Organization of the Nervous System

2011-09-25T00:12:00.000-07:00

This topic will discuss about the Organization of the Nervous System – this will help some student to understand the nervous system organization.

ANATOMICAL DIVISION

1. CNS

Brain
Spinal cord

2. PNS

Cranial nerves, except CN I
Spinal nerves – origin: spinal cord
Associated ganglia

ª Collection of nerve cell bodies:

CNS: nuclei/nucleus
Outside the CNS: ganglion / ganglia

3. ANS – constituent part of the CNS and PNS

a. Parasympathetic

Origin: Cranio-sacral
Cranial – CN 3, 7, 9 & 10
Sacral – sacral cord levels and sacral spinal nerves 2, 3 & 4

b. Sympathetic

Origin:Thoraco-lumbar
Arises from the spinal cord – T1-L2 or L3
Forms the sympathetic trunk with its ganglia

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FUNCTIONAL DIVISION

1. Sensory / Afferent

Receives and transmits impulses to the CNS

2. Motor/ Efferent

Impulses originate from the CNS

ª Gray matter / cerebellar cortex / cerebral cortex – collection of nerve cell bodies

ª White matter – collection of myelinated axons (tracts,fasciculus,peduncle, columns)

** note: in spinal cord – gray matter is found at the center while white matter is at the periphery

TYPES OF FIBERS

1. Commissural

Helps communicate one hemisphere to another
i.e. corpus callosum

2. Association

Communicates within the same hemisphere

a. Long

b. Short

3. Projection

Need to communicate (in the gray matter) involving several fibers in different locations
i.e. corona vadiata

TRACTS – fibers with common origin and destination

1. Ascending

Spinothalamic tract
Sensory

2. Descending

Corticobulbar tract
Corticospinal tract
Motor tract

ª White matter of the spinal cord

Fasciculus – cervical part of the cord

§ Ganglia – upper

§ Cunneatus – lower

Funniculus – anterior, lateral, dorsal

>> Additional Info (from Dr. Elma) – in order to identify which side of the spinal cord is dorsal or ventral

àseen cross sectionally the spinal cord has:

Ventral median fissure – deeper
Dorsal median sulcus – shallow (Posterior)

Glial cells / Neuroglia

Astrocytes
Oligodendrocytes
Microglia – macrophage system
Macroglia – collective term for astrocytes and oligodendrocytes
Ependymal cells – lining the central canal of spinal cord

Homunculus

Motor – bigger hands (left)
Sensory – bigger lips and arms (right)

For Med Students

Organization of the Nervous System

This topic will discuss about the Organization of the Nervous System – this will help some student to understand the nervous system organization.