Car 14 - Regulation of BP

Question 1

How does the CNS achieve short term BP regulation?

Answer 1

Baroreceptors in the aortic arch sense that senses high BP and transmits a signal to the medulla via the vagus nerve. Also the carotid sinus baroreceptor can detect high or low BP and sends the signal to the solitary nucleus of the medulla via Glossopharyngeal nerve.

Question 2

Which adrenergic receptors cause vasoconstriction?

Answer 2

Alpha-1 receptors.

Question 3

What happens in regulation of short term BP when there is a drop in BP?

Answer 3

\/ arterial pressure sensed by carotid sinus which \/ afferent baroreceptor firing. This causes ^ efferent sympathetic stimulation and \/ efferent parasympathetic stimulation. This results in ^ alpha1 vasoconstriction and ^ HR and cotractility via beta1 receptors.

Question 4

What is a carotid massage?

Answer 4

^ stretch in carotid tricks the body into thinking there is an ^ in BP, therefore tells the vagus nerve to \/ HR. Listen to the carotid first for carotid bruiting; if they have a plaque, you can dislodge it causing a stroke.

Question 5

What is Cushing’s reflex?

Answer 5

Caused by the baroreceptors, an ^ in intracranial pressure will cause a triad of : ^ systemic BP, reflex bradycardia, Respiratory depression.

Question 6

What do the peripheral chemoreceptors respond to?

Answer 6

Hypoxia. Hypercapnia. Acidosis. This changes are detected in the blood.

Question 7

What do the central chemoreceptors respond to?

Answer 7

They are in the medulla and respond changes in the CFS. They respond to changes in CO2 and pH.

Question 8

What causes smooth muscle cell contraction?

Answer 8

The Calmodulin-Ca complex stimulates myosin light-chain kinase to phosphorylate myosin into myosin-PO4(phosphate). This myosin-PO4 interacts w/ acting to cause contraction.

Question 9

How do Beta2 receptors and Prostaglandin E2 cause smooth muscle relaxation?

Answer 9

Both cause an increase in cAMP, which inhibits myosin light-chain kinase, which is responsible for phosphorylation of myosin so contraction can happen when it binds with actin.

Question 10

How does Sildenafil work to cause smooth muscle relaxation?

Answer 10

It works by inhibiting cGMP phosphodiesterase, which is in charge of turning cGMP back to plain GTP. cGMP is what activates myosin phosphatase, which takes away the phosphate from myosin PO4, causing smooth muscle relaxation. So more cGMP causes more smooth muscle relaxation.

Question 11

How does nitric oxide cause smooth muscle relaxation?

Answer 11

It activates Guanylyl Cyclase, which turns GTP into cGMP, causing activation of myosin phosphatase, taking away the phosphate from myosin-PO4, causing smooth muscle relaxation.

Question 12

Why do G(-) bacteria with LPS cause smooth muscle relaxation (vasodilation) and sepsis?

Answer 12

Because they stimulate iNOS (inducible Nitric Oxide synthase) that converts L-arginine to citrulline and NO. NO activates Guanylyl Cyclase, turning GTP to cGMP, which activates myosin phosphatase, which takes away the phosphate from myosin-PO4, which causes smooth muscle relaxation.

Question 13

What is Atrial natriuretic peptide? What does it do?

Answer 13

Hormone produced in the atria in response to: ^ atrial volume, ^ atrial pressure. It causes vasodilation and is a natriuretic peptide (diuresis of both water and Na). Acts by dilating afferent and constricts efferent arteriole on the renal glomeruli: ^ GFR, promotes diuresis.

Question 14

Which organ receives largest portion of systemic CO?

Answer 14

Liver.

Question 15

Which organ receives highest blood flow per gram of tissue?

Answer 15

Kidneys.

Question 16

Which organ receives 100% of CO from RV?

Answer 16

Lungs.

Question 17

Which organ extracts 80% of oxygen from the blood by default?

Answer 17

Heart.

Question 18

When does myocardial perfusion take place?

Answer 18

During diastole.

Question 19

How does Nitroglycerin relieves angina?

Answer 19

Causes systemic venous vasodilation. It reduces preload, \/ myocardial oxygen demand. It is not due to vasodilation of coronary arteries because they are already vasodilated.

Question 20

What does hypoxia in the lungs cause to the vessels?

Answer 20

It causes vasoconstriction. Everywhere else in the body, it causes vasodilation.

Question 21

Outline the mechanism by which the kidneys regulate BP.

Answer 21

JGA sense low BP and secretes renin. Renin converts angiotensinogen to ATI. ACE converts ATI to ATII in the lungs. ATII causes vasoconstriction and stimulates adrenal cortex to secrete aldosterone. Aldosterone ^ renal reabsorption of Na+ and H2O to expand blood volume and increase BP.

Question 22

What substances act on smooth muscle myosin light-chain kinase? How does this affect BP?

Answer 22

Dihydropyridine calcium channel blockers. Epinephrine acting at beta2-receptors. Prostaglandin E2. All of these cause relaxation of vascular smooth muscle, causing vasodilation and \/ BP.

Question 23

Describe the chain events in which hypotension causes a reflex tachycardia.

Answer 23

Baroreceptors in the carotid sinus sense low BP. Low BP results in less stretch of the carotid sinus, causing \/ stimulation of glossopharyngeal nerve and \/ inhibition of sympathetic output (causing ^ sympathetic output, \/ in parasympa). This causes reflex tachycardia.