Structure of a Neuron
Neurons are the nerve cells. A typical neuron
(Fig.1) consists of a cell body and two types
of processes – dendrites and axon. Most of
the cell organelles, including the nucleus, are
located in the cell body (also known as cyton
or perikaryon or soma). A typical neuron has
numerous highly branched processes called
dendrites. The dendrites receive signals from
other neurons.
A single axon arises from a cone-shaped
region of the cell body called the axon
hillock. The cytoplasm of an axon is called
the axoplasm. It is surrounded by a plasma
membrane called the axolemma. Axons are
often much longer than dendrites. Axons of
the motor neurons of the spinal cord that
innervate the foot muscles may be up to
one meter long. The axon is specialized in
conducting nerve impulses away from the
cell body to other neurons or effectors. Near
its other end, an axon usually divides into
many axon terminals (telodendria). The
swollen tips of axon terminals are called
synaptic end bulbs (terminal boutons). They
contain many tiny membrane-enclosed sacs
called synaptic vesicles that store a chemical
called a neurotransmitter.
The site of communication between
two neurons or between a neuron and an
effector cell is called a synapse. A neuronal
synapse is generally formed by an axon
terminal (presynaptic terminal), a region on
the surface of dendrite of another nerve cell
(postsynaptic terminal), and a thin
intercellular space called the synaptic cleft.
At most synapses, the pre-synaptic neuron
releases a chemical neurotransmitter thatBy: Murali Krishna (Hyderabad)