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Biology is for cool people > 16. homeostasis > Flashcards

16. homeostasis Flashcards

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1
Q

What is the optimum core temp of humans?

A

37 degs

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2
Q

What happens to enzymes if body temp exceeds optimal temperature?

A

H-bonds of active site break, altering active site shape.

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3
Q

what effect does an increase in glucose concentration (in the blood) have on body cells?

A

water moves out of body cells by osmosis

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4
Q

What is glycogenesis?

A

Liver cells produce enzymes that convert glucose into glycogen.

Happens when glucose concentration is too high

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5
Q

What is glycogenolysis?

A

Enzymes from liver cells hydrolyse glycogen to glucose

…in response to low blood glucose concentration

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6
Q

What is gluconeogenesis?

A

liver cells form glucose from glycerol and amino acids

…in response to blood glucose concentration

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7
Q

where are beta cells located?
what do they detect?

A
  • pancreas, islets of langerhans
  • high blood glucose concentration
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8
Q

What do beta cells secrete?

A
  • insulin
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9
Q

What does insulin do?

A
  • binds to receptors on muscle cells,
  • causes change in tertiary structure of transport proteins
  • uptake of glucose by muscle cells increase (fac diff)
  • increase rate of respiration
  • insulin binds to receptors on liver cells
  • liver cells produce enzymes that activate glucose to glycogen.

Both processes decrease blood glucose concentration.

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10
Q

Describe the importance of glucose to the water potential in blood.

A
  • more glucose = lower water potential;
  • = water moves out of tissue into blood by osmosis
  • increase in blood pressure, cells dehydrated
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11
Q

What is normal blood glucose concentration?

A

90mg

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12
Q

Where are changes in blood glucose levels detected?

A

The pancreas

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13
Q

What two reactions take place respond to low blood glucose?

A

Glycogenolysis
Gluconeogenesis

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14
Q

What is the effect of an increase in blood glucose on the CELLS in the body?

A

Water moves out by osmosis

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15
Q

What happens to respiration if glucose concentration decreases?

A

Not enough glucose for respiration, rate of respiration decreases.

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16
Q

describe the action of glucagon.

A
  • Attach to surface of liver cells
  • Activating enzymes involved in conversion of glycogen to glucose
  • Activating enzymes involved in the conversion of GLYCEROL and AMINO ACIDS into glucose.
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17
Q

What factors can increase blood glucose concentration?

A
  • diet (glucose absorbed)
  • glycogenolysis
  • gluconeogenesis
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18
Q

What three main hormones work to maintain glucose concentration?

A
  • insulin
  • glucagon
  • adrenaline
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19
Q

What cells detect a rise in blood glucose concentration?

A

B (beta) cells

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20
Q

Where (specifically) are B cells found?

A

The islet of langerhans in the pancreas

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21
Q

Where (specifically) are A cells found?

A

The islet of langerhans in the pancreas

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22
Q

What cells detect a decrease in glucose concentration?

A

A cells

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23
Q

What hormone do A cells secrete?

A

glucagon

24
Q

What hormone do B cells secrete?

A

insulin

25
Q

Summarize the overall effect of both insulin and glucagon.

A

Insulin - decrease blood glucose levels,

glucagon - increase blood glucose levels,

26
Q

Define homeostasis

A

The control of internal conditions of body in response to stimuli.

27
Q

Why must PH levels be regulated?

A

Affects ionic bonds of tertiary structure, ( + active site) enzyme unable to catalyse reaction(s)

28
Q

Name and explain what happens at the PCT of the nephron

A

SELECTIVE REABSORPTION,85% of filtrate back into the blood, leaving urea and ions in filtrate.

  • Sodium/potassium pump actively transports sodium out of PCT cell
  • Co-transport of glucose and sodium into PCT cell from lumen,
  • glucose diffuse out of PCT cell
29
Q

Name and explain what happens at the glomerulus of the nephron.

A

ULTRAFILTRATION

Blood enters through afferent arteriole, small capileroe establish hydrostatic pressure. Water and small molecules are forced out of blood into filtrate inside renal capsule.

large proteins and blood cells leave through efferent arteriole.

30
Q

How is the PCT adapted for its function?

A

Microvilli - large surface area

Lots of mitochondria - energy for active transport

31
Q

What does PCT and DCT stand for?

A

Proximal convoluted tube, Distal convoluted tube.

32
Q

How much glucose is reabsorbed at the PCT?

A

all of it.

33
Q

Suggest what happens at the loop of henle. (don’t explain)

A

Maintenance of sodium ion gradient to enable reabsorption of water.

34
Q

Contrast the ascending and descending limbs of the loop of henle

A

Descending limb is permeable to water, much thinner.

Ascending limb, Sodium ions are actively transported out.

35
Q

Explain how the sodium ion gradient is maintained at the loop of henle. (4)

A

1) Sodium ions are actively transported out of ascending limb,

2) Accumulation of ions outside of nephron lowers the water potential.

3) Water moves by osmosis out of the descending loop and then into blood capillaries.

4) At the base of ascending limb, sodium ions can now diffuse out of loop by diffusion.
… because water potential is lower in the loop at the base (water has moved ouy)

36
Q

Name and explain what happens at the DCT and collecting duct of the nephron.

A

REABSORPTION OF WATER

  • filtrate at DCT is very dilute
  • Medulla is concentrated, more water out of filtrate.
  • What is left is transported to form urine.
37
Q

Why do Desert animals have a longer loop of henle?

A

More sodium ions transported out, more negative water potential, water reabsorbed into the blood.

38
Q

Draw and label a nephron.

A
  • Afferent and efferent arterioles
  • Glomerulus
  • renal capsule
  • PCT
  • Descending and Ascending loop of henle
  • DCT
  • collecting duct
  • Cortex
  • Medulla
39
Q

Explain the action of adrenaline in the liver. (4)

A
  • Adrenaline binds to a transmembrane receptor on liver cell
  • causing protein on the other side (adenyl cyclase) to change shape, activating it.
  • activated adenyl cyclase converts ATP to cAMP
  • cAMP activates kinase, catalyzing glycogen to glucose
40
Q

Contrast the causes of type 1 and 2 diabetes.

A

Type one - body CANNOT produce insulin.

Type two - insulin IS made (can be deficient) but glycoproteins are not responsive to it.

41
Q

What is meant by negative feedback?

A

Deviations from optimal conditions (in both ways) causes a response that restores conditions.

42
Q

HyPERtonic blood has…

A

too low water potential.
too many solutes

43
Q

Where are osmoreceptors located?

A

hypothalamus - brain

44
Q

What happens to osmoreceptors when water potential is too low?

A

water leaves osmoreceptors, more ADH is produced by hypothalamus.

45
Q

Where is ADH secreted and produced?

A

Secreted by the posterior pituitary, into blood.
Produced by osmoreceptors.

46
Q

What is ADH’s ‘target organ’ and what happens when it reaches it?

A

The kidney, increases permeability of DCT and collecting duct. causes aquaporin-containing vesicles to fuse to membrane by the activation of phosphorylase by ADH.

47
Q

What happens to osmoreceptors when water potential is too high?

A

water enters osmoreceptors, less ADH produced by hypothalamus.

48
Q

summarize negative feedback response to hypotonic blood

A
  • low water potential
  • water moves out of osmoreceptors, more ADH is produced by hypothalamus
  • ADH secreted by posterior pituitary gland
  • DCT and collecting duct more permeable to water (more aquaporins)
  • more water reabsorbed into blood.
  • concentrated urine
49
Q

explain the action of adrenaline (secondary messenger)

A
  • attach to receptors on the surface of target cells
  • G protein is activated
  • ATP to cAMP
  • cAMP activates an enzyme that can hydrolyse glycogen into glucose
  • cAMP is secondary messenger
50
Q

Explain the action of glucagon (secondary messenger model)

A
  • glucagon attaches to receptors on surface of target cells (liver / muscles)
  • activation of adenylyl cyclase
  • ATP into cAMP
  • cAMP is ‘second messenger’
  • activates kinase protein
  • which catalyses glycogen into glucose
51
Q

glucogenogenesis is…
takes place in the…

A

amino acids to glucose, in the liver.

52
Q

adrenaline is released by…

A

adrenal gland

53
Q

To move exit the bloodstream at the glomerulus, substances must be…

A

Small enough to fit through gaps in epithelial and podocyte cells to fit through the basement membrane

54
Q

fancy words for shrivel and burst

A

cenate, lysis

55
Q

when blood has too high water pot it is described as

A

hypotonic
few solutes

56
Q

Explain how insulin increases the uptake of glucose.
don’t refer to glycogenesis

A
  • attaching to receptors on the surface of target cells, change in shape, more facilitated diffusion
  • more protein carriers are incorporated in membrane (vesicles containing glucose channels)

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