Lecture 5:Reflexes and muscle contraction

Question 1

what cells to skeletal muscles have?

Answer 1

myocytes

Question 2

what is skeletal muscles formed from?

Answer 2

skeletal muscle fibres

Question 3

what does stimulation of muscle fibre in the skeletal muscle do?

Answer 3

excitation the entire cell

Question 4

where do motor neurones form synapses?

Answer 4

on the skeletal muscle fibres at the motor endplates

Question 5

what are slow muscle fibres?

Answer 5

postural muscles, mainly type 1 fibres

Question 6

what are fast muscle fibres?

Answer 6

mainly type 2 fibres, better suited to generate large forces but can fatigue rapidly

Question 7

how do you see the different types of fibres?

Answer 7

immunostaining

Question 8

what are isotonic contractions?

Answer 8

when muscle shortens on contraction against a constant load e.g. flexing a limb

Question 9

what are isometric contractions?

Answer 9

muscle constrained to a constant length e.g. holding heavy object still

Question 10

How does muscle fibre contraction happen ?

Answer 10

1. Nerve AP
2. Nerve ending secretes ACh
3. End plate potential
4. muscle action potential
5. T tubules depolarise
6. opens Ca2+ channels of sarcoplasmic reticulum
7. sarcoplasm Ca2+ increases
8. muscle fibre contracts
9. Ca2+ goes back
10. muscle fibre relaxes

Question 11

what happens in Excitation-contraction coupling?

Answer 11

AP from motor endplate, goes to T tubules, leading to SR, AP stimulates ion channels, releasing calcium, into the cytosol, myosin binds to actin( protein in thick filament). Contraction continues if Ca high and ATP present.