Physiology 19: Role Of Kidneys In Arterial Pressure And Hypertension

Front 1

What is pressure diuresis?

Back 1

increased urinary output caused by high arterial pressure

Front 2

What is pressure natriuresis?

Back 2

increased salt output in urine caused by high salt content

Front 3

What is the "near infinite feedback gain principle" for renal control of blood pressure?

Back 3

if the arterial pressure is too high, kidneys will excrete water until the equilibrium point is reached (normal blood pressure). if it is too low, kidneys will retain water until normal pressure is reached

Front 4

2 factors that will lead to long-term high blood pressure regarding kidneys?

Back 4

shift of renal output curve right (kidney damage) or increased salt/water intake

Front 5

What does the "chronic renal output curve" show us?

Back 5

changes in blood pressure in patients with normal kidney function, but chronic high salt/water intake. their body has adapted to the high salt/water intake and blood pressure is barely affected by high salt/water intake

Front 6

If a patient with chronic high salt/water intake suffers from sudden kidney damage, what immediate changes will we see?

Back 6

Increasing blood pressure. Patients with chronic high salt/water intake do not have high blood pressure because the kidneys adapt (pressure diuresis/natriuresis). if the kidneys are not removing this high salt/water content from circulation, the BP will rise. The chronic renal output curve becomes less steep and models the acute curve.

Front 7

When blood pressure drops, formation of anti-natriuretic hormones (increases or decreases)?

Back 7

increases. anti-natriuretic hormones lead to an increase in salt/water in the blood (less excretion by kidneys), raising blood pressure. a natriuretic hormone removes salt/water from the blood, reducing BP

Front 8

A patient who is salt-insensitive regarding blood pressure has a renal output curve that looks (steep or flat)?

Back 8

steep. the chronic renal output curve is very steep due to the kidney's ability to adapt and remove the salt/water from the patient. thus their BP is salt-insensitive. it doesn't matter how much salt they eat, their kidneys are already adapted to remove it before it can affect BP

Front 9

A patient with damaged kidneys had a blood pressure that is likely salt (sensitive or insensitive)?

Back 9

if the kidneys are not functioning, their BP is salt sensitive. any salt (water follows) intake will increase BP since the kidneys can't remove the salt/water

Front 10

If there is a severe increase in peripheral resistance (except in the kidneys), what will happen to the BP, assuming kidney function is normal?

Back 10

nothing will happen to BP, kidneys will still be able to remove the water from the vessels to return to homeostasis

Front 11

When does increased vascular resistance lead to an increase in BP, even if the kidneys are functioning?

Back 11

if the renal and intra-renal arteries are also affect by the high resistance, then the kidneys won't be able to function to remove water as well to control BP

Front 12

What increased peripheral resistance of which arteries are most likely to cause increased BP?

Back 12

RENAL and intrarenal arteries. resistance in any other vessel can be compensated for by the kidneys, but if the resistance is in the kidneys themselves, then water will have a hard time being removed to compensate

Front 13

When there is an increase in cardiac output, a phenomenon called "auto-regulation" occurs. What is that?

Back 13

excess blood flow through a tissue = vasoconstriction to return blood flow to normal = high resistance = high BP

Front 14

What is the "indirect" way that high cardiac output leads to high BP?

Back 14

auto-regulation. more blood flowing through the tissue = vasoconstriction to return blood flow to normal = high resistance = high BP

Front 15

Why does salt intake have a greater effect on BP than water intake?

Back 15

water can be excreted easily. salt stimulates thirst centers and ADH that lead to water being forced in.

Front 16

3 reasons chronic hypertension is fatal.

Back 16

1) excess workload on heart (more resistance) = failure. 2) stroke risks (cerebral infarct). 3) kidney destruction

Front 17

What is "volume loading hypertension"?

Back 17

high BP caused by excess fluid volume

Front 18

What type of hypertension would we expect from a patient with a kidney removed and high salt diet?

Back 18

volume loading hypertension

Front 19

With partial kidney removal and high salt diet, there is a rapid increase in blood volume. Why does BP increase at a slower rate?

Back 19

peripheral resistance decreases due to baroreceptors attempting to maintain the normal BP

Front 20

Why does total peripheral resistance increase with high cardiac output?

Back 20

auto-regulation. vasoconstriction of vessels to maintain normal blood flow through tissues

Front 21

In volume loading hypertension, which comes first? Peripheral resistance or Hypertension?

Back 21

Hypertension develops first form the high fluid volumes, then resistance develops via "auto-regulation" from the high cardiac output

Front 22

Where is pro-renin stored?

Back 22

JG cells (juxtaglomerular)

Front 23

What are JG cells?

Back 23

modified smooth muscle in afferent arterioles before glomerulus. store renin (pro-renin)

Front 24

When is renin released form JG cells?

Back 24

when BP falls in the afferent arterioles of the glomerulus

Front 25

Renin is an enzyme that works on what substrate?

Back 25

angiotensinogen. renin converts angiotensinogen into angiotensin 1

Front 26

How does angiotensin 1 become angiotensin 2?

Back 26

angiotensin converting enzyme

Front 27

Function of angiotensin 2

Back 27

potent vasoconstrictor, salt/water retention, and signals release of aldosterone from adrenal cortex (zona glomerulosa)

Front 28

What are angiotensinases?

Back 28

degrade angiotensin 2

Front 29

In "One kidney Goldblatt Hypertension", why does hypertension occur?

Back 29

a clamp is placed on the renal artery. the JG cells sense the low BP downstream of the clamp. this leads to angiotensin 2 and aldosterone production = high systemic BP and normal renal artery BP

Front 30

In "One kidney Goldblatt Hypertension", there are 2 events that cause increase in systemic BP seen as 2 separate slopes. What causes them?

Back 30

1st increase is the immediate vasoconstriction caused by angiotensin 2. 2nd slope is form salt/water retention from aldosterone release

Front 31

In "Two kidney Goldblatt Hypertension", why do both kidneys function to retain salt/water?

Back 31

if a patient has both kidneys but 1 renal artery is stenosed, the ischemic kidney will release renin. This renin leads to angiotensin in the blood stream that will affect both kidneys

Front 32

How might a patient develop upper body hypertension?

Back 32

coarctation of the aorta

Front 33

In patients with coarctation of the aorta, why is the blood flow in the legs the same as the blood flow in the arms (even though the arms have a much higher BP)?

Back 33

auto-regulation. the vessels in the arm will constrict to keep excess blood away from the tissue. the blood flow is regulated by the needs of the tissue, not by the pressures

Front 34

What is preeclampsia?

Back 34

hypertension during pregnancy

Front 35

What is neurogenic hypertension?

Back 35

strong sympathetic tone = vasoconstriction = high BP

Front 36

Cutting the nerves to and from the baroreceptors has what affect on hypertension?

Back 36

causes hypertension. body assumes there is a drop in BP so activates adaptive mechanisms to increase BP

Front 37

With a drop in BP, what responses occur within seconds?

Back 37

vasoconstriction, heart rate up

Front 38

With a drop in BP, what responses occur within minutes?

Back 38

renin/aldosterone, stress-releaxation mechanism, capillary fluid shift

Front 39

What is the stress-relaxation mechanism regarding decreasing BP?

Back 39

high BP = more stretched vessels. they stretch so much that eventually they lose elasticity and relax. then there is lower resistance = lower BP

Front 40

How does the capillary fluid shift increase BP?

Back 40

tissue fluid around the capillary moves in to increase volume during emergencies