Muscle contraction

Question 1

Differentiate between isotonic & isometric contraction

Answer 1

Isotonic:
Involve movement of load through range of motion
Concentric:
Muscle shortens as it contracts
e.g. bicep curl or tugging in dogs
Eccentric:
Muscle lengthens as it contracts
e.g. lowering weight during bicep curl or horse extending forelimbs to break down steep hill

Isometric:
Muscle generates force but doesn’t change length
Used to hold position, stabilise joint or build strength

Question 2

What is tetanic contraction

Answer 2

Muscle fibre stimulated with series of rapid impulses (muscle doesn’t relax completely)

Results in fused contraction that is stronger

e.g. maintaining posture, lifting heavy objects & walking

Question 3

Outline relationship between external load velocity of shortening & resulting power output

Answer 3

Low velocity:
At low velocity of shortening (external load heavy & muscle contracting slowly) force generated by muscle high but velocity low
Power output low

Intermediate:
Medium velocity & medium load = maximum power output

High velocity:
At high velocity of shortening (external load light & muscle contracting fast) force generated low but velocity high
Power output also low

Question 4

Explain relationship between contractile force & sarcomere length

Answer 4

At rest, sarcomeres at optimal length for generating force
As muscle is stretched, force generated by muscle decreases due to reduced overlap of actin & myosin (less cross bridges formed)
When muscle shortened, force generated also decreases as filaments can’t slide efficiently