Neuromotor Basis For Motor Control Part 2

Question 1

Grey matter

Answer 1

H shaped central portion
Contains cell bodies and axons

Question 2

2 horns of spinal cord

Answer 2

Dorsal (posterior) horns
Ventral (anterior) horns

Question 3

Dorsal horns

Answer 3

Sensory neurons

Question 4

Ventral horns

Answer 4

Alpha motor neurons (terminated in skeletal muscle)
Interneurons

Question 5

Function of spinal cord

Answer 5

Reflexive movement
Transmit ascending and descending neural signals

Question 6

2 types of reflexive movement

Answer 6

Monosynaptic
Polysynaptic

Question 7

monosynaptic reflex

Answer 7

• 1a afferent
• muscle spindle detects a stretch in the muscle
• direct synapses from sensory to motor neuron of same muscle causes contraction

Question 8

Polysynaptic reflex

Answer 8

• 1b afferent
• from tendon send signal of change in muscle force
• sensory nerve synapses on interneuron
• interneuron if excitatory can cause contraction of antagonist (withdrawal) or inhibitory and inhibit contraction of same muscle (relaxation)

Question 9

What is reciprocal inhibition

Answer 9

Relaxation of the antagonist muscle during activity of the agonist

Question 10

What happens during reciprocal inhibition

Answer 10

Muscle spindle detects change in length
- 1a afferent directly synapses on alpha motor neuron and on inhibitory interneuron
- then synapses with alpha motor neuron of antagonist muscle

Question 11

Neural pathway of motor

Answer 11

Descending

Question 12

Neural pathway of sensory neurons

Answer 12

Ascending

Question 13

2 types of descending motor tracts

Answer 13

Lateral corticospinal tract
Lateral vestibulospinal tract

Question 14

Lateral corticospinal tract (motor)

Answer 14

1. Motor commands send down from motor cortex
2. Cross after medulla
3. And travel to spinal cord to synapse on motor and interneurons

Question 15

Very shortened version of motor neural pathway- lateral corticospinal tract

Answer 15

Cortex - medulla - spinal cord- signal to skeletal muscle(s)

Question 16

Lateral vestibulospinal tract (motor)

Answer 16

1. Motor output sent down from lateral vestibular nuclei
2. To medulla
3. Travels without crossing to spinal cord
4. Synapses on motor and interneurons

Question 17

Shortened version of motor neural pathway - lateral vestibulospinal tract

Answer 17

Brainstem- lateral vestibular nucleus - medulla - spinal cord - signal to skeletal muscle(s)

Question 18

What are extrapyrimidal tracts

Answer 18

Brainstem pathways

Question 19

What do the fibers of the extrapyrimidal tracts not do

Answer 19

Cross to other side of body

Question 20

what are extrapyrimidal tracts involved in

Answer 20

Postural control and control of hand and finger flexion/extension

Question 21

What does the lateral vestibulospinal tract excite

Answer 21

Antigravity muscles to maintain extension and prevent collapse

Question 22

What happens when you spin around until feeling dizzy and then stagger around

Answer 22

Have experience over active lateral vestibulospinal tract

Question 23

2 ascending sensory tracts

Answer 23

Dorsal column tract
Posterior spinocerebellar tract

Question 24

Dorsal column tract (sensory)

Answer 24

Sensory info from proprioceptors and touch receptors
Sent to spinal cord
Crosses in medulla
Travels to somatosensory cortex via thalamus

Question 25

What are examples of sensory info from touch receptors

Answer 25

Touch
vibration
Two point discrimination

Question 26

Shortened version of sensory neural pathway - dorsal column tract

Answer 26

Signal from proprioceptors and touch receptors - spinal cord - medulla - thalamus - cortex

Question 27

Posterior spinocerebellar tract (sensory)

Answer 27

Sensory info from lower limb proprioceptors
Sent up spinal cord
Does not decussate in medulla
Travels to ipsilateral cerebellum

Question 28

Shortened version of sensory neural pathway - posterior spinocerebellar tract

Answer 28

Signal from proprioceptors - spinal cord - medulla - cerebellum

Question 29

Motor unit

Answer 29

An alpha motor neuron and all the skeletal/extrafusal muscle fibers it innervates

Question 30

Example of motor unit for fine movement

Answer 30

Eye muscles = 1 fiber/motor unti

Question 31

Example of motor unit for a gross movement

Answer 31

Postural control = up to 700 fibers/motor unti

Question 32

Amount of contractile force is directly related to what

Answer 32

Number of motor units activated

Question 33

Recruitment

Answer 33

Process of increasing number of motor units involved

Question 34

What does recruitment follow

Answer 34

Size principle

Question 35

What does size = in motor unit recruitment

Answer 35

Motor unit cell body diameter

Question 36

What is the size principle

Answer 36

Recruit smallest motor units first then systematically increase size of unit recruited until desired force is achieved

Question 37

3 parts of neural control of voluntary movement that determine motor control

Answer 37

1. Perception (detecting visual, auditory, tactile cues)
2. Cognition (reaction time, intent)
3. Emotion (fear of falling)

Question 38

Where is the intent located

Answer 38

Higher centers of the cortex

Question 39

Planning and organization of the required movement occurs where

Answer 39

The middle center of the brain including the sensorimotor cortex, diencephalon, cerebellum, and brainstem

Question 40

Execution of the movement plan involves

Answer 40

Brainstem, spinal cord, muscle fired and sensory receptors