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Biology - Year 2 (Eduqas) > Chapter 12 - Homeostasis and the Kidney. > Flashcards

Chapter 12 - Homeostasis and the Kidney. Flashcards

1
Q

What is homeostasis?

A

It is the maintenance of a constant environment.

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2
Q

What is a negative feedback mechanism?

A

A change in a system produces a second change, which reverses the first change.

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3
Q

What is excretion?

A

It’s the removal of wastes made by the body

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4
Q

What are the 2 main functions of the kidneys?

A
  • Excretion, removal of nitrogenous metabolic waste.
  • Osmoregulation, control of the water potential of the body’s fluids by regulating the water content and the solute concentration.
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5
Q

Where and why is urea made?

A

Its made in the liver after excess amino acids are deaminated. Other nitrogen-containing waste products can also be converted to urea.

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6
Q

What are the 3 main regions of the kidney?

A
  • Outer cortex.
  • Inner medulla.
  • Renal pelvis.
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7
Q

Where does the kidney receive blood from?

A

Receives it from a renal artery and returns blood to the general circulation in a renal vein.

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8
Q

Where does ultrafiltration occur?

A

At the Bowman’s capsule.

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9
Q

What is the capillary network surrounding the loop of henle called?

A

Vasa recta.

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10
Q

Why is there a high pressure in the glomerulus?

A
  • The hearts contraction increases the pressure of arterial blood.
  • The afferent arteriole has a wider diameter than the efferent arteriole.
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11
Q

What is the selective barrier that acts like a sieve during ultrafiltration?

A

The basement membrane of the podocytes.

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12
Q

What is within the glomerular filtrate?

A
  • Water.
  • Glucose.
  • Salts.
  • Urea.
  • Amino acids.
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13
Q

What is too large to pass through the basement membrane?

A
  • Red blood cells.

- Large plasma proteins.

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14
Q

What is selective reabsorption?

A

The uptake of specific molecules and ions from the glomerular filtrate in the nephron back into the bloodstream.

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15
Q

Where does selective reabsorption take place?

A

Takes place in the proximal convoluted tubule (PCT).

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16
Q

What features of the PCT make it suitable for selective reabsorption?

A
  • Large S.A.
  • Cubioidal epithelial cells in its walls with a S.A. increased by microvilli.
  • Many mitochondria providing the ATP for active transport.
  • A close association with capillaries.
  • Tight junctions between the cells of PCT epithelium.
17
Q

How does selective reabsorption reabsorb the glucose and amino acids?

A

By co-transport. Na+ is actively transported out of the epithelial cells decreasing the concentration gradient. A glucose molecule and 2 Na+ ions bind to a transporter protein in a cuboidal epithelium cell membrane and are carried into the cell by facilitated diffusion. Sodium diffuses into the capillary down its concentration gradient providing the energy for the secondary active transport of glucose into the blood, against its concentration gradient.

18
Q

How and Where is most of the water reabsorbed from the glomerular filtrate?

A

About 90% is reabsorbed in the PCT by osmosis. This happens because the reabsorbed ions lower the water potential of the blood.

19
Q

What condition may cause glucose to be lost in the urine?

A

Diabetes, Type 1 and 2.

20
Q

How does the loop of henle reabsorb some of the water from the glomerular filtrate?

A

The ascending limb actively transport sodium and chloride ions out of the filtrate into the tissue fluid which makes the medulla have a lower water potential. The walls of the descending limb are permeable to water so water diffuses out by osmosis down a water potential gradient into the vasa recta.

21
Q

What is the hormone that causes the DCT and the collecting duct to become permeable to water?

A

ADH (Antidiuretic hormone).

22
Q

Where is Antidiuretic hormone produced and what effect does it have?

A

It is produced in the hypothalamus and secreted by the posterior pituitary gland. It increases permeability of the cells of the distal convoluted tubule and collecting duct by causing aqua porins to fuse with the membrane, increasing water reabsorption.

23
Q

How does osmoregulation work?

A

-Osmoreceptors in the hypothalamus detect a reduced water potential.
-ADH is released, increasing the permeability of the walls of the DCT and collecting duct to water.
-More water is reabsorbed into the region of high solute concentration.
-More water is reabsorbed from the medulla into the vasa recta.
-Water potential of blood is restored to normal.
The opposite occurs if the water potential of the blood decreases.

24
Q

What are the commonest causes of kidney failure?

A
  • Diabetes.
  • High blood pressure (Prevents ultrafiltration).
  • Auto-immune disease.
  • Infection.
  • Crushing injuries.
25
Q

What treatments are used to reduce the concentration of waste products and control the volume of body fluids if the kidneys are damaged?

A
  • Reducing intake of certain nutrients.
  • Using drugs to reduce blood pressure.
  • Regulating the concentration of dissolved potassium and calcium.
  • Dialysis.
  • Kidney transplant.
26
Q

What are the 2 forms of dialysis?

A
  • Haemodialysis.

- CAPD (Continuous ambulatory peritoneal dialysis).

27
Q

How does Haemodialysis work?

A

Blood is taken from and artery and run through long, narrow fibres made of selectively permeable dialysis tubing which are surrounded by the dialysis fluid. The pores in the tubing let molecules out into the dialysis fluid.

28
Q

How does CAPD work?

A

The patient drains a bag of dialysis fluid through a catheter in the abdomen, into the body cavity. The peritoneum is the membrane lining the body cavity and it has a rich supply of capillaries so it acts as the dialysis membrane. The fluid is then drained from the abdomen.

29
Q

Why must the recipient of a donated organ take immunosuppressant’s?

A

To prevent the body attacking the donated organ but because it suppresses the immune system, the patients are more susceptible to infection.

30
Q

Where is the transplanted kidney placed?

A

In the lower abdomen, attached to the iliac artery and vein.

31
Q

What are the 3 forms that ammonia can be excreted as and which organisms excrete which?

A
  • Ammonia, most aquatic organisms.
  • Uric acid, birds reptiles and insects (very little water is needed for its excretion).
  • Urea, mammals.
32
Q

What are the 2 types of nephron and what are their differences?

A
  • Cortical nephrons, short loop of henle.

- Juxtamedullary nephrons, long loop of henle.

33
Q

What is metabolic water?

A

Water produced from the oxidation of food reserves.

Biology - Year 2 (Eduqas) (14 decks)

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