Synaptic transmission

• Action potential

  • Neuron in resting state - inside of the cell is negatively charged.
  • Neuron sufficiently activated by stimulus - inside of cell becomes positively charged for a split second.
  • Rapid switch from negative to positive charge is called depolarisation.
  • Depolarisation creates an electricall impulse that travels down the axon, towards the terminal buttons.
  • Action potential is generated when depolarisation reaches a certain threshold - it is an all or nothing event.
• • Neurons communicate with eachother withing groups called neural networks.
  • They are seperated by tiny gaps called a synaptic cleft.
• How are signals within a neuron transmitted?

  Electrically
• How are signals between neurons transmitted?

  Chemically
• Synaptic transmission process:

  1. Chemical process that starts with an action potential - the elctrical impulse passed down the axon triggers the release of neurotransmitters from vesicles.
  2. The neurotransmitters diffuse across the synapse to the next neuron.
  3. The neurotransmitters fit onto matching receptor sites on the post synaptic neuron - here, the signal is converted back into electricity.
  4. Neurotransmitters left in the synapse are reabsorbed by the presynaptic neuron to be used again - this is called reuptake.
• Neurotransmitters

  • Chemical messengers that act between the neurons.
  • Each one has its own specific molecular structure that fits perfectly into a specific type of postsynaptic receptor.
• Noradrenaline

  • Fight or flight response.
  • Sleeping - dreaming.
  • Learning
  • Attention
  • Emotion - mood control.
• Dopamine

  • Posture and control of movement.
  • Dependency behaviour - addiction.
  • Cognitive functions.
  • Emotions.
• Serotonin

  • Regulates body temperature.
  • Sleep - wakefulness.
  • Hunger.
  • Feeling pain.
  • Mood control - happiness and good mood.
• Acetylcholine

  • Stimulates muscle contraction and key function in motor control and movement.
  • Cognitive functions including memory and thinking.
  • Expressions of some emotions e.g. anger and sexuality
• Gamma-aminobutyric acid (GABA)

  • Inhibitor, so blocks messages.
  • Calms nerves that are firing, so produces feelings of relaxation.
  • Low levels are associated with anxiety.