Skeletal Muscle

Question 1

Excitation-contraction

Answer 1

1. Nerve a.p.
2. Ach secretion by nerve ending
3. End-plate potential
4. Muscle a.p.
5. Depolarise T-tubules + open Ca2+ channels of R
6. Increase sarcoplasmic Ca2+
7. Contraction
8. Ca2+ pumped into S.R.
9. Relaxation

Question 2

In contraction:

Answer 2

• Length of actin and myosin doesn’t change
• H- zone and I-band decrease in length
• distance between z-discs and M-lines decrease

Question 3

Contractile response pattern

Answer 3

Latent, lag, contract, relax

Question 4

Stimulation frequency is dependant on

Answer 4

Wave summation + fused tetanus leading to strong contractile response

Question 5

Isometric

Answer 5

Muscle length constant but generates force for tension

Question 6

Isotonic

Answer 6

Force steady but length of muscle changes

Question 7

Types of isotonic contraction

Answer 7

1. Concentric - muscle tension rises to meet resistance then remains the same as muscle shortens
2. Eccentric- muscle lengthens due to resistance being greater than force being produced

Question 8

Force depends on

Answer 8

1. no. active motor units
2. cross-sectional area of muscle
3. freq. of stimulation
4. rate at which muscle shortens determined by force velocity conc.
5. Isometric tension developed depends on muscle length -> declines at longer length

Question 9

Slow muscles are

Answer 9

Slow oxidative (light)

Question 10

Fast muscles are

Answer 10

a. Fast oxidative (darkest)

b. Fast glycolytic (intermediate)

Question 11

In a force-velocity curve max power =

Answer 11

1/3 of max. velocity of shortening

Question 12

Power =

Answer 12

Force x velocity of contraction