neurons and synaptic transmission

micro level NS

contains 100billion nerve cells that are called neurons (specialised cells), 80% of these located in brain alone. electrical impulses travel from one end of a neuron to the other and release a chemical called neurotransmitter.

NS steps

1. when a message travels down a neuron it’s in the form of an electrical impulse called action potential

2. to be passes onto the next neuron the message had to cross a small gap called synaptic cleft. as electrical impulses cannot pass over the gap they are converted into a chemical message through the use of neurotransmitters

3. if the next neurone is activated by these neurotransmitters the message is converted back into an electrical impulse that travels down neuron

nerve impulses that neurons create are

units of info processing. all aspects of behaviour is coded by the frequency and pattern of nerve impulses in different parts of the brain

sensory neurons

• carry messages from the PNS to CBS

• tells brain about external and internal environment by processing information one of the 5 sets of sensory receptors quickly converted into neural impulses

• impulses translated into sensations for reactions

• long dendrites, short axons

relay neurons

• most common type of neuron in the CNS

• carries nerve impulses between sensory and motor neurons

• carry along the CNS

• found in brain, spinal chord and visual system

• short stubby dendritrd and axons

motor neurons

• connect CNS to effectors (muscles and glands)

• form synapses with muscles releases neurotransmitters when stimulated to trigger a muscular response (contract)

• short dendrites, long axons

neurotransmitters definition

although each neuron creates a nerve impulses and a chemical reaction at the terminal buttons, they can differ whether they actually encourage further activation or discourage further activation in neighbouring neurons

excitation

neurotransmitters create excitation of post synaptic neuron they create a positive charge and make neuron more likely to fire, increased activation potential causes increased activity eg. dopamine

inhibition

they create a negative charge that makes the neuron less likely to fire, decreased action potential causes decreased activity eg. GABA or serotonin