Lecture 7: Spinal Cord, Control of Motor Function

Question 0

What do Renshaw cells do?

Answer 0

Receive collateral branches from alpha motor neurons and results in lateral inhibition

Question 1

What neurons are capable of spontaneous activity and are 30x as numerous as anterior motor neurons?

Answer 1

Interneurons

Question 2

What apparatus detects changes in muscle length via stimulation of sensory fibers in region of intrafusal fibers?

Answer 2

Muscle spindle

Question 3

Stimulation of sensory fibers from central region of intrafusal fibers results from?

Answer 3

Lengthening of muscle and contraction at ends of intrafusal fibers

Question 4

T/F: Dynamic stretch reflex opposes sudden changes to muscle length.

Answer 4

True

Question 5

T/F: Static reflex causes muscle contraction to remain constant.

Answer 5

True

Question 6

Gamma-_____ motor neurons excite nuclear bag intrafusal fibers and Gamma-_____ motor neurons excite nuclear chain intrafusal fibers.

Answer 6

Gamma-dynamic

Gamma-static

Question 7

What is the function of the posterior motor cortex?

Answer 7

Make sure the motor cortex signal is what the body actually wants to happen

Question 8

Input signals enter the motor cortex in layers…?

Answer 8

2-4

Question 9

TQ: Upper motor neurons are entirely within the _____.

Answer 9

CNS

Question 10

Lower motor neurons are made up of _____.

Answer 10

Alpha motor neurons

Question 11

75-85% of upper motor neurons decussate in _____, the rest decussate near _____.

Answer 11

Pyramidal system

Synapse

Question 12

The lateral corticospinal tract is made up of fibers that have crossed in the _____ and supply _____ levels of spinal cord.

Answer 12

Medulla

All

Question 13

The anterior corticospinal tract is made up of fibers that cross near the _____ and supply _____.

Answer 13

Synapse

Neck and Upper limbs

Question 14

TQ: Which neurons pass through an internal capsule?

Answer 14

Upper motor neurons

Tertiary sensory neurons?

Question 15

TQ: What is the pathway of the corticospinal tract?

Answer 15

Site of origin–>internal capsule–>medullary pyramids–>x in lower medulla–>lateral columns of spinal cord

Question 16

Which cells send collaterals back to the cortex?

Answer 16

Giant pyramidal cells (Betz)

Question 17

What are 2 major functions of the coritcospinal tract?

Answer 17

1) add speed and agility to conscious movements (especially of hand)
2) provide a high degree of motor control (movement of fingers)

Question 18

TQ: What do corticospinal tract lesions cause?

Answer 18

Reduced muscle tone
Clumsiness
Weakness
Not complete paralysis

Question 19

What does the corticobulbar tract innervate?

Answer 19

The head

Question 20

Where does the rubrospinal tract decussate?

Answer 20

Lower brain stem

Question 21

What 3 tracts make up the extrapyramidal system?

Answer 21

Rubrospinal
Vestibulospinal
Reticulospinal

Question 22

What do lesions of the rubrospinal tract cause?

Answer 22

Impaired distal arm & hand movement & intention tremors

Question 23

What is the vestibulospinal tract mainly involved with and what does it synapse with?

Answer 23

Maintenance of upright posture, LMNs

Question 24

Which tract controls movements of trunk and limbs that do not require balance?

Answer 24

Reticulospinal tract

Question 25

The _____ reticular nuclei excite antigravity muscles & the _____ reticular nuclei relax antigravity muscles.

Answer 25

Pontine, medullary

Question 26

The macula of the _____ determines head orientation when head is upright and the macula of the _____ determines head orientation when the head is lying down.

Answer 26

Utricle

Saccule

Question 27

TQ: Why is there no statonconia on the crista ampullaris?

Answer 27

Because it’s moved by movement of fluid

Question 28

T/F: When cilia on hair cells bend, hundreds of cation channels open causing depolarization, then close causing hyperpolarization.

Answer 28

True

Question 29

What is the Crista Ampullaris?

Answer 29

Small crest within each ampulla

Question 30

What is the Cupula?

Answer 30

Loose mass of gelatinous tissue on top of crista