Central Nervous System and Somatic Nervous System

what is the brain?

• big bundle of nerve cells

• made up of grey matter (cellular mass of the brain) and white matter (the 'wiring', sends signals between the grey matter

where is the grey matter?

frontal lobe, temporal lobe and spinal cord and cerebellum

where is the white matter?

parietal lobe and occipital lobe (largest single lobe, controls spacial awareness)

what does the spine do?

• transmits motor and sensory signals to and from the brain

• responsible for reflex actions where it would take too long for the brain to get involved

what do relay neurons do? (in the spine)

connect motor and sensory neurons

what happens when a sensory neuron sends a signal?

transmits to the spine and via relay neurons and directly communicate with the muscles via motor neurons

similarities between the neurons

all have a cell body, dendrites and an axon

differences between motor and sensory neurons

• motor neurons cell body's are at the start, sensory's are at the middle

• motor neurons direction of travel is spine/brain -> muscle

• sensory neurons direction of travel is muscle -> spine/brain

what is nodes of ranvier?

the myelin sheath has gaps in it and ranvier discovered this. he said that the gaps speed up conduction as they allow negatively charged ions back into the nerve

three main neurons

sensory, relay, motor

recall the synaptic transmission process

1. action potential causes an electrical impulse to travel down a neuron to the pre-synaptic nerve terminal

2. triggers a release of neurotransmitter from the vestibules into the synaptic cleft (gap)

3. neurotransmitters travel across the synaptic cleft and bind to their complementary post synaptic receptor sites

4. opens on channels (gaps for ions) allowing either positive or negatively charged ions to flow into the next neuron

what two processes make action potential?

excitation and inhibition

what are excitatory neurotransmitters?

• a.k.a adrenaline

• cause the absorption of positively charged ions (that are constantly fired)

what are inhibatory neurotransmitters?

• a.k.a GABA

• causes the absorption of negatively charged ions (we slow down)

what is action potential set by?

• the overall charge from the absorbed positive and negatively charged ions

• the higher the positive charge, the more likely it is to fire the next electrical impulse