Prof.Dr. Selda Önderoğlu
The organism reacts to changes and adjusts itself to its external and internal
environments.
Changes or events which excite an organism are called STIMULI
the effects which result from these stimuli are called REACTIONS or RESPONSES.
The system within the body responsible for
these changes is the nervous system.
For descriptive purposes the nervous system of vertebrates is divided into:
CENTRAL NERVOUS SYSTEM
PERIPHERAL NERVOUS SYSTEM
THE CENTRAL NERVOUS SYSTEM CNS
The central nervous system consists of the BRAIN (ENCEPHALON) and the SPINAL CORD.
THE CNS is essentially a compact bundle of
nerve cells and nerve fibers embedded in a
NEUROGLIA (GLIA).
THE PERIPHERAL NERVOUS SYSTEM (PNS)
Extending from the CNS are:
- 12 pairs of CRANIAL nerves and
- 31 pairs of SPINAL nerves
which together with their branches
modulate sensory and motor functions.
- and: sensory(spinal) and autonomic GANGLIA.
Also related to the PNS are the peripheral
part of the AUTONOMIC nervous system
(ANS)namely : VISCERAL (SPLANCHNIC)
nerves
Cranial nerves: 12 pairs
Spinal nerves: 31 pairs 8 cervical
12 thoracic 5 lumbar 5 sacral 1 cocygeal
A typical spinal nerve
Ventral root+dorsal root Unite and form a spinal nerve
Then;
A spinal nerve is divided into
Dorsal branch+ventral branch
Sensory (spinal) ganglion
MAJOR DIVISIONS OF THE CNS
ENCEPHALON (BRAIN) SPINAL CORD
The CNS is invested by membranes called MENINGES (MENINX)
a) DURA MATER
b) ARACHNOID MATER
c) PIA MATER
THE SPINAL CORD
ENCEPHALON
The encephalon consists of a number of regions:
RHOMBENCEPHALON (HINDBRAIN)
MYELENCEPHALON ( Medulla oblongata)
METENCEPHALON (Pons) CEREBELLUM
MESENCEPHALON (MIDBRAIN)
PROSENCEPHALON (FOREBRAIN) DIENCEPHALON
CEREBRAL HEMISPHERES
PROSENCEPHALON
DIENCEPHALON
THALAMUS
METATHALAMUS
HYPOTHALAMUS
EPITHALAMUS
SUBTHALAMUS
CEREBRAL HEMISPHERES (2 in number)
BRAIN STEM
MEDULLA OBLONGATA
PONS
MIDBRAIN (Mesencephalon)
The encephalon consists of a number of regions:
RHOMBENCEPHALON (HINDBRAIN)
MYELENCEPHALON ( Medulla oblongata)
METENCEPHALON (Pons) CEREBELLUM
MESENCEPHALON (MIDBRAIN)
PROSENCEPHALON (FOREBRAIN) DIENCEPHALON
CEREBRAL HEMISPHERES
CEREBELLUM
The encephalon consists of a number of regions:
RHOMBENCEPHALON (HINDBRAIN)
MYELENCEPHALON ( Medulla oblongata)
METENCEPHALON (Pons) CEREBELLUM
MESENCEPHALON (MIDBRAIN)
PROSENCEPHALON (FOREBRAIN) DIENCEPHALON
CEREBRAL HEMISPHERES
DIENCEPHALON is composed of:
-Thalamus
-Hypothalamus
-Subthalamus
-epithalamus
HYPOTHALAMUS
EPITHALAMUS & SUBTHALAMUS
Brain Ventricles
-there are spaces in certain parts of CNS
called ventricles namely:
-lateral Ventricle -Third Ventricle -Fourth Ventricle
Ventricles are filled with Cerebrospinal fluid(CSF)
Fourth ventricle continues in the central canal of the
spinal cord and connects to
subarachnoid space through
foramina.
LATERAL VENTRICLE -Within the cerebral hemispheres
-Two in number -each is located
in each hemisphere
CAVITY OF THE DIENCEPHALON:
THE THIRD VENTRICLE
CAVITY OF THE HINDBRAIN is the
THE FOURTH VENTRICLE
4th VENTRICLE & CEREBRAL AQUEDUCT (of SYLVIUS)-connects III ventr. To 4th
ventr.
The encephalon consists of a number of regions:
RHOMBENCEPHALON (HINDBRAIN)
MYELENCEPHALON ( Medulla oblongata)
METENCEPHALON (Pons) CEREBELLUM
MESENCEPHALON (MIDBRAIN)
PROSENCEPHALON (FOREBRAIN) DIENCEPHALON
CEREBRAL HEMISPHERES
THE CEREBRAL HEMISPHERES (CEREBRUM)
The cerebrum is the most cranial part of the brain.
It lies in the anterior and middle cranial fossa and is related to the concavity of the skull.
There are two cerebral hemispheres:right and left
The two hemispheres are partially separated from each other by the longitudinal cerebral fissure.
Has convolutions: gyrus (gyri:plural)
between gyri has sulcus (sulci:plural)
Each cerebral hemisphere has:
- an external layer of GREY MATTER and
- a central core of WHITE MATTER(MEDULLARY SUBSTANCE).
In the medullary substance are located several large masses of grey matter called BASAL GANGLIA(nucleı or subcortıcal nucleı).
Each hemisphere contains a cavity called the LATERAL
VENTRICLE.
Lateral ventricles -2 in number
THE MEDULLARY SUBSTANCE (white matter)
basically contains three types of fibers:
ASSOCIATION FIBERS:Interconnect various regions of the same hemisphere.
COMMISSURAL FIBERS: Interconnect corresponding regions of the two hemispheres.
PROJECTION FIBERS: Convey impulses from the cortex
to distant regions and vice versa.
Commissural fibers Largest one of these is the:
corpus callosum
