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Biology Paper 2 > Topic 7 – Animal Coordination, Control and HomeostasisTopic 7 – Animal Coordination, Control and Homeostasis-Homeostastis > Flashcards

Topic 7 – Animal Coordination, Control and HomeostasisTopic 7 – Animal Coordination, Control and Homeostasis-Homeostastis Flashcards

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1
Q

What is homeostasis?

A

The maintenance of a stable internal environment in the body despite fluctuations in internal and external conditions.

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2
Q

Why is homeostasis important?

A

To ensure optimum conditions for enzymes and cellular processes in the body

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3
Q

State three conditions within the body that must be controlled by homeostasis

A

● Temperature
● Blood glucose concentration
● Water levels

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4
Q

What is thermoregulation? (biology only)

A

The maintenance of core body temperature

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5
Q

Why must body temperature be controlled? (biology only)

A

Enzymes work best at their optimum temperature. Deviations from this optimum temperature decrease the rate of enzyme-controlled reactions.

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6
Q

What is the optimum temperature for enzymes in the human body? (biology only)

A

37°C

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7
Q

What does the maintenance of an ideal body temperature depend on? (biology only)

A

A negative feedback system involving:
● Receptors
● Hypothalamus
● Effectors e.g. sweat glands, hair erector muscles

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8
Q

Where are temperature-sensitive receptors located? (biology only)

A

● Skin - epidermis (outer layer) and dermis (below epidermis)
● Hypothalamus

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9
Q

What is the function of receptors in the skin and in the hypothalamus? (biology only)

A

They detect changes in blood

temperature and send information to the hypothalamus.

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10
Q

What is the function of the hypothalamus? (biology only)

A

It coordinates information from the receptors and sends instructions to the effectors.

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11
Q

What is the function of the effectors? (biology only)

A

They produce a response to counteract the change in blood temperature and return it to the set point.

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12
Q

Outline the responses of the body to an increase in temperature above 37°C (3) (biology only)

A

● Vasodilation
● Sweating
● Erector muscles relax, hairs lie flat

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13
Q

What structure produces sweat? (biology only)

A

Sweat glands found in the dermis

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14
Q

How is sweat released from the skin? (biology only)

A

Pores in the epidermis release sweat onto the skin’s surface which then evaporates.

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15
Q

How does sweating help to reduce body temperature? (biology only)

A

Heat energy is used to evaporate sweat. Increased heat transfer from the skin to the environment decreases body temperature.

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16
Q

What is vasodilation? (biology only/higher)

A

● Dilation of blood vessels near the skin surface
● Blood flows closer to the skin surface
● Greater heat loss to the surroundings

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17
Q

Outline the responses of the body to a decrease in temperature below 37°C (4) (biology only)

A

● Vasoconstriction
● Shivering
● Hair erector muscles contract
● Little sweat is produced

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18
Q

How does shivering help to increase body temperature? (biology only)

A

Involuntary contraction of muscles generates heat energy from respiration

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19
Q

How does the contraction of hair erector muscles help to increase body temperature? (biology only)

A

Hairs stand on end creating pockets of air between hairs and a layer of insulation.

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20
Q

What is vasoconstriction? (biology only/higher)

A

● Constriction of blood vessels near skin surface
● Less blood flows close to the skin surface
● Less heat loss to the surroundings

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21
Q

Which organ is responsible for the maintenance of blood glucose concentrations?

A

Pancreas

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22
Q

How are blood glucose concentrations controlled?

A

Controlled by the hormones insulin and glucagon which are secreted by the pancreas

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23
Q

Insulin and glucagon are antagonistic hormones. What does this mean?

A

They have opposite effects which counteract one another.

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24
Q

Describe the role of insulin in the regulation of blood sugar levels

A

● Causes liver and muscle cells to increase their uptake of glucose from the blood
● Glucose is converted into glycogen, a storage molecule

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25
Q

Describe the role of glucagon in the regulation of blood sugar levels (higher)

A

● Causes the breakdown of glycogen to glucose in the liver

● Glucose is released into the blood

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26
Q

What is the control of blood glucose concentration an example of?

A

Negative feedback

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27
Q

Describe what happens when blood glucose concentrations become too high (higher)

A

● Blood glucose concentration increases above a set point
● Pancreas secretes insulin and stops producing glucagon
● Liver and muscle cells increase uptake of glucose
● Glucose is converted to glycogen and stored
● Some glucose may be stored as lipid in tissues
● Blood glucose concentration decreases, returning to normal level

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28
Q

Describe what happens when blood glucose concentrations become too low (higher)

A

● Blood glucose concentration decreases below a set point
● Pancreas secretes glucagon and stops producing insulin
● Liver cells convert glycogen into glucose which is released into blood
● Blood glucose concentration increases, returning to normal level

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29
Q

What is diabetes?

A

A condition where the homeostatic control of blood glucose levels stops

30
Q

What is the cause of type 1 diabetes?

A

Pancreas does not produce enough insulin

31
Q

How is type 1 diabetes treated? (3)

A

● Daily insulin injections at meal times
● Limiting intake of refined sugars
● Regular exercise

32
Q

What is the cause of type 2 diabetes?

A

Person develops insulin resistance or doesn’t produce enough insulin (often due to obesity)

33
Q

How is type 2 diabetes treated? (3)

A

● Balanced diet
(eating fewer simple sugars and replacing them with more complex carbohydrates)
● Exercise
● Medication or insulin injections (however, these are less effective)

34
Q

How does exercise help to control diabetes?

A

Exercise increases respiration in muscle cells. Excess glucose is removed from the blood to produce energy in the form of ATP.

35
Q

Why are type 2 diabetics advised to replace simple carbohydrates with more complex carbohydrates?

A

● Simple carbohydrates are broken down quickly so can raise blood glucose levels rapidly.
● Complex carbohydrates take longer to break down so have a reduced effect on blood glucose levels.

36
Q

What is the Body Mass Index (BMI)?

A

A value based on height and mass used to categorise an individual as underweight, normal weight, overweight or obese.

37
Q

How is BMI calculated?

A

BMI=Mass(kg)/Height(m)(squared)

38
Q

What BMI values indicate obesity and an increased risk of type 2 diabetes?

A

BMI value larger than 30

39
Q

How is an individual’s waist-to-hip ratio calculated

A

waist-to-hip ratio =waist circumference cm/hip circumference cm

40
Q

What does a waist-to-hip ratio higher than 1.0 in males or 0.85 in females indicate?

A

● Abdominal obesity

● Increased risk of developing type 2 diabetes

41
Q

What is osmoregulation?

A

The maintenance of constant water

levels in the body fluids of an organism

42
Q

Why is osmoregulation important? (biology only)

A

Prevents cells bursting or shrinking when

water enters or leaves by osmosis

43
Q

Describe what happens to an animal cell if it is
placed into a solution with a higher water
concentration (biology only)

A

● Higher concentration of water in surrounding solution
● Water molecules move down their water concentration
gradient into the cell by osmosis
● Pressure inside the cell increases, cell bursts (lysis)

44
Q

Describe what happens to an animal cell if it is
placed into a solution with a lower water
concentration (biology only)

A

● Lower concentration of water in surrounding solution
● Water molecules move down their water concentration
gradient out of the cell by osmosis
● Pressure inside the cell decreases, cell shrinks (crenation)

45
Q

Describe what happens to an animal cell if it is
placed into a solution with an equal water
concentration (biology only)

A

No net movement of water molecules

into or out of the cell

46
Q

Describe the function of the kidneys (biology only)

A

● Removes toxic waste substances from the body

● Alters blood water levels

● Alters blood ion levels

47
Q

What is urine? (biology only)

A

Waste product of the kidney that
contains urea, excess water and excess
ions

48
Q

How is urea produced? (biology only)

A

In the liver, urea is produced from the

breakdown of excess amino acids.

49
Q

What is the function of the renal artery?

biology only

A

Supplies blood to the kidneys

50
Q

What is the function of the renal vein? (biology only)

A

Drains blood from the kidneys

51
Q

What is the function of the ureter? (biology only)

A

Takes urine to the bladder from the

kidneys

52
Q

What is the function of the urethra? (biology only)

A

Releases urine from the bladder, out of

the body

53
Q

What is a nephron? (biology only)

A

Functional unit of the kidney where
filtration and selective reabsorption takes
place

54
Q

Describe filtration in the kidneys (biology only)

A

● Blood flows through the glomerulus under high
pressure
● Small molecules (e.g. urea, glucose), water and
ions are filtered out of the blood and into the
Bowman’s capsule of the nephron

55
Q

Why do large molecules (e.g. red blood cells,

proteins) remain in the blood? (biology only)

A

They are too large to fit through the

pores in the capillary walls.

56
Q

Which substances are selectively reabsorbed from

the nephron tubule? (biology only)

A

● All sugars
● Some water
● Some ions

57
Q

What happens to the molecules not selectively

reabsorbed? (biology only)

A

They travel down the kidney tubule as
urine and are transported to the bladder
via the ureter. Here they are stored and
eventually excreted.

58
Q

How is the concentration and volume of urine

controlled? (biology only/higher)

A

controlled by the secretion of

anti-diuretic hormone (ADH)

59
Q

What produces ADH? (biology only/higher)

A

Pituitary gland

60
Q

Describe how ADH affects the reabsorption of water

from the kidney tubules (biology only/higher)

A

ADH increases the permeability of the
collecting ducts, enabling more water to
be reabsorbed into the blood.

61
Q

What is required to maintain the ideal water content

of blood? (biology only/higher)

A

A negative feedback system involving:

● Receptors in the hypothalamus
● Hypothalamus
● Effector i.e. pituitary gland

62
Q

Describe the negative feedback loop which occurs
when low blood water concentration is detected
(biology only/higher)
.

A

● Receptors detect low blood water content and send information to the
hypothalamus. This coordinates the information and sends instructions to the
pituitary gland.
● Pituitary gland increases ADH secretion. ADH increases collecting duct
permeability so more water is reabsorbed.
● Blood water content increases. More concentrated urine is produced

63
Q

Describe the negative feedback loop which occurs
when high blood water concentration is detected
(biology only/higher)

A

● Receptors detect high blood water content and send information to the
hypothalamus. This coordinates the information and sends instructions to the
pituitary gland.
● Pituitary gland secretes less ADH. Collecting duct becomes less permeable
so less water is reabsorbed.
● Blood water content decreases. More dilute urine is produced.

64
Q

How can kidney failure be treated? (biology only)

A

● Kidney dialysis

● Kidney transplant

65
Q

What is kidney dialysis? (biology only)

A

A machine artificially filters a patient’s blood.

66
Q

How does kidney dialysis work? (biology only)

A

● Selectively permeable barrier separates patient’s blood from
dialysis fluid

● Materials are exchanged across the barrier e.g. urea, excess
ions and water move out of the blood and into the dialysis fluid

● Large cells and proteins remain in the blood

67
Q

Describe the composition of dialysis fluid

biology only

A

● Same concentration of glucose and ions as in
normal blood plasma

● No urea

68
Q

What does a kidney transplant involve? (biology

only)

A

Taking a kidney from a living donor or
someone recently deceased and
implanting it into the patient.

69
Q

What is the risk associated with kidney transplants?

biology only

A

Risk of the body rejecting the

transplanted kidney

70
Q

What precautions are taken to minimise the risk of

rejection? (biology only)

A

● Tissue typing ensures that the transplanted
organ is ‘compatible’ with the recipient

● Immunosuppressant drugs help prevent the
immune system from rejecting the organ

Biology Paper 2 (9 decks)

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