Physio 11

Question 1

what is the kidney’s response to increase in ECF volume?

Answer 1

increases Na+ excretion. kidney responds to increase in ECF volume, NOT sodium concentration

Question 2

effective circulating volume

Answer 2

functional blood volume reflecting the extent of tissue/organ perfusion where blood pressure is sensed. normally parallels the ECF volume, bbut can be less than total ECF in congestive heart failures or other things causing edema

Question 3

central vascular sensors

Answer 3

low pressure (very important): atria and pulmonary vasculature

high pressure (less important): carotid sinus, aortic arch, and juxtaglomerular apparatus (renal afferent arteriole)

Question 4

other sensors of blood pressure

Answer 4

sensors are in the CNS and the liver. they are not as important as the other ‘central’ sensors

Question 5

what are the four parallel effector systems?

Answer 5

RAA (renin angiotensin aldosterone), sympathetic nerve activity, ADH/AVP, and atrial natriuretic peptide

Question 6

renin-angiotensin-aldosterone hormonal system

Answer 6

angiotensin II promotes sodium retention by stimulating Na/H exchange in the proximal tubule. decreases renal plasma flow, again promoting Na reabsorption. Aldosterone increases sodium reabsorption by the late distal tubule and early collecting duct.

Question 7

angiotensinogen and renin

Answer 7

angiotensinogen substrate of the enzyme renin and is made by the liver and released into the systemic circulation

renin is synthed and stored in granular cells of the juxtaglomerular apparatus of the kidney. decreased effective circulating volume increases renin release. converts angiotensinogen into angiotensin I

Question 8

angiotensin I

Answer 8

converted to angiotensin II by angiotensin converting enzyme. mainly found in the lungs, but is found in the entire body. located on the luminal surface of vascular endothelium. II is degraded by aminopeptidases to III, which is less active

Question 9

three renal mechanisms regulating renin release

Answer 9

1. local renal baroreceptors in afferent arterioles respond to low pressure and increase secretion of renin
2. decreased systemic arterial blood pressure stimulates baroreceptor reflex which causes increased sympathetic drive to juxtaglomerular apparatus increasing secretion of renin
3. cells of macula densa sense tubular fluid sodium concentration, and if low, cause increased release of renin

Question 10

actions of angiotensin II

Answer 10

induces aldosterone release from adrenal cortex. acts on hypothal to increase thirst and induce release of ADH/AVP. vasoconstricts renal and other systemic vessels to increase GFR and increase starling forces to favor reabsorption. enhances Na/H exchange in the proximal tubule which increases sodium reabsorption. induces hypertrophy of the renal tubule cells

Question 11

aldosterone actions

Answer 11

acts on kidney tubules to increase reabsorption of Na and water. acts on the distal nephron to increase the secretion and excretion of K+. induces increased Na reabsorption by prinicpal cells in the late distal tubule and early collecting duct. increases Na transporter expression (basolateral Na/K pumps, apical Na channels, and mitochondrial enzyme expression)

Question 12

aldosterone mechanism of action

Answer 12

diffuses into cell and binds to an intracellular aldosterone receptor to form a receptor-aldosterone complex. complex enters nucleus and induces the transcription of mRNAs coding for membrane transport proteins mediating transcellular sodium reabsorption as well as mitochondrial enzymes mediating oxidative phosphorylation

Question 13

secretogogues for aldosterone (things that cause increased aldosterone excretion)

Answer 13

angiotensin II, increased plasma K concentration, adrenocorticotropic hormone (ACTH) (induced by angiotensin II)

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Question 14

hypernatremia

Answer 14

increase in plasma sodium concentration to a level above the normal range of 135-145 mEq/L. symptoms include lethargy, weakness, and irritability. severe symptoms like seizure and coma occur over 158 mEq/L. caused by a loss of water from the plasma due to inadequate consumption of water or an inappropriate renal excretion of water.

Question 15

hypovolemic and hypervolemic hypernatremia causes

Answer 15

hypo: inadequate water consumption, extreme sweating, severe diarrhea, excessive renal excretion of water
hyper: excessive hypertonic fluid consumption (sea water) and hyperaldosteronism

Question 16

hyponatremia

Answer 16

decrease in plasma sodium concentration to a level below normal range of 135-145 mEq/L. symptoms include nausea, vomiting, headache, lethargy, fatigue, loss of appetite, restlessness, irritability, weakness, spasms, cramps. severe symptoms like neuro problems, brain swelling, seizures and coma at levels below 125. caused by gain of water in plasma due to extreme consumption of water or inapprotpriate water reabsorption by kidney

Question 17

causes of hyper and hypovolemic hyponatremia

Answer 17

hyper: inappropriate water reabsorption. may occur in congestive heart failure and other things that cause edema
hypo: hemorrhage, prolonged exercise in heat, diuretic drug therapy. addison’s disease: hypoaldosteronism. severe vomiting / diarrhea

Question 18

sensors of ECF volume and osmolarity

Answer 18

volume: carotid sinus, aortic arch, renal afferent arteriole, atria
osmolarity: hypothalamic osmoreceptors