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Biology Section 6 - Organisms Respond to Changes in their Environment > Homeostasis (Chapter 16) > Flashcards

Homeostasis (Chapter 16) Flashcards

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1
Q

Define Homeostasis

A

Maintenance of a constant internal environment. Maintain temperature so that enzymes can work at their optimum temperature.

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2
Q

Define Positive Feedback

A

Taking something further from its setpoint value. Encourages more of something to happen.

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3
Q

Define Negative Feedback

A

Returning something to its set point.

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4
Q

What is the function of the pancreas?

A

Controls blood glucose levels.

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5
Q

What group of cells make up the pancreas?

A

Islets of Langerhans

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6
Q

What cells make glucagon?

A

Alpha cells

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7
Q

What cells make insulin?

A

Beta cells

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8
Q

Which cells are glucagon made in?

A

Alpha cells

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9
Q

Which cells are insulin made in?

A

Beta cells

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10
Q

What is the main factor which affects blood glucose experiment?

A

If a person has eaten previously

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11
Q

What happens when blood glucose too high?

A

Insulin is made

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12
Q

Define Glycogenolysis

A

Breakdown of glycogen

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13
Q

Define Gluconeogenesis

A

Making new glucose (e.g. liver making glucose from glycerol and amino acids)

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14
Q

Define Glycogenesis

A

Making glycogen by converting glucose

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15
Q

Describe the stages of glucose regulation

A

1) Insulin binds to glycoprotein receptor on target cell (e.g. on liver) changing tertiary structure.
2) Leads to more transport protein for glucose becoming active by opening them.
3) More glucose enters the cells (from blood which lowers concentration in the blood)
4) Insulin increases activity of enzymes which convert glucose to glycogen (glycogenesis)
5) It also causes vesicles containing glucose transporters to fuse with cell membranes by exocytosis - allowing for diffusion of glucose.

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16
Q

What happens if blood glucose is too low?

A

Glucagon made

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17
Q

How does glucagon activate enzymes?

A

Attaches to receptors on target cells to activate enzymes by:

A) Convert stored glycogen to glucose (glycogenolysis) - uses messenger model. Stored in liver so this organ has lots of glucagon receptors.

B) Convert glycerol /amino acids/fatty acids to glucose (gluconeogenesis)

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18
Q

Describe the difference between type 1

and type 2 diabetes

A

Type 1 - Person makes no insulin - tends to be younger sufferers

Type 2 - Receptors don’t respond to insulin - diet, lack of exercise can be triggers

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19
Q

What is the second messenger model?

A

Way adrenaline and glucagon increase blood sugar levels

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20
Q

Describe the stages of the second messenger model

A

1) Hormone binds to receptor sites and activates enzyme (by changing shape of protein)
2) This makes the enzyme cyclic AMP (acts as a second messenger) from ATP.
3) This binds to protein kinase enzyme, changing shape and activating it. Leads to glycogenolysis.

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21
Q

What drug is used to treat T2 diabetes and how does it work?

A

Metformin

Increases a cell’s sensitivity to insulin, so more insulin binds to receptors, stimulating uptake of glucose by transport proteins (GLUT 4) or activates enzymes that convert glucose to glycogen.

22
Q

How does metformin inhibit adenylate cyclase?

A
  • Less/no ATP converted to cAMP
  • Less/no cAMP binding to protein kinase
  • Less/no protein kinase activated
  • Less/no glycogenolysis occurring
23
Q

Describe how the body increases the volume of urine

A

1) Water potential of filtrate/tubule decreased
2) Less water reabsorbed by osmosis through filtrate/tubule
3) Collecting duct is where most osmosis occurs

24
Q

Where are glucose and water reabsorbed?

A

The proximal convoluted tubule of a nephron

25
Q

How is glucose reabsorbed?

A

Facilitated diffusion and active transport

26
Q

How is water reabsorbed?

A

Down water potential gradient

27
Q

Describe the process of ultrafiltration

A

1) High blood/hydrostatic pressure
2) Two named substances (e.g. water, glucose, ions, urea) pass out
3) Through small gaps/pores/fenestrations in capillary endothelium
4) Through capillary basement membrane

28
Q

What is shown when the medulla is thicker?

A

More concentrated urine and longer loop of Henle

29
Q

What is shown by a longer loop of Henle?

A

Increase in sodium ions in medulla so water potential gradient maintained for longer so more water reabsorbed from loop and collecting duct.

30
Q

What is the optimum point?

A

The point in which the system operates best.

31
Q

What is the job of a receptor?

A

Detects deviation from the optimum point.

32
Q

What is the job of a coordinator?

A

Co-ordinates information from a receptor.

33
Q

What is the job of an effector?

A

Brings changes needed to return the system to the optimum point.

34
Q

Describe a feedback loop

A

1) Optimum point changes
2) The receptor detects a deviation from the optimum point.
3) The co-ordinator co-ordinates information from the receptor.
4) The effector creates the changes that return the body to the optimum point.

35
Q

What is the feedback mechanism?

A

When a receptor detects a stimulus created by the change to the system and the effector brings about the appropriate response.

36
Q

Define osmoregulation:

A

The homeostatic control of the water potential of the blood.

37
Q

What is the fibrous capsule?

A

The outer membrane that protects the kidneys.

38
Q

What is the kidney cortex?

A

A lighter coloured outer region made up of the renal (Bowman’s) capsules, convoluted tubules and blood vessels.

39
Q

What is the kidney medulla?

A

A darker coloured inner region made up of loops of Henle, collecting ducts and blood vessels.

40
Q

What is the renal pelvis?

A

A funnel-shaped cavity that collects urine into the ureter.

41
Q

What is the ureter?

A

A tube that carries urine to the bladder.

42
Q

What is the renal artery?

A

Supplies the kidney with blood from the heart via the aorta.

43
Q

What is the renal vein?

A

Returns blood to the heart via the vena cava.

44
Q

What is the renal (Bowman’s) capsule?

A

The closed end at the start of the nephron. It is cup-shaped and surrounds a mass of blood capillaries knowm as glomerulus. The inner layer of the renal capsule is made up of specialised cells called podocytes.

45
Q

What is the proximal convoluted tubule?

A

A series of loops surrounded by blood capillaries. Its walls are made up of epithelial cells that have microvilli.

46
Q

What are loop of Henle?

A

A long, hairpin loop that extends from the cortex into the medulla of the kidney and back again. It is surrounded by blood capillaries.

47
Q

What is distal convoluted tubule?

A

A series of loops surrounded by blood capillaries. Its walls are made up of epithelial cells, but it is surrounded by fewer capillaries than the proximal tubule.

48
Q

What is the collecting duct?

A

A tube into which a number of distal convoluted tubules from a number of nephrons empty. It is lined by epithelial cells and becomes increasingly wide as it empties into the pelvis of the kidney.

49
Q

What is the affrent arteriole?

A

A tiny vessel that arises from the renal artery and supplies the nephron with blood. The arteriole enters the renal capsule of the nephron where it forms the glomerulus.

50
Q

What is the glomerulus?

A

A many-branched knot of capillaries from which fluid is forced out of the blood. The glomerular capillaries recombine to form the efferent arteriole.

51
Q

What is the efferent arteriole?

A

A tiny vessel that leaves the renal capsule. It has a smaller diameter than the afferent arteriole so causes an increase in blood pressure within the glomerulus. The efferent arteriole carries blood away from the renal capsule and later branches to form the blood capillaries.

52
Q

What are the renal blood capillaries?

A

A concentrated network of capillaries that surround the proximal convoluted tubule and form where they reabsorb mineral salts, glucose, and water. These capillaries merge together into venules that then merge together to form the renal vein.

Biology Section 6 - Organisms Respond to Changes in their Environment (3 decks)

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