Salt & Water Balance

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Aldosterone, ADH, ANF

3 Hormones that control Salt and Water Balance.

Aldosterone

This hormone's main target is the kidney and it decreases Na+ excretion and causes water retention and increased blood pressure.

renin-angiotensin

Aldosterone is regulated by ___________ ___________ system involving kidney and liver.

Positively

Blood volume is ___________ correlated with blood pressure.

reabsorption

Blood volume is regulated by regulating sodium __________ in the kidney.

osmosis.

water follows Na+ by _____________

Blood volume

Increased Na+ = increased _______________

Glomerular Filtration

First step of urine formation is ___________ _____________.

Tubular reabsorption

Second step of urine formation is ______________ ________________.

tubular secretion

Third step of urine formation is ____________ ____________

excretion

Fourth step of urine formation is _________

Juxtaglomerular Apparatus

Main organ that regulates aldosterone. Part of the afferent arteriole wall.

Macula densa cells

These cells are part of the distal convoluted tubule wall and located next to juxtaglomerular cells

Juxtaglomerular apparatus

Juxtaglomerular cells and macula densa make up what?

chemical signals

Juxtaglomerular apparatus secrete ________ ________ that ultimately regulate aldosterone.

Sympathetic NS.

Juxtaglomerular apparatus gets activated when the _________ ________ is activated.

mean arterial pressure

A drop in this is sensed by baroreceptors and triggers a sympathetic response.

sympathetic nerves.

Juxtaglomerular cells richly innervated by ________ _________.

stretch receptors

Drop in Afferent Arteriole Blood Pressure is directly sensed by _________ __________ in juxtaglomerular cells.
Drop is Na+ reabsorpt

Glomerular Filtration Rate.

If there is less blood going to the kidney, less Na and water reabsorbed, this will lead to a drop in __________ __________ ________.

Macula densa cells

Drop is Na+ reabsorption in distal convoluted tubules is sensed by __________ __________ _____________.

Renin

When Juxtaglomerular apparatus is activated, __________ is secreted.

Angiotensinogen

Renin acts on __________ which is a large protein made by the liver and already circulating in high concentration in the blood.

Angiotensin I

Angiotensinogen is the substrate for renin and renin acts on it to produce _____________(.

Inactive

Angiotensinogen I is biologically ____________.

ACE

_____________ converts Angiotensinogen I to Angiotensinogen II (8AA).

Pulmonary circuit

Having Renin in the ________ _________, aids in the rapid conversion of Angiotensin I to Angiotensin II.

Glands, receptors.

Angiotensin II acts like a hormone, because it has __________ and ____________.

Blood Pressure

Angiotensin II increases __________ ___________. Thus a target of 40% of blood pressure medications.

Vasoconstriction

Angiotensin II directly causes widespread __________ of arterioles.

Cardiac

Angiotensin II directly causes increase ___________ excitability.

Peripheral resistance

Angiotensin II directly causes increased cardiac output + increased __________ ___________ = increased blood pressure

Aldosterone.

Angiotensin II indirectly acts on adrenal gland to stimulate secretion of ______________

Distal convoluted tubule.

Reabsorption of Na is in the ________ __________ ________

Na channels

Amount of _______ _________ present is limited by amount of Na available to Na+/K+ pump.

Renal outer medullary K

DCT have _________ channels on the lumen membrane.

K secretion

Renal outer medullary K account for _______ ________ into the cell.

SGK

____________ inactivates Nedd4-2.

Nedd4-2.

________ tags Na channels to be removed from the membrane.

Na

High levels of Aldosterone = higher concentration of ____________ channels in the membrane.

K

Aldosterone also promotes _____________ secretion.

Na, K.

Cant save ____ without losing _____.

Plasma osmolality.

Mechanism of maintaining BP has little effect on ________ __________ b/c Na and water are moved along together.

AVP

Hormone the helps in regulating plasma osmolality and regulates urine output.

Hypothalamus,

AVP is synthesized in the ___________.

secretory granules

Once synthesized, AVP is packaged into ___________ _________ and transported down axons to posterior pituitary.

Magnocellular, Parvocellular

AVP is synthesized in two populations of cells, ___________ and ____________ neurons.

Posterior pituitary

Magnocellular projects to ____________ ____________

median emminence

Parvocellular projects to _____________ ___________

Dehydration

AVP Stimuli for Secretion. Blood plasma becomes more concentrated.

increase

AVP Stimuli for Secretion is expressed by __________ in plasma osmolality.

decrease

AVP will cause a dramatic _________ in blood volume (in emergency situation).

Antidiuresis, Vasoconstriction.

Effects of Vasopressin are ___________ and ____________

ADH

___________ concentrates urine to retain water in body and decrease osmolality of the blood.

V2, moderate

Antidiuresis is mediated through high affinity _______ receptors in the kidney at _______ levels of ADH. (day to day regulation).

Vasoconstriction

_____________ helps maintain blood pressure when blood volume drops. (Hemorrhage)

V1, high

Vasoconstriction is mediated by lower affinity ___ receptors that require _________ levels of ADH to be activated.

IP3, Ca

V1 _____ signaling pathway increases ______ which constricts muscle.

a1 adrenergic

V1 has same mechanism as ______ __________ receptors

V2

_____ pathway uses classic cAMP pathway to increase water reabsorption.

Loop of Henle

__________ create high solute concentrations.

High osmotic gradient

_________ _______ _________ allow water to leave.

AVP.

Permeability of collecting ducts to H2O regulated by _______

Dilute

If collecting duct is impermeable to water, you get ____________ urine. (When you are hydrated)

ADH

________ produced during dehydration.

Increases, concentrated.

ADH _________ permeability of collecting ducts to water. Resulting in _________ urine.

Osmosis.

In the collecting ducts, water reabsorbed from filtrate by __________, is leaving concentrated urine

aquaporins

Collecting duct epithelial cells contain vesicles with HIGH concentration of _______ (water channels)

exocytosis

Secretion of ADH causes __________ of vesicles with aquaporins. (Their contents get dumped out of the cell)

Outer

In the process of exocytosis, aquaporin membranes fuse with ______ cell membrane.

Increases permeability

After exocytosis, aquaporin loaded membranes are incorporated into the cell membrane. This greatly _________ ___________ to H2O.

ANF

__________ is secreted by cells in the atrium of the heart and opposes the actions of aldosterone.

BP, increases, Na.

ANF lowers _________,
___________ blood volume,
Increases _____ excretion.

hypervolemia

Activation of stretch receptors in atrium indicates ___________ (too much blood volume)

G-protein coupled, cGMP

AVP uses ____________ receptors that use ___________ as a second messenger.

cGMP

AVP receptors activate ________ dependent kinases.

arterioles, heart,

ANF vasodilates __________
Reduces sympathetic stimulation of __________________. (calms it down)

juxtaglomerular apparatus

Reduces sympathetic stimulation of _________ ____________ so it does not activate to oppose its actions.

glomerular filtration rate, aldosterone, AVP

ANF Increases ______________ ________________ _______________ by relaxing the afferent arterioles - more Na+ and water removed & it directly inhibits ____________secretion by the adrenal gland
Inhibits ____________ secretion by the posterior pituitary.

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