Neuromuscular System and Exercise

Question 1

What is the neuromuscular system

Answer 1

the interaction between the nervous system and the muscles.

Question 2

What happens when there is a voluntary decision to move?

Answer 2

Efferent nerve impulses are sent

Question 3

What is the basic functional unit of movement?

Answer 3

Motor neuron

Question 4

What is in a motor unit?

Answer 4

Anterior motor neuron

Muscle fibers it innervates

Question 5

What is a motor neuron?

Answer 5

Efferent nerve and is relatively large in diameter
leads to neuromuscular junstion
Myelinated thus provides fast conductivity

Question 6

What is a motor units?

Answer 6

Includes the interface and muscle fiber
Site of acetylcholine release = change in NA2+ and K+ permeability
Initiating depolarization and contraction

Question 7

How can we study motor units?

Answer 7

1) Electromyography (surface and intramuscular)
- Quality and quantity of electrical activity
2) Muscle biopsy
- Removal and analysis of a small portion of muscle
- Directly measures fibers
3) Force/Power Output Device
- Measures force, power, torque, angular velocity
4) Other imaging devices

Question 8

What are the classifications of the 3 primary motor units?

Answer 8

Fast Fatiguable
-high force
-thickest
-fatigue
Fast fatigue resistance
-fast
-mod force
-thick
Slow twitch
-low force
-fatigue resistance

Question 9

What is the nerve to muscle fibre ratio definition?

Answer 9

A single motor neuron and the number of muscle fibres stimulated

Question 10

What is gross movement?

Answer 10

Muscles involved a higher muscle fiber to nerve ratio (gastroc 1:1776)

Question 11

What is precise movement?

Answer 11

Fine movements have a lower muscle fiber to nerve ratio

eye 10:1

Question 12

What is Hennman’s size principle?

Answer 12

Small neurons fire first

Need to be at or above 60% of MVC to recruit fast fatigue

Question 13

What motor units are recruited first?

Answer 13

slow motor units for both power and endurance movements

-Slow have a lower recruitment threshold (depolarize quicker)

Question 14

What accounts for force production during fast velocity exercise?

Answer 14

Fast fatigue and fast fatigue resistant

Question 15

What are the fiber type classification?

Answer 15

Type I (Slow)
Type IIa (FFR)
Type II b/x (FF)

Question 16

How are the muscle fibers classified?

Answer 16

By the myosin heavy chain(MHC)

Question 17

Within each MU type the fibers can vary, how?

Answer 17

In their properties and they co-express different proportions of MHC that can change with training.

Question 18

What are the four main points to distribution?

Answer 18

1) fiber type varies within multifunction muscles
2) Fiber type varies between different muscles
3) Variation of same muscle between two different people
4) Vary due to function of muscle

Question 19

What are skeletal muscle contraction types?

Answer 19

Isotonic = same tension (lifting weight)
Isokinetic = same velocity (cybex)
Isometric = same measure (no movement)

Question 20

What is a concentric action?

Answer 20

Shortening under tension

Question 21

What is an eccentric action?

Answer 21

lengthening under tension

Question 22

What is a static action?

Answer 22

tension within the muscle but no visible movement

Question 23

How does muscle muscle tension vary?

Answer 23

1) Muscle length
2) Joint angle
3) Velocity of movement
4) Percent of fast twitch fibers

Question 24

What is torque?

Answer 24

Work and torque are the same

It is a twisting force that tends to cause rotation

Question 25

What effects do muscle length have on tension?

Answer 25

Max tension occurs near resting length of the muscle because of max overlap of myosin and actin cross bridge

Question 26

What effects do joint angle have on tension?

Answer 26

Muscle tension is greatest some where in the middle of the ROM

Question 27

What effect does velocity of a movement have on tension?

Answer 27

Isometric produce the greatest tension
MU Recruitment Times:
-Isometric more time for recruitment
-Fast contraction less time

Question 28

What effect does the percent of fast twitch have on tension?

Answer 28

-Higher peak torque at most angular velocities with greater fast twitch fibers

Question 29

What are neural factors influencing muscle tension?

Answer 29

1) Conscious CNS drive (Increase/decrease tension)
2) Muscle spindle respond to stretch pf muscle to increase tension
3) Golgi tendon organ and some ligaments respond to tension and cause reflexes

Question 30

What is a muscle spindle?

Answer 30

Information about fiber length and tension.

Responds to stretch (counteracts stretch)

Question 31

What is the Golgi tendon organ?

Answer 31

Activated by excessive muscle tension

Responds by reflex inhibition of muscle

Question 32

Why does muscle force increase with increase in velocity

Answer 32

Greater CNS drive
Greater MU recruitment
Greater passive tension contribution from series and parallel elastic components

Question 33

Muscle power increases with…

Answer 33

increase in concentric movement velocity up to 50% max shortening velocity
After ~50% PO decreases

Question 34

Concentric peak torque is inversely related to

Answer 34

angular velocity

faster the movement less time for recruitment

Question 35

Muscles with greatest % of FF will have…

Answer 35

greatest power/strength output at any given velocity

Larger muscle fibers, faster MN conduction velocity, greater Ca2+ release