Transcript The nervous system

THE NERVOUS
SYSTEM
By
Prof. Khaled Na3im
THE NERVOUS
SYSTEM
REGULATES ALL
THE BODY
FUNCTION .
The (N.S) is formed of 3 system s:
The central nervous
system , ( CNS ).
The peripheral nervous
system , (PNS ).
The autonomic
nervous system ,
(ANS ).
The ( C . N . S ) :
includes the brain + spinal cord
.The brain =
. Cerebrum
. Cerebellum
. Brain stem ( midbrain, pons and
medulla oblongata )
The ( p . N . S ) :
The PNS is made up of the cranial nerves and
the spinal nerves .
.The cranial nerves are 12 pairs.
. The spinal nerves are 31 pairs :
. 8 Cervical
.12 Thoracic
. 5 Lumbar
. 5 Sacral
. One Coccygeal
THE NERVE CELL
( THE NEURON )
The neuron ( nerve cell ) is
the functional and
anatomical unit of the
nervous system
Neurons
Humans have about 100 billion neurons in their
brain alone! While variable in size and shape
The neuron is formed of three parts.
1.Dendrites receive information from another
cell and transmit the message to the cell body.
2.The cell body contains the nucleus,
mitochondria and other organelles typical of
eukaryotic cells except the centrioles.
3.The axon conducts messages away from the
cell body out .
The neuron
The neuron
Mylinated nerve =
Mylinated axon
The neuron
Synapses
The synapse is a junctional space between a nerve
cell and another cell or effector is called a
synapse.
Messages travel within the neuron as an electrical
action potential.
The space between two cells is known as the
synaptic cleft. To cross the synaptic cleft requires
the actions of neurotransmitters.
Neurotransmitters are stored in small synaptic
vessicles clustered at the tip of the axon .
Types of Neurons
Three types of neurons occur. Sensory neurons
typically have a long dendrite and short axon,
and carry messages from sensory receptors to
the central nervous system. Motor neurons have
a long axon and short dendrites and transmit
messages from the central nervous system to
the muscles (or to glands). Interneurons are
found only in the central nervous system where
they connect neuron to neuron.
The brain
the brain made up :
Is 3 anatomical
parts :
1) cerebrum .
2) cerebellum .
3) brain stem .
The cerebrum
The cerebrum is formed of 2 cerebral
hemispheres , right and left .
The 2 cerebral hemispheres form the largest
part of the brain, occupying the anterior and
middle and posterior cranial fossae in the
skull and extending backwards over the
tentorium cerebelli.
They are made up of the cerebral cortex, the
basal ganglia, tracts of synaptic connections,
and the ventricles containing CSF .
THE CEREBRUM IS CONSISTED
OF:
2 cerebral
hemispheres :
right and left .
Lobes of the hemispere
Each hemisphere is divided into 4
lobes :
1) frontal lobe .
2) Parietal lobe .
3) Occipital lobe .
4) Temporal lobe .
Lies anterior contains most of
the motor areas ( it controls
movements , recent memory
and personality )
THE FRONTAL LOBE :
Lies superior contains most of the sensory areas .
THE PARIETAL LOBE :
Lies posterior and contains the centers of visions .
THE OCCIPITAL LOBE :
Lies inferior and contains the centers of hearing .
THE TEMPORAL LOBE :
The cerebellum
The Cerebellum
It is formed of 2 cerebllar hemispheres .
Controls :
1) Equilibrium
2) Coordination .
Thr cerebellum
The cerebellum is a large structure at the back
of the brain, immediately behind the
brainstem and below the occipital cortex. The
cerebellum receives direct inputs from the
sensory fibers in the spinal cord as well as
indirect inputs from the motor cortex,
possibly as a copy of the commands being
sent downward to the spinal cord.
Histology of the brain
The Brain stem
Is formed of 3 parts :
1) Midbrain .
2) Pons .
3) Medulle .
The midbrain
The midbrain (mesencephalon) occupies only a
small region in humans (it is relatively much
larger in "lower" vertebrates).
We shall look at only three features
The reticular Formation
the reticular formation:
collects input from
higher brain centers and
passes it on to motor
neurons .
The Substantia Nigra
the substantia nigra:
helps "smooth" out
body movements;
damage to the
substantia nigra causes
Parkinson's disease
VTA
the ventral tegmental area (VTA):
packed with dopamine-releasing neurons
The pons
The pons seems to serve as a relay station
carrying signals from various parts of the
cerebral cortex to the cerebellum .
The medulla
The medulla looks like a swollen tip to the spinal
cord. Nerve impulses arising here .
Medulla
rhythmically stimulate the intercostal muscles
and diaphragm — making breathing possible
The Blood Supply of the
Brain
Food and oxygen are carried to the
brain by many blood vessels.
These vessels are found on the
surface of the brain and deep within
the brain.
The blood vessels (and nerves) enter
the brain through holes in the skull
called foramina .
Blood Supply Of The Brain
Although the brain is only about 2% of the total
body weight in humans, it receives 15-20% of
the body's blood supply. Because brain cells
will die if the supply of blood which carries
oxygen is stopped, the brain has top priority
for the blood. Even if other organs need
blood, the body attempts to supply the brain
with a constant flow of blood