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Biology > CH16 Homeostasis > Flashcards

CH16 Homeostasis Flashcards

1
Q

What is homeostasis

A

Internal environment is maintained within set limits around an optimum

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2
Q

Why is it important that core temperatures remain stable

A

Maintains stable rate of enzyme-controlled reactions and prevents damage to membranes

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3
Q

Why is it important that blood pH remains stable

A

Maintain stable rate of enzyme-controlled reactions

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4
Q

Why is it important that blood glucose remains stable

A

Maintain constant blood water potential to prevent lysis of cells
Maintain constant concentration of respiratory substrate

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5
Q

Define negative feedback

A

Self-regulatory mechanisms return internal environment to optimum when there is a fluctuation

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6
Q

Define positive feedback

A

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

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7
Q

Stages of negative feedback

A

Receptors detect deviation –> coordinator –> corrective mechanism by effector –> receptors detect that conditions have returned to normal

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8
Q

Suggest why separate negative feedback mechanism control fluctuations in different directions

A

Provides more control, especially in case of ‘overcorrection’ which would lead to deviation in the opposite direction from the original one

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9
Q

Suggest why coordinators analyse inputs from several receptors before sending an impulse to effectors

A

Receptors may send conflicting information

Optimum response may require multiple types of effector

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10
Q

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

A

Takes time to:
Produce hormone
Transport hormone in blood
Cause required change to target protein

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11
Q

Name factors that affect blood glucose concentration

A

Amount of carbohydrate digested
Rate of glycogenolysis
Rate of gluconeogenesis

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12
Q

Define glycogenesis

A

Liver converts glucose into glycogen

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13
Q

Define glycogenolysis

A

Liver hydrolyses glycogen into glucose which can diffuse into blood

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14
Q

Define gluconeogenesis

A

Liver converts glycerol and amino acids into glucose

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15
Q

Role of glucagon when blood glucose concentration decreases

A
  1. alpha cells in Islets of Langerhans in pancreas detect decrease and secrete glucagon in bloodstream
  2. Glucagon binds to surface receptors on liver cells and activates enzymes for glycogenolysis and gluconeogenesis
  3. Glucose diffuses from liver into bloodstream
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16
Q

Role of adrenaline when blood glucose concentration decreases

A
  1. Adrenal glands produce adrenaline. It binds to surface receptors on liver cells and activates enzymes for glycogenolysis
  2. Glucose diffuses from liver into bloodstream
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17
Q

What happens when blood glucose concentration increases

A
  1. Beta cells in Islets of Langerhans in pancreas detect increase and secrete insulin into bloodstream
  2. Insulin binds to surface receptors on target cells to:
    - increase cellular glucose uptake
    - active enzymes for glycogenesis
    - stimulate adipose tissue to synthesise fat
18
Q

How does insulin lead to a decrease in blood glucose concentration

A

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

19
Q

How does insulin increase permeability of cells to glucose

A

Increases number of glucose carrier proteins

Triggers conformational change which opens glucose carrier proteins

20
Q

How does insulin increase glucose concentration gradient

A

Activates enzymes for glycogenesis in liver and muscles

Stimulates fat synthesis in adipose tissue

21
Q

How do glucagon and adrenaline work

A

Secondary messenger model

  1. Hormone-receptor complex forms
  2. Conformational 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
22
Q

Explain causes of type 1 diabetes

A

Body cannot produce insulin

Treated by injection of insulin

23
Q

Explain causes of type 2 diabetes

A

Glycoprotein receptors are damaged or become less responsive to insulin
Treated by controlling diet and exercise regime

24
Q

Signs and symptoms of diabetes

A

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

25
Q

How could colorimetry be used to identify the glucose concentration in a sample

A
  1. Benedict’s test on solutions of known conc - use colorimeter to record absorbance
  2. Plot calibration curve
  3. Benedict’s test and absorbance of unknown sample and use calibration curve
26
Q

Define osmoregulation

A

Control of blood water potential via homeostatic mechanisms

27
Q

Describe gross structure of kidney

A

Fibrous capsule - protects kidney
Cortex - Consists of Bowman’s capsules, convoluted tubules and blood vessels
Medulla - consists of collecting ducts, loop of Henle and blood vessels
Renal pelvis - cavity collects urine into ureter
Ureter - tube carries urine to bladder
Renal artery - supplies kidney with oxygenated blood
Renal vein - returns deoxygenated blood from kidney to heart

28
Q

Describe structure of nephron

A 
Bowman's capsule 
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct
29
Q

Blood vessels associated with nephron

A

Wide afferent arteriole from renal artery enters renal capsule and forms glomerulus
Efferent arteriole branches to form capillary network that surrounds tubule

30
Q

How is glomerular filtrate produced

A

Ultrafiltration in Bowman’s capsule
High hydrostatic pressure in glomerulus forces small molecules out of capillary fenestrations against osmotic gradient
Basement membrane acts as filter

31
Q

How are cells of Bowman’s capsule adapted for ultrafiltration

A

Fenestrations between epithelial cells of capillaries

Fluid can pass between and under folded membrane of podocytes

32
Q

What happens during selective reabsorption

A

Useful molecules from glomerular filtrate are reabsorbed into the blood
Occurs proximal convoluted tubule

33
Q

How are cells in proximal convoluted tubule adapted for selective reabsorption

A

Microvilli - large SA for co-transporter proteins
Many mitochondria - ATP for AT of glucose
Folded basal membrane - large SA

34
Q

What happens in loop of Henle

A
  1. AT 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 descending limb
35
Q

Role of distal convoluted tubule

A

Reabsorption of water via osmosis and ions via AT

Permeability of walls determined by action of hormones

36
Q

Role of collecting duct

A

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

37
Q

Importance of maintaining Na+ gradient

A

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

38
Q

What might cause blood water potential to change

A

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

39
Q

Role of hypothalamus in osmoregulation

A

Osmosis of water out of osmoreceptors in hypothalamus cause them to shrink
Triggers hypothalamus to produce antidiuretic hormone (ADH)

40
Q

Role of posterior pituitary gland in osmoregulation

A

Stores and secretes ADH produced by hypothalamus

Biology (9 decks)

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