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Biology Unit 5 > Homeostasis > Flashcards

Homeostasis Flashcards

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0
Q

Endotherm

A

Animal that maintains a constant body temperature (mammal that does homeostasis)

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1
Q

Ectotherm (definition)

A

Animal which regulates it’s temperature by exchanging heat with its surroundings (doesn’t do homeostasis) e.g. Reptiles

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2
Q

Temperature control:

When an endotherm becomes too cold, what happens?

A
  • Thermoreceptors detect the fall in temperature
  • sends an impulse to hypothalamus in the brain
  • effector: arterioles muscles
  • response: vasoconstriction of arterioles near skin surface so blood is kept away from surface preventing heat loss
  • effector: hair erector muscles
  • response: hairs stand up and trap warm air close to skin
  • effector: skeletal muscles contract (shivering)
  • response: generates heat by respiration
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3
Q

Temperature control:

When an endotherm becomes too hot, what happens?

A
  • thermoreceptors detect rise in temperature
  • sends an impulse to hypothalamus in brain
  • effector: arterioles muscles
  • response: vasodilation of arterioles near skin so blood flows close to surface allowing heat loss by radiation through the skin
  • effector: sweat glands
  • response: secretion of sweat so skin loses heat (from blood) by evaporation
  • effector: salivary glands
  • response: panting allows heat (from blood) to be lost by evaporation
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4
Q

Heart rate control:

Why and how does the heart rate increase?

A
  • blood CO2 is high (due to respiration)
  • detected by chemoreceptors in the aorta
  • impulse sent to medulla oblongata
  • impulse sent back to heart muscle
  • SAN causes heart rate to speed up (via sympathetic nerves)

SOMETIMES: (in extreme situations)
-adrenal gland is stimulated to secrete adrenaline to speed up heart rate

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5
Q

Heart rate control:

Why and how does the heart rate slow down?

A
  • blood CO2 is low
  • detected by chemoreceptors in aorta
  • impulse sent to medulla oblongata
  • impulse sent back to heart muscle
  • SAN causes heart rate to slow down (via parasympathetic nerves)
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6
Q

Which nervous system speeds things up?

A

Sympathetic nervous system

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7
Q

Which nervous system slows things down?

A

Parasympathetic nervous system

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8
Q

What does the sympathetic nervous system do?

A

Speed things up

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9
Q

What does the parasympathetic nervous system do?

A

Slows things down

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10
Q

What do endocrine glands do?

A

Secrete hormones into the blood

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11
Q

What kind of glands secrete hormones?

A

Endocrine glands

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12
Q

Hormone definition

A

A protein that is secreted into the blood, binds to target cells with the complementary receptor.
Can have a widespread (long term) effect and spread by diffusion

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13
Q

What do exocrine glands do?

A

Secrete a product via a duct onto the surface next to the gland (e.g. Saliva, sweat)
Stimulated by hormone secretion
E.g. Pancreatic secretions in small intestine

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14
Q

Is the pancreas an endocrine gland or an exocrine gland?

A

Both

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15
Q

Why is the pancreas an endocrine gland?

A

It secrete hormones

Insulin and glucagon to control blood glucose

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16
Q

Why is the pancreas an exocrine gland?

A
  • enzymes are secreted (e.g. Amylase, trypsin)
  • secretions are controlled by nerves and hormones
  • pancreatic secretions go into small intestine
  • pancreatic secretions make small intestine alkaline
17
Q

Which two hormones regulate blood glucose?

A

Insulin and glucagon

18
Q

Where are the alpha and beta cells?

A

In the islets of Langerhans in the endocrine tissue of the pancreas

19
Q

When and where from is insulin secreted?

A
  • secreted from Beta cells

- when blood glucose is too high

20
Q

What happens when blood glucose is too high?

A
  • high blood glucose is detected by beta cells
  • insulin is secreted into the blood from beta cells in islets of Langerhans in pancreas
  • insulin binds to receptors on liver cells
  • activating carrier proteins, increasing membrane permeability to glucose
  • allows glucose to be taken into cells
  • activates enzymes involved in glycogenesis which converts glucose into glycogen
21
Q

What happens when blood glucose is too low?

A
  • low blood glucose is detected by alpha cells
  • glucagon is secreted into the blood from alpha cells in the islets of Langerhans in the pancreas
  • glucagon binds to receptors on liver cells
  • activates enzymes used in glycogenolysis (converting glycogen to glucose)
  • glucose diffuses into blood
22
Q

What is Gluconeogenesis?

A

Making glucose from glycerol and fats when glucose is very low (in extreme situations)

23
Q

How does adrenaline increase blood glucose concentration?

A

-adrenaline binds to a receptor on the cell membrane
(Adrenaline is too big to pass through cell membrane by diffusion)
(Adrenaline must use channel protein to pass into cell)

-inside cell, ATP is converted to cAMP
-cAMP activates the protein channel
-protein channel changes shape so adrenaline can pass through
-enzymes in the cell are activated
-glycogenolysis and Gluconeogenesis occur to make glucose
(Glycogenesis is inhibited)

24
Q

what is cAMP

A
  • a secondary messenger

- ATP with 2 phosphate groups removed

25
Q

When does type 1 diabetes occur?

A

When there is a lack of insulin because the immune system destroys most/all beta cells in pancreas
Tends to be present from birth (genetic)

26
Q

How is type 1 diabetes managed?

A

Regular injections of insulin

27
Q

When does Type 2 Diabetes occur

A

When the body does not produce enough insulin/ insulin produced doesn’t affect target cells
Usually doesn’t develop until 40s+

28
Q

How can type 2 diabetes be managed?

A

Can be controlled by diet (e.g more complex carbohydrates and less simple carbohydrates) and exercise
But sometimes insulin injections are required

29
Q

How can type 2 diabetes be caused?

A
  • increasing age
  • genetics
  • obesity
  • high sugar intake
  • lack of exercise
  • high blood pressure
  • excessive alcohol intake
  • more common in some ethnic groups
  • more common in males
30
Q

How can insulin be made for diabetics?

A
  • pig insulin (taken from pigs)

- bacteria produced human insulin

31
Q

Why might people disagree with the use of pig insulin?

A
  • religious, ethical reasons
  • health scares (e.g. Swine flu)
  • some people react to it as it is pig insulin
32
Q

Why might bacteria produced insulin be better than the use of pig insulin?

A
  • pigs are expensive to look after
  • pig insulin may be ineffective in some people
  • bacteria produced insulin is cheaper to produce
  • less space is required for producing insulin with bacteria
  • bacteria produce human insulin, so there will be no reactions against it and a better tolerance
33
Q

What is the Oestrous cycle?

A

Changes in hormone concentrations in mammalian fertility

34
Q

How is the oestrous cycle controlled?

A

Controlled by negative and positive feedback loops

35
Q

What does oestrogen do?

A
  • prepares the follicle in the ovary for the release of an egg
  • thickens uterus lining
  • causes positive feedback as FSH and LH are produced
36
Q

What does FSH do?

A
  • stimulated development of follicles in the ovary to ripen eggs
  • causes positive feedback and LH is then produced
37
Q

What does LH do?

A
  • further triggers ovulation a (release of an egg)

- causes positive feedback as progesterone is then produced

38
Q

Where is progesterone secreted from?

A

The corpus luteum (after realise of an egg)

39
Q

What does progesterone do?

A
  • maintains the uterus lining (thickening) ready for implantation of an egg
  • causes negative feedback as it stops production of all other hormones
40
Q

If egg is fertilised, what happens to level of progesterone?

A

Stays HIGH

41
Q

If egg is not fertilised, what happens to hormone levels?

A

Progesterone level decreases, allowing cycle to begin again

Biology Unit 5 (4 decks)

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