Muscle contraction

Question 1

what is tension

Answer 1

the force that a muscle exerts on the joint when it is contracting

Question 2

what is load

Answer 2

force exerted on a muscle by an object

Question 3

what is a twitch

Answer 3

the mechanical response of a muscle fibre to a single action potential

Question 4

what effect does increasing load have on concentric contraction?

Answer 4

increased latent period
decreased velocity of shortening
decreased duration of twitch
shortened distance

Question 5

which muscle fibres have the largest shortening velocity

Answer 5

type II

Question 6

when is a contraction tetanus

Answer 6

when successive stimulations result in a sustained contraction

Question 7

what is the length tension relationship

Answer 7

when muscles are almost fully shortened, amount of tension generated is low due to sarcomeres overlapping
at optimum level of stretch, large amount of tension can be produced
when muscle is very long, actin and myosin are too far apart so force produced is low

Question 8

what does contraction speed depend on

Answer 8

rate of cross-bridge cycling

Question 9

what are the mechanisms of muscle fatigue?

Answer 9

1. conduction failure- caused by potassium accumulation in t-tubules
2. lactic acid build up- acidic environment affects proteins and mechanisms involved
3. inhibition of cross-bridge cycling- accumulation of ADP and Pi prevents release of cross-bridges
4. fuel substrates- muscle glycogen, blood glucose, dehydration
5. central command fatigue- failure to propagate signals from brain to Moto neurones

Question 10

how can fibre type be determined?

Answer 10

colour of fibre (type I usually more red)
fibre speed and oxidative capacity
myosin heavy chain isoform
genomic nomenclature