nervous

1. NERVOUS SYSTEM
(Basic concepts regarding human nervous system)

2. The nervous system in man and in other higher animals is
composed of 2 major components :
1. Central nervous system (CNS)
2. Peripheral nervous system ( PNS)
 Central nervous system consists of brain and spinal cord.
 Peripheral nervous system consists of nerves that arise
from brain and spinal cord (CNS) and spread in differents
parts of body.
 CNS = brain + spinal cord
 PNS = nerves
 All these components are made of neurons, it means
CNS (brain & spinal cord) and PNS ( nerves) ,all are made
of neurons.

3. All these components are made of neurons.

4. Neuron or nerve cell
• it is the unit of nervous system.
• the human nervous system consists of billions of neurons plus
supporting cells called neuroglial cells.
• Human nervous system = neurons + neuroglial cells.
• Neurons are cells ,just like other cells of the body , but they are
specialized cells because they transmit information from one part of
the body to the other in the form of electrical impulses. In this way
they communicate with each other and with other types of body cells.
this means that neuron communicates with other neurons in nervous
system and neuron also communicates with other cells of body such
as heart cells , muscle cells e.t.c
This communication occurs through junctions called synapses, we
will discuss it later.

5. Neurons have 3 distinct parts;
1. Cell body (soma)
2. Axon
3. Dendrites
• cell body : nucleus and most of the cytoplasm of the neuron is
located in its cell body.
• Dendrites and axons are actually the cytoplasmic projections from
the cell body.
• Axons conduct impulses away from the cell body.
• Dendrites conduct impulses toward cell body.

7. • Schwann cells ; special neuroglial cells located at regular intervals
along axons.
• Myelin sheath; in some neurons schwann cells secrete a fatty
layer over axons called myelin sheath.
• Nodes of ranvier ; between the areas of myelin on an axon, there
are non-myelinated points called nodes of ranvier.
 Types of neurons:
1. Sensory neurons
2. Interneurons
3. Motorneurons.

8. Sensory neurons
• they conduct sensory information from receptors towards CNS.
• They have one dendrite and one axon.

9. Interneurons
• Form brain and spinal cord
• They receive information, interpret them and stimulate motor neurons.
• They have many dendrites and axons.

11. Motor neurons
• Carry information to muscles or glands ( effectors )
• They have many dendrites but only one axon.

15. Nerve
• A union of several axons that are enveloped by a covering made of
lipid.
• Based on the property of axons , nerves are classified into 3 types :
1. Sensory nerves : contains the axons of sensory neurons only.
2. Motor nerves : contain the axons of motor neurons only.
3. Mixed nerves ; contain the axons of both sensory and motor neurons.
A nerve is an enclosed, cable-like
bundle of nerve fibres called axons, in
the peripheral nervous system. A nerve
transmits electrical impulses and is the
basic unit of the peripheral nervous
system.

17. Peripheral nervous system
• It is composed of nerves and ganglia
• A ganglion is a group of neuron cell bodies in the peripheral
nervous system.
• In certain parts of body, the cell bodies of many neurons form a
group enveloped by a membrane, this is called ganglion.
• Ganglia are ovoid structures containing cell bodies of neurons
and glial cells supported by connective tissue. Ganglia function
like relay stations - one nerve enters and an other exits
• A ganglion (pl. ganglia) is a mass of nerve cell bodies found
outside of the central nervous system (CNS) along with some glial
cells and connective tissue.

19. PNS continued……..
• Nerves arise or lead to brain and spinal cord, so they are named as
cranial and spinal nerves.
• 12 pairs of cranial nerves
• 31 pairs of spinal nerves
• Some cranial nerves are sensory , some are motor and some are mixed.
• All spinal nerves are mixed nerves.

22. • Cranial and spinal nerves make 2 pathways
1. Sensory pathway
2. Motor pathway
 Motor pathway makes 2 systems
3. Somatic nervous system
4. Autonomic nervous system
 Autonomic nervous system comprises of
5. Sympathetic nervous system (SNS)
6. Parasympathetic nervous system (PANS)

23. Cranial and
spinal
nerves
Motor
poathway
Somatic
nervous
system
Autonomic
nervous
system
Sensory
pathway
sympatheti
c
parasymp
ethetic

25. Any questions?