Flashcards in Med Neuro Deck (166):
What are the 3 major components and levels of control of the motor system?
What are the 3 levels of the motor system regulated by?
Basal Ganglia and Cerebellum
What is the final common pathway of the motor system?
The bundle of motor neurons involved in contraction
What are the motor neurons that cause muscle contraction and execute movement?
lower motor neuron
What are the two types of interneurons?
Project to motor neurons, help connect and coordinate motor neurons that contract as a group
What are propiospinal interneurons?
Interneurons that transmit info between multiple spinal cord levels
What are segmental interneurons?
Interneurons that project withina single spinal cord level
What is the medial brainstem pathway and the 3 origins?
Reticulospinal, vestibulospinal and tectospinal
provides basic postural control system, influences axial and proximal muscles
What is the lateral brainstem pathways?
Rubrospinal tract (red nucleus--spinal cord) Tract descends in dorsolateral white matter and terminates in dorsolateral area of ventral spinal cord. Modulate goal-directed limb movements like reaching and manipulation
What is the role of hte primary motor cotex?
executes commands to motor neurons, controls individual finger movement. Coordinates force and direction. Somatically mapped
What is the role of the premotor cortex?
integrates motor movements with sensory input. Coordinates complex sequences of movments and is involved in motor learning
What is teh role of the supplementary motor area?
Important in internally driven, will driven moveents. Formulates an intention
What are the two descending pathways through which the cerebral cortex acts on motor neurons?
lateral corticospinal tract-contralateral limb, digits, goal directed reaching
ventral corticalspinal tract-neck, trunk muscles and postural control
What is teh role of hte lateral corticospinal tract?
contralateral limb, digits and goal directed reaching
What is the role of the ventral corticospinal tract?
involved in neck, trunk muscles and postural control
What are the three types of movment?
Reflex, automatic postural adjustments, and voluntary moveemnts
What are the functions of skeletal muscle?
execute voluntary movements, maintain posture, produce tremendou heat and metabolic energy
What are skeletal muscles made up of?
Parallel bundles of fasicles
fasicles made of muscle fibers
How can complex action potentials in muscle can be recorded with what?
Motor neuron pool
1 muscle can be innervated by many motor neurons, in the smae pool
Medial motor nuclei?
motor neurons that innervate axial muscles of neck
Lateral motor nuclei?
innervate limb muscles, most medial innervate proximal limb muscles
most lateral innervate distal limb muscle
What are slow-twitch motor units?
Innervate slow, red, slow-twitch muscle fibers
smaller fibers; small MN; slow contraction; small tension output
specialized for endurance; fatigue resistant
What are fast fatigable motor units?
Innervate white, fast-twitch fibers
large fibers, large MN, large contraction
fatigue bc glycogen is rapidly depleted
specialized for strength and speed
What are fast fatigue-resistant fibers?
innervate intermediate fibers (btw red and white)
combine fast twitch dynamics and contraction with enough aerobic capacity
specialized for excercise with endurance
Ultimate force exerted by a muscle depends on what?
Rate code: frequency of action potentials
recruitment: Number of motor units firing
size principle: smallest motor units fire first; largest fire last
slow twitch: fire first
fast-twitch: fire second
What are the receptors in muscle that monitor length and tension of muscle?
Muscle spindles and golgi tendon organs
What do muscle spindles do?
made of intrafusal fibers and sense muscle length. Important for propioception. Length of muscle correlates with angle of joints Discharge when muscle stretched
What are the types fo intrafusal fibers in muscle spindle?
Dynamic nuclear bag fibers sense change in length
Static nuclear bag and nuclear chain fibers sense static length
What afferent nerve innervates muscle spindle sense length and rate of change in length?
Ia--convey fasty dynamic response. Code velocity of stretch, very sensitive
what afferent nerve innervates muscle spindel sense static length?
II afferents. Sense static length, slow tonic response. Code duration of stretch
What type of nerve innervates gogli tendon organ?
capsule innervated by Ib affarent
Where is the golgi tendon organ located?
Located at junction of muscle fiber andtendon, in series with 14-20 extrafussal fibers. Intertwined btw collagen fiber mesh
When does Ib afferent nerve discharge?
Innervates golgi tendon and discharges when musccle contracts; precisesly measures force
What is the purpose of golgi tendon reflexes?
protects muscle from too much tendon, and gives procise control of musccle force.
What type of motor neuron innervates muscle spindles?
gamma motor neuron. In comparison to alpha motor nerutons of extrafusal fibers
What is gamma alpha motor coactivation?
During voluntary movment alpha and gamma motor neurons causespindles to shorten keeping them sensitive at al length
What is the stretch reflex?
monosynaptic excitatory reflex
"deep tendon reflex"
strike tendon cause muscle contracts very fast
What is teh mechanism of action of stretch reflex?
muscle lenthened, spindles excited Ia afferent excited. Excites alpha motor neurons to contract. Monosynaptic contraction
disynaptic inhibits antagonist muscle
What are the clinical causes of decreased or absent deep tendon reflex?
indicates problem with component of reflex arc
disease of muscles, neuromusc junction, sensory neurons, lower motor neurons
What are the clincial cause of hyperreflexia?
upper motor neuron lesion
loss of descending inhibitory control
What are the purpose of monosynaptic reflexes?
maintain appropiate amnt of tension
muscle tone balance
smoothe out movement
What si teh crossed-extension reflex?
Withdrawal from painful stimulus
Mechanism of action of crossed-extension reflex?
Adelta nociceptor activated causes excited ipsilateral flexor inhibit ipsilateral extensor
interneurons cross and excite contralateral extensor
What is the golgi tendon reflex?
muslce contracts and puts tension on golgi tendon organ
activates Ib afferent and Ib inhib internueron
used to pick up delicate things. Increase in muscle tension
Inhibitory interneurons do what?
help coordinate reflex actions
pupose is to simplify voluntary control
Descending control does what?
descending neurons from cortex and brainstem modulate reflexes
What is muscular dystrophy?
30 types of a group of chronic hereditary disease, caused by weakness and wasting of skeletal muscles
What is teh most common form of muscular dystrophy in chidlren?
Duchenne's MD, wasting, X-linked
What are the clinical symptoms of Duchenne's muscular dystrophy?
Waddling, lurching gait.
muscle wasting esp at pelvic girdle and hypercontracted muscle fibers
Clinical tests reveal what in Duchenne's muscular dystrophy?
High creatine kinase levels due to muscle damage
elevate before symptoms appear
What is teh cause of Duchenne's muscular dystrophY?
Lack of gene for dystrophin, located on X-chromosome,
protein in cytoskeleton of muscle membrane and stabilizes muscle. Without it muscle shears
What is the tx for Duchenne's?
PT to keep muscles functioning
surgery for scoliosis correction
Corticosteroids to slow muscle deterioration
Prognosis Death at 20-30
What is myathensia gravis?
autoimmune disorder, antibodies to nictonic Ach Receptor in muscle blocking it, crosslinking it triggereing internatlization leading to muscle weakness and easy fatigue
What are teh clinical symptoms of myathensia gravis?
Weakness, especiallly cranial muscles and ptosis
fatigue in oropharyngeal muscles--drooling trouble chewing
What is teh main treatment for myathensia gravis?
Acetylcholinesterase inhibitor (pyridostigmine) prolongs half life of Ach
Plasmapheresis- remove blood and reinfuse with saline or plasma subsititue
What are the clinical symptoms of lower motor neurons?
atrophy of muscles
decreased muscle tone, fatigue
What are the clinical symptoms of upper motor neurons?
incrased muscle tone
weakness in muscle but no atrophy of muscle
What is amyotrophic lateral sclerosis?
Lou Gherig's disease; progressive degeneration of upper and lower motor neurons
muscle atrophy and hardness of spinal cord from scarring of lateral tracts
What causes the scarring of ALS?
Disease of corticospinal tracts, degenerate progressively
loss of motor nuclei in lower brainstem and loss of motor neurons in ventral spinal cord
loss of betz cells and other pyramidal neurons
usually spares ocular muscles and bladder spphincter
What are teh clinical symptoms of ALS?
atrophy of muscles
respiratory muscle weakness
cognitive and behavioral deficity
pseudobulbar effect: emotional incontinence
What is spared in ALS?
eye movemnts, snesory systems, autonomic NS (bladder, Bowels) cognitive and memory sometimes
What is teh ause of ALS?
Unkonwn, cases sporadic and low genetic correlation
What is the Tx for ALS?
90% die in 6 yrs
Riluzole: blocks glutamate release to reduce damage
What is guillain-barre syndrome?
disorder of peripheral nerve, acute inflammatory demyelinating polyneuropathy
rapid onset 1-2 weeks after viral infection, affects both motor and sensory
Sympotoms of Guillain-Barre syndorm?
insensitiivyt to heat and cold
rapid onset of weakness
as it progresses
paralysis of breathing muscles
Loss of stretch reflex and plantar reflexes due to motor weakness
What is the Tx of Guillain Barre?
Plasmapheresis, Iv immunoglobulin therapy
Good prognosis most recover ina year and most make near full recovery
What is the role of the reticular formation?
Helps regulate conciousness and contains respiratory and CV centers
What is the role of the corticospinal tract?
Most important tract; controls voluntary movmeent and fie motor control of limbs
What si teh role of the spinothalamic tract?
transmits sensory inforamtion
What are the somatic motor classification and what do they cover?
Innervate skeletal muscles in the head and neck that are derived from myotomes
What are the branchial motor nuclei?
innervate skeletal muscles derived from branchial arch
motor nucleus of 5
facial nucleus (7)
nucleus ambiguus (9 and 10)
Spinaal Acessory nucleus (11)
What are the visceral motor nuclei?
preganglionic parasympathetic innervation
Inferior Salivatory (9)
Dorsal motor nucleus of 10 (10)
What are the visceral sensory nuclei?
special-taste (rostral nuclus solitarius (7,9, and 10))
General-control of carioresp and digestive function (caudal nucleus solitarius (9 and 10))
What are the somatic sensory nuclei?
Convey touch, pain, temp posion, vibraion, muscles nad joints
trigeminal nucleus (5,7,9,10)
What are the special sensory nuclei?
cochlear nucleu and vestibular nucleui (8)
What part of the cerebellum influences hte control of axial and proximal limb movments and what tract is it a part of?
vermis and part of spinocerebellum
What part of the cerebellum controls distal limbs and what tract is part of?
intermediate zone and part of spinocerebellum
What part of the cerebellum controls planning and initiation of movments?
Lateral zone and part of cerebrocerebellum
What are the 5 major neruonal types of hte cerebellum and what is the excitatory type?
What are the two excitatory afferents of the cerebellar cortex?
Climbing fibers(from contralateral inferior olivary nucleus)--> synapse directly with Purkinje cells
Mossy fibers--> synapse with granule cells which activate Pukinje cells
What are the three layers of the cerebellum?
Molecular layer, purkinje cell layer and granular layer
What does the Molecular layer contain?
Dendrites of Purkinje cells
Parallel fibers of granule cells
climbing fibers from ION
What is contained within the purkinje cell layer?
What is contained within the granule layer?
The deep cerebellar nuclei contains what?
Receives collaterals from climibng and mossy fibers
receive inputs from PUrkinje cells
output is excitatory
What is a denate nuclei?
largest and most lateral nuclei of the deep cerebellar nuclei
receive projections from lateral zone
What is the interposed nuclei?
Emoboliform + blobose; deep cerebellar nuclei receive projections from intermediate zone
What are the inhibiotry neurons of the cerebellum?
Basket and stellate cells in hte molecular layer inhibit purkinje cell
golgi cells in granular layer inhibit granule cells
What does the vesitulocerebellum contain?
flocculondodular lobe and inferior vermis
What does the vestibulocerebellum control?
Control balance and equilibrium while standing or moving. Controls eye movements. Coordinates movements of head and eyes
What is part of the spinocerebellum?
Vermis and intermedaite zone?
What does the spinocerebellum control?
Vermis control of azial and proximal muscle
intermediate zone control of distal movements
ongoing execulation of movements
What is contained within the cerebrocerebellum?
Lateral zone of cerebellum
What is the funciton of the cerebrocerebellum?
Involved in iniation planning and mental rehearsal of complex motor actions
What is the full route of the spinocerebellum major efferents?
Intermediate zone to interposed nuclei to either
-thalamus-motor and premotor cortex and corticospinal tract or
-brain stem (red nucleus) to lateral descending systems
What is the route of the cerebrocerebellum path?
nerves initially form contralateral cortex to lateral zones--dentate nucleus--contralateral red nucleus--thalamus-- then eithe rpons or spinal cord
What is the result of the indirect pathway to the thalamus?
movement is inhibited by thalamus inhibition
What is the result of the direct pahtway to teh thalamus?
Thalamus is disinhibited and movement is facilitated
What 2 different types of output neurons does dopamine affect in the striatum?
Neurons with D1 dopamine receptors excite direct pathway
Neurons with D2 dopamine receptors inhibit indirect pathway
dopamine therefore facilitates movment
What is the cause of parkinsons disease?
degeneration of dopaminergic cells in SNc
What is the cause of huntington disease?
mutation in chromosome 4 leads to degeneration of cholinergic and GABAerigic neurons in striatum
What is the cause of Tardive dyskinesia?
results from long term of antipsychotic agens. which block DA transmission
involuntary movements of face and tongue
What si teh cause of Hemiballismus?
lesion of subthalamic nucleus resulting in violent ball-thrwoing movements of cotnralateral arm
What are the inputs to the cerebellum?
motor information from cord
Visual sensory motor information from cortex
and propioceptive information from the limb
What is the path of omotor informationf rom the spinal cord to the cerebellum?
cord to VSCT to SCP to cerebelulm
What is the path of visual sensory motor information from teh cortex to the cerebellu?
cortex to pontine nuclei to MCP to cerebellum
What is the path of propioceptive information from the limbs to the cerebellum?
limbs to fasciculus gracilus/cuneatus to DSCT and cuneocerebellar tract to ICP to cerebellum
What are the three outcomes of cerebellar outputs
movement, head/eye control and posture and unconcious motor control
Why are symptoms ipsilateral to the cerebellar lesion?
inputs are ipsilateral or doublecrossed
What is ataxia?
uncoordinated muscle movement; problems with speed, range, force and timing
What are clinical symptosm of vermian lesion?
tibuation=tremor of head or trunk
What are a symptoms of flocculonodular lobe lesion?
ocular dymetria=overshoot or undershoot of eyes when focusing on target
slow saccades=slow eye movments
What do lesions of cortex invovle as far as eye movement?
saccades=quick,voluntary eye movements
What is a symptom of lesion of lateral hemisphere?
scanning ataxic speec=slow,effortful
What are the acute causes of cerebellar disorders?
cerebellar stroke, alcohol intoxication and drug overdose (ie phenytoin)
What are the chronic causes of cerebellar disorder?
Essential tremor, spinocerebellar ataxia, tumor (ie astrocytoma)
What is an essential tremor?
most common movement disorder, bilateral postural and action tremor that is persistant
neuodegenerative gradual loss of purkinje cells
Chronic alcoholism causes what changes in the cerebellum?
cerebellar vermian atrophy and acute EtOH intoxicantion which causes dysfunction of vermis
What is the romberg test?
aska patient to stand in place, feet together and close eyes; if they need to step to stabilize the dfecit could be due to cerebellar, propioceptive or vestibular disorder
What occurs if the lateral hemispheres of the cerebellum are lesioned?
influences LCST pathway
and gain appendicular ataxia
What occurs if hte intermediate hemisphere is lesioned?
influences LCS, rubrospinal tract results in appendicular ataxia?
What occurs with a vermis and flocculondoluar lobe lesion?
VCST, reticulospinal tract, vestibulospinal tract-->truncal ataxia
and or balance and vestibuloocular reflexes at hte medial longitutudal fasciculus result in nystagmus/slow saccades
What si spinocerebellar atazia?
gropu of autosomal dominant ataxic disorders caused by degeneration of afferent and efferent cereellar pathways and destruction of purkinje cells
What is the striatum composed of?
putamen, caudate, nucleus accumbens; large cholinergic internurons are located within striatum
What is teh subthalamic nucleus?
Only excitatory nucleus in the striatum and releases gluatamte
What is the corticostriatl pathway?
excitatory path from cortex to striatum mediated by glutamate; cortical input to direct pathway acts like an accelerator and facilitates volitional movment; cortical input to indirect pathway acts like a break
What is the nigrostriatal pathway?
dopaminergic pathways from substantia nigra to striatum that results in opposing efects
direct pathway results in exciattion fo striatum
indirect pathway results in inhibition of striatum
What is the normal striatal affect of activation of the direct pathway?
gaba released and inhibits globus pallidus interna and substantia nigra pars reticula and gaba is not released onto VA/VL thalamus with release of inhibition goes to VA/VL thalamus is activated which actavtes motor cortes and facilitates movment
What does normal striatal actiavtion of indirect pathway cause?
Gaba released and inhibits globus pallidus externa and SNR which means gaba not released onto STN and STN is activated and releases glutamate onto GPi/SNR and this is activated and releases GABA onto thalamus which inbhitis movmet
WHat is the cause of parkinsons dsease?
loss of dopaminergic neurons in substantia nigra pars compacta (hypokinetic movment disorder)
What are the four clinical features of Parkinsons disease?
What is the cause of Huntingtons disease?
neurodegenerative disorder with loss of neurons primarily in the caudate (hyperkinetic movment disorder)
What are the symptoms of huntingtons disease?
dance like near continuous movment of limbs, face and toungue
lesion of caudate is the cause
What is hemiballims?
brief high amplitude irregular movemnts of a limb; caused by a lesion of subthalamic nucleus
What is the definition of encephalopathy?
all 3 domains affected but a lesser degree than coma; some alertness maintained
What is a coma?
loss of alertness, attention, awareness
What is altered consciousness?
if altered emntation from baseline, then lesion could be in bilateral cerebal hemispheresm, bilateral thalami, brainstem ARAS
What is the frontal lobe supplied by?
MCA and ACA
What is Jacksonian march?
seizure that spreads along primary motor cortex
Where is broca's area?
inferior frontal lobe usually the leftside
What artery supplies Broca's area and what occurs when a stroke or tumor disrupts brocas area?
few words, effortful
What is the role of the prefrontal cortex?
sequencing, organizing, abstaction, problem solving
What is the role of the orbitofrontal cortex?
part of limbic system--> memory and emotions
inhibits socially inappropriate behavior
2 most common ways for lesions to this area include head trauma and meningoma
What is the frontotemporal dementia?
atrophy of the orbitofrontal and prefrontal cotex leading to change in personality, poor judgement, and innappropiate behavior
What is the role of hte mesiofrontal cortex?
provides initiative, motivation, goal directed behavior
micturition inhibitory center
What does a lesion of the mesiofrontal cortex cause?
What is the role of the parietal cortex?
primary somatossensory cortex
nondominant association cortex
What occurs due to a lesion of hte association cortex?
loss of stereognosis
What occurs to a lesion of the nondominant association cortex
Whic association cortex (dominant or non-dominant) drives attention to the world?
contains "map of the world"
What is praxis?
ability to execute a learned skilled task sucha s dressing, riding a bicycle or tying a shoe lace
What is apraxia?
inability to performa task despite good comprehension and strength
What is Gerstmann syndrome?
dominant parietal lobe and angular gyrus
What is the result of Wernicke's aphasia?
fluent lots of nonsensical words come out
smaller branch of MCA stroke
What occurs during a conduction aphasia?
arcuate fibers damaged due to a smaller branch of MCA stroke
What is global aphasia and cause?
Full MCA stroke at its proximal end
What is Kluver-Bucy syndrome?
bilateral anterior temporal poles and b/l amygdala lesion
innaporpriate sexual displays
depression v overactivity
Alzheimer's disease often has what?
severe hippocampal atrophy
Damage to occipital cortex results in what type of disturbance??
homonymous visual field defects
presence of a homonymous hemianopia indicates what?
cortical or subcortical disease
What causes macular sparing?
VF deficit with a PCA stroke; macular vision is spared bc crtiical area of brain recieves dual supply
What are the aterial supplies of the macula?
What is the cause of balint syndrome?
MCA-PCA watershed infacts; alzheimer's
What is Balint SYndrome?
simultanagnosia=inability to perceive the visual field as a whole
optic ataxia=inability to point/reach for object in visual field under visual guidance
ocular apraxia=inability to look at objects in VF using saccades
lesions of bilateral occipital-parietal ccortices