00-neuroanat-01
Terms
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- rhombencephalon
- hindbrain
- mesencephalon
- midbrain
- prosencephalon
- forebrain
- encephalon
- greek: within the head
- telencephalon
- endbrain or cerebral hemispheres – devs 5th week
- Diencephalon
- unpaired central forebrain – means between brain
- optic vessicles
- develop from proencephalon – become retinas
- stalks of optic vessicles
- become optic nerves
- neurohypophysis
- posterior pituitary – midline stalk from diencephalon
- myelencephalon
- part of rhombencephalon continuous with spinal cord
- myelo means
- marrow
- medulla oblongata
- same as myelencephalon
- cerebellum
- controls movement, receives-integrates signals, sends to thalamus, then to cortex
- ataxia
- 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
- thalamus
- dorsal 2/3 of the diencephalon-central processing station, contains many nuclei
- exteroception
- signals from body surface – touch, pain, temperature
- proprioception
- 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
- hypothalamus
- ventral portion of diencephalon – regulates viscera and endocrine function
- pitus
- latin for mucus – origin of pituitary
- cerebral cortex
- mantle or pallium of cerebrum
- gyri
- convolutions on surface of brain
- sulci
- fissures on cortex
- amygdala
- 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
- striatum
- darker zone of corpus striatum, smaller cells, has 2 areas
- 2 zones of striatum
- caudate nucleus and putamen
- caudate
- trailing end of cell mass of striatum
- putamen
- 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
- axons
- 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
- bulbar
- brainstem
- projection fibres
- descending from cortex to bulb or spine (cortico-bulbar or spinal) or asc. from sp. cord: spinothalamic
- fasciculus
- 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
- automatisms
- problems with bodily movement
- explosively rapid automatism
- chorea
- 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
- polio
- 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
- laminae
- 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
- pyramids
- 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
- 80-85%
- 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