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Biology > Homeostasis > Flashcards

Homeostasis Flashcards

1
Q

What is the definition of homeostasis?

A

The regulation of internal conditions in a cell or organism to give optimum conditions for it to function in response to internal and external changes.

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2
Q

What is it in cells and organisms that needs optimal conditions?

A

Enzymes work best in their optimum conditions, and most reactions inside cells and organisms involve enzymes.

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3
Q

What exactly is controlled during homeostasis in humans?

A

Blood glucose concentration, body temperature and water levels.

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4
Q

What are the automatic control systems in the body for homeostasis?

A

The nervous system and the endocrine (hormonal) system.

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5
Q

What three parts do all control systems have?

A

Receptor cells, coordination centres and effectors.

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6
Q

What is a receptor cell?

A

Any cell that can detect changes in the environment. These changes are called stimuli (singular is stimulus).

e.g. Chemical receptor cells on the tongue.

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7
Q

What is a coordination centre?

A

An area of the body that receives and processes the information from the receptors.
e.g. brain, spinal cord, pancreas.

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8
Q

What is an effector?

A

Effectors cause the response to happen so that the body is returned to optimum levels.

e.g. Muscles and glands.

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9
Q

What is a neurone?

A

A nerve cell. They are quite long and thin, and they can transmit information as electrical impulses.

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10
Q

What is the CNS?

A

The central nervous system. It is made of two parts, the brain and the spinal cord.

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11
Q

What happens at the CNS?

A

The CNS receives impulses from the receptor cells and then sends impulses out to the effectors.
The effect would be a muscle contracting or a gland secreting a hormone.

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12
Q

What is the order of the pathway of a reflex arc?

A

Stimulus > Receptor > Coordinator > Effector > Response.

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13
Q

What are the three neurones called in a reflex arc?

A

Sensory neurone, Relay neurone and Motor neurone.

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14
Q

What is the role of a sensory neurone?

A

Sensory neurones transmit an electrical impulse from the receptor cell to the CNS.

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15
Q

What is the role of a relay neurone?

A

Relay neurones are found in the CNS, usually in the spinal cord. It takes the information from the sensory neurone and passes the information to the motor neurone.

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16
Q

What is the role of a motor neurone?

A

Motor neurones transmit an electrical impulse from the CNS to the effector (a muscle or a gland).

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17
Q

What is a synapse?

A

Synapses are tiny gaps between neurones. As the electrical signal can’t pass across the gap, the information is converted into chemicals called neurotransmitters.

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18
Q

How do neurotransmitters cross a synapse?

A

Neurotransmitters move across a synapse by DIFFUSION. When they reach the next neurone, they cause a new electrical impulse to be sent.

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19
Q

Why does the speed slow down when an impulse reaches a synapse?

A

The electrical impulse is much faster than the chemical neurotransmitter, so every synapse slows the speed of the overall reaction.

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20
Q

Why do reflexes help reduce damage by injury?

A

They are automatic and rapid so they don’t involve the conscious part of the brain. The response is quicker than if the impulse travelled to the brain, so less damage happens.

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21
Q

What sort of factors slow down reaction times?

A

Alcohol, depressant drugs, tiredness and dehydration can all slow down the speed of a reaction. Stimulant drugs can speed up reactions.

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22
Q

What is the required practical for reaction times?

A

Measuring how fast someone reacts by doing a computer reaction test, or dropping a ruler and measuring how many cm have dropped before they catch it.

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23
Q

What is the endocrine system?

A

The system of glands that release hormones directly into the bloodstream. This leads to slower responses than the nervous system, but the effects last for longer.

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24
Q

What is a hormone?

A

A chemical that travels in the blood to a target organ where it produces an effect.

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25
Q

What is a target organ?

A

The organ of the body where the chemical hormone will have an effect. Each hormone has its own target organ.

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26
Q

Why is the pituitary gland so important?

A

The pituitary gland is a ‘master gland’ as it produces several different hormones that can then make other glands produce hormones too, which cause effects.

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27
Q

Which glands do I need to know/label for GCSE?

A

Pituitary gland, Pancreas, Thyroid, Adrenal gland, Ovaries, Testes.

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28
Q

Which hormonal controls do I need to know for GCSE?

A

The control of blood glucose levels, and the control of human reproduction (including how we develop contraceptives).

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29
Q

What does the pancreas do?

A

It monitors and controls blood glucose levels.

30
Q

What are the hormones produced by the pancreas?

A

Insulin (when blood glucose is too high) and Glucagon (when blood glucose is too low…remember you produce glucagon when your glucose is gone).

31
Q

When is insulin produced?

A

When levels of glucose in the blood get higher than they should be, the pancreas produces insulin.

32
Q

What does insulin do?

A

Insulin travels in the bloodstream to the liver where it causes liver and muscle cells to take in glucose and convert it to glycogen for storage.

33
Q

What does glucagon do?

A

Glucagon travels in the bloodstream and causes glycogen stores to be converted back to glucose which is then released back into the blood.

34
Q

What is negative feedback in blood glucose control?

A

The pancreas is constantly monitoring glucose levels in the blood, and the two hormones insulin and glucagon are constantly causing their own inhibition.

35
Q

What is diabetes?

A

A disorder where the blood glucose levels are not properly controlled. There are two types of diabetes.

36
Q

What is Type 1 diabetes?

A

A disorder where the pancreas does not produce sufficient insulin. Blood glucose levels can get extremely high.

37
Q

How is Type 1 diabetes treated?

A

Regular insulin injections and careful diet control are needed to treat Type 1 diabetes.

38
Q

What is Type 2 diabetes?

A

A disorder where liver and muscle cells no longer respond to insulin produced by the pancreas. Obesity increases the risk of developing Type 2 diabetes.

39
Q

How is Type 2 diabetes treated?

A

Exercise and careful diet control (with limited carbohydrates) are usual treatments. Some patients need tablets or injections as well as this.

40
Q

When do people get diabetes?

A

Type 1 is usually diagnosed in childhood. Type 2 occurs in older people who have become obese.

41
Q

What are the hormones in the human reproductive system?

A

Testosterone in men; Oestrogen, progesterone,(FSH) and (LH) in women.

42
Q

When do humans start making reproductive hormones?

A

During puberty, and they cause secondary sex characteristics to develop (breasts,pubic hair etc)

43
Q

What does testosterone do?

A

Testosterone causes men to produce sperm. Sperm production starts during puberty.

44
Q

What is the menstrual cycle?

A

The development and release of an egg cell, plus the development of the uterus lining each month.

45
Q

What is ovulation?

A

The release of an egg cell from an ovary.

46
Q

What does FSH do?

A

FSH is released from the pituitary gland and causes one egg cell to mature inside the ovary.

47
Q

What does LH do?

A

LH is released from the pituitary gland and causes the mature egg cell to be released.

48
Q

What do oestrogen and progesterone do?

A

Oestrogen (produced by the ovary) and progesterone (produced by the uterus) are involved in maintaining the uterus lining (ready for an embryo to develop and grow).

49
Q

What order are the menstrual cycle hormones released in?

A

FSH (from pituitary) causes production of oestrogen; Oestrogen (from ovary) causes FSH production to stop and LH production to start; LH (from pituitary) causes egg release.

50
Q

When should LH levels be highest?

A

LH levels will be highest when ovulation occurs.

51
Q

What is a contraceptive?

A

Any method that reduces the chance of a female becoming pregnant.

52
Q

What are the non-hormonal methods of contraception?

A

• Barrier methods (condoms and diaphragms)
• Spermicides
• Intra-uterine devices
• Abstaining
• Surgery to sterilise the male or the female

53
Q

What are the hormonal methods of contraception?

A

• Oral contraceptives (these inhibit FSH production, so no egg matures)
• Implants/patches/injections (these release progesterone slowly so no egg matures)

54
Q

How do hormones help treat infertility?

A

Fertility drugs contain FSH and/or LH which make the woman produce a mature egg. She can then become pregnant naturally.

55
Q

How are hormones used in IVF treatment?

A

Women are given high doses of FSH and LH so several eggs mature at the same time.

56
Q

How does IVF work once the eggs are mature?

A

The eggs are collected from the mother and fertilised by the father’s sperm in the laboratory. They develop into embryos and can be inserted back into the mother’s uterus.

57
Q

What are the benefits of IVF treatment and fertility drugs?

A

The woman and man have a chance to have their own baby.

58
Q

What are the negatives of IVF treatment?

A

• It is emotionally and physically stressful
• Success rates are not high
• It can lead to multiple births which are high risk for both mother and babies.

59
Q

Where is adrenaline produced, and when do we produce it?

A

Adrenaline is produced by the adrenal glands when we are stressed or in times of fear.

60
Q

What does adrenaline do in the body?

A

Adrenaline increases heart rate and boosts the supply of oxygen and glucose to the brain and to muscles, preparing the body for ‘fight or flight’.

61
Q

Where is thyroxine produced?

A

Thyroxine is produced by the thyroid gland.

62
Q

What does thyroxine do in the body?

A

Thyroxine stimulates basal metabolic rate (how fast reactions happen in the body), and also plays an important role in growth and development.

63
Q

What is negative feedback in thyroxine control?

A

Thyroxine levels are controlled by negative feedback. Too much thyroxine produced will slow down the production of more thyroxine.

64
Q

When measuring a reflex response, what equipment would you need?

A

Metre ruler, chair and table.

65
Q

When measuring a reflex response, the catcher uses their ‘dominant hand’. What does this mean?

A

It’s the hand they write with. We use this to make sure that we don’t disadvantage left handed students.

66
Q

What unit do we use to measure the distance the ruler has travelled?

A

cm or mm. We do NOT measure the time.

67
Q

Why do we measure the reflex response a large number of times?

A

To obtain a reliable mean.

68
Q

What if one of the results is very different to the other values and doesn’t fit the pattern or trend?

A

We ignore that value and it is NOT included in our mean. It’s anomalous.

69
Q

What are the factors that can affect the reaction times of the metre ruler catching experiment?

A

Caffeine intake, fatigue, age, experience in catching.

70
Q

What can we do with the average data from the metre ruler?

A

Use a conversion table to estimate the reaction time in seconds or milliseconds.

Biology (7 decks)

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