomotor nucleus -->
innervates right lateral rectus

Inhibitory neurons from left VN inhibits left abducens nucleus -->
left lateral rectus does not contract

Also inhibits the right horizontal semicircular canal
Describe the connections between the vestibular nucleus and the cerebellum.
Flocculus, nodulus, vermis and fastigial nucleus
What are the two different projections from the fastigial nucleus?
Ipsilateral juxtarestiform body
Contralateral uncinate fasciculus
How does the eye focus near objects?
Contraction of ciliary muscle relieves tension on lens, causing it to assume a nearly-spherical shape
How does the eye focus distant objects?
Ciliary muscle relaxes, exerting tension on the lens and pulling it flat
What are the two different types of photoreceptors?
Rods and Cones
Where are rods and cones mostly localized?
Cones in the fovea
Rods in the periphery
What is the name of the photopigment molecule in rods and cones?
What parts make up rhodopsin?
Opin + chromophore (11-cis-retinal)
What does ligt do to rhodopsin?
Light isomerizes 11-cis-retinal to the all-trans configuration, which detaches from opsin.
What does it mean for rhodopsin to be bleached?
11-cis-retinal is changed to all-trans configuration, rendering it incapable of absorbing light
Why is the membrane potential of photoreceptors significantly less negative than that of a typical neuron in the dark?
In addition to the usual K-selective leakage channels, there are also non-selective cationic channels open in the resting state
What is the resting membrane potential of a photoreceptor and what causes it?
-35 mV, created by the tug of war between leakage channels and non-selective cationic channels
What creates the dark current in photoreceptors?
Na+ and Ca2+ enter the outer segment while K+ ions leave the inner segment
What two pumps are involved in establishment of the dark current?
Na-K ATPase
Na-Ca exchnger
What chemical process happens when light contacts a photoreceptor?
Cationic channels close, and influx of Na and Ca ceases. Vm hyperpolarizes towards Ek. This hyperpolarization terminates the release of glutamate by closing Ca channels.
What are the biochemical steps that photoreceptors are involved in?
Rhodopsin activated -->
Stimulates G protein -->
Activates PDE -->
Hydrolyzes cGMP -->
Channels close due to decreased levels
What is light adaptation?
Each receptor can adjust its sensitivity to light due to changes in intracellular Ca concentration
Where does input from photoreceptors converge?
On bipolar cells--converges in periphery while is one-to-one at the fovea
Why is the fovea a region of high visual acuity?
Because of the one-to-one ratio of cones to midget bipolars, a type of bipolar cell
What are the two types of bipolar cells? What is the difference between them?
H bipolars hyperpolarize when the photoreceptors that directly connect them are illuminated
D bipolars depolarize when the photoreceptors that drive them are stimulated by light
What neurotransmitter do bipolar cells respond to?
What is the difference between the glutamate receptors of H bipolars and D bipolars?
H = ionotropic (receptor = ion channel)
D = metabotropic (not channels themselves)
Do H and D bipolar cells generate action potentials?
No, because their electrical signal is sufficient
What cells do bipolar cells synapse on?
Retinal ganglion cells
Do retinal ganglion cells generate action potentials?
Where do retinal ganglion cells project to?
Axons give rise to the optic nerve which projects to the lateral geniculate nucleus of the thalamus
What do you call the retinal ganglion cells connected to the H and D bipolar cells?
H = off-ganglion cells
D = on-ganglion cells
What cells occupy the plane between photoreceptors and bipolar cells? What stimulates them and what do they do?
Horizontal cells are stimulated by glutamate and release GABA to inhibit other neurons in the area once it is stimulated
What is the purpose of lateral inhibition?
To enhance contrast
What creates lateral inhibition?
An excited photoreceptor excites a horizontal cell, which inhibits neighboring photoreceptors
What are amacrine cells and what is their function?
Another lateral communication cell that connects retinal ganglion cells--involved in sharpening the detection of time-dependent visual clues, such as motion
How do we distinguish between different colors?
There are three different types of cones--red, blue, and green
What is the name of the photopigment involved in circadian rhythms? Where do its axons project?
Axons project to the suprachiasmatic nucleus
What type of information is contained in the fibers of the optic tract?
Information from the contralateral visual field, but has fibers from BOTH eyes
What are the three places where fibers of the optic tract drop off on their way to the lateral geniculate nucleus of the thalamus?
Suprachiasmatic nucleus of hypothalamus for circadian rhythms
Pretectum to bilateral Edinger-Westphal nucleus for pupillary reflex control
Superior colliculus for orienting head and eyes with visual information
How are the six layers of the lateral geniculate nucleus divided?
Magnocellular = 1,2
Parvocellular = 3,4,5,6
Contralateral = 1,4,6
Ipsilateral = 2,3,5
What is the difference between magnocellular and parvocellular layers of the LGN?
Magnocellular is for rapidly changing/moving stimuli
Parvocellular is for high acuity/color
What is the name of the main area that the ateral geniculate nucleus projects to?
Striate cortex
aka V1, primary visual cortex
Where does visual information project to from the primary visual cortex?
V2, V3, V4, V5, and extrastriate visual areas
What is the organization of the LGN? Of the striate cortex?
LGN = spot detector
Striate Cortex = bar/edge detector
Where is the first place that information from both eyes is brought together?
Striate cortex (primary visual cortex)
What is meant by the "receptive field axis" of the primary visual cortex?
The orientation of the bar or edge representing the best stimulus for a cell
What is the difference between simple and complex cells in the primary visual cortex?
Simple = respond to edge/bar
Complex = respond to appropriately oriented stimulus, light or dark bar situated anywhere, may move
What is the difference in angles preferred between orientation columns? How many columns are required for all orientations?
10 degrees, therefore there are 18 columns
What is an ocular-dominance column?
Cells with a preference for input from one eye or the other
What is a hypercolumn?
A set of orientation columns and ocular-dominance columns
Where is the primary visual cortex located?
In the occipital pole and banks and depths of the calcarine sulcus on the medial surface of the brain
What are some other names for the primary visual cortex?
Striate cortex
Area 17
What are the inputs to the primary visual cortex?
Lateral geniculate nucleus in thalamus
Primary visual cortex of opposite hemisphere
Feedback connections from visual association areas of cortex
What are the outputs of the primary visual cortex?
LGN and other areas of thalamus
Superior colliculus and other areas of brainstem
Other hemisphere
Extrastriate visual areas
What nucleus in the thalamus can project directly to the extrastriate visual areas?
Pulvinar nucleus
Cortical visual receptive fields are in the contralateral visual space except:
-Spillover along vertical meridian
-Callosal connections
Describe the path and function of the dorsal stream of visual processing.
V1-V2-MT (stays in dorsal part of temporal love, headed for parietal --> frontal)

The dorsal stream processes motion ("Where")
Describe the path and function of the ventral stream of visual processing.
V1-V2-V4 (ventrally down temporal lobe)

The ventral stream processes form ("What")
What are the symptoms of lesions of V1?
Scotoma - blind spot in visual field; localized loss of ability to perceive any aspect of a visual stimulus located in a topographically corresponding part of the visual field
What symptoms are caused by lesions in V4?
Achromatopsia - disturbed color processing
What symptoms are caused by a lesion in the fusiform face area (FFA)?
Prosopagnosia - inability to recognize faces
What symptoms do lesions in the inferotemporal cortex (IT) cause?
Difficulty in object recognition and salience
What symptoms are caused by lesions in V5?
Lesions in V5 disturb motion sensitivity
What are the symptoms of lesions of the parietal lobe?
Visuospatial neglect - one can see an object if pointed out only
What causes monocular visual loss?
Disease in one eye or one optic nerve
What causes visual field loss?
Lesion caudal to the optic chiasm
What symptoms are caused by lesions of the optic nerve?
Decrease or loss of vision in one eye. When the patient covers the bad eye, vision seems fine.
What is the most common cause of lesions of the optic chiasm?
Pituitary tumors
What is the defect caused by lesions of the optic chiasm?
Bitemporal hemianopsia - loss of vision in the temporal visual field (which is conveyed by fibers coming from the nasal area)
What might cause binasal hemianopsia?
A lesion of both lateral aspects of the optic chiasm by tumor or infection
What would be the result of a lesion of the lateral geniculate body?
Homonymous hemianopsia - loss of an entire visual field
What is the most common cause of a lesion of the optic radiation?
Stroke in the distribution of the middle cerebral artery
What causes contralateral inferior quadrantanopsia?
A stroke involving only the upper division of the middle cerebral artery, damaging only the upper fibers of the optic radiation in the parietal lobe
What causes contralateral, upper quadrantanopsia?
A stroke involving the lower division of the middle cerebral artery and damage to lower fibers of optic radiation
What is the result of a lesion of the occipital cortex?
Homonymous hemianopsia
What is Anton's syndrome?
A rare syndrome when a patient will deny or be unaware of blindness
What causees Anton's syndrome?
Bilateral occipital lobe infarction
What area receives information from the motor cortex and discharges it into the brainstem?
Basal ganglia
Describe red muscle.
Smaller fibers
Rich vascular supply
Little glycogen
High ATPase activity
Many mitochondria
Slower contraction speed
Describe white muscle.
Fight or Flight
Largest fibers
Few mitochondria
Meager blood supply
Large amounts of glycogen
Fastest contraction speed
In what order are motor units activated? (Describe the size principle)
The order is determined by the sie of their motor neurons -- smaller fibers are active most of the time, and larger fibers are activated only when maximal effort is demanded
Describe the arrangement of the muscle spindle with regard to muscle fiber. How does this correlate with its function?
A muscle spindle is arranged parallel to the muscle fiber, therefore it is ideally suited to measure muscle length.
Describe the arrangement of the Golgi tendon organ with regard to muscle fiber. How does this correlate with its function?
The golgi tendon organ is embedded in the tendon of a muscle, oriented in series with the muscle fibers. This makes it ideally suited to measure muscle tension.
What is a muscle spindle composed of?
Intrafusal fibers surrounded by a connective tissue capsule -- two types of fibers are nuclear bag fibers and nuclear chain fibers.
Describe the two types of innervation of the muscle spindle.
Ia afferent: fiber ends in a spiral sensory termination around both nuclear bag and nuclear chain fibers, cell body is in DRG; contacts spinal interneurons or alpha motor neurons

Gamma/Fusimotor nerve fibers: innervate polar contractile ends of the muscle spindle
What is compensatory loading?
Information about muscle length is always transmitted to the CNS regardless of the activity of the muscle. This is due to contraction at the polar ends of the muscle spindle, causing the spindle to become shorter.
What are two methods by which voluntary movement might be initiated?
Direct activation of alpha motor neurons by descending output from the motor cortex.

Indirect activation of alpha motor neurons from the gamma reflex loop (activation of gamma motor neurons in spinal cord --> stretch of muscle spindle --> activation of Ia afferents --> reflex activation of alpha motor neurons)
What happens when a Golgi tendon organ is activated?
Activates Ib afferent fibers -->
Activates inhibitory interneuron -->
Inhibits alpha motor neuron connected to the same muscle -->
Relaxation of muscle from which Ib discharge arises
Describe the efferent projections from the motor cortex that are responsible for facial movements.
-To interneurons of lateral reticular formation which lead to cranial motor nuclei
-To motor neurons of some cranial motor nuclei (motor trigeminla, hypoglossal, nucleus ambiguous, facial)
Describe the afferent inputs to the primary motor cortex (area 4).
-Somatosensory cortex of postcentral gyrus
-Premotor cortex (area 6) w/ info from auditory, ss, visual, multimodal assoc. areas
-Contralateral motor cortex
-VL nucleus of thalamus w/ info from cerebellum, basal ganglia, and motor cortex itself
List the four major brainstem areas involved in the brainstem motor system.
-Superior colliculus (tectospinal tract)
-Vestibular complex (vestibulospinal tracts)
-Medial reticular formation (reticulospinal tract)
-Red nucleus (rubrospinal tract)
What are phasic movements?
simple reflexes, autonomic movements such as breathing, heart beat, etc
What is the difference between lesions of the pyramidal and extrapyramidal motor systems?
Pyramidal = loss of movement
Extrapyramidal = excessive, uncontrolled movement
What are the symptoms of pyramidal syndrome?
Impaired movement of limbs
What is the term for neurons excited sufficiently to produce APs? Those who do not reach threshold?
Firing zone
Subliminal fringe
What is facilitation?
Overlapping of subliminal fringes which results in a stimulus much larger than the algebraic sum of the two
What is occlusion?
Overlap of firing zones, resulting in an AP that is smaller than the sum of the two smaller APs
Which types of muscles are involved in antigravity movements? Withdrawal reflex?
What is reciprocal innervation?
Mutual inhibition of antagonist and protagonist muscle groups to produce smooth movements
What is the function of the cerebellum?
Monitors voluntary motor output and receives sensory feedback to adjust ongoing activity --> produces coordination
What are the three divisions of the cerebellum and what are they composed of?
Archicerebellum = Flocculo-nodular node
Paleocerebellum = anterior lobe + vermis
Neocerebellum = posterior lobe hemispheres
What is the function of the archicerebellum?
Maintaining equilibrium and proper adjustment of anti-gravity muscles during movement
What is the function of the paleocerebellum?
Postural reflexes
What is the function of the neocerebellum?
Voluntary movement--smoothly fine movement
Can cerebellar lesions produce paralysis?
Describe the cell layers of the cerebellar cortex.
-Deepest = Granule cell layer -excitatory to molecular layer as parallel fibers
-Purkinje cell layer -principle projections
-Molecular layer -inhibitory; stellate cells, basket cells
What are the two types of afferent fibers to the cerebellar cortex?
-Climbing fibers from inferior olive; excitatory on Purkinje cells
-Mossy fibers; excitatory on Granule cells --> parallel fibers --> purkinje cells
List the deep nuclei of the cerebellum, from medial to lateral.
Fastigial nucleus
Globose and Emboliform
What is the corollary motor discharge?
Input from motor regions to the cerebellum telling it of its "intention to move"
What is the sole source of all climbing fibers to the cerebellum?
The inferior olive
How does MRI work?
Magnetic field aligns protons in tissue. Then radio frequency pulses are sent to disturb the alignment, and when the pulse stops, the protons realign and emit the frequency that they absorbed.
What is the difference between T1 and T2 MRIs?
T1 = white matter is white, gray matter is gray, CSF/bone/blood/air is black

T2 = white matter/bone/blood/air are black, CSF is white, gray matter is gray
How does a CT scan work?
x-rays are absorbed in different tissues to different degrees and the unabsorbed x-rays are detected and measured by external detectors
What scan is useful for studying the regional metabolic functions of the brain?
PET scan
What is the fusimotor reflex?
Keeps the muscle taut.
What are 4 charateristics of the fusimotor reflex?
-Exhibits local sign (i.e. potentiates activity of muscle in carrying out its normal activity)
-Reflexes are polysynaptic
-Well activated by cutaneous afferents, but poorly activated by muscle proprioceptors
-Gamma motor neurons which mediate these reflexes are small and tend to be tonically active
What determines whether a muscle spindle will be more sensitive to the extent of stretch or the rate at which it changes?
Whether Gamma I or Gamma II fibers are activated
What are the motor functions of the brainstem?
Pusture, muscle tone, equilibrium reactions and righting reflexes
What formation regulates most of the brainstem motor functions?
Reticular formation
What causes decerebate rigidity?
Loss of descending inpus to the two zones of the reticular formation: facilitatory reticular formation is allowed to run unchecked and the input necessary to generate activity in the inhibitory reticular formation has been eliminated, leading to overactivity of the extensors.
What are the two ways that neural activity at the spinal cord level can be modulated?
-direct excitatory activation by neurons from higher centers
-fusimotor activation of muscle spindle
What are the three groups of receptors to help us to maintain equilibrium?
-labyrinthine receptrs in inner ear
-visual receptors in eye
-somatic proprioceptors
Explain the consequences of the following CNS transections:
-b/t cns and spinal cord
-b/t colliculi
-cerebral cortex
-Spinal animal: paralysis, loss of sensation, spinal shock
-Bulbospinal: rigid standing, will fall over if bumped
-Decerebate: rigidity
-Mesencephalic: can walk, run etc, but has trouble avoiding objects
-Decorticate: loses visual righting reflex, loss of previously learned behavior
What is the placing reaction?
Motor cortex sends info to alpha and gamma motor neurons which cause movement, and sensory stimulation through sensory cortex communicates with motor cortex to reinforce this action
What portions of the brain make up the basal ganglia?
Globus palidus
What are the cardinal symptoms of extrapyramidal motor syndrome?
-changes in muscle tone/rigidty
Can damage to basal ganglia cause paralysis?
What is the function of the basal ganglia?
Modulation of activity of cortical motor output
Damage to what structure causes pyramidal syndrome?
Damage to motor cortex
What is the major input and output of the basal ganglia? What is the NT used?
Input = cerebral cortex
Ouput = Motor cortex
What sends fibers into the striatum?
Telencephalic cortex

Caudate = prefrontal, temporal, parietal association areas
Putamen = motor, somatosensory cortices
Where do efferents from the striatum (caudate and putamen) project?
Inhibitory efferents to external and internal segments of globus pallidus
What provides the main input to the globus pallidus?
The striatum (caudate and putamen)
What is the difference in the projections of the internal and external segment of the globus pallidus?
Internal = VL/VA nuclei of thalamus
External = subthalamic nucleus
What is the difference between the two segments of the globus pallidus with regards to dopamine receptors?
Internal = influenced by action on D1 receptors

External = influenced by action on D2 receptors
Which portion of the substantia nigra is considered a part of the pallidum?
Pars reticulata
Describe the input/output of the substantia nigra pars reticulata.
Input = inhibitory from striatum
Output = inhibitory projections to thalamus
Describe the input/output of the substantia nigra's pars compacta.
Receive input/sends output to striatum
What is the difference between D1 and D2 receptors?
D1 = excitatory
D2 = inhibitory
What effect to dopaminergic projections from the substantia nigra have on the striatum?
Depends on the Dopamine receptor...
1.Excite D1 R: inhibits GPi, releases inhib from Va/VL thalamus, stimulates cortex
2.Inhibits D2 R: releases excitation from subthalamic nucleus, releases excitation from Va/VL, no motor cortex excitation
What are the inputs/outputs of the subthalamic nucleus.
Input = inhibitory from external GP, ecitatory from internal GP

Output = excitatory to internal GP
What causes hemiballismus (flinging of contralateral extremity)?
Unilateral destruction of subthalamic nucleus
What causes Parkinsonism symptoms?
Damage to dopaminergic neurons of substantia nigra pars compacta
What are the three major symptoms of Parkinson's Disease?
Resting tremor
What are some symptoms of dopamine excess during Parkinson's treatment?
Explain how MPTP might offer one possible cause of Parkinson's Disease.
MAO B converts MPTP to MPP+
MPP+ irreversibly inhibits NADH/ComplexI in mitochondria by producing free radicals
This reduces ATP production
List medical treaments of PD.
Anticholinergics (lower output of striatum)
L-dopa (increase dopamine prod.)
Dopa agonists
MAO-B / COMT inhibitors (slow breakdown of dopamine)
What are some possible surgical treatments of PD?
-Bilateral stimulation of subthalamic nuclei
-Pallidotomy (lesion of GPi)
-Thalamotomy (lesion in nuclei)
-Thalamic stimulation
What does a pallidotomy do in pts with PD?
Reduces the number of abnormally firing cells of GPi. Reduces tremor. Surprisingly, decreases hypokinesia and dyskinesia.
Where is allocortex found? What makes it different from neocortex?
The allocortex, which has fewer than six layers of cells, is located in the hippocampus, subiculum, entorhinal area, etc.
Where are pyramidal cells found in the cerebral cortex?
Anywhere outside layer 4, which is where thalamic input is. Mostly layers 2,3,5,6
What are spiny stellate cells?
Cells found in layer 4 of some cortices, like pyramidal cells but lacking apical dendrites; excitatory
What are nonpyramidal cells?
Inhibitory cells (NT = GABA) of cerebral cortices
Describe the six layers of neocortex.
1: molecular layer; apical tufts of pyramidal cells

2/3: pyramidal cells

4: thalamic input; small spiny stellate or pyramidal cels

5: large pyramidal cells

6: pyramidal cells (upper), horizontal cells (lower)
What are the specific terms for the primary sensory area cortex and motor cortex?
Primary sensory = granular cortex

Motor = agranular cortex
What are Betz cells?
Extremely large layer V pyramidal cells in the motor cortex of the precentral gyrus
What are vertical bundles in the cortex made of? What about horizontal bands?
Vertical = cortical efferents

Horizontal = myelinated communications between cortical areas
What do areas 1,2, and 3 correspond to?
Somatosensory area
What does area 4 correspond to?
Motor cortex
What does area 17 correspond to?
Primary visual cortex
What do areas 41 and 42 correspond to?
Auditory cortex
What are the three major inputs to the cerebral cortex?
-thalamic inputs = excitatory; layer 4
-other cortical areas(association input) = terminates in layer 3
-callosal input = layer 3; not for hands or visual area
What are the major output pathways of the cerebral cortex?
-layer 3 to other areas of cortex
-layer 5 to brainstem and spnial cord
-layer 6 to thalamus
What is considered the roof of the third ventricle?
The epithalamus
Which thalamic nuclei are involved with motor functions?
What thalamic nucleus is involved in visual processing?
Lateral geniculate nucleus
Which thalamic nucleus is involved with hearing?
Medial geniculate nucleus
What information do anterior limb fibers of the internal capsule convey?
connect anterior nucleus and cingulate gyrus, dorsomedial nucleus and prefrontal cortex, and frontal lobe with pontine nuclei
What information is conveyed by genu fibers of the internal capsule?
connects VA/VL with motor and premotor cortex
What information is conveyed by the posterior limb of the internal capsule?
connects VA/VL to motor and premotor cortex, corticospinal/bulbar tracts, somatosensory projections from VPL/VPM to postcentral gyrus
What information is conveyed by the retrolenticular limb of the internal capsule?
association cortex with pulvinar and LP nuclei, optic radiation from LGN to calcarine sulcus, corticopontine fibers
What information is conveyed by the sublenticular limb of the internal capsule?
connects optic radiation of superior visual field, auditory radiation from MGB to superior temporal gyrus
What cells develop into pyramidal cells in the cerebral cortex?
Neuroblasts divide and differentiate into pyramidal neurons and the glia of the cortex
What happens when the plane of cleavage of neuroblasts is vertical? Horizontal?
Vertical = both cells remain as neuroblasts

Horizontal = upper will differentiate into neuron or glial cell, lower remains neuroblast
Describe the steps in neuroblast differentiation.
-neuroblasts differentiate into radial glia
-newer differentiating cells climb up radial glia to cortical plate
-cortical plate becomes separated from radial glia by intermediate zone
-layer 6 forms first, 5,4,3,2,1 after
Describe the development of non-pyramidal cells of the cerebral cortex.
Migrate tangentially for long distances through the intermediate zone, before travling up through the cortical plate to take their places as interneurons in cerebral cortex
What do astrocytes develop from?
Radial glia, the first differentiating cell of the neuroblasts
How do the different cortical areas develop? (Two theories)
Protomap theory : map is programmed into cellswhile they are in neuroepithelium

Protocortex : become specified in terms of function and connections as a consequence of other factors, such as thalamic input
How does an EEG work?
Records only signals that reflect the synchronous activity of large populations of nerve cells--other activity will tend to cancel out
Arrange the wave types (alpha, beta, delta, theta) in order of increasing frequency.
Delta- 0.5-4 Hz
Theta- 4-8 Hz
Alpha- 8-13 Hz
Beta- 13+ Hz
What is alpha wave suppression an indicator of?
What are the functions of the hypothalamus?
Homeostasis of BP, electrolytes, body temp, arousal and stress responses
Describe the hypothalamic connections with regard to endocrine control.
-Paraventricular nucleus and supraoptic nucleus connect to posterior pituitary
-Arcuate nucleus connects to anterior pituitary
Describe the hypothalamic connections with regards to autonomic visceromotor control.
Dorsal longitudinal fasciculus (DLF) travels to all brainstem ANS nuclei (ex. dorsal motor nucleus of the vagus) and joins the reticulospinal tract to reach sympathetic and parasypathetic areas of spine
Describe the hypothalamic connections with regard to species-preserving behavior.
-Medial forebrain bundle (MFB) from VTA, Mammillary peduncle from PAG = afferents
-MFB, Mammillotegmental tract; both project to reticular formations = efferents
What are the afferents to the hypothalamus from the limbic system/prefrontal cortex?
-Medial forebrain bundle from basal forebrain nuclei
-Fornix from hippocampus
-Stria terminalis from amygdala
-Ventral amygdalofugal pathway (VAF)
What are the efferent projections from the hypothalamus to the limbic system?
-Medial forebrain bundle
-Mammillothalamic tract to anterior nucleus of thalamus
-Diffuse periventricular fibers
What is the hypothesis about how the limbic system developed?
The hypothesis is that the limbic system differentiated from the olfactory system
What are the two regions of allocortex that have only three cell layers?
Hippocampal formation
Primary olfactory cortex
What are the three cholinergic nuclei of the basal forebrain?
Septal nuclei
Diagonal band nuclei
Nucleus basalis
Where do primary olfactory axons project to?
Primary olfactory axons -->
Amygdala and entorhinal cortex -->
Hippocampal formation
Where is the largest multimodal association area found? Where are smaller areas found?
The largest area is in the prefrontal cortex, however there are smaller areas in the posterior parietal lobe and posterior and entral temporal lobe.
What is the function of the amygdala?
The amygdala is the interpreter of stimuli that are directly relevant to basic biological needs and their related species preserving behaviors.
What type of behavior does large amygdala lesions cause?
Previously aggressive animals become placid, misdirected sexuality, agnosia (lack of knowledge of the meaning of diff. stimuli)
Describe the input of the amygdala.
Input =
Sensory association cx (vision, audition, somatic sensory)
Primary olfactory cx
Cingulate cortex (pain)
Basal forebrain via limbic system (reward/punishment)
Hypothalamus (hunger, third, sex drive,etc)
Describe the output of the amygdala.
-Sensory association cortices
-Cingulate and frontal cortices
-Entorhinal cortex
-Basal forebrain
How does the amygdala reach the hypothalamus? (Name two paths)
-Stria terminalis in wall of lateral ventricle
-Ventral amygdalofugal pathway through basal forebrain
What are the major hypotheses with regard to the function of sleep?
-Restoration and recovery
-Energy conservation
-Promotion of foraging and predator avoidance
-Modulation of memory formation or storage
What are the characteristics of the 5 stages of sleep?
1 = decreased alpha activity
low voltage EEG
slow rolling eye movements
moderate/low EMG

2 = sleep spindles
eye movements rare

3 = slow delta waves appear

4 = dominated by delta waves

REM = rapid eye movements
no muscle movement
brain activity similar to when awake
What does the ability to fall asleep and maintain sleep depend on?
Duration of prior wakefullness and circadian time when sleep episode occurs
What area of the brain regulates circadian rhythms?
Suprachiasmatic nucleus of hypothalamus
What neurotransmitter is involved in REM sleep generation?
Name some wakefullness promoting factors.
Substance P
Corticotropin releasing factor
Thyrotropin releasing factor
Vasoactive intestinal protein
Name some sleep promoting factors.
Prostaglandin D2
Describe cell death by necrosis.
Decreased O2 -->
Interrupts ATP dependent processes, like Na/K pump and glutamate-uptake transporters-->
Cells cannot regulate intracellular environment, build up of ions -->
Influx of water -->
Cell swells and bursts
Describe cell death by apoptosis.
Programmed cell death--activate cascade of degradative enzymes that disassemble cell. A neighboring cell engulfs the debris.
What is Wallerian degeneration?
Schwann cells --> scavenger like cells + monocytes --> macrophages eliminate myelin and axonal fragments from proximal to distal axon in order to make space for new axons to grow. Leaves connective tissue to guide regeneration.
Where does a glial scar form?
Wallerian degeneration of axons in CNS
What is a neurotrophic factor? Name some examples.
Induces neural growth of axons.

Ex. Neural growth factor, brain derived neural growth factor, neurotrophin 3,4,5
What do neurotrophic factors interact with?
Tyrosine-kinase receptors
What is a neurotropic factor? Name some examples.
Guides axons to correct target.

Ex. semaphorin, neurophilin, CAM
What are some ways through which neural plasticity can occur?
-modulation of synaptic strength
-use of other neuronal circuits
-generation of new networks
-axonal sprouting
What receptor are long term depression and potentiation dependent on?
glutamate NMDA receptor
What are the two major efferent pathways of the hippocampus?
-Subcortical: leaves through fornix to basal forebrain, anterior nucleus of thalamus, mammillary bodies
-Cortical: project directly through white matter of temporal lobe to multimodal areas
What afferents does the hippocampus receive?
-multimodal sensory input through entorhinal cortex
-olfactory input via entorhinal cortex
-viscerosensory input from amygdala
-cingulate cortex input with pain/emotional reward info
Where do efferents from the hippocampus project to?
-basal forebrain
-hypothalamus and anterior thalamus via fornix
-entorhinal cortex
-multimodal areas in parahippocampal cortex and cingulate cortex
What is the hippocampal formation important for?
Putting new memories into storage
What is kindling?
When seizure activity becomes "learned", i.e. the theshold becomes lower
Describe the afferent inputs to the cingulate gyrus.
-hippocampus via anterior thalamic nuclei
-hypothalamus via mediodorsal thalamic nuclei
-amygdala directly and via medial dorsal nuclei
-multimodal and specific sensory association cortices
-paleospinothalamic tract
Describe the efferent outputs from the cingulate cortex.
-entorhinal cortex through congulum and via relay there to the hippocampus
-prefrontal and posterior parietal association areas
What causes lacunar strokes?
Occlusion of penetrating branches of middle cerebral, posterior cerebral, basilar, and anterior cerebral or vertebral arteries.
What are the symptoms of lacunar stroke?
The strokes can be either purely motor or purely sensory.

Progress in stepwise fashion-
Foot drop--> slowing of finger movement--> weakness --> paralysis
What chemical is induced by drugs of abuse?
Delta Fos B
What symptoms are required for a diagnosis of Schizophrenia?
1. 2 of: delusions, halucinations, incoherence, catatonoic behavior, flat or inappropriate affect

2. bizarre delusions

3. prominent hallucinations
What is the difference between Type I and II Schizophrenia?
Type I is predominantly positive symptoms, acute, and has good response to drugs

Type II is mostly negative symptoms, chrinic and unresponsive to drugs
Describe the physical characteristics of a schizophrenic brain.
-enlarged cerebral ventricles
-loss of cerebral tissue
-atrophy of hippocampus and amygdala
-changes in structure of cells of cingulate cortex
-hypometabolism of frontal lobes (neg symptoms)
-hypermetabolism of left temporal region (positive symptoms)
-abnormality in density of dopamine receptors in basal ganglia
What is implicated as the cause of Schizophrenia?
-maybe excess dopamine
-maybe blocking of NMDA receptor
What receptors are blocked by conventional schizophrenic medications?
D2 receptors
What are the three diagnostic features of autism?
Social impairment
Communication impairment
Repetitive behaviors
Describe the neuropathological findings in autism.
-no gross lesions
-increased cell packing density of hippocampus, entorhinal cortex, amygdala
-loss of purkinje cells of cerebellar cortex
-decreased muscarinic 1 and nicotinic receptor binding in cerebral cortex
-decreased GAD expression in cerebral cortex (turns glutamate to GABA)
What is the different between a totipotent cell, a multipotent cell and a progenitor cell?
Totipotent = can reproduce itself and any other cell in the body
Multipotent = can regenerate other cells, but only of the same tissue type
Progenitor cells = can only give rise to specific cells within a cell type
What does it mean to say that the development of the neocortex involves a process of "inside-out" placement of new neurons?
Neurons in layer 6 complete development before layers 5,4,3,2,1
What are the two sites of neural stem cells?
Subventricular zone
Subgranular zone
Where is the subventricular zone?
Lines lateral ventricle
Where is the subgranular zone?

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