Urine production and regulation

The primary function of the kidney is regulation of _______________

body fluid composition

The kidney is the organ that sorts the substances from the blood for either removal in the urine or return to the _________ .

blood

the funtional units of the kidney

nephrons

The categories of urine formation is divided into three major processes:______________

filtration, tubular reabsorption, and tubular secretion.

_________ occurs when blood pressure non-selectively forces water and other small molecules out of glomerular capillaries and into the Bowman capsule, forming a fluid called filtrate.

Filtration

___________ is the movement of substances from the filtrate across the wall of the nephron back into the blood of the peritubular capillaries

Tubular reabsorption

_____________ is the active transport of solutes across the nephron walls into the filtrate.

Tubular secretion

______________________ , the blood pressure within the glomerulus, moves fluid from the blood into the Bowman capsule.

Glomerular capillary pressure

_________________ , the pressure inside the Bowman capsule, moves fluid from the capsule into the blood

Capsular pressure

_____________ , produced by the concentration of blood proteins, moves fluid from the Bowman capsule into the blood by osmosis.

Colloid osmotic pressure

______________ is equal to the glomerular capillary pressure minus the capsular and colloid osmotic pressures.

Filtration pressure

Three major hormonal mechanisms are involved in regulating urine concentration and volume:

• The renin-angiotensin-aldosterone mechanism.

• The antidiuretic hormone (ADH) mechanism.

• The atrial natriuretic hormone (ANH) mechanism.

Renin and angiotensin help regulate _______________ secretion

aldosterone

_________ , an enzyme, is secreted by cells of the juxtaglomerular apparatuses in the kidneys.

Renin

Renin acts on ________________ , a plasma protein produced by the liver, and converts it to angiotensin I.

angiotensinogen

Angiotensin I is rapidly converted to a smaller peptide called _______________ by angiotensin-converting enzyme (ACE).

angiotensin II

Angiotensin II acts on the adrenal cortex, causing it to secrete _____________

aldosterone.

Aldosterone increases the rate of active transport of Na+ in the_________ convoluted tubules and collecting ducts.

distal

In the absence of aldosterone, large amounts of Na+ ___________ in the nephron and become part of the urine.

remain

A high Na+ concentration in the filtrate causes water to remain in the __________ and increases urine volume.

nephrons

Therefore, when the rate of active transport of Na+ is ______ , urine volume increases, and the urine contains a high concentration of Na+

slow

Because Cl- is attracted by the _________ charge on Na+, Cl- is cotransported with Na+

positive

When blood pressure suddenly decreases or when the concentration of Na+ in the filtrate becomes too low, the kidney releases _________ .

renin

The resultant increase in aldosterone causes an increase in Na+ and Cl- ___________ from the nephrons.

reabsorption

_________________ , secreted by the posterior pituitary gland, passes through the circulatory system to the kidneys.

Antidiuretic hormone (ADH)

__________ regulates the amount of water reabsorbed by the distal convoluted tubules and collecting ducts.

ADH

When ADH levels ___________ , the permeability of the distal convoluted tubules and collecting ducts to water increases, and more water is reabsorbed from the filtrate.

increase

Consequently, an increase in ADH results in the production of a small volume of concentrated _________ . On the other hand, when ADH levels decrease, the distal convoluted tubules and collecting ducts become less permeable to water.

urine

As a result, less water is reabsorbed, and a large volume of dilute urine is ____________

produced

The release of ADH from the posterior pituitary is regulated by the __________ .

hypothalamus

Certain cells of the hypothalamus are sensitive to changes in ________ concentration.

solute

When the solute concentration in the blood increases, action potentials are sent along the axons of the ADH-secreting neurons of the hypothalamus to the posterior pituitary, and ADH is released from the ends of the _________ .

axons

A reduced solute concentration in the blood causes inhibition of ________ release.

ADH

________________ is secreted from cardiac muscle cells in the right atrium of the heart when blood pressure in the right atrium increases above normal.

Atrial natriuretic hormone (ANH)

___________ acts on the kidney to decrease Na+ reabsorption.

ANH

The increased loss of Na+ and water as urine reduces the blood volume and the ______________

blood pressure.