neurons and synaptic transmssion

• Neuron


  The basic building block of the nervous system. Neurons are nerve cells that process and transmit messages through electrical and chemical signals.
• Neurotransmitters


  Brain chemicals released from synaptic vesicles. Neurotransmitters relay signals from one neuron to another across a synapse. Neurotransmitters can be broadly divided into those that perform an excitatory function and those that perform an inhibitory function.
• Synaptic transmission


  The process by which neighbouring neurons communicate with each other by sending chemical messages across the tiny gap (the synapse) that separates neurons.
• Neurons


  • They have the same basic structure
  • They vary in size and shape
• Synaptic transmission


  1. Neurotransmitter release from presynaptic neuron

  2. Neurotransmitter diffusion across synaptic cleft

  3. Neurotransmitter binding to receptors on postsynaptic neuron

  4. Conversion of chemical signal to electrical signal in postsynaptic neuron

  5. Neurotransmitter reuptake and breakdown
• Excitation and inhibition


  Neurotransmitters can have either an excitatory or inhibitory effect on the postsynaptic neuron
• Summation


  The excitatory and inhibitory influences on a postsynaptic neuron are summed - if the net effect is inhibitory then the neuron is less likely to fire, if the net effect is excitatory then the neuron is more likely to fire
• Several dozen neurotransmitters have been identified in the human brain, each with its own specific molecular structure and receptor
• Acetylcholine (ACh) is found where a motor neuron meets a muscle and upon its release will cause the muscle to contract
• Serotonin causes inhibition in the postsynaptic neuron making it more negatively charged and less likely to fire, while dopamine causes excitation of the postsynaptic neuron by increasing its positive charge and making it more likely to fire