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biology year 2 > Homeostasis > Flashcards

Homeostasis Flashcards

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1
Q

example of positive feedback

blood clot after injury

A
  • platelets activated - release chemical
  • triggers more platelets = activated
  • platelets quickly form blood clot at injury site
  • process ends with neg feedback - body detects blood clot formed
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2
Q

hypothermia

A
  • low body temp
  • when heat lost from body quicker than produced
  • body temp falls - brain doesnt work
  • shivering stops - body temp FALLS MORE
  • pos feedback takes body temp AWAY from normal level
  • continues to decrease until action taken
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3
Q

why isnt pos feedback involved in homeostasis?

A

doesnt keep internal enviro stable

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4
Q

what is the conc of glucose in blood normally?

A

90 mg per 100cm3

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5
Q

Beta cells secrete…

A

insulin into blood

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6
Q

alpha cells secrete…

A

glucagon into blood

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7
Q

define glycogenesis?

A

process of forming glycogen from glucose

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8
Q

define glycogenolysis?

A

process of breaking down glycogen

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9
Q

define gluconeogenesis?

A

process of forming glucose from non-carbs

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10
Q

insulin …

A

lowers blood glucose conc when too high

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11
Q

glucagon…

A

raises blood glucose conc when too low

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12
Q

what is GLUT4?

A

channel protein in skeletal and cardiac muscle

  • is glucose transporter
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13
Q

what is hyperglycaemia?

what can it lead to?

A
  • after eating, blood glucose level rises and stays high
  • death if untreated
  • kidneys cant reabsorb all glucose
  • some excreted as urine
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14
Q

how do you carry out the quantitative benedicts test?

A
  • add quantitative benedicts reagent to sample
  • heat in boiling water bath
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15
Q

homeostatic mechanisms maintain a constant environment in the body.

the graph shows changes in plasma glucose concentration that occurred in a person who went without food for some time.

explain the role of negative feedback in the control of plasma glucose concentration?

A
  • deviation of value form norm initiates negative feedback
  • fluctuations in plasma glucose conc detected by hypothalamus
  • initial decrease - no food given - stimulates secretion of glucagon
  • increase stimulates secretion of insulin from beta cells as secretors
  • dec uptake of glucose by cells
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16
Q

the graph shows on some occasions, the conc of glucose in the girls blood was very high.

suggest why?

A
  • eaten
  • meal with carbs/sugars
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17
Q

use the graph to evaluate the use of the urine test as a measure of blood glucose concentration?

A
  • postitive correlation
  • range of results for particular value
  • urine test only arbitrary scale
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18
Q

diabetic people who do not control their blood glucose conc may become unconscious and go into coma.

a doctor may inject a diabetic person who is in a coma with glucagon.

explain how glucagon would affect the persons blood glucose concentration?

A
  • glycogenolysis
  • gluceoneogenesis
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19
Q

give one example, explain why homeostasis is important in mammals?

A
  • temp
  • maintaining enzyme action
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20
Q

cross-channel swimmers may suffer from muscle fatigue during which contraction mechanisms is disrupted.

once factor thought to contribute to muscle fatigue is decrease in availability of Ca2+ within muscle fibres.

explain how a decrease in the availability of Ca2+ could disrupt the contraction of mechanism in muscles?

A
  • Ca2+ ions needed to remove tropomyosin
  • calcium ions allow formation of actin-myosin crossbridge
  • activates ATPase
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21
Q

scientists investigated the control of blood glucose conc in mice.

they kept a group of normal mice without food for 48 hours.

after 48 hours, the blood glucose conc of mice were same as at the start of experiment.

explain how the normal mice prevented their blood glucose conc falling when they had not eaten for 48 hours?

A
  • release glucagon
  • activates enzymes that catalyse glycogenolysis
  • this activates enzymes that catalyse gluconeogenesis
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22
Q

describe how urea is removed from the blood?

A
  • hydrostatic pressure generated
  • causes ultrafiltration at bowmans capsule
  • through basement membrane
  • enabled by small size urea molecule
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23
Q

explain how urea is conc in filtrate?

A
  • reabsorption of water by OSMOSIS
  • at PCT
  • at DCT
  • active transport of ions
24
Q

describe how ultrafiltration produces glomerular filtrate?

A
  • hydrostatic pressure
  • small molecules
  • pass through basement membrane
  • proteins too large to go through
  • due to presence of podocytes
25
Q

give components of the blood which are not normally present in filtrate?

A
  • blood cells
  • platelets
  • proteins
26
Q

reabsorption of glucose takes place in PCT.

explain how cells of PCT are adapted for this function?

A
  • many mitochondria prov ATP for AT
  • many carrier proteins for AT
  • microvilli prov larger surface area for absorption
27
Q

when a person is dehydrated, the cell volume of an osmoreceptor decreases.

why?

A
  • WP of blood decreases
  • water moves from osmoreceptor into blood by OSMOSIS
28
Q

stimulation of osmoreceptors can lead to secretion of hormone ADH.

describe and explain how the secretion of ADH affects urine produced by kidneys?

A
  • permeability of membrane to water inc
  • more water absorbed from DCT
  • smaller vol of urine
  • urine = more conc
29
Q

some people who have diabetes do not secrete insulin.

explain how a lack of insulin affects reabsorption of glucose in kidneys of a person who does not secrete insulin?

A
  • high conc of glucose in blood
  • high conc in filtrate
  • reabsorbed by FD
  • requires proteins
  • these are workin at max rate
  • not all glucose reasborbed
30
Q

some desert mammals have long loops of Henle and secrete large amounts of ADH.

explain how these 2 features are adaptations to living in desert conditions?

A
  • more water reabsorbed
  • by OSMOSIS
  • from collecting duct
  • due to longer loop of Henle
  • Na+/Cl- absorbed from filtrate in ascending limb
  • gradient established in medulla
  • acts on collecting duct
  • makes cells more permeable
31
Q

the kangaroo rat is a small desert mammal. it takes in very little water in its food and it rarely drinks.

its core body temp is 38 degrees.

the kangaroo rat takes in some water by feeding and drinking.

describe another method by which the kangaroo rat could obtain water?

A

from aerobic respiration

32
Q
A
  • treated / controlled by diet / exercise
  • usually type 2 produce insulin cells / receptors less responsive to insulin
33
Q

define homeostasis?

A

physiological control systems that maintain a constant internal enviro

34
Q

how temp affects homeostasis?

A
  • metabolism controlled by enzymes
  • enzymes have optimum temp
  • too HOT - enzymes denature
  • too COLD - rate of reaction slows
35
Q

how pH affects homeostasis?

A
  • too acidic

OR

  • too alkaline

RATE OF REACTION DEC

36
Q

how glucose affects homeostasis?

A
  • minimum amount of gluc needed as resp substrate
  • too much - dec WP of blood
  • water will move out of cells by OSMOSIS
  • cells shrivel up
37
Q

negative feedback

A

when receptors detect a change away from normal and effectors activate mechanisms to return body back to normal

38
Q

examples of negative feedback?

A
  • body temp
  • pH
  • glucose
39
Q

in negative feedback what gives more control?

A

separate systems

(more than one)

40
Q

positive feedback

A

a response that results in effectors further amplifying from normal

41
Q

examples of positive feedback?

A
  • Na+ channel threshold - depolarisation
  • blood clotting
42
Q

which hormones are involved in second messenger model?

A
  • adrenaline
  • glucacagon
43
Q

second messenger model

A
  • adrenaline / glucagon comp to receptor protein on cell memb of target cell e.g. liver cell
  • adenyl cyclate activated
  • converts ATP to cAMP (cyclic AMP)
  • cAMP activates enzyme protein kinase A by changing TS
  • cAMP is second messenger
44
Q

blood glucose conc too high

A
  • receptors in pancreas detect inc in blood glucose
  • beta cells secrete insulin
  • insulin binds to receptors in liver and muscle cells
  • inc perm to glucose
  • more glucose absorbed by FD
  • glycogenesis
  • inc rate of respiration
45
Q

blood glucose conc to low

A
  • receptors in pancreas detect low blood glucose
  • alpha cells secrete glucagon
  • glucagon binds to receptors on liver cells
  • gluconeogenesis
  • glycogenolysis
  • dec rate of respiration
46
Q

define diabetes mellitus?

A

illness where blood glucose levels not controlled

47
Q

causes of type 1 diabetes

A
  • immune system kills beta cells in islets of Langerhan
  • cant make insulin

(in children and young adults)

48
Q

type 1

effect on blood glucose

A
  • hyperglycaemia
  • stays high - kidneys cant remove glucose from urine
49
Q

treatment of type 1 diabetes

A
  • insulin injections / pump (too much = hypoglycaemia)
  • avoid simple carbs
  • eat at reg intervals
  • regular exercise
50
Q

causes of type 2 diabetes

A
  • obesity
  • lack of exercise
  • poor diet
  • beta cells dont make enough insulin
  • liver and muscle cells stop responding to insulin

(adults/elderly)

51
Q

type 2 effect

A

hyperglycaemia

52
Q

type 2 treatment

A
  • eat healthily
  • lose weight
  • regular exercise
  • drugs - reduce amount glucose released - inc senitivity to insulin - make more insulin
  • insulin injections
53
Q

glucagon mechanisms

A
  • dec resp rate
  • glycogenolysis
  • gluconeogenesis
54
Q

adrenaline mechanisms

A

ACTIVATES

  • glycogenolysis
  • secretion of glucagon

INHIBITS

  • glycogenesis
  • insulin
55
Q

insulin mechanisms

A
  • inc resp rate
  • glycogenesis
  • inc liver and muscles perm to glucose

biology year 2 (29 decks)

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