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PHYSIOLOGY > ME03 - Motor System 1 - SC, Cortex, Brainstem > Flashcards

ME03 - Motor System 1 - SC, Cortex, Brainstem Flashcards

1
Q

Neural pathways that control the sequence and pattern of muscle contractions
Distributed throughout brain and spinal cord

A

Motor System

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2
Q

What constitutes a MOTOR UNIT?

A

Consists of a single motor neuron and the muscle fibers that it innervates

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3
Q

For fine control, a single motor neuron innervates only a few muscle fibers. True or False

A

True, Example: Eye Muscle

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4
Q

For larger movements, a single motor neuron may innervate thousands of muscle fibers. True or False?

A

True, Example: Postural Muscles/Axial Muscles

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5
Q

Force of muscle contraction is graded by recruitment of additional motor units

A

Graded Response - Size Principle of Muscle

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6
Q

What principle is applied in “As additional motor units are recruited, more motor neurons are involved and more tension is generated”

A

Size Principle of Muscle

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7
Q

2 Types of Motor Neurons

A

Alpha Motor Neurons | Gamma Motor Neurons

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8
Q

o Innervate extrafusal skeletal muscle fibers
o Action potentials in _ motor neurons lead to action potentials in the extrafusal muscle fibers they innervate, which results in contraction

A

Alpha Motor Neurons

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9
Q

o Innervate specialized intrafusal muscle fibers
o Adjust the sensitivity of the muscle spindles

A

Gamma Motor Neurons

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10
Q

2 Types of Muscle Fibers

A

Extafusal Fibers | Intrafusal Fibers

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11
Q

o Make up the bulk of muscle
o Innervated by alpha motor neurons
o Provide the force for muscle contraction

A

Extrafusal Fibers

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12
Q

o Smaller than extrafusal muscle fibers
o Are innervated by gamma motor neurons
o Encapsulated in sheaths to form muscle spindles
o Are too small to generate significant force

A

Intrafusal Fibers

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13
Q

Mnemonic for Motor Neuron Fiber

A

AEGIS (Alpha Motor - Extrafusal | Gamma Motoe - Intrafusal)

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14
Q

Central role in skeletal muscle control
Cell bodies are topographically arranged within the ventral horn of the spinal cord
Axons innervate skeletal muscle fibers

A

Alpha Motor Neurons

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15
Q

Cell bodies of Alpha Motor Neuron receive numerous synaptic connections from:

A

o proprioceptors
o higher levels of the CNS including the brainstem, basal ganglia, cerebellum, and motor cortex

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16
Q

Topographic Arrangement of muscles of the trunk

A

Medial

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17
Q

Topographic Arrangement of muscles of the extremities

A

Lateral

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18
Q

Topographic Arrangement of limb flexors

A

Dorsal

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19
Q

Topographic Arrangement of limb extensors

A

Ventral

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20
Q

Cells responsible for the synapse with the pool of motor neurons when stimulated

A

Renshaw Cells&raquo_space; predominantly inhibitory
bring about recurrent or feedback inhibition

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21
Q

NTs involved in the muscle contraction

A

Glycine - inhibitory | Strignin - cause prolonged muscle contraction

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22
Q

What type of synaptic arrangement is exemplified by Renshaw cells?

A

One to Many

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23
Q

What neurotransmitter is released by Renshaw cells?

A

Glycine

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24
Q

What type of neuronal circuit is exemplified by Renshaw cells?

A

Divergent

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25
Q

Sense of awareness of POSITION of the body in space

A

Proprioception

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26
Q

Proprioception progress of the movement by sensory receptors within the muscles and joints. True or False?

A

TRUE

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27
Q

Where can proprioceptors be found?

A

Mechanoreceptors within muscles and joints | Two Major Proprioceptor are (1) Muscle Spindle (2) Golgi Tendon Organ

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28
Q

Function of proprioceptors beside the sense of awareness of position?

A

Provide the CNS with information regarding muscle length, position and tension (force)

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29
Q

Small, encapsulated intrafusal fibers
Lie in parallel with extrafusal muscle fibers

A

Muscle Spindle - (STRETCH)

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30
Q

What are the innervations of Muscle Spind (afferent, efferent)

A

Afferents via group Ia (primary or annulospiral endings) and group II fibers (secondary endings)&raquo_space; respond to muscle stretch

Efferents via gamma motor neurons&raquo_space; regulates sensitivity of the spindles

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31
Q

The finer the movement required, the greater the number of muscle spindles in a muscle. True or False?

A

TRUE

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32
Q

Where is y-neuron found in intrafusal fibers?

A

In the belly of the muscle

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33
Q

2 Types of Intrafusal Fibers in Muscle Spindle?

A

Nuclear Bag Fibers | Nuclear Chain Fibers

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34
Q

o Detect the rate of change in muscle length (fast, dynamic changes)
o Innervated by group Ia afferents

A

Nuclear Bag Fibers - Have nuclei collected in a central bag region

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35
Q

o Detect static changes in muscle length
o Innervated by group II afferents
o More numerous than nuclear bag fibers
o Have nuclei arranged in rows

A

Nuclear Chain Fibers

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36
Q

There is very intense period activity of primary endings (Group IA) during the stretch compared to secondary endings. True or False?

A

True; this is related to the tendency to overstretch “Wear & Tear” of Muscles

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37
Q

Role of Muscle Spindles

A

Comparators for maintenance of muscle length
Important during goal-directed voluntary movements
o Voluntary changes in muscle length are initiated by motor areas of the brain
o Includes changes to the set-point of the muscle spindle system

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38
Q

Simultaneous activation of extrafusal fibers (by alpha motor neurons) and intrafusal fibers (by gamma motor neurons)
Readjusts the sensitivity of muscle spindles continuously as the muscle shortens
Allows the muscle spindles to be functional at all times during a muscle contraction

A

C0-ACTIVATION

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39
Q

Alpha-Gamma Coactivation (Stretch Spindle/Intrafusal)

A
  1. Alpha motor neuron fires and gamma motor neuron fires.
  2. Muscle contracts.
  3. Stretch on centers of intrafusal fibers unchanged. Firing rate of afferent neuron remains constant.
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40
Q

Without Gamma Motor (Alpha-motor only) Neurons

A
  1. Alpha motor neuron fires.
  2. Muscle contracts
  3. Less stretch on center of intrafusal fibers
  4. Firing rate of spindle sensory neurons decreases.
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41
Q

Mechanoreceptors that lie within the tendons of muscles immediately beyond their attachments to the muscle fibers

A

Golgi Tendon Organ - senses tension in the tendon

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42
Q

Golgi Tendon Organ respond to degree of tension within muscles. True or False?

A

TRUE

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43
Q

Which fibers is responsible to relay this information to the CNS (in particular the spinal cord and cerebellum)

A

Group Ib afferent fibers

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44
Q

Follow the pathway of GTO from muscle contraction to relaxation

A

Muscle contracts&raquo_space; INC tension&raquo_space; GTO&raquo_space; CNS&raquo_space; Interneuron&raquo_space; INHIBIT a-motor neurons&raquo_space; Relaxed

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45
Q

Why are Group Ib fibers of GTO have short periods of intense firing?

A

They have short periods of intense firing since they are series with muscle fibers and well-adapted to monito muscle tension.

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46
Q

Rapidly executed, automatic, and stereotyped response to a given stimulus
Simplest form of irritability associated with the nervous system

A

Reflex

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47
Q

Components of a Reflex Arc

A

o Receptor
o Afferent neuron that synapses in the CNS
o Efferent neuron that sends impulses to an effector
o Interneurons may be present between the afferent and efferent neurons

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48
Q

Classify neural reflexes by EFFERENT DIVISION THAT CONTROLS THE EFFECTOR

A

Somatic Motor Neuron controls skeletal muscles
Autonomic Neurons control smooth and cardiac muscle, glands, and adipose tissue.

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49
Q

Classify neural reflexes by INTEGRATING REGION WITHIN CNS

A

Spinal Reflexes do not require input from brain
Cranial Reflexes integrated within the brain

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50
Q

Classify neural reflexes by TIME AT WHICH REFLEX DEVELOPS

A

Innate Reflexes genetically determined
Learned Reflexes acquired through experience

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51
Q

Classify neural reflexes by NO. OF NEURONS IN THE REFLEX PATHWAY

A

Monosynaptic Reflexes have only 2 neurons (one afferent and one efferent)

Polysynaptic Reflexes include one or more interneurons between afferent and efferent neurons.

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52
Q

Only somatic motor reflexes can be monosynaptic. True or False?

A

TRUE

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53
Q

All autonomic reflexes are polysynaptic because they have 3 neurons: one afferent and two efferent. True or False?

A

TRUE

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54
Q

Single synapse between afferent and efferent neurons

A

Monosynaptic Reflex

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55
Q

Two or more synapses between afferent and efferent neurons

A

Polysynaptic Reflex

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56
Q

Reflexes that do not need to go to the brain

A

Spinal Cord Reflexes

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57
Q

Also known as patellar tendon-tap reflex, knee-jerk reflex or Myotactic Reflexes
Stretching of a muscle stimulates the muscle spindle afferents
Plays an important role in the control of posture

A

Muscle Stretch Reflex

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58
Q

Caused by rapid stretch or unstretch/ RAPID CHANGE IN STRETCH
Transmitted from primary sensory or annulospiral endings of the muscle spindles
Oppose sudden changes in muscle length
Lasts within a fraction of a second only

A

Dynamic Stretch Reflex (Ia Only)

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59
Q

Elicited by the continuous static receptor signals
Transmitted by both primary and secondary endings
Causes the degree of muscle contraction to remain reasonably constant
Continues for a prolonged period

A

Static Stretch Reflex (Ia and II)

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60
Q

Muscle spindles prevent oscillation or jerkiness of body movements
Ensure that contraction is relatively smooth, even though the motor nerve to the muscle is excited at a slow frequency

A

Damping Function of Stretch Reflexes

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61
Q

Reinforcement technique for eliciting deep tendon reflexes
o fingers are locked together and one hand pulls against the other while reflex is evoked

A

Jendrassik’s Maneuver

62
Q

What is the physiologic basis of Jendrassik’s Maneuver?

A

When one muscle is stretched, it facilitates a substantial number of alpha motor neurons
Transient increase of gamma motor neuron activity

63
Q

Jendrassiks maneuver facilitates multiple alpha motor neurons. True or False?

64
Q

Oscillation of a stretch reflex

65
Q

When does Clonus occur?

A

Ordinarily occurs only when the stretch reflex is highly sensitized by facilitatory impulses from the brain

66
Q

This is elicited by noxious stimuli
Transmitted by group II, III, IV fibers
Possesses at least one interneuron, and so the most basic flexion reflex is disynaptic
Usually many muscles are involved through polysynaptic pathways

A

Flexor Withdrawal Reflex

67
Q

To achieve withdrawal of a limb:

A

Flexor muscles in the limb must contract while the extensor muscles relax

68
Q

Follow the pathway for “Reciprocal Inhibition”

A
  1. Painful stimulus activates nociceptor.
  2. Primary sensory neuron enters spinal cord and diverges.
  3. One collateral activates ascending pathways for sensation (pain) and postural adjustment (shift in center of gravity)
  4. Withdrawal reflex pulls foot away from painful stimulus.
    Crossed extensor reflex supports body as weight shifts away from painful stimulus.
69
Q

This ensures that the extensor muscles acting on a joint will relax while flexor muscles contract

A

Reciprocal Inhibition

70
Q

Neuronal circuit that causes this reciprocal relation

A

Reciprocal innervation

71
Q

What are the components of Flexor Withdrawal Reflex

A

Diverging circuits to spread the reflex to the necessary muscles for withdrawal

Reciprocal inhibition circuits to inhibit the antagonist muscles

Circuits to cause afterdischarge lasting many fractions of a second after the stimulus is over

72
Q

Stimulation of the flexion reflex frequently elicits extension of the contralateral limb about 250 ms later
Long latency between flexion and crossed extension represents the time taken to recruit interneurons
Helps to maintain posture and balance

A

Crossed Extensor Reflex (More sustained, more time for afterdischarge)

73
Q

What type of neuronal circuit is exemplified by prolonged afterdischarge in crossed extensor reflex?

A

Recurring/Reverberating

74
Q

Responsible for the after discharge

A

Interneurons

75
Q

Golgi tendon organs monitor muscle tension
Negative feedback mechanism that prevents development of too much tension on muscles

A

Inverse Myotactic Reflex (Instantaneous Relaxation)

76
Q

A reaction when tension becomes extreme, reflex inhibitory effects lead to instantaneous relaxation of the entire muscle

A

Lengthening Reaction

77
Q

What are the four major spinal cord reflexes?

A

Muscle Stretch Reflex monosynaptic; muscle stretch (stimulus); Group Ia fibers > Muscle Contraction

GT Reflex di/polysynaptic; muscle tension (stimulus); Group Ib fibers > Muscle Relaxation

Flexor Withdrawal Reflex polysynaptic; Pain (stimulus); II,II, IV fibers > Ipsilateral muscle flexion

Crossed Extension Reflex polysynaptic; Pain (stimulus); II,III,IV fibers > Contralateral Muscle Extension

78
Q

Caused by transection of the spinal cord
Loss of spinal reflexes (areflexia) and flaccid paralysis below the level of the injury
Over the ensuing weeks, spinal cord activity below the level of the lesion returns as the excitability of undamaged neurons increases
May give rise to spasticity of the paralyzed muscle groups

A

Spinal Shock

79
Q

What are the events in SPINAL SHOCK?

A

NEUROGENIC SHOCK
o arterial blood pressure falls instantly
o demonstrates that sympathetic nervous system activity becomes blocked almost to extinction

AREFLEXIA
o may last 2 weeks to several months
o order of return: stretch reflexes, flexor reflexes, postural antigravity reflexes, remnants of stepping reflexes

INCONTINENCE
o sacral reflexes for control of bladder and colon evacuation are suppressed

80
Q

EXAMPLES OF EXTENT OF PARALYSIS

A

Tetraplegia | Paraplegia | Hemiplegia | Bulbocarvernosus Reflex

81
Q

Impairment or loss of motor and sensory function in the arms, trunk, legs, and pelvic organs

A

TETRAPLEGIA / QUADRIPLEGIA

82
Q

Impairment of function of the legs and pelvic organs

A

PARAPLEGIA / BIPLEGIA

83
Q

Total paralysis of the arm, leg, and trunk on the same side of the body
Does not usually result from spinal cord injuries but from strokes

A

HEMIPLEGIA (Stroke)

84
Q

Polysynaptic reflex useful in testing for spinal shock
Checks anal sphincter contraction in response to squeezing the glans penis

A

Bulbocavernosus Reflex

85
Q

Reactions to Bulbocavernosus Reflex

A

Absence indicates spinal shock
First reflex to return after spinal shock
_ once this reflex has returned, all remaining neurologic deficits are considered permanent

86
Q

Contains motor areas
o stimulation will elicit contralateral movements
displays somatotopic arrangement

A

Cerebral Cortex

87
Q

Areas of the body that are capable of especially refined and complex movements (i.e. fingers, lips, and tongue) have a disproportionately LARGE area of representation. True or False?

88
Q

What are the three sub-areas of Motor Cortex?

A

o PRIMARY MOTOR CORTEX
o PREMOTOR AREA
o SUPPLEMENTARY MOTOR AREA

89
Q

located in pre-central gyrus or Brodmann area 4
responsible for the execution of movement
o programmed patterns of motor neurons and voluntary movement

A

Primary Motor Cortex

90
Q

PMA is somatotopically organized. True or False?

A

True, it is called the motor homunculus

91
Q

Epileptic events in the primary motor cortex cause

A

Jacksonian Seizures

92
Q

Immediately anterior to the lateral portion of the primary motor cortex
Forms a portion of Brodmann area 6
Responsible for generating a plan for movement
o transferred to primary motor cortex for execution
Stimulation causes activation of groups of muscles

A

Premotor Area

93
Q

Located in the medial portion of Brodmann area 6 just anterior to the lower extremity portion of the precentral gyrus
Stimulation causes activation of bilateral muscle activation (usually upper extremities)
Programs complex motor sequences

A

Supplementary Motor Area

94
Q

Supplementary Motor Area is active during

A

Mental rehearsal for a movement

95
Q

o Motor speech area
o Converts simple vocal utterances into whole words and complete sentences

A

BROCA’S AREA

96
Q

Controls conjugate eye movement required to shift gaze from one object to another

A

FRONTAL EYE FIELD (Brodmann area 8)

97
Q

Enables movement of head correlated with eyes

A

HEAD ROTATION AREA

98
Q

When damaged, hand movements are lost (motor apraxia)

A

AREA FOR FINE MOVEMENTS OF HAND

99
Q

Motor Outflow of Cerebral Cortex IS carried by what tracts?

A

Corticospinal (pyramidal) and Extrapyramidal tracts

100
Q

Where is the predominant sensory input?

A

Somatosensory system, which receives its input from the thalamus

101
Q

Where is afferent information received?

A

Received from the visual system, cerebellum, and basal ganglia

102
Q

Motor Input of Cerebral Cortex is important because:

A

Used to refine movements, particularly to match the force generated in specific muscle groups to an imposed load

103
Q

originates over a wide area of cortex including both motor and somatosensory areas
more than 80 per cent of the fibers decussate at the pyramids (CERVICOMEDULLARY JUNCTION)

A

Corticospinal Tract

104
Q

MAIN FUNCTION OF Corticospinal Tract

A

predominant pathway for the control of fine skilled manipulative movements of the extremities

105
Q

Hallmark feature of lesions to the corticospinal tract

A

Loss of precise hand movements

106
Q

FLOW OF CORTICOSPINAL TRACT

A

Motor Cortex&raquo_space; Corona radiata&raquo_space; Internal capsule&raquo_space; Cerebral peduncle&raquo_space; Brainstem&raquo_space; Cervicomedullary junction*&raquo_space; Corticospinal tract (A/L)&raquo_space; Anterior horn cell&raquo_space; Ventral root&raquo_space; Peripheral nerve&raquo_space; Neuromuscular junction&raquo_space; Muscle

107
Q

conveys nerve impulses from the motor cortex to skeletal muscles of the head and neck
axons of UMNs descend from the cortex into the brain stem, where some decussate and others do not
provide input to lower motor neurons in the nuclei of cranial nerves III, IV, V, VI, VII, IX, X, XI, and XII

A

Corticobulbar Tract

108
Q

MAIN FUNCTION OF Corticobulbar Tract

A

Control voluntary movements of the eyes, tongue and neck, chewing, facial expression and speech

109
Q

also called CEREBROVASCULAR DISEASE
cessation of blood flow to the brain due to:
o ruptured blood vessel that bleeds into the brain
o thrombosis of a vessel, producing local ischemia

110
Q

Muscles controlled by the damaged areas show a corresponding loss of function. GIVE EXAMPLE OF LOSS OF FUNCTION

A

o clumsiness and loss of fine muscle control
o postural movements may not be affected
o hyperreflexia, hypertonia and spasticity occur with extension of involvement

111
Q

Loss of the ability to prepare for voluntary movement
Ability to execute simple movements is retained

112
Q

LESION to what areas of the brain causes Apraxia

A

Lesions to supplementary and premotor areas

113
Q

o motor neurons that originate in the motor region of the cerebral cortex or the brain stem
o main effector neurons for voluntary movement in layer V of the primary motor cortex (Betz cells)

A

UPPER MOTOR NEURON

114
Q

UMN pathways (above anterior horn cell) include what tracts?

A

_ corticospinal tract
_ corticobulbar tracts
_ extrapyramidal tracts

115
Q

o motor neurons connecting the brainstem and spinal cord to muscle fibers
o bring nerve impulses from the upper motor neurons out to the muscles
o begins at the level of the anterior horn cell in the spinal cord

A

LOWER MOTOR NEURON

116
Q

Total loss of motor function associated with an increase in muscle tone

A

SPASTIC PARALYSIS (UMN)

117
Q

Manifestation of a Spastic Paralysis

A

Associated with clasp-knife phenomenon and hyperreflexia

118
Q

Total loss of motor function associated with a decrease in muscle tone

A

FLACCID PARALYSIS (LMN)

119
Q

Manifestation of a Flaccid Paralysis

A

Associated with floppiness, areflexia or hyporeflexia

120
Q

Reflex extension of the great toe with flexion of the other toes

A

Babinski Reflex

121
Q

How do you test for Babinski Reflex?

A

Evoked by stroking the lateral sole of the foot

122
Q

Presence of Babinski Reflex indicates what type of lesion?

A

indicates an UPPER motor neuron lesion

123
Q

Small, local, involuntary muscle contractions visible under the skin
Arise from spontaneous discharge of a bundle of skeletal muscle fibers

A

Fasciculations

124
Q

Presence of Fasciculations indicates what type of lesion?

A

Lower motor neuron lesion

125
Q

Differentiate UMN vs LMN

A

UMN
INC Muscle Tone, Spastic Paralysis
Hyperreflexia
(+) Babinski, Clonus
Atrophy of Disuse

LMN
DEC Muscle Tone, Flaccid Paralysis
Hyporeflexia
(+) Fasciculations
Atrophy of Denervation

126
Q

Composed of midbrain, pons and medulla

127
Q

Special functions of Brainstem

A

o control of respiration
o control of the cardiovascular system
o partial control of gastrointestinal function
o control of many stereotyped movements of the body
o control of equilibrium
o control of eye movements
o way station for command signals from higher centers

128
Q

Modifies and Refines the activity of the neural circuitry within the spinal cord

A

Descending Motor Control Pathways

129
Q

Example of Descending Motor Control Pathways

A

o pyramidal tract
_ CORTICOSPINAL TRACT
o extrapyramidal tracts
_ RETICULOSPINAL TRACT
_ VESTIBULOSPINAL TRACT
_ RUBROSPINAL TRACT
_ TECTOSPINAL TRACT

130
Q

influence mainly the muscles of the trunk and proximal parts of the limbs
important in maintenance of certain postures and in STARTLE REACTIONS

A

Reticulospinal Tract

131
Q

Two main divisions of Reticulospinal Tract

A

o PONTINE or MEDIAL RETICULOSPINAL TRACT
o MEDULLARY or LATERAL RETICULOSPINAL TRACT

132
Q

originates in the pontine reticular nuclei
projects to the ventromedial spinal cord
general stimulatory effect on both extensors and flexors, with the predominant effect on extensors

A

Pontine Reticulospinal Tract

133
Q

originates in the medullary reticular formation
projects to spinal cord interneurons in the intermediate gray area
stimulation has a general inhibitory effect on both extensors and flexors, with the predominant effect on extensors

A

Medullary Reticulospinal Tract

134
Q

originates in DEITERS nucleus
projects to ipsilateral motoneurons and interneurons

A

Vestibulospinal Tract

135
Q

Important functions of Vestibulospinal Tract

A

o control the activity of extensor muscles
_ stimulation causes a powerful stimulation of extensors and inhibition of flexors

o maintenance of an erect posture
_ selectively controls the excitatory signals to the different antigravity muscles

o making adjustments in response to signals from the vestibular apparatus

136
Q

originates in the SUPERIOR COLLICULUS
projects to the cervical spinal cord
decussates before entry to spinal cord

A

Tectospinal Tract

137
Q

Lesions IN TECTOSPINAL TRACT are always

A

CONTRALATERAL

138
Q

IMPORTANT FUNCTIONS OF TECTOSPINAL TRACT

A

o control of neck muscles
o controlling head and eye movements

139
Q

most important extrapyramidal tract
originates in the red nucleus
afferent information from cortex, cerebellum and basal ganglia
projects to interneurons in the lateral spinal cord
decussates before entry to spinal cord

A

Rubrospinal Tract

140
Q

Lesions in the Rubrospinal Tract are always

A

Ipsilateral

141
Q

IMPORTANT FUNCTIONS OF RUBROSPINAL TRACT

A

controls both flexor and extensor muscles
o stimulation of the red nucleus produces stimulation of flexors and inhibition of extensors

142
Q

Voluntary movements are impaired with lesions in the Rubrospinal Tract. True or False?

143
Q

Differentiate Descending Tracts

A

PONTINE RETICULOSPINAL
-Pontine reticular nuclei; Ventromedial SC projection
-Stimulates flexors and extensors

MEDULLARY RETICULOSPINAL
-Medullary reticular nuclei; Intermediate gray projection
-Inhibits flexors and extensors

VESTIBULOSPINAL
-Deiters nuclei; Ventromedial SC projection
-Stimulates flexors & extensors

TECTOSPINAL
-Superior colliculus; Cervical SC projection
-Contralateral (lesion)
-Control neck muscles

RUBROSPINAL
-Red nucleus; Lateral SC projection
-Contralateral (lesion)
-Stimulates flexors; Inhibit extensors

144
Q

involuntary flexion or extension of arms and legs
occurs when one set of muscles becomes incapacitated while the opposing set is not
indicates a severe medical emergency requiring immediate medical attention

A

Abnormal Posturing

145
Q

Types of Abnormal Posturing

A

o DECORTICATE RIGIDITY
o DECEREBRATE RIGIDITY

146
Q

involuntary flexion of the upper extremities in response to external stimuli
arms flexed, hands are clenched into fists, legs extended and feet turned inward

A

Decorticate Rigidity

147
Q

involuntary extension of the upper extremities in response to external stimuli
head is arched back, arms are extended by the sides, and legs are extended

A

Decerebrate Rigidity

148
Q

Cause DECEREBRATE RIGIDITYE because of the removal of inhibition from higher centers

A

LESIONS ABOVE THE LATERAL VESTIBULAR NUCLEUS

149
Q

Cause DECEREBRATE RIGIDITY because of the removal of central inhibition from the pontine reticular formation

A

LESIONS ABOVE THE PONTINE RETICULAR FORMATION BUT BELOW THE MIDBRAIN

150
Q

Result in DECORTICATE RIGIDITY and intact tonic neck reflexes

A

LESIONS ABOVE THE RED NUCLEUS

PHYSIOLOGY (13 decks)

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