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Homeostasis Flashcards

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Biology 101 flashcards
1
Q

Positive feedback

A

Deviation from optimum causes changes that result in greater deviation from the normal

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2
Q

Components of control mechanism

A

Optimum point
Receptor - detects deviation from optimum
Coordinator - coordinates info from receptor and sends to effector
Effector - brings about changes to bring system to optimum

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3
Q

Negative feedback

A

Stimulus causes corrective measures that turns off its own measures. Brings system to original and prevents overshoot

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4
Q

Mechanism of adrenaline

A

Binds to protein receptor on liver cell membrane.
Causes protein to change shape on inside of membrane.
Leads to shape change and activation of enzyme called adenyl cyclase that converts ATP to cyclic AMP that binds to and activates kinase.
This catalyses conversion of glycogen to glucose, which moves out of the cell via channel proteins to blood.

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5
Q

Glycogenesis

A

Conversion of glucose to glycogen

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6
Q

Glycogenolysis

A

Breakdown of glycogen to glucose.

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7
Q

Gluconeogenesis

A

Production of glucose from sources other than carbohydrate i.e amino acids and glycerol

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8
Q

How insulin brings about change of blood-glucose level

A

Combines with cell surface receptor. Change in tertiary structure of glucose transport carrier proteins so that more glucose enters cell via facilitated diffusion.
Increase in number of glucose carrier proteins in cell membrane (vesicles containing this protein fuse with cell surface membrane)
Activation of enzymes that convert glucose to glycogen and fat

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9
Q

How does glucagon change blood-glucose level

A

Binds to protein receptor on liver cell membrane.
Causes protein to change shape on inside of membrane.
Leads to shape change and activation of enzyme called adenyl cyclase that converts ATP to cyclic AMP that binds to and activates kinase.
This catalyses conversion of glycogen to glucose, which moves out of the cell via channel proteins to blood.

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10
Q

Type 1 diabetes

A

Body unable to produce insulin, auto-immune attack of beta cells of islets of Langerhans

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11
Q

Type 2 diabetes

A

Glycoprotein receptors on body cells being lost/losing responsiveness or inadequate supply of insulin from pancreas

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12
Q

Type 1 diabetes control

A

Injections of insulin, blood glucose monitored by biosensors

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13
Q

Type 2 diabetes control

A

Regulating intake of carbohydrate in diet and matching to amount of exercise.
Can also be supported by injections of insulin

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14
Q

Renal (Bowman’s) Capsule

A

Close end at start of nephron, surrounds mass of blood capillaries known as glomerulus, inner later made of podocytes

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15
Q

Proximal convoluted tubule

A

Series of loops surrounded by blood capillaries, walls made of epithelial cells with microvilli
Also cotransport

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16
Q

Loop of Henle

A

Long, hairpin loop that extends from cortex into medulla and back, surrounded by blood capillaries

17
Q

Distal convoluted tubule

A

Series of loops surrounded by blood capillaries, walls made of epithelial cells

18
Q

Collecting duct

A

Tune where distal convoluted tubules empty into, lined by epithelial cells

19
Q

Afferent arteriole

A

Small vessel that arises from renal artery and supplies nephron with blood, enters renal capsule and forms glomerulus

20
Q

Glomerulus

A

Branched knot of capillaries where fluid is forced out of blood

21
Q

Efferent arteriole

A

Tiny vessel that leaves renal capsule, smaller diameter than afferent arteriole so increase of blood pressure in glomerulus, branches later on to form capillaries

22
Q

Blood capillaries

A

Concentrated network of capillaries that surrounds proximal convoluted tubule, loop of Henle and distal convoluted tubule where mineral salts, glucose and water are reabsorbed, merge to form veins which merge to form renal vein

23
Q

Contents of glomerular filtrate

A

Water, glucose, mineral ions

24
Q

What factors resist movement of glomerular filtrate out of arteriole

A

Capillary epithelial cells and connective tissue
Epithelial cells of renal capsule
Hydrostatic pressure of fluid in renal capsule space
Low water potential of blood in glomerulus

25
Q

How is glomerular filtrate formed

A

Despite resistance, podocytes on inner later of renal capsule allow filtrate to pass between their branches.
Endothelium also has spaces between cells so fluid can pass between and through basement membrane.
The hydrostatic pressure due to the decrease in diameter between afferent and efferent arteriole pushes molecules out between these gaps and through capillary basement membrane.

26
Q

What happens in ascending limb of loop of Henle

A

Sodium ions actively transported out using ATP, creating low water potential in region of medulla between 2 limbs. Thick walls mean no water escapes. Increasingly higher water potential due to loss of Na+

27
Q

What happens in descending limb of loop of Henle

A

Water passes out of filtrate by osmosis into interstitial space and is carried away be blood capillaries and Na+ diffuses in. Reaches lowest water potential at end of hairpin

28
Q

Water potential in cortex and medulla

A

High water potential (low ion conc.) in cortex that gets lower when going further into medulla

29
Q

What happens in collecting duct

A

Filtrate moves down and loses water via osmosis and is carried away by capillaries

30
Q

What happens in DST

A

Concentration of ions and glucose and pH of blood controlled by reabsorption of molecules from filtrate by active transport .

31
Q

How does body respond to fall in water potentia

A

Cells in hypothalamus lose water due to fall in water potential in blood.
Hypothalamus produces ADH and it secreted in capillaries via pituitary gland.
Passes to blood in kidneys, increases permeability of water of cell surface membrane in cells of DST and CD.
Receptors bind to ADH and activates phosphorylase that causes vesicles with aquaporins to bind to cell surface membrane.
Permeability of collecting duct to urea also increased, lowering water potential of fluid around duct.

32
Q

How does body respond to rise in water potential

A

Osmoreceptors detect rise and increase frequency of impulses to pituitary gland to reduce release of ADH.
Decrease in permeability of cells of DST and CD to water and urea, less reabsorption, more dilute urine.
When water potential returns to normal, osmoreceptors make pituitary gland raise release of ADH again.

33
Q

Why does longer loop of Henle result in high urine conc

A

Increase in sodium ion concentration in medulla.

More water absorbed from collecting duct and loop by osmosis.

Bio (20 decks)

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