Lecture 9: Control of Motor Function I

Question 1

what is the function of interneurons

Answer 1

they are responsible for most of the spinal cord integrative function

Question 2

what are renshaw cells

Answer 2

inhibitory cells in anterior horns of spinal cord

Question 3

what is the neurotransmitter of the upper motor neuron

Answer 3

glutamate

Question 4

what is the neurotransmitter of the lower motor neuron

Answer 4

acetylcholine

Question 5

define motor unit

Answer 5

composed of a single motor neuron and the muscle fibers it innervates

Question 6

define motor neuron pool

Answer 6

group of motor neurons that innervate fibers within the same muscle

Question 7

what is a muscle spindle and what does it detect

Answer 7

a group of fibers arranged in parallel with extrafusal fibers that detects both dynamic and static changes in muscle length

Question 8

what is the golgi tendon organ and what does it detect

Answer 8

encapsulated sensory receptor through which muscle tendon fibers pass through
arranged in series with extrafusal fibers that detect muscle tension

Question 9

describe nuclear bag fibers

Answer 9

detect rate of change in muscle length

innervated by group Ia afferent and dynamic gamma efferents

Question 10

describe nuclear chain fibers

Answer 10

detect static change in muscle length
innervated by group II afferents and static gamma efferents
more numerous
multiple nuclei arranged in a single row

Question 11

describe gamma motor neurons

Answer 11

innervates intrafusal muscle fibers
keeps muscle spindles taut
acetylcholine is neurotransmitter

Question 12

where does stimulation of gamma motor neurons come from

Answer 12

lengthening of entire muscle

Question 13

what are the types of gamma motor neurons

Answer 13

alpha gamma
gamma dynamic
gamma static

Question 14

describe the functions of a muscle spindle.

Answer 14

Send info to the nervous system about muscle length or rate of change of length
Functions as a sensory receptor

Question 15

describe a dynamic stretch reflex

Answer 15

Signals transmitted from primary nerve endings
Elicited by rapid stretch or unstretch
Opposed sudden changes to muscle length

Question 16

describe a static stretch reflex

Answer 16

Transmitted by both primary and secondary endings

Causes degree of muscle contraction to remain relatively constant

Question 17

describe the flexor reflex

Answer 17

A painful stimulus is applied to the hand, as a result the flexor muscles of the upper arm become excited, thus withdrawing the hand from the painful stimulus
Pass first into the spinal cord interneuron pool of neurons and only secondarily to the motor neurons

Question 18

describe the withdrawal reflex

Answer 18

A pain stimulus on the inward side of the arm elicits not only contraction of the flexor muscles of the arm but also contraction of abductor muscles to pull the arm outward

Question 19

describe the crossed extensor reflex

Answer 19

Signals from sensory nerves cross to the opposite side of the cord to excite extensor muscles

Question 20

what is the function of the premotor cortex

Answer 20

Anterior part develops a motor image of the total muscle movement that is to be performed
Generates plan for movement

Question 21

what is the function of the supplementary motor cortex

Answer 21

Programs complex motor sequences

Responsible for mental rehearsal for a movement

Question 22

what is the function of the motor cortex

Answer 22

Images excite each successive pattern of muscle activity required to achieve the image

Question 23

What are the outputs of the posterior motor cortex?

Answer 23

Primary motor cortex

Basal nuclei and thalamus

Question 24

How is Broca’s area related to associated respiratory and voluntary eye movement fields?

Answer 24

Respiratory activation of the vocal cords can occur simultaneously with the movements of the mouth and tongue during speech
Eye movement field located above Broca’s area

Question 25

describe upper motor neurons

Answer 25

Are entirely within the CNS
Originate in the cerebral cortex, cerebellum, brainstem
Form descending tracts

Question 26

describe lower motor neurons

Answer 26

Begins in CNS
From anterior horns of spinal cord
From brainstem cranial nerve nuclei
Made up of alpha motor neurons
Make up spinal and cranial nerves

Question 27

what is a mirror neuron

Answer 27

Becomes active when a person performs a specific motor task or when he or she observes the same task performed by others.