Muscular contractions Flashcards
1
Q
Latent period
A
- Motor end-plate depolarisation
- Depolarisation (AP) transmitted down T tubules
- Ca2+ channels open in SR
- [Ca2+] in the sarcoplasm
- Ca2+ binds to troponin revealing myosin binding site on actin
2
Q
Contraction
A
- Myosin binds to actin, moves (powerstroke, ADP ejected), releases (new ATP binds) and reforms many times causing sarcomeres to shorten.
3
Q
Relaxation
A
- Ca2+ actively transported back into SR
- Troponin-tropomyosin complex blocks myosin binding
- Muscle fibre lengthens passively (relaxation)
4
Q
Motor unit
A
1 motor neuron & its muscle fibres
- One nerve with one nerve impulse
- Small contractions over whole muscle
5
Q
Multiple motor units
A
- Activation of more motor neurones
- More muscle fibres
- more contractile strength
Force dependant on number of motor units
6
Q
Threshold
A
If the threshold stimulus for a nerve is reached and the threshold for muscle contraction is reached, the muscle fibre will contract, otherwise it will not.
7
Q
Recruitment
A
- The greater the force of contraction needed, the more motor units are required
- Each motor unit operates in an all or none fashion
8
Q
Increase stimulus sensitvity
A
- Controls the force of contraction (in absence of internal changes, such as fatigue, fibres will contract ‘fully’ each time).
- The more motor units the bigger the twitch
9
Q
Order of tension
A
- Subthreashold
- Threshold
- Submaximal
- Maximal
- Supamaximal
10
Q
Lower frequency
A
Muscle fibres relax fully before next AP arrives
11
Q
Low frequency and contractile force
A
- Muscle fibres relax fully before next AP arrives
- Twitches (tension returns to baseline – not shown)
- Before next AP can occour fibres must fully relax
12
Q
High frequency contractile force
A
- No time for the muscle fibres to relax before the next AP arrives
- Continual exposure to Ca2+ maximal contraction Tetanus
13
Q
ATP need in contraction
A
- Contraction (crossbridge forming and release),
- Relaxation ( pump Ca2+)
- Restore Na+ and K+ levels afer AP
14
Q
Sorces of ATP for muscles
A
- Phosphocreatine - A source of ATP
- Carbohydrates
- Aerobic metabolism : producing about 30
ATP for each molecule of glucose - Anaerobic glycolysis : glucose is metabolized to lactate/lactic acid with a yield of only 2 ATP per glucose
15
Q
Slow twitch oxidative red muscle
A
- Smallest with slow contraction and ATP breakdown
- Fatigue resistant and high aerobic metabolism
- High myoglobin and mitochondria
16
Q
Fast-twitch oxidative red muscle
A
- Medium size fast contraction time and breakdown of ATP
- Fatigue resistant and high anaeobic respiration
17
Q
Fast-twitch white muscle
A
- Large very fast muscle contraction with fast breakdown of ATP
- Easily fatigued and highest anaerobic respiration rate
18
Q
Slow-twitch muscle activation
A
- Only neurones with low threshold minimal force one neurone so lasts longer
