Homestasis and response

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  • Created by: leo1223
  • Created on: 28-05-18 11:26
What is meant by homeostasis?
Homestasis is the regulation of the internal conditions of a cell or an organism in response to internal or external changes
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Why is homeostasis important?
Homestasis is important because it keeps conditions constant for enzymes and cell functions
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What does homeostasis control?
Blood glucose concentration, body temperature, water and ion levels
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Name 2 control systems used by homeostasis
Responses using nerves and chemical responses using hormones
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What is a control system?
A control system is a system that has receptors, a coordination centre and effectors, an example of a control system would be the CNS
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What is a receptor?
A receptor are cells which detect stimuli (changes in the internal or external environment)
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What is a coordination centre? (include examples)
Coordination centres are an organ or tissue that receives and processes information received from the receptors. The brain, spinal cord and pancreas are all coordination centres
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Explain what negative feedback?
When a receptor detects a change in a stimulus, the coordination centre compares the stimulus to the set point, a effector then produces a response to correct the difference between the stimulus and the set point. This is know as negative feedback
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Explain what the thermoregulatory centre in the brain does?
It monitors and controls the body temperature, it contains receptors that monitor temperature of blood flowing through brain, receives impulses from temperature receptors in skin
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Explain what the thermoregulatory centre does when body temperature is too high?
When the body temperature is too high, blood vessels widen, directing more blood to the surface of the skin, this is know as vasodilation, more sweat is produced from the effectors, both of these processes are caused by the effectors
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Explain what the thermoregulatory centre does when body temperature is too low?
When the body temperature is too low, blood vessels narrow, directing blood away from the surface of the skin, this is know as vasoconstriction, skeletal muscles uncontrollably contract and relax quickly, which causes the body shiver
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What does the central nervous system do?
The central nervous system enables humans to react to their surroundings and coordinate their behaviour, i.e. the CNS coordinates the response of effectors, muscles contracting or glands secreting hormones
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What are reflex actions?
Reflex actions are automatic actions performed to protect the body, which do not involve the conscious part of the brain
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Explain how reflex actions are triggered?
The pain stimulus is detected by receptors, impulses from the receptor pass along a sensory neurone to CNS, an impulse then passes through a relay neurone, a motor neuronee carries an impulse to the effector, the effector (muscle) responds
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What are synapses?
Synapses are the gaps between each neurone where communication takes place , When an electrical impulse reaches a synapse, a chemical is released and diffuses across the gap, this causes an electrical impulse to generate in the second neurone
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Name the three main regions of the brain
Cerebral cortex, cerebellum and the medulla
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How have neuroscientists been able to map out specific regions of the brain?
Neuroscientists have been able to map the regions of the brain to particular functions by: studying patients with brain damage, electrically stimulating different parts of the brain, using MRI scanning techniques
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What is the retina
The retina contains receptor cells which are sensitive to light
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What is the optic nerve?
The optic nerve carries impulses from the retina to the brain
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What is the sclera?
The sclera forms a tough outer layer at the back of the eye, the cornea is a transparent region at the front of the eye which is part of the sclera
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What is the cornea?
The cornea is part of the sclera, it is located at the front of the eye and is transparent
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What is the iris?
The iris is the part of the eye which controls the size of the pupils and the amount of light reaching the retina
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What are the ciliary muscles and suspensory ligaments?
The ciliary muscles and suspensory ligaments are able to change the shape of the lens to focus the light on near or distant objects
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What is the process of accommodation?
Accommodation is the process of changing the shape of the lens to focus on near or distant
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How does the eye focus on a near object?
To focus on a near object the ciliary muscles contract, the suspensory ligaments are loosened, which causes the lens to become thicker and refracts light rays strongly
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How does the eye focus on a far away object?
To focus on a distant object the ciliary muscles relax, the suspensory ligaments are pulled tight, which causes the lens to become thinner and only slightly refracts light rays
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What is myopia and what lens fixes this defect?
Myopia is short sightedness, a convex lens can fix this defect
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What is hyperopia and lens fixes this defect?
Hyperopia is long sightedness, a concave lens can fix this defect
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What is the endocrine system?
The endocrine system is made up of glands that secrete hormones directly into the bloodstream
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What are hormones?
Hormones are chemical messengers that are carried in the blood to a target organ where they produce an effect
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How do the effects of hormones compare to the effects of the nervous system?
Compared with the effect of the nervous system, the effects of hormones are slower and act for longer
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What is the pituitary gland also know as?
The 'master gland'
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What does the pituitary gland do?
The pituitary gland secretes serval hormones in response to body conditions, some of these hormones act on other glands to stimulate other hormone to be released and bring about effects
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Describe what Adrenaline is and its effects?
Adrenaline is a hormone produced in the adrenal glands in times of fear and stress, it increases the heart rate which boosts the rate at which oxygen and glucose is delivered to the brain and the muscles, creates the 'flight or fight' response
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Describe what Thyroxine is and its effects?
Thyroxine is a hormone produced in the thyroid gland, it increases the metabolic rate, it also controls the rate at which animals and humans grow and develop, it is controlled by negative feedback
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What gland controls and monitors the blood glucose concentration?
Pancreas
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What happens when the blood glucose concentration is too high?
When the blood glucose concentration is too high the pancreas releases more of the hormone insulin, insulin causes glucose to move from the blood into the cells, in the liver and muscle cells, excess glucose is converted in to glycogen for storage
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What happens when the blood glucose concentration is too low?
When the blood glucose concentration is too low the pancreas releases the hormone; glucagon, glucagon stimulates glycogen to be converted into glucose and released into the blood, this is an example of negative feedback
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Describe what type 1 diabetes is caused by, its effects on the body and possible treatments?
Type 1 diabetes is a disorder that is caused by the pancreas failing to produce sufficient insulin which results in uncontrolled high blood glucose levels, it can be treated with insulin injections
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Describe what type 2 diabetes is caused by, its effects on the body and possible treatments?
Type 2 diabetes is a disorder that is caused by the body cells no longer responding to insulin, obesity is a risk factor, possible treatments include regular exercise paired with a carbohydrate-controlled diet
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How can water leave the body?
Water can leave the lungs from breathing as water vapour, from the skin in sweat and in urine
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What happens to body cells when the concentration of blood in the body changes?
Body cells will either lose or gain too much water by osmosis when the concentration of blood is changed
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What gland regulates the balance of water and ions in the body?
The kidneys
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What is urea used for?
Urea is excreted to get rid of waste products that are produced in the liver such as ammonia, which is formed by the breakdown of proteins containing nitrogen
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Describe how amino acids are formed?
The digestion of proteins from food results in excess amino acids. In the liver these amino acids are converted into ammonia in a process called deamination. Ammonia is toxic, it is then converted into urea and sent to the kidneys for safe excretion
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Describe the process whereby kidneys produce urine?
Kidneys produce urine by filtering the blood, selective reabsorption of useful substances such as glucose and some ions and water occurs, finally this leaves urea and excess water and ions to form urine
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Where does the process of blood filtration, selective reabsorption and urine production take place?
Millions of small tubes in the kidneys know as tubules are where the process of blood filtration, selective reabsorption and urine production takes place
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What hormone controls the water level in the body?
ADH / Anti-diuretic hormone
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Describe what happens when the blood is too concentrated?
When the blood is too concentrated, ADH is released by the pituitary gland, it passes in the blood, to the kidney tubules where it causes more water to be reabsorbed back into the blood. This is an example of negative feedback
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How can people who suffer from kidney failure be treated?
People who suffer from kidney failure can be treated by either an organ transplant or kidney dialysis
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Explain what a dialysis machine does?
The dialysis machine takes over the role of the kidneys, as it removes waste products from the blood. The dialysis machine must be used three times a week for serval hours in order to treat the patient suffering kidney failure
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Describe what happens when the blood is too dilute?
When the blood is too dilute, ADH is not released by the pituitary gland. The lack of the hormone in the kidney tubules causes less water to be reabsorbed back into the blood. This is an example of negative feedback
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Describe the process of ovulation?
Ovulation is where the matured eggs are released, this process starts during puberty for young females and is caused by the release of the hormone; LH
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Where is the hormone; Oestrogen secreted from and what are it's functions?
Oestrogen is secreted by the ovaries in a female, it inhibits FSH release and stimulates LH release, it also makes the lining of the uterus grow again after menstruation
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Where is the hormone; FSH secreted from and what are it's functions?
FSH is secreted by the pituitary gland, it causes eggs to mature in the ovaries in the first part of the menstrual cycle, it also stimulates the ovaries to produce oestrogen
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Where is the hormone; LH secreted from and what are it's functions?
LH is secreted by the pituitary gland, it stimulates the release of the egg from the ovary also know as ovulation
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Where is the hormone; Progesterone secreted from and what are it's functions?
Progesterone is secreted by an empty follicle in the ovaries, it maintains the lining of the uterus during the second half of the cycle, it also inhibits both FSH and LH release
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Where is the hormone; Testosterone secreted from and what are it's functions?
Testosterone is secreted by the testes and stimulates sperm production
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Explain how oral contraceptives reduce fertility?
Oral contraceptives are hormonal methods. An example of an oral contraceptive is the pill, which contains oestrogen and progesterone, which inhibit FSH production so that no eggs are released
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Explain how injections, implants or patches of progesterone reduce fertility?
Injection, implants or patches of progesterone are hormonal methods. These methods of slowly releasing progesterone into the body stops the release of eggs for a number of months or years
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Explain how barrier methods reduce fertility?
Barrier methods such as condoms and diaphragms are non-hormonal methods. These methods prevent sperm from reaching an egg
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Explain how intrauterine devices reduce fertility?
Intrauterine devices are a non-hormonal method, these devices prevent embryos from implanting in the uterus
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Explain how spermicidal creams reduce fertility?
Spermicidal creams are a non-hormonal method, which disable or kill sperm cells
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Explain how surgical methods reduce fertility?
Surgical methods are a non-hormonal method, male and female sterilisation, such as the cutting of the sperm ducts or tying of the fallopian tubes, prevent the sperm from ever reaching a egg
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How can women with low levels of FSH increase their fertility?
Doctors may prescribe an drug; which contains FSH and LH, to a woman if her own level of FSH is too low to stimulate eggs to mature, the increase in FSH and LH will increase the likelihood that eggs have matured and therefore increase fertility
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Describe the process of IVF?
The IVF treatment involves: giving a woman FSH and LH to stimulate growth of many eggs, collecting the eggs from a woman, fertilising the eggs with sperm from the farther in the lab, inserting one or two embryos into woman's uterus
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Name 3 disadvantages of IVF
IVF causes emotional and physical stress for the woman and father, the success rates are not high, IVF can lead to multiple births which are a risk for both the babies and the mother
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Name 3 response plants make to external changes in the environment
Roots and shoots growing towards or away from a particular stimulus, plants flowering at a particular time and ripening of fruits
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What do plants shoots grow towards/away from? What are these responses know as?
Plant shoots grow towards light, making them positively phototropic, plant shoots grow away from gravity, making them negatively gravitropic
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What do plants roots grow towards/away from? What are these responses know as?
Plant roots grow towards gravity, making them positively gravitropic, plant roots grow away from light, making them negatively phototropic
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What is a 'tropism'?
When a part of a plant responds by growing in a particular direction, it is called a tropism
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Name two tropisms
Gravitropism and phototropism
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What are tropisms controlled by?
Tropisms are controlled by a ground of plant hormones called auxins
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Describe the way in which a plant responds to light?
As more light reaches one side of the shoot, more auxin is sent down the shaded side of the shoot, this results in cells on the shaded side elongating more, the shoot therefore grows towards the light. Making the shoots positively phototropic
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Describe how auxins work in the roots of a plant?
In the roots, auxin moves to the bottom of the root and causes less elongation, which causes the root to grow downwards. Making the root positively gravitropic
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What are gibberellins?
Gibberellins are another group of plant hormones and are important in initiating seed germination
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What do plants use ethene gas for?
Ethene is a gas which is also a plant hormone. It controls cell division and the ripening of fruits
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Why are auxins used as weed killers?
Auxins are used as weed killers because they make the weeds grow so rapidly that they use up all their food reserves and die
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Why are auxins used as rooting powders?
Auxins are used as rooting powders because they make cuttings produce roots when they are planted
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What are auxins used in to promote growth?
Auxins can be used in tissue cultures to promote growth
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Why is ethene used in the food industry?
Ethene is used in the food industry to control the ripening of fruit during storage and transport
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Name 4 uses of gibberellins
End seed dormancy, promoting the germination of seeds, promote flowering so that plants can flower when there is the most demand, increase fruit size
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Why is fruit picked unripe before being transported?
Unripened fruit can be transported over long distances without damage. It can then be ripened using ethene when it reaches its destination
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Why is meant by auxin weedkillers being 'selective'?
Auxin weedkillers are selective meaning that they can be used on lawns to kill weeds but not the grass, making them extremely useful for farming
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Card 4

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Card 5

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