Skeletal muscle

Question 1

What is the epimysium?

Answer 1

Ensheathment of entire muscle

Question 2

What is the perimysium?

Answer 2

Ensheathment of muscle fibres into bundles

Question 3

What is the endomysium?

Answer 3

Areolar connective tissue that ensheaths each individual myocyte (separating muscle fibres). It also contains capillaries and nerves

Question 4

What are the three stages of myogenesis?

Answer 4

Determination
Myoblast proliferation/migration
Muscle differentiation

Question 5

What are the first signs of muscle commitment?

Answer 5

Appearance of AChRs all over sarcolemma

Formation of actin and myosin filaments, no sarcomeres

Question 6

what is myosin?

Answer 6

actin-dependent ATPase

Question 7

What is oxidative capacity?

Answer 7

Microlitres of oxygen consumed per gram of muscle per hour
- depends on capillary density, oxygen carrying capacity of blood (rbc count), myoglobin presence, amount of oxygen utilised (number of mitochondria present)

Question 8

What are 3 pathways for ATP regeneration?

Answer 8

1) direct phosphorylation of creatine kinase
2) anaerobic glycolysis
3) oxidative phosphorylation in mitochondria

Question 9

what is CrP level at rest?

Answer 9

~30mM

Question 10

What is EPOC?

Answer 10

excess post-exercise oxygen consumption

-> allows restoration of CrP, glycogen

Question 11

What are the 4 main tasks to complete post exercise?

Answer 11

Replenishment of ATP and phosphocreatine
Removal (oxidation) of lactic acid
Replenishment of myoglobin with oxygen
Replenishment of glycogen

Question 12

What is the structure of myosin?

Answer 12

Hexamer
2 identical heavy chains, 2 essential light chains, 2 regulatory light chains
globular head, 2 alpha helices forming super helical rod

Question 13

What are three theories of muscle fatigue?

Answer 13

1) Conduction Failure - due to the build-up of external K+ within T-tubules –> Action Potential (AP) failure
2) Lactic acid build-up associated with anaerobic glycolysis: when the rate of lactate production exceeds the rate of its disappearance –> acidification –> conformational changes in muscle proteins
3) Inhibition of X-bridge cycling due to the build-up of ADP and Pi

Question 14

Are muscle fibres of the same type located together?

Answer 14

A motor unit/all muscle fibres innervated by one motoneuron are of the same type
All muscles contain a mixture of fibre types

Question 15

How is tension varied in muscle?

Answer 15

orderly recruitment of motor neurons
The small motor units are most excitable and are recruited first. They develop low forces that can be maintained for long periods. The large motor units
are recruited later, after ~ 40% of the maximal tension in a whole muscle had been reached

Question 16

What are the effects of endurance training?

Answer 16

augmentation of oxidative mechanisms

increase in capillary density, more mitochondria

Question 17

What are the effects of strength training?

Answer 17

larger pale FG fibres

Question 18

What are the three stages of myogenesis?

Answer 18

myoblast determination
myoblast proliferation, migration
differentiation

Question 19

Which muscle types have high oxidative capacity?

Answer 19

Slow Oxidative Red (I) and Fast-Oxidative Glycolytic (IIA and IID)

Question 20

Which muscle types have high myosin ATPase activity?

Answer 20

Fast Oxidative glycolytic red (IIA, IID) and fast glycolytic white (IIB)

Question 21

What are the steps of muscle contraction?

Answer 21

1) muscle AP propagated
2) Ca released from lateral sac
3) Ca binds troponin, removes blocking action of tropomyosin
4) cross bridge moves
5) Ca taken up
6) Ca removal from troponin –> muscle relaxes

Question 22

Which process leads to lactic acid build up?

Answer 22

glycolysis

Question 23

How can fatty acids be utilised to produce ATP?

Answer 23

oxidative phosphorylation