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biology paper 2 > topic 1 > Flashcards

topic 1 Flashcards

1
Q

What is homeostasis?

A

Homeostasis is the maintenance of a constant internal environment in order to
maintain optimum conditions for enzyme and cellular function.

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2
Q

Give examples of conditions maintained
by homeostasis in the body

A

● Blood glucose concentration
● Body temperature
● Water levels

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3
Q

What two types of responses are used in body control systems?

A

Nervous and chemical

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4
Q

What three components do all control systems have?

A

● Receptors
● Coordination centres
● Effectors

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5
Q

What is the function of a receptor?

A

Receptors detect changes in the
environment (stimuli).

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6
Q

What is the function of a coordination centre?

A

obtain and process information from receptors.

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7
Q

What is the function of an effector?

A

Effectors (muscles or glands) bring about responses to stimuli.

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8
Q

What is the function of the nervous system?

A

allows the body to
react to its surroundings and coordinate an
appropriate response.

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9
Q

How does a stimulus lead to a response being carried
out by the body?

A
  • Stimulus is converted into an electrical impulse by the
    receptors.
    ● The electrical impulse passes along sensory neurones to
    the central nervous system (CNS).
    ● The CNS coordinates an appropriate response and an
    electrical impulse is sent along motor neurones to the
    effector, which carries out the response.
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10
Q

What sequence of events describes how
the nervous system works?

A

stimulus
receptor
sensory neurone
relay/CNS
motor neurone
effector
response

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11
Q

What is a reflex action?

A

automatic and rapid
response which does not involve any
conscious input from the brain

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12
Q

Why are reflex actions important?

A

aid survival by preventing
harm to the body.

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13
Q

what is a synapse

A

gap between any neurone

a neurotransmitter diffuses across and produces an electrical impulse in the next neurone

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14
Q

Describe how a reflex action occurs via a reflex arc

A

● The stimulus is detected by a receptor.

● An electrical impulse passes along a sensory neurone to the spinal cord
(part of the CNS).

● At a synapse between a sensory neurone and a relay neurone, a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neurone.

● The same process occurs at a synapse between a relay neurone and a motor neurone.

● At the effector, an appropriate response is carried out

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15
Q

What is the function of the cerebral cortex?

A

controls consciousness,
intelligence, memory and
language.

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16
Q

What is the function of the cerebellum?

A

controls muscular
coordination

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17
Q

What is the function of the medulla?

A

controls
unconscious
activities

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18
Q

Why is the investigation and treatment of the
brain difficult?-

A

● complex and delicate organ.
● easily damaged and destroyed.
● Certain membranes prevent drugs from reaching
the brain.
● The exact function of each part of the brain is not
known

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19
Q

What methods are used by scientists to determine
brain function?

A

● Studying patients with brain damage
● Electrical stimulation of the brain
● MRI scans

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20
Q

What stimuli are the receptors of the eye sensitive to?

A

Light intensity
colour

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21
Q

what is the iris

A

controls light entry

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22
Q

what is the cornea

A

refracts light

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23
Q

what is the pupil

A

allows light to pass through and enter the eye

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24
Q

what is the lens

A

refracts light to focus on the retina

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25
Q

what is the sclera

A

white part

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26
Q

What are the two main functions of structures
found within the eye?

A

● Focusing on near or distant objects -
accommodation.
● Adaptation to dim light

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27
Q

Describe the structure of the retina

A

The retina is a light-sensitive
layer found at the back of the
eye.

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28
Q

Describe the function of the retina

A

Light stimulates the retinal cells,
resulting in impulses being sent
to the brain.

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29
Q

what are cilliary muscles

A

adjust the shape of the lens to alter the refraction of light

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30
Q

what are suspensory ligaments

A

slacken or stretch to adjust the thickness of lens

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31
Q

eye adjust to focus on near object

A

cilliary muscles contract
suspensory ligaments loosen
lens is thicker
refracts light more

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32
Q

eye adjust to focus on
distant object

A

cilliary muscles loosen
suspensory ligaments pull tight
lens is thinner
refracts light slightly

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33
Q

Describe how the iris alters the size of the pupil in dim light

A

circular muscles relax and radial muscles contract - makes pupil larger so more light can
enter the eye.

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34
Q

Describe how the iris alters the size of the pupil in bright light

A

circular muscles contract and radial muscles relax - makes pupil smaller to avoid retinal
damage.

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35
Q

What is accommodation?

A

the alteration of the
lens’ shape in order to focus on near or distant objects.

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36
Q

What is myopia?

A

short sightedness
lens of the eye is too curved. As a result, light is focused in front of the retina

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37
Q

How can myopia be treated?

A

glasses with a concave lense, which spreads out light rays so they can be focused on the retina.

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38
Q

What is hyperopia?

A

the lens of the eye is too flat. As a result, light is focused behind the retina

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39
Q

How can hyperopia be treated?

A

glasses with a convex lense, which brings the light rays together so they can be focused on the retina

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40
Q

What are the two types of contact lenses?

A

● Hard - rigid material, last a long time, must be kept
sterile.
● Soft - flexible material, last for a shorter time, more
comfortable.

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41
Q

risks of replacement lenses

A

retinal damage, cataracts
and infections.

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42
Q

What is laser eye surgery?

A

lasers either reduce thickness (myopia)
alter curvature (hyperopia)

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43
Q

Where is body temperature controlled in the
body?

A

thermoregulatory centre in the hypothalamus
of the brain

44
Q

when the temp is too high

A

● Vasodilation - blood vessels near the surface
of the skin dilate - more heat is radiated away.
● Sweating - evaporation of water takes away
heat energy from the surface of the skin.

45
Q

How is temperature monitored by the body?

A

● Thermoregulatory centre has receptors
sensitive to blood temperature.
● Skin has receptors sensitive to skin
temperature - sends impulses to
thermoregulatory centre.

46
Q

What physiological changes occur when the
body temperature is too low?

A

Vasoconstriction - blood vessels near the surface
of the skin constrict - less heat radiated away.
● Shivering - respiration allows muscles to contract.
It is an exothermic process, so heat energy is
released.
● Sweating stops.

47
Q

what is the endocrine system

A

made from glands
body’s coordination system
which involves hormones

48
Q

What is a hormone?

A

A hormone is a chemical messenger
secreted by a gland. It travels in the blood to
a target organ, where it causes a response.

49
Q

what is the pituitary gland

A

master gland
secretes several hormones
sometimes they act upon other glands to release hormones

50
Q

How does the pancreas respond when blood
glucose levels are too high?

A

secretes insulin
causes glucose to move from blood into the cells
in the liver excess glucose is converted to glycogen for storage

51
Q

How does the pancreas respond when blood
glucose levels are too low?

A

secretes the hormone
glucagon. Glucagon binds to liver cells, causing glycogen to be converted into glucose and released into the blood.

52
Q

what is type 1 diabeties

A

pancreas doesnt produce enough insulin
insulin injections

53
Q

what is type 2 diabeties and their risk factors

A

body cells to stop responding to insulin
obsitity

54
Q

How can Type 1 diabetes be treated?

A

● Insulin injections before meals - allows
glucose to be converted into glycogen.
● Limiting carbohydrate intake.

55
Q

How can Type 2 diabetes be treated?

A

● Following a carefully-controlled diet
● Doing regular exercise
● Losing weight
● Use of drugs which increase insulin production and effectiveness

56
Q

How is blood glucose concentration controlled using
a negative feedback loop?

A

● When the blood glucose concentration rises or falls
below the optimum, a hormone is secreted by the
pancreas.
● The action of either hormone (insulin or glucagon)
helps bring back the concentration to the correct
level

57
Q

In what ways is water lost from the body?

A

● During exhalation via the lungs
● Sweating
● Urine (some reabsorbed in the kidney)

58
Q

what happens if cells gain/loose too much water

A

do not function effectively

59
Q

In what ways are ions lost from the body?

A

● Sweating
● Urine (some reabsorbed in the kidney)

60
Q

How are excess amino acids excreted from the
body?

A

● Excess amino acids are deaminated in the liver to
form ammonia.
● Ammonia is toxic, therefore it is converted into urea
● Urea is excreted from the body via sweat and urine.

61
Q

kidney fuction

A

produce urine by filtration
urea is not reabsorbed
glucose ions and water are reabsorbed

62
Q

what is in dyalisis fluid

A

glucose concentration similar to blood level
similar ion level
no urea

63
Q

not enough water in blood

A

increase ADH
increases the permeability of tubules
more water reabsorbed
concentrated urine

64
Q

too much water in blood

A

decrease ADH
decreases the permeability of tubules
less water reabsorbed
dilute urine

65
Q

Why is kidney failure dangerous?

A

● A build-up of toxic molecules (eg. urea) in the
body.
● An uncontrolled ion and water balance and cells
being damaged as a result of osmosis.

66
Q

What are the two main ways of treating kidney failure?

A

● Dialysis
● Transplant

67
Q

What is kidney dialysis?

A

use of a specialist machine
to carry out the function of kidneys

68
Q

What is the main male reproductive hormone?

A

testosterone, which is produced by the testes and controls sperm production.

69
Q

What is the main female reproductive hormone?

A

oestrogen, which is produced by the ovaries
and is involved in the menstrual cycle.

70
Q

What is the menstrual cycle?

A

monthly cycle of
physiological changes that occur in females,
involving the shedding of the uterus lining
(menstruation) and ovulation.

71
Q

Describe the events of the menstrual cycle

A

● Uterus lining thickens and eggs begin to mature in the
ovaries.
● An egg is released from one of the ovaries (ovulation)
- uterus lining remains thick.
● If the egg is fertilised, pregnancy may occur. If not,
both the egg and the uterus lining are shed during
menstruation.

72
Q

what is FSH

A

pituitary gland
matures the egg
simulates oestrogen release

73
Q

LH

A

stimulates the release of the egg

74
Q

What is the role of oestrogen in the menstrual cycle?

A

it causes
the regrowth of the uterus lining.
It triggers the production of LH and restricts the
release of more FSH.

75
Q

What is the role of progesterone

A

It sustains the uterus lining and
inhibits FSH and LH.

76
Q

what is ovulation

A

the realease of a mature eggh

77
Q

how often dos ovulation occur

A

28 days

78
Q

what are the four main hormones

A

● Oestrogen
● Progesterone
● Follicle stimulating hormone (FSH)
● Luteinising hormone (LH)

79
Q

what is contreception

A

any method of prevneting pregnacy

80
Q

What are the two types of oral contraceptives?

A

● Combined contraceptive pill (contains
oestrogen and progesterone).
● Mini pill (contains only progesterone).

81
Q

How does the contraceptive pill prevent
pregnancy?

A

● Inhibits FSH - eggs do not mature.
● Prevents the development of the uterus lining -eggs cannot implant.
● Increases the thickness of cervical mucus - immobilises sperm cells.

82
Q

What is the contraceptive patch?

A

● Contains both oestrogen and
progesterone.
● It is a patch that is placed onto the skin for 7 days at a time.

83
Q

What is the contraceptive implant?

A

A small rod inserted under the skin which continuously releases the hormone progesterone - lasts for 3 years

84
Q

what is the contraceptive injection

A

injection containing progesterone

85
Q

what is an IUD

A

small copper-containing device inserted into the uterus, which prevents the implantation of embryos.

86
Q

what is spermicide

A

kills/ imboblises serm
not very effective

87
Q

How do fertility drugs increase the chance of
pregnancy?

A

Many fertility drugs contain FSH - which
stimulates oestrogen production and the
maturation of eggs in the ovary. They also
contain LH which triggers ovulation.

88
Q

what is IVF

A

mother is given FSH/LH to simulate the maturation of the egg
eggs are collected and fertilized by sperm in a lab
which develop into embryos
when a tiny ball of cells they are separated 1 or 2 in the womb the rest are frozen

89
Q

advantages of IVF

A

● Allows infertile couples to have children
● Can store a woman’s eggs for later

90
Q

disadvantages of IVF

A

● It can be a very expensive process.
● It has a low success rate - especially for older couples.
● Increases chance of multiple pregnancies - dangerous for mother and babies.
emotionally and physically stressful

91
Q

What is negative feedback?

A

a type of control where
the body responds to an increase or
decrease in a factor by returning it to the optimum level.

92
Q

where is thryroxide produced

A

in the thyroid gland

93
Q

role of thyroxine

A

stimulates the basal metabolic rate
increase metabolism
so more fat is used up and more energy required ( weight loss)
important in growth and development

94
Q

How is the release of thyroxine controlled by negative
feedback?

A

● Levels of blood thyroxine falls - detected by
receptors in the brain.
● Pituitary gland releases more TSH.
● More thyroxine produced and released by the
thyroid gland.
● Blood thyroxine level returns to normal.

95
Q

what is adrenaline

A

produced in the adrenal glands
stimulates heart rate
boosts oxygen and glucose to the brain and muscles
for flight or fight

96
Q

What are the effects of adrenaline?

A

● Dilation of pupils.
● Increased mental awareness.
● Blood diverted away from digestive system to
muscles

97
Q

What is a tropism?

A

A tropism is the response of a plant to a
specific stimulus

98
Q

What is phototropism?

A

Phototropism is the response of a plant’s
shoot or root to light

99
Q

What is geotropism?

A

Gravitropism is the response of a plant’s
shoot or root to gravity.

100
Q

what is auxin

A

a plant growth hormone
responds to light and gravity
unequal distribution causes an unequal growth rate in plants

101
Q

How do plant shoots show positive
phototropism?

A

● One side of the shoot is in the light, causing auxin
to move to the shaded side.
● At the shaded side, the cells are stimulated to
grow - the shoot bends towards the light.
● As a result, photosynthesis can occur at a faster rate.

102
Q

How do plant shoots show negative
gravitropism?

A

● In a horizontal shoot, auxin accumulates in the
lower side due to gravity.
● Cells on the lower side of shoot grow more, causing
the shoot to bend away from the direction of gravity.
● As a result, more light is usually available for photosynthesis.

103
Q

what are gibberellins

A

initiate seed germination
- termination of seed dormancy
- promotion pf flowering
- increase fruit size

104
Q

what is ethene

A

controls cell division ripening of fruits

105
Q

uses of auxins

A

weedkillers - rapid growth which leads to death
rooting powder - grow quicker

biology paper 2 (3 decks)

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