Long Term Control of Blood Pressure

Question 1

what inherent flaws exist in the way we analyze blood pressure?

Answer 1

everyone has a different set point for normal and it changes over the course of the day

Question 2

how are hypertension and hypotension defined?

Answer 2

hypertension is sustained pressure of 140/90 or higher

hypotension is systolic below 90

Question 3

what types of hypertension are normal? abnormal?

Answer 3

transient elevation caused by fever, physical exertion and emotional upset are normal
chronic elevation is abnormal

Question 4

what does chronic hypertension cause?

Answer 4

heart failure, vascular disease, renal failure and stroke

Question 5

what are the fast, intermediate and slow ways to change blood pressure?

Answer 5

fast- baroreceptor reflex
intermediate- renal vascular resistance
slow- changes in renal and water excretion

Question 6

describe the renin- angiotensin activation pathway

Answer 6

angiotensinogen is synthesized by the liver. it is activated to angiotensin I by renin (made by kidney) and is further activated to ACE in lung capillaries to angiotensin II

Question 7

what are the two major effects of angiotensin II?

Answer 7

causes vasoconstriction to increase blood pressure and causes the adrenal cortex to secrete aldosterone

Question 8

what is the effect of aldosterone?

Answer 8

increases water and sodium reabsorption and decreases urine volume. It also stimulates ADH release

Question 9

what are the direct and indirect actions of the kidney to maintain blood pressure long term?

Answer 9

direct- altering blood volume

indirect- renin angiotensin mechanism

Question 10

what is responsible for initiating the renin- angiotensin pathway?

Answer 10

macula densa cells detect decrease in sodium concentration and signal to the juxtaglomerular cells to release renin

Question 11

what are the two levels of effect of the renin-angiotensin- aldosterone system on the body?

Answer 11

local effects and global effects

local effects are less understood but work within organs and can result in damage

Question 12

what are the three determinants of renin secretion?

Answer 12

renal SNS are triggered by neural baroreceptors
intrarenal baroreceptors in afferent arterioles
sodium chloride delivery to macula densa

Question 13

how do transplanted kidneys still function in maintenence of blood pressure?

Answer 13

they can function without innervation from the CNS in the release of renin

Question 14

how does the NaCl sensing of the macula densa reflect blood pressure?

Answer 14

with low GFR caused by low blood pressure, there is increased NaCl reabsorption due to low flow rate. this decreases the delivery of sodium to the macula densa

Question 15

what two effects occur with decreased macula densa NaCl reception?

Answer 15

increased renin release and decreased afferent arteriole resistance to increase GFR

Question 16

how does angiotensin II impact GFR?

Answer 16

by constricting mesangial cells in the kidney to decrease surface area and reduce GFR

Question 17

how does angiotensin II impact granular cells?

Answer 17

provides negative feedback to inhibit renin production by binding AT receptors and decreasing intracellular Ca

Question 18

when does sympathetic tone have more of an influence on the kidney? does a renal nerve ablation fix this?

Answer 18

in resistant hypertension

there was no statistically significant difference between the sham procedure and the actual one

Question 19

what three factors influencing blood pressure?

Answer 19

cardiac output, peripheral resistance and blood volume

Question 20

what does blood pressure equal?

Answer 20

cardiac output x peripheral vascular resistance

Question 21

what three factors influence to cardiac output?

Answer 21

blood volume, arterial/venous compliance and resistance to venous return

Question 22

what four effectors exist for the control of sodium content of the blood?

Answer 22

changes in GFR driven by sympathetic nerves and angiotensin II as well as antidiuretic hormone and atrial naturetic peptide

Question 23

what is pressure diuresis?

Answer 23

increased fluid loss from the kidney with increased blood pressure

Question 24

what does the equilibrium point for pressure naturesis reflect?

Answer 24

an equilibrium between intake and renal output at a normal water and salt intake.

Question 25

what is the effect of increased blood pressure on GFR, angiotensin levels, fluid resorption in the proximal tubule and excretion of salt and water?

Answer 25

increased GFR, decreased A II, decreased fluid resorption and increased excretion of salt and water to decrease blood pressure

Question 26

what is a major problem with ACE inhibitors? what are they used for?

Answer 26

that they prevent conversion to angiotensin II in a hypotensive situation
used to prevent water retention in people with high blood pressure

Question 27

other than angiotensin II, what controls aldosterone secretion?

Answer 27

plasma K concentration and atrial naturetic peptide

Question 28

what is the effect of aldosterone? how much effect does it have?

Answer 28

stimulates Na reabsorption in cortical collecting tubules and collecting ducts. only increases sodium reabsorption by 1-2% (a lot of volume because of high passage of Na through those tubules)

Question 29

what are the 5 major effects of angiotensin II synthesis?

Answer 29

increased SNS activity, increased Na, Cl and decreased K reabsorption (H2O retention), increased aldosterone secretion, arteriolar vasoconstriction and ADH secretion by the posterior pituitary

Question 30

how does aldosterone change solute composition of the urine?

Answer 30

activates and increases synthesis of Na/K pump and other channels that transport these ions. leads to increased Na resorption and increased K secretion

Question 31

what prevents over correction of other reflexes in the kidney?

Answer 31

tubuloglomerular feedback acts in the opposite direction to other reflexes by inhibiting the increase in renal blood flow and pressure at the glomerular capillary during high renal arterial pressure

Question 32

what are two of the naturetic peptides and what are their two actions? what are they used for?

Answer 32

ANP and BNP
inhibit the release of renein and relaxation of afferent arterioles
used diagnostically to assess congestive heart failure

Question 33

what is the function of antidiuretic hormone?

Answer 33

increases water reabsorption

Question 34

what other hormones increase and decrease Na reabsorption?

Answer 34

increase- cortisol, estrogen, growth hormone, thyroid hormone and insulin
decrease- glucagon, progesterone and PTH

Question 35

where are osmoreceptors located?

Answer 35

in the hypothalamus along the ventricles

Question 36

what are the different controls of ECF homeostasis in the proximal and distal nephron components

Answer 36

proximal- regulates ECF based on BP (both sodium and water)

distal- two mechanisms to maintain water and sodium separately (ADH and aldosterone)

Question 37

under what conditions is ADH secreted? inhibited? which prevails when they conflict?

Answer 37

secreted with decreased blood pressure sensed by baroreceptors (more important than osmolality)
inhibited with decreased fluid osmolality sensed by chemoreceptors

Question 38

why do people get hypertension?

Answer 38

there is a shift of the renal function curve that impairs naturesis and increases sodium and water retention

Question 39

how does obesity lead to hypertension?

Answer 39

hyperinsulinemia increases sodium reabsorption and smooth muscle cell proliferation (increasing vasoconstriction) also increases overall inflammation