End of muscle

Question 1

What is the effect of strength straining?

Answer 1

more actin and myosin which increases the fibre diameter

this means there can be more actin and myosin interactions to generate more force

Question 2

What is it called when the fibre diameter increases like during strength training?

Answer 2

hypertrophy

Question 3

What is the effect of endurance training?

Answer 3

increased oxidative capacity including
- more mitochondria
- more capillaries
- more myoglobin
- increased muscle stores of lipids
- increased ability to use lipids directly from the blood
this allows increased ability for sustained activity

Question 4

Isotonic contraction

Answer 4

force constant, length changes

Question 5

isometric contraction

Answer 5

length constant, force changes

Question 6

Length tension relatinoship

Answer 6

as length increases, contraction force increases because there is no blocking of actin and myosin until it reaches its resting length and then as length increases further, force decreases because the actin and myosin are not overlapping and so no cross bridges can form

Question 7

Load-velocity relatioship

Answer 7

Maximum cycling rate at no load, as load increases, velocity decreases until you can’t lift, you can only hold, exceeding this point means that you can’t lift, there is increasing velocity in lengthening the muscle

Question 8

Nervous system regulates muscle force by controlling the activity in what?

Answer 8

motor units

Question 9

What are 4 properties of the motor units?

Answer 9

• all muscle fibres in one unit are the same metabolic type
• motor unit size varies from small to large
• all fibres in one unit are active at once, so maximum force from a unit depends on size
• the size of a motor neuron cell body depends on the number of muscle fibres in the motor unit

Question 10

What two things is muscle force regulated by?

Answer 10

• changing the rate of activity in each unit (rate modulation)
• changing the number of units active (recruitment)

Question 11

Describe the rate modulation theory

Answer 11

As you increase the rate of stimuli, the initial twitch expends energy stretching the muscle and later ones work on the pre-stretched muscle so contribute more force to the tendon. At high rates though , SERCA can not clear Ca2+ between twitches so there is no chance for any relaxation and maximum force is transmitted to the tendon, continuously

Question 12

Describe the recruitment of motor units theory

Answer 12

motor units are recruited in order from smallest to largest; smaller motor units are more tonically active to give fine graded control of small forces, larger motor units automatically recruited as required force increases