Pseudounipolar neurons found in the spinal cord ganglia enable sensory impluses picked up by the dendrites to travel directly to the axon without passing through the cell body. Neurons may also be classified according to function. Sensory neurons are involved in the reception and transmission of sensory stimuli. Motor neurons send inpulses to control muscles and glands. Other neurons, interneurons, act as go-betweens between neurons as part of functional networks.
Synapses are specialized functional cell junctions to propogate cellular signals.
Most synapses are chemical synapses where vesicles in the presynaptic terminal contian a chemical messenger that is released to the synapic cleft when the presynaptic membrane is stimulated. The chemical messenger diffuses across the synaptic cleft to bind to receptors in the postsynaptic membrane. This induces a change in the polarization state of the postsynaptic membrane effecting cellular action. A special type of synapse is the neuromuscular junction . Once used, the neurotransmitters are removed quickly by enzymatic breakdown, difusion or endocytosis by the presynaptic cell.