2.NEURONS AND SYNAPTIC TRANSMISSION

• What does every neuron have

  Each neurones has a cells body , axon and dendrites and after each axon there are axon terminals
• What does the cell body contain

  contains the nucleus of the cells
• What is the axon

  The axons carries the impulses aways from the cell body down the length of the neurone
• What is the axon covered with

  It is covered in a fatty layer of myelin sheath which protects the cells and increase the speed of electoral transmission
• What does the myelin sheath

  The myelin sheath is segmented by gaps called nodes of Ranvier - which speed up the transmission of the impulse by forcing it to 'jump' across the gaps along the axon
• How do neurons work

  Firstly a sensation is detected in the sensory neurone in the sensory receptors, e.g. this could be a pain receptor indicating a hot temp , this will lead to an electoral signal which rushes along the dendrite then to the axon ending at the axon terminal
• At the point of the axon terminal it converts into a chemical signal and crosses the synaptic cleft which is located in the spine.Then reflex responses are then passed to the motor neurone and in addition information from the relay neurone is sent to theCNS for processing.After the information is sent to the relay neurone it will be sent to the effect which in this case is muscle fibre which will then cause the limb to move out of danger
• What is a synapse

  the synapse is the point where one neurone can send a chemical message to an adjacent neurone
• What are neurotransmitter

  Neurotransmitters are chemical messengers that are released by neurone which relay signals across the synapse from one neutron to another.
• What are two types of neurotransmitters

  Neurotransmitter can be divided in to that that perform an excitatory function and those that perform an inhibitory function
• What is the excitatory neurotransmitter

  these are neurotransmitters that increase the likelihood of a new action potential forming in the postsynaptic cells
• What charge do excitatory neurotransmitters make

  When they are detected by receptors in the postsynaptic cell these neurotransmitters make the electrical charge inside more positive and more likely to fire- depolarisation [positively charged Sodium ions enter the postsynaptic cell]
• What is the inhibitory neurotransmitters

  these are neurotransmitters that decrease the likelihood of a new action potential forming in the post synaptic cells. When they are detected by receptors in the postsynaptic cell.
• What charge does the inhibitory neurotransmitters make

  These neurotransmitters make the electrical charge more negative and less likely to fire - hyper-polarisation [positively charged potassium ions level the postsynaptic cell]
• What is summation

  Summation is the combined effect of all the excitatory and inhibitory neurotransmitters influences on the post synaptic neurones.If a threshold is reached then a new action potential will form in the postsynaptic cell
• What is an example of a inhibition


  The neurotransmitter serotonin cause inhibition in the receiving neurone resulting in the neurone to be more negatively charged and less likely to fire [ hyper-polarisation]
• What is an example of excitation

  The neurotransmitter adrenaline cause excitation of the postsynaptic neurones by increasing its positive charge and making it more likely to fire [depolarisation]