Muscle: skeletal muscle 2

Question 1

length tension relationship

Answer 1

during an isometric contraction, the maximum active force (tension developed) at the sarcomere is dependent on the overlap of actin and myosin

Question 2

excitation contraction coupling

Answer 2

1. ACh released into neuro-muscular junction
2. activation of ACH receptors
3. a muscle action potential is triggered
4. calcium is released from SR
5. Ca binds with troponin -> Crossbridge cycle
6. Ca levels fall and contraction ends

Question 3

muscle metabolism

Answer 3

sources of ATP
1. creatine phosphate - (ATP + creatine stores energy which is then given back as ATP when reacting with ADP, when needed immediately - 15s)
2. anaerobic glycolysis - breakdown of glucose (energy for 2min)
3. aerobic metabolism - mitochondira, energy for several minutes to hours

Question 4

passive force

Answer 4

increases as the muscle is stretched due to passive elements

Question 5

active force

Answer 5

developed via cross-bridge cycling: dependent on actin-myosin overlap

Question 6

motor unit

Answer 6

a motor neuron and all the muscle fibres it connects to and sends signal to
one nerve per muscle fibre but a nerve can connect to multiple fibres

Question 7

type 1 motor unit

Answer 7

slow twitch - slow efficient aerobic cells for mosture and walking

Question 8

type 2 motor unit

Answer 8

fast twitch - large fibres that fatigue rapidly but develop large forces for jumping or weight lifting

Question 9

regulation of force

Answer 9

dependent on
1) rate of stimulation of individual motor units
- single stimulus, contraction and relaxation
- another stimulus before fully relaxed, more tension results
- high frequency of stimuli, no relaxation between, high tension
2) the number of motor units recruited
- greater stimulation means more units recruited gives more tension, where smaller more fatigue resistant units are recruited first