The nervous system and the brain...
The nervous system consists of the brain, spinal cord, and paired nerves and receptors (sense organs). The brain and spinal cord are referred to as the central nervoes the us system (CNS). The rest of the nerves in the body are collectivley called the peripheral nervous system.
The nervous system allows organisms to react to their surrounding and coordinate their behaviour.
Information from the receptors passes along neurones (nerve cells) to the brain, which coordinates the response.
The brain cooridinate most of the body's actions. It is the most delicate organ in the human body. It recieves stores and recalls information, and instructs and coordinates actions but sometimes things can go wrong;
- Tumours-develop when cells in the brain divide and grow uncontrollably. The tumour presses against other parts of the brain, resulting in them not working properly.
- Parkinsons Disease- develops when the brain stops producing dopamine, a chemical brain cells use to communicate with each other.This can affect movements of the body.
- Strokes- occur when the brain is starved of oxygen and stops working properly.
- Grand Mal Epilepsy- brain neurones neurones communicate with each other by sending electrical impulses.Sometimes these impulses are random and instructions are uncoordinated to the bosy - causing fits.
...are specially adapted cells that carry electrical signals called impulses. Neurones are elongates (stretched out) to make connections between parts of the body. They have branched endings which allow a single neurone to act on many muscle fibres or connect with many other neurones. There are three types;
- Sensory neurone- these take nerve impulses from the sense organs (receptors) to the central nervous system
- Relay neurones- these pass impulses on from sensory neurones to motor neurones in the CNS
- Motor neurones- take impulses from the CNS to the muscles or glands.
Neurones pass information into and out of the central nervous system and they do not touch each other. The very small gap between them is called a synapse.
1. When an electrical impulse reaches this gap via neurone A a chemical transmitter is released and activates receptors in neurone B. 2.This causes an electrical impulse to be generated in neurone B. 3. The chemical transmitter is the destroyed.
Voluntary Responses- These are actions over which we have complete control- we concioulsy decide to act eg. speaking, walking or picking something up.
Involuntary/Reflex Response- These are responses over which we have no control eg blinking pupil reflex or moving part of your body away from pain.
Reflex arcs and reflex actions...
Sometimes conscious action would be too slow to prevent harm to the body. Reflex action speeds us the response time by missing out the brain.
The spinal cord acts as the coordinator and passes impulses directly from a sensory neurone to a motor neurone via a relay neurone which bypasses the brain.
For example the Iris Reflex- the human eye can increase and decrease in size in order to regulate the amount of light entering it.
If you were in a country lane and a bird swooped above your head you would duck- this is an example of relex actions.
Blood have four components;
Red Blood cells-have no nucleus so can be packed with haemoglobin. The shape provides bigger surface area. Haemoblobin combines easily with oxygen. In the lungs where theres lots of oxygen, haemoglobin + oxygen -> oxyhaemoblobin. The word equation is visa versa for tissues where oxygen is being used up. This reversible reaction ensures oxygen is transported to where it is needed
Plasma- is a straw coloured liquid consisting mainly of water. It transports; carbon dioxide from the organs to the lungs. Soluble products of digestions from the small intestine. Urea from the liver to the kidneys. Chemical messengers called hormones. Water to and from various parts of the the body.
White blood cells- part of the body's immune system: they either engulf bacteria or produce antibodies.
Hormones and Coordination...
Hormones are chemical messengers produced by endocrine glands. Hormones coordinate and control the way in which parts of the body function. Hormones are transported to their target organs (an organ which has s hormone that has a specific effect) or target cells through the bloodstream eg the pancreas produces insulin.
Oestrogen- causes the lining of the uterus to thiken during the early part of the menstrual cycle (it repairs after a period)
Progesterone- is produced after an egg is released. It preserves and mantains the uterus wall during the middle part of the cycle.
Fertillisation- if it occurs and the woman become pregnant then the ovary continues to produce progesterone until the placenta is formed. The placenta then produces progesterone for the remainder of the pregnancy, maintaning the uterus and preventing further ovulation.
Manufactured oestrogen and progesterone can be used in two ways;
As Contraception-prevents the development of eggs
To treat Female Infertility- raise the bodys oestrogen levels and helps trigger ovulation
IVF - is used if a couple cannot concieve naturally.Some questions asked are;
what should happen to the spare embryos?
Older women can still have a baby and be a mother in their 70s.
Is it right to interfere with a natural process?
It is expensive costing between £5000 and £6000 for each attempt.
Producing Human Insulin..
Human Insulin can be produced by Genetic Engineering.
The gene for insulin production is cut out of the human DNA and inserted into a ring of bacterial DNA. The bacterial DNA is then allowed to reproduce.There are then millions of them, each programmed to produce inslulin.
This method allows insulin to be roduced in large quantites and made very cheaply.
Bacteria-a singe cell with no nucleus
Effector- the part of the body that produces a response to a stimulu eg muscle or gland.