Lecture 6 (RAAS and Hemodynamics)

Question 1

Function of Renin:

Answer 1

necessary for angiotensin II synthesis

Question 2

Function of Angiotensin II:

Answer 2

• vasoconstrictor
• stimulates aldosterone secretion from adrenal cortex

Question 3

Function of Aldosterone:

Answer 3

• promotes Na+ conservation by kidneys; H2O follows Na+
• increases intravascular volume
• vasoconstrictor

Question 4

All angiotensin II bioactivity in vascular smooth muscle and cardiac muscle is mediated by what receptor?

Answer 4

AT1

Question 5

Actions of angiotensin II that lead to increased blood pressure (4):

Answer 5

1. vasoconstriction
2. block in high pressure baroreceptor activity
3. increased aldosterone levels
4. stimulation of norepi release from post-ganglionic SNS fibers

Question 6

Angiotensin II can block high pressure baroreceptor input. How does this cause an increase in BP?

Answer 6

• endogenous counter-response to elevated BP is neutralized.
• SNS not shut off in response to elevated BP.
• SNS has free-reign to maintain increased BP.

Question 7

Where are receptors for RAAS (angiotensin II and aldosterone) located?

Answer 7

1. myocardium
2. vascular smooth muscle
3. kidney

Question 8

Effect of RAAS (aldosterone and angiotensin II) on the heart:

Answer 8

• contributes to left ventricular hypertrophy
• increased wall stress and oxygen demand
• reduced ejection fraction

Question 9

Effect of RAAS (aldosterone and angiotensin II) on vascular smooth muscle:

Answer 9

• leads to tunica intima and tunica media thickening
• can cause vascular stenosis

Question 10

Effect of RAAS (aldosterone and angiotensin II) on the kidney:

Answer 10

• impairs normal renal function
• can lead to renal failure.

Question 11

Treatments for hypertension:

Answer 11

1. ACE inhibitors (angiotensin II)
2. ARBs (AT1 receptors)
3. Diuretics (aldosterone)
4. Calcium channel blockers (amlodipine)
5. beta-blockers (SNS)

Question 12

Function of verapamil and cardizem:

Answer 12

• blocks Type L calcium channels in the heart.
• help reduce heart rate by increasing AV nodal delay.

Question 13

Function of amlodipine:

Answer 13

• blocks Type L calcium channels in vascular smooth muscle.
• prevents vasoconstriction.

Question 14

Primary hypertension:

Answer 14

• hypertension due to an unknown cause.
• treatable with general hypertension protocol.
• ACE inhibitors, ARBs, calcium channel blockers, etc.

Question 15

Secondary hypertension:

Answer 15

• hypertension due to another medical condition.
• not treatable with general hypertension protocol.

Question 16

How, specifically, does using a beta-blocker decrease blood pressure?

Answer 16

• beta-blockers block SNS effects on the heart.
• decrease HR and inotropy, and therefore CO.
• CO = SV x HR.
• MAP = CO X TPR.

Question 17

General primary hypertension treatment protocol:

Answer 17

• First:
  
  • thiazide diuretic
• Second:
  
  • thiazide diuretic + ACE inhibitor/ARB
• Third:
  
  • thiazide diuretic + ACE inhibitor/ARB + Ca2+ channel antagonist

Question 18

The four body systems involved in hypertension, and drugs that target their function:

Answer 18

• cardiac
  
  • calcium channel blockers, beta-blockers
• renal
  
  • diuretics, ACE inhibitors, ARBs
• vascular smooth muscle
  
  • calcium channel blockers, ACE inhibitors, ARBs, alpha-1 receptor blockers
• ANS
  
  • beta-blockers

Question 19

Blood vessels with the highest velocity and lowest velocity of flow:

Answer 19

• highest velocity: aorta
• lowest velocity: capillaries

Question 20

Blood vessels with the highest and lowest total cross-sectional area:

Answer 20

• highest: capillaries
• lowest: aorta

Question 21

Blood vessels with the highest and lowest transmural (wall) pressure:

Answer 21

• highest: aorta
• lowest: vena cava

Question 22

Total peripheral resistance equation:

Answer 22

• TPR = (Pa - Pv)/Qt.
  
  • Qt = cardiac output (CO = SV x HR).
• Pa - Pv = CO x R

Question 23

60% of total peripheral resistance is due to:

Answer 23

• arteriolar resistance
  
  • Arterioles can undergo 4x changes in lumen diameter, which leads to up to a 256x change in conductance.

Question 24

Which blood vessel has the greatest influence over total peripheral resistance?

Answer 24

arterioles

Question 25

Peak arterial pressure occurs at:

Answer 25

* the end of decreased/slow systolic ejection phase, which is the end of the T wave.

Question 26

Lowest arterial pressure occurs at:

Answer 26

* the end of isovolumetric contraction. * immediately before the aortic valve opens

Question 27

Draw ECG with arterial pressure graph underneath:

Answer 27

Question 28

Where does systolic pressure normalize with diastolic pressure?

Answer 28

* right before entering the capillaries after traveling through the arterioles.

Question 29

How do arterioles maintain a relatively constant capillary pressure?

Answer 29

* **by adjusting resistance to flow with precapillary sphincters.** * **ΔP = Q x R** * flow (Q) and capillary pressure remain relatively constant, so arterioles adjust arterial pressure going into capillaries via resistance.

Question 30

The four Starling forces governing capillary filtration/exchange with the interstitial fluid:

Answer 30

1. Capillary hydrostatic pressure 2. Capillary oncotic pressure 3. Interstitial fluid hydrostatic pressure 4. Interstitial fluid oncotic pressure

Question 31

What is oncotic pressure, and how does it affect capillary filtration?

Answer 31

* The tendency for fluids to be pulled toward proteins. * Albumin generates about 70% of the oncotic pressure in capillaries, which decreases capillary filtration into interstitial fluid.

Question 32

On what end of capillaries is filtration the greatest?

Answer 32

* arteriole * P_cap \> P_if; filtration occurs * π_if \> π_cap; filtration occurs

Question 33

Draw a capillary with starling force magnitudes:

Answer 33

Question 34

What carries capillary filtrate in the interstitial fluid back to the venous system?

Answer 34

* lymphatic ducts

Question 35

Lymphatic function is compromised if the amount of capillary filtrate in the interstitial fluid is greatly increased. This causes edema. How can this occur?

Answer 35

1. increased arterial pressure (increased Pcap) 2. increased venous pressure (increased Pcap) 3. a pathological increase in capillary permeability

Question 36

When does edema occur?

Answer 36

* when there is increased capillary pressure that leads to increased filtration that overwhelms the lymphatic system.

Question 37

The two types of diffusion that occurs from capillaries to interstitial fluid:

Answer 37

1. **via pores:** * water soluble molecules; rapid 2. **via plasma membrane:** * lipid-soluble molecules (gases); very rapid

Question 38

The pressure drop across the arterial-venous tree is determined by what equation?

Answer 38

**Pa - Pv = CO x R** * R is determined by the arterial side, mostly by arterioles. (TPR = (Pa - Pv)/QT)