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Homeostasis Flashcards

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1
Q

What is homeostasis ?

A

Maintaining a constant internal environment to maintain optimum conditions despite changing conditions

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2
Q

What do receptor cells do?

A

Detect stimuli (changes in the environment) like eyes or skin

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3
Q

What are co-ordination centres?

A

Brain, spinal cord, pancreas. They receive and process information from receptors to coordinate a response

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4
Q

What are effectors?

A

Like skeletal muscles and glands which bring responses to restore optimum conditions

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5
Q

What do sensory neurones do?

A

Carry information as electrical impulses from your receptor cells to the central nervous system (coordinator)

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6
Q

What is the CNS made of?

A

The brain and the spinal cord

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7
Q

What does the CNS do?

A

Coordinates process information and send impulses along motor neurones

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8
Q

What do motor neurones do?

A

Carry information from coordinator to effector organs to bring about a response

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9
Q

Name the two types of effectors and state what they do

A

Muscles contract
Glands release hormones

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10
Q

What are reflex actions?

A

Rapid automatic responses to a stimulus which don’t involve the brain and are often protective

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11
Q

What is the pathway of a reflex arc?

A

SRSRME- stimulus, receptor, sensory, relay, motors, effector

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12
Q

Many general anaesthetics inhibit the release of signalling chemicals called neurotransmitters across some synapses. Explain the impact of this on the nerve impulse

A

A nerve/electrical impulse arrives at the end of the neurone; [1 mark]
(But), anaesthetic stops/inhibits the release of chemicals/neurotransmitters; [1 mark]
(So) no/fewer chemicals/neurotransmitters diffuse across / crosses the gap between neurones; [1 mark]
No / a reduced impulse is triggered/sent from the next neurone; [1 mark]
(Thus) stopping/disrupting the transmission of nerve/electrical impulse;

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13
Q

Reflexes in the eye cause a blink if something quickly comes towards them. Explain why such reflexes are important

A

Reflexes are involuntary
The brain is not involved in the reflex action
They help minimise damaged to the body

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14
Q

Function of the cerebral cortex

A

Intelligence, memory, consciousness and personality

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15
Q

Cerebellum

A

Under cerebral cortex and responsible for balance, muscle coordination and movement

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16
Q

Medulla

A

Unconscious activities like heart rate and breathing

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17
Q

Hypothalamus

A

Controls body temperature

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18
Q

Pituitary gland

A

Master gland send signals to other glands to produce hormones

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19
Q

What is the function of the cornea?

A

Transparent lens that refracts light as it enters the eye

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20
Q

Function of Iris

A

Controls how much light enters the pupil

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21
Q

Function of the lens

A

Transparent disc that changes shape to focus light on the retina . Further refracts light

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22
Q

Function of the optic nerve

A

Sensory neurone that carries impulses between the eye and the brain

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23
Q

Function of the sclera

A

White tough outer layer coat to protect eye from injury

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24
Q

Function of pupil

A

Hole that allows light to enter the eye

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25
Q

Function of retina

A

Light receptor cells (rods- light intensity) and cones (colour) and are sensitive to light

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26
Q

What happens to the pupil in dim light?

A

It dilates to allow as much light as possible into the eye

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27
Q

What happens to the pupil in bright light?

A

The pupil constricts in order to prevent too much light from entering the eye and damaging the retina

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28
Q

What are the two muscles in the eye?

A
  1. Circular muscles
  2. Radial muscles
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29
Q

Describe the pupil reflex in dim light

A

-pupil dilates
-more light enters the eye
-Radial muscles contract
-Circular muscles relax

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30
Q

Describe pupil reflex in bright light

A

Pupil size narrows
Less light enters the ete
Radial muscles relax
Circular muscles contract

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31
Q

What is accommodation?

A

The process of changing the shape of the lens to focus on near or distant objects

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32
Q

How does your eye focus on a near object?

A

The ciliary muscles contract
The suspensory ligament loosen
The lens is thicker and shorter and refracts light rays strongly
The Light rays are diverging

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33
Q

How does your eye focus on a distant object?

A

The ciliary muscles relax
Suspensory ligaments are pulled tight
Lens is pulled thin and only slightly refract rays

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34
Q

Explain myopia (short sightedness)

A

-Can see objects in close focus, distant objects are blurred
-Light is focused in front of retina
-Lens is too thick and curved or long eyeball

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35
Q

Treatment of myopia

A

Concave lens as it spreads out light from distant objects before it reach the eye

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36
Q

Explain hyperopia

A

Light focused behind the retina
Lens to flat or short eyeball and cannot refract enough

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37
Q

Treatment for hyperopia

A

Convex lens bring light rays together more before they reach the eye

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38
Q

Hard and Soft contact lenses

A

On surface of eye and act invisible and are more comfortable to wear
High infection risk and do not last long

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39
Q

Laser surgery

A

-change shape of cornea
MYOPIA: cornea is slimmed down so light is refracted less strongly
Hyperopia: change so refractive power in increased
Risk of unexpected damage which can worsen vision

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40
Q

Replacement lenses

A
  1. Permanent lens in implanted into the eye and natural lens left in place
  2. Faulty lens replaced by artificial lens
    Risk : more invasive than laser surgery and carries risk of damage to retina, lead to sight loss possibly
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41
Q

Function of the Testes

A

Sperm production by meiosis

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42
Q

Function of sperm duct

A

Transports sperm from the testes to the urethra

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43
Q

Function of penis

A

Places sperm into vagina

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44
Q

Function of prostate gland

A

Produces alkaline fluid to provide nutrients to sperm

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45
Q

Function of scrotum

A

Keeps testes outside body and for optimum cooler temperature

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46
Q

Function of ovaries

A

Where eggs mature via meiosis

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47
Q

Function of oviduct

A

Eggs travel to uterus and may be fertilised

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48
Q

Function of uterus

A

Where the foetus develops

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49
Q

Cervix function

A

Entrance to uterus, sperm deposited

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50
Q

Function of vagina

A

Where penis enters female reproductive system

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51
Q

Explain the menstrual cycle

A
  1. Menstruation-loss of lining from uterus if no fertilisation occurs
  2. Lining of uterus thickens
  3. Ovulation egg travels down oviduct to uterus
  4. Lining is thickened in case of fertilisation
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52
Q

What is FSH?

A

Follicle stimulating hormone
- secreted by the pituitary gland
-causes egg to mature in the ovaries

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53
Q

What is LH?

A

-secreted by the pituitary gland
Stimulates release of egg at day 14 of the cycle (ovulation)

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54
Q

What is oestrogen?

A

Secreted by ovaries
Causes lining of uterus to thicken
Stimulates LH production

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55
Q

What is progesterone?

A

-secreted by empty follicle in ovary after egg is released
-Inhibits FSH and LH and maintains uterus lining

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56
Q

Explain the interactions of hormones in the the menstrual cycle

A

-FSH is produced by pituitary gland and released into blood
-It stimulates an egg to mature in the ovaries
-FSH causes oestrogen hormone to be produced by ovary
-Oestrogen causes the uterus lining to repair and thicken
-Increasing levels of oestrogen inhibit the production of FSH by pituitary gland
-Also stimulates production of LH by pituitary gland
-This hormone stimulates the release of an egg -ovulation
-Follicle cells remaining in ovary produce progesterone hormone
-Thickens lining of uterus in case of fertilisation
-Also inhibited FSH and LH so no further eggs develop

57
Q

What happens if the egg is fertilised?

A

-follicle remains in ovary
-more progesterone released
Maintains uterus lining so embryo can implant
As progesterone levels are high it inhibits release of FSH and LH to prevent uterus lining from breaking down

58
Q

What happens if egg is not fertilised?

A

-empty follicle degenerates in the ovary
-progesterone levels fall
-uterus lining breaks down and is lost is menstruation

59
Q

Benefits of contraception

A

Preventing unwanted pregnancies
Pregnancies may lead to risk of mother’s health
Pregnancies have occurred as a result of rape

60
Q

Disadvantages of contraception

A

Ethical and religious concerns

61
Q

Contraceptive pill

A

Adv- 99% effective at preventing pregnancies , easy to use
Dis- may cause changes in weight, mood, high blood pressure because of high levels of oestrogen
Does not protect against STI’s

62
Q

Skin patch

A

Slow release of progesterone
Benefit - small, lasts 1 week, absorbed directly into bs

63
Q

Condoms

A

A- easily obtained, protects against STI’s , no side effects
D- it can tear and let sperm through

64
Q

Spermicide

A

Kill or disable sperm only 70-80% effective

65
Q

Natural contraception

A

Abstaining from intercourse
100% effective
Fertility cant be accurately predicted

66
Q

IUD

A

Very effective
May cause period problems or infections

67
Q

Surgical methods

A

Lasts forever, highly effective, no risk of human error
Low possibility tubes have rejoined

68
Q

Describe the process of IVF

A
  1. Mother given FSH and LH to stimulate egg production
  2. Eggs collected from mother and fertilised with sperm from gather in the laboratory in nutrient medium
  3. Develops into embryos
  4. Inserted into lining of uterus and starts to divide. Injected with O + P to maintain thick lining
69
Q

Issues of fertility treatments

A
  1. Several embryos implanted so high risk of multiple births increasing risk of miscarriage
  2. Low success rate , emotionally upsetting and physically stressful
  3. Some women use IVF to get pregnant at later age than naturally
    4 Some people are against because more embryos are produced than used, used in research but have potential human life
    5 Use of genetic testing is controversial because it could be misused in choosing characteristics of offspring
70
Q

What is a hormone?

A

A chemical substance that coordinates the body’s activities

71
Q

Which type of glands produce hormones?

A

Endocrine glands

72
Q

What is negative feedback?

A

A change occurs away from the norm so the body detects the change and responds to it to return the level back to the normal range

73
Q

What does the pituitary gland produce?

A

Insulin to regulate blood glucose levels

74
Q

What does the thyroid produce?

A

Thyroxine which controls metabolic rate and affects enzyme growth

75
Q

What do the adrenal glands produce?

A

Adrenaline

76
Q

What do the ovaries produce?

A

Oestrogen

77
Q

What do the testes produce?

A

Testosterone

78
Q

What is the cause of Type 1 diabetes ?

A

The inability of the pancreas to produce enough insulin

79
Q

Symptoms of type 1 diabetes

A

Thirsty, weight loss, fatigue

80
Q

What is the treatment for Type 1 diabetes?

A

Insulin injections
Monitor blood glucose levels
Controlling amount of starch in diet

81
Q

What is the cause of Type 2 diabetes?

A

Cells (liver and muscle) become resistant to insulin

82
Q

Treatment for Type 2 diabetes

A

Regular exercise
Low carbohydrate diet

83
Q

`Explain negative feedback if your blood concentration is too low

A

If blood glucose concentration is too low, the pancreas detects the decrease and produces glucagon. This travels to the liver and muscle cells and breaks bond for glycogen to be converted into glucose released into the blood. The blood glucose level rises and is returned back to normal

84
Q

Explain negative feedback system if your blood glucose concentration is too high

A

Pancreas detect increase and produces insulin which stimulates liver and muscle cells to convert glucose into glycogen to be stored which reduced the level or your muscle cells take up more glucose.

85
Q

What does thyroxine do?

A

Controls metabolic rate in your body
Growth and elopement
How much oxygen your tissues use

86
Q

When is adrenaline released?

A

Frightened , angry, excited

87
Q

What does adrenaline do ?

A

Increases mental awareness of surroundings
Make pupils dilate allowing more light to enter
Hearing becomes more acute
Increases breathing and heart rate

88
Q

How do these responses help in the fight or flight response?

A

Give more glucose for more respiration for more energ
Heart rate increases

89
Q

What is your body temperature controlled by?

A

The thermoregulatory centre in the brain hypothalamus which constantly monitors body temperature . Contains receptors sensitive to the temperature of the blood and receives information from the skin

90
Q

Explain what happens when the body temperature is too high

A
  1. Vasodilation occurs and the vessels supplying the skin capillaries increase in diameter. There is more blood flow through the skin capillaries. More heat escapes h through the skin by radiation
  2. Erector muscles replaces. The hairs lie flat on the skin allowing air to freely circulate so no air is trapped to act as an insulator
  3. Sweat glands produce seat which is released onto the skin surface where it evaporates using heat from the body which cools the skin
91
Q

Explain what happens if you body temperature is too low

A

Vasoconstriction occurs : the vessels supplying the skin capillaries decrease in diameter . Less blood flows through the capillaries therefore less heat escapes the skin by radiation
2. The erector muscle contracts and the hairs stand on end creating a layer of air that acts as an insulator and reduces heat loss to surroundings
3. Sweat glands stop producing sweat
4. Our muscles contract more which requires more energy so the rate of respiration increases to release heat energy because it is exothermic so it heats us up

92
Q

How is CO2 produced as a waste product?

A

By the lungs which excrete Carbon Dioxide during exhalation as it is acidic so build up would affect enzyme action . When it dissolves in water it lowers the pH and makes it acidic so we excrete to maintain a relatively constant pH

93
Q

How is urea produced and excreted?

A

From excess amino acids and cannot be stored in the body.
In the liver amino acids are deaminated to form ammonia
Ammonia is toxic and is converted into urea which is released into the bloodstream and filtered through the kidneys

94
Q

What processes of excretion do we had no control of?

A

Water loss via the lungs during exhalation
Water, mineral ions and urea lost through sweat from the skin

95
Q

Processes of excretion that we do have control over

A

Urea, excess water and mineral ions removed from the body by the kidney and excreted as urine

96
Q

What are the kidneys responsible for in homeostasis?

A
  1. Excretion of toxic urea
  2. Osmoregulation- maintaining of water/ ion balance of the blood by adjusting volume and concentration of urine produced
97
Q

Explain the formation of urine

A
  1. Ultrafiltration : when the blood passes through the kidneys it is filtered under high pressure so small molecules are forced out from the blood into the nephron (out from glomerulus to bowman’s capsule )SWAGU( salts/mineral ions, water, amino acids, glucose, urea)
  2. Selective Reabsorption : useful substances that have been filtered are re absorbed from the nephron into the blood. SWAG _ some water and mineral ions but all amino acids and glucose
  3. Urea passes down the nephron with some salts and water (swu) to form urine and passed down ureter into bladder
98
Q

Explain ADH and the negative feedback system

A

ADH is a hormone produced by the pituitary gland which regulates the concentration of water in the bloodstream .
If the water content of the blood is too high the pituitary gland releases less ADH into the bloodstream which binds to the collecting duct and decreases its permeability to H2O so less is re absorbed by osmosis back into the bloodstream making the urine more dilute and less concentrated
If the water content is too low then the hypothalamus detects this and sends a signal to the pituitary gland to release more ADH into the bloodstream increasing the permeability of the tubule which means more water is absorbed by osmosis in the kidney

99
Q

List reasons why kidneys may not work properly

A

Inherited disorders
Cancers or tumours
Accidents
Physical trauma
Untreated can lead to death because of build up fo toxins in the blood like urea

100
Q

Explain dialysis

A

-Removes urea and maintains salt/water balance of blood
Unfiltered blood from artery pumped into machine and returned into a vein
Blood and dialysis fluid are separated by a partially permeable membrane , blood flows in opposite direction to dialysis fluid allowing exchange because of concentration gradient

Dialysis fluid contains:
-A glucose concentration similar to normal blood level
-A concentration similar to normal level in blood
-no urea

101
Q

Explain Kidney Transplantation

A

Healthy kidney from donor
Donors wont have the same antigens
Recipient may produce antibodies that reject the donor’s kidney
Tissue typing reduces risk of rejection

102
Q

Describe 2 ways in which the risk of rejection can be produced

A
  1. By taking immunosuppressant drugs
  2. Carry our tissue typing , test out antigens to find similar match to kidney donor
103
Q

Advantages of transplantation

A

No build up of toxins
Blood conc is kept constant
Prevent high blood pressure
You dont have to restrict your diet
No time wasted on dialysis
In long term it is cheaper than dialysis
More freedom

104
Q

Disadvantage of dialysis

A

Uncomfortable, time consuming
Blood may not clot properly because of anti clotting drugs in dialysis machine

105
Q

Disadvantages of Transplantation

A

Rejection problem finding tissue match
Risk of passing on a disease
Having to take immunosuppressant drugs leading to other infections
Dangers and risks of operations, anaesthetic and painful

106
Q

How does shivering warm the body?

A

It involves muscles contracting and relaxing automatically which requires a lot of energy from respiration which releases a lot of heat energy as waste

107
Q

How does sweat keep us cool?

A

It evaporates and removes heat energy from the skin

108
Q

What are the functions of the kidney?

A

Regulate ion levels
Regulate water levels
Remove urea

109
Q

How does blood enter and leave the kidney?

A

Enters via the renal arteries
Leaves via renal veins

110
Q

Consequences of kidney failure

A

Poor regulation of ion levels
Increase in waste products like urea

111
Q

In a dialysis machine why is fresh dialysis fluid pumped through the machine?

A

To maintain a concentration gradient for diffusion across the membrane

112
Q

Explain why urine contains mineral ions and urea but no glucose or protein

A

-Glucose is filtered but re absorbed
-Ions are filtered but some reabsorbed
-No proteins are filtered
-Urea is filtered but none are reabsorbed

113
Q

Explain why the man’s urine contained a higher concentration of mineral ions and urea on the hot day than on the cool day

A

-he lost water by sweating more so he lost more water therefore the kidney reabsorbs more water and so less volume of urine and less water in the urine

114
Q

Why is albumin (a blood protein) not removed from the blood during dialysis

A

Protein is too big and cannot pass through the filter

115
Q

Give 2 advantages of kidney transplants

A

-Catching infection from operation
-Shortage of donors
Rejection of tissue match antibodies fighting against foreign antigens
Immunosuppressant drugs

116
Q

Explain how sweating helps to keep our body temperature relatively constant

A

Sweat evaporates
Cools the body

117
Q

Explain why the temperature of the brain would change after the student swallowed iced water

A

Blood cooled
Goes to the brain and cools it down

118
Q

A change in brain temperature leads to a change in the temperature of the surface layer of the skin

A

Hypothalamus send impulses to the skin
Vessels supplying capillaries constrict to prevent radiation
Sweat glands stop producing sweat
Hairs on skin erect
Less heat is lost through the skin

119
Q

Describe how the water content of the blood is controlled

A

If too low ADH is released
Pituitary gland
Into the bloodstream
Kidney reabsorbs more water
Urine is more concentrated/less volume
If too high less ADH released
Less water is absorbed by the kidney
Urine is more dilute/larger volume

120
Q

What are plants sensitive to ?

A

Light, water and gravity

121
Q

Why do plants tend to grow towards light and against the force of gravity?

A

Need a source of light energy to absorb maximum sunlight

122
Q

Why do plant toots tend to grow towards moisture, away from light and in the direction of the force of gravity?

A

Do not have chloroplasts so do not need light because they are in the soil and absorbed water and mineral ions from the soil

123
Q

Hormone that controls plant growth?

A

Auxin

124
Q

What are tropisms?

A

Growth responses directed by a stimulus

125
Q

What is phototropism

A

Growth of a plant directed by light
Positive is growth in the direction of light (shoots)
Negative is growth away from light (roots)_

126
Q

What does unequal distribution of auxin mean?

A

Leads to unequal growth rates

127
Q

Explain phototropism in the shoots

A

At the tip of shoots and it promotes growth
Auxin moved to the dark side
Distributes unevenly and accumulates on shaded side

128
Q

What is gravitropism/ geotropism

A

Growth of a plant directed by gravity
Positive is growth in the direction of gravity (down) root
Negative is away from the gravity Shoot
Unequal distribution of auxin leads to unequal growth rates

129
Q

Explain gravitropism in roots

A

Auxin made at tip of root
Distributes unevenly in root and accumulates on lowest side which grows less rapidly and bends in the direction of gravity

130
Q

Explain positive phototropism

A

Light stimulates auxin production at the shoot tip
Auxin diffuses ad accumulates on the shaded side
It promotes growth rate in the shoot causing the shaded side with the highest conc to grow more than the lit side
This causes the shoot to curve towards the light
Once curved auxin curves towards the light
And then distributes evenly in shoot

131
Q

Explain negative phototropism

A

Light —> auxin
In root in accumulates in the shaded side and decreases growth rate
Lit side grows faster causing it to bend away from the light

132
Q

Negative gravitropism

A

Gravity stimulates auxin to be produced at shoot tip causing auxin to be accumulated on the lower side
Unequal distribution of auxin
As auxin promotes growth rate in shoot the lower side grows faster causing the shoot to curve upwards away from the force of gravity

133
Q

Explain positive gravitropism

A

Auxin diffuses backwards and accumulates on the lower side of the roots, unequal distribution of auxin
Lower side with highest conc has lower growth rate causing root to bend towards the force of gravity
Once bent downwards auxin evenly spread and it goes staifght

134
Q

What are other plant hormones?

A

Gibberellins —> initiate seed germination .
Trigger breakdown of food stores in the seed at start of germination and stimulate the growth of plant stems

Ethene —> controls cell division and ripening of fruits.It is a gas

135
Q

What are the uses of auxin?

A

As rooting powders small amount on end of cutting to encourage root growth

136
Q

Uses of plant hormones as weed killers

A

High doses like auxin absorbed by weeds as they have a large surface area and narrow leaved plants take less weed killer

137
Q

Uses of plant hormones for promoting growth in tissue culture

A

Auxin stimulates growth and cell division to produce many genetically identical plants

138
Q

Uses of gibberellins

A

In brewing , barley seeds sprayed to end dormancy
Horticulturists can. Use to promote flowering
Growers can spray to increase size of fruit

139
Q

Uses of ethene -control ripening of food

A

Warmed up and sprayed
Harvested when unripe and stored in cool conditions and sprayed to promote ripening

Biology cells (2 decks)

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