Neurons

• Neurons- 


  Highly specialised cells that are responsible for transmitting information throughout the body (in chemical and electrical forms)
• Dendrite -


  Receives information from other neurons to transmit electrical signals towards the body
• Cell body - 


  Core of the neuron- maintain the cell and keeps neuron functioning efficiently
• Axon-

  Carries signals away from the cell body to the terminal buttons, in order to transmit the electrical signals
• Myelin sheath -


  Insulates axon to stop interference from other neurons and protect the axon, this transmits the signal quicker as a result
• Axon terminal-

  Responsible for transmitting the signal on to other neurons
• Sensory neuron-

  These carry messages from PNS to CNS. They have long dendrites and short axon
• Afferent neuron (sensory neuron) -

  Sends information towards the brain
• Relay neurons - 


  These connect sensory neurons to the motor neurons or other relay neurons. They have short dendrites and short axons
• Efferent neurons (motor neuron)


  Carry information away from the brain
• Synaptic transmission- 


  The process of transmitting messages from neuron to neuron
• Synapse 


  The synapse is specialised gap between neurons through which electrical impulse from the neuron is transmitted chemically
• Action potential- 


  When an electrical impulse is transmitted down an axon
• Pre synaptic cell (sending)
• Post synaptic cell (receiving)b
• Summation-

  -A post synaptic cell can receive a positive and negative potential at the same time

  -Addition of positive and negative potentials, determines whether or not the neuron will fire

  >creates an electrical impulse in post synaptic neuron, transmit messages
• Summation-

  If the potentials at post synaptic cell are mostly positive, it is more likely to fire
• Summation-

  If potentials at post synaptic cell are mostly negative, it is less likely to fire
• Excitatory effect- 


  -Increases positive charge and increases the likelihood that the neuron will fire and pass on electrical impulse

  -Mostly positive potential in summation
• Inhibitory effect- 


  -Increases negative charge and decreases likelihood that the neuron will fire and pass on electrical impulses

  -Mostly negative potentials
• Motor neuron function- 


  Connects the CNS to the effectors such as muscles and glands
• Motor neuron structure - 


  Short dendrites

  Long axons
• Synaptic transmission part 1- 


  -Action potential reaches end of axon of the pre synaptic neuron (axon terminals)

  -Action potential stimulates vesicles. Vesicles release neuro-transmitter (exocytosis) into synaptic cleft
• Synaptic transmission part 2- 


  -Neurotransmitter diffuses across the synaptic cleft and binds to receptor sites of post synaptic cell

  -Once they are activated they have an excitatory (more likely to fire) or inhibitory (less likely to fire) effect.

  -Summation occurs
• Synaptic transmission part 3- 


  -The process is terminated by reuptake, pre synaptic neuron to be reused

  -Enzymes break down any left over neurotransmitter in the synapse
• Positive potentials - 


  If the potentials at post synaptic cell are mostly positive, it is ore likely to fire
• Negative potentials- 


  If the potentials at the post synaptic cell are mostly negative, it is more likely to fire