Download The Central Nervous System

The Central Nervous
System
The Central Nervous System
There are two main
structures that make
up the central
nervous system
(CNS):
– Brain
– Spinal Cord
Coverings of the Brain and Spinal
Cord
The brain and spinal
cord are both delicate
and vital, nature has
provided them with
two protective
coverings:
– Bone (cranium and
vertebrae)
– Meninges (3 layers of
connective tissues)
Dura mater – made of
strong white fibrous
tissue
Arachnoid membrane
– delicate cob-web
like layer
Pia mater –
transparent innermost
layer of the meninges
that covers the brain
and spinal cord and
contains blood
vessels
The Meninges
Spaces Between & Around
the Meninges
Epidural Space
Outside the dura and
inside the bony
coverings of the brain
and spinal cord.
Contains supporting
cushion of fat and
other connective
tissues.
Subdural Space
Between the dura
mater and the
arachnoid
membrane
Contains a small
amount of
lubricating fluid
Subdural Hematoma
Subarachnoid Space
Under the archnoid space and outside of
the pia mater
Contains a significant amount of
cerebrospinal fluid
Menenges and Spaces
Histology of
the
Meninges
Meningitis
An infection or inflammation of the meninges
Most commonly caused by bacteria, however, it
may also be caused by viral or fungal infections
or tumors
Usually complain of fever and severe headaches
Can be fatal
Cerebrospinal Fluid (CSF)
Acts as additional cushion
Reservoir of circulating fluid that, along with
blood, the brain monitors for changes in the
internal environment.
If CO2 content in the CSF goes up, a
homeostatic response is triggered in the
respiratory control centers of the brainstem
Fluid Spaces
Found in the subarachnoid space
Within cavities and canals of the brain and
spinal cord
The large, fluid-filled cavities of the brain
are called ventricles.
Ventricles of the Brain
Formation
and
Circulation
of
CSF
The Spinal Cord
About 45 cm long
Extends from the foramen magnum to the
border of the first lumbar vertebrae
Two nerve roots project from each side of
the spinal cord
– Dorsal carries sensory information
– Ventral carries motor information out
Structure of the Spinal Cord
Spinal Cord Function
Two main functions
– Provides conduction routes to and from the brain
– Serves as an integrator for all spinal reflexes
Tracts provide conduction paths to and from the
brain (composed of axon bundles)
– Ascending tracts conduct sensory impulses up the
cord to the brain
– Descending tracts conduct motor impulses down the
cord from the brain
Spinal Tracts
The Brain
Weighs about three pounds in adults
Neurons can grown in size, but not increase in
number
Grows rapidly during the first nine years and
matures at about 18 years
6 Major divisions
Medulla Oblongata
Attaches to the spinal cord
Contains control centers—for example, the
cardiac, respiratory, and vasomotor control
centers
Pons
Lies just above the medulla
Passes information from the brain to the
body and vice versa, controls facial
expression.
Midbrain
Also called the mesencephalon
Forms the midsection of the brain
Involved in auditory and visual function as
well as some muscular control functions
Functions of the Brainstem
Sensory, motor and reflex functions
Reflexes such as those for vomiting,
coughing, sneezing, hiccupping and
swallowing are located in the brain stem
Cerebellum
2nd largest part of the brain
Gray matter makes up the outer portion, or
cortex and white matter makes up the
interior portions
Has numerous grooves (sulci) and raised
areas (gyri)
Functions of the Cerebellum
Acts with cerebral cortex to produce skilled
movements by coordinating activities of groups
of muscles
Helps control posture
Controls movements so they are not jerky
Controls skeletal muscles to maintain balance
Diencephalon
Located between the cerebrum and midbrain
The main structures of the diencephalon are the:
– Thalamus – sensations, relay info to cerebrum,
emotions, complex reflex movements
– Hypothalamus – link between mind and body and
links the nervous system and endocrine system
– Optic chiasma – optic nerves cross
– Pineal body – seems to be important in regulating the
body’s biological clock
Cerebrum
Largest division of the brian
Consists of two hemispheres
Surface (cerebral cortex) is made up of
gray matter only 2 – 4 mm thick
Each hemisphere is divided into 5 lobes
Functional Areas of the Cerebral
Cortex
Primary Somatic
Sensory and
Motor Areas of
the Cortex