Ca and muscle

Question 1

Fill in the table on relative ion concentrations at resting potential

Answer 1

Question 2

What role does Ca play in the neuromuscular synapse/junction?

Answer 2

Question 3

How do catecholamines increase cardiac contractility?

Answer 3

Increase cardiac muscle fibre membrane permeability to Ca => increased contractility

Question 4

Why is cardiac muscle more susceptible to change in Ca conc than skeletal muscle?

Answer 4

Skeletal muscle:
- T tubules have closed ends
- Ca ions released from SR within fibre
Cardiac:
- T tubules open directly to outside of fibre
- allows ECF to enter T tubules
- availability of Ca ions to cardiac muscle is dependent on ECF Ca cone

Question 5

how can low Ca levels cause eclampsia?

Answer 5

Permeability changes to Ca and Na channels => increased influx of Na into cells changes resting potential => cell becomes more easily excitable => depolarisation and impulse generation => repeated stimulation of skeletal muscle => tetanic muscle contraction