Muscle [Smooth]

Question 1

How is smooth muscle innervated?

Answer 1

Autonomic NS who’s nerves form varicosities with diffuse junctions. They release neurotransmitters into target cells.

Question 2

Response to stretch

Answer 2

Resists at first by contracting then relaxes once adapted

Question 3

Advantage of smooth muscle organisation

Answer 3

Poorly organised so shortening can take place without filaments colliding.

Question 4

Single unit vs multi-unit

Answer 4

Single: electrically coupled, blood vessels and organs.
Multi: innervated by nerves to contract. Vas deferens or iris

Question 5

2 layers of arrangement in hollow organs

Answer 5

Longitudinal: mush food
Circular: moves food down

Question 6

What do smooth muscles have instead of t tubules and what do they do?

Answer 6

Caveolae which increase surface area

Question 7

Why do smooth muscle cells contract automatically if stretched?

Answer 7

Stretch activated ion channels for Ca2+. Relax by calcium dependent K+ channels

Question 8

How does Ca2+ enter the cell

Answer 8

Via channels or SR

Question 9

What happens after Ca2+ enters the cell? (4 steps)

Answer 9

Binds to calmodulin which activates MLCK which phosphorylates the myosin head which causes the cross bridge to begin.

Question 10

Relaxation phase

Answer 10

MLCP dephosphorylates MLCK.

Ca-ATPase removes Ca2+