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greek: within the head
endbrain or cerebral hemispheres – devs 5th week
unpaired central forebrain – means between brain
optic vessicles
develop from proencephalon – become retinas
stalks of optic vessicles
become optic nerves
posterior pituitary – midline stalk from diencephalon
part of rhombencephalon continuous with spinal cord
myelo means
medulla oblongata
same as myelencephalon
controls movement, receives-integrates signals, sends to thalamus, then to cortex
loss of order of bodily motion
cerebellum purpose
integrates messages from all senses, smooths movements through integration
four hills on back of midbrain
corpora quadrigemina, tectum, or tectum mesencephali
inferior colliculi
central conduction paths for hearing
superior colliculi
central conduction paths for vision
dorsal 2/3 of the diencephalon-central processing station, contains many nuclei
signals from body surface – touch, pain, temperature
perception of the body itself – signals from muscles, tendons, joint capsules, ligaments
thalamus processing functions
exteroception, proprioception, auditory and visual sensation
medial geniculate body
thalamic nuclei responsible for processing auditory sensation
lateral geniculate body
thalamic nuclei responsible for processing visual information
lateral posterior thalamic nucleus
information processing
ventral portion of diencephalon – regulates viscera and endocrine function
latin for mucus – origin of pituitary
cerebral cortex
mantle or pallium of cerebrum
convolutions on surface of brain
fissures on cortex
immediately under olfactory cortex – contains nuclei
cortical nucleus
part of the amygdala – fuses with the olfactory cortex
limbic system
amygdala and hippocampus – axons descend to hypothalamus
corpus striatum
core of cerebrum – programs complex body movements
globus pallidus
district of corpus striatum – large cells, inner zone
darker zone of corpus striatum, smaller cells, has 2 areas
2 zones of striatum
caudate nucleus and putamen
trailing end of cell mass of striatum
husk portion of darker area of corpus striatum
in anterior fossae of skull
frontal lobe
in middle fossae
temporal lobe
in posterior fossae
hindbrain & cerebellum
extradural hematoma
acute onset, usually blow to head, middle meningeal A
subdural hematoma
subtle onset, small vessels
pineal gland
unpaired, superior posterior diencephalon- third eye – can calcify with age – pineal sand-radioopaque
midbrain structures
essential for consciousness
medial temporal lobe herniation
through tentorial notche, presses midbrain against tentorium, produces coma,death
cerebellar tumour
when causing herniation thru foramen mag., compresses medulla – cardio/resp. centres=rapid death
grey matter
cell bodies (on surf. cerebellum + cereb. hemispheres)
white matter
basal ganglia
caudate (tail) nucleus, and lentiform nucleus
lentiform nucleus made up of
putamen and globus pallidus
3 types of white matter axons
association, commissural, projection
association fibres
don’t cross midline
short association fibres run between
gyrus – adjacent gyrus
long association fibres
between one lobe - another lobe in same hemisphere
commissural fibres
cross midline – connect matching areas of both brain halves
projection fibres
descending from cortex to bulb or spine (cortico-bulbar or spinal) or asc. from sp. cord: spinothalamic
bundle of fibres
uncinate fasciculus
hook shaped from frontal to temporal lobe – assoc. fibres
arcuate fasciculus
also called superior longitudinal fasciculus
simplest motor pathway descending
2 paths (synapses) brain – sp.cord, sp. cord to musc
upper motor neurons
brain to spinal cord
lower motor neurons
spinal cord to muscle.
simplest sensory path ascending
projection fibres – 3 paths: into sp. cord, into nucleus, into brain
projection fibre paths ascending
join nucleus in medulla, synapse w/cell bodies of nucleus
ascending projection fibres – order in sp. cord
innermost: sacral, lumbar, thoracic, cervical outermost
choroid plexus
cells within ventricles – produce CSF
CSF pathways
L+R lateral ventricles-for. of munroe-3rd ventricle-aqueduct-foramen of magendie + luschka – subarachnoid sp – arach. granulations – venous blood
hydrocephalus normal cause
impaired absorption (NOT excessive secretion)
hydrocephalus results
ventricles grow, brain atrophy, head expansion
hydrocephalus clinical
increased skull circumference, if left: impaired consciousness, ‘cracked-pot’ skull sound, setting sun eyes, lids retract, can’t look up, thin scalp, dilated veins
how does hydrocephalus arrest?
intracranial pressure returns to normal, CSF absorption balances production
damage from hydrocephalus
white matter damage, gliotic scarring, can also damage grey matter
problems with bodily movement
explosively rapid automatism
slow and wormlike movement
athetosis (means: without position)
constant shifting from foot-foot
incipient athetosis
small lens shaped mass of caudal diencephalon
subthalamic nucleus: satellite of globus pallidus
function of subthalamic nucleus
contralateral motor control of arms and legs (works with globus pallidus)
lesions of substantia nigra
affect face, cause parkinsons
symptoms of parkinsons
mask-like face, muscular rigidity, pill-rollers tremor, difficulty initiating movements
extrapyramidal motor system
corpus striatum (putamen and caudate), subthalamic nucleus, and substantia nigra
extrapyramidal dyskinesias
chorea, athetosis, hemiballism, parkinsons
main target of extrapyramidal system
acts through thalamus on motor cortex
motor unit
a single motor neuron and the muscular fibres it innervates
4 parts of motor unit
cell body, axon, synapse (neuro-musc. junction) musc. fibres
muscle fibre types in motor unit
always same within one motor unit
how many fibres of motor unit contract if action pot.
all – all or nothing response
fine motor control (hands) because of
more motor units
small number of large motor units
stronger, but not finely controlled
what occurs if motor unit pathology
weakness, wasting
disease effecting muscle fibres
primary myopathy
disease effecting motor neurons
primary neuropathy
example of a primary neuropathy
muscular dystrophy
explain pathology of primary myopathy
indiv. musc. fibres die, so size of motor unit decreases, therefore, muscle weakens
primary neuropathy – what occurs
motor neuron degeneration – deinnervated muscles, which can be adopted by other, healthy neurons
primary neuropathy characterized by
decrease in # of motor units, with each motor unit growing in SIZE.
how is neuro vs. myopathy detected?
measurement of size and # of motor units
example of neuropathy
higher order systems in hierarchy of motor systems
cortex, basal gang.,thalamus, cerebellum – direct 1st order systems
1st order systems
muscle spindle, pathways to brainstem, cerebellum
lowest order system
lower motor neuron
largest diameter motor neuron
alpha motor neuron
smallest diameter motor neuron
gamma motor neuron
what innervates voluntary muscle
alpha motor neurons
arrangment of neurons in common layer of spinal cord performing similar functions
form motor nuclei of cranial nerves
lower motor neurons in brain stem
motor neuron groupings within spinal cord
rexed laminae
lower motor neuron size and character
very large with extensive branching (dendritic arborization)
purpose of branching of lower motor neurons
receive wide range of input and integrate into single coordinated response
cluster of motor neurons within grey matter
motor pools – segmental associations for specific motor nerves, eg: L4-L5-S1
Example of T1 motor pool lesion
would effect hand
character of lower motor neurons
large, myelinated, signals travel quickly
final common pathway
lower motor neuron influences motor unit directly, based on input from higher order systems
lou gehrigs disease
amyotropic lateral sclerosis – lower motor neuron lesions
lower motor neuron lesion characteristics
weak or paralyzed muscle, no reflexes, flaccid paralysis, atrophy, fasciculations
explain reflex arc
muscle and synergist stretch, musc. spindle sends signal to sp. cord, causes musc. to contract, and antagonists to relax
muscle spindle purpose
monitor muscle length and speed of contraction
pathway of muscle spindle
monosynaptic, responsible for reflexes
sensitivity of muscle spindle controlled by
small intrafusal muscle fibres
character of voluntary motor pathway
corticobulbar,corticospinal – high speed, rapid movement changes
voluntary motor path neuron cell bodies are where
in the neocortex, expecially precentral gyrus – brodmans area 4
path of voluntary motor pathway neurons
transverse corona radiata and internal capsule, gather on ventral midbrain as basis pedunculi, travel through pons
bundle of axons at medulla
motor nuclei of cranial nerves
formed by some of pyramidal neurons which end at brainstem
2 parts of voluntary motor pathway
corticobulbar, corticospinal
projection of corticobulbar axons
usually bilateral
what corticobulbarly innervated structures are not bilateral
hypoglossal nucleus, and nucleus to lower half of face
condition where forehead is innervated, ½ of rest of face not
forehead sparing, caused by certain corticobulbar nuclei being contralateral, but most not. forehead is bilaterally innervated
bilateral nerve arrangement goes where?
gaze centres to coordinate movements
entry of corticospinal axons into spinal cord
caudal end of medulla
% of axons crossing midline at medulla
formation caused by crossing fibres?
decussation of pyramids in ventral medulla
crossed fibres of decussation go where in sp. cord?
lateral corticospinal tract in lateral funinculus
uncrossed fibres go where in sp. cord
ventral corticospinal tract in ventral funinculus
do uncrossed fibres cross midline?
eventually, in the segment where the lower motor neurons are that they innervate
termination of corticospinal axons?
on lower motor neurons along length of pathway

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