Nervous System

Topics: Brain, Cerebrum, Central nervous system Pages: 46 (2458 words) Published: December 5, 2014
Prof. Melvin Carreon
Physiological Psychology
University of the East

Anatomical Directions

Rostral/Anterior – toward the head of a fourlegged animal
Caudal/Posterior – toward the tail
Inferior/Ventral – toward the belly
Superior/Dorsal – toward the back
Neuraxis – an imaginary line that runs the
length of the spinal cord to the front of the brain
Midline – an imaginary line dividing the body
into two equal halves
Ipsilateral – directional term referring to
structures on the same side of midline

Contralateral – opposite side of the midline
Medial – toward the midline
Lateral – away from the midline
Proximal – closer to center
Distal – opposite of proximal
Coronal section – anatomical section dividing the
brain front to back, parallel to the face
Sagittal section – parallel to the midline
Midsagittal section – sagittal section that divides
the brain into two equal halves
Horizontal/axial section – divides the brain from
top to bottom

Meninges (singular: meninx )

The protective sheaths around
the brain & the spinal cord

The meninges consist of three
layers: the dura mater, the
arachnoid mater, and the pia
The primary function of the
meninges and of the
cerebrospinal fluid is to
protect the central nervous

Layers of Meninges
Dura Mater – means hard mother, the outermost w/c is
tough & flexible. It surrounds & supports the large venous
channels carrying blood from the brain toward the heart.
Arachnoid membrane – the middle layer, so named
because of its spider web-like appearance. It provides a
cushioning effect for the CNS.
Pia Mater - very thin membrane composed of fibrous tissue
covered on its outer surface by a sheet of flat cells
thought to be impermeable to fluid. It is pierced by blood
vessels which travel to CNS, and its capillaries are
responsible for nourishing the brain.

Cerebrospinal Fluid

occupies the space
between the arachnoid
mater & the pia mater.
produced by Choroid plexus

It acts as a "cushion" or
buffer for the cortex,
providing a basic
mechanical and
immunological protection
to the brain inside the skull.

CSF serves four primary purposes

Buoyancy: The actual mass of the human brain is about
1400 grams; however, the net weight of the brain suspended in the CSF is equivalent to a mass of 25 grams. It allows the brain to maintain its density w/o being impaired by its own weight, which would cut off blood supply & kill neurons in the lower section.

Protection: CSF protects the brain tissue from injury when jolted or hit. In certain situations such as auto accidents or sports injuries, the CSF cannot protect the brain from forced contact with the skull case, causing hemorrhaging, brain damage, and sometimes death.

Chemical stability: CSF flows throughout the inner ventricular system in the brain and this allows for homeostatic regulation of the distribution of neuroendocrine factors, to which slight changes can cause problems or damage to the nervous system.

Prevention of brain ischemia w/c is made by decreasing the amount of CSF in the limited space inside the skull.

The brain contains a series
of hollow interconnected
chambers: ventricles
(little bellies) w/c are filled
w/ CSF.
The largest chambers are
the lateral ventricles w/c
are connected to the third
The cerebral aqueduct (a
long tube) connects the
third ventricle to the fourth

Human Brain
The brain emerges during embryonic development from the
neural tube. The most anterior part of the neural tube is called the telencephalon, w/c expands rapidly due to cell
proliferation, and eventually gives rise to the brain.
 Gradually some of the cells stop dividing and differentiate into neurons and glial cells. The newly generated neurons migrate to...
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