Neurons are specialized cells that transmit nerve signals in the brain and spinal cord. There are several types of neurons defined by their structure and function. Structurally, neurons consist of a cell body containing the nucleus, dendrites which receive signals, an axon which transmits signals, and axon terminals which release neurotransmitters and connect to other cells. Functionally, neurons are classified as sensory, motor, or interneurons depending on whether they transmit signals to or from the central nervous system. Neuroglia provide support and protection for neurons and include astrocytes, oligodendrocytes, microglia, and ependymal cells.

1. NEURON
STRUCTURE
TYPES
( Rabbia Yousaf)

2.  A nerve cell alongwith all its processes is a neuron.
 Excitable cells that are specialized for the reception
of stimuli and the conduction of the nerve
impulse.
 Found in the brain and spinal cord .
 Do not undergo division and
replication.

3. Neuron Anatomy
Axon hillock
(trigger zone)
Soma (cell body)
Axon (transmits signals)
Axon terminals
(stimulate
another cell)
Dendrites (receive
signal)

5.  DENDRITES function to receive the signal and
carry the nerve conduction toward the cell body.
 SOMA (cell body) is where the nucleus,
ribosomes, and most organelles are located
 AXON HILLOCK is the area on the soma where
the action potential of the neuron
builds up before it transmits the
signal down the axon.

6.  AXON function is to transmit signals. Some
cells have many axons, some have one, some
are short, and some are long.
 AXON TERMINALS (also called synaptic
knobs) contain a neurotransmitter which,
when released, stimulates another cell.

7.  A synapse is the site at which two neurons
communicate.
 The neuron that conducts the signals towards the
synapse is called the presynaptic neuron.
 The neuron that transmits the signals away from the
synapse is called the postsynaptic neuron.
 Most neurons function as pre-synaptic and
post-synaptic neurons.
 The neurons don’t physically touch each
other at the synapse. The space between
them is called the synaptic cleft.

9.  Morphological
 Functional

10.  On the basis of number, length, and mode of
branching of the neurites.
1.Pseudounipolar
2.Unipolar
3.Bipolar
4.Multipolar
1. Golgi type I
2. Golgi type II

12.  Possess a single process that extends from the
cell body and subsequently branches into an
axon and dendrite.
 Present in spinal and cranial gangli.

13.  Possess a single process
 Rare in vertebrates.
 Mesencephalic neurons of trigeminal nerve
 Amacrine cells of retina

14.  possess an elongated cell body, from each end
of which a single neurite emerges
 Examples of this type of neuron are found in
the retinal bipolar cells and the cells of the
sensory cochlear and vestibular ganglia.

15.  have a number of neurites arising from the cell
body.
 With the exception of the long process, the
axon, the remainder of the neurites are
dendrites.
 Most neurons of the brain and spinal cord are
of this type.

16.  have a long axon that may be 1 m or more in
length in extreme cases. The axons of these
neurons form the long fiber tracts of the brain
and spinal cord and the nerve fibers of
peripheral nerves. The pyramidal cells of the
cerebral cortex, the Purkinje cells of the
cerebellar cortex, and the motor cells of the
spinal cord are good examples.

17.  Have a short axon that terminates in the
neighborhood of the cell body or is entirely
absent.
 Numerous short dendrites give them a star-
shaped appearance.
 They greatly outnumber the Golgi type I
neurons.

19.  Neurons are grouped functionally according to
the direction the nerve impulse travels relative to
the CNS.
Sensory Neurons
Motor Neurons
Interneurons

20.  Sensoroy Neurons (afferent neurons)
 Transmit impulses toward the CNS.
 They originate in the PNS and terminate in the
CNS.
 Motor Neurons (efferent neurons)
 Transmit impulses from the CNS to effector
organs (muscles and glands).
 They originate in the CNS and terminate in the
PNS.

21.  Interneurons (association neurons)
 connect sensory neurons to motor neurons
within the spinal cord and brain.
 They originate and terminate in the CNS, and
form complex neuronal pathways.
 They make up 99.98% of the neurons in the
body, reflecting the vast amount of
information processed in the CNS.

22.  Located only in the CNS
 Several cell types
 Do not conduct impulses-do not form synapses
with other cells.
 Outnumber neurons.
 Embedded in a web of tissue termed the
neuroglia.
 They function to support and protect
neurons.

24. 1. Astrocytes (Protoplasmic astrocytes & Fibrous
astrocytes )
2. Oligodendrocytes
3. Schwann cells
4. Microglia
5. Ependymal cells

25.  The largest of the neuroglial cells.
 Have many processes with expanded pedicles
(vascular feet)
 Surround blood vessels or contact the pia
mater.
 Protoplasmic astrocytes reside mostly
in gray matter
 Fibrous astrocytes reside mostly in
white matter

27.  Form a protective sealed barrier between the
pia mater and the nervous tissue of the brain
and spinal cord.
 They provide structural support for nervous
tissue.
 They proliferate to form scar tissue after
injury to the CNS.

28.  They are necessary for the survival of neurons.
 Located in both gray matter and white matter
 Produce myelin, a sheath that insulates and
protects axons in the CNS.
 Each oligodendrocyte produces myelin for
several axons.

30.  Perform the same function in the PNS as
oligodendrocytes in the CNS; protect and
insulate neurons.
 A myelin sheath consists of several Schwann
cell wrapped around a single axon.

32.  small, phagocytic neuroglial cells
 Activated microglial cells become antigen-
presenting cells and secrete cytokines.

34.  Epithelial cells that line the neural tube and
ventricles of the brain.
 They help in movement and formation of CSF
(choroid plexus formation).

35.  hyperphysics.phy-
astr.gsu.edu/hbase/biology/nervecell.html
 biology.tutorvista.com/cell/nerve-cell.htm