73: Control of Blood Pressure and Volume

Question 1

…… and ……… intake/excretion determines ECF, blood volume (BV) & blood pressure (BP)

Answer 1

Na+ and H20

Question 2

When the body contains too much ECF, … and ……..rise

Answer 2

Blood Volume and Blood Pressure

Question 3

Rise in urinary water (volume) excretion due to raised BP

Answer 3

Pressure diuresis

Question 4

Rise in Na+ excretion due to raised BP

Answer 4

Pressure natriuresis

Question 5

Autoregulation occurs when GFR and RBF constant with increases of BP between ……….

Answer 5

80-180 mmHg

Question 6

Acute rise in blood pressure leads to intrinsic ………. in urinary Na+ excretion.

Answer 6

Increase Na+ Excretion.

no SNS, renin/angiotensin II, antidiuretic hormone activity (ADH

Question 7

Chronic rise in Blood pressure leads to continued ……

Answer 7

Increase in urinary Na+ output due to hormonal activity (decrease R-A-A system; increase atrial natriuretic peptide (ANP)) excreting Na+/ H2O

Question 8

……….. maintains fluid balance to keep changes in BV, ECF, CO & BP minimal even with large changes in Na+/ H2O intake

Answer 8

Feedback mechanism

Question 9

If increase Na+/H2O intake, BP …………

Answer 9

Increases

To compensate renal output of Na+/H20 also increases.

Question 10

If BP decreases, Na+/H2O intake …….

Answer 10

Decreases

To compensate renal output of Na+/H2O decreases

Question 11

BV remains constant despite large changes in ………

Answer 11

Fluid Intake

Question 12

Why does BV remains constant despite large changes in fluid intake?

Answer 12

1. Slight change in BV changes cardiac output by changing mean circulatory filling pressure & venous return
2. Change in CO changes BP
3. Change in BP causes large change in urine output through pressure diuresis and hormonal activity

Question 13

Only change seen in Blood Volume is when fluid intake is too………to make up for fluid losses (i.e. evaporation

Answer 13

Low

Question 14

……… ,part of juxtaglomerulus apparatus, sense tubular flow of NaCl and send feedback signals to afferent or efferent arteriole to constrict/dilate to keep RPF and GFR at normal levels

Answer 14

Macula Densa Cells

Question 15

The juxtaglomerular apparatus (JGA) responds to low blood volume or blood pressure (due to dehydration or loss of blood) stimulates the …………….system

Answer 15

Renin-Angiotensin-Aldosterone System

Question 16

Protein enzyme released from granular cells of juxtaglomerular apparatus

Answer 16

Renin

Question 17

The secretion of renin is stimulated by:

Answer 17

1. Decreased arterial pressure leading to decreased renal perfusion pressure
2. Decrease in NaCl sensed by macula densa cells
3. Increased activity of renal sympathetic nerves

Question 18

Renin catalyzes conversion angiotensinogen to Angiotensin I eventually giving ………….

Answer 18

Angiotensin II

Question 19

Powerful controller of Na+ reabsorption

Answer 19

Angiotensin II

Question 20

Angiotensin II secretion is stimulated by…..

Answer 20

1. Decreased arterial pressure leading to decreased renal perfusion pressure
2. Low Na+ intake

Question 21

Actions of Angiotensin II:

Answer 21

Actions:
➢ Stimulates aldosterone secretion from adrenal glands ➢ Vasoconstriction (renal arterioles - mainly efferent when low; afferent when high)
➢ Stimulates thirst
➢ Increase NaCl reabsorption in proximal tubule
➢ Increases Na+/H+ exchanger in proximal tubule (therefore also aids in ??? reabsorption)

Question 22

Angiotensin II causes increased Na+/H20 reabsorption in the ……… which indirectly stimulates Na+ reabsorption in LD/CD via aldosterone.

Answer 22

Proximal Convoluted Tubule

Question 23

Angiotensin II ……… blood pressure via vasoconstriction and …….. the drive to drink

Answer 23

Increases blood pressure

Increases drive to drink

Question 24

Angiotensin II ……… Na+/H2O excretion, …………..ECF & arterial pressure

Answer 24

Decreases Na Na+/H2O excretion

Increase ECF & arterial pressure

Question 25

➢ Secreted by glomerulosa cells of adrenal cortex
➢ Binds to basolateral receptors on principals cells of LD/CD
➢ Directs synthesis of proteins involved in Na+ reabsorption (luminal membrane Na+ channel, Na+/K+-ATPase)

Answer 25

Aldosterone

Question 26

Aldosterone secretion is stimulated by:

Answer 26

1. Angiotensin II
2. Hyperkalemia (high plasma [K+])
3. Hyponatremia (low plasma [Na+])

Question 27

Actions of Aldosterone:

Answer 27

Actions:
➢ Increase Na+/H2O reabsorption by principal cell in LD/CD
➢ Increase K+ secretion
➢ Increase H+ secretion from a-intercalated cells

Question 28

The overall effect of the Renin-Angiotensin-Aldosterone System:

Answer 28

Low blood pressure (BP) stimulates renin secretion from the kidney. Renin stimulates the production of Angiotensin II, which stimulates aldosterone secretion from the adrenal cortex. Aldosterone increase Na+ and water reabsorption in the kidney.

Question 29

Increases in ECF volume dilute OncoticPC and ……… PCT reabsorption

Answer 29

Decrease

Question 30

………. in ECF volume concentrates OncoticPC and stimulates PCT reabsorption

Answer 30

Decreases

Question 31

Nerves reduces Na+ excretion in 3 ways:

Answer 31

1. Decreases GFR and RBF leads decreased filtered Na+ load and PT cap hydrostatic pressure for excretion
2. Direct stimulatory effect on Na+ reabsorption by renal tubules
3. Causes renin release leads to increases angiotensin II and aldosterone levels for reabsorption

Question 32

• Peptide hormone secreted by posterior pituitary
• Involved in the regulation of body water content
• Also called vasopressin

Answer 32

Anti-Diuretic Hormone (ADH)

Question 33

The secretion of Anti-Diuretic Hormone (ADH) is stimulated by:

Answer 33

1. Increased plasma osmolarity of 1 mOsm/L (most important physiologic stimulus)
2. Hypovolemic loss of >8% ECF (MOST POTENT stimulus)

Question 34

Large volume changes evoke ADH secretion regardless of …………

Answer 34

Osmolarity/Tonicity

Question 35

Actions of Anti-Diuretic Hormone (ADH):

Answer 35

Allows formation of water channels in the late distal and collecting duct increasing reabsorption of water  increases urine osmolarity and decreases urine flow volume
➢ Increases H2O permeability (V2 receptors)
➢ Increases contraction of vascular smooth muscle (V1 receptors)

Question 36

Actions of……… on renal tubule :
➢ Increases H2O permeability
➢ Increases 2Cl-/Na+/K+ co-transporter effectiveness
➢ Increases urea permeability

Answer 36

Anti-Diuretic Hormone (ADH)

Question 37

➢ADH binds to ………receptor
➢……………. that increases cAMP
➢ Increases in cAMP cause the insertion of …………(H2O channels) to facilitate H2O reabsorption

Answer 37

V2
G-protein coupled receptors
Aquaporins

Question 38

➢ Released by cardiac atrial myocytes
➢ Receptors found in adrenal cortex, vascular endothelium, collecting duct, distal tubule but NOT proximal tubule AND several areas in brain (i.e. thirst center)

Answer 38

Atrial Natriuretic Peptide (ANP)

Question 39

The secretion of Atrial Natriuretic Peptide (ANP) is stimulated by:

Answer 39

Atrial stretch from excess BV (ECF)

Question 40

Actions of Atrial Natriuretic Peptide (ANP):

Answer 40

Actions:
➢ Vasodilation (afferent arterioles - also constricts efferent arterioles)
➢ Inhibits Na+ reabsorption at medullary CD
➢ Inhibits norepinephrine & angiotensin II induced vasoconstriction
➢ Inhibits renin and aldosterone secretion
➢ Inhibits ADH secretion
➢ Inhibits adenylate cyclase in target tissues