3. Neuron
• Neuron is an electrically excitable cell that
processes and transmits information by
electrical and chemical signaling.
• A nerve is made up of many nerve cell fibers
(neurons) bound together by connective
tissue.
• Epineurium (Connective Tissue of Nerve).
• Perineurium ( Connective Tissue of Bundle of
Nerve Fibers).
• Endoneurium (Connective Tissue of Nerve
Fiber)
5. Cell Body (Soma)
• The neuronal cell body is the site where almost all
of the metabolic and biosynthetic machinery is
located.
• Mostly in C.N.S.
• 4 to 100 micrometers in diameter.
• The soma is the central part of the neuron. It
contains the nucleus and Organells of the cell, and
therefore is where most protein synthesis occurs.
• The nucleus ranges from 3 to 18 micrometers in
diameter.
6. Dendrites
• A branched protoplasmic extension of a nerve cell
that conducts nerve impulses from adjacent cells
inward toward the cell body; a single nerve may
possess many dendrites; typically dendrites are
relative short.
7. Axon
• An axon is a special cellular extension that
arises from the cell body at a site called the
axon hillock.
• Some axons are enveloped by Schwan Cells
which provide structural and metabolic
support.
• These are classified on Basis of
Presence/Absence of Myeline Sheath.
-> Myelinated ( Concentric Layers of Schwan
Cells) E.g Longer Axons
-> Non-Myelinated ( No Concentration).
8. Myelin
• Myelin is a fatty covering which envelops many
axons and permits action potentials to be
propagated at a much greater velocity.
9. Myelination
• A Schwann cell is illustrated
with brown cytoplasm.
• The blue oval is the
Schwann cell's nucleus.
• Observe that as the growing
Schwann cell spirals inward
around the axon, it wraps its
membrane into layers of
myelin.
10. Axon (Continued)
• Many neurons have only one axon, but this axon
may—and usually will—undergo extensive
branching, enabling communication with many
target cells.
• The part of the axon where it emerges from the
soma is called the axon hillock.
• Axon Hillock the most easily-excited part of the
neuron and the spike initiation zone for the axon.
11. Difference b/w Axon & Dendrites.
Feature Axon Dendrite
Shape Circular/ Constant Radius Taper
Length Large Small
Function Output Input
All Rules above has Exception.....
12. Synapse
• A site where two neurons join and
intercommunicate......
• The axon terminal contains synapses,
specialized structures
where neurotransmitter chemicals are
released to communicate with target neurons.
13. Nodes of Ranvier
• Nodes of Ranvier are short fragments of
unmyelinated segments of the axon, which
are found periodically in between the cells
of the myelin sheath. These nodes are areas
where the action potential is amplified
using a high density of sodium (Na+) ions
and is subsequently passed along the axon.
• The points between segments of myelin are
called nodes of Ranvier.
14. Support Cells
• Schwann cells
• Glial cells
• Oligodendroglia
• Astroglia or astrocytes
• Microglia
