Transcript 01-introduction of

THE N.S
The nervous and 
endocrine systems
control the functions of
the body.
FUNCTIONS
(1) It receives 
information (stimuli)
that arise either outside
or inside the body from
different sensory
receptors.
These are grouped 
together to form
sensory input.
FUNCTION
(2) It integrates 
and correlates
these sensory
input.
(3) It effects a 
response to an
effector (muscle or
gland) through the
motor output.
CLASSIFICATION OF N.S.
(1) Central nervous system 
(CNS)
(2) Peripheral nervous system 
(PNS)
CENTRAL NERVOUS SYSTEM
It is formed of : 
The brain and spinal cord. 
They occupy the dorsal 
body cavity.
They are the main centers 
where correlation and
integration of nervous
information occur.
PERIPHERAL N.S
It is the link between 
the CNS and peripheral
structures.
It is formed of : 
1.Cranial and Spinal 
nerves.
2.Their ramifications 
within the body.
3.Associated Ganglia. 
CLASSIFICATION OF NERVES
Nerves are classified 
according to the
direction in which they
carry impulses :
(1) sensory (afferent): 
They carry impulses 
toward the CNS.
(2) Motor (efferent) : 
They carry impulses 
from the CNS.
(3) Mixed . 
FUNCTIONAL CLASSIFICATION
OF PNS
1. Sensory (Afferent): 
A. Somatic : 
It delivers impulses to 
the CNS from:
Skin. 
Skeletal muscles. 
joints. 
B. Visceral : 
It transmits impulses 
from the visceral
organs.
FUNCTIONAL CLASSIFICATION
OF PNS
2. Motor (efferent ) 
A. Somatic : 
It allows conscious 
(voluntary) control of skeletal
muscles.
B. Autonomic 
It controls involuntary 
activity of smooth, cardiac
muscles and glands.
AUTONOMIC N.S
It is divided into 
Sympathetic and
Parasympathetic.
In both there are 
afferent, efferent
nerve fibers and
ganglia.
AUTONOMIC N. SYSTEM
It has a chain of two motor 
neurons (Ganglia).
The first motor neuron is in 
the brain or spinal cord.
Its axon (Preganglionic) 
synapse with the second
motor neuron (outside )
the CNS.
The axon of this neuron is 
(Postganglionic) extends to
the organ which it serves.
INTERNAL STRUCTURE OF N.S.
The interior of the 
N.S. is organized
into gray and white
matter.
GREY MATTER
It is composed of 
large numbers of
excitable nerve
cells (Neurons) and
their processes
which are
supported by
specialized tissue
(Neuroglia).
NEURONE
It is the structural and 
functional unit of the
nervous system.
It receives and integrates 
information from sensory
receptors or other neurons
and transmit information to
the effector organs.
PROCESSES OF NEURONS
Dendrites : 
They are receptive 
processes.
They can detect 
changes in the
external or internal
environment.
PROCESSES OF NEURONS
Axons : 
Carry information away from 
the cell body.
They can be divided into 
several collaterals.
Terminal Buttons : 
Are at the end of the axon 
where information is
transferred to the dendrites of
other neurons. Transmission of
information between neurons
is always by chemical not
electrical means.
FUNCTIONAL CLASSIFICATION
OF NEURONS
1. Sensory 
Carry information 
from the periphery
to the CNS to reach
the conscious level.
Their cell bodies 
are always outside
the CNS in a
ganglion.
2. MOTOR (EFFERENT)
Their cell bodies are always
located in the CNS.
They are divided into upper 
and lower motor neurons.
3. ASSOCIATION
(INTERNEURONS)
They are relay neurons 
connecting sensory and 
motor neurons.
They reside entirely 
within the CNS.
Their cell bodies are 
always located in the
CNS.
WHITE MATTER
It consists of nerve 
fibers embedded in
neuroglia.
Tracts : 
Nerve processes 
sharing common
connections,
course and
functions.
REFLEXES
They are rapid, predictable 
and involuntary responses to
stimuli.
They are : 
(1) Somatic reflexes : 
Stimulate skeletal muscles. 
(2) Autonomic reflexes : 
Regulate smooth muscles. 
PROTECTION OF CNS
The brain and spinal 
cord are covered
with meninges and
are suspended in the
cerebrospinal fluid.
They are further 
protected by the
bones of the skull
and vertebral
column.
BRAIN
Is divided into : 
Fore brain. 
Mid brain. 
Hind brain. 
HIND BRAIN
It consists of : 
Cerebellum 
Medulla . 
Pons. 
MEDULLA OBLONGATA
It is continuous 
caudally with the
spinal cord.
It extends rostrally 
to the pons.
PONS
It owes its name to its 
appearance as that of
a bridge connecting
the two cerebellar
hemispheres.
CEREBELLUM
It is an important center 
which is essential for
accurate, coordinated
and purposeful
movements.
It operates at an 
unconscious level.
STRUCTURE
It has an outer layer of 
grey matter (cerebellar
cortex) which is highly
convoluted and forms
regular folds (Folia).
The white matter 
forms the central core.
MID BRAIN
It is rostral to the 
pons.
Its dorsal surface is 
formed by four
rounded eminences
(Superior and Inferior
Colliculi).
BRAIN STEM
It forms a small part of 
the entire brain.
It consists of : 
Medulla. 
Pons. 
Mid brain (It is the 
smallest part of the
brain stem).
BRAIN STEM
It is attached to the 
cerebellum by three
parts of nerve fibers
(peduncles) :
Inferior to the 
medulla.
Middle ( largest 
peduncle) to the
pons.
Superior to the mid 
brain.
FORE BRAIN
It consists of :
Diencephalon .
Two cerebral
hemispheres.
DIENCEPHALON
It is formed of four 
subdivisions in a
dorsoventral direction
(1) Epithalamus 
The Pineal Gland is its 
most notable part .
It is immediately rostral 
to the superior colliculi
of the mid brain.
DIENCEPHALON
(2) Thalamus 
It is the largest 
part.
It has an important 
role in the sensory,
motor and
cognitive
functions.
DIENCEPHALON
(3) Subthalamus 
. (4) 
Hypothalamus
It is involved with 
the autonomic,
limbic and
cardiovascular
systems.
CEREBRAL HEMISPHERES
They represent the 
massive part of the
forebrain.
The two 
hemispheres are
separated by the
Great Longtudinal
Fissure.
The fissure is 
occupied by the
Falx Cerebri.
CEREBRAL HEMISPHERES
The cerebral cortex is 
highly convoluted for
maximising the
cortical surface area.
The convolutions are 
the Gyri and the
furrows between
them are the Sulci.
Some of these gyri 
and sulci mark the
location of important
functional areas.
CEREBRAL LOBES
Each hemisphere is 
divided into four
lobes which are
named according to
the names of the
bones of the skull
beneath which they
lie.
CEREBRAL LOBES
The lobes are : 
Frontal lobe . 
Its most anterior convexity 
is the frontal pole.
Parietal lobe. 
Temporal lobe. 
Its tip is the temporal pole. 
Occipital lobe. 
It terminates in the 
occipital pole.
STRUCTURE
It consists of an 
outer layer of grey
matter (cortex)
and an inner mass
of white matter.
BASAL GANGLIA
They are large 
masses of cell
bodies (grey matter)
which are buried
within the white
matter.
BASAL GANGLIA
They are concerned 
with the control of
muscle tone
posture.They are
important in the
facilitation of
appropriate motor
behavior and the
inhibition of
unwanted
movements.
BASAL GANGLIA
The largest 
component is the
Corpus Striatum.
It consists of : 
Caudate nucleus. 
Putamen and 
Globus pallidus.
FUNCTIONAL CORTICAL AREAS
(Frontal lobe)
Precentral gyrus which 
contains the primary
motor cortex.
It is the highest level in 
the brain for the control
of voluntary, skilled
movements(muscles of
speech, fascial
expression and hand
movements).
The opposite half of the 
body is represented in a
highly precise fashion.
UPPER MOTOR NEURONES
They are in the motor 
cerebral cortex.
Their axons form the 
descending tracts
(corticospinal and
corticobulbar) which
control the activity of
the lower motor
neurons.
LOWER MOTOR NEUROENS
Their cell bodies are in 
the spinal cord and
brain stem.
They constitute the 
final pathway by which
the nervous system
controls the skeletal
muscles.
FUNCTIONAL CORTICAL AREAS
(PARIETAL LOBE)
Postcentral gyrus 
(primary
somatosensory
cortex)
It is the site of 
termination of
pathways carrying
touch, pressure, pain
and temperature from
the opposite half of
the body.
FUNCTIONAL CORTICAL AREAS
Occipital Lobe : 
Visual cortex 
Temporal Lobe : 
Auditory cortex 
CORTICAL FIBERS
Corona Radiata 
It is a radiating 
pattern which
is formed from the 
afferent and efferent
fibers between the
cerebral cortex and
subcortical
structures.
CORTICAL FIBERS
Internal Capsule 
It is deep inside 
the hemisphere.
The fibers are
arranged as a
dense sheet of
white matter
CORTICAL FIBERS
Corpus Callosum 
It is a sheet of 
transversely running
nerve fibers
(Commissural Fibers)
which link
corresponding areas of
the two cerebral
cortices.
It lies in the depths of 
the longtudinal fissure.
VENTRICULAR SYSTEM
It is the site of 
production of the
CSF which is
secreted by the
choroid plexus.
VENTRICULAR SYSTEM
Fourth ventriclrre 
It is the rostral 
continuation of the
central canal of the
spinal cord.
It is a shallow, 
rhomboid-shaped
depression on the
dorsal surface of the
medulla and pons
beneath the
cerebellum.
VENTRICULAR SYSTEM
Cerebral aqueduct 
It runs through the mid 
brain beneath the
superior and inferior
colliculi.
Third ventricle 
It is a slit like chamber 
which is narrow from
side to side.
Its lateral walls are 
formed by the
diencephalon especially
the thalamus.
VENTRICULAR SYSTEM
Lateral ventricle 
It is an extensive 
chamber within the
cerebral hemisphere. It
is C – shaped.
It communicates 
with the third ventricle 
through the
interventricular foramen
(foramen of Monro).