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COORDINATION - Coggle Diagram

- - - - Nerves are made of groups of neurons. Neurons are special cells that transmit electrical signals containing information. The electrical signals are called impulses.
        Neurons have special characteristics that allow them to do this:
        
        Cell body: the cell body contains all the usual parts of a cell, like the nucleus.
        
        Dendrites:It connect to other neurons so that impulses can pass from the cell to cell. The have many branches so they can make lots of connections.
        
        Axon: This part is long and thin, like a cable. The impulse can travel long distances along the axon very quickly.
        
        Myelin sheath: It sheath surrounds and protects the axon. It helps the impulse so travel faster.
    - - The central nervous system consists of the brain and the spinal cord. Neurons within the brain or spinal cord are called relay neurons. The brain processes the information it receives from impulses, decides what to do, and the sends out instructions. Each part of the brain has a different job:
        
        The cerebrum is the dome-shaped part of the brain.
        
        The sensory areas receive information from the sense organs - they give us sensations like smell or hearing.
        
        The motor area controls our muscles.
        
        The association areas are used for thinking and memory.
        
        The brain stem controls unconscious actions like breathing and our heart beat.
        
        The cerebellum helps to control our balance.
        
        The spinal cord consists of millions of nerve fibres. It goes from the brain stem down the middle of the back. It is the main route for information between the brain and the peripheral nervous system. Many reflexes are controlled by the spinal cord.
- - - - Hormones only travel at the same speed that blood flows around the body, and they act slowly (taking at least a few seconds, and often much longer). They therefore can't be used for things that need a very quick response. However, their effects are often long-lasting. They are used for:
        
        controlling gradual changes, like growth and sexual development.
        
        regulating the level of substances in the body.
      - The hypothalamus is a part of the brain. It receives messages from receptors and monitors conditions such as temperature, hunger and thirst. It controls the production of hormones in the other glands, including the pituitary gland.
        
        The pituitary gland produces many hormones, including:
        
        growth hormone (controls growth)
        
        hormones that control when eggs are released from the ovaries
        
        anti-diuretic hormone (controls the amount of water in the blood)
        
        The thyroid gland produces thyroxine, which controls the rate of metabolism.
        
        The adrenal glands are on top of the kidneys. They produce adrenaline when we are angry or scared. This hormone prepares our body for action by increasing the heart rate and increasing the level of sugar in the blood.
        
        The ovaries (in females) produce oestrogen. This hormone causes changes in girls during puberty (for example, they grow breasts). It also helps to control the menstrual cycle.
        kidneys.
        
        The pancreas produces the hormones insulin and glucagon, which control the level of sugar in the blood.
        
        The testes (in males) produce testosterone, which causes changes in boys during puberty. It also controls sperm production.
- - - - Negative feedback works like the thermostat on a central heating system:
        
        If the body temperature starts to increase, the body acts to reduce the temperature.
        
        If the body temperature starts to decrease, the body acts to increase the temperature.
        
        This means that the temperature always stays around 37°C.
    - - Glucose in our blood provides us with energy. However, too much glucose can be harmful, so our body stores excess glucose as glycogen. Our blood sugar level (the amount of glucose in the blood) is regulated by two hormones: insulin and glucagon.