NEURONS (NERVE CELLS)

STRUCTURES

NEURONS (NERVE CELLS)

cell body

controls metabolism of nerve cell

dendrite

collects info from other cells

axon

extended to carry info over long distances

myelin sheath

electrical insulation which prevents distortion of the nervous impulse by activities of neighbouring cells

myelinated fibres

insulated fibres which have to cover long distances

unmyelinated fibre

uninsulated fibres which have to cover short distances

schwann cell

fatty individual cells which insulate the axon and form the myelin sheath

nodes of ranvier

allows rapid conduction of impulses by forcing messages to "jump" from one node to the next

functional units of the nervous system

types of neurons

morphological classification (structural types)

multipolar

bipolar

one axon and one dendrite
eg. inter

unipolar

just one axon with cell body to side of axon
eg. sensory

one axon and multiple dendrites extending from cell body
eg. interneurons and motor neurons

synapses

synapse: the junction between the branches of adjacent neurons

action at the synapse:

  1. nerve impulse reaches end bulb of axon
  1. vesicles move to end bulb membrane
  1. neurotransmitters are released into synaptic cleft
  1. neurotransmitters diffuse across cleft
  1. neurotransmitters bind to receptor sites on membrane of the dendrites of the next neuron
  1. binding on causes depolarisation of the next neuron's axon and the impulse travels on
  1. enzymes break down neurotransmitter after impulse has been transferred

functional types

interneurons

carry messages between motor and sensory neurons

motor neurons

carry messages away from CNS to effectors (muscles and glands) [efferent]

sensory neurons

carry messages from receptors to CNS [afferent]