Physiology

Question 1

what extrinsic mechanisms increase stroke volume

Answer 1

1. sympathetic system on heart
2. sympathetic system on venous return
3. skeletal muscle pump
4. thoracic pump
5. increased activity in the RAAS

Question 2

what are the molecular mechanisms by which the sympathetic system increases stroke volume

Answer 2

1. activation of beta 1 adrenergic receptors on the ventricles
2. increased cAMP
3. increase in PKA
4. phosphorylation of L type ca2+ channels allowing increased ca2+ entry
5. constriction of veins through the activation of alpha 1 adrenergic receptors
   - increases IP3 which leads to an increase in conc of Ca2+, leading to increase in Ca2+ calmodulin, activation of MLCK and phosphorylation of MLC which causes contraction of smooth muscle

Question 3

name 2 systems that can regulate total peripheral resistance

Answer 3

• sympathetic system

- RAAS

Question 4

describe the mechanism of action of the sympathetic system in regulating total peripheral resistance

Answer 4

1. either activates alpha 1 adrenergic receptors to cause an increase in TPR
2. or activates beta 2 adrenergic receptors to cause a decrease in TPR via an increase in cAMP, increase in PKA and phosphorylation of MLCK which inhibits its action so smooth muscle relax

Question 5

describe the mechanism of action of RAAS in regulating total peripheral resistance

Answer 5

1. RAAS increases TPR by the actions of AngII on AT1 receptors
   - increases IP3
   - increases intracellular Ca2+
   - increases ca2+ calmodulin
   - increases activation of MLCK
   - increases phosphorylation of MLC
   - increases smooth muscle contraction

Question 6

which hypertensive would be frontline treatment for a black person of African or Caribbean origin

Answer 6

calcium channel blocker

Question 7

which antihypertensive would be frontline treatment for a British Indian patient aged 45 years old with no other comorbidities

Answer 7

ACE inhibitors

Question 8

which antihypertensive would be frontline treatment for a patient aged 45 years old with hypertension and benign prostatic hypertrophy

Answer 8

alpha 1 antagonist

Question 9

why do ACE inhibitors cause a cough in about 20% of patients

Answer 9

they inhibit the breakdown of bradykinin which can then activate sensory nerves in the airways to cause the cough