Lecture 2 - Introduction & CV Homeostasis

Question 1

Active control process?

Answer 1

set point is affected by error, which acts on an effector acting on a process, altered output as a result of changed process is picked up by sensor, which acts to minimise error signal and try to restore set point

Question 2

Equilibrium of closed systems?

Answer 2

operating point: usually where venous return = cardiac output; venous return ceases when MRAP equals mean systemic filling pressure; MRAP reduction will restore venous return, when MRAP equals extravascular pressure veins collapse and plateau venous return

Question 3

Situation of increased venous return?

Answer 3

transfusion

Question 4

Situation of increased cardiac output?

Answer 4

increased afterload - the pressure heart works at to eject in systole

Question 5

Distribution of Cardiac Output in Exercise?

Answer 5

NB that volumes are constant or vastly increase, but percentages change: brain, GI, spleen kidneys, skeleton and fat decrease, muscle and skin increase drastically

Question 6

Renin-angiotensin-aldosterone System?

Answer 6

renal macula densa cells release renin, this catalyses Angitotensinogen -> Angiotensin I, which -> Angiotensin II (catalysed by pulmonary and renal ACE) which acts on adrenal gland cortex to release aldosterone and posterior pituitary to release ADH

Question 7

Functions of RAAS system?

Answer 7

increased sympathetic activity, tubular Na and Cl reabsorption, K excretion, H2O retention @ tubules and absorption at collecting duct, vasoconstriction and increased BPq

Question 8

Stimuli of natriuretic peptide release?

Answer 8

cardiac distension, sypmathetic, angiotensin II, endothelin

Question 9

Natriuretic peptides?

Answer 9

vasodilation, decreased Renin, Ang II and Aldo, increased GFR causing natriuresis & diuresis (and renin decrease) decreasing blood volume and pressure

Question 10

Enzyme degrading natriuretic peptides?

Answer 10

neutral endopeptidase (NEP)

Question 11

Final result of natriuretic peptide action?

Answer 11

decreased blood volume, pressure (a and v), pulmonary capillary wedge pressure, and cardiac output