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GCSE AQA biology > Topic 5- Homeostasis and response > Flashcards

Topic 5- Homeostasis and response Flashcards

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1
Q

Sexual reproduction:

A

Invloves the joining of male and female gamtes, each containing genetic information from the mother or father.
* Sperm and egg cells in animals
* Pollen and egg cells in flowering plants

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2
Q

Meiosis:

A
  • The cell makes copies of it’s chromosmes, so it has double the amount of genetic information
  • The cell divides into two, both the cells have half the amount of chromosmes
  • The cells divide again, producing four cells, each with a quarter amount of chromosmes
  • These cells are called gametes and they are all genetically different from each other. This is because the chromosomes are shuffled during the process, resulting in random chromosomes ending up in each of the four cells.
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3
Q

Homeostasis:

A
  • An organism’s ability to regualte it’s internal conditions, even when external conditions change.
  • What needs to be regualted?
    1. Blood glucose concentration
    2. Body temperature
    3. Water levels
  • Homeostasis maintains optimal conditions for enyme action and cell functions.
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4
Q

Automatic control systems:

A
  • May invlove nervous responses or chemical responses
  • All control systems include:
    - Recpetors (cells that dectect a stimulus)
    - Coordination centres (such as the brain, spinal cord and pancreas) that recieve and process information from receptors
    - Effectors, muscles or glands which bring about responses which restore optimum levels.
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5
Q

The human nervous system:

A

Enables humans to react to their surroundings and co-ordinate their behaviour.
1. Information from receptors passes along receptors (cells)
2. As electrical impulses to the central nervous system (CNS).
3. The CNS coordinates a response- which may be muscles contracting or glands secreting hormones.

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6
Q

What is the central nervous system (CNS)?

A

The brain and spinal cord.

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7
Q

What is the PNS?

A

All other nerves.

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8
Q

Reflex:

A
  • In a reflex arc, the signal passes by much quicker
  • They are automatic and rapid- do not involve the concious part of the brain.
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9
Q

Structures in a reflex arc:

A

Stimulus→receptor→coordinator→effector→response

This is quicker than normal responses as you do not have to think about the response.

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10
Q

Synapse:

A

A gap between two neurones that trigger chemicals to be released.

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11
Q

The brain- cerebral cortex:

A

Resonsible for higher level functions:
* Memory
* speech
* problem solving

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12
Q

The brain - cerebellum:

A

Responsible for motor skills:
* Movement
* Balance
* Coordination

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13
Q

The brain- medulla:

A

Responsible for unconcious actions:
* Heart and breathing rate
* Signals to adrenal glands to release adrelanine

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14
Q

Electrically stimulating different parts of the brain:

A
  • Can be stimulated electically by pushing an electrode intto the tissue and giving it a small zap of electricity. By observing the stimulation, scientists get a better idea of what those parts of the brain do.
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15
Q

MRI scans:

A
  • Allow doctors to see brain activity without surgery.
  • Issues with the brain are impossible/ difficult to treat safely.
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16
Q

Accomodation:

A

The eye’s ability to focus on near or distant objects.

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17
Q

Accomodation- near objects:

A
  • Ciliary muscles contract
  • So they have a smaller diameter
  • Suspensory ligaments slacken
  • Lens becomes fatter
  • Light is refracted more
  • Light rays are focused onto retina
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18
Q

Accomodation- distant objects:

A
  • Ciliary muscles relax
  • So they have a bigger diameter
  • Suspensory ligaments tighten
  • Lens becomes thin
  • Light is refracted by a smaller amount
  • Light rays are focused onto retina
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19
Q

Retina cells:

A

Consist of only rod and cone cells, which respond to light.
* Rods only detect light intensity
* 3 different types of cones; that are sensitive to red, blue or green wavelengths of light which provide colour information.
* These signals travel to the brain via the optical nerve

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20
Q

HYPEROPIA (long sightedeness):

A

Long-sighted people are unable to focus on near objects.
* The eyeball is too short, so light focuses behind the retina.
* Use glasses with convex lenses so light rays focus on the retina.

21
Q

MYOPIA (short-sightedness):

A

Short-sighted people are unable to focus on distant objects.
* Eyeball is too long, so light focuses infront of the retina.
* Use glasses with concave lenses so that light rays focus on the retina.

22
Q

Body temperature:

A
  • Controlled by the thermoregulatory centre in the brain.
  • Thermoregulatory centre contains receptors sensetive to the temperaure of the blood.
  • Nervous impulses are sent to effectors
23
Q

Body temperature is too high:

A
  • Blood vessels dilate
  • Sweat is produced from the sweat glands
  • Both these mechanisms transfer energy from skin to environment.
24
Q

Blood temperature is too low:

A
  • Blood vessels constrict
  • Sweating stops
  • Skeletal muscles contract (shiver)
  • Hair stands on end to trap air- layer of insulation
25
Q

Endocrine system:

A

System of glands which secrete hormones to send signals to effectors, transported via the blood.
* Slower than the nervous system, but act for longer.

26
Q

Pituitary gland:

A
  • In the brain
  • Is the ‘Master gland’
  • Send signals to other glands to stimulate other hormones to be released.
27
Q

Thyroid:

A

Controls growth and metabolism

28
Q

Control of blood glucose concentration:

A

Blood glucose concentration is monitored and controlled by pancreas.

29
Q

What happens when blood glucose concentration is too high?

A
  • Pancreas produces the hormone insulin
  • This causes glucose to move from the blood into cells
  • In liver and muscle cells, excess glucose is converted into glycogen for storage.
30
Q

What happens when blood glucose concentration os too low?

A
  • The pancreas produces the hormone glucagon that causes glycogen to be converted into glucose and released into the blood.
    This is an example of NEGATIVE FEEDBACK.
31
Q

Type 1 diabetes:

A
  • Pancreas fails to produce sufficient insulin
  • Person has high blood glucose levels
    Person is treated with insulin injections.
32
Q

Type 2 diabetes:

A
  • The body cells no longer respond to insulin prduced by the pancreas.
  • Risk factor- obesity
    Common treatments: carbohydrate controlled diet, exercise regime.
33
Q

Maintaining water and nitrogen balance in the body:

A
  • Water leaves the body via the lungs during exhalation
  • Water, ions and urea are lost from the skin in sweat.
  • There is no control over water, ion aor urea lost by skin or lungs.
  • Excess water, ions and urea are removed via the kidneys in the urine
  • If body cells lose or gain too much water by osmosis, they do not function efficiently.
34
Q

Too much water:

A
  • Water moves in by osmosis
  • Cell becomes turgid, could burst
  • Cell cannot function efficiently
35
Q

Too little water:

A
  • Water moves out by osmosis
  • Cell becomes flaccid
  • Cell cannot funnction efficiently
36
Q

Urea:

A

Urea is asubstance removed from the body
* Digestion of proteins results in excess amino acids that need to be excreted safely.
* In the liver, the amino acids are deaminated to form ammonia.
* Ammonia is toxic- so it’s immediately converted to urea for safe excretion.

37
Q

Kidneys:

A

Kidneys produce urine (water mixed with urea) by filtration of blood and selective reabsorption of useful substances, such as glucose, ions and water.

38
Q

ADH:

A
  • Water level in the body is controlled by ADH, which acts on the kidney tubules.
  • ADH is released by the pituitary gland when the blood is too concentrated
  • This causes more water to be reabsorbed bak into the blood from the kidney tubules.
    This is controlled by negative feedback.
39
Q

Kidney failure:

A
  • Organ transplant
  • Kidney dialysis- blood is filtered by a machine. If this does not happen, the build up of urea/ ammonia will be poisonous.
40
Q

Hormones in human reproduction:

A
  • Oestrogen is the main female reproductive hormone- produced in the ovary. At puberty, eggs begin to mature and one is released every 28 days. This is called ovulation.
  • Testosterone is the main male reproductive hormone- produced by testes and stimulates sperm production.
41
Q

Menstrual cycle:

A
  • FSH- causes maturation of an egg in the ovary
  • LH- stimulates the release of an egg
  • Oestrogen & progesterone- involved in maintaining the uterus lining
42
Q

Contraception:

A
  • Oral contraceptives- contain hormones to inhibit FSH production
  • Barrier methods e.g. condoms and diaphragms- prevent sperm from reaching egg
  • Spermicidal agents- kill or disabke sperm
43
Q

The use of hormones to treat infertility:

A

IVF treatment:
* Invloves giving a mother FSH and LH to stimulate the mauration of an egg
* Eggs are collected from mother and fertilised by sperm from father in the lab.
* Fertilised aggs develop into embryos
* When they are tiny balls of cells, one or two embryos are inserted into the mother’s uterus (womb).

44
Q

Adrenaline:

A
  • Produced by adrenal gland in times of fear and stress.
  • It increases the heart rate and boosts the delivery of oxygen and glucose to brain and muscles
  • This prepares the body for a ‘fight or flight situation’.
45
Q

Thyroxine:

A
  • Produced by thyroid gland
  • Stimulates metabolic rate
  • Plays an important role in growth and development
46
Q

Gibbirelanis (palnt hormone):

A

Important in initiating seed germination

47
Q

Ethene (plant hormone):

A

Controls cell division and ripening of fruits.

48
Q

What are auxins used as?

A
  • Weed killers
  • Rooting powders
  • Promoting growth in tissue culture
49
Q

What is gibberellins used to do?

A
  • End seed germination
  • Promote flowering
  • Increases fruit size

GCSE AQA biology (5 decks)

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