•Gives out 31 pairs of spinal nerves , attached along the entire length of the cord by the ant/motor roots & the post/sensory roots

•Composed of an inner core of gray matter & an outer covering of the white matter

Divisions of the brain

Divisions of the forebrain

31 pairs

8 (cervical)

12 (thoracic)

5 (lumbar)

5 (sacral)

1 (coccygeal)

All are mixed nerves

The _____________________ is an H-shaped pillar with ant & post-gray columns/horns united by a thin gray commissure containing a small central canal.

The ____________________________ of the cord is further divided into anterior, lateral & posterior white columns

Functions of Spinal Cord

•Somatic (voluntary & Involuntary)

•Autonomic

•Cardiac & Secretomotor

Functions of Spinal Cord

•Unconscious

•Conscious

Effects of a complete section of Spinal Cord:

It results in:

•Loss of muscle tone

•All reflexes &

•Complete loss of sensations

•Called as “stage of spinal shock”

•E.g. muscle paralysis

Effects of a complete section of Spinal Cord:

It results in:

•Return of muscle tone (but hypotonic)

•Flexors are more active than extensors

•Muscles contracted in this reflex are called physiological flexors

•Reflex activity returns

It results in:

•If a general infection develops

•Mass reflex response disappears

•Threshold for all reflexes raised

Effects of hemi-section of Spinal Cord

Effects of complete section of Spinal Cord

¨Referred as part of embryonic

somite

¨It is defined as the

“ Area of the skin that provides sensory input to the central nervous system through one pair of the spinal nerves ”

¨It States that:

“Visceral pain is referred to dermatomes supplied by the posterior roots through which the visceral afferent impulses reach the spinal cord ”

Groups of nerve fibers carrying similar impulses are termed as __________.

Ascending tracts =

Descending tracts =

•Convey impulses in various parts of the body to different parts of brain

•Motor signals are sent from brain to lower motor neurons

•POSTERIOR

•COLUMN TRACTS

•LATERAL

•COLUMN TRACTS

•ANTERIOR

•COLUMN TRACTS

•INTERSEGMENTAL

•FIBERS

•Pyramidal tracts

•Extra pyramidal tracts

•Inter segmental fibers

—Includes:

—Fine touch

— Able to localize touch

—Tactile localization

— Able to identify the site of touch or pain

—Graphesthesia

— Ability y to recognize writing on skin

—Stereognosis

— Ability to recognize object

—Ability to detect rapidly changing peripheral conditions

—Sense of Pain & temperature

—Sense of alertness & consciousness