The regulation of internal conditions in a cell or organism is response to internal and external changes
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Why is homeostasis important?
It keeps conditions constant for enzyme activity and cell functions
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What can homeostasis include the control of?
Blood glucose
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What might the control systems of homeostasis involve?
Responses using nerves
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What do all control systems involve?
Receptors
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What is a receptor?
Cells that detect stimuli (a change in environment)
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What are coordination centres?
Places such as the brain
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What are effectors?
Muscles or glands which bring about responses to restore optimum levels
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What is negative feedback?
A receptor senses a change in stimulus
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What is the ideal temperature for the human body?
37 degrees
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Why is the optimum temperature for the human body 37 degrees?
Gives optimum temperature for enzymes to work
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What does the thermoregulatory centre in the brain do?
Monitors and controls body temperature
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What does the thermoregulatory centre in the brain use to get imformation from?
It has receptors that monitor the temperature of the blood flowing through the brain and receives impulses from temperature receptors in the skin
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What happens if body temperature is too high?
Blood vessels widen so more blood goes to the surface of the skin (Vasodilation)
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What happens if body temperature is too low?
Blood vessels marrow so blood goes away from surface of skin (vasoconstriction)
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What does the nervous system allow humans to do?
React with their surroundings and coordinate behaviour
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What is the pathway for a normal nerve impulse?
Receptor to CNS to effector
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What is the CNS?
The spinal cord and brain
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What is a reflex action?
Automatic and rapid so they protect the body. They don't involve the conscious part of the brain
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What is the reflex pathway?
Receptors to sensory neurone to CNS to relay neurone to effector
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What is the gap between neurones called?
Synapse
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What type of impulse goes through a neurone?
An electrical impulse
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How to neurones send impulses across synapses?
A chemical messenger is released when the impulse reaches the end of the neurone which travels across the synapse and induces an impulse in the next neurone
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What is the brain made of?
Billions of interconnected neurones and has different regions that carry out different functions
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What are the three main regions of the brain?
Cerebral cortex
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What does the medulla do?
controls heartbeat and breathing
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What does the cerebellum do?
Coordinates movement and balance
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What does the cerebral cortex do?
Responsible for consciousness
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How have neuroscientists been able to map the regions of the brain to particular functions?
By studying patients with brain damage
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What is the retina?
Contains receptor cells that are sensitive to light
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What is the function of the optic nerve?
Carries impulses from the retina to the brain
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What is the sclera?
Forms a tough outer layer
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What is the function of the iris?
Controls the size of the pupil
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What is the function of the pupil?
To control the amount of light that can enter the eye
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What is the function of the ciliary muscles and suspensory ligaments?
To change the shape of the lens to allow light to focus on the retina
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How does the eye focus on a near object?
The ciliary muscles contract
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How does the eye focus on distant objects?
The ciliary muscles relax
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What is myopia?
Near sightedness
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What is hyperopia?
Far sightedness
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How are sight defects corrected?
Spectacle lenses
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What is the endocrine system?
Include glands which secrete hormones into the bloodstream
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What are hormones?
Chemical messengers that are carries in the blood to a target organ where they produce an effect
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How do the effect of the nervous system and hormones compare?
Nervous system is faster
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What is the pituitary gland?
The 'master gland' that secretes hormones. These can have an effect on other glands to stimulate other hormones to be released
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Where is the pituitary gland?
Near the brain
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Where is the thyroid gland?
In your throat
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Where is the pancreas?
In your belly
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Where are the ovaries and testes?
Reproductive systems
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Where are the adrenal glands
Just above your kidneys
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What does adrenaline do?
Increases heart rate to increase delivery of oxygen and glucose to brain and muscles. It prepares the body for 'fight or flight'
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Where and when is adrenaline produced?
In the adrenal glands in time of stress or fear
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Where is thyroxine produced?
In the thyroid glands
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What does thyroxine do?
Increases the metabolic rate
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What is thyroxine controlled by?
Negative feedback
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What organ controls blood glucose?
The pancreas
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What happens if blood glucose concentration is too high?
The pancreas releases insulin which causes glucose to move into muscle cells and the liver where it is stored and glycogen
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What happens if the blood concentration is too low?
The pancreas releases glucagon which causes the release of glycogen from the liver and muscles back into glucose in the blood stream
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What is type one diabetes?
A disease that causes the pancreas to produce insufficient insulin resulting in uncontrolled high blood glucose levels
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How is type one diabetes treated?
Insulin injections
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What is type two diabetes?
The body cells no longer respond to insulin
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What is a risk factor for type two diabetes?
Obesity
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How is type two diabetes treated?
With carbohydrate-controlled diet and regular exercise
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How does water leave the body?
From the lungs during breathing
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What happens to water if the blood changes concentration?
The body cells will lose or gain too much water by osmosis
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What organ regulates the balance of water and ions?
The kidneys
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What is urea?
A waste product produced by the breakdown of proteins
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How is urea produced?
The digestion of proteins from foods results in excess amino acids. In the liver these excess amino acids are converted into ammonia. Ammonia is toxic so it is immediately converted to urea and sent to the kidneys for excretion
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How do the kidneys produce urine?
Filtering the blood
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Where does the process of producing urine take place in the kidneys?
Tubules
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What hormone controls water level in the body?
ADH- anti diuretic hormone
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Where is ADH released from and when?
The pituitary gland when blood is too concentrated
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How does ADH decrease the concentration of blood?
It passes into the kidneys through the blood stream where it causes more water to be reabsorbed back into the blood
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What are the two options for treatment for kidney failure?
Dialysis and transplant
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What are the advantages of kidney dialysis?
Don't have to wait for donor
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What are the disadvantages of kidney dialysis?
Restrictive diet- low protein and salt intake
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What are the advantages of a kidney transplant?
Patients do not have to monitor what they eat and drink
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What are the disadvantages of kidney transplant?
Must take immune suppressant drugs
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Which gland secretes oestrogen?
The ovaries
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What is the function of oestrogen in the menstrual cycle?
Inhibits FSH release
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Which gland secretes FSH?
The pituitary gland
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What is the function of FSH in the menstrual cycle?
Causes the eggs to mature
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Which gland secrets LH?
The pituitary gland
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What is the function of LH in the menstrual cycle?
Stimulates the release of the egg from the ovary (Ovulation)
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Where is progesterone secreted from?
The empty follicle in the ovary after ovulation
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What is the function of progesterone in the menstrual cycle?
Maintains the lining of the uterus during the second half of the cycle
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What is the main male hormone?
Testosterone
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Which gland secretes testosterone in males?
The testes
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What are the hormonal methods of contraception?
Oral contraceptives
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How does the oral contraceptive (combined pill) work?
Contains oestrogen and progesterone which inhibit FSH so no eggs are released
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How do hormonal contraceptives such as the implant work?
They slowly release progesterone to stop the release of eggs for a number of month or years
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What are the non-hormonal methods of contraception?
Barrier methods (Condoms
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How do barrier methods of contraception work?
Stop the sperm reaching the egg
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How do intrauterine devices of contraception work?
Prevent embryos from implanting in the uterus
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How do spermicidal creams work?
They kill or disable sperm
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What is in a fertility drug given to a woman?
FSH and LH
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What are the stages of IVF?
Giving a woman FSH and LH to stimulate the growth of many eggs
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What are the disadvantages of IVF?
It is emotionally and physically stressful
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How do the responses of plants compare to that of animals?
Plants' responses are much slower
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What can plant responses include?
Roots and shoots growing towards or away from a stimulus
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What is a tropism?
When part of a plant starts to grow in a certain direction due to response to a stimuli