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Human physiology > Lecture 9: Spinal cord and Brainstem Control of Motor Function I > Flashcards

Lecture 9: Spinal cord and Brainstem Control of Motor Function I Flashcards

1
Q

Interneuron characteristics

A 
30x as numerous as anterior motor neurons
Bipolar shape
Small and highly excitable
Capable of spontaneous activity
Most are inhibitory- GABA
Some excitatory- Glutamate
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2
Q

Renshaw cells are what located where and use what NT

A

Inhibitory cells located in anterior horns of spinal cord

Glycine

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3
Q

Renshaw cells receive collateral branches from ___

A

Alpha motor neurons

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4
Q

Renshaw cells transmit inhibitory signals to who resulting in what

A

Surrounding motor neurons, resulting in lateral inhibition and enhanced fluidity of limb movement

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5
Q

What is it called when Renshaw cell transmits inhibitory signal to same motor neuron

A

Recurrent inhibition/negative feedback

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6
Q

Sensory and motor neurons are afferent/efferent

A

Sensory afferent

Motor efferent

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7
Q

Upper neuron axons project

A

To spinal cord interneurons or lower motor neuron

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8
Q

Lower motor neuron axons project

A

From spinal cord to effector

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9
Q

Neurotransmitter of upper lower neuron to lower motor neuron

A

Glutamate

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10
Q

Lower motor neurons found in

A

Anterior gray portion of spinal cord or cranial nerve nuclei of brain stem

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11
Q

LMN use what neurotransmitter

A

Acetylcholine

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12
Q

Cranial nerves are unique _____

A

Lower motor neurons

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13
Q

Motor unit

A

Single motor neuron and muscle fibers it innervates

Composed of extrafusal fibers

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14
Q

Motor neuron pool

A

Group of motor neurons that innervate fibers within the same muscle

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15
Q

Small motor neuron characteristics

A

Innervate few muscle fibers
Lowest thresholds
Fire first
Small force

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16
Q

Large motor neuron characteristics

A

Innervate many muscle fibers
Highest thresholds
Fire last
Largest force

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17
Q

Recruitment

A

Refers to the increase in tension of muscle contractions by the activation of additional motor units

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18
Q

Ia inhibitory neurons

A

Inhibits antagonistic muscle
Signal from muscle spindle
Avoids spasticity

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19
Q

Ib inhibitory neurons

A

Autogenic inhibition reflex
Golgi tendon activated with stretch
Connects with Ib to inhibit same muscle
Responsible for smooth muscle contraction and protects muscles from tears

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20
Q

Excitatory interneurons involved in and receive stimuli from

A

Spinal reflex to remove extremity from damaging stimulus

Sensory group III afferents

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21
Q

Muscle spindle consists of and description

A

Group Ia and group II afferents (small gamma MNs)
Arranged in parallel with extrafusal fibers
Detect both dynamic and static changes in muscle length-corrects for increase in muscle length
Consists of 3-12 intrafusal fibers

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22
Q

Golgi tendon organ consists of/descripiton

A

Group Ib afferents
Arranged in series with extrafusal fibers
Detect muscle tension

23
Q

Pacinian corpuscle consists of/description

A

Group II afferents

Detect vibration

24
Q

Free nerve endings consist of/description

A

Group III and IV afferents

Detect noxious stimuli

25
Q

Sensory nerve fiber groups I-IV myelination

A

Groups I-III are myelinated, IV is not

26
Q

A fibers are

A

Somatic, myelinated

27
Q

Types of A fibers and description

A

Alpha-Largest, Type I
Beta- Type II
Gamma
Delta- smallest,, type IV

28
Q

B fibers

A

Lightly myelinated

Preganglionic fibers of ANS

29
Q

C fibers

A

Unmyelinated
Found in somatic and autonomic systems
Also referred to as type IV

30
Q

Sensory fibers grouped from high speed to low speed

A

A-alpha/A-beta 30-120m/sec
A-delta- 4-30m/sec
C fibers- less than 2.5m/sec

31
Q

Nuclear bag fibers

A

Intrafusal
Detect rate of change in muscle length
Innervated by group Ia Afferents & dynamic y Efferents
Multiple nuclei in central bag like configuration

32
Q

Nuclear chain fibers

A 
Intrafusal
Detect static change in muscle length
Innervated by group II Afferents and static y Efferents
More numerous than nuclear bag
Nuclei arranged in single row
33
Q

Alpha motor neuron characteristics

A

Most numerous
Innervate effector-skeletal muscle
NT- Acetycholine

34
Q

Gamma motor neuron characteristics

A

Innervates intrafusal fibers
Keeps muscle spindles taut
NT- Acetycholine

35
Q

Muscle spindle Ay neurons suppy

A

Supply small intrafusal fibers in middle of muscle spindle

36
Q

Muscle spindle gamma-dynamic

A

Excite nuclear bag intrafusal fibers

37
Q

Muscle spindle gamma-static

A

Excite nuclear chain intrafusal fibers

38
Q

Brain areas that control gamma motor neurons

A

Bulboreticular region of brain stem
Cerebellum
Basal nuclei
Cerebral cortex

39
Q

Dynamic stretch reflex

A

Signals transmitted from primary nerve endings

Opposes sudden changes to muscle length

40
Q

Static reflex

A

Transmitted by both primary and secondary endings

Causes degree of muscle contraction to remain relatively constant

41
Q

Stretch reflex description

A

Stretching of muscle stretches Ia afferent fibers
Ia afferents synapse directly on a-motor neurons of same muscle
The muscle contracts and decrease tension on spindle
Synergistic muscles are activated and antagonistic inhibited

42
Q

Golgi tendon organ description

A

Arranged in series with extrafusal fibers
Stimulated by contracting or stretching of muscle
Opposite of the stretch reflex

43
Q

Golgi tendon organ circuitry

A

Type Ib afferent–> inhibitory interneuron–> anterior motor neuron

44
Q

What is after-discharge

A

Result of persistent neural activity in polysynaptic circuits. It prevents the muscle from relaxing for some time

45
Q

Premotor and supplementary motor areas

A

Generate a plan for movement and transmit to primary motor cortex
Signals generated here cause more complex patterns of movement

46
Q

Supplemental vs premotor areas

A

Premotor cortex develops a motor image of the total muscle movement to be performed
Supplementary cortex programs complex sequences and is responsible for mental rehearsal of a movement

47
Q

Posterior motor cortex circuit

A

Posterior MC–> primary MC

Posterior MC–> basal nuclei/thalamus–> primary MC

48
Q

Motor cortex- pyramidal cells in what layer/ input signals inter what layer

A

5th-pyramidal

2-4th- input signals enter

49
Q

Neurons in 6th layer communicate with

A

Other regions of the cerebral cortex

50
Q

Upper motor neuron full description

A

All in CNS
Orginate in cerebral cortex, cerebellum, brain stem
Form descending tracts

51
Q

Lower motor neuron full description

A

Begin in CNS from anterior horns of SC or brainstem
Made up of alpha motor neurons A-alpha
Make up spinal and cranial nerves

52
Q

Medial activation system

A

Innervate postural and girdle muscles

53
Q

Lateral activation system

A

Associated with distally located muscles for fine movement

54
Q

Nonspecific activating system

A

Facilitate local reflex arcs

Human physiology (16 decks)

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