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Biology Paper 2 > Homeostasis and response > Flashcards

Homeostasis and response Flashcards

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1
Q

What is homeostasis needed for ?

A
  • enzyme action
  • all cell functions
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2
Q

What does homeostasis control in the human body?

A
  • blood glucose concentration
  • body temperature
  • water levels
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3
Q

What are nervous and hormonal communication involved in?

A

The automatic control systems, which detect changes and respond to them

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4
Q

What do all control systems have?

A
  • receptors
  • coordination centres
  • effectors
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5
Q

What does the nervous system allow us to do?

A
  • react to our surroundings
  • coordinate actions in response to stimuli
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6
Q

Describe structure of nervous system and what occurs

A
  • receptor cells convert a stimulus into an electrical impulse
  • electrical impulse travels along cells called SENSORY NEURONS to the CNS
  • Here, the information is processed and the appropriate response is coordinated, resulting in an electrical impulse being sent along MOTOR NEURONES to effectors
  • the effectors carry out the RESPONSE ( muscles contracting/ glands secreting hormones)
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7
Q

Why are reflexes important?

A

Prevent individual from getting hurt as information travels down a pathway called a reflex arc, allowing vital responses to take place quickly

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8
Q

How is a reflex arc pathway different from the usual response to stimuli?

A

The impulse does not pass through the conscious part of the brain

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9
Q

Describe the reflex arc

A
  • stimulus detected by receptors
  • impulses sent along a sensory neuron
  • in the CNS the impulse passes to a relay neuron
  • impulses are sent along motor neuron
  • impulse reaches an effector resulting in the appropriate response ( pupils getting smaller)
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10
Q

Describe what occurs when the impulses reaches the end of the first neurone

A
  • a chemical is released into the synapse
  • chemical diffuses across the synapse
  • when chemical reaches the second neurone, it triggers the impulse to begin again in the next neurone
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11
Q

Describe synaptic transmission

A
  • incoming electrical impulse causes neurotransmitters to move to the membrane
  • neurotransmitter is released into synapse
  • neurotransmitter binds to SPECIFIC receptors on the membrane of the next neurone
  • electrical impulse continues to effector
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12
Q

What is reaction time and how can’t it be measured?

A
  • how long it takes you to respond to a stimulus
  • can be measured with the ruler drop test
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13
Q

Name the 3 components of the brain and describe them

A

Cerebral cortex - controls consciousness, intelligence, memory and language, it is the outer part of the brain

Cerebellum- controls fine movement of muscles, rounded structure towards the bottom/ back of the brain

Medulla- controls unconscious actions ( breathing, heart rate ), found in the brain stem in the front of the cerebellum

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14
Q

Why is investigating brain function and treating brain damage/disease difficult?

A
  • is complex and delicate
  • is easily damaged
  • drugs given to treat diseases cannot always reach the brain because of the membranes that surround it
  • is not fully understood which part of the brain does what
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15
Q

Name methods for studying the brain and describe them

A
  • studying patients with BRAIN DAMAGE - observing the changes in an individual following damage on a certain area of the brain, can provide information on the function this area has
  • ELECTRICAL STIMULATION- use electrical currents to stimulate different parts of the brain to learn functions of specific neurones as the stimulation may result in a mental or physical change
  • MRI - magnetic resonance imaging scanner can be used to create an image on the brain which can show which part of the brain is affects by a tumour or which part is active during a specific task
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16
Q

Function of retina

A

Layer of light sensitive cells found at the back of the eye.
When light hits this, the cells are stimulated. Impulses are sent to the brain, which interprets the information to create an image

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17
Q

Optic nerve function

A

A nerve that leaves the eye and leads to the brain
Carries the impulses from the retina to the brain to create and image

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18
Q

Sclera function

A

White outer layer which supports structures inside the eye
Is strong to prevent damage it the eye

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19
Q

Cornea function

A

The see-through layer at the front of the eye
It allows light through and the curved surface bends and focuses light onto the retina

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20
Q

Function of iris

A

Muscles that surround the pupil
They contract or relax to alter the size of the pupil

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21
Q

Function of ciliary muscles and sensory ligaments

A

Hold the lens in place
They control its shape

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22
Q

Describe what happens to the iris in bright light

A

The circular muscles contract and radial muscles relax to make the pupil smaller- avoiding damage to retina

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23
Q

Describe what happens to the iris in bright light

A

The circular muscles contract and radial muscles relax to make the pupil smaller- avoiding damaging to retina

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24
Q

Describe what happens to the iris in dim light

A

The circular muscles relax and the radial muscles contract to make the pupil larger- so more light can enter to create a better image

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25
Q

Define accommodation

A

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

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26
Q

What happens when focussing on a near object

A

The ciliary muscles contract
The suspensory ligaments loosen
The lens is then thicker and more curved
Meaning light rays are refracted more/strongly

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27
Q

What happens when focussing on a distant object

A

The ciliary muscles relax
Suspensory ligaments tighten
Lens becomes thinner- meaning light rays are only slightly refracted

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28
Q

When do eye defects occur and name 2 common ones

A

Occurs when light can’t focus on the retina
Myopia (short sightedness) the lens is too curved so distant objects appear blurry
Hyperopia (long sightedness) the lens is too flat so it can’t refract light enough

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29
Q

Name treatments for eye defects

A

Spectacle lenses (glasses) - concave lenses to spread out the light to treat myopia and convex lenses to bring the rays together to treat hyperopia

Contact lenses- work the same as glasses but allow activities (sport) to be carried out

Laser eye surgery- lasers can be used to either reduce the thickness of the cornea (so it refracts light less) to treat myopia or change its curvature (so it refracts light more strongly) to treat hyperopia

Replacement lens- hyperopia can be treated by replacing the lens with an artificial one made of clear plastic. The risk include damage to retina or cataracts developing

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30
Q

What is thermoregulation

A

The process that allows your body to maintain its core internal temperature (37degrees)

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31
Q

What is the thermoregulatory centre and what does it do?

A

Monitors and controls body temperature and is found in the brain
-has receptors that monitor the temp of the blood
-has receptors in the skin that send impulses to the thermoregulatory centre

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32
Q

How do our bodies respond when our bodies are too hot?

A

-sweat glands produce sweat because evaporation of water from sweat takes heat away from body
-blood vessels dilate (vasodilation) as more blood flows closer to the surface of skin, allowing heat to escape
-hairs lie flat so body is able to loose heat

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33
Q

How do our bodies respond when our bodies are too cold?

A

-sweating stops, so heat energy is not lost
-shivering - skeletal muscles contract rapidly to generate heat from respiration
-hairs stand on end to create an insulating layer, trapping warm air
-blood vessels constrict (vasoconstriction) meaning less heat radiated from skins surface, less heat lost

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34
Q

What is the role of the endocrine system?

A

Sends hormones (chemical messengers) around the body
When they reach a target tissue they produce a response
Is made up of glands which secrete hormones directly into bloodstream

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35
Q

Function of pituitary gland

A

The master gland
Secretes hormones into the blood to either have an effect on the body or to act on other glands to stimulate them to produce different hormones

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36
Q

What is the function of pancreas?

A

Secretes insulin
Controls blood glucose levels

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37
Q

Function of thyroid

A

Secretes thyroxine
Controls metabolic rate, heart rate and temp

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38
Q

What is the function of adrenal gland?

A

Secretes adrenaline
Involved in the flight or fight response

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39
Q

What is the function of ovaries

A

Secretes oestrogen
Involved in the menstrual cycle and the development of female secondary sexual characteristics

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40
Q

What is the function of testes

A

Secretes testosterone
Involved in production of sperm and the development of male secondary sexual characteristics

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41
Q

What is a difference between the nervous and endocrine systems

A

Endocrine in much slower but it lasts for longer

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42
Q

Why does the concentration of glucose in blood need to be kept within a certain limit

A

As glucose is needed by cells for respiration- controlled by pancreas

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43
Q

What increases glucose levels in blood?

A

Eating foods that contain carbohydrates

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44
Q

What happens if blood glucose levels are too high?

A

The pancreas releases insulin into blood
Insulin causes cells and tissues to absorb glucose which will be used for respiration
Excess glucose is converted to glycogen by liver
Blood sugar level returns to normal

45
Q

What causes blood glucose to decrease

A

Rigorous activity as it uses glucose for respiration meaning there is less in blood

46
Q

What happens when blood glucose levels are too low

A

Pancreas releases the hormone glucagon
Glucagon binds to the liver cells causing glycogen to be broken down into glucose
Glucose is released into blood, increasing blood glucose concentration, so it returns back to normal

47
Q

What is type 1 diabetes and what causes it

A

When pancreas can’t produce enough insulin
Usually starts in young children or teenagers
Cause could be a genetic element

48
Q

What are the symptoms of type 1 diabetes

A

Blood glucose can rise to a fatal amount
Glucose is excreted with urine and lots of urine is produced leaving individual thirsty
Lack of energy
Weight loss

49
Q

What are the treatments for type 1 diabetes?

A

Insulin injections at meal times which results in glucose being taken up from bloodstream
Advised to limit the intake of simple carbohydrates which contain lots of glucose
Doctors are attempting to cure diabetes with pancreas and pancreatic cell transplants and genetically engineering pancreatic cells from mice to make insulin

50
Q

What is type 2 diabetes and what is a risk factor/cause?

A

When the body cells no longer respond to insulin

Risk factor/cause- obesity and lack of exercise

51
Q

What is a symptom of type 2 diabetes?

A

Blood glucose levels can rise to a fatal amount

52
Q

What are the treatments for type 2 diabetes?

A

Reducing number of simple carbohydrates in diet
Losing weight
Increasing exercise
Also drugs to make insulin more effective on body cells, help the pancreas make more insulin or reduce amount of insulin absorbed in gut

53
Q

What happens if body cells lose or gain too much water by osmosis

A

They don’t function properly

54
Q

What is the function of the kidneys?

A

Maintains the balance of water and other substances in body by removing toxic urea from the body in urine
As urine is produced constantly the bladder must store it

55
Q

How do kidneys make urine?

A

By filtering out the waste products
And selectively reabsorbing useful substances- all glucose, some ions and some water

56
Q

What happens when there is too much water in blood ?

A

The hypothalamus detects too much water in blood
Pituitary gland secretes ADH into blood
It travels in the bloodstream to the kidney tubules
The tubules (walls of kidney) become less permeable to water
So less water returns to blood via bloodstream
More water is lost in urine (less concentration)
Water levels return back to normal (negative feedback loop)

57
Q

What will happen to the volume of urine produced when ADH is secreted?

A

Causes more water to be reabsorbed back into blood via osmosis
Low volume of concentrated urine produced

58
Q

Define kidney failure

A

When your kidneys stop working
Meaning waste products build up which can be harmful to the body, eventually resulting in death

59
Q

Explain a different way water can leave the body

A

Can leave the body at the lungs as a result of exhalation or from the skin in sweat
Depending on the concentration of water in the blood, a certain amount of water is lost in urine

60
Q

Explain how ions are taken in and leave the body

A

Taken in via food
If ion concentration is incorrect then too little or too much water may enter body cells. This is because the water potential of the blood would be altered
They are least in sweat
In kidneys, certain amounts of ions are reabsorbed into blood after it has been filtered to ensure the concentration in blood is maintained

61
Q

How does urea leave the body

A

Amino acids are the products of the digestion of proteins
Amino acids are deaminated (removal of an amino acid group from an amino acid) in the liver to form ammonia. As ammonia is toxic it’s converted to urea for safe excretion
Is lost in sweat
In the kidneys, it’s filtered out of blood

62
Q

What does anti-diuretic hormone (ADH) control?

A

Controls the amount of water reabsorbed by kidneys/loss of water as urine

63
Q

What is diuretic?

A

Chemical that increases urination

64
Q

Where is ADH released and when?

A

Released into the pancreas by the pituitary gland when a receptor in the brain detects that blood is too concentrated

65
Q

Explain how the structure of the kidneys helps carry out its function

A

Kidney contains millions of filtering units called nephrons
Each nephron is made of a tubule and is responsible for cleaning the blood by removing urea and excess water and minerals
All of the blood in the body passes through your kidney once every 5 mins

66
Q

Describe what a nephron does in the kidney

A

-Blood enters under high pressure
-Filtration- small molecules (glucose,water,mineral ions, urea) are forced out of blood into tubules
-Larger molecules (red blood cells,larger proteins) remain in bloodstream
-the filtered liquid passes through the tubule
- selective reabsorption- useful substances are absorbed back into blood
- remaining liquid forms urine
- urine travels to the bladder for storage

67
Q

Describe the 2 functions for kidney failure

A

Dialysis- when the function of the kidneys it carried out using an artificial membrane
-Blood moves between partially permeable membranes surrounded by dialysis fluid
-Useful ions and glucose are not lost from blood but urea, excess ions and water diffuse across the membrane
-has to be done 3 times a week, the process takes 4 hours
-acts as an artificial kidney and keeps patient alive whilst waiting for a transplant
Disadvantage- Can cause blood clots, takes a lot of time, have to follow strict diet, build up of waste products between sessions can make u feel ill

Kidney transplant - providing individual with healthy kidney, only cure
Transplanted from people who died suddenly, or from people still alive
Don’t need to visit hospital as regularly and is cheaper than dialysis
Disadvantage- can be rejected from body as a result of immune system recognising the antigens in donor organ as foreign ( reduced by immunosuppressant drugs)
Person can be left vulnerable to other diseases
Transplanted kidneys don’t last forever

68
Q

What happens during puberty?

A

Reproductive hormones begin to be released
These cause secondary sexual characteristics to develop in men and women

69
Q

What primary sex characteristics are u born with?

A

Females- ovaries
Male- testes

70
Q

Describe the sex hormones in men and women

A

Male- testosterone, produced in testes, stimulates the production of sperm
Female- oestrogen, produced in ovaries, produces physical changes and is involved in menstrual cycle

71
Q

What happens to females during puberty?

A

Eggs being to mature
One is released from ovaries approximately every 28 days- this is called ovulation

72
Q

State the role of female sex organs

A

Fallopian tube/oviduct- egg travels
Ovaries- eggs mature
Uterus/ womb- foetus develops
Cervix - entrance to the uterus

73
Q

Define menstrual cycle

A

The regular natural changes that occurs in the uterus and ovaries that make pregnancy possible

74
Q

Define what occurs during menstrual cycle

A

Begins with the lining of uterus breaking down, women has her period
They layer then builds up again until ovulation (day 14) occurs - an egg is released from the ovary and moves to the uterus via fallopian tube
If a fertilised egg hasn’t been embedded in the lining after 28 days, it begins to break down and cycle continues

75
Q

Name and describe the main hormones involved in menstrual cycle

A

Follicle stimulating hormone (FSH) - causes the maturation of an egg in the ovary. Produced in pituitary gland and stimulates the ovaries to produce oestrogen
Oestrogen- causes the lining of uterus to grow again. Produced in ovaries, secreted as a result of FSH.stimulates the production of LH and inhibits the secretion of more FSH
Lutenising hormone (LH) - produced in pituitary gland as a result of hormone oestrogen. Its release results in ovulation
Progesterone- produced in ovaries and secreted from egg follicle, maintains lining of uterus and supports pregnancy of egg is fertilised. Inhibits release of FSH and LH

76
Q

Describe hormonal methods of contraception

A

The contraceptive patch - taken regularly or bodies own hormones will be released, leading to egg maturing
Mixed pill contains oestrogen and progesterone
Means oestrogen levels are constantly high, inhibiting FSH so no eggs mature
Lining stops developing and mucus in cervix becomes thick so sperm can’t move through
Side effects- mood swings, depression, high blood pressure

Progesterone only pill- has less side effects in comparison to mixed pill

The contraceptive patch- contain oestrogen and progesterone
Is small and stuck on skin
Lasts for 1 week

The contraceptive implant- releases a continuous amount of progesterone
Prevents ovaries from releasing egg, thickens mucus so sperm can’t swim and stops fertilised eggs from embedding in uterus
Lasts for 3 years

The contraceptive injection- made up of progesterone
Same effect as implant
Lasts for 2/3 months

The plastic intrauterine device (iud) - releases progesterone
Same effect as implant
T-shaped, inserted into uterus

77
Q

Decline non hormonal methods of contraception

A

Chemical methods involve spermicides. These kill or disable sperm but are only 70% effective

Barrier methods include condoms and diaphragms
Condoms prevent individual from contracting sexually transmitted diseases but can tear
Diaphragm is a plastic cup which is positioned over cervix, used with spermicides

Copper intrauterine device works by killing sperm in uterus and stopping any fertilised embryos from implanting in uterus lining

Surgical methods of male and female sterilisation involve cutting and tying the fallopian tubes or sperm ducts
Lasts forever

Abstaining from intercourse ensures egg isn’t fertilised
Others may only abstain during ovulation

78
Q

Positive and negatives of contraceptive methods

A

+
Pill is easy to use
Condoms have no side effects
IUD are very effective and last up to 5 years
Implant can last up to 3 years
Spermicides are readily available
Barriers can also prevent spread of diseases

-
IUD can cause period problems and infections
Surgery is permanent
Spermicides are not thought to be very effective
Condoms can become easily damaged
Pill has side effects
Discomfort on implantation

79
Q

Describe process of IVF

A

Mother is given FSH and LH to stimulate the maturation of several eggs
Eggs are collected from the mother and fertilised by sperm from father
The fertilised egg develops into embryos
When eggs are tiny balls of cells one or 2 embryos are inserted into mother’s uterus
Spare embryos can be frozen for future attempts or donated to their couples
Sometimes they are destroyed

80
Q

What are the positives and negatives of IVF

A

+
Provided a way for an infertile couple to have a child

-
Physically stressful, woman may have reactions to hormones
Emotionally stressful- may not work
Can lead to multiple births
Can be expensive if process needs repeating

81
Q

What is negative feedback

A

Initiating corrective mechanisms whenever the internal environment deviates from its normal or acceptable level

82
Q

Explain what a negative feedback does

A

Maintains a steady state
Reverses any changes

83
Q

Give examples of negative feedback

A

Insulin and glucagon
Sex hormones
Osmoregulation
Thermoregulation

84
Q

What does thyroxine do?

A

Regulated metabolic rate
Also important in growth and development e.g brain development in children

85
Q

How is thyroxine released

A

By the thyroid gland
It uses iodine from your diet to produce thyroxine
Its release is stimulated by the thyroid stimulating hormone

86
Q

What is metabolism?

A

Sum of all the chemical reactions in body

87
Q

What are the levels of thyroxine controlled by?

A

Negative feedback

88
Q

What happens when thyroxine levels are too low?

A

Sensors in Brian detect decreased thyroxine levels
Pituitary gland releases thyroid stimulating hormone
Stimulates the thyroid to secrete thyroxine
Thyroxine levels rise

89
Q

What happens when thyroxine levels are too low?

A

Sensors in Brian detect decreased thyroxine levels
Pituitary gland releases thyroid stimulating hormone
Stimulates the thyroid to secrete thyroxine
Thyroxine levels rise

90
Q

What happens if thyroxine levels are too high?

A

Sensors in brain detect
Inhibits release of TSH
Thyroid gland secretes less thyroxine
Thyroxine levels fall

91
Q

Where and when is adrenaline produced?

A

In times of fear, stress, anger or excitement
From adrenal glands
Involves no negative feedback loop

92
Q

What are the effects of adrenaline?

A

Increased heart and breathing rate to deliver more oxygen and glucose to brain and muscles for respiration
Glycogen stored in liver is converted to glucose for respiration
Pupils dilate to let more light in
Blood flow to muscles increases
Blood flow to digestive system decreases

93
Q

What detects thermoregulation

A

Hypothalamus

94
Q

What would happen to our body without thermoregulation?

A

Hyperthermia (too cold)
Hypothermia (too hot)

95
Q

What would happen to our body without thermoregulation?

A

Hyperthermia (too cold)
Hypothermia (too hot)

96
Q

Why do plants need hormones?

A

To coordinate and control growth
They are needed for tropisms eg phototropism - response to light

97
Q

How do hormones produce the appropriate response?

A

Hormones move from the place they are made to where they are needed in order to produce appropriate response
E.g gravitropism - response to gravity
Hydrotropism- response to water

98
Q

What do plants need to respond to?

A

Light intensity and direction
Gravity (direction of root and shoot)
Water

99
Q

What are auxins and what do they do

A

Specific growth hormones
They coordinate responses and control growth
These responses are known as tropisms to directional growth response causing movement of part of an organism

100
Q

What are positive and negative tropisms

A

Positive- growth towards stimuli
Negative - growth away from stimuli

101
Q

Describe phototropism in plants

A

Stem and leaves are positively phototrobic (grow towards light)
Contain chloroplasts which maximise photosynthesis
Roots are negatively phototrobic

102
Q

Describe gravitropism in plants

A

Roots are positively gravitrobic as they grow with gravity to absorb more mineral ions and anchor plant

103
Q

Describe hydrotropism in plants

A

Roots are positively hydrotrobic - grow towards water to absorb it

104
Q

How do auxins work/ cell elongation?

A

Plants grow towards light
The auxins are evenly distributed so the shoot grows up
The plant is exposed to light on one side causing auxins to move to shaded side
Shoot bends towards light so only that side elongates
Plant receives more light, meaning photosynthesis can occur faster
Once light falls equally on all side of shoot, auxins distribute evenly again

105
Q

How can u investigate the effect of light or gravity on newly germinated seedlings

A

By varying conditions
Placing in cardboard box and shining light from one side
Attaching a Petri dish containing seedlings to a wall

106
Q

Describe 2 other plant hormones

A

Gibberellins - important to stimulate seed germination
Ethene - involved in cell division and ripening of fruits

107
Q

Where and why are plant hormones used

A

Used to alter plant growth
Used in areas such as agriculture and horticulture to increase yield, obtain desirable chemicals and to lower costs

108
Q

Define what auxins are used for

A

As weed killers- many weeds are broad-leaved
Weed killers containing auxin have been synthesised so they only affect broad leaved plants
Increased amount of auxin causes cells to grow too rapidly resulting in weed dying

As rooting powders- plants with desirable features are cloned to make more plants with the same feature
One way to clone is to take a cutting from original plant
Rooting powder containing auxins is applied to it and is placed in ground
Roots grow and the new plant begins to grow very quickly

To promote growth in tissue culture - another way to clone a plant is to use tissue culture
Cells form the plant are taken and placed in a growth medium containing nutrients
Hormones such as auxins are added
Cells begin to form roots and shoots

109
Q

What are gibberellins used for?

A

Ending seed dormancy- in brewing industry, the germination rate of barley seeds is increased to make malt

Promoting flowering - allows it to flower in any conditions with bigger flowers

Increasing fruit size- seedless fruit is generally smaller so sprayed with givberellins to increase size

Biology Paper 2 (4 decks)

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