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biology > Homeostasis > Flashcards

Homeostasis Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Define homeostasis

A

Maintenance of constant internal environment within restricted limits

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2
Q

Describe the importance of homeostasis

A

Maintaining pH of blood = prevent denaturing of enzymes

Constant water potential= reliable source of Respiratory substrate prevent Osmotic damage

Allow organisms to live in larger range of environments

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3
Q

What features do all control mechanisms posses

A

Optimum point

Receptor

CO ordinator

Effector

Feedback mechanism

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4
Q

Define feedback mechanism

A

Receptor responds to stimulus brought about by Effector

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5
Q

Define negetive feedback

A

Restores system to original level

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6
Q

Define positive feedback

A

Deviation from optimum causes further deviation from optimum

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7
Q

Where are hormones produced

A

Endocrine Glands

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8
Q

How do hormones reach target cells

A

Blood plasma

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9
Q

By what action do hormones act

A

Second messenger model

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10
Q

What hormones act vía second messenger model

A

Glucagon

Adrenaline

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11
Q

Describe the second messenger model

A

Hormones bind to como receptor on liver cell

Activates adenylate cyclase

Converts ATP to cAMP

cAMP activates protein kinase

Catalyses glycogenolysis

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12
Q

Describe the role of the pancreas

A

Exocrine - secrete digestive enzymes into ileum

Endocrine– secrete hormones into blood

Detect change in blood glucose conc and secrete hormones

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13
Q

What cells secrete insulin and glucagon and where are they found

A

Islet of langerhans

Alpha= glucagon

Beta = insulin

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14
Q

What is the role of the liver

A

Where hormones have effect

Glycogenolysis gluconeognesis and glycogenolysis gave effect

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15
Q

What are liver cells called

A

Hepatocytes

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16
Q

Define glycogenolysis

A

Hydrolysis of glycogen to glucose

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17
Q

Define gluconeognesis

A

Glucose production from non carbohydrate sources

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18
Q

Define gluconeognesis

A

Glucose production from non carbohydrate sources

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19
Q

Define glycogeneiss

A

Production of glycogen from glucose

20
Q

Sources of blood glucose

A

Diet

Glycogenolysis

Gluconeognesis

21
Q

Describe the action of insulin

A

Change structure of gcp to allow more glucose in

Cause vesicles with gcp to fuse with cell membrane increasing number of gcp and permeability to glucose

Activate enzymes involved in glycogenesis

22
Q

Describe the action of glucagon

A

Activate enzymes involved in glycogenolysis and gluconeognesis via second messenger model

23
Q

Describe action of Adrenaline

A

Acts via second messenger model

Activating enzymes involved in glycogenolysis and gluconeognesis

24
Q

What is diabetes

A

Metabolic diabetes causing inability to control BGC

25
Q

Describe type 1 diabetes

A

Produce little to no insulin. Insulin dependent

Rapid and early development

Can be due to autoimmunity

Treated with insulin injections

26
Q

Describe type 2 diabetes

A

Insulin independent

Loss of insulin receptors/ sensitivity

May also be due to inadequate insulin supply

Poor diet and excersie

Treat with diet and exercise

27
Q

What steps are involved in osmoregulation?

A

Ultrafiltration
Reabsorption of glucose and water on PCT

Maintenance of water potential gradient
Reabsorption of water and sodium ions

28
Q

Describe ultrafiltration

A

Small molecules such as glucose and Amino acids are forced out of the blood into glomerular filtrate.

Due to higher HPa of blood

29
Q

What resists ultrafiltration

A

HPa of glomerular filtrate

Osmotic Pa of filtrate

Basmenet membrane cells (endo podocyte)

30
Q

Why are small molecules forces out of glomerular capillaries

A

Diameter of effernet artiriole is smaller than afferent causing increase in blood pressure.

31
Q

Where does ultrafiltration occur

A

Renal bowman’s capsule

32
Q

How is the capsule adapted for ultrafiltration

A

Podocyte have foot like processes allowing molecules to pass between

Endothelium of glomerular capillaries are fenestrated so have gaps

33
Q

What adaptions does the proximal convoluted tubule have?

A

Epithelial cells have microvilli and I folding to increase surface area

Many mitochondria for na/k pump

Good blood supply to maintain conc gradient

34
Q

Name the parts for the system a small molecule passes when producing urine

A

Glomerular

Renal bowman’s capsule

Proximal convoluted tubule

Loop of henle

Distal convoluted tubule

Collecting duct

35
Q

Describe how substances are reabsorbed in the PCT

A

3 Na+ are pumped out and 2k+ are pumped in

Na+ conc gradient set up

Glucose Amino acids mineral ion and vitamins enter via FD until equilibrium and then Co Transported with Na+

Glucose e.t.c then FD into tissue fluid and then cappilaries

Solutes into epithelial cells and blood decrease water potential so water reabsorbed vía Osmosis

Lipid soluble substances reabsorbed via simple diffusion

Ions move via SD through tight junction

36
Q

Where is the loop of henle found

A

In nephron in medulla

37
Q

Describe the descending limb

A

Permeable to water impermeable to ions

Narrow with thin walls

38
Q

Describe the ascending limb

A

Wide with thick walls

Impermeable to water

Permeable to ions

39
Q

How is the gradient in the loop of henle maintained

A

Counter current multiplier

40
Q

How and why does the length of the loop of henle affect the amount of water absorbed

A

Longer loop = more water absorbed so more conc urine

41
Q

What is the function of the DCT

A

Make final adjustments to water potential and ion conc

42
Q

What occurs in the DCT and how is it adapted for this

A

Water and ions are reabsorbed into blood

Many microvilli and mitochondria

Permeability affects by hormones

43
Q

Where is the collecting duct found

A

Medulla

44
Q

What occurs in the collecting duct

A

Water leaves via Osmosis

Nephron is connected to Ureter

45
Q

What is the WP of the blood affected by

A

Sweating

Water consumed

Intake of ions

46
Q

Describe the response to a decrease in blood wp

A

Osmoreceptors in the hypothalamus decent change in wp

Impulses sent to hypothalamus to produce more ADH

Impulses to posterior pituitary gland so more ADH released into blood

Increased absorption of water in DCT and collecting duct

Prevent further lower of wp

(impulses also sent to theist centre)

47
Q

Describe response to increase in wp

A

Detected by osmoreceptors in hypothalamus

Less impulses to hypothalamus so less ADH
Produced

Less ADH released from posterior pituitary gland

Less water reabsorbed in DCT and collecting duct

Larger volume of Dilute urine decreases wp

biology (28 decks)

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