2. OVERVIEW OF THE NERVOUS
SYSTEM
The nervous
system has two
major anatomical
subdivisions;
The central
nervous system
(CNS)
The peripheral
nervous system
(PNS)
4. CELLS OF THE NERVOUS SYSTEM
There are two cells of the nervous
system. These are;
Neuron
Neuroglia
The functional unit of the nervous
system is the nerve cell, or neuron
Neuroglia or glial are supportive cells in
the nervous system that aid the function
of neurons
5. NEURONS (Nerve Cells)
Neurons have three fundamental
physiological properties:
1. Excitability
2. Conductivity
3. Secretion
A typical neuron is divided into three
parts;
Soma or cell body (perikaryon)
Dendrites
Axon
7. CLASSIFICATION OF NEURONS
Neurons may be classified according
to structure or function.
Function
neuron
• Interneuron
(association)
• Motor neuron
Structure
• Sensory (afferent)• Unipolar neurons
• Bipolar neurons
• Multipolar
neurons
• Anaxonic neurons
12. SYNAPTIC TRANSMISSION
The meeting point between a neuron
and any other cell is called a synapse
The synapses b/t neurons and skeletal
muscle cells are referred to as
myoneural or neuromuscular
junction
Synapse can be;
Chemical synapse
Electrical synapse
14. CENTRAL NERVOUS SYSTEM
The CNS consists of the brain
and spinal cord
CNS protected by a cranium
surrounding the brain
vertebral column surrounding
the spinal cord
The CNS is bathed in
cerebrospinal fluid
The CNS is composed of gray
and white matter
15. THE BRAIN
The brain is semi-spherical but soft delicate
complex organ.
It is the center for control and integration
An adult brain weighs near 1.5 kg (3-3.5lbs)
Averages about 1,600 g (3.5 lb) in men
1,450 g in women
Composed of an estimated 100 billion (1011)
neurons
Anatomically, the brain is divided into 3 region;
Forebrain
Midbrain
Hindbrain
18. The brain is lined by membrane
called meninges.
The brain is conspicuously marked
by surface gyri (folds) and sulci
(grooves).
The human brain is composed of
neurons, glial cells and blood
vessels.
It also consists of four internal,
interconnected chambers called
ventricles.
20. FOREBRAIN
Forebrain consist of the following regions; Telecephalon
(cerebrum) and Diencephalon (Thalamus, hypothalamus,
epithalamus and pituitary gland)
CEREBRUM
The cerebrum is the largest part of the brain.
It is divided into two hemispheres separated by the
longitudinal fissure.
The hemispheres are prominently marked with gyri and
sulci.
Portions of the two hemispheres are connected internally
by the corpus callosum
Each cerebral hemisphere is subdivided by deep sulci, or
fissures, into the five lobes: Frontal, Parietal, Occipital,
Temporal and Insula
23. DIENCEPHALON
A major autonomic region of the brain that consists of vital
structures such as;
Thalamus, Hypothalamus , Epithalamus , Pituitary
gland
completely surrounded by the cerebral hemisphere of the
telencephalon.
These structures surround the third ventricle of the brain
The thalamus is a large ovoid mass of gray matter
The hypothalamus is a small portion of the diencephalon
inferior to the thalamus
The epithalamus is the dorsal portion of the diencephalon
that includes a thin roof over the third ventricle.
The pituitary gland, or hypophysis, is positioned on the
inferior aspect of the diencephalon
24. MIDBRAIN
The midbrain is a short section of the
brain stem between the diencephalon
and the pons
A short segment of the brainstem that
connects the hindbrain and forebrain
Within the midbrain is the cerebral
aqueduct (aqueduct of Sylvius)
It includes important centers for
vision, hearing, pain, and motor
control
26. HINDBRAIN
The embryonic hindbrain differentiates into two
subdivisions the metencephalon and
myelencephalon
The metencephalon is the most superior portion
of the hindbrain.
The pons which measures about 2.5 cm long,
forms a broad anterior bulge in the brainstem
just rostral to the medulla.
It conducts signals up and down the brainstem
and between the brainstem and cerebellum
The cerebellum is the largest part of the
hindbrain and receives most of its input by way
of the pons.
Occupies the inferior and posterior aspect of
the cranial cavity
29. MENINGES OF THE
CENTRAL NERVOUS SYSTEM
The CNS is protected by
three connective tissue
membranes coverings
called meninges
From superficial to deep,
they are;
Dura mater,
Arachnoid mater,
Pia mater
30. CEREBROSPINAL FLUID &
VENTRICLES OF THE BRAIN
ventricles
Two lateral ventricles
A third and fourth ventricles
The brain has four internal chamber called
The fourth ventricle is located in the brain
stem
The cerebral aqueduct (aqueduct of
Sylvius) passes through the midbrain to
link the third and fourth ventricles.
CSF is a clear fluid that forms a protective
cushion around and within the CNS
32. SPINAL CORD
It is an elongated cylindrical structure that is a
ropelike bundle of nervous tissue
In adults, it averages about 1.8 cm thick and 45
cm long
It begins as a continuation of the medulla
oblongata at the level of the foramen magnum
The spinal cord serves three principal functions:
Conduction, Locomotion and Reflexes
The cord gives rise to 31 pairs of spinal
nerves. the part supplied by each pair of spinal
nerves is called a segment.
The spinal cord is divided into cervical,
thoracic, lumbar, and sacral regions.
34. CROSS-SECTIONAL ANATOMY
The spinal cord consists of two kinds of
nervous tissue called gray and white
matter.
Gray matter has a relatively dull color
because it contains little myelin.
It has butterfly- or H-shaped in cross
sections
It contains the somas, dendrites, and
proximal parts of the axons of neurons.
It is the site of synaptic contact between
neurons (information processing)
36. White matter contains an abundance of myelinated
axons, which give it a bright, pearly white
appearance.
It is composed of bundles of axons called tracts or
fascicule
It carry signals from one part of the CNS to another.
The spinal cord has two tracts; Ascending and
descending tract
Ascending tracts carry sensory information up the
cord and descending tracts conduct motor
impulses down
38. PERIPHERAL NERVOUS SYSTEM
The (PNS) is that portion of
the nervous system outside
the central nervous system
Sensory receptors within the
sensory organs, neurons,
nerve, ganglia, and plexuses
are all part of the PNS
The nerves of the PNS are
classified as;
cranial nerves or spinal nerves,
39. GENERAL ANATOMY OF
NERVES AND GANGLIA
Anerve is a cordlike organ composed of
numerous nerve fibers (axons) bound together
by connective tissue.
Nerve fibers of the peripheral nervous system
are ensheathed in Schwann cells, which form a
neurilemma and often a myelin sheath around
the axon. Nerves has:
endoneurium, perineurium and epineurium
41. CRANIAL NERVES
Cranial nerves are nerves that emerge directly
from the brain and the brainstem.
There are 12 pairs of cranial nerves, numbered I
to XII
They relay information between the brain and
parts of the body.
Considers to be parts of both CNS and PNS
They are traditionally classified as sensory,
motor or mixed base on their functions.
44. SPINAL NERVES
There are 31 pairs of spinal nerves: 8 cervical
(C1–C8), 12 thoracic (T1–T12), 5 lumbar
(L1–L5), 5 sacral (S1–S5), and 1 coccygeal
(Co).
The first cervical nerve emerges between the
skull and atlas
The others emerge through intervertebral
foramina, including the anterior and posterior
foramina of the sacrum and the sacral hiatus.
45.
46. AUTONOMIC NERVOUS SYSTEM (ANS)
ANS is motor nervous system that controls
glands, cardiac muscle, and smooth muscle
The primary target organs of the ANS are the
viscera of the thoracic and abdominal cavities
Its job is to regulate such fundamental states
and life processes as heart rate, blood
pressure, body temperature, respiratory
airflow, pupillary diameter, digestion,
energy metabolism, defecation, and
urination.
47. DIVISION OF THE ANS
The ANS has two subsystems
Sympathetic
parasympathetic divisions
Sympathetic (Thoracolumbar) Division
The sympathetic division is also called the
thoracolumbar division
It has relatively short preganglionic and
long postganglionic fibers
48. PARASYMPATHETIC DIVISION
The parasympathetic division is also
called the craniosacral
Somas of the preganglionic neurons are
located in the pons, medulla oblongata,
and segments S2 to S4 of the spinal cord
The parasympathetic division has long
preganglionic fibers reaching almost all
the way to the target cells
short postganglionic fibers that cover the
rest of the distance.
