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Biology Module 3 > Homeostasis > Flashcards

Homeostasis Flashcards

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1
Q

What are the main metabolic waste products in mammals?

A
  • Carbon dioxide
  • Nitrogenous waste
  • Bile pigments
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2
Q

How are bile pigments formed?

A

Breakdown of haemoglobin from old red blood cells in the liver.

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3
Q

What colours the faeces?

A

Bile pigments

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4
Q

How is nitrogenous waste formed?

A

Breakdown of excess amino acids by the liver.

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5
Q

How is oxygenated blood supplied to the liver?

A

Hepatic artery

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6
Q

How is deoxygenated blood returned to the heart from the liver?

A

Hepatic vein

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7
Q

What is the role of the hepatic portal vein?

A

Supplies blood to the liver loaded with the products of digestion from the intestines.

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8
Q

What are the features of hepatocytes?

A

Large nuclei
Prominent Golgi apparatus
Lots of mitochondria

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9
Q

What happens in sinusoids?

A

Blood from the hepatic artery and hepatic vein mix.

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10
Q

What surrounds sinusoids?

A

Hepatocytes

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11
Q

What is the purpose of mixing of the blood in the sinusoids?

A

Increases oxygen content of blood from the hepatic portal vein so the hepatocytes have enough oxygen.

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12
Q

What is the purpose of the Kupffer cells in the sinusoids?

A

Ingest foreign particles.

Help protect against disease.

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13
Q

What do hepatocytes secrete?

A

Bile

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14
Q

Why do hepatocytes secrete bile?

A

Secrete bile into canaliculi and from these the bile drains into bile ducts which take it to the gall bladder.

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15
Q

Where does detoxification happen?

A

Liver

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16
Q

What is transamination?

A

Conversion of one amino acid into another.

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17
Q

Why is transamination important?

A

Diet doesn’t always contain the required balance of amino acids.

18
Q

What is deamination?

A

Removal of an amine group from a molecule.

19
Q

What is ultrafiltration?

A

1) Blood from the renal artery is supplied to the glomerulus from the afferent arteriole.
2) Blood leaves through the narrower efferent arteriole which builds up pressure.
3) So blood is passed out through the capillary wall and then through the basement membrane. Red blood cells and proteins are retained in the capillary as they are too large.

20
Q

What are the role of podocytes in ultrafiltration?

A

Acts as an additional filter. They have extensions called pedicles that wrap around capillaries forming slits to ensure ay escaped large molecules from the basement membrane don’t pass into the tubule.

21
Q

What are the steps of reabsorption which occur in the PCT?

A

All glucose, amino acids, vitamins and hormomes are actively transported back into the blood. About 85% of Na ions move back by AT and Cl ions by passive diffusion.

22
Q

What are the adaptations of cells lining the PCT?

A
  • Microvilli

- Many mitochondria

23
Q

What are the steps of reabsorption which occur in the loop of Henle?

A

Descending limb-
Lower part is permeable to water, so water moves out by osmosis. Impermeable to ions. At the hairpin, the fluid is very concentrated.

Ascending limb-
In the first section, many ions move out by diffusion. In the second part, ions are moved out by AT. Impermeable to water. So the fluid becomes increasingly dilute.

24
Q

What does the loop of Henle act as?

A

A countercurrent multiplier

25
Q

What are the roles of the DCT in reabsorption?

A

If the body lacks salts, ions will be pumped out down an electrochemical gradient.

The cells lining the DCT have many mitochondria for AT.

The permeability of the walls to water vary with the levels of ADH.

26
Q

What is the main purpose of the DCT and collecting duct?

A

Balancing of water needs.

27
Q

What happens when water is in short supply?

A
  • Detected by osmoreceptors in the hypothalamus.
  • Send nerve impulses to the posterior pituitary gland which releases ADH.
  • ADH is picked up by receptors in the cells lining the collecting duct and increases the permeability to water.
  • So water enters the blood by osmosis.
28
Q

What happens when there is an excess of water in the body?

A
  • Change is detected by the osmoreceptors in the hypothalamus.
  • Nerve impulses to the posterior pituitary are reduced so release of ADH is inhibited.
29
Q

What is the mechanism of ADH?

A
  • Vesicles in the cells lining the collecting duct fuse with the cell surface membranes on the side of the cell in contact with the tissue fluid of the medulla.
  • Membranes of these vesicles contain aquaporins and make a cell surface membrane permeable to water.
  • This allows for the movement of water in the blood by osmosis.
30
Q

What is the ornithine cycle?

A

Ammonia combines with carbon dioxide to form urea and water.

31
Q

What is the purpose of the ornithine cycle?

A

Ammonia is too toxic to be excreted directly.

32
Q

What is the process of deamination?

A

NH2 are removed from excess amino acids forming ammonia and organic acids.

33
Q

What is done with the organic acids formed in deamination?

A

Used in respiration
Stored as glycogen
Converted to carbohydrate

34
Q

Which dialysis has AT?

A

Peritoneal

35
Q

Where does peritoneal dialysis take place?

A

Inside the body

36
Q

What is an advantage of peritoneal dialysis?

A

Can take place at home

37
Q

How does peritoneal dialysis work?

A

1) Dialysis fluid is introduced into the body using a catheter.
2) Left for hours so urea and excess mineral ions pass out of blood capillaries into the tissue fluid across the peritoneal membrane into the dialysis fluid.

38
Q

What machinery does haemodialysis use?

A

Dialysis machine

39
Q

How does haemodialysis work?

A

1) Blood leaves body from artery and flows into machine.
2) Blood flows between partially permeable dialysis membranes which mimic the basement membrane.
3) Patients lose excess mineral ions and urea.

40
Q

How is it ensured that patients don’t lose useful substances in haemodialysis?

A

Dialysis fluid contains normal plasma levels of glucose.

41
Q

How is a steep concentration gradient of urea built up in haemodialysis?

A

Dialysis fluid doesn’t contain any urea.

Biology Module 3 (4 decks)

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