2.3 Hypertension - SNS manipulators

Question 1

What is the ratio of systolic to diastolic blood volume?

Answer 1

~64% venous

~Heart 7%

~Arterial: 13%

Venous blood can be brought back in as preload through manipulation of vasculature.

Question 2

Which has a more pronounced effect on blood pressure: increasing venous tone or increasing arterial tone? Why?

Answer 2

Increasing arterial tone has a greater impact because pressure is already higher in this system.

Question 3

What three factors create resistance in an arteriole?

vessel diameter, vessel length, and viscosity of blood

Answer 3

vessel diameter, vessel length, and viscosity of blood

Q = flow

r = radius of arteriol

Question 4

What key organs and parts of the vasculature effect BP?

Answer 4

Arterial BP = (cardiac output) x (peripheral vascular resistance)

Question 5

If blood pressure drops

Answer 5

1. baroreceptors detect drop in MAP
2. this activates vasomotor center
3. this increases BP through: kicking in SNS

SNS: increases cardiac output through venous tone (inc preload), contractile force increases which increases venous return and stroke volume; sns also increase HR

SNS also increases peripheral vascular resistance. All of these increase Mean Arterial Pressure (MAP)

When MAP is getting high, baroreceptors can contact the vasomotor center to have it decrease BP, though there are not as many mechanisms to do this. The main thing it can do is decrease HR (decrease output) to lower MAP.

Looking at bottom part of loop, a drop in MAP will lower renal blood flow/pressure. This triggers renin release, which is then converted to angiotensin, which then triggers aldosterone. This causes increase reabsorption of fluid in distal tubue, increasing blood volume.

Question 6

Where do Calcium channel blockers and vasodilators impact blood pressure regulation?

Answer 6

Ca channel blockers decrease peripheral vascular resistance and decrease contractile force.

Vasodilators decrease peripheral vascular resistance and decrease venous tone.

Question 7

Where do ACE inhibitors and ARBs target blood pressure regulation?

Answer 7

Decrease blood volume through Renin/Angiotensin/Aldosterone system.

Question 8

Where do diuretics target blood pressure regulation?

Answer 8

Question 9

Where do alpha blockers target blood pressure regulation?

Answer 9

Alpha blockers trigger the SNS, but specifically focus on reducing peripheral vascular resistance.

Question 10

Where do beta blockers target blood pressure regulation?

Answer 10

Beta blockers have multiple targets of the SNS:

pripheral vasculature, heart rate, contractile force, venous tone

Question 11

Complete the pneumonic for classes of anti-hypertensives:

A
B
C
D
E

Answer 11

Question 12

Review map of anti-hypertensive mechanisms

Question 13

What are ways that drugs modulate the SNS?

Answer 13

Question 14

What are the centrally acting anti-hypertensives that target the alpha-2 receptor?

What do they do to it?

What is the cascade?

What is the net effect?

Answer 14

The net effect is vasodilation.

Question 15

What are adrenergic neuron blocking agents? Why are they undesirable relative to other interventions?

Answer 15

Question 16

Name the major beta blockers by:

• Non-selective (B1 & B2)
• Selective B1
• Partial agonists (partial = competing antagonism)
• Beta-blocking + vasodilating
• Super short activing (used IV)

Answer 16

Note; nebeivalol also releases nitrous oxide.

Question 17

What medication class could:

– prevent reflex tachycardia from a vasodilator

– improve mortality after an MI

– treat congestive HF

Answer 17

Beta blockers

Question 18

What are the major concerns about beta-blockers?

Answer 18

Non-specific beta blockers can limit the efficacy of asthma/COPD drugs.

They present a danger with diabetes because they mask diaphoresis and other signs of hypoglycemia.

Question 19

1. What are the common alpha-1 antagonist medications?
2. What is their effect?
3. What disorders are they used to treat?
4. What are concerns?

Answer 19

1. Common A-1 antagonists/blockers are prazosin, terazosin, doxazosin
2. The most significant effect is vasodilation, but there is also relaxation of smooth muscle in the prostate and other areas
3. Hypertension and BPH urinary retention
4. Concerns include:
   
   1. Orthostatic hypotension from venous pooling
   2. Water and sodium retention when the kidney tries to compensate for decreased BP. A diuretic may need to be added to the alpha-1 antagonist to stop this compensation.