Topic 5 - Homeostasis And Response (paper 2) Flashcards
1
Q
What is homeostasis?
A
The regulation of internal conditions of a cell or organism to maintain optimum conditions for functions in response to internal and external changes
2
Q
Why is homeostasis important?
A
Cells need the right conditions in order to function properly, including the right conditions for enzyme action
3
Q
What do automatic control systems include?
A
Nervous responses or chemical responses
4
Q
What internal conditions are controlled?
A
Blood glucose concentration, body temperature, water levels
5
Q
What do all control systems include?
A
Cells called receptors, which detect stimuli (changes in the environment)
Coordination centre (brain,spinal cord, pancreas) which receive and process information from receptors
Effectors (muscles and glands) which bring about responses that restore optimum levels
6
Q
What does the nervous system do?
A
It enables humans to react to their surroundings to coordinate behaviour and respond to stimuli
7
Q
What does the CNS consist of?
A
Vertebrates - brain and spinal cord
Mammals - CNS is connected to the body by sensory neurones and motor neurones
8
Q
How does information from receptors pass along cells?
A
As electrical impulses to the CNS
9
Q
What is the function of sensory neurones?
A
Carrying information as electrical impulses from receptors to the CNS
10
Q
What are motor neurones?
A
Neurones that carry electrical impulses from the CNS to effectors
11
Q
What are effectors?
A
Muscles and glands which respond to nervous impulses
12
Q
What are receptors?
A
Cells that detect stimuli
13
Q
Examples of receptors?
A
Taste receptors, ears (sound receptors), light receptors on the retina
14
Q
What is the path of a reflex arc?
A
Stimulus
Receptor - eyes, ears
Sensory neurone
Relay neurone - CNS - brain and spinal cord
Motor neurone
Effector - muscles and glands
Response
15
Q
Why are reflex actions important?
A
They’re quick, automatic, protective and don’t involve the conscious part of the brain
16
Q
Examples of reflexes
A
Sneezing
Blinking when getting dust in your eye
When bright light is shone in your eye, your pupil constricts
Adrenaline is automatically released when you get a shock
17
Q
Outline the reflex arc for getting stung by a bee
A
The stimulus (bee sting) is detected by receptors, sending impulses along a sensory neurone to the CNS
Impulses reach a synapse between the sensory neurone and the relay neurone, causing chemicals to be released, these cause impulses to be sent along the relay neurone
Impulses reach a synapse between the relay neurone and the motor neurone, releasing chemicals which cause an impulse to be sent along the motor neurone
Impulses title along the motor neurone to the effector - muscle
The muscle contracts, causing the hand to move away from the bee
18
Q
What is a synapse?
A
A gap between neurones
19
Q
How are signals transferred across synapses?
A
Electrical impulse travels along neurone A
Neurotransmitter chemical made by neurone A
Neurotransmitter chemical diffuses across the synapse
Neurotransmitter chemical attaches to receptors on neurone B
Neurone B sends electrical impulses
20
Q
What is negative feedback?
A
It brings levels in your body back to normal when they are too high or too low
21
Q
Describe negative feedback for when a level is too high
A
Receptor detects stimulus - high level
Coordination centre receives and processes the information, then organises a response
Effector produces a response, counteracting the change and then restores the optimum level, decreasing the level
Effectors continue producing responses until they’re not stimulated by the coordination centre. However, the level can change too much, up the receptor detects this and negative feedback starts again
22
Q
What does the brain control?
A
Complex behaviours
23
Q
What is the brain made of?
A
Billions of interconnected neurones and has different regions that carry out different functions
24
Q
What’s the function of the cerebral cortex?
A
Controls memory, language, consciousness, intelligence
25
What’s the function of the cerebellum?
Fine motor control, coordination, balance
26
What’s the function of the medulla?
Unconscious activities, like breathing and heart rate
27
What’s the function of the hypothalamus?
Regulation of body temperature
28
What are 3 methods for studying the brain?
MRI scanning techniques, studying patients with brain damage, electrically stimulating different parts of the brain
29
Outline studying patients with brain damage?
Identify the areas of the brain that are damaged and see what abilities or functions are affected
30
Outline electrically stimulating different parts of the brain?
Use electrodes to stimulate different parts of the brain and observe what effects it has on the patient. Give the patient tasks to do and use PET and MRI scans to see the more active parts of the brain
31
Outline MRI scans?
Magnetic resonance imaging produces detailed pictures of the brains structures. The patients is given tasks during the scan to find out which areas of the brain are more active
32
What are the problems associated with studying the brain?
Ethical issues with studying brain damage
Electrical stimulation is risky and can cause brain damage
Scanners are expensive and the patients has to be still
The brain is complex and different parts interact so it’s difficult to get a clear picture
33
What are the problems with treating the brain?
There’s a wide range of problems that may affect the brain (tumours, infection etc)
The brain is delicate and the skull is fragile
The brain is complex and it’s difficult to produce drugs that reliably work
34
Pro and cons of MRI scans
Pros - can detect cancer cells, clots and abnormal blood flow, non invasive, no ionising radiation, safer than a CT, safe for pregnant women and babies
Cons - noisy, claustrophobic
35
Pros and cons of CT scans
Pros - quicker than MRI, accurate diagnosis of many conditions
Cons - ionising radiation risk, dye injection, cancer risk
36
Pros and cons of EEGs
Pros - safe due to no electricity being put into the body, can detect epilepsy, fits and memory problems, direct feedback from patient
Cons - can’t detect cancer, needs a highly trained expert, risk of brain damage
37
What is the eye?
A sense organ containing receptors sensitive to light and colour
38
Function of the retina
Contains light receptor cells sensitive to colour
39
What two types of receptor cells are in the retina?
Cone and rod cells
40
Function of the optic nerve
Contains sensory neurones that carry impulses on the receptors on the retina to the brain
41
Function of the sclera
Tough, supporting wall of the eye
42
Function of the cornea
Transparent to let light enter the eye. Its curved surface bends the light and focuses it towards the retina
43
Function of the iris?
Circular muscle that controls the diameter of the pupil and controls how much light reaches the retina
44
Function of the suspensory ligaments and ciliary muscles
Control and change the shape of the lens
45
Function of the blind spot
No light sensitive cells so no light falling here is detected
46
What’s accommodation?
Changing the shape of the lens to focus on near or distant objects
47
What happens to eye when bright light is detected and why?
Circular muscles contract
Radial muscles relax
Pupil constricts
So less light enters the eye, in order to protect it from
48
What happens to the eye in dim light?
Circular muscles relax
Radial muscles contract
Pupil dilates
49
What does the eye do to focus on near objects?
Ciliary muscles contract, suspensory ligaments loosen, lens is thicker and refracts light rays strongly
50
What does the eye do to focus on distant objects?
Ciliary muscles relax, suspensory ligaments are pulled right, lens is pulled thin and only slightly refracts light rays
51
What is myopia?
Short sightedness
52
What is hyperopia?
Long sightedness
53
What happens when there are defects to the eye?
Rays of light don’t focus on the retina
54
How does hyperopia occur?
When the lens is the wrong shape and doesn’t refract the light enough and the eyeball is too short. The I,ages are focus are brought into focus behind the retina
55
What lens can be used to treat hyperopia and how does it work?
A convex lens (curves outwards) and it refracts the light rays so they focus on the retina
56
How does myopia occur?
When the lens is the wrong shape and refracts the light too much or the eyeball is too long. The images of distant objects are brought into focus in front of the retina
57
What lens can be used to treat myopia and how does it work?
A concave lens (curves inwards) corrects the eye, so that the light rays focus on the retina
58
What are the 3 treatments for vision defects?
Contact lenses, laser eye surgery, replacement lens surgery
59
What are contact lenses?
Thin lenses that sit on the surface of the eye and are shaped to compensate for the fault in focusing. They refract the light onto the retina
60
What are the pros and cons of contact lenses?
Pros - can’t be seen, lightweight, easier to play sport, soft lenses are more comfortable, hard lenses last a long time
Cons - hard lenses are uncomfortable, have to be sterilised each night, risk of eye infections with soft lenses more so than hard lenses
61
What is laser eye surgery?
A laser is used to vaporise tissue, changing the shape of the cornea
Myopia can be improved by reducing the thickness of the cornea and making it less powerful
Hyperopia can be improved by changing the curve of the cornea and making it more powerful
62
What are the pros and cons of laser eye surgery?
Pros - no longer need glasses or contact lenses, surgeon can precisely control how much tissue the laser takes off
Cons - only available to adults once their eyes have stopped growing, risk of complications like infection or vision being worse than before due to reaction of eye
63
What is replacement lens surgery?
Replacing the lens of the eye. The natural lens of the eye is removed and an artificial lens made of clear plastic is inserted in its place
64
What are the pros and cons of laser eye surgery?
Pros - effective for treating hyperopia
Cons - higher risks than laser eye surgery, like damage to the retina which could lead to loss of sight
65
What is bodily temperature?
37°C
66
Why does body temperature have to be maintained?
Enzymes have an optimum temperature and will not catalyse reactions efficiently a few degrees above or below normal body temperature
67
What is body temperature controlled and monitored by?
The thermoregulatory centre in the brain, which contains receptors sensitive tissue the temperature of the blood
The skin contains temperature receptors and sends nervous impulses to the thermoregulatory centre
68
What happens when the body temperature is too high?
Hair muscles relax making hairs lie flat
Sweat is produced from the sweat glands and evaporates from the skin, transferring energy to the environment
Vasodilation - the blood vessels supplying the skin dilate so more blood flows close to the surface of the skin, transferring energy to the environment
69
What happens when the body temperature is too low?
Hair muscles contract making hair muscles erect to trap an insulating layer of air
The sweat glands do not produce sweat
Vasoconstriction - blood vessels supplying skin capillaries constrict to close off the skin’s blood supply
Shivering - the skeletal muscles contract and relax rapidly. This needs respiration, which transfers some energy to warm the body
70
Describe the negative feedback for a rise in body temperature
The thermoregulatory centre detects the change by receiving information from the temperature receptors and triggering the effectors
Effectors produce a response : sweat glands produce sweat, hairs lie flat, blood vessels supplying capillaries at the skin surface dilate - vasodilation
Body temperature decreases
71
Describe the negative feedback for a decrease in body temperature
Thermoregulatory centre detects the change by reaching information from the temperature receptors and triggers the effectors
Effectors produce a response : hair muscles contract so hairs are erect, sweat glands don’t price sweat, blood vessels constrict so less blood flows to the skin surface (vasoconstriction) and skeletal muscles contract (shivering)
72
How does shivering warm the body?
Shivering involves muscles contracting and relaxing automatically. This requires lot of energy from respiration, which in the process releases a lot of heat energy as waste
73
What is the endocrine system?
It is composed of glands which secrete chemicals called hormones into the bloodstream
74
Where are hormones released into?
The bloodstream
75
Where are hormones in the blood carried to?
A target organ where it produces an effect
76
Compare the endocrine system to the nervous system
Nervous system:
- very fast action
- response is short lived
- act on a very precise area/ use electrical impulses
Endocrine system:
- slower action
- response is long lived
- act in a more general way/ uses chemical messages
77
Why can’t pain signals or certain information be carried to the brain using hormones?
Hormones are too slow, and some messages need to be passed to effectors really quickly
78
Give an example of a long hormonal response
When you get a shock, adrenaline is released into the body
79
What is the function of the pituitary gland and where is it found?
The pituitary gland in the brain is a ‘master gland’ which secretes several hormones into the blood in response to body conditions. These hormones in turn act on other glands to stimulate other hormones to help released to bring about effects.
80
Where is the thyroid located and what is its functions?
Located in the neck and produces thyroxine, which is involved in regulating metabolic rate
81
What produces TSH and what does it do?
Pituitary gland and it stimulates the thyroid gland to make thyroxine
82
What do the ovaries do?
Produce oestrogen, which is involved in the menstrual cycle
83
What do the testes do?
Produce testosterone, which controls puberty and sperm production in males
84
What does the adrenal gland do?
Produces adrenaline, which is used to prepare the body for a ‘fight or flight’ response
85
What does the pancreas do?
Produces insulin, which is used to regulate the blood glucose level
86
What is blood glucose concentration monitored and controlled by?
The pancreas
87
What causes blood glucose levels to increase?
Eating a sugary meal, eating foods containing carbohydrate
88
What causes blood glucose levels to decrease?
The normal metabolism of cells
Vigorous exercise
89
What hormones are involved in the regulation of glucose levels in the blood?
Insulin and glucagon
90
What happens if blood glucose concentration is too high?
The pancreas produces the hormone insulin that causes glucose to move from the blood into the cells.
Glucose is taken in by cells and used for respiration
In liver and muscle cells excess glucose is converted to glycogen for storage
Blood glucose levels fall
91
What happens if blood glucose concentration is too low?
The pancreas releases glucagon
Glycogen in the liver is broken down into glucose. Amino acids and fats are broken down
Blood glucose levels increase
92
Where is glycogen stored?
In the liver and muscles
93
When is insulin produced?
When blood glucose levels are too high
94
When is glucagon produced?
When blood glucose levels are too low
95
What is type 1 diabetes?
A disorder in which the pancreas fails to produce sufficient insulin. It is characterised by uncontrolled high blood glucose levels
96
What are some treatments for type 1 diabetes?
Insulin therapy
Insulin injections before meals - ensures that glucose is removed from the blood quickly once the food has been digested, stopping the level from getting too high
Limiting carbohydrate intake
Regular exercise but needs to be carefully planned to ensure blood glucose levels are steady
97
What are some possible ‘cures’ for type 1 diabetes?
Pancreas transplant however it’s risky and there is a lack of donors
Immunosuppressant drugs will then need to be taken to regent organ rejection
Transplanting pancreatic cells has had little success
Using embryonic stem cells, but it’s not ethically acceptable
Genetic engineering
98
What is type 2 diabetes?
When the body cells no longer respond to insulin produced by the pancreas, meaning blood sugar levels can rise to a dangerous level
99
Who is type 2 diabetes more common in?
Older people
100
What are some risk factors for type 2 diabetes?
Obesity, lack of exercise, poor diet
101
What are some treatments for type 2 diabetes?
Having a carbohydrate controlled diet
Losing weight
An exercise regime
If the other methods aren’t effective them drugs can be taken which help the insulin work better, help the increase make more insulin or reduce the amount of glucose that is absorbed from the small intestine
102
What are some possible ‘cures’ for type 2 diabetes?
Lose weight
Exercise regularly
Reduce simple carbohydrates in take
103
Negative feedback systems work to…
…maintain a steady state
104
If a factor in the internal environment increases…
…changes take place to reduce it and restore the original level of
105
If a factor in the internal environment decreases…
…changes take place to increase it and restore the original level
106
What is selective re-absorption?
The process in the kidneys where the materials needed in the body such as glucose, some mineral ions, and water are re absorbed back into the blood from the filtrate
107
What is the thermoregulatory centre?
The area of the brain that is sensitive to the temperature of the blood
108
What is vasoconstriction?
The construction or narrowing of the blood vessels
109
What is vasodilation?
The dilation or opening up of the blood vessels
110
What happens if the blood becomes too dilute?
Water moves into cells by osmosis
The cells can burst
111
What happens if the blood becomes too concentrated?
Water moves out of the cells by osmosis
Causing the cells to shrink
112
How does water leave the body?
Via the lungs during exhalation
Sweat containing water, ions and urea
Via the kidneys in urine
113
What is excretion?
Removing waste products from cells and then from the body. The waste products have been produced by cellular activities
114
What is egestion?
Removing undigested material (food) from the digestive tract
115
What is lost from the skin in sweat?
Water, ions and urea
116
What is removed via the kidneys in urine?
Excess water, ions and urea
117
What happens if body cells lose or gain too much water by osmosis?
They don’t function efficiently
118
How is ammonia formed in the body?
Digestion of proteins results in excess amino acids which need to be excreted safely
In the liver the amino acids are deaminated to form ammonia
119
What is ammonia converted to and why?
Urea as it is toxic, so it’s converted to be safely excreted
120
How is urea removed from the body in urine?
Excess amino acids
Broken down by the liver (deamination)
Ammonia, which is highly toxic, is produced
Ammonia is converted into less toxic urea
Urea released into the blood
Urea filtered out by kidneys
Urea passed out in urine
121
Where is there no control over water, ions or urea?
By the lungs or skin
122
How are ions removed from the body in urine?
Ions are taken into the body in food, then absorbed into the blood
If ion content if the body is wrong, the balance between ions and water is wring, so too much or too little water is drawn into the cells by osmosis, damaging the cells
Some ions are lost in sweat, but it’s not regulated so the kidneys maintained the balance of ions in the body
The right amount of ions is reabsorbed into the blood after filtration and the rest is removed from the body in urine
123
How is the amount of water in the body controlled?
The amount we consume and the amount removed by the kidneys in urine
124
What hormone controls the water level in the body and what does it act on?
ADH which acts in the kidney tutblues
125
Where is ADH released from and when?
Released by the pituitary gland when the blood is too concentrated and causes more water to be reabsorbed back into the blood from the kidney tubules
126
Describe the negative feedback for water control?
Water content is too high:
Receptor in brain detects that the water content is too high
Coordination centre in the brain receives the information and coordinates a response
Pituitary gland releases less ADH
Less water is reabsorbed from the kidney tubules
More urine produced
Level is too low:
Receptor in the brain detects that the water content is too low
Coordination centre in the brain receives the information and coordinates a response
Pituitary gland releases more ADH
More water is reabsorbed from the kidney tubules
Little urine produced
127
How do the kidneys maintain the balance of water in the body?
Lack of water- kidneys conserve it by producing low volumes of concentrated urine
Excess water - kidneys produce large volumes of diluted water
128
What control system controls the water content of the body?
Negative feedback
129
What happens when the kidneys don’t work properly?
Waste substances build up in the blood and you lose your ability to control the levels of ions and water in your body, eventually resulting in death
130
How can people with kidney failure be kept alive?
Dialysis treatment - a machine does the job if the kidneys
Kidney transplant - healthy donor kidneys transplanted by surgical procedure
131
Why dies dialysis have to be done regularly?
To keep the concentrations of dissolved substances in the blood at normal levels, and to remove waste substances
132
How does dialysis work?
In a dialysis machine, the persons blood flows between partially permeable membranes surrounded by dialysis fluid
The membrane are permeable to ions and waste substances but not big molecules like proteins
The dialysis fluid has the same concentration of dissolved ions and glucose as healthy blood, so useful dissolved ions and glucose won’t be lost from the blood during dialysis
Only waste substances like urea and excess ions and water diffused across the barrier
133
During dialysis, why does clean blood flow through a bubble trap?
To get rid of any bubbles
134
What de the pros and cons of dialysis treatment?
Pros - keep patient alive, readily available and can be used by patients while waiting for a transplant, no rejection can occur
Cons - regular sessions, each session can take up to 10 hours, unpleasant experience, over the long term the balance of substances becomes more difficult to control, diet has to be strictly regulated, expensive for the NHS, blood clots or infections can occur
135
Outline kidney transplants
Healthy kidneys are usually transplanted from people who have died suddenly
Person who died has to be on the organ donor register or carry an organ donor card
Kidneys can also be transplanted from people who are still alive
136
What are the pros and cons of kidney transplants?
Pros - keep patient alive, cheaper than dialysis, can put an end to the hours patients must spend on dialysis, cure for kidney failure
Cons - rejection can occur, long waiting lists, patient must be on immunosuppressants for the rest of their life to prevent rejection
137
In a dialysis machine, why is it important to constantly pump fresh dialysis fluid through the machine?
To maintain a concentration gradient for diffusion across the membrane
138
In a dialysis machine, why is it important to constantly pump fresh dialysis fluid through the machine?
To maintain a concentration gradient for diffusion across the membrane
139
what is adrenaline?
a hormone produced by the adrenal glands
140
when is adrenaline produced?
during the 'fight or flight' response, when you get stressed, scared or need to exercise
141
what does adrenaline do?
increases heart rate
increases blood pressure
increases blood flow to the muscles increases blood sugar levels by stimulating the liver to break glycogen down into glucose
142
where is thyroxine produced?
in the thyroid gland, which is in the neck
143
what is the function of thyroxine?
it helps with growth and development, but its main role is to control metabolic rate
144
how is the production of thyroxine regulated?
the pituitary gland produces TSH, which stimulates the thyroid gland to produce thyroxine
thyroxine then inhibits the production of TSH from the pituitary gland
145
what happens if thyroxine levels are too low?
the pituitary gland will release TSH, which will stimulate the thyroid gland to produce thyroxine, which brings thyroxine levels in the blood back to normal
146
what happens if thyroxine levels are too high?
the thyroxine will inhibit the pituitary gland from producing TSH. Less TSH means that the thyroid gland won't release as much thyroxine. So thyroxine levels in the blood fall back to normal.
147
what is the control of levels of thyroxine by the hypothalamus and pituitary gland an example of?
negative feedback
148
when focusing on distant objects, what is the shape of the lens?
long and thin
149
short sightedness is caused by the lens being too
long
150
What name is given to the furthest position an object can be from the eye and still be focused clearly?
far point
151
what is the fluid at the front of the eye called?
aqueous humour
152
what do convex lenses do?
Converging (or convex) lenses bring the light rays closer, moving the image location forwards, onto the retina
