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Biology > Homeostasis. > Flashcards

Homeostasis. Flashcards

1
Q

What is homeostasis?

A

The regulation of the internal conditions of a cell or organism in response to internal and external changes.

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2
Q

Why is homeostasis important?

A

Because it keeps conditions constant for enzyme action and cell functions.

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3
Q

What does homeostasis control?

A

It controls:
-Blood glucose concentration
-body temperature
-water and ion levels.

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4
Q

What do all control systems include?

A

-Receptors which detect stimuli (changes in the environment)
-Coordination centres eg the brain, spinal cord and pancreas
-Effectors that bring about responses that restore optimum levels.

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5
Q

What does the thermoregulatory center in the brain do?

A

-Monitors and controls body temperature.
-Has receptors that monitor the temperature of blood flowing through the brain
-Receives impulses from temperature receptors in the skin.

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6
Q

What is vasodilation?

A

When the body temperature is too high blood vessels widen, directing more blood to the surface of the skin.

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7
Q

What is vasoconstriction?

A

If the body temperature is too low blood vessels narrow, directing blood away from the surface of the skin.

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8
Q

What are the steps of unconscious reactions?

A

It does not involve the conscious part of the brain.
1) The pain stimulus is detected by receptors.
2) Impulses pass along a sensory neurone to the central nervous system.
3) An impulse then passes through a relay neurone.
4)A motor neurone carries an impulse to the effector.
5) The effector (usually a muscle) responds to withdraw a limb from the pain

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9
Q

(RP) Investigating the effect of a factor on human reaction time.

A

1) Experimenter holds a meter ruler from the end.
2) The subject has their thumb and finger apart,
3) The experimenter lets go of the ruler and the subject has to catch it.
4) Wherever the subject’s thumb is, is where you measure the result from.
5) Repeat the experiment on subjects that have drunk coffee or cola etc and use a conversion table to change it into time (s).

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10
Q

Variables for the RP Investigating the effect of a factor on human reaction time.

A

IV= Whether the subject has had caffeine or not.
DV= Distance the ruler travels.
CV= Age, gender and mass of the subjects.

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11
Q

What is the endocrine system made up of?

A

It is made up of glands that secrete hormones directly into the bloodstream.

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12
Q

What are hormones?

A

They are chemical messengers that are carried in the blood to a target organ where they produce an effect.

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13
Q

What are the differences between the effects of the central nervous system and hormones?

A

The effects of hormones are slower and act for longer.

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14
Q

What does the pituitary gland do?

A

Located in the brain and is a ‘master gland’. It secretes several hormones in response to body conditions.

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15
Q

Adrenaline.

A

-Is produced by the adrenal glands in times of fear or stress.
-Increases the heart rate, boosting the delivery of oxygen and glucose to the brain and muscles.
-Prepares body for flight or fight.

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16
Q

Thyroxine.

A

-Is produced by the thyroid gland.
-Increase the metabolic rate.
-Controls growth and development in young animals.
-Is controlled by negative feedback.

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17
Q

What happens if blood concentration is too high?

A

-The pancreas releases more of the hormone insulin.
-Insulin causes glucose to move from the blood into the cells.
-In liver and muscle cells, excess glucose is converted to glycogen for storage.

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18
Q

What happens if blood concentration is too low?

A

-The pancreas releases glucagon.
-Glucagon stimulates glycogen to be converted into glucose and released into the blood.
-This is an example of negative feedback.

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19
Q

Type 1 diabetes is a disorder that:

A

-Is caused by the pancreas failing to produce sufficient insulin.
-Results in uncontrolled high blood glucose levels.
-Is normally treated with insulin injections.

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20
Q

Type 2 diabetes is a disorder that:

A

-Is caused by the body cells no longer responding to insulin.
-Has obesity as a risk factor.
-Is treated with a carbohydrate-controlled diet and regular exercise.

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21
Q

What is deamination?

A

Digestion of proteins from food, results in excess amino acids.
In the liver, these excess amino acids are converted to ammonia in a process called deamination.

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22
Q

What happens to the ammonia produced in the liver?

A

It is toxic so it is immediately converted to urea and sent to the kidneys for excretion.

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23
Q

How does the kidneys produce urine?

A

1) Filtering the blood.
2) Selective reabsorption of useful substances, such as glucose, some ions and water.
3) This leaves urea and excess water and ions to form urine
These processes take place in millions of small tubes in the kidneys called tubules.

24
Q

What does the hormone ADH control?

A

The water level in the body.

25
Q

Why is ADH released and where from?

A

It is released by the pituitary gland when the blood is too concentrated.
It passes, in the blood, to the kidney tubules where it causes more water to be reabsorbed back into the blood.

26
Q

How can kidney failure be treated?

A

People who suffer from kidney failure may be treated by organ transplant or kidney dialysis.

27
Q

What does a dialysis machine do?

A

It takes over the role of kidneys, it is used to remove waste products from the blood, three times a week.

28
Q

What is oestrogen?

A

The female sex hormone and is from
the ovaries.

29
Q

What is ovulation?

A

When eggs begin to mature and be released.

30
Q

What is testosterone?

A

It is the main male sex hormone. It is produced by the testes and simulates sperm production.

31
Q

What are the 4 hormones involved in control of the menstrual cycle?

A

Follicle-stimulating hormone (FSH)-Causes eggs to mature stimulates ovaries to produce oestrogen.
Oestrogen- secreted by the ovaries. Function- Prevents FSH release. Stimulates LH release. Makes the lining of the uterus.
Luteinising hormone (LH)- Stimulates the release of the egg from the ovary (ovulation).
Progesterone- Secreted by the empty follicle in the ovaries.
Maintains the lining of the uterus during the second half of the cycle.
Prevents both FSH and LH release.

32
Q

What are the hormonal methods of contraception?

A

-Oral contraceptives(the combined pill) that contain oestrogen and progesterone which inhibit FSH production so that no eggs are released.
-An injection, implant or skin patch of slow-release progesterone to stop the release of eggs for a number of months or years.

33
Q

What are the non-hormonal methods of contraception?

A

-Barrier methods such as condoms, that prevent the sperm from reaching an egg.
-Intrauterine devices, which prevent embryos from implanting in the uterus.
-Spermicidal creams, which kill or disable sperm.

34
Q

What is in a fertility drug and why is it given?

A

Doctors may give FSH and LH in a drug to a woman if her own level of FSH is too low to stimulate eggs to mature.

35
Q

What does the in vitro fertilisation (IVF) treatment involve?

A

-Giving a woman FSH and LH to stimulate the growth of many eggs.
-Collecting the eggs from the woman.
-Fertilising the eggs with sperm from the father in the laboratory.
-Inserting one or two embryos into the woman’s uterus (womb).
This gives the woman a chance to have a baby.

36
Q

What are the disadvantages of IVF?

A

-It is emotionally and physically stressful.
-The success rates are not high.
-It can lead to multiple births, which are a risk to both the babies and the mother.

37
Q

What are the 3 main regions of the brain and what are their functions?

A

Cerebral cortex- Responsible for consciousness, intelligence, memory and language.
Cerebellum- Coordinates movement and balance.
Medulla- Controls automatic reactions such as heartbeat and breathing.

38
Q

How have neuroscientists been able to map the regions of the brain to particular functions?

A

-Studying patients with brain damage.
-Electrically stimulating different parts of the brain.
-Using MRI scanning techniques.

39
Q

Parts of the eye and their functions.

A

Retina-Contains receptor cells that are sensitive to the brightness and colour of light.
Optic nerve- Carries impulses from the retina to the brain.
Sclera-Forms a tough outer layer, with a transparent region at the front called the cornea.
Iris- Controls the size of the pupil and the amount of light reaching the retina.
-Ciliary muscles and suspensory ligaments-Can change the shape of the lens to focus light onto the retina.

40
Q

What is accommodation?

A

Accommodation is the process of changing the shape of the lens to focus on near or distant objects.

41
Q

What happens to the eye when focusing on a near object?

A

-Ciliary muscles contract.
-Suspensory ligaments loosen.
-Lens becomes thicker and refracts light rays strongly.

42
Q

What happens to the eye when focusing on a distant object?

A

-Ciliary muscles relax.
-Suspensory ligaments are pulled tight.
-Lens is pulled thin and only slightly refracts light rays.

43
Q

What is myopia and hyperopia and how is it treated?

A

Myopia (concave lens) is short-sightedness and hyperopia(convex lens)is long-sightedness. It is treated by spectacle lenses which refract the light rays so that they focus on the retina.

44
Q

What is tropism?

A

When part of a plant responds by growing in a particular direction.

45
Q

How does gravity affect the shoots and roots?

A

Shoots- Away= Negatively gravitropic (geotropic).
Roots- Towards= Positively gravitropic (geotropic).

46
Q

How does light affect shoots and roots?

A

Shoots-Towards= Positively phototropic.
Roots-away= Negatively phototropic.

47
Q

What is the name of the plant hormone that tropism is controlled by?

A

Auxin.

48
Q

What are the steps that are involved in the response to light?

A

1) More light reaches one side of the shoot.
2) More auxin is sent down the shaded side of the shoot.
3) This results in cells on the shaded side elongating more.
4) The shoot, therefore,grows towards the light

49
Q

How does auxin work in the roots?

A

It moves to the bottom of the root and causes less elongation so the root grows downwards.

50
Q

What are gibberellins?

A

They are another group of plant hormones and are important in initiating seed germination (growth).

51
Q

(RP) Investigating the effect of light on the growth of newly germinated shoots.

A

1) Take a number a number of small boxes and make a hole on one side.
2) Put soil in and plant 10 cress seeds each.
3) Put a lid on each container.
4) Put them in even lighting with holes pointing in different directions.
5) Water the soil and leave for several days.

52
Q

What are the variables of the RP Investigating the effect of light on the growth of newly germinated shoots?

A

IV= Position of the hole.
DV= Direction in which the seedlings grow.
CV= Type of seeds, soil type and volume of water.

53
Q

What is ethene and what does it do?

A

It is a gas and also a plant hormone. It controls cell division and ripening of fruits.

54
Q

What is auxin used for?

A

-Weed killers because they make weeds grow so rapidly that they use up their food reserves and die.
-Rooting powders because they make cuttings and produce roots when planted.
-Promoting growth in tissue culture.

55
Q

What is ethene used for?

A

Used in the food industry to control the ripening of fruit during storage and transport.

56
Q

What is gibberellin used for?

A

-Make seeds germinate.
-Increase fruit size.
-Promote flowering so that plants flower when there is the most demand.

Biology (8 decks)

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