MODULE 8- ARPIN STUDY GUIDE

Question 1

what does each lower motor neuron innervate

Answer 1

muscle fibers within a single muscle

Question 2

motor neuron pool

Answer 2

all the motor neurons innervating a single muscle

Question 3

somatotopic organization of motor neuron pools in dorsal/ventral horn of SC

Answer 3

ventral

Question 4

medial ventral horn

Answer 4

-terminates bilaterally
-control of posture + locomotion

Question 5

lateral ventral horn

Answer 5

-terminates only ipsilatterally
-fine control of distal extremities

Question 6

2 types of lower motor neurons

Answer 6

-α-motor neurons (striated muscles)
-γ-motor neurons (sensory receptors/muscle spindles)

Question 7

motor unit

Answer 7

α-motor neuron + all the muscle fibers it innervates

Question 8

innervation number

Answer 8

number of muscle fibers innervated by one α-motor neuron

Question 9

size principle

Answer 9

orderly recruitment of motor neurons

S -> FR -> FF

Question 10

regulation of muscle force (2)

Answer 10

-number of active motor units
-firing rate of active motor units

Question 11

muscle spindle

Answer 11

intrafusal fibers arranged in PARALLEL

Question 12

what 3 intrafusal fibers do muscle spindles have

Answer 12

-dynamic nuclear bag fibers
-static nucleus bag fibers
-nuclear chain fibers

Question 13

3 neurons of muscle spindle

Answer 13

-Ia afferent
-II afferent
-gamma (γ) motor neuron

Question 14

what does gamma (γ) motor neuron do

Answer 14

contracts intrafusal fibers making Ia afferents more sensitive (gain)

Question 15

stretch reflex

Answer 15

stretching muscle ->
increased discharge from Ia afferents

Question 16

stretch reflex increases/decreases alpha motor neurons of agonist

Answer 16

increases

Question 17

stretch reflex increases/decreases alpha motor neurons of antagonist

Answer 17

decreases
-reciprocal innervation

Question 18

golgi tendon organs

Answer 18

sense changes in tension

Question 19

what axons innervate GTOs

Answer 19

Ib axons

Question 20

positive/negative feedback system for GTOs

Answer 20

negative

Question 21

negative feedback system of GTOs

Answer 21

increased tension ->
increase in Ib neuron activity ->
inhiits alpha motor neuron of agonist + excites alpha motor neuron of antagonist

Question 22

flexion reflex

Answer 22

-stimulates cutaneous (nociceptor)
-excites interneuron circuits in SC

Question 23

what does flexion reflex lead to

Answer 23

withdrawal of limb from painful stimuli

Question 24

flexion reflex- inhibition/excitation of extensor of stimulated foot

Answer 24

inhibition

Question 25

flexion reflex- inhibition/excitation of flexor of the stimulated foot

Answer 25

excitation

Question 26

flexion reflex- what happens to other limb

Answer 26

opposite response
-crossed extension reflex

Question 27

central pattern generator (CPG)

Answer 27

-rhythmic patterns of movement
-supraspinal commands are not necessary