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Biology IGCSE > Homeostasis > Flashcards

Homeostasis Flashcards

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1
Q

Define homeostasis

A

Maintenance of a constant internal environment

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2
Q

State 3 conditions which need to be controlled within

the body

A
  • Temperature
  • Water levels
  • Blood glucose concentration
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3
Q

What are the 3 main parts to a coordinated

response?

A
  • A stimulus (e.g. temperature change)
  • A receptor (to detect the change)
  • An effector (to carry out the response)
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4
Q

What is a stimulus?

A

A stimulus is a change in the

environment

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5
Q

What is an effector?

A

A part of the body that brings about the
response to a stimulus like a muscle or a
gland.

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6
Q

Why does the temperature need to be controlled?

A

To provide a suitable environment for
enzymes so that they can work fastest at
their optimum temperature

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7
Q

Give 2 processes involving the skin that

cool the body down

A

Sweating - Cools the body by evaporation
Vasodilation - Allows blood to flow closer
to the surface of the skin where it can cool

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8
Q

Describe the process of vasodilation

A
  • The body detects a rise in temperature
  • Blood vessels supplying the capillaries at the skin
    surface dilate (the muscles in the vessels relax)
  • More blood flows closer to the skin where it can
    cool
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9
Q

Give 3 processes that work to keep the

body warm

A
  • Vasoconstriction
  • Shivering
  • Erection of hairs on the skin
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10
Q

Describe the process of vasoconstriction

A
  • The body detects a drop in temperature
  • Blood vessels supplying the capillaries at the skin
    surface constrict (the muscles in the vessels
    contract)
  • Less blood flows closer to the skin surface so less
    heat is lost to the surroundings
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11
Q

What are hormones?

A

Hormones are chemical messengers that
are secreted by glands of the endocrine
system into the bloodstream.

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12
Q

Role of insulin?

A
  • Helps control blood sugar level

- Stimulates to liver to turn glucose into glycogen for storage

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13
Q

Where is insulin secreted from?

A

Pancreas

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14
Q

What does testosterone do?

A
  • Main male sex hormone
  • Involved in growth of testes and penis
  • Triggers many changes in males during
    puberty (hair growth, deeper voice, increased
    muscle mass)
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15
Q

Where is testosterone secreted from?

A

The testes

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16
Q

When is adrenaline secreted?

A

During times of anxiety, fear or stress

17
Q

Where is adrenaline released from?

A

The adrenal glands

18
Q

Give 3 effects of adrenaline in the body

A
  • Increases heart and breathing rate
  • Increases blood glucose concentration
  • Dilates the pupils
19
Q

What does oestrogen do?

A

Oestrogen causes the uterus lining to

thicken

20
Q

Where is oestrogen secreted from?

A

The ovaries

21
Q

What does progesterone do?

A

Progesterone maintains the uterus lining

22
Q

Where is progesterone secreted from?

A

The ovaries

23
Q

What hormone does progesterone inhibit?

A

FSH

24
Q

What hormone does oestrogen inhibit?

A

FSH

25
Q

What does follicle stimulating hormone (FSH) do?

A
  • Stimulates the egg to mature

- Stimulates ovaries to produce oestrogen

26
Q

What does luteinising hormone (LH) do?

A
  • Stimulates the release of an egg from the ovaries (ovulation)
27
Q

Where are FSH and LH secreted from?

A

The pituitary gland

28
Q

Where is ADH secreted from?

A

The posterior pituitary gland

29
Q

What is the role of ADH

A

Increases permeability of collecting duct - allows water to be reabsorbed into blood if salt concentration too high (dehydration)

30
Q

What is type 1 diabetes?

A

insulin dependent - insulin making cells in the pancreas don’t work

solution : injecting insulin/increased exercise/pancreas transplant

31
Q

what Is type 2 diabetes ?

A

liver and muscle cells are resistant to insulin. - unable to store glucose.

treatment : diet of low sugar meals/ regular exercise
the small amount of insulin can control glucose if it is limited

32
Q

Symptoms of diabetes

A

glucose is present in urine
constant thirst
lack of energy as glucose cant be taken up by cells
fat and protein used as an alternative source of energy resulting is weight loss.

33
Q

why is it important to regulate body temperature

A

it is important to maintain a body temperature of 37 degrees as this is the optimum temperature for enzymes. if this increases enzymes will denature
Low temperatures mean that enzymes and chemical reactions would take slowly. Therefore it wouldn’t happen at a fast enough rate to sustain life.

34
Q

what happens in the sweat glands when the body is too hot

A

as temperature of skin is warm - body wants to cool down hence endocrine sweat glands produce lots of sweat. the sweat on the surface of the skin then evaporates which means heat energy is lost

35
Q

describe the effects of insulin on the body

A

the pancreas monitors glucose levels and will release insulin into the blood stream when glucose levels are too high. insulin will stimulate the liver to store glucose as glycogen. hence ensuring blood glucose levels are not high.

36
Q

describe the effect of glucagon on the body

A

when the pancreas detects that blood glucose levels are too low, it releases glucagon into the blood. glucagon converts glucagon back into glucose so it can be absorbed into the blood and used by cells for respiration

37
Q

suggest why glycogen is insoluble

A

this allows glucose to be stored and hence not absorbed back into the blood. this means that the water concentration of the blood won’t be effected therefore preventing the osmotic effect.

38
Q

why do people with diabetes have glucose in their urine

A
  • people with diabetes have low levels of insulin
  • hence unable to regulate glucose
  • resulting in high levels of blood glucose
  • hence not all glucose can be re-absorped
  • so it is excreted through urine
39
Q

explain why reducing the levels of sugar in the blood reduces the risk of type 2 diabetes developing

A
  • diet contains less sugar
  • less sugar in blood
  • less insulin produced by the pancreas
  • decreasing the chance of insulin resistance

Biology IGCSE (7 decks)

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