✅Muscle Function

Question 1

What does the process of muscle contraction involve?

Answer 1

• Neural stimulation of sarcolemma
  – Causes excitation–contraction coupling
• Muscle fibre contraction
  – Interaction of thick and thin filaments
  • Tension (force) production

Question 2

What is essential for contraction?

Answer 2

ATP

Question 3

Where is the enzyme myofibrillar ATPase (mATPase) located?

Answer 3

In the myosin head.

Question 4

What is ATP also required for?

Answer 4

To pump calcium back into the SR during relaxation.

Question 5

Describe Slow fibres

Answer 5

• Type I fibres
– Slow-twitch fibres
– Slow-oxidative fibres
– Large amounts of mitochondria
– Myoglobin

Question 6

Describe Fast fibres

Answer 6

• Type IIb fibres
– Fast-twitch fibres
– Fast-glycolytic fibres
– Larger in diameter
• Type IIa fibres
– Intermediate fibres
– Fast-oxidative fibres
– Hybrid of type I & IIb

Question 7

What is muscle tone?

Answer 7

The resting tension in a muscle

Question 8

What are contractions classified based on?

Answer 8

Patterns of tension production

Question 9

What are the two types of contraction?

Answer 9

• Isotonic contraction

* Isometric contraction

Question 10

Describe isotonic contraction

Answer 10

• Skeletal muscle changes length
- Resulting in motion
• If muscle tension > load (resistance):
- Muscle shortens (concentric contraction)
• If muscle tension < load (resistance):
- Muscle lengthens (eccentric contraction)

Question 11

Describe isometric contraction

Answer 11

Skeletal muscle develops tension, but is prevented from changing length
iso- = same, metric = measure

Question 12

What are inversely related?

Answer 12

Load and speed of contraction

Question 13

What does the load (resistance) on a muscle affect?

Answer 13

The longer it takes for shortening to begin

The less the muscle will shorten

Question 14

What are the affects of types of number of motor units recruited?

Answer 14

– More motor units = greater force
– Fast motor units = greater force

Question 15

What is the affect of initial muscle length on force?

Answer 15

• Optimum overlap produces greatest amount of tension
• Nature of the motor unit neural stimulation

Question 16

What affect does the frequency of stimulation have?

Answer 16

-simple twitch, summation, and tetanus

Question 17

What is a single muscle twitch composed of?

Answer 17

Latent, contraction and relaxation periods.

Question 18

What are the two receptors in muscle?

Answer 18

Muscle Spindle

Golgi Tendon Organ

Question 19

What does a muscle spindle do?

Answer 19

– Detect dynamic and static changes in muscle length

– Stretch reflex
– Stretch on muscle causes reflex contraction

Question 20

What does a golgi tendon organ do?

Answer 20

-Monitor tension developed in muscle
– Prevents damage during excessive force generation
– Stimulation results in reflex relaxation of muscle

Question 21

When can a muscle no longer perform at the required level of activity?

Answer 21

– Depletion of metabolic reserves
– A decline in pH within the muscle fibre – lactic acid
– A sense of weariness due to low blood pH
– Damage to sarcolemma or sarcoplasmic reticulum
– Pathological conditions – premature fatigue – heart problems, blood loss etc

Question 22

What is anaerobic pathway?

Answer 22

Lactic acid

Question 23

Describe atrophy

Answer 23

• Results due to lack of activity or loss of neuronal innervation
• Reduction in muscle fibre size, tone and power
• Examples are sedentary life style, bed rest, spinal cord injury

Question 24

Describe hypertrophy

Answer 24

• Results due to repeated, exhaustive stimulation
• Muscle fibre increases in diameter
• Number of muscle fibre remains the same
• There is an increase in mitochondria, glycolytic enzymes, larger glycogen reserve