Biology module B6

The Nervous system
1. The Nervous system detects and reacts to stimuli
2. the Nervous system is made up of different parts
  1. Central Nervous System (CNS)
    1. in Vertebrates this consists of the brain and the spinal chord only. In mammals the CNS is connected to the body by sensory neurones and motor neurones- these make up the peripheral nervous system (PNS)
      1. SENSORY NEURONES
        The neurones that carry impulses from the receptors to the CNS
      2. MOTOR NEURONES
        The neurones that carry impulses from the CNS to effectors
      3. EFFECTORS
        All your muscles and glands which respond to nervous impulses
3. The Central Nervous System (CNS) coordinates the response
  1. The CNS is a processing centre- receives information from the receptors
    1. and then coordinates a response (decides what to do about it)
Neurones and Synapses
1. information is transmitted around the body by Neurones
  1. The Gap Between Two Neurones is Called a Synapse
    1. Neurones aren't attached to each other- there's a tiny gap between them called the synapse.
    2. When an electrical impulse reaches the end of a neurone it triggers the release of transmitter chemicals into the synapse
      1. The transmitter chemicals diffuse across the gap and bind to receptor molecules on the membrane of the next neurone
        Only specific transmitter chemicals can bind to the receptor molecules on the neurone
        When the chemicals bind to the right receptors they trigger a new electrical impulse in the next neurone
    3. SOME DRUGS AFFECT TRANSMISSION ACROSS SYNAPSES
      1. Many drugs and toxins can interfere with the transmission of impulses across a synapse
        ecstasy works to block sites in the brain's synapses where the transmitter chemical Serotonin is removed
        Serotonin is thought to affect
2. when stimulated, Neurones transmit information around the body as electrical impulses
  1. The electrical impulses pass along the axon of the nerve cells
  2. Axons are made from nerve cell's cytoplasm stretched out into a long fibre and surrounded by a cell membrane
  3. Some axons are also surrounded by a fatty sheath that acts as an electrical insulator, shielding the neurone from neighbouring cells and speeding up the electrical impulse
  4. Electrical impulses carry information around the body really quickly so the responses they cause happen fast. But they're short lived, e.g. if your hand touches something hot you pull it away and the response is over
    1. Hormones (e.g. insulin and oestrogen) are also used to carry information around the body- they're produced in glands and travel around in the blood. The responses they cause are brought about more slowly and they're longer lasting than the responses caused by nerve impulse's

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Biology module B6

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	Created by anna.mat1997 almost 11 years ago