„ INTRODUCTION „ GRAY MATTER „ WHITE MATTER „ TRACTS IN SPINAL CORD „ ASCENDING TRACTS „ DESCENDING TRACTS „ APPLIED PHYSIOLOGY

1. Spinal Cord
M.Pandian,
Dept of Physiology

2. • „INTRODUCTION
• „GRAY MATTER
• „WHITE MATTER
• „TRACTS IN SPINAL CORD
• „ASCENDING TRACTS
• „DESCENDING TRACTS
• „APPLIED PHYSIOLOGY

3. INTRODUCTION
• Situation and Extent
-Spinal cord lies loosely in the vertebral canal.
-It extends from foramen magnum where it is
continuous with medulla oblongata,
-above and up to the lower border of first lumbar
vertebra below.
• Coverings
-Spinal cord is covered by sheaths called meninges
-Meninges are dura mater, pia mater and
arachnoid mater.
-These coverings continue as coverings of brain.

5. • Shape and Length
-Spinal cord is cylindrical in shape.
- Length of the spinal cord is about 45 cm in males
and about 43 cm in females.
• Enlargements
- Spinal cord has two spindle-shaped swellings,
namely cervical and lumbar enlargements
• Conus Medullaris and Filum Terminale
• - Below the lumbar enlargement, spinal cord rapidly
narrows to a cone-shaped termination called conus
medullaris

7. • Segments / Spinal Nerves
-Spinal cord is made up of 31 segments,

8. Cross Section of Spinal Cord

9. • Nerve Roots
-Each spinal nerve is formed by an anterior
(ventral) root and a posterior (dorsal) root

11. White Matter: Pathway Generalizations

12. Myelin-Stained Spinal Cord Sect.

13. Spinal Cord Trauma and Disorders
• Severe damage to ventral root results in flaccid paralysis (limp and
unresponsive)
• Skeletal muscles cannot move either voluntarily or involuntarily
• Without stimulation, muscles atrophy.
• When only UMN of primary motor cortex is damaged
• spastic paralysis occurs - muscles affected by persistent spasms
and
exaggerated tendon reflexes
• Muscles remain healthy longer but their movements are no
longer
subject to voluntary control.
• Muscles commonly become permanently shortened.
• Transection (cross sectioning) at any level results in total motor and
sensory loss in body regions inferior to site of damage.
• If injury in cervical region, all four limbs affected
(quadriplegia)
• If injury between T1 and L1, only lower limbs affected
(paraplegia)

14. Spinal Cord Trauma and Disorders
• Spinal shock - transient period of functional loss that follows the injury
• Results in immediate depression of all reflex activity caudal to lesion.
• Bowel and bladder reflexes stop, blood pressure falls, and all muscles
(somatic and visceral) below the injury are paralyzed and insensitive.
• Neural function usually returns within a few hours following injury
• If function does not resume within 48 hrs, paralysis is permanent.
• Amyotrophic Lateral Sclerosis (aka, Lou Gehrig’s disease)
• Progressive destruction of anterior horn motor neurons and fibers of the
pyramidal tracts
• Lose ability to speak, swallow, breathe.
• Death within 5 yrs
• Cause unknown (90%); others have high glutamate levels
• Poliomyelitis
• Virus destroys anterior horn motor neurons
• Victims die from paralysis of respiratory muscles
• Virus enters body in feces-contaminated water (public swimming pools)

15. 2 Primary Systems
Dorsal column-Medial
Lemniscal System
Corticospinal Tract

16. Brown-Séquard syndrome

19. Cerebrospinal Fluid (CSF)
• Cerebrospinal fluid (CSF) is the clear,
colorless and
• transparent fluid that circulates through
ventricles of brain, subarachnoid space and
central canal of spinal cord.
• It is a part of extracellular fluid (ECF).

20. Properties
• Volume : 150 mL (100 mL to 200 mL)
• Rate of formation : 0.3 mL per minute
• Specific gravity : 1.005
• Reaction : Alkaline.

22. FORMATION OF CEREBROSPINAL
FLUID
SITE OF FORMATION
• CSF is formed by choroid plexuses, situated within
the ventricles.
• Choroid plexuses are tuft of capillary projections
present inside the ventricles and
• covered by pia mater and ependymal covering.
• A large amount of CSF is formed in the lateral
ventricles.
MECHANISM OF FORMATION
• CSF is formed by the process of secretion that involves
active transport mechanism.
• Formation of CSF does not involve ultrafiltration or
dialysis.

23. SUBSTANCES AFFECTING THE
FORMATION OF CSF
1. Pilocarpine, ether and extracts of pituitary gland stimulate the
secretion of CSF by stimulating choroid plexus
2. Injection of isotonic saline also stimulates CSF formation
3. Injection of hypotonic saline causes greater rise in capillary
pressure and
intracranial pressure and fall in osmotic pressure, leading to
increase in CSF formation
4. Hypertonic saline decreases CSF formation and decreases the
CSF pressure.
The increased intracranial pressure is reduced by injection of
30% to 35% of sodium chloride or 50% sucrose.

24. Circulation of cerebrospinal fluid