skeletal muscle energetics

Question 1

give the definition of a muscle doing work (equation)

Answer 1

work = force x distance

Question 2

work = force x distance

expand on what this means by ‘distance’, and how this links to what is classed as a muscle doing work:

Answer 2

distance = change in length of muscle that occurs to produce force

SO

a muscle is only doing work when there is a change in length

Question 3

define isometric contraction + e.g.

Answer 3

generating force without fibres shortening

e.g. maintaining body posture

Question 4

define isoTONIC contraction + e.g.

Answer 4

activated muscles change in length(?) as they develop force, sarcomeres shorten/lengthen (?)

e.g. limb movement

Question 5

give 2 types of isoTONIC contraction:

Answer 5

• concentric
• eccentric

Question 6

(isoTONIC contraction)

define CONCENTRIC contraction

Answer 6

muscle SHORTENS whilst doing work

e.g. bicep curl

Question 7

(isoTONIC contraction)

define ECCENTRIC contraction

Answer 7

muscle LENGTHENS whilst doing work

e.g. braking down steep slope

Question 8

define TETANIC contraction:

Answer 8

series of APs in rapid succession (motor neurone)

= persistent contraction of muscle fibres

(= sustained and constant contractile force)

Question 9

in what situation does a incomplete tetanic contraction occur?

Answer 9

when the interval between APs is shorter than the duration of a single twitch

Question 10

define pathological tetanic contraction - use example of tetanus

Answer 10

tetanic contraction caused by disease(?)

tetanus bacteria produce toxins which stimulates many APs along motor neurone in quick succession

= hyperactivity in voluntary muscles
[rigidity (tonic involuntary contractions) and spasming (shorter lasting with stretching of muscle] ???????

Question 11

explain the relationship between contractile force and sarcomere length (check and write answer properly as this is an LO)

Answer 11

contractile force = sarcomeres shorten (in all contractions excl eccentric - would lengthen?)

Question 12

When exercising an animal, why is it important to make sure the muscle length never deviates much from the optimal length?

Answer 12

If the sarcomere (muscle) is stretched to the point where the thick and thin filaments do not overlap at all, no cross-bridges can be formed, and no tension is generated.

Question 13

muscle power output is what ?

Answer 13

work per unit of time

Question 14

muscle power output (work per unit of time) is product of…?

Answer 14

velocity of muscle shortening

external load

Question 15

anki: explain the shape of this graph: the inverted ‘U’ shape (for external load against muscle power output graph)