Chapter 4: Muscle Physiology

Question 1

What is the muscle fibre structure? (6)

Answer 1

1) Tendon Sheath
2) Epimysium
3) Muscle Belly
4) Fasciculi
5) Muscle Fiber

Question 2

Tendon Sheath

Answer 2

The bundle of epimysium extended beyond the muscle, which attaches the muscle to the periosteum of the bone.

Question 3

Epimysium

Answer 3

Connective tissue that wraps around the muscle.

Question 4

Muscle Belly

Answer 4

The main bulk of the muscle.

Question 5

Fasciculi

Answer 5

Smaller bundle of muscle fibres containing strands of muscle cells and wrapped in perimysium (similar to epimysium).

Question 6

Muscle Fiber

Answer 6

Made up of Myofibrils which run along the whole fibre and contain the contractile components (Myofilaments) called Sacromeres.

Question 7

Sarcomeres

Answer 7

Functional and main contractile unit of the muscle fibre; consists of Z disc, Actin and Myosin.

Question 8

Actin

Answer 8

Double helix structure containing Tropomyosin and Troponin protein which inhibits myosin from sliding over it unless Ca+ releases as a signal from the motor neuron.

Question 9

Myosin

Answer 9

Thick filament with cross-bridges globular heads that slides over Actin which allows the shortening of the sarcomere.

Question 10

Power Stroke (3)

Answer 10

Contraction of a sarcomere; consumes ATP to produce force during contraction.
- Contracts down to 50% of the original length.
- Stays at rest in the absence of an electrical signal.

Question 11

Sensory Neurons

Answer 11

Carries info about changes in body positions, load, etc., to CNS (spinal column + brain).
- RNS (neurons outside of CNS)

Question 12

Motor Neurons

Answer 12

Carries electrical stimulation to the muscle causing it to contract.

Question 13

Neuromuscular Junction

Answer 13

The connection between the motor neuron and the individual muscle fibre.

Question 14

All or None Principle

Answer 14

Muscle fibres will contract to their max potential or not at all within their motor unit.

Question 15

Muscle FIber Recruitment

Answer 15

The body will recruit more motor units/increase the frequency of nervous stimulation to accommodate the increased load.

Question 16

What are the 3 Types of Muscle Fibers (3)

Answer 16

1) Type 1: Slow oxidative twitch fibres
2) Type 2A: Oxidative Intermediate twitch fibres
3) Type 2B: Glycolytic fast twitch fibres

Question 17

Type 1: Slow Oxidative Twitch Fibres (3)

Answer 17

The higher oxidative capacity allows for high endurance and fatigue resistance suited for endurance sports.
- Able to metabolize ATP through aerobic processes, allowing it to contract for long periods.
-Thin fibres containing high amounts of mitochondria, myoglobin and much more capillarization.

Question 18

Type 2A: Oxidative Intermediate twitch fibres (2)

Answer 18

Capable of creating energy both with and without oxygen, thus be able to produce high force yet resistant to fatigue.
-Suited for sports like hockey.

Question 19

Type 2B: Glycolytic fast twitch fibres (3)

Answer 19

An anaerobic system produces fast and powerful contractions and releases lactic acid, which causes to muscle to fatigue quickly.
-Thick fibres containing lower amounts of mitochondria, myoglobin and much less capillarization.
-Suited for sports like sprinting or powerlifting.

Question 20

Characteristics and distribution of muscle fibres.

Answer 20

We all have 45-65% slow twitch muscles, and our ratio becomes established around two years old.
We tend to lose more fast twitch muscle as we age.
They can train to maximize their potential but cannot switch to other types.
Fibre distribution is different in different muscle groups.