Motor System and Reflexes

Question 1

Where is the primary motor cortex located?

Answer 1

precruciate and postcruciate gyri and the rostral suprasylvian gyrus

Question 2

What are the motor tracts of the primary motor cortex?

Answer 2

lateral and ventral corticospinal tract

Question 3

What are precise and refined voluntary control of extremities controlled by?

Answer 3

the contralateral side of the cerebrum

Question 4

What percentage of motor fibers from the corticospinal tract terminate in cervical segments?

Answer 4

50

Question 5

What percentage of motor fibers from the corticospinal tract terminate in thoracic segments?

Answer 5

30

Question 6

What percentage of motor fibers from the corticospinal tract terminate in lumbosacral segments?

Answer 6

20

Question 7

What are interneurons?

Answer 7

local circulatory neurons mediating signals between neurons

Question 8

What are the type of interneurons?

Answer 8

excitatory, inhibitory, and renshaw cells

Question 9

What do excitatory internuerons release?

Answer 9

Ach and glutamate

Question 10

What do inhibitory interneurons release

Answer 10

GABA and glycine

Question 11

What do renshaw cells release?

Answer 11

glycine

Question 12

What does tetanus toxin do?

Answer 12

prevents the release of GABA and glycine from inhibitory and renshaw cells

Question 13

What are the types of spinal motor neurons?

Answer 13

alpha motor neurons and visceral motor neurons

Question 14

What are the alpha motor neurons located in and what type of motor neuron is it?

Answer 14

extrafusal muscles; lower motor neuron

Question 15

What are the visceral motor neurons located in?

Answer 15

smooth and cardiac muscles

Question 16

What is a motor unit?

Answer 16

a motor neuron and all of the muscle fibers it innervates

Question 17

What do motor units do?

Answer 17

generate appropriate contractile force of muscles needed for any given task

Question 18

What do upper motor neurons control?

Answer 18

lower motor neurons in the brain stem and spinal cord mostly via interneurons

Question 19

What do lower motor neurons innervate?

Answer 19

directly innervate muscles - skeletal, smooth, and cardiac

Question 20

What is a spinal reflex?

Answer 20

A relatively simple, stereotyped motor response to sensory input of sufficient intensity

Question 21

What is the myotatic reflex?

Answer 21

a reflex that induces stretching of the target muscle by tapping the associated tendon

Question 22

What nerve does the quadriceps reflex test the function of?

Answer 22

the femoral

Question 23

What cord segments does the quadriceps test?

Answer 23

L4-L6

Question 24

What muscle does the quadriceps reflex test test?

Answer 24

the quadriceps femoris

Question 25

What is the reflex pathway for the quadriceps reflex test?

Answer 25

muscle spindle to primary sensory neuron to motor neuron to skeletal muscle to golgi tendon organ

Question 26

What type of neurons does the reflex circuit use?

Answer 26

sensory, interneuron, and motor

Question 27

What are some spinal reflexes other than the myotatic reflex?

Answer 27

flexor (or withdrawal) reflex, crossed extensor reflex, perineal reflex

Question 28

How must the animal be positioned for the flexor/withdrawal reflex?

Answer 28

lateral recumbency

Question 29

How is the flexor or withdrawal reflex executed?

Answer 29

A stimulus to the foot triggers a flexion of the limb

Question 30

How must the animal be positioned for the crossed exensor reflex?

Answer 30

the animal must be standing

Question 31

How is the crossed extensor reflex executed?

Answer 31

Flex one limb, the opposite limb extends to support the increased weight on that limb

Question 32

How does the perineal reflex work?

Answer 32

Contraction of the anal sphincter and tail flexion in response to tactile stimulation of the perineum

Question 33

What nerves does the perineal reflex test test?

Answer 33

pudendal and caudal nerves

Question 34

What cord segments does the perineal reflex test test?

Answer 34

S1-S3

Question 35

What muscle does the perineal reflex test the function of?

Answer 35

anal sphincter and flexion tail muscles

Question 36

What is motor neuron disease classified by?

Answer 36

any disease that directly affects the function of motor neurons (perikarya and/or axons)