Chapter 19 - Guyton

Question 1

pressure diuresis

Answer 1

increased urine output

Question 2

pressure natriuresis

Answer 2

increased sodium output

Question 3

The two primary determinants of the long-term arterial pressure level are as follows:

Answer 3

1) degree of pressure shift of the renal output

curve for water and salt; 1) level of the water and salt intake line

Question 4

Explain the overall mechanism by which increased extracellular fluid volume elevates arterial pressure.

Answer 4

increase extracellular fluid volume–>increases
blood volume–>increase mean circulatory
filling pressure–>increase venous
return of blood to the heart–>increase
cardiac output–>increase arterial pressure

Question 5

Two ways in which cardiac output can increase arterial pressure?

Answer 5

direct effect of increased cardiac output to increase the pressure, and the other is an indirect effect to raise total peripheral vascular resistance through autoregulation of blood flow

Question 6

How does salt intake affect extracellular fluid volume?

Answer 6

increased osmolality from salt intake stimulates thirst center and drink more fluid; increased osmolality also stimulates hypothalamic-posterior pituitary gland secretory mechanism to secrete increased quantities of antidiuretic hormone (decrease urine output)

Question 7

A mean arterial pressure greater than ____ mm Hg (normal is about 90 mm Hg) is considered to be hypertensive (diastolic blood pressure is greater than about 90 mm Hg and the systolic pressure is greater than about 135 mm Hg).

Answer 7

110

Question 8

Three primary lethal effects of chronic hypertension.

Answer 8

heart failure or CHD (excessive workload on heart), cerebral infarct (CVA), renal destruction

Question 9

What occurs during volume-loading hypertension (intake of salt and water increased substantially and held there)

Answer 9

The first stage results from increased fluid volume causing increased cardiac output (causing hypertension). The second stage is characterized by high blood pressure and high total peripheral resistance but return of the cardiac output to near to normal.

Question 10

What is the function of aldosterone?

Answer 10

increases the rate of reabsorption of salt and water by the tubules of the kidneys, decreasing urine output and causing an increase in blood volume and extracellular fluid volume

Question 11

Explain the renin-angiotensin vasoconstrictor mechanism for arterial pressure control.

Answer 11

decreased arterial pressure–>renin (kidney)–>renin substrate (angiotensinogen)–>Angiotensin I–>Angiotensin II (converting enzyme in lungs)–>vasoconstriction (renal retention of salt and water)–>increased arterial pressure

Question 12

Whenever excess amounts of __________ circulate
in the blood, the entire long-term renal–body fluid mechanism for arterial pressure control automatically becomes set to a higher arterial pressure level than normal.

Answer 12

angiotensin

Question 13

When the renin-angiotensin system becomes activated, the rate of ___________ secretion usually also increases.

Answer 13

aldosterone

Question 14

Explain the sequential events that occur with increased salt intake (with a functioning renin-angiotensin system under normal conditions).

Answer 14

Increased salt intake–>Increased extracellular volume–>Increased arterial pressure–>Decreased renin and angiotensin–>Decreased renal retention of salt and water–>Return of extracellular volume almost to normal–>Return of arterial pressure almost to normal

Question 15

How does angiotensin increase arterial pressure (two ways)?

Answer 15

constricting arterioles throughout the body, causing kidneys to retain salt and water

Question 16

What is primary hypertension?

Answer 16

also known as “essential hypertension” by many clinicians; the hypertension is of unknown origin

Question 17

Some of the characteristics of primary hypertension caused by excess weight gain and obesity include:

Answer 17

cardiac output is increased (excess body tissue), increased sympathetic nerve activity (especially in kidneys), angiotensin II and aldosterone levels are increased, renal-pressure natriuresis mechanism is
impaired

Question 18

Two general classes of drugs used to treat hypertension.

Answer 18

vasodilator drugs and natriuretic or diuretic drugs

Question 19

Three mechanisms of vasodilator drug action.

Answer 19

inhibiting sympathetic nervous signals to the kidneys; relaxing the smooth muscle of the renal vasculature; blocking the action of the renin-angiotensin system

Question 20

Rapidly acting pressure control mechanisms, acting within seconds or minutes.

Answer 20

baroreceptors, chemoreceptors, CNS ischemic response

Question 21

Pressure control mechanisms that act after a number of minutes.

Answer 21

renin-angiotensin vasoconstrictor mechanism; stress-relaxation of the vasculature; shift of fluid through the tissue capillary walls in and out of the circulation to readjust the blood volume as needed

Question 22

What is the stress-relaxation mechanism?

Answer 22

When the pressure in the blood vessels becomes too high, they become stretched and keep on stretching more and more for minutes or hours; as a result, the pressure in vessels falls to normal.

Question 23

What is the capillary fluid shift mechanism?

Answer 23

any time capillary pressure falls too low, fluid is
absorbed through the capillary membranes from the tissues into the circulation, thus building up the blood volume and increasing the pressure in the circulation

Question 24

Long-term mechanisms for arterial pressure regulation.

Answer 24

renal-blood volume pressure control mechanism (feedback gain for control of arterial pressure equal to infinity meaning it will bring the pressure all the way back eventually)