Hormonal Control of Blood Pressure

Question 1

what are the two main goals when there is severe hemorrhage?

Answer 1

respond rapidly to perfuse vital organs and gradually replenish blood volume

Question 2

what are the rapid acting control mechanisms in response to acute change in blood pressure? what types of responses are these?

Answer 2

baroreceptors, chemoreceptors and CNS ischemic response.

these are nervous reflexes

Question 3

what are the three intermediate controls of blood pressure?

Answer 3

renin-angiotensin vasoconstrictor mechanism, capillary fluid shift mechanism and the stress relaxation mechanism

Question 4

what is the long term control of blood pressure?

Answer 4

volume control by the kindney, especially the renin-angiotensin-aldosterone system

Question 5

what occurs when blood flow to the vasomotor center in the brain stem becomes decreased enough to cause cerebral ischemia?

Answer 5

the vasoconstrictor and cardioaccelerator neurons in that area become strongly excited and blood pressure compensates as much as it possibly can (up to 250 mmHg)

Question 6

what is the specific cause of the CNS ischemic response?

Answer 6

buildup of local concentration of CO2 stimulates vasomotor control centers

Question 7

what happens to urine production during the CNS ischemic response and why?

Answer 7

it slows dramatically and may even stop. this is because the vasoconstriction can be so great that some peripheral vessels become occluded

Question 8

how far must the arterial pressure fall before the CNS ischemic response occurs? when it is optimal?

Answer 8

must be down to 60 mmHg but is optimal at 15-20 mmHg

Question 9

what does the Cushing reaction respond to?

Answer 9

increased pressure of cerebrospinal fluid around the brain that cuts off blood flow to the brain

Question 10

how does the cushing reaction respond to ischemia?

Answer 10

it initiates the CNS ischemic response so that the arterial pressure rises to a pressure above the intracranial pressure so there is blood flow

Question 11

what are the four major groups of receptors that compensate for a large fall in mean arterial pressure?

Answer 11

high and low pressure baroreceptors, peripheral chemoreceptors and central chemoreceptors

Question 12

what response do high pressure baroreceptors have to decreased pressure and what is the result?

Answer 12

decreased firing rate

increases heart rate, cardiac contractility and vasoconstriction

Question 13

what do low pressure baroreceptors respond to and what does it mediate?

Answer 13

decrease firing rate responding to decreased circulating volume leads to SNS mediated vasoconstriction and ADH release

Question 14

what do peripheral chemoreceptors respond to and what do they cause?

Answer 14

respond to hypoxia by increasing firing rate and increases vasoconstriction and changes ventilation

Question 15

where can central chemoreceptors be found and what do they respond to? what effect does this have?

Answer 15

respond to brain ischemia (acidosis) and mediate the CNS ischemic response

Question 16

the major compensations that are mediated with blood loss can keep MAP normal with what amounts of blood loss?

Answer 16

15-20% blood loss

Question 17

where is renin secreted and what is its effect?

Answer 17

secreted by the kidneys and it cleaves the circulating protein angiotensinogen to angiotensin I

Question 18

where is angiotensin I converted to angiotensin II and by what enzyme?

Answer 18

in the lungs by angiotensin converting enzyme (ACE)

Question 19

what is the vascular effect of angiotensin II?

Answer 19

it is a powerful short acting arterial vasoconsrictor and causes venoconstriction to increase venous return as well

Question 20

what effect does angiotensin II have on the kidney, brain and adrenal gland?

Answer 20

kidney- retains salt and water
brain-promotes release of ADH
adrenal gland- causes the release of aldosterone

Question 21

what is the effect of aldosterone?

Answer 21

increases the salt and water reabsorption by the kidneys

Question 22

what inactivates angiotensin II?

Answer 22

angiotensinases

Question 23

how much does the renin-angiotensin vasoconstrictor response return mean arterial pressure after a drop from 100-50 mmHg?

Answer 23

can raise pressure back to about 83 mmHg (only raised to 60 mmHg without the response)

Question 24

describe the capillary fluid shift mechanism of responding to a decrease in MAP.

Answer 24

decreased intravascular hydrostatic pressure increases fluid resorption in the capillaries and therefore increases blood volume

Question 25

what is unstressed blood volume? what is stressed volume?

Answer 25

the volume of blood in the peripheral venous compartment

stressed- the volume in the arteries that produces pressure by stretching the vessels

Question 26

what is the every day function of the renin angiotensin system?

Answer 26

allows a person to eat salt in varying amounts without causing great changes in extracellular fluid volume or arterial pressure

Question 27

when salt intake is increased, how does the blood volume and pressure react? what does this do to renin and angiotensin?

Answer 27

increased extracellular volume and arterial pressure

decreases renin and angiotensin

Question 28

what is the result of decreased renin and angiotensin on the kidney?

Answer 28

decreases retention of salt and water

Question 29

where is antidiuretic hormone manufactured and secreted?

Answer 29

synthesized in the supraoptic nuclei of the hypothalamus and is stored and released at the posterior pituitary

Question 30

when is ADH secreted?

Answer 30

in response to increased osmolarity of extracellular fluid, decreased volume (low pressure baroreceptors), decreased blood pressure, antiotensin II, and stress

Question 31

what are the major and minor effects of ADH?

Answer 31

increase water resorption in the kidney and minor vasoconstrictor effect

Question 32

what inhibits the secretion of ADH?

Answer 32

increased blood volume and pressure, ethanol, decreased fluid osmolarity and atrial natriuretic hormone

Question 33

what hormones are smooth muscle dilators and constrictors?

Answer 33

dilaor- atrial natriuretic peptide

constriction- ADH and angiotensin II (ACE found on endothelium)

Question 34

other than the carotid sinus and the aortic arch, where are there other high pressure baroreceptors? what do they regulate?

Answer 34

in the afferent arterioles in the renal juxtalomerular apparatus. regulate renin release

Question 35

when is atrial natriuretic peptide released and where?

Answer 35

when there is volume overload in the atria of the heart