Lecture 34 Countercurrent multiplier and urinary regulation

The _______________ of the loop of Henle generates strong osmotic gradients in the medullary interstitial fluid.

countercurrent multiplier effect

The ascending limb has high _____________ (1) activity, but is very impermeable to _______________(2).

What is the term for 1?

Na+/K+-ATPase

The ascending limb has high _____________ (1) activity, but is very impermeable to _______________(2).

What is the term for 2?

water (H2O)

The descending limb is very impermeable to __________(1), highly permeable to ________________(2).

What is the term for 1?

solutes

The descending limb is very impermeable to __________(1), highly permeable to ________________(2).

What is the term for 2?

water (H2O)

There is an osmolarity gradient in the kidney interstitial fluid, such that the fluid deep in the medulla is ____________ relative to most body fluids.

hyperosmotic (very concentrated)

The ___________ structure of the loop allows for the generation of the interstitial osmolarity gradient.

countercurrent

In the steady state, water and solutes move into the vasa recta by bulk flow at basically the ___________ that they move into the interstitial fluid by active transport/osmosis?

same rate

The interstitial fluid volume remains steady and the osmolarity gradient is maintained due to the _____________(1) of water and solutes reabsorbed from the loop of Henle being returned into the capillaries of the ___________(2) where they are returned to circulation.

What is the term for 2?

vasa recta

The interstitial fluid volume remains steady and the osmolarity gradient is maintained due to the _____________(1) of water and solutes reabsorbed from the loop of Henle being returned into the capillaries of the ___________(2) where they are returned to circulation.

What is the term for 1?

bulk flow

The fluid that enters the collecting duct is very ___________.

Hyposmotic (dilute)

The interstitial osmolarity gradient favors water________ from the urine as it passes into the renal pelvis through the collecting ducts, concentrating the urine.

reuptake

Reabsorption of H2O in the collecting duct is controlled by an antidiuretic hormone aka _________________.

vasopressin

Reabsorption of Na+ in the distal tubule and collecting duct, is controlled by the ___________________________.

renin-angiotensin-aldosterone system (RAAS system)

High vasopressin signaling is associated with ________ reabsorption.

more H20

High aldosterone signaling is associated with ___________ reabsorption.

more Na+

Vasopressin can directly causes increased plasma volume and increased ________________.

blood pressure

The RAAS system can indirectly cause more _________________(1) and thus increased _______________(2) and increased _________________(3).

What is the term for 1?

H20 reabsorption

The RAAS system can indirectly cause more _________________(1) and thus increased _______________(2) and increased _________________(3).

What is the term for 2?

plasma volume

The RAAS system can indirectly cause more _________________(1) and thus increased _______________(2) and increased _________________(3).

What is the term for 3?

blood pressure

Hypothalamic _______________ directly monitor the osmolarity of body fluids.

osmoreceptors

Would osmoreceptors increase or decrease vasopressin release when osmolarity is high in body fluids?

increase

Would osmoreceptors increase or decrease vasopressin release when osmolarity is low in body fluids?

decrease

The release of vasopressin is stimulated when baroreceptors detect a decrease in __________

blood pressure

By increasing sodium reabsorption, the hormone __________ indirectly increases blood volume and pressure.

Aldosterone

The collecting duct can also operate in a state where water reabsorption is __________, allowing for the production of dilute urine when there is low vasopressin.

reduced

Vasopressin aka ADH (Anti Diuretic Hormone): prevents the state of __________(production of copious dilute urine)

diuresis

An increase in the osmolarity of extracellular fluid stimulates __________ in the hypothalamus to detect and respond.

Osmoreceptors

The _____________ responds to increased osmolarity by secreting vasopressin(ADH).

posterior pituitary gland

Vasopressin increases __________ reabsorption in the kidneys, reducing water __________.

Water; excretion

The conservation of body water helps reduce __________ in extracellular fluid.

osmolarity

Vasopressin regulates the shuttling of aquaporins into the ______ membranes of duct epithelial cells via a G-protein coupled signaling pathway

apical

When vasopressin is low aquaporins are put into _______ in the membrane.

vesicles

Low water intake (dehydration) increases __________ in the blood, stimulating osmoreceptors in the hypothalamus.

Plasma osmolality

In response to dehydration, the posterior pituitary increases the release of __________.

Vasopressin

Overhydration causes __________(1) plasma osmolality, which reduces ADH release and increases __________ (2)water excretion.

What is the term for 1?

decreased

Overhydration causes __________(1) plasma osmolality, which reduces ADH release and increases __________ (2)water excretion.

What is the term for 2?

urinary

The primary role of osmoreceptors in the hypothalamus is to detect changes in __________.

Plasma osmolality

A decrease in _____________ would activate the RAAS system.

MAP (Mean Arterial Pressure)

Renin is released from the __________ cells of the afferent arteriole of the kidney.

Juxtaglomerular

Renin acts on __________, a protein produced by the liver, to form angiotensin I.

Angiotensinogen

Angiotensin I is converted to angiotensin II by __________ in the capillary endothelial cells.

ACE (angiotensin-converting enzyme)

Angiotensin II stimulates the adrenal cortex to release __________, which promotes sodium and water retention.

Aldosterone

In the distal tubule, aldosterone increases reabsorption of __________ and __________, leading to increased blood volume.

Sodium (Na⁺); water (H₂O)

The activation of the RAAS system results in an increase in blood volume and __________, which restores MAP

pressure

Aldosterone increases Na+ reabsorption (and K+ secretion) by altering ____________________ in the membranes of nephron epithelial cells.

transport protein densities

__________ is the main nitrogenous waste compound in mammals.

Urea

Epithelial cells in this region have an increased density of apical membrane aquaporins when vasopressin secretion is high.

Collecting duct

Epithelial cells in this region have an increased density of basolateral membrane sodium-potassium pumps when aldosterone secretion is high.

Distal convoluted tubule

Epithelial cells in this region engage in significant reabsorption of nutrients such as glucose.

Proximal convoluted tubule

Epithelial cells in this region have gaps between them that allow significant paracellular movement of water and solutes.

Bowman's capsule

Epithelial cells in this region have low densities of basolateral membrane sodium-potassium pumps.

Descending limb of the loop of Henle