Quiz 2 Flashcards
(88 cards)
0
Q
White Matter in Spinal Cord: columns & what carries sensory and motor information
A
White matter: dorsal, lateral, ventral columns
Dorsal Root Ganglia: holds sensory neurons
Ventral Nerve Root: holds motor neuron axons
1
Q
Motor Association Cortex (Name of 2, Function, Location, Lesions cause)
A
Name: Supplementary motor area, Premotor cortex
Function: higher order motor planning
Location: anterior to primary motor cortex
Lesions: no severe deficits, cause deficits in higher order sensory analysis or motor planning
2
Q
Central Gray Matter: what is sensory vs. motor, intermediate zone, can be divided…
A
Sensory-dorsal horn (Rex laminae 1-6)
Motor-ventral horn (Rex laminae 8-9)
Intermediate Zone-interneurons and specialized nuclei
Can be divided into nuclei or laminae with different functions
3
Q
White Matter Spinal Cord: Enlargements
A
Cervical and Lumbosacral due to plexuses
4
Q
General Organization of Motor Systems (feedback loops): cerebellum and basal ganglia, sensory inputs, UMN, LMN, descending motor pathways
A
- Cerebellum and basal ganglia: project back to cerebral cortex via thalamus, not LMN
- Sensory inputs play important role in motor control and participate in motor circuits
- UMN arise from cerebral cortex and brain stem and synapse with LMN that project to muscles in periphery
- Descending motor pathways divide into later and medial motor systems.
5
Q
Lateral Motor Systems (fxn) vs. Medial Motor Systems
A
Lateral/Contralateral: -lateral corticospinal tract- rapid, skilled movements -rubrospinal tract- not well defined Medial: -anterior corticospinal tract -vestibulospinal tract -reticulospinal tract -tectospinal tract
6
Q
Medial Motor Systems (function, descend, control what movements, lesions)
A
- Function: postural tone, balance, head and neck movements, gait
- Descend ipsilaterally or bilaterally
- Control movements that involve multiple, bilateral spinal segements
- Small deficits result from lesions
7
Q
Lateral Corticospinal Tract or Pyramidal Tract
A
- most important motor tract: lesions along its course produce severe deficits that enable precise clinical localization
- controls movement of extremities
- descends contralaterally with 85% of fibers crossing at pyramidal decussation
- half of fibers arise from primary motor cortex and half from posterior or supplementary motor areas
- 3% of neurons are giant pyramidal cells called Betz Cells
- cortex –> posterior limb of internal capsule –> pyramidal decussation
8
Q
Two Divisions of Motor System
A
- Somatic- skeletal system
2. Visceral/Autonomic- SNS and PSNS nerves and ganglia; enteric nervous system
9
Q
Divisions of Autonomic Nervous System
A
- Sympathetic- fight or flight
2. Parasympathetic- rest or digest
10
Q
Sympathetic NS (preganglionic neurons arise from, spinal cord levels, preganglionic NT and receptor, postganglionic NT and receptor)
A
Thoracolumbar division:
- preganglionic neurons arise in intermediolateral nucleus and travel via the intermediolateral cell column
- spinal cord: T1-L2
- preganglionic NT: Ach –> nicotinic receptors
- postganglionic NT: NE –> adrenergic receptors
11
Q
Sympathetic NS (2 sets of sympathetic ganglia; length of fibers)
A
- Paravertebral ganglia- along the spinal cord bilaterally; form the sympathetic chain/trunk ganglia; allows efferents to reach other parts of body
- Prevertebral ganglia- unpaired; 3 types are celiac ganglion, superior mesenteric ganglion, inferior mesenteric ganglion
- —pre is short, post is long
12
Q
Parasympathetic NS (spinal cord, travel, preganglionic NT and receptor, postganglionic NT and receptor, length of fibers)
A
- arises in cranial nerve nuclei and S2-S4
- preganglionic fibers travel to terminal ganglia in or near organs
- preganglionic NT: Ach –> nicotinic
- postganglionic NT: Ach –> muscarinic
- pre long, post short
13
Q
Enteric Nervous System
A
Involved with digestion:
- peristalsis
- GI secretions
- nerve plexus in gut wall
14
Q
Arteries Supplying Spinal Cord
A
- Vertebral Arteries- form spinal arterial plexus
- anterior spinal artery: runs ventral surface supplying anterior horns & anterior and lateral white matter columns, supplies approx 2/3 off anterior cord
- posterior spinal artery: runs right and left dorsal surface supplying posterior columns & part of posterior horns - Spinal Radicular Arteries
15
Q
Spinal Arterial Plexus, Radicular Arteries, Great Radicular Artery
A
-Spinal Arterial Plexus: anterior and posterior spinal arteries; supply below upper cervical levels; form anastomotic network with radicular arteries
-Radicular Arteries: supply most of lower levels of spinal cord; approx 6-8 pairs of radicular arteries
Great Radicular Artery of Adamkiewicz: supply lumbar and sacral regions of cord; arises between T5 and L3
16
Q
Vulnerable Zone for blood supply
A
- decreased perfusion T4-T8
- between lumbar and vertebral arterial blood supply
- susceptible to infarction
17
Q
Veins
A
- Batson’s plexus: blood drains here before reaching systemic circulation
- located in epidural space
- do not have valves
18
Q
UMN from cerebral cortex go to and fxn, UMN from brainstem from brainstem go to and fxn
A
**Cerebral cortex –> lateral white matter –> LMN in lateral ventral horn –> distal limb muscles for skilled movements
**Brainstem –> anterior medial white matter bilaterally –> LMN in medial ventral bilaterally –> axial and proximal limb muscles for posture and balance
19
Q
Rex Laminae part of motor control
A
7,8,9
20
Q
Levels of Current for Premotor and Supplementary Motor Cortex
A
Premotor- low level stimulation causes muscle to move
Supplementary- high levels of current for higher levels
21
Q
Primary Motor Cortex: Betz Cells
A
- Layer 5 motor neurons with direct path to LMN Betz cells (3-5%)
- Remaining UMN are non Betz neurons
22
Q
UMN axons go to what tracts?
A
corticobulbar and corticospinal tracts
23
Q
Corticobulbar Tract: axons end where, UMN path innervates what, most go bilaterally with what exception
A
- Axons end in brainstem
- UMN path innervates cranial nerve nuclei, reticular formation (posture, equilibrium, etc), red nucleus
- most go bilaterally, EXCEPT those that control lower face and tongue
24
Functional Organization of Motor System
- homonculus actually organized by movements
- small current stimulates several muscles
- with certain areas, a movement could be obtained by stimulation in several different areas
- suggested: linkage of neurons and circuits that spread the stimulus
- suggested: overlap of regions in charge of initiating different motions
25
Force and Firing Rate
- increase UMN stimulation --> increase in LMN --> larger force
- firing rates of active neurons changes prior to movements
26
Activity of primary motor neurons correlates with:
1. size of muscle contraction
2. direction of force produced by muscles- neurons have preferred directions, one neuron likes to move muscle in one way, neurons give less activity as movement changes direction
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Spike Triggered Averaging
- able to measure activity of 1 UMN on LMN
- found: 1 UMN stimulated activity of multiple different muscles = muscle field
- multiple neurons can activate same muscle
- UMN stimulate movement not just a single muscle group
28
Michael Graziano found
- prolonged stimulation of UMN evoked complex movements
| - hands to mouth, hand to central space, defensive postures
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What do motor maps represent?
- map of musculature
- map of movement
- map of intention of movement
30
Premotor Cortex: function, Brodmann's areas, receives input from
- Function: motor functions
- Brodmann's areas 6,8,44/45 on lateral frontal lobe surface, areas 23 and 24 on medial surface
- Receives input from inferior and superior parietal lobes (sensory) and from rostral division of frontal lob (motivation/intention)
31
Premotor Cortex: how it influences motor behavior, function, difference between Primary Motor Cortex
- Influences motor behavior directly via corticobular and corticospinal tracts and stimulate LMN, and indirectly via reciprocal connects with primary motor cortex
- Function: use info to choose appropriate movement
- Different from primary motor cortex: strength of connection to LMN because it doesn't make as many monosynaptic connections to alpha motor neurons
32
Premotor Cortex Divisions
1. Lateral Premotor- external cues
2. Medial Premotor- internal cues
- both involved in selection of movement or sequence of movements
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Lateral Premotor of Premotor Cortex: function and damage to area
- Function: neurons firing at appearance of external cues and organizing muscles needed for production of sounds and selection of action needed to perform task
- Damage: leads to difficulty moving in response to visual or verbal cue (Broca's area)
34
Medial Premotor of Premotor Cortex: function, damage, divisions
- Function: helps select and initiate movement from internal cues
- Damage: effects self initiated movements
- Divisions: front eye field (helps direct gaze to area), cingulate sulcus (express emotional behavior)
35
Mirror Motor Neurons: portion of premotor cortex, function, part of what
- Ventrolateral portion of premotor cortex
- neurons fire not only to perform the action, but also during observation of an action
- part of imitation learning, empathy
- encoding actions and intentions of others
36
Vestibular Nuclei: input from what, function, start of what
- composed of 4 nuclei located in pons and medulla
- primary input is from vestibulocochlear nerve- semicircular canals & otolith organs
- start of vestibulospinal tract
- has UMN that project to CN 3,4,6 nuclei
- function: balance, posture, orient visual gaze
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Lateral Vestibulospinal Tract: start, travel, function
- Start at lateral vestibular nucleus
- Travel anteriorly to synapse on medial LMN that stimulate proximal limbs
- Helps with balance and posture
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Medial Vestibulospinal Tracts: start, travel, function
- Starts at medial vestibular nucleus
- Travels anteriorly and bilaterally to medial ventral horn of cervical cord
- Regulates head position in response to information from semicircular canals
39
Reticular Formation: what are they, where are they, functions
- Scattered groups of nuclei not seen in discrete bundles
- Extend from midbrain to medulla and form a network of circuits
- Many functions: coordinate axial and proximal muscles, CV and resp control, reflexes, eye movements, **sleep and wake states, start of reticulospinal tract
40
Reticulospinal Tract: terminates where, functions, rise from
- Terminates in medial ventral horn
- Modulates axial and girdle muscles; helps orient motion of head
- UMN in superior colliculus give rise to it
41
Rubrospinal Tract: start, descends, terminates, arises, importance
- Starts in red nucleus
- Descends laterally and terminates in lateral aspect of ventral horn
- Arises from magnocellular neurons within nucleus
- not as important in humans, but in some mammals
- extremity movements, spinal cord injury recovery, movement velocity
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Summary: feedforward/feedback in reticular formation or vestibular nuclei
- Reticular Formation: provides feedforward posture adjustments, influenced by motor centers in cortex, hypothalamus, and brainstem
- Vestibular Nuclei: provides feedback to a rapid response for postural instability
43
Cat's Forepaw Strike: inactivate reticular formation vs. active rf
- Activated RF: forepaw movement occurs also with postural adjustment in other legs
- Inactivated RF: electrical stimulation of motor cortex only triggers forepaw motion
44
Rhesus Monkeys: direct pathway cut but indirect in tact...what symptoms return when; conclusions
- Immediately: able to use axial and proximal muscles, but difficulty with isolated distal movements of hands
- Weeks: some return of hand movement but ability to perform independent fine movement of fingers never return
- Conclusion: indirect pathway to spinal cord involve proximal muscles, direct pathway gives speed, agility, precision
45
Upper Motor Neuron Syndrome- initial symptoms
- weakness, hypotonia- greatest in limbs
- Spinal Shock-lack of input to circuits
- trunk muscles preserved
46
Upper Motor Neuron Syndrome-days later
- regain some function, but pattern of motor behavior develops
- positive Babinski sign
- spasticity (increased muscle tone, hyperreflexia, clonus)- loss of suppressive influences of cortex on postural centers
- inability to perform fine motor movements
47
Clonus
- rhythmic pattern of contractions
| - occurs due to stretching and then relaxation of muscle spindles
48
Extensive UMN lesions can lead to: decerebrate rigidity and decorticate rigidity
- decerebrate rigidity: extension of leg and arms, head is arched back, damage to brain stem and cerebellum
- decorticate rigidity: arms flexed and bent inward on chest, hand clenched into fists, legs extended and feet turned inward, higher up damage
49
Functions of Brainstem vs. Cortex
- Brainstem: posture and balance
| - Cortex: executing, planning, choosing appropriate movements
50
Functions of Local Circuit Neurons
- manage system
- determine spatial and temporal patterns
- receive direct input from sensory neurons
- mediate sensory motor reflexes
- enable coordination of rhythmic and stereotyped behavior
- can cause another alpha motor neuron to fire or inhibit
51
4 Distinct Interactive Subsystems of Neural Circuits Responsible for Movement
1. local circuitry
2. UMN-synapse with local circuit neurons or LMN
3. cerebellum-detect motor error between intended movement and movement performed
4. basal ganglia- suppress unwanted movements and prepare UMN for initiation of movement
52
Motor Neuron Pool
all motor neurons innervating a single muscle
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Topography of Motor Neuron Pools- medial vs. lateral
- medial: axial musculature more important for trunk, posture, balance; medial ventral horn and span many segments
- lateral: distal extremities and coordinate skilled behavior; shorter and span less than 5 segments; ipsilateral
54
2 Types of LMN
1. gamma motor neurons- intrafusal muscle fibers intimately linked to muscle spindle; regulate sensory input by setting length of intrafusal fibers
2. alpha motor neurons- extrafusal muscle fibers; tell striated muscle fibers what to do and generate forces needed for posture and movement
55
Motor Unit
single alpha motor neuron and all extrafusal muscle fibers it innervates constitute the smallest unit of force in muscle that can be activated to produce movement
56
Small Motor Units
- slow motor units
- fatigue resistant
- red in color: myoglobin, capillaries, mito
- slow contractions, small forces- posture
- tonically active with sustained effort
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Large Motor Units
- pale in color: few mito, capillaries, myoglobin
- fast fatigable
- larger forces and rapid contractions for movement
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Intermediate Motor Units
- fast fatigue resistant
| - 2x the force of small units, but fatigue resistant
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Size Principle
-order of recruitment: slow --> fast fatigue resistant --> fast
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Muscle Spindle- maintains what, classes, 2 fibers
- maintains length***
- nuclear bag and nuclear chain
- Group Ia afferents: large diameter sensory axons, respond phasically to small stretches, dynamic nuclear bag fibers, emphasize velocity of fiber stretch
- Group II afferents: flow spray endings, respond tonically at a frequency proportion to degree of stretch, static nuclear bag fibers
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Reciprocal Innervation
- sensory neuron connections with those alpha motor neurons that innervate same or antagonistic muscles
- excitatory = same muscles/agonist
- inhibitory = antagonists
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Dynamic Gamma Neurons vs. Static Gamma Neurons firing in response to stretch
- Dynamic: enhance dynamic response of Ia
- Static: enhance static response of Ia and static input of II, decrease dynamic input of Ia
- Coactivation of alpha and gamma motor neurons allow spindles to function at all muscle length during movement and postural adjustment
63
What is gain? What does it mean if gain reflex is high or low? What about difficult movements?
- Gain = level of gamma activity adjusted by UMN or local circuitry
- Gain reflex high = small stretch causes large increase in alpha motor neurons and in tension
- Gain reflex low = greater stretch to generate smallest forces and tension
- Difficult movements = increase in gamma activity for rapid and precise movements
64
Golgi Tendon Reflex: maintains what, innervation, function
- maintains muscle force***
- innervated by Ib sensory axons
- works with contraction of muscle and pressure of tendon
- act by negative feedback due to inhibitory function of Ib axons to decrease activation of a muscle when large forces are generated
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Ib Axons
- contact GTOs, UMNs, cutaneous receptors, muscle spindles, joint receptors, etc.
- contact inhibitory circuits --> synapse with alpha motor neurons to maintain steady level of force
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Lower Motor Neuron Syndrome
- paralysis of what they are innervating
- paresis (weakness) if damaged but not destroyed
- areflexia: no reflexes
- loss of muscle tone and atrophy
- fibrillations = fine twitching due to single denervated fiber
- fasiculations = exaggerated twitching due to denervated motor unit (alpha motor neurons)
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Unilateral Face, Arm, and Leg Weakness/Paralysis: No Sensory Deficits (side of lesion, location, signs/sx)
- side: contralateral to weakness above decussation
- location: corticospinal and corticobulbar tract fibers
- signs/sx: UMN signs, dysarthria, ataxia
68
Unilateral Face, Arm, and Leg Weakness/Paralysis: Associated Sensory Deficits (side of lesion, location, signs/sx)
- side: contralateral to weakness above decussation
- location: above medulla through primary motor cortex
- signs/sx: somatosensory deficits, oculomotor and visual deficits, aphasia, neglect, dysarthria, ataxia, UMN signs
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Unilateral Arm and Leg Weakness or Paralysis (side of lesion, location, signs/sx)
- side: contralateral to weakness in motor cortex or medulla, ipsilateral to weakness in cervical spinal cord
- location: arm and leg area of primary motor cortex, corticospinal tract from lower medulla to C5
- signs/sx: UMN signs, aphasia, hemineglect, man in barrel, medullary sx
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Unilateral Face and Arm Weakness or Paralysis (side of lesion, location, signs/sx)
- side: contralateral to weakness above decussation
- location: face and arm areas of primary motor cortex
- signs/sx: UMN signs, dysarthria, parietal lobe extension/sensory loss, dominant hemisphere lesion-Broca's aphasia, nondominant hemisphere lesion-hemineglect
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Unilateral Arm Weakness or Paralysis (side, location, signs)
- side: contralateral to weakness if in motor cortex, ipsilateral to weakness if in peripheral nerves
- location: arm area of primary motor cortex or peripheral nerves supplying arm
- signs/sx: motor cortex lesion- UMN signs, cortical sensory loss, aphasia, occasional subtle face and arm, peripheral nerve lesion-LMN signs, weakness, sensory loss
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Unilateral Leg Weakness or Paralysis (side, location, signs)
- side: contralateral in motor cortex, ipsilateral in spinal cord or peripheral nerves
- location: leg area of primary motor cortex, lateral corticospinal tract < T1, peripheral nerves supplying leg
- signs/sx: motor cortex lesion-UMN signs, cortical sensory loss, frontal lobe signs; spinal cord lesion-UMN signs, Brown Sequard syndrome, altered sphincter tone; peripheral nerve lesion-LMN signs, weakness and sensory loss
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Unilateral Facial Weakness or Paralysis (side, location, signs/sx)
- side: ipsilateral to weakness in facial nerve or nucleus, contralateral to weakness in motor cortex or internal capsule
- location: facial nerve, face area of primary motor cortex, genu of internal capsule, facial nucleus or fascicles in brainstem
- signs/sx: facial nerve or nucleus lesion-Bell's Palsy sx, forehead involvement, nucleus involvement; motor cortex or genu lesion-forehead usual spared, dysarthria, unilateral tongue weakness, subtle arm involvement possible, sensory loss, aphasia
74
Bilateral Arm Weakness or Paralysis (side, location, signs)
- side: bilateral
- location: medial fibers of both lateral corticospinal tracts, bilateral cervical spinal ventral horns, peripheral nerve or muscle disorders
- signs/sx: central cord syndrome, anterior cord syndrome
75
Bilateral Leg Weakness of Paralysis (side, location, signs)
- side: bilateral
- location: bilateral leg areas of primary motor cortex along medial surface of frontal lobes, lateral corticospinal tracts < T1, cauda equina syndrome
- signs/sx: bilateral medial frontal lesions-UMN signs, confusion, apathy, grasp reflexes, incontinence; spinal cord lesions-UMN signs, sphincter or autonomic dysfunction; bilateral peripheral nerve/muscle disorders-cauda equina syndrome, distal segmental polyneuropathies, prox NM disorder or myopathies
76
Bilateral Arm and Leg Weakness or Paralysis (side, location, signs/sx)
- side: bilateral
- location: bilateral leg and arm areas of motor cortex, bilateral lesions of corticospinal tracts from lower medulla to C5
- signs/sx: combine unilateral arm and leg weakness signs/sx
77
Generalized Weakness or Paralysis (side, location, signs)
- side: bilateral or diffuse disorder
- location: bilateral motor cortex, bilateral corticospinal or corticobulbar tracts from corona radiata to pons, diffuse disorders of LMN/NMJ/muscles, bilateral ventral pontine
- signs/sx: UMN signs, LMN signs, respiratory depression with generalized weakness, sensory loss, EOM dysfunction, pupillary issues, autonomic dysfunction, impaired conscioiusness
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Spastic Gait (localization, description)
- localization: unilateral or bilateral corticospinal tracts
- description: stiff legged, toe walking inward, tight calf muscles
- cause: CP
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Ataxic Gait (localization, description)
- localization: cerebellar vermis or other midline cerebellar structures
- description: wide based, unsteady, stagger side to side
- alcohol
80
Vertiginous Gait (localizations, description)
- localization: vestibular nuclei, vestibular nerve, semicircular canals
- description: wide base, unsteady, staggering
- alcohol
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Frontal Gait (localization, description)
- localization: frontal lobes or frontal subcortical white matter
- description: slow, shuffling, barely raise feet off floor, similar to Parkinsonian gait
82
Parkinsonian Gait (localization, description)
- localization: substantia nigra or other regions of basal ganglia
- description: slow, shuffling, narrow based, difficulty initiating walking
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Dyskinetic Gait (localization, description)
- localization: subthalamic nucleus, other regions of basal ganglia
- description: dancelike, flinging and ballistic
- Huntington's disease
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Tabetic Gait (localization, description)
- localization: posterior columns or sensory nerve fibers
| - description: high stepping, foot flapping, sway
85
Paretic Gait (localization, description)
- localization: nerve roots, peripheral nerves, NMJ, muscles
| - description: waddling, Trendelenburg gait, knee buckling
86
Painful Gait (localization, description)
- localization: peripheral nerve or orthopedic injury
| - description: avoid putting pressure, facial expression
87
Functional Gait (localization, description)
- localization: pscyhologically based
| - description: pt says they have poor balance, swaying movements without ever falling
