Describe the role of the human nervous system.
The human nervous system enables humans to react to their surroundings and to coordinate their behaviour.
What is the central nervous system?
The central nervous system comprises of:
- the brain
- the spinal cord
How is information from receptors passed through the nervous system?
The information is passed through the nervous system as electrical impulses.
Describe the pathway through the nervous system, starting at the receptor.
The pathway is as follows:
stimulus --> Receptor --> Coordinator --> Effector --> Response
What is the role of receptors?
Receptors detect a change in the environment.
What is the role of an effector?
An effector brings about a response. Effectors can be muscles (eg hand muscles contracting to move a hand away from a hot plate) or glands secreting hormones (eg the pancreas releasing insulin)
What is the role of a sensory neurone?
A sensory neurone carries signals from the receptors to the spinal cord or brain.
What is the role of a relay neurone?
A relay neurone carries messages from one part of the CNS to another
What is the role of a motor neurone?
Motor neurones carry signals from the CNS to effectors.
What is a reflex action?
A reflex action is automatic and rapid. It does not involve the conscious part of the brain.
How are electrical impulses carried between neurones?
Between neurones are junctions called synapses. electrical impulses are converted in to chemical signals as neurotransmitter. The neurotransmitter diffuses across the synapse where it is the converted back in to an electrical impulse.
Describe the role and structure of the brain.
The brain controls complex behaviour. It is made of billions of interconnected neurones and has different regions that carry out different functions.
What is the role of the cerebral cortex?
The cerebral cortex is concerned with:
What is the role of the cerebellum?
The cerebellum controls muscular activity and balance.
What is the role of the medulla?
The medulla controls unconscious activities such as controlling heartbeat, breathing and the movements of the gut.
Explain why it is difficult to investigate and treat brain disorders.
Many of the process that take place in the brain involve many different neurones in different areas. There is also a range of different chemicals released in the synapses.
Drugs do not always reach the brain through the membranes that surround it.
Surgery is difficult because the brain is not fully understood and it is easy to cause unintended damage.
Explain how neuroscientists have been able to map the regions of the brain with particular functions.
Neuroscientists have been able to study patients with brain damage. They have also been able to eectrically stimulate different parts of the brain and use MRI scanning techniques.
What is the role of the retina?
The retina is a light sensitive layer that contains receptors which are sensitive to light intensity and colour.
Describe the structure and role of the optic nerve?
The optic nerve is a bundle of sensory neurones at back of eye. It carries impulses from the eye to the brain.
Describe the structure and function of the sclera.
The sclera is the white outer layer of the eye. It is relatively strong and tough so the eyeball does not get damaged.
Describe the structure and function of the cornea.
The cornea is a transparent area at the front of the eyeball. It is convex and transparent. The cornea refracts light - bends it as it enters the eye.
Describe the structure and function of the iris.
The iris is pigmented - decides the colour of your eyes - so light cannot pass through.
Its muscles contract and relax to alter the size of its central hole or pupil which controls how much light enters the pupil.
Describe the structure and function of the ciliary muscles.
The ciliary muscles change the shape of the lens so that the image always comes to a sharp focus on the retina.
Describe the structure and function of the lens.
The lens is a ransparent, bi-convex, flexible disc behind the iris attached by the suspensory ligaments to the ciliary muscles.
The lens focuses light onto the retina.
Describe the function of the suspensory ligaments.
The suspensory ligament
What is accomodation?
Accomodation is the process of changing the shape of the lens to focus on near or distant objects.
Explain what happens to the ciliary muscles, suspensory ligaments and the lens in order to focus on a near object.
In order to focus on a near object:
- the ciliary muscles contract
- the suspensory ligaments loosen
- the lens becomes thicker and refracts light rays strongly.
Explain what happens to the ciliary muscles, suspensory ligaments and the lens in order to focus on a distant object.
In order to focus on a near object:
- the ciliary muscles relax
- the suspensory ligaments tighten
- the lens becomes thinner and only slightly refracts light rays.
What is myopia?
Myopia is also known as short sightedness. People with myopia can see close objects with clear focus but distant objects look blurred.
This may be a result of a lens that is too curved or a long eyeball. The light is focused infront of the retina.
What is hyperopia?
Hyperopia is also known as long-sightedness. People with hyperopia can focus clearly on distant objects but close objects appear blurred.
This may be a result of a lens that is too flat and thin or a short eyeball. This means that the lens cannot refract the light rays stongly enough and light is focused behind the retina.
Describe how myopia can be treated.
Myopia can be treated by wearing glasses with a concave lens that spread out the light rays from distant objects before they reach the eye.
Describe how hyperopia can be treated.
Hyperopia can be treated by wearing glasses with a convex lens. This brings the light rays together before they reach the eye.
Describe the role of a contact lens in treating myopia and hyperopia,
Contact lenses are placed on the surface of the eye. They cannot be seen and make playing sport and general activities easier.
Contact lenses may need to be removed over night and sterilised to prevent infection.
Describe the role of laser surgery in treating myopia and hyperopia.
To treat myopia, lasers are used to reduce the thickness of the cornea so it refracts the light less strongly.
To treat hyperopia lasers are used to change the curve of the cornea.
Laser surgery can only be performed in adults once the eyes have stopped growing.
Describe how replacement lenses can be used to treat myopia and hyperopia.
The addition of another lens inside the eye can be used to treat both conditions.
A permanent contact lens can be implanted alongside the natural lens or the faulty lens can be replaced.
Risks include damage to the retina, infections and the development of cataracts.
What part of the brain monitors and controls body temperature?
Body temperature is monitored and controlled by the thermoregulatory centre in the hypothalamus.
Explain why body temperature needs to stay at 37 degrees.
Body temperature needs to remain at 37 degrees as this is the temperature at which our enzymes work best.
Describe and explain the mechanisms involved in lowering body temperature.
If our body temperature becomes too high:
- Vasodilation - more blood can flow through the capillaries and so more heat can be transferred to the surroundings by radiation
- Sweat is produced from sweat glands - sweat evaporates from the skin which transfers heat energy to the surroundings
Describe and explain the mechanisms involved in increasing body temperature.
In order to increase core body temperature:
- Vasoconstriction - blood flow through the capillaries is reduced and so energy transfer through radiation is reduced
- Sweating stops - less water evaporates and so less heat energy is transferred away from the body
- Skeletal muscles contract - muscle contractions need respiration which is an exothermic reaction.
Describe the structure and function of the human endocrine system.
The human endocrine system is composed of glands which secrete hormones directly in to the blood stream.
The blood carries the hormone to a target organ where it produces an effect.
Give 2 differences between the effects of the nervous system and endocrone system.
Compared to the nervous system the effects of the endocrine system are slower but last for longer.
Which gland of the endocrine system is known as the "Master gland".
The pituitary gland is known as the master gland.
It secretes several hormones into the blood in repsonse to body conditions. These hormones act on other glands to stimulate other hormones to be released which bring about effects.
Which organ monitors and controls blood glucose concentration?
Blood glucose concentration is monitored and controlled by the pancreas.
What is the name of the hormone that controld blood glucose concentration?
Insulin controls blood glucose concentration.
Explain how insulin controls blood glucose levels in the body.
Insulin causes glucose to move from the blood into the cells. In liver and muscle cells excess glucose is converted to glycogen for storage.
What causes Type 1 diabetes?
Type 1 diabetes is caused when the pancreas fails to produce enough insulin.
Describe how type 1 diabetes can be treated.
Type 1 diabetes can be treated with insulin injections.
What causes Type 2 diabetes?
Type 2 diabetes is caused when body cells stop responding to insulin.
Obesity is a risk factor.
Describe how type 2 diabetes can be treated.
Type 2 diabetes can be treated by eating a carbohydrate controlled diet and having an exercise regime.
Describe what happens when blood glucose concentration falls too low.
If the blood glucose concentration is too low, the pancreas produces the hormone glucagon thay causes glycogen to be converted in to glucose and released into the blood.
Give three ways in which excess water is removed from the body.
Excess water is removed from the body:
- Via the lungs during exhalation
- From the skin as sweat
- By the kidneys in urine
Give 2 ways in which excess ions and urea are removed from the body.
Excess ions and urea are removed from the body...
- from the skin as sweat
- from the kidneys in the urine
Describe how protein from our diet is removed from the body.
The digestion of proteins from the diet results in excess amino acids which need to be excreted safely.
In the liver these amino acids are deaminated to form ammonia. Ammonia is toxic
and so it is immediately converted to urea for safe excretion.
Describe the function of kidneys in maintaining ion and water balance in the body.
The kidneys produce urine by filtration of the blood and selective reabsorption of useful substances such as glucose, some ions and water.
Describe the effect of ADH on the permeability of the kidney tubules.
ADH is released by the pituitary gland when the blood is too concentrated (not enough water). ADH causes more water to be reabsorbed back into the blood from the kidney tubules.
Describe 2 treatments for kidney failure.
Kidney failure may be treated by:
- Kidney transplant
Describe how dialysis can be used to treat kidney failure.
A dialysis machine "cleans" blood. The patients blood leaves their body and flows between partially permeable membranes. On the other side of these membranes is dialysis fluid which has the same concentration of useful substances as the blood of a healthy person so there is no diffusion of useful substances. The dialysis fluid contains no urea and so there is a steep concentration gradient meaning it will diffuse out of the blood.
It is vital the the pateients lose the excess urea and mineral ions that have built up in the blood but do not lose any useful substances such as glucose.
Where is oestrogen produced?
Oestrogen is produced in the ovaries.
Describe the process of ovulation.
During ovulation, an egg is released from an ovary approximately every 28 days.
Where is testosterone produced?
Testosterone is produced by the testes.
What is the role of testosterone?
Testosterone stimulates sperm production.
Describe the role of Follicle stimulating hormone (FSH) in the menstrual cycle.
FSH causes the maturation of an egg in the ovary.
Describe the role of Luteinising hormone (LH) in the mesntrual cycle.
Luteinising hormone stimulates the release of the egg.
Describe the role of Oestrogen and Progesterone in the menstrual cycle.
Oestrogen and progesterone maintain the uterus lining
Where is FSH produced?
FSH is produced by the pituitary gland.
Describe the interaction between FSH and Oestrogen.
FSH stimulates the ovaries to produce oestrogen which then inhibits FSH.
Describe the interaction between oestrogen and LH.
Oestrogen stimulates the release of LH.
What effect does progesterone have on LH and FSH?
Progesterone inhibits LH and FSH.
Name three hormonal methods of contraception.
Hormonal methds of contraception include:
- Oral contraceptives
- Skin Patch
- Intrauterine device
Name three non hormonal methods of contraception
Non hormonal methods of contraception include:
- Barrier methods such as condoms and diaphragms
- Spermicidal agents
- Abstaining from intercourse when an egg may be in the oviduct
- Surgical methods of sterilisation
Explain how oral contrceptives may be used as a method of contaception.
Oral contraceptives contain hormones to inhibit FSH production so no eggs mature.
Explain how injections, implants and skin patches may be used as a method of contaception.
Injections, implants and skin patches slowly release progesterone which inhibits the maturation and release of eggs.
Explain how barrier methods may be used as a method of contaception.
Barrier methods prevent the sperm reaching an egg and so fertilisation cannot take place.
Explain how intrauterine devices may be used as a method of contaception.
Intrauterine devices prevent the implantation of an embryo in the lining of the womb or may release hormones.
Describe the process of In Vitro Fertilisation (IVF)
In Vitro Fertilisation (IVF) treatment.
• IVF involves giving a mother FSH and LH to stimulate the
maturation of several eggs.
• The eggs are collected from the mother and fertilised by sperm
from the father in the laboratory.
• The fertilised eggs develop into embryos.
• At the stage when they are tiny balls of cells, one or two
embryos are inserted into the mother's uterus (womb).
Describe the disadvantages of fertility treatment.
Although fertility treatments such as IVF gives infertile couples the oportunity to become parents there are disadvantages:
- it is very emotionally and physically stressful
- the success rates are not high
- It can lead to multiple births which are a risk to both the babies and the mother.
- It is expensive (for both society and individuals)
- Ethical issues regarding frozen embryos if the mother dies or the parents split up
Describe the role of thyroxine in the body.
Thyroxine controls metabolic rates in the body such as how quickly substances are broken down and built up and how much oxygen your tissues use. It also plays an important part in growth and development.
Describe the role of adrenaline.
Adrenaline is produced by the adrenal glands in times of fear or stress. It increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for ‘flight or fight’.
Describe the role of negative feedback.
Negative feedback systems work to maintain a steady state. If a factor in the internal environment increases or decreases, mechanisms take place to restore the original level.
What is the name given to a plant response to light?
A plants response to light is called a phototropism
What is the name given to a plants response to gravity.
A plants response to gravity is called a geotropism or gravitropism
What is the name of the hormone that controls growth in plants?
The hormone auxin controls growth in plants.
Explain how auxin controls phototropism in plants.
Auxin is broken down by sunlight and so concentrates in the unlit side of the shoot. The cells on the unlit side of the shoot elongate and grow causing the shoot to bend towards the light.
Explain how auxin controls gravitropism in shoots and roots.
Auxin makes shoot cells grow but inhibits growth in root cells.
Auxin causes unequal growth of cells on one side which causes the shoots and roots to bend
What is the role of gibberellins in plants.
Gibberellins are important in initiating seed germination.
What is the role of ethene in plants?
Ethene controls cell division and ripening of fruits.
Describe how auxins can be used in agriculture and horticulture.
Auxins are used:
• as weed killers
• as rooting powders
• for promoting growth in tissue culture.
Describe how ethene can be used in agriculture and horticulture.
Ethene is used in the food industry to control ripening of fruit during storage and transport.
Describe how gibberellins can be used in agriculture and horticulture.
Gibberellins can be used to:
• end seed dormancy
• promote flowering
• increase fruit size.