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Edexcel Biology Gcse > homeostasis in humans > Flashcards

homeostasis in humans Flashcards

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1
Q

ADH

definition

A

A hormone produced in the pituitary gland that controls the volume and concentration of urine.

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2
Q

anti-coagulant drugs

definition

A

Substance that prevents blood clotting.

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3
Q

antigen

definition

A

A foreign organism that gets into the body and triggers an immune response.

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4
Q

blood plasma

definition

A

The liquid part of the blood containing useful things like glucose, amino acids, minerals, vitamins (nutrients) and hormones, as well as waste materials such as urea.

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5
Q

contract

definition

A

A muscle tenses as fibres shorten or create tension.

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6
Q

dialysis

definition

A

Medical treatment in which blood is removed from the body and filtered before being returned.

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7
Q

digestion

definition

A

The breakdown of large insoluble food molecules to smaller soluble ones.

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8
Q

effector

definition

A

The organ, tissue or cell that produces a response.

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9
Q

exhale

definition

A

Discharged as waste

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10
Q

homeostasis

definition

A

The maintenance of steady conditions. The ability of the body to maintain a constant internal environment, eg temperature and blood glucose concentration.

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11
Q

hypothalamus

definition

A

The part of the brain that detects changes in blood temperature and water concentration.

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12
Q

nerve impulses

definition

A

Electrical signals that travel along the nerve fibre from one end of the nerve cell to the other.

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13
Q

nervous system

definition

A

Body system that includes the brain, spinal cord and nerves.

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14
Q

osmoregulation

definition

A

A form of homeostasis which controls the volume of water in the body.

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15
Q

permiable

definition

A

A substance which allows fluids or gases to pass through it.

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16
Q

protease

definition

A

Enzyme that breaks down proteins.

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17
Q

receptor

definition

A

Organ, tissue or cell that detects a stimulus.

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18
Q

toxic

definition

A

Poisonous

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19
Q

urea

definition

A

A nitrogenous waste product resulting from the breakdown of proteins. It is excreted in urine.

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20
Q

vascoconstriction

definition

A

Narrowing of aterioles supplying the skin’s blood capillaries, causing less blood to flow.

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21
Q

vasodilation

definition

A

The increase in diameter of the skin arterioles to increase blood flow and increase heat loss by radiation.

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22
Q

Homeostasis
nervous system
hormones

A

The conditions inside our body must be carefully controlled to allow it to function effectively. Homeostasis is the maintenance of a constant internal environment in the body. The nervous system and hormones are responsible for controlling this.

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23
Q

The body control systems are all automatic, and involve both nervous and chemical responses. It has many important parts, including:
(basic)

A
  • Receptors
  • Coordination centres
  • Effectors
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24
Q

The body control systems are all automatic, and involve both nervous and chemical responses. It has many important parts, including:

A
  • Receptors detect a stimulus, which is a change in the environment, such as temperature change
  • Coordination centres in the brain, spinal cord and pancreas. They receive information from the receptors, process the information and instigate a response.
  • Effectors, such as muscles or glands create the response. Glands often release a hormone, which would restore the optimum condition again.
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25
Q

Receptor

definition

A

Receptors detect a stimulus, which is a change in the environment, such as temperature change

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26
Q

Coordination centre

definition

A

Coordination centres in the brain, spinal cord and pancreas. They receive information from the receptors, process the information and instigate a response.

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27
Q

Effector

definition

A

Effectors, such as muscles or glands create the response. Glands often release a hormone, which would restore the optimum condition again.

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28
Q

Body temperature

homeostasis

A

Body temperature is one of the factors that is controlled during homeostasis. The human body maintains the temperature that enzymes work best, which is around 37°C.

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29
Q

Body temperature

enzymes

A

If body temperature increases over this temperature, enzymes will denature and become less effective at catalysing important reactions, such as respiration.

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30
Q

Body temperature

A

Body temperature is one of the factors that is controlled during homeostasis. The human body maintains the temperature that enzymes work best, which is around 37°C.

If body temperature increases over this temperature, enzymes will denature and become less effective at catalysing important reactions, such as respiration.

This process is controlled by the thermoregulatory centre, which is contained in the hypothalamus in the brain, and it contains receptors sensitive to the temperature of the blood. The skin also has temperature receptors and sends nervous impulses back to the hypothalamus.

The hypothalamus responds to this information by sending nerve impulses to effectors in the skin to maintain body temperature

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31
Q

The skin contains three layers:

A

The epidermis, dermis and a layer of fatty tissue.

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32
Q

The skin

When we get too hot:

A

Sweat glands in the dermis release more sweat onto the surface of the epidermis. The sweat evaporates, transferring heat energy from the skin to the environment.

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33
Q

The skin

When we get too cold:

A

Skeletal muscles contract rapidly and we shiver. These contractions need energy from respiration, and some of this is released as heat. Nerve impulses are sent to the hair erector muscles in the dermis, which contract. This raises the skin hairs and traps a layer of insulating air next to the skin.

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34
Q

The control of body temperature is an example of a negative feedback mechanism. It regulates the amount of:

A
  • shivering (rapid muscle contractions release heat)

- sweating (evaporation of water in sweat causes cooling)

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35
Q

The amount of blood flowing through the skin capillaries is altered by what?

A

vasoconstriction and vasodilation.

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36
Q

vasodilation

definition

A

The increase in diameter of the skin arterioles to increase blood flow and increase heat loss by radiation.

A response to being too cold.

Heat lost by radiation

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37
Q

vasoconstriction

definition

A

Narrowing of aterioles supplying the skin’s blood capillaries, causing less blood to flow

A response to being too cold.

Little heat lost.

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38
Q

Osmoregulation

definition

A

Osmoregulation is the control of water levels and mineral ions (salt) in the blood.

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39
Q

Water content

osmoregulation

A

Water levels and mineral ions in the blood are controlled to keep the concentrations the same inside the cells as around them. This protects cells by stopping too much water from entering or leaving them by osmosis. If body cells lose or gain too much water, they do not function efficiently.

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40
Q

Water content
osmoregulation
concentration is too high outside the cell

A

If the concentration of water is the same inside and out the cells, they remain in their normal state. If the water concentration is too high outside, water enters the cell by osmosis and they may burst.

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41
Q

Water content
osmoregulation
concentration is too low outside the cell

A

On the other hand, if the water concentration is too low outside compared to the inside of the cells, water will leave by osmosis and the cells may shrivel. If body cells lose or gain too much water by osmosis they do not function efficiently.

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42
Q

Water content
osmoregulation
animal cell
hypotonic

A

More dilute solution out side the cell (hypotonic)

Cell swell, burst

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43
Q

Water content
osmoregulation
animal cell
hypertonic

A

More concentrated solution outside the cell (hypertonic)

Shrivelled cells

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44
Q

Water content
osmoregulation
Plant cell
hypotonic

A

More dilute solution outside the cell (hypotonic)

normal turgid cell

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45
Q

Water content
osmoregulation
Plant cell
hypertonic

A

More concentrated solution outside the cell (hypertonic)

Cytoplasm shrinks from the cell wall

46
Q

Human excretory organs are:

A

The organs of excretion in humans include the skin, lungs and kidneys.

47
Q

Human excretory organs

Water is lost from the body as:

A
  • sweat from the skin
  • water vapour, from the lungs when we exhale
  • urine from the kidneys
48
Q

What do sweat glands produce?

A

Sweat glands in the skin produce sweat. Water, ions and urea are lost from the skin as they are contained in sweat.

49
Q

Lungs

A

Water leaves the body via the lungs when we exhale as well as excess carbon dioxide.

We cannot control the level of water, ion or urea loss by the lungs or skin. For example, in a hot climate, your body sweats to help keep you cool. In the same way, when we breathe out we lose water vapour, and we cannot alter the amount we lose.

50
Q

Kidneys

A

The kidneys are organs of the urinary system - which removes excess water, mineral ions and urea. Our bodies can control the amount of water and ions removed by the kidneys. This is called osmoregulation.

51
Q

What happens when excessive amounts of protein are eaten?

A

When excessive amounts of protein are eaten, the excess amino acids produced from digesting proteins are transported to the liver from the small intestine. The liver controls the amino acid concentration in the body, as excess amino acids which need to be excreted safely. The body is unable to store proteins or amino acids.

52
Q

What happens in the liver when excessive amounts of protein are eaten?

A

In the liver, ammonia is formed by the deamination of amino acids. It is highly toxic and cannot be allowed to accumulate in the body. Excess ammonia is converted to urea. Urea and water are released from the liver cells in to the bloodstream and transported to the kidneys where the blood is filtered and the urea is passed out of the body in the urine.

53
Q

How is blood is transported to the kidney?

A

Blood is transported to the kidney through the renal artery. The blood is filtered at a high pressure and the kidney selectively reabsorbs any useful materials such as glucose, mineral ions and water. After it has been purified, the blood returns to the circulatory system through the renal vein.

54
Q

Maintaining water balance in the body

Kidneys

A

The kidneys are organs of the urinary system - which remove excess water, mineral ions and urea.

The kidneys produce urine and this helps maintain water balance. The urine is taken from the kidneys to the bladder by the ureters. The bladder stores the urine until it is convenient to expel it from the body.

55
Q

What are the ureters

A

The ureters are tubes that carry urine from the kidneys to the bladder.

56
Q

What is the urethra?

A

The urethra is the tube that carries urine out of the body.

57
Q

Maintaining water balance in the body
Kidneys
(step by step)

A
  • Renal artery carries oxygenated blood to the kidneys
  • Renal veins carries deoxygenated blood away from the kidneys
  • Kidneys regulates water content and filters blood
  • Ureter carries urine from the kidneys to the bladder
58
Q

Maintaining water balance in the body

Urine

A

Urine contains water, urea and mineral ions. Urea is produced in the liver when excess amino acids are broken down. Urea is the main waste product removed in the urine, as it is not reabsorbed in the kidney.

59
Q

Maintaining water balance in the body
The nephron
The role of the kidney

A

Each kidney contains over one million microscopic filtering units called nephrons. Each nephron is made of a tubule and is responsible for ‘cleaning’ the blood by removing urea, excess water and mineral ions.

60
Q

Maintaining water balance in the body
The nephron

The kidney works in a number of different stages:

A

Stage 1 - Filtration

Stage 2 - Selective reabsorption

Stage 3 - The formation of urine

61
Q

Maintaining water balance in the body
The nephron
The kidney works in a number of different stages

Stage 1 - Filtration

A

Blood passes into the many capillaries inside the kidney. The blood is under high pressure at the start of the nephron, which helps the ultrafiltration of the blood. Small molecules are squeezed out and pass into the nephron tubule. These small molecules include urea, water, ions, and glucose. However, large molecules, such as blood proteins, are too big to fit through the capillary wall and remain in the blood.

62
Q

Maintaining water balance in the body
The nephron
The kidney works in a number of different stages.

Stage 2 - Selective reabsorption

A

Having filtered out small essential molecules from the blood - the kidneys must reabsorb the molecules which are needed, while allowing those molecules which are not needed to pass out to form urine. Therefore, the kidneys selectively reabsorb only those molecules which the body needs back in the bloodstream.

63
Q

Maintaining water balance in the body
The nephron
The kidney works in a number of different stages
Stage 2 - Selective reabsorption

The reabsorbed molecules include:

A
  • all of the glucose which was originally filtered out
  • as much water as the body needs to maintain a constant water level in the blood plasma
  • as many ions as the body needs to maintain a constant balance of mineral ions in the blood plasma
64
Q

Maintaining water balance in the body
The nephron
The kidney works in a number of different stages

Stage 3 - The formation of urine

A

The molecules which are not selectively reabsorbed (the urea, excess water and ions) continue along the nephron tubule as urine. This eventually passes down to the bladder.

In carrying out these processes, the kidney is able to fulfil its functions of regulating the water and ion balance of the blood plasma, as well as keeping the level of urea low.

65
Q

What does the hypothalamus?

A

The hypothalamus detects changes in the blood plasma.

66
Q

What is ADH?

A

anti-diuretic hormone

67
Q

What gland regulates the release of the anti-diuretic hormone, known as ADH?

A

pituitary gland

68
Q

ADH

A

Different amounts of ADH are released into the bloodstream according to the concentration of water in the blood plasma. ADH is released by the pituitary gland when the blood is too concentrated and it causes the kidney tubules to become more permeable. This allows more water to be reabsorbed back into the blood during selective reabsorption.

69
Q

ADH

What happens if a person consumes a large volume of water and has not lost much as sweat?

A

If a person has consumed a large volume of water and has not lost much as sweat, too much water might be detected in the blood plasma. If this occurs, less ADH will be released, which results in less water being reabsorbed and a dilute and larger volume of urine will be produced.

70
Q

ADH
Too much water in blood.
(step by step)

A

1) Hypothalamus detects water level
2) Pituitary gland releases less ADH
3) Less water reabsorbed by kidneys
4) More water lost in urine

Blood water level returns to normal

71
Q

ADH

What happens if a person becomes too hot and sweats a lot, but doesn’t drink enough water to replace what was lost?

A

If a person becomes too hot and sweats a lot, but doesn’t drink enough water to replace what was lost, too little water might be detected in the blood plasma. More ADH will be released, which results in water being reabsorbed and a more concentrated but smaller volume of urine will be produced.

72
Q

ADH
To little water in blood
(step by step)

A

1) Hypothalamus detects water level
2) Pituitary gland releases ADH
3) More water reabsorbed by kidneys
4) Less water lost in urine

Blood water level returns to normal

73
Q

What is the problem if there is a hich concentration of plasma?

A

Too little water

74
Q

What is the problem if there is a low concentration of plasma?

A

Too much water

75
Q

What happens to the rate of release of ADH if plasma concentration is high?

A

ADH release increases

76
Q

What happens to the rate of release of ADH if plasma concentration is
low?

A

ADH release decreases

77
Q

What happens to the rate of release of ADH if plasma concentration is low?

A

ADH release decreases

78
Q

What is the effect of ADH if plasma concentration is high?

A

More water is reabsorbed by nephrons.

79
Q

What is the effect of ADH if plasma concentration is low?

A

Less water is reabsorbed by nephrons.

80
Q

What is the effect on urine if plasma is of high concentration?

A

Urine is more concentrated

81
Q

What is the effect on urine if plasma is of low concentration?

A

Urine is more dilute

82
Q

What is negative feedback?

A

A negative feedback control system responds when conditions change from the ideal or set point and returns conditions to this set point. There is a continuous cycle of events in negative feedback.

83
Q

What is the role of the kidneys?

A

The kidneys are responsible for the removal of waste products from the blood.

84
Q

What happens if the kidneys are damaged?

A

Damage from accidents or disease can lead to a build-up of poisonous wastes in the body.

85
Q

Treatment for total kidney failure.

A

Treatment is available for kidney failure and can be by organ transplant or by using kidney dialysis.

86
Q

What is kidney dialysis

overview

A

In this procedure, patients are connected to a dialysis machine which acts as an artificial kidney to remove most of the urea and restore or maintain the water and ion balance of the blood.

87
Q

When would kidney dialysis be necessary?

A

Patients with kidney failure can be kept alive by using kidney dialysis until a transplant becomes available.

88
Q

Kidney dialysis

detailed

A

Unfiltered blood that is high in urea is taken from a blood vessel in the arm, mixed with blood thinners or an anti-coagulant to prevent clotting, and pumped into the dialysis machine. Inside the machine the blood and dialysis fluid are separated by a partially permeable membrane the blood flows in the opposite direction to dialysis fluid, allowing a concentration gradient to exist and exchange of substances to occur.

As the dialysis fluid has no urea in it, there is a large concentration gradient - meaning that urea moves across the partially permeable membrane, from the blood to the dialysis fluid, by diffusion. This is very important as it is essential that urea is removed from the patients’ blood.

As the dialysis fluid contains a glucose concentration equal to a normal blood sugar level, this prevents the net movement of glucose across the membrane as no concentration gradient exists. This is very important as the patients’ need to retain glucose for respiration.

As the dialysis fluid contains an ion concentration similar to the ideal blood plasma concentration, movement of ions across the membrane only occurs where there is an imbalance.

  • if the patient’s blood is too low in ions, they will diffuse from the dialysis fluid into the blood, restoring the ideal level in the blood
  • if the patient’s blood is too high in ions, the excess ions will diffuse from the blood to the dialysis fluid
89
Q

What does dialysis fluid contain?

A
  • a glucose concentration similar to a normal level in the blood
  • a concentration of mineral ions similar to that found in normal blood plasma
  • no urea
90
Q

Kidney dialysis
advantages

Kidney dialysis allows a person with kidney failure to maintain their health. The overall effect of this is that the blood leaving the machine and returning into the patient’s arm will have:

A
  • greatly reduced levels of urea – it is ‘cleaned blood’
  • no overall change in blood glucose levels
  • the correct water and ion balance maintained or restored (with only excess ions removed)
91
Q

Kidney dialysis

Disadvantages

A

Kidney dialysis requires highly specialised and expensive machinery. The patient must be connected to this machinery 2-3 times a week for periods (on average) of between 4-6 hours at a time. This is time consuming and restrictive, as this mainly happens in hospital.

As the filtration only works when they are connected, kidney patients must monitor their diet carefully in between dialysis sessions. They need to avoid eating foods with a high salt content or a high protein content as excess amino acids are broken down into urea. This again can be difficult to control and monitor, but will help maintain the health of the patient.

Finally, dialysis will only work for a limited amount of time before a transplant is needed, and sadly many patients will die before a suitable one is found.

92
Q

Treating kidney failure by transplant

overview

A

Kidney transplantation is an alternative method for treating kidney failure and can save a patient’s life. This procedure involves implanting a kidney from an organ donor into the patient’s body to replace the damaged kidney. This is better than using a restrictive dialysis machine, as the recipient can lead a normal life afterwards.

93
Q

Treating kidney failure by transplant

Antigens

A

As with all cells, the donor kidney cells will have protein antigens on their surface. Antigens are unique to each of us (with the exception of identical twins), and allow our body to identify our own cells from those of potential pathogens.

94
Q

Treating kidney failure by transplant

Organ rejection

A

Differences in the antigens of the donor kidney cells and those of the patient receiving the transplant would mean that the patient’s immune system would quickly form antibodies against the kidney cell antigens, and would ultimately destroy the kidney. This is known as organ rejection. This is potentially very harmful for the patient.

95
Q

Treating kidney failure by transplant

Two precautions can be taken to reduce organ rejection:

A
  • Tissue typing
  • Immuno-suppressant drugs

Even with these two precautions, most donor kidneys will only survive for an average period of 8-9 years before the patient will require a further transplant or a return to dialysis.

96
Q

Precautions against rejection

Tissue typing

A

a kidney is given to patients who have antigens that are very similar to the antigens of the donor kidney. This can lead to long waits for transplants while compatible donors become available - during which time patients must undergo dialysis, and in some cases they will die before a match is found.

97
Q

Precautions against rejection

Immuno-suppressant drugs

A

these drugs must be taken by transplant patients for the rest of their lives. They suppress the immune system, greatly reducing the immune response against the donor kidney. The negative effect of this is that it also suppresses the immune response against pathogens which enter the body, increasing the risk of infections.

98
Q

Kidney transplant

advantages

A
  • Patients can lead a more normal life without having to watch what they eat and drink
  • Cheaper for the NHS
99
Q

Dialysis

advantages

A
  • available to all kidney patients

- No need for immune-suppressant drugs

100
Q

Kidney transplant

disadvantages

A
  • Must take immune-suppressant drugs which increase the risk of infection
  • Shortage of organ donors
  • Kidney only lasts 8-9 years on average
  • Any operation carries risks
101
Q

dialysis

advantages

A
  • Patient must limit their salt and protein intake between dialysis sessions
  • Expensive for the NHS
  • Regular dialysis sessions - impacts on the patient’s lifestyle
102
Q

What is thermoregulation?

A

Control of body temperature

103
Q

Which part of the brain controls temperature?

A

The hypothalamus contains the thermoregulatory centre and controls temperature.

104
Q

How does sweat keep us cool?

A

As sweat evaporates it takes heat energy away. We sweat when we are hot.

105
Q

Which of these substances is removed from the blood by the kidneys?

A

Urea is removed from the blood by the kidneys.

106
Q

What is urine?

A

Urine is the liquid which contains the urea.

107
Q

What is reabsorbed back into the blood by the kidneys?

A

Glucose and water

108
Q

What is the part of the nephron responsible for filtration?

A

Glomerulus and Bowman’s capsule

109
Q

What does the collecting duct do?

A

The collecting duct reabsorbs water.

110
Q

ADH is released from the pituitary in response to?

A

Decreased water content of the blood.

111
Q

ADH increases permeability of which structure?

A

Collecting duct.

112
Q

What does the glomerulus do?

A

The glomerulus filters the blood.

Edexcel Biology Gcse (36 decks)

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