THE NERVOUS
SYSTEM
Dr. G. U. Israel
1. Introduction
TABLE OF CONTENT
2. cellular architecture
i.
Neuron
ii. Neuroglial cells
iii. Synapse
iv. Reflex arc
3. central nervous system
i.
The brain
ii. The spinal cord
4. peripheral nervous system
i.
Autonomic nervous system
ii. Somatic nervous system
INTRODUCTION
 The nervous system is the chief controlling and coordinating system of the body. It
is responsible for judgement, intelligence and memory, this made it the most
complex system of the body.
 This system is composed of highly specialized cells called neurons which can
detect, receive and transmit different kind of stimuli.
 Neves are composed of groups of
individual specialized neurons, which
transmit motor and sensory information
back and forth between the peripheral and
central nervous system.
Divisions of the Nervous System
1. Central nervous system (CNS)
2. Peripheral nervous system (PNS)
CELLULAR ARCHITECTURE
NEURON
 This is the structural and functional unit of the
nervous system.
 It’s a specialized cell which can detect, receive and
transmit different kind of stimuli.
 Neurons communicate with other cells via
synapses, using biochemical neurotransmitters.
Structure of the Neuron
 Cell body (soma); contains a nucleus, Golgi
apparatus, mitochondria, endoplasmic retinaculum,
ribosomes, Nissl's granules, etc.
 Dendrites; cytoplasmic extension of the soma. It
receives action potential and carry them towards
the body.
 Axon; it carries action potential away from the
soma.
CELLULAR ARCHITECTURE
NEURON
CELLULAR ARCHITECTURE
Classification of Neurons
1. According to the number of their processes.
i. Multipolar neurons
ii. Bipolar neurons
iii. Pseudounipolar neurons
iv. Unipolar neurons
CELLULAR ARCHITECTURE
Classification of Neurons
1. According to the length of axon.
i. Golgi type I
ii. Golgi type II
iii. Amacrine neuron
 Does not have axon, only dendrite
 Found in retina
CELLULAR ARCHITECTURE
CELLULAR ARCHITECTURE
Classification of Neurons
1. According to function.
i. Sensory neuron
ii. motor neurons
iii. Relay or Interneurons
CELLULAR ARCHITECTURE
CELLULAR ARCHITECTURE
Classification of Neurons
1. According to Shape.
i. Stellate
ii. Basket
iii. Fusiform
iv. Pyramidal
CELLULAR ARCHITECTURE
Classification of Neurons
1. According to Size.
i. Macroneuron: more than 7um, eg. Betz cells
ii. Microneuron: less than 7um, eg. Granular cells
CELLULAR ARCHITECTURE
NEUROGLIAL CELLS
 These are supportive cells that surround the cell bodies, dendrites, and axons
of neurons in both CNS and PNS. They include:
1. Astrocytes
2. Oligodendrocytes
3. Microglia
4. Ependymal cells
5. Schwann cells
CELLULAR ARCHITECTURE
SYNAPSE
 This is the site of contact between
neurons.
 Neurons are connected to one another
by their processes.
 The contact between neurons is by
contiguity and not continuity.
 Impulse is transmitted across a
synapse
through
biochemical
neurotransmitters (acetylcholine).
REFLEX ARC
 This is the functional unit
of the nervous system.
 It is neural pathway that
controls an action reflex
 An involuntary motor
response to a sensory
stimulus is called reflex
action.
It consist of:
• A receptor, e.g. skin
• The sensory neuron
• The interneuron
• The motor neuron
• The effector, e.g. muscle
CENTRAL NERVOUS SYSTEM
 This is the body’s processing center.
Function
1. Reception of sensory information (touch, pressure, pain, temperature,
vibration)
2. Receiving and perceiving special sensations (taste, smell, vision, sound)
3. Integration and processing of sensory information
4. Responds generation
Components
1. Brain
2. Spinal cord
CENTRAL NERVOUS SYSTEM
CENTRAL NERVOUS SYSTEM
BRAIN
Parts of the brain
Parts
Subdivisions
Principal Structure
Ventricle
Forebrain
(prosencephalon)
Telencephalon
Cerebrum, Basal ganglia,
limbic system
Lateral
Diencephalon
Thalamus, hypothalamus,
metathalamus,
epithalamus
Third
Midbrain
(mesencephalon)
Mesencephalon
Crus cerebri, substantia
Cerebral aqueduct
nigra, tegmentum, tectum
Hindbrain
(rhombencephalon)
Metencephalon
Pons, cerebellum
Myelencephalon
Medulla oblongata
Fourth
CENTRAL NERVOUS SYSTEM
CENTRAL NERVOUS SYSTEM
BRAIN
CENTRAL NERVOUS SYSTEM
SPINAL CORD
• It is the long cylindrical lower pat of the
CNS
• it’s the main pathway for information
connecting the brain and the PNS
 Meningeal Coverings
• Outermost dura mater
• Middle arachnoid mater
• Innermost pia mater
 Enlargements
• Cervical enlargement
• Lumbar enlargement
 Spinal Nerves
• 31 pairs of spinal nerves
• Each nerve arises by dorsal and ventral
nerve rootlet
CENTRAL NERVOUS SYSTEM
SPINAL CORD
CENTRAL NERVOUS SYSTEM
Tracts of the Spinal Cord
• A collection of nerve fibres that connects two masses of grey matter within the cns
is called a tract.
 Descending Tracts
 Ascending Tracts
 Pyramidal or corticospinal tracts
• Lateral spinothalamic tract
• Lateral corticospinal tract
• Anterior spinothalamic tract
• Anterior corticospinal tract
• Fasciculus gracilis
 Extrapyramidal tracts
• Fasciculus cuneatus
• Rubrospinal tract
• Dorsal spinocerebellar tract
• Medial reticulospina tract
• Ventral spinocerebellar tract
• Lateral reticulospina tract
• Spino-olivary tract
• Olivospinal tract
• Spinotectal tract
• Vestibulospinal tract
• Tectospinal tract
CENTRAL NERVOUS SYSTEM
SPINAL CORD TRACTS
PERIPHERAL NERVOUS SYSTEM
The peripheral nervous system is
divided into;
 Somatic Nervous System
• It is made up of 12 pairs of
cranial nerve and 31 pairs of
spinal nerves
It’s divided into:
 Sensory or afferent nervous
system
 Motor or efferent nervous system
 Autonomic Nervous System; it’s
divided into:
 Sympathetic nervous system
 Parasympathetic nervous system
PERIPHERAL NERVOUS SYSTEM
Cranial Nerves
 There are twelve (12) cranial nerves ,
arising from the brain, as follows;
 Forebrain: Olfactory nerve (CN I), optic
nerve (CN II)
 Midbrain: Oculomotor nerve (CN III),
trochlear (CN IV)
 Hindbrain
• Pons: Trigeminal nerve (CN V),
abducent nerve (CN VI), facial nerve
(CN VII), vestibulocochlear nerve (CN
VIII).
• Medulla oblongata: Glossopharyngeal
nerve (CN IX), vagus nerve (X),
accessory nerve (CN XI), hypoglossal
nerve (CN XII)
PERIPHERAL NERVOUS SYSTEM
Spinal Nerves
RECEPTORS
RECEPTORS
THE EAR
RECEPTORS
THE TONGUE
RECEPTORS
THE NOSE AND SMELLING PATHWAY
RECEPTORS
THE EYES AND VISION PATHWAY
RECEPTORS
THE SKIN
THANK YOU