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Biology > Homeostasis > Flashcards

Homeostasis Flashcards

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1
Q

What is homeostasis?

A

Internal environment is maintained

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2
Q

Why is it important that core temperature remains stable?

A

Maintain a stable rate of enzyme controlled reactions and prevent damage membranes
Low temperature= insufficient kinetic energy
High temperature= enzymes denature

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3
Q

Why is it important that blood pH remains stable?

A

Maintain stable rate of enzyme controlled reactions

Acidic pH = shape of active sites change

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4
Q

Why is it important that blood glucose remains stable?

A

Maintain a constant blood water potential- stops osmotic lysis
Maintain a constant concentration of respiratory substrate

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5
Q

What is negative feedback?

A

Self regulatory mechanisms return internal environment to optimum when there is fluctuations

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6
Q

What is positive feedback?

A

A fluctuation triggers changes that result in an even greater deviation from the normal level

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7
Q

Outline the stages involved in negative feedback

A

Receptors detect changes > Coordinator > effector > receptors detect change is back to normal

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8
Q

Why is there a lag time between hormone production and response by an effector?

A

It takes time to:
Produce the hormone
Transport the hormone in the blood
Cause required change to the target protein

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9
Q

Name the factors that affect blood glucose concentration?

A

Amount of carbohydrate in diet
Rate of glycogenolysis
Rate of gluconeogenesis

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10
Q

What is glycogenesis?

A

Liver converts glucose into glycogen

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11
Q

What is glycogenolysis?

A

Liver hydrolyses glycogen into glucose which can diffuse into blood

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12
Q

What is gluconeogenesis?

A

Liver converts glycerol and amino acids into glucose

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13
Q

Outline the role of glucagon when blood glucose concentration decreases

A
  1. a cells in Islets of Langerhans in pancreas detect decrease and secrete glucagon into bloodstream
  2. Glucagon binds to surface cell receptors on liver cells and activates enzymes for glycogenolysis and gluconeogenesis
  3. Glucose diffuses from liver into blood stream
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14
Q

Outline the role of adrenaline when blood glucose concentration decreases

A
  1. Adrenal gland produces adrenaline. It binds to surface receptors on liver cells and activates enyzmes for glycogenolysis
  2. Glucose diffuses from liver into bloodstream
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15
Q

Outline what happens when blood glucose concentration increases

A
  1. B cells in islets of langerhans in pancreas detect increase and secrete insulin into bloodstream
  2. Insulin binds to receptor cells on target cells to increase glucose uptake and activate enzymes for glycogenesis
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16
Q

Describe how insulin leads to a decrease in blood glucose concentration

A

Increases permeability of cells to glucose
Increases glucose concentration gradient
Triggers inhibition of enzymes for glycogenolysis

17
Q

How does insulin increase permeability of cells to glucose?

A

Increases number of glucose carrier proteins

Opens more glucose carrier proteins

18
Q

How does insulin increase the glucose concentration gradient?

A

Activates enzymes for glycogenesis in liver and muscles

Stimulates fat synthesis in adipose tissue

19
Q

Use the secondary messenger system to explain how glucagon and adrenaline work

A
  1. Hormone receptor complex forms
  2. Change to receptor activates G-Protein
  3. Activates adenylate cyclase which converts ATP to cyclic AMP
  4. cAMP activates protein kinase A pathway
  5. Results in glycogenolysis
20
Q

Explain the causes of type 1 diabetes and how it can be controlled

A

The body cannot produce insulin e.g due to an autoimmune response which attacks B cells in Islets of Langerhans
Treat by injecting insulin

21
Q

Explain the causes of type 2 diabetes and how it can be controlled

A

Glycoprotein receptors are damaged or become less responsive to insulin
Correlation with poor diet/obesity
Treat by controlling diet and exercise regime

22
Q

Name some symptoms of diabetes

A

High blood glucose concentration
Glucose in urine
Blurred vision
Sudden weight loss

23
Q

What is osmoregulation?

A

Control of blood water potential

24
Q

Describe the structure of the kidney

A 
Fibrous capsule
Cortex 
Medulla
Renal pelvis
Ureter
Renal artery
Renal Vein
25
Q

Describe the structure of a nephron

A 
Bowmans capsule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct
26
Q

Describe the blood vessels associated with a nephron

A

Afferent arteriole- Wide

Efferent arteriole- Narrow

27
Q

Explain how glomerular filtrate is formed

A

Ultrafiltration in Bowmans capsule
High hydrostatic pressure in the glomerulus forces small molecules out of capillary fenestrations against osmotic gradient
Basement membrane acts a filter

28
Q

How are cells of the Bowmans capsule adapted for ultrafiltration?

A

Fenestrations between epithelial cells or capillaries

Fluid can pass between podocytes

29
Q

State what happens during selective reabsorption and where it occurs

A

Useful molecules from glomerular filtrate e.g glucose are reabsorbed into the blood
Occurs in proximal convoluted tubule

30
Q

Outline the transport processes involved in selective reabsorption

A

Glucose from glomerular filtrate > co transport with Na+ > cells lining proximal convoluted tubule > active transport > intercellular spaces > diffusion > blood capillary lining tubule

31
Q

How are cells in the proximal convoluted tubule adapted for selective reabsorption?

A

Microvilli
Many mitochondrion
Folded basal membrane

32
Q

What happens in the loop of henle?

A
  1. Active transport of Na+ and Cl- out of ascending limb
  2. Water potential of interstitial fluid decreases
  3. Osmosis of water out of descending limb
  4. Water potential of filtrate decreases going down the descending limb
33
Q

Explain the role of the distal convoluted tubule

A

Reabsorption of water via osmosis and of ions via active transport
Permeability is determined by action of hormones

34
Q

Explain the role of the collecting duct

A

Reabsorption of water from filtrate into interstitial fluid via osmosis through aquaporins

35
Q

Why is it important to maintain an Na+ concentration gradient?

A

Countercurrent multiplier - filtrate in collecting duct is always beside an area of interstitial fluid that has a lower water potential
Maintains water potential gradient for maximum reabsorption of water

36
Q

What might cause blood water potential to change?

A

Level of water intake
Level of ion intake in diet
Level of ions used in metabolic processes of excreted
Sweating

37
Q

Explain the role of the hypothalamus in osmoregulation

A
  1. Osmosis of water out of osmoreceptors in hypothalamus causes them the shrink
  2. This triggers the production of antiduretic hormone (ADH)
38
Q

Explain the role of the posterior pituitary gland

A

Stores and secretes ADH produced by the hypothalamus

39
Q

Explain the role of ADH in osmoregulation

A
  1. Makes cells lining collecting duct more permeable to water: binds to receptors > activates phosphorylase > vesicles with aquaporins on membrane fuse with cell surface membrane
  2. Makes cells lining collecting duct more permeable to urea: Water potential in interstitial fluid decreases, more water reabsorbed = more concentrated urine

Biology (20 decks)

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