Motor System

Question 1

What proteins create contraction of muscles?

Answer 1

Actin, myosin, troponin, tropomyosin

Question 2

What is the functional unit of muscles?

Answer 2

Sarcomere

Question 3

What are the three structural proteins?

Answer 3

M-line, Titian, Z-line (ends)

Question 4

T/F myosin heads bind with actin filaments

Answer 4

True

Question 5

What is the name of the model that shortens (contracts) muscles?

Answer 5

Sliding filament model

Question 6

What is the sliding filament model?

Answer 6

Muscle shortens/lengthens by actin and myosin filaments sliding past each other without changing length

Question 7

The attachment, rotation, and detachment of filaments utilize energy from what source?

Answer 7

ATP hydrolysis

Question 8

Which bands get narrower as shortening continues?

Answer 8

I and H bands

Question 9

What is another name for muscle membrane?

Answer 9

Sarcolemma

Question 10

What are the projections that extend into the muscles that allow for depolarization within the muscle?

Answer 10

T-tubules

Question 11

Depolarization within the muscles release Ca2+ from what?

Answer 11

Sarcoplasmic reticulum (Ca2+ sacs)

Question 12

What is the inhibition complex that covers the binding site on actin filaments?

Answer 12

Troponin-tropomyosin complex

Question 13

What causes the movement of the troponin-tropomyosin complex to expose the binding site?

Answer 13

Ca2+

Question 14

To where do UMN tracts deliver signals to?

Answer 14

Spinal interneurons and LMNs

Question 15

Where are the cell bodies of LMNs located?

Answer 15

In brainstem and ventral horn of spinal cord

Question 16

What is called the “final common path” by Sir Charles Sherrington?

Answer 16

LMNs

Question 17

Which motor neuron tract is essential for INITIATING movement?

Answer 17

UMNs

Question 18

T/F UMNs rarely synapse with interneurons before synapsing with LMNs

Answer 18

False (most of them do)

Question 19

What does a motor unit consist of?

Answer 19

LMN and the specific muscle fiber it innervates

Question 20

T/F a single motor unit will innervate only one specific muscle fiber TYPE

Answer 20

True

Question 21

What are the three classifications of motor unit characteristics?

Answer 21

1. Twitch (speed)
2. Tension (force)
3. Fatigability (endurance)`

Question 22

Which type of twitch is very fatigue resistant?

Answer 22

Slow twitch (Type 1)

Question 23

Which type of exercise uses Type IIb motor units?

Answer 23

Plyometric exercises (fast twitch and v high force)

Question 24

What generates force gradation and changes in tension?

Answer 24

Motor unit RECRUITMENT strategies

Question 25

What are the two mechanisms that determine gradation of force?

Answer 25

1. Increased # (recruitment, more motor units) | 2. Increased frequency of motor unit discharge (repetitive stimuli = temporal summation)

Question 26

What principle states that orderly recruitment produces smooth muscle actions (fine tuning)

Answer 26

Henneman’s Size Principle

Question 27

T/F motor units fire all at once

Answer 27

False (different times, different intensities)

Question 28

What are the three types of temporal summation in motor units?

Answer 28

1. Wave summation (2nd stimulus occurs before complete relaxation) 2. Unfused tetanus 3. fused tetanus

Question 29

What term refers to motor unit firing rate?

Answer 29

Rate coding

Question 30

What does “recruitment strategy varies by size” mean?

Answer 30

Smaller muscles rely on rate coding / larger muscles rely on recruitment

Question 31

What is the brief contraction of all muscle fibers in a motor unit in response to a single nerve impulse?

Answer 31

Twitch contraction

Question 32

What is the record of muscle contraction called?

Answer 32

A Morgan

Question 33

What is a recording of electrical muscle activity?

Answer 33

Electromyography (EMG)

Question 34

Which type of motor neurons convey signals to extra/intrafusal skeletal muscle?

Answer 34

LMNs

Question 35

What are the two types of LMNs?

Answer 35

Alpha motor neurons (large, extrafusal) and gamma motor neurons (medium, intrafusal)

Question 36

What are groups of muscles innervated by a single spinal nerve?

Answer 36

Myotomes

Question 37

What are groups of cell bodies whose axons project to a single muscle?

Answer 37

LMN pool

Question 38

LMN pools are correlated to what four anatomical positions?

Answer 38

Medial (axial and proximal muscles) Lateral (distal muscles) Anterior (extensors) Posterior (flexors)

Question 39

What spinal cord function inhibits antagonist muscles during agonist contraction?

Answer 39

Reciprocal inhibition (prevents stretch reflex)

Question 40

What do you call the spinal cord’s creation of a complete proprioceptive model of the body in real time?

Answer 40

Proprioceptive body schema

Question 41

Which stretch reflex responds to quick stretch?

Answer 41

Phasic stretch reflex (deep tendon reflex)

Question 42

T/F the phasic stretch reflex arc is di-synaptic

Answer 42

False (monosynaptic)

Question 43

During stretch reflexes, what detects the quick muscle stretch?

Answer 43

Muscle spindles

Question 44

What reflex involves a painful stimulus detected by a nociceptor?

Answer 44

Withdrawal reflex (flexion reflex)

Question 45

What does a withdrawal reflex result in?

Answer 45

1. Activation of flexor and inhibition of extensor | 2. Movement of body away from painful stimulus

Question 46

T/F the withdrawal reflex arc is polysnaptic

Answer 46

True

Question 47

What reflex is activated simultaneously with a withdrawal reflex?

Answer 47

Crossed extension reflex

Question 48

What does a crossed extension reflex result in?

Answer 48

1. Contralateral activation of extensor and inhibition of flexor 2. Weight support for contralateral limb