L28

Question 1

explain concenteric vs eccentric vs isometric contraction

Answer 1

-concentric- muscle contracts, flex up
-eccentric- muscle elongates, flex down
-isometric- muscle contracts, no movement

Question 2

what does tension dependent on

Answer 2

-muscle fibres crteate it cross bridge cycling, which shortens each sarcomere
-amount of tension depends on
- resting sarcomere length
-length-tension relationship
-frequency of action potentials
- intesity of stimulation

Question 3

explain the length-tension relationship

Answer 3

• refers to resting sarcomere length (when thick + thin filaments have slight overlap)
  -resting sarcomere legnth relates to how much tension produced WHEN muscle fibre contracts
  -too much or too little overlap leads to less-ideal tension (each too much overlap = less tension), this is due to
  -not enough overlap = less tension, less no. of cross bridges may form
  -too much overlap= less tension, less ability of sarcomeres to shorten during cross bridge cycling
  
  • ideal overlap,80-120% of resting length

Question 4

explain motor units

Answer 4

a motor unit = 1 alpha motor neuron + all muscle fibres it innervates
- all fibres within a motor unit have same threshold for activation + contract/relax together
- fine control = smaller motor units

Question 5

define muscle twitch

Answer 5

-contraction of a single motor unit, evoked by a single action potential
-3 periods
- latent period- following stimulation of the motor neuron
- contraction period- when cross bridges actively cycle, producing tension
-relaxation period- end of neural stimulation, Ca2+ returned to SR, cross bridges detach, active sites on actin covered by tropomyosin