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Josh Lee Biology > Topic 5 - Homeostasis > Flashcards

Topic 5 - Homeostasis Flashcards

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1
Q

What is homeostasis?

A

The regulation of your internal body conditions to maintain a stable environment in response to changes in external and internal conditions.

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2
Q

What regulates your internal environment?

A

Automatic control systems

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3
Q

What are the 3 main components of a control system?

A

Receptors
Coordination centres
Effectors

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4
Q

What is negative feedback?

A

A mechanism used by control systems to keep your internal environment stable. When a level of something gets too high or low, your body uses negative feedback to get it back to normal.

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5
Q

What is the process of negative feedback? (Three steps)

A

1) Receptor detects stimulus level too high/low.
2) Coordination centre receives and processes information, then organises a response.
3) Effector produces response which counteracts change and restores optimum level.

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6
Q

Why do internal body conditions need to be regulated?

A

In order for your cells to function properly.

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7
Q

What is the function of the nervous system?

A

To detect and react to stimuli

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8
Q

What are the parts of the nervous system?

A

CNS (central nerve system)
Sensory neurones
Motor Neurones
Effectors

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9
Q

What is the CNS?

A

In vertebrates its the brain and spinal cord only.

In mammals cns is connected to the body by sensory and motor neurones.

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10
Q

What are sensory neurones?

A

Neurones that carry information as electrical impulses from receptors to CNS

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11
Q

What are motor neurones?

A

Neurones that carry information as electrical impulses from CNS to effectors.

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12
Q

Whats an effector?

A

All your muscles and glands which respond to nervous impulses.

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13
Q

What would be the whole pathway of nervous system response to stimulus?

A 
Stimulus
Receptor
Sensory neurone
CNS
Motor neurone
Effector
Response
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14
Q

Whats a synapse?

A

The connection between 2 neurones.

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15
Q

How do nerve signals transfer from one neurone to another via a synapse?

A

Nerve signal is transferred by chemicals which diffuse across the gap between the neurones. The chemicals set off new electrical signal in next neurone.

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16
Q

What is a reflex?

A

A rapid, automatic response to certain stimuli that dont involve the conscious part of the brain. They reduce the chances of you getting injured.

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17
Q

What are the steps of a reflex arc?

A

Stimulus (eg bee stings finger)
Stimulation of pain receptor
Impulses travel along sensory neurone until synapse between relay neurone.
Impulses passed along relay neurone via a synapse (through the chemicals).
When impulses reach synapse between relay neurone and motor neurone impulses transferred through chemicals again.
Impulses travel along motor neurone to effector.
Muscle then contracts and moves hand away.

This is quicker as you dont have to think about the response.

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18
Q

Whats the brain made up of?

A

Billions of interconnected neurones.

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19
Q

What are the different regions of the brain and their function?

A

Cerebral cortex - Responsible for consciousness, intelligence, memory, language.

Medulla - Responsible for unconscious activities eg breathing and heartbeat.

Cerebellum - Responsible for muscle coordination

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20
Q

What are the 3 methods scientists use to study the brain? Explain them in detail.

A

Studying patients with brain damage - If small part of brain has been damaged, the effect on the patient can tell you a lot about what the damaged part of the brain does.

Electrically stimulating the brain - Brain can be electrically stimulated by pushing a tiny electrode into the tissue and giving it a small zap of electricity. You can observe what stimulating different parts of the brain does to the person.

MRI Scans - A magnetic resonance imaging scanner is a machine that can produce a very detailed picture of the brains structures. Scientists use it to see what parts of the brain are active when people are doing things (eg listening to music)

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21
Q

What are benefits and risks of studying the brain?

A

Benefits - Knowledge of brain has led to development of treatments for disorders of the nervous system. Eg electrical stimulation of brain can help reduce muscle tremors caused by nervous system such as Parkinsons disease.

Risks - Risk of physical damage to the brain or increased problems with brain function (eg difficulties with speech)

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22
Q

What are the different parts of the eye?

A 
Sclera
Cornea
Iris
Lens
Ciliary muscles
Suspensory ligaments
Optic nerve
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23
Q

What is the sclera?

A

The tough, supporting wall of the eye

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24
Q

What is the cornea?

A

Transparent outer layer found at front of eye. Refracts light into the eye.

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25
Q

What is the iris?

A

The iris contains muscles that allow it to control the diameter of the pupil and therefore how much light enters the eye.

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26
Q

What is the lens?

A

Focuses light onto the retina (which contains receptor cells sensitive to light intensity and colour)

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27
Q

What do ciliary muscles and suspensory ligaments do?

A

Change the shape of the lens

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28
Q

What does the optic nerve do?

A

Carries impulses from receptors on retina to the brain.

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29
Q

What is the iris reflex? (In the eye)

A

When light receptors in eye detect very bright light, a reflex makes the pupil smaller. The circular muscles in the iris contract and radial muscles relax. This reduces amount of light that can enter the eye.

Opposite for dim light.

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30
Q

How does the eye use accommodation reflex to focus on near and distant objects?

A

Near objects:

Ciliary muscles contract. Suspensory ligaments relax.
Lens becomes more curved.
Increases the amount by which it refracts light.

Distant:

Opposite

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31
Q

What are some people long sighted?

A

Long sighted people are unable to focus on near objects.

Occurs when lens is wrong shape and doesnt refract light enough or eyeball too short.

Images of near objects focuses behind the retina.

Use glasses with convex lens (curves outwards) to correct. Light rays now focus on the retina

32
Q

Whats the medical term for long sightedness?

A

Hyperopia

33
Q

Why are some people short sighted?

A

Unable to focus on distant objects.

Occurs when lens is wrong shape and refracts light too much or eyeball is too long.

Images of distant objects are focused in front on the retina.

Use glasses with concave lens (curves inwards) to correct so light rays focus on retina.

34
Q

Whats the medical term for being short sighted?

A

Myopia

35
Q

What are alternative ways from glasses to treat vision defects?

A

Contact lenses - thin lenses that sit on the surface of the eye. Lightweight and almost invisible.
More convenient than glasses for activities like sport.
Can get hard lenses and soft lenses.
Soft lenses more comfortable but higher risk of infection.

Laser eye surgery - laser used to vaporise tissue, changing the shape of the cornea.
Slimming cornea makes it less powerful so improves short sight.
Changing shape to be more powerful improves long sight.
Risk of complications such as infection or eye reacting in a way which makes vision worse.

Replacement lens surgery - natural eye lens removed and artificial lens replaces it.
Higher risks than laser eye surgery, including possible damage to retina which could lead to loss of sight.

36
Q

What is the bodys optimum temperature for enzymes to work? (Body temperature)

A

37°c

37
Q

What is the function of the thermoregulatory system?

A

In the brain. Contains receptors that are sensitive to temperature of blood flowing through the brain. Also receives impulses from temperature receptors in the skin, giving skin temperature.

Acts as coordination centre

38
Q

What are responses to too high body temperature?

A

Sweat glands are the effectors. They produce sweat which evaporates from skin. This transfers energy to environment.

Blood vessels supplying the skin dilate so more blood flows close to surface of skin. This is called VASODILATION. Helps energy transfer from skin to environment

39
Q

What are responses to body temperature being too low?

A

Hairs stand up to trap an insulating layer of air.

No sweat

Blood vessels supplying the skin capillaries constrict to close off skins blood supply. This is VASOCONSTRICTION.

You shiver. This needs respiration which transfers some energy to warm the body.

40
Q

What are hormones?

A

Hormones are chemical molecules released directly into the blood. They affect particular cells in particular organs. Control things in organs and cells that need constant adjustment.

Long lasting effects

Secreted by glands called endocrine glands. These glands make up the endocrine system.

41
Q

What are some glands that make up the endocrine system?

A 
Pituitary gland
Thyroid
Adrenal gland
Ovaries
Pancreas
Testes
42
Q

Whats the function of the pituitary gland?

A

Produces many hormones that regulate body conditions.

Some hormones act on other glands, making them produce hormones.

43
Q

What do the ovaries do?

A

Produce oestrogen, involved in the menstrual cycle.

44
Q

What do the testes do?

A

Produce testosterone, which controls puberty and sperm production

45
Q

What does the thyroid gland do?

A

Produces thyroxine which is involved in regulating things like rate of metabolism, heart rate and temperature.

46
Q

What does the adrenal gland do?

A

Produces adrenaline which is used to prepare for ‘fight or flight’ response.

47
Q

What does the pancreas (gland) do?

A

Produces insulin, which is used to regulate blood glucose level.

48
Q

What is the difference between nerves and hormones?

A

Nerves:

Very fast action
Act for very short time
Act on very precise area

Hormones:

Slower action
Act for longer time
Act in more general way

49
Q

How is blood glucose level controlled?

A

Controlled by the pancreas which adds insulin into blood if too high or glucagon if too low.

Insulin makes liver turn glucose into glycogen which can be stored in the liver, decreasing blood glucose levels.

Glucagon makes liver turn glycogen into glucose which increases blood glucose levels

50
Q

What is type 1 diabetes?

A

Pancreas produces little or no insulin. A persons blood glucose level can rise dangerously high.

Treated with insulin injections, most likely at meal times which makes sure glucose from blood is removed quickly once food has been digested.

Limit intake of simple carbohydrate foods.

Exercise.

51
Q

What is diabetes?

A

Condition that affects your ability to control blood glucose level.

52
Q

What is type 2 diabetes?

A

Person becomes resistant to their own insulin. Cause blood glucose levels to rise too high.

Being overweight can increase your chances of getting it. (Obesity is a risk factor)

Can be controlled by eating a carbohydrate controlled diet and getting regular exercise.

53
Q

What is the function of the kidneys?

A

They make urine by taking waste products out of your blood. Substances filtered put of the blood as it passes through kidneys. (Filtration). Useful substances are diffused back into blood. This process is SELECTIVE REABSORPTION.

54
Q

What are the substances removed from the body in urine?

A

Urea - Proteins cant be stored by the body so excess amino acids convert into fat and carbohydrates which can be stored. This process is DEAMINATION.

Ammonia is a waste product from this process. Its toxic so converted to urea in liver. Urea is transported to kidneys where its filtered out of blood and excreted through urine.

Ions - Ions such as sodium are taken into the body in food, and then absorbed into the blood.

If ion or water content in body is wrong it could upset balance between water and ions, meaning too much or little water is drawn into cells by osmosis. This can damage cells.

Water - Body has to balance the water coming in against water going out.

We lose water from skin in swear and lungs when we breathe out.

Amount of water is balanced by amount we consume and amount removed by kidneys in urine.

55
Q

How is concentration of urine controlled?

A

Controlled by a hormone called anti-diuretic hormone(ADH) which is released into bloodstream by pituitary gland.

Brain monitors water content of blood and instructs pituitary gland when to release ADH.

If water content is too high, less ADH produced so less water reabsorbed from kidney tubules.

If water content too low, more ADH produced so more water gets reabsorbed from kidney tubules.

56
Q

What would happen if kidney failure wasnt treated?

A

Waste substances would build up in your blood and you would lose your ability to control the level of ions and water in your body.
Eventually you would die,

57
Q

How can dialysis treatment help someone with kidney failure?

A

Has to be done regularly to keep concentration of dissolved substances in the blood at normal levels and remove waste substances.

In a dialysis machine the persons blood flows between partially permeable membrane, surrounded by dialysis fluid.

Dialysis fluid has same concentration of dissolved ions and glucose as healthy blood. So only waste substances diffuse across the barrier.

Can cause blood clots or infections.
Expensive for NHS.
Useful whilst waiting for donor kidney

58
Q

How do kidney transplants work?

A

The only cure to kidney failure.

Risk that donor kidney could get rejected by patient immune system.

Cheaper than dialysis but long waiting list.

59
Q

What is puberty?

A

When your body starts releasing sex hormones that trigger off secondary sexual characteristics and cause eggs to mature im women.

60
Q

What is the reproductive hormone in men? And women?

A

In men its testosterone. Produced by testes and stimulates sperm production.

In women its oestrogen . Produced by ovaries

61
Q

What are the 4 stages of the menstrual cycle?

A

1) Day 1 - Menstruation starts. The uterus lining breaks down for about 4 days.
2) Uterus lining builds up again, from day 4 to 14, into a thick spongey layer full of blood vessels, ready to receive a fertilised egg.
3) An egg develops and is released from the ovary at day 14. This is OVULATION.
4) The wall is maintained for about 14 days till day 28. If no fertilised egg has landed on uterus wall by day 28, the spongy lining starts to break down and whole cycle starts again.

62
Q

How is the menstrual cycle controlled by 4 hormones?

A

1) FSH (Follicle-Stimulating hormone)
Produced in pituitary gland
Causes an egg to mature in one of the ovaries in a structure called a follicle.
Stimulates ovaries to produce oestrogen.

2) Oestrogen
Produced in ovaries
Causes lining of uterus to grow
Stimulates release of LH

3) LH (luteinising hormone)
Produced in pituitary gland
Stimulates release of an egg (ovulation)

4) Progesterone
Produced in ovaries by remains of the follicle after ovulation
Maintains lining of uterus during 2nd half of cycle.
When progesterone falls, the lining breaks down.
Inhibits release of LH and FSH

63
Q

How can hormones be used to reduce fertility?

A

Oestrogen can be used to prevent the release of an egg (can be used as contraception). If taken everyday it inhibits production of FSH so after a while egg development and production stop.

Progesterone stimulates production of thick mucus which prevents sperm getting to egg.

This pill is an oral contraceptive containing oestrogen and progesterone.
Over 99% effective.
Side effects like headaches and nausea and doesnt protect against STDS.

Progesterone only pill which is just as effective with less side effects.

Other methods:

Contraceptive patch contains oestrogen and progesterone and is a small patch stuck to skin. Lasts a week.

Contraceptive implant inserted under skin of arm. Releases progesterone which stops ovulation. Can last 3 years.

Contraceptive injection contains progesterone. Each dose lasts 2-3 months.

Intrauterine device (IUD) is a device inserted into uterus to kill sperm and prevent implantation of fertilised egg. Plastic ones release progesterone and copper ones prevent sperm surviving.

64
Q

How do barriers stop sperm and egg meeting?

A

Condoms - Worn over penis to prevent sperm from entering vagina. Only form of contraception to prevent STDs.

Diaphragm - Shallow plastic cup that fits over cervix to form a barrier. Used with spermicide.

Spermicide can be used alone as a form of contraception but not as effective.

65
Q

What are some drastic ways to prevent pregnancy?

A

Sterilisation - Cutting or tying fallopian tubes in female, or sperm duct, in male. Permanent.

Natural methods - Finding out when woman is most fertile and avoiding sex on those days. Not very effective.

Abstinence - Only way to be completely sure that sperm and egg dont meet is by not having sex.

66
Q

How can hormones be used to increase fertility?

A

FSH and LH can be given to stimulate ovulation.

Helps a lot of women get pregnant when they couldnt before.

Doesnt always work.
Too many eggs could be stimulated (twins, triplets etc)

67
Q

How does IVF work?

A

1) Collect eggs from womans ovaries and fertilise them in a lab using a mans sperm or inject sperm directly into them.
2) Fertilised eggs are grown into embryos in a laboratory incubator.
3) Once the embryos are tiny balls of cells, one or two are transferred back to womans uterus
4) FSH and LH are given before egg collection to stimulate several eggs.

68
Q

What are pros and cons of IVF?

A

Pros - Can give infertile couple a child

Cons - Multiple births can happen is more than one embryo grows into a baby.
Success rate of IVF is low
Emotionally and physically stressful

69
Q

Why are some people against IVF?

A

The process results in unused embryos which are eventually destroyed. Some people think this is unethical because theyre potential human life.

Genetic testing raises ethical issues because it could lead to selection of preferred characteristics such as gender or eye colour.

70
Q

Whats the function of adrenaline?

A

Adrenaline is a hormone released by adrenal glands.

Released in response to stressful or scary stimulations.
Your brain detects fear or stress and sends nervous impulses to adrenal glands which respond by producing adrenaline.

Increases supply of oxygen and glucose to cells in brain and muscles. Eg increases heart rate

71
Q

How does your body control levels of hormones?

A

Negative feedback

72
Q

What is thyroxine?

A

A hormone released by thyroid gland.

Regulates metabolic rate. Also important for protein synthesis.

Released in response to thyroid stimulating hormone (TSH) from pituitary gland.

Negative feedback keeps thyroxine in the blood at the right level.
If thyroxine too high, release of TSH is inhibited and opposite if thyroxine too low

73
Q

What is auxin?

A

Auxin is a plant hormone which controls growth near the tips of shoots and roots.

Controls the growth of a plant in response to light (phototropism) and gravity(geotropism)

Extra auxin promotes growth in shoot but inhibits growth in root.

Produced in tips and moves backwards to stimulate cell enlargement.

If tip is removed, no auxin is available and shoot may stop growing.

74
Q

Why does a shoot grow towards light and gravity?

A

When shoot tip is exposed to light, more auxin accumulates on the side thats in the shade which makes cells grow faster on shaded side so shoot bends towards light.

When a shoot is growing sideways, gravity produces an unequal distribution of auxin in tip, with more on the lower side.
This causes lower side to grow faster, bending the shoot upwards.

A root growing sideways will also have more auxin on its lower side.
In a root extra auxin inhibits growth so cells on the top will grow faster, making it bend downwards

75
Q

What are commercial uses of auxin?

A

Killing weeds - Auxin disrupts their growth patterns which soon kills them

Growing from cuttings with rooting powder - rooting power with auxins makes cuttings grow roots and start growing as a new plant. Allows growers to produce clones of really good plants.

Growing cells in tissue culture - auxins added to growth medium to stimulate the cells to divide to form both roots and shoots

76
Q

What are commercial uses of gibberellin?

A

Hormone that stimulates seed germination, stem growth and flowering.

Controlling dormancy - Make seeds germinate at times of years that they wouldnt normally

Inducing flowering - Let plants flower without certain environmental conditions needed.

Growing larger fruit

77
Q

How is ethene used commercially?

A

A gas produced by aging parts of a plant. Influences growth of the plant controlling cell division. Stimulates enzymes that cause fruit to ripen.

Speed up ripening of fruits. Whilst on the plant or even when being transported to a shop.

Allows fruit to be picked unripe.

Ripening can be delayed whilst in storage

Josh Lee Biology (6 decks)

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