Cardiovascular Homeostasis

Question 1

Cardiac function curve linking MRAP with CO and VR

As MRAP increases, CO _____. Flattens at about __mmHg. (Starlings law)

As MRAP increases, VR ____ (as VR is influenced by pressure difference between ____ and ____).
When MRAP = 7-10, ____ ____ ____ ____ where there is no flow
VR is ____ when pressure inside veins is about _____ pressure. Veins collapse, no further VR increase

Where lines cross is where body functions as CO=VR

Answer 1

As MRAP increases, CO increases. Flattens at about 10mmHg. (Starlings law)

As MRAP increases, VR decreases (as VR is influenced by pressure difference between veins and MRAP).
When MRAP = 7-10, mean systemic filling pressure where there is no flow
VR is flat when pressure inside veins is about intrathoracic pressure. Veins collapse, no further VR increase

Where lines cross is where body functions as CO=VR

Question 2

What were to happen to cardiac function curve if

1) transfusion/constrict venous blood vessels
2) increase inotropic state
3) combination

Answer 2

• VR increasing independently due to transfusion, or exercise meaning reduced TPR and SM activity increasing in veins increases the MRAP, larger MSFP, and can increase CO to a point where curve flattens
• cardiac state enhanced alone reduces the MRAP, and higher CO, can only be done to a point, where VR curve flattens
• combination of the two increases CO and VR with little change to MRAP

Question 3

MORE revision
When renin is secreted(converts angiotensinogen in liver)
A2 functions

Answer 3

Renin release: sympathetc drive, low pressure in afferent arteriole (low BP); low Na+ in macula densa

A2 effects: increase sympathetic activity; tubular Na+ absorption, through aldosterone release too water retention; arteriole vasoconstriction to increase BP; stimulate ADH and thirst

Question 4

Natriuretic peptides
when released
effect
two types

antagonise RAAS!

Answer 4

-released when cardiac distension, sympathetic stimulation; A2; endothelin
-Inhibit renin release and vasodilate. ;less renin means less ang2 and aldosterone, water excreted (diuresis) and sodium loss (natriuresis) leading to decreasing blood pressure
-ANP: atrial
BNP: brain type, released by ventricles, seen in heart failure

NEP breaks down these, inhibiting can prolong effects