Neuron
Has a cell body (soma), axon and dendrites. Carries signals via neurotransmitters.
Glia
Non-neural cells of the nervous system. Provide scaffolding, insulation and protection for neurons.
Astroglia
Star shaped glial cells involved in nutrition and support of neurons.
Microglia
Small glial cells that protect neurons.
Oligodendroglia
Form myelin around axons in the CNS.
Schwann cells
Form myelin around axons in the PNS
Action Potential Stage 1
Voltage gated sodium channels open. Sodium flows into the cell due to concentration gradient. Leaves the inside more positive than the outside.
Action Potential Stage 2
Potassium channels open as AP peaks. Potassium flows out of the cell, leaving the inside more negative again.
Action Potential Stage 3
Sodium potassium pump activates to restore the ionic balance of sodium and potassium.
Properties of Action Potentials
Same speed in any myelinated neuron.
Uniform size
One direction
Doesn’t decay (all or none)
Synaptic Transmission
Action potential causes depolarisation in the terminal buttons. This causes an influx of calcium ions which fuse vesicles to the presynaptic membrane, releasing neurotransmitters. These bind to receptors in the post-synaptic membrane which triggers a new action potential. Enzymes in the cleft breakdown some neurotransmitters and others bind to autoreceptors so they can be reused.
Ionotropic Receptors
Directly control an ion channel on the post-synaptic membrane. Neurotransmitter binds to receptor Channel opens Ions flow across membrane. Acts quickly, but not for long.
Metabotropic Receptors
Indirectly controls ion channels by releasing G-protein inside the post-synaptic neuron.
Neurotransmitter binds to G-protein
G-protein activates and moves towards adjacent ion channels
Channel opens and ions flow across membrane
Takes longer but lasts a longer time.
Excitatory Neurotransmitters
Causes excitation of the post-synaptic cell, increasing the chance of an action potential.
Acetylcholine, serotonin, glutamate.
Inhibitory Neurotransmitters
Causes inhibition of the post-synaptic cell, increasing the chance of an action potential.
Dopamine, GABA, noradrenaline, endorphins.