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A-level biology > homeostasis > Flashcards

homeostasis Flashcards

1
Q

what is homeostasis?

A

maintaining a stable internal environment by regulating different processes

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2
Q

what is negative feedback?

A
  • a series of changes that result in a system being restored to its original state
  • when the stimulus causes the corrective measures to be turned off, returning the system to its original level
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3
Q

what is positive feedback?

A
  • occurs when the feedback causes the corrective measures to remain on
  • in doing so it causes the system to deviate even further from the norm
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4
Q

methods of gaining heat:

A
  • production of heat - metabolism of food

* gain heat from environment - conduction, convection, radiation

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5
Q

methods of lowering heat:

A
  • evaporation of water - during sweating

* loss of heat to environment - conduction, convection & radiation

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6
Q

go through the process of negative feedback

A

stimulus -> receptors -> control center -> effectors -> response

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7
Q

type of message sent

A

chemical

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8
Q

speed of transmission

A

slow

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9
Q

method of transmission

A

in the blood

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10
Q

how long does a response last

A

long term

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11
Q

what is glycogenolysis

A

breakdown of glycogen by glucagon

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12
Q

what is glycogensis

A

creation of glycogen by insulin

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13
Q

what is gluconeogenesis

A

creation of new glucose from non-carbohydrate substrates e.g amino acids & lipids

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14
Q

what do hormones do

A

carry information from one part of a mammals body to another part

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15
Q

what produces hormones

A

endocrine glands

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16
Q

how do endocrine glands produce hormones?

A

contain secretory cells which secrete hormones directly into the blood e.g pituitary, adrenal, pancreas

17
Q

what are exocrine glands?

A
  • exocrine = secreting to the outside

* they secrete substances which are not hormones into a tube or duct along which the secretions show

18
Q

what is the pancreas

A

an organ that has both endocrine and exocrine functions

19
Q

how do hormones work?

A
  • small molecules
  • can be polypeptides (insulin) or steroids (oestrogen)
  • concentrations in the blood are always very small
  • broken down by enzymes or lost in urine
  • effects particular cells called target cells which contain receptors that are complementary to the hormone
20
Q

what is the pancreas’ endocrine function

A

secretes insulin and glucagon

21
Q

what does the pancreas do

A

• control blood glucose levels, produced by group of cells called islets of langerhans
• 2 types of cell:
- alpha cells are larger and secrete glucagon
- beta cells are smaller and secrete insulin

22
Q

what do alpha cells do

A

secrete glucagon

23
Q

what do beta cells do

A

secrete insulin

24
Q

the effect of insulin in body cells

A
  • insulin binds to glycoprotein receptors complementary to the hormone insulin found on the plasma membrane of most cells
  • this causes the tertiary structure of the glucose transport protein channel to change shape and open, allowing more glucose into the cell by facilitated diffusion
25
Q

the effect of insulin on the muscles

A
  • insulin causes additional carrier proteins to join the membrane
  • insulin bids to receptors, this releases a chemical signal which causes vesicles inside the cell to move and fuse with the plasma membrane
  • this adds more carrier proteins to the plasma membrane for glucose to be transported through
26
Q

the effect of insulin on liver cells

A
  • after glucose has entered by facilitated diffusion, insulin activates an enzyme that rapidly converts glucose to glucose phosphate
  • this maintains a steep concentration gradient between the blood and the liver cells
  • ensures glucose still enters the cells and equilibrium isn’t reached
  • glycogenesis eventually becomes glycogen
27
Q

what do alpha cells do

A

detect a fall in the blood glucose concentration and respond by secreting glucagon into the blood plasma

28
Q

what does glucagon do (full process)

A
  • glucagon binds w receptor on liver cell membrane
  • causes protein on the inside of the plasma membrane to change shape
  • this activates enzyme adenyl cyclase
  • this breaks two phosphate groups away from ATP to form CAMP
  • CAMP binds w enzyme protein kinase which changes the shape of the enzyme and activates it
  • protein kinase then catalyses the reaction to break glycogen into glucose
  • glucose leaves the cell via facilitated diffusion
29
Q

how does gluconeogenesis work

A
  • breakdown of non carbohydrate substrates
  • glucagon will bind to receptors on target cells and will activate enzymes
  • the enzymes will convert glycerol, amino acids and fatty acids into glucose
  • glucose will leave the target cells by facilitated diffusion and will raise the blood glucose level
30
Q

what causes type 1 diabetes

A
  • when the immune system attacks and destroys the insulin-producing beta cells of the pancreas
  • insulin isn’t produced so glycogenesis cant happen to promote the uptake of glucose
  • blood glucose levels stay high
31
Q

how is type 1 diabetes treated

A

insulin injections into the body

32
Q

what causes type 2 diabetes

A
  • when the body becomes resistant to insulin/pancreas is unable to produce enough insulin
  • can be caused by poor diet/obesity
  • body breaks down carbs into glucose but glucose levels keep rising as insulin doesn’t work properly
  • therefore more insulin is released = tires out pancreas & makes less insulin
33
Q

how is type 2 diabetes treated

A
  • lifestyle changes = losing weight
  • blood glucose monitoring & medication
  • insulin injections

A-level biology (25 decks)

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