L14: Drug effects on smooth muscle

Question 1

Where is smooth muscle found?

Answer 1

Walls of the hollow organs of the body involved in the transport of gases, liquids & solids

Question 2

What is smooth muscle controlled by?

Answer 2

Autonomic nervous system by hormones

Question 3

What is contraction regulated by?

Answer 3

Myosin-light chain phosphorylation

Question 4

What is smooth muscle cell composed of?

Answer 4

Actin+myosin filaments
Adherens junction
Gap Junction
Sarcoplasmic reticulum (release & reaccumulates Ca2+)

Question 5

Regulation of smooth muscle contraction

Answer 5

1) Myosin light chain undergoes phosphorylation, detaching from actin filaments

2) Ca2+-calmodulin complex activates MLCK

3) Myosin binds to actin

Question 6

How is smooth muscle contraction relaxed?

Answer 6

Myosin light chain phosphatase reverse phosphorylation which causes relaxation

Question 7

What is the inhibition of MLCP called and what does it promote?

Answer 7

Calcium Sensitisation
- Promotes contraction

Question 8

What is the activation of MLCP called and what does it promote?

Answer 8

Calcium Desensitisation
- Promote relaxation

Question 9

What protein does Ca bind to in smooth muscle to initiate contraction?

Answer 9

Calmodulin

Question 10

What enzyme removes the phosphate group?

Answer 10

Myosin phosphotase

Question 11

What does vascular tone determine?

Answer 11

Contraction & releaxion of vascular smooth muscle

Question 12

5 classes of hypertension drugs

Answer 12

1) alpha1-adrenoceptor antagonists
2) beta1-adrenoceptor antagonist
3) Ca2+ channel blockers
4) Diuretics
5) Drugs inhibiting RAAS

Question 13

Function of RAAS

Answer 13

Maintenance of blood pressure via hormones in circulation

Question 14

What is the endothelium derived relaxing factor?

Answer 14

Nitric Oxide

Question 15

What is Nitric Oxide released by and in response to?

Answer 15

Released by endothelial cells in response to stimuli

Question 16

What do endothelial cells lining blood vessels release?

Answer 16

Substance that relaxes neighbouring vascular smooth muscle cells- cause vasodilation

Question 17

2 drugs acting on the NO pathway

Answer 17

1) Nitrovasodilator drugs
2) PDE-5 inhibitors

Question 18

How do nitrovasodilator drugs mimic/enhance actions of NO?

Answer 18

Decompose in blood plasma to release NO
- Treat angina

Question 19

How does PDE-5 inhibitors mimic/enhance the actions of NO?

Answer 19

Stop breakdown of cGMP
- Used for erectile dysfunction & pulmonary hypertension

Question 20

What cells is NO released from in blood vessels?

Answer 20

Endothelial cells

Question 21

Name of enzyme activated by NO in smooth muscle cells & what is its product?

Answer 21

GC (Guanylyl Cyclase)
Product: GTP to cGMP

Question 22

What enzyme converts angiotensin I to angiotensin II?

Answer 22

Angiotensin-converting enzyme (ACE)

Question 23

What does RAAS do?

Answer 23

Regulates arterial pressure through angiotensin II & aldosterone

Question 24

Where is renin released from?

Answer 24

Juxtaglomerular cells of the kidney

Question 25

Where is ACE found?

Answer 25

Surface of vascular endothelial cells, lungs

Question 26

Where is aldosterone released from?

Answer 26

Adrenal cortex (cells in the outer layer of the adrenal gland)

Question 28

Function of ACE

Answer 28

- Converts angiotensin I to angiotensin II - Inactivates vasodilator, bradykinin