Friday, December 18, 2009

Prof. Noriah's note (4)

Picture's source:

Characteristic of CNS
Protected by cranium, meningis + csf

-secreted by choroid plexuses (special capillaries in ventricles of the brain → form BBB)
-act as shock absorbing medium

Brain stem
-pons → resp. center
-medulla → resp. center, cardiac center (coordinating reflex for vomiting, swallowing, coughing, sneezing)
-cerebellum → required for smooth coordinated movement + equilibrium

Blood brain barrier (BBB)
-Composed of endothelial cells packed tightly together to form tight junction that prevent passage of most molecules.
-An underlying basement membrane and specialized glial cells (astrocyte), which projects processes (pedicles) that attach to the walls of the capillary, reinforce this barrier.
-Very few substances can cross the BBB into brain tissue:
(1)Water is able to freely diffuse
(2)Glucose (the primary energy source of the brain) and amino acid require carrier-mediated transport
(3)Nonpolar lipid soluble substances can cross more readily than polar water-soluble ones
(4)Other active transport systems are present to pump weak organic acids, halides and extracellular K+ across the BBB

The blood – CSF barrier
-Cerebrospinal fluid (CSF) is clear, colorless fluid that normally contains none or few cells, a small amount of protein, and a moderate amount of glucose
-The blood – CSF barrier is composed of epithelial cells of the choroid plexus – a highly vascular structure, located within the ventricles .

Function of NS
Detect changes in internal and external environmental (in + outside the body)
via sense organs (receptors)

↓ (information sent to CNS by sensory nerve/afferent nerve)

CNS (brain/spinal cord) – intergrating center

↓ (analyse the sensory information via motor nerve/efferent nerve – send instruction to)


(a) special receptor
- hearing
- smell
- taste
- chemoreceptor
- osmoreceptor

(b) general receptor
- pain
- temperature
- proprioreceptor

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