neurons

parts of a neuron

motor neuron

 form synapses and control their contractions.

relay neuron

These neurons are the most common type of neuron in the CNS. They allow sensory and motor neurons to communicate with each other.

sensory neurons

Carry nerve impulses from sensory receptors to the spinal cord.

synapse

the conjunction of the end of the axon of one neuron and the dendrite or cell body of another.

neurotransmitter

chemical substances that play an important part in the workings of the nervous system by transmitting nerve impulses across a synapse.

synaptic transmission

refers to the process by which a nerve impulse passes across the synaptic cleft from one neuron (the presynaptic neuron) to another (the postsynaptic neuron)

three types of neurons

• sensory

• relay

• motor

dendrite

branches that receive message from other neurons

node of Ranvier

gaps in myelin sheath that speeds up nerve transmission

myelin sheath

fatty insulation around the axon that helps signals travel faster

schwann cells

cells that make the myelin sheath in the peripheral nerves

axon

long fibre that carries electrical impulses away from the body

terminal boutons

endings of the axon that release neurotransmitters to the next cell

how do neruons work

description of neurons working

• sensory neuron carries impulse to the CNS

• relay acts as a connection between sensory and motor neuron

• motor neruon carries nervous impulses out of the CNS to the muscles or gland

what does a sensory neuron look like

what does a motor neuron look like

what does a relay neuron look like

function of a sensory neuron

• carry nerve impulses from sensory receptors eg vision to brain and spinal cord

• convert info from recpetors into nerve impulses

• when they reach brain they are converted into sensations

• don’t all go to brain eg reflexes

where are sensory receptor found

in eyes, ear, tongue and skin

function of relay neurons

• allow sensory and motor neurons to communicate with each other

• found in brain in spinal cord

• in between sensory and motor neurons

functions of motor neurons

• conduct singla sfrom the CNS to effector organs eg muscle

• cell bodies in CNS but have long axons which can form parts of PNS

• motor neurons form synapses with muscles and control their contractions

what happens when motor neurons are stimulated

• release neurotransmitters that bind to receptors on muscle and triggers movement

• strength depends on rate of firing of axons relaxation caused by inhibition of motor neuron

what is a reflex arc

• Reflex arcs produce a fast response because impulses pass along a very simple nerve pathway involving very few neurons and synapses.

what does a reflex arc look like