Spinal Cord Lecture Notes

Learning Outcomes

• Describe the protective structures of the spinal cord
• Describe the external and internal anatomical structures of the spinal cord
• Describe the sensory and motor pathways

Spinal Cord Anatomy

Central Nervous System (CNS)

• Composed of the spinal cord and brain.
• Protection:
  • Vertebrae
  • Meninges: Three layers (pia mater, arachnoid mater, dura mater)
  • Cerebral Spinal Fluid (CSF)

Meninges

• Pia Mater: Inner layer, delicate.
• Arachnoid Mater: Middle, spider web-like.
• Dura Mater: Tough outer layer.
• Epidural Space: Contains fat and blood vessels; location for analgesic injections.

Cerebrospinal Fluid (CSF)

• Produced by the choroid plexus.
• Acts as a cushion, found in the subarachnoid space.

Vertebrae

• Includes vertebral arch, body, and spinous process.

Spinal Cord Structure

• Begins at the medulla oblongata, ends at L2 for adults.
• Ends in a tapered section called the conus medullaris.
• Cauda Equina: Resembles a horse's tail.

Cross Section Anatomy

• Gray Matter: Butterfly shaped, contains cell bodies.
• White Matter: Myelinated axons, sensory and motor pathways.

Pathways

Motor Pathways

• Descending: From brain to muscles.
• UMN and LMN: Upper and Lower Motor Neurons.
• Corticospinal Tracts: Controls skeletal muscles.

Direct Pathways

• Lateral Corticospinal Tract: From cortex to spinal cord, decussates in medulla.
• Anterior Corticospinal Tract: Decussates at spinal cord.

Indirect Pathways

• Tectospinal, Vestibulospinal, Rubrospinal, Reticulospinal: Control reflexive movements, balance, limb movement, posture.

Sensory Pathways

• Ascending: Towards the brain.
• Spinothalamic Tracts: Pain and temperature.
• Dorsal Column-Medial Lemniscus: Somatosensory info.

Spina Bifida

• Failure of vertebrae to develop posteriorly.
• Types: Occulta, Meningocele, Meningomyelocele.

Spinal Nerve & Plexus

Spinal Nerve Structure

• 31 pairs: Cervical, thoracic, lumbar, sacral, coccygeal.
• Mixed motor and sensory.

Nerve Structure

• Epineurium, Perineurium, Endoneurium: Connective tissue layers.

Plexuses

• Cervical, Brachial, Lumbar, Sacral: Supply nerves to different body parts.
  • Cervical Plexus: Phrenic nerve controls diaphragm.
  • Brachial Plexus: Arm nerves.
  • Lumbar & Sacral Plexus: Leg nerves, sciatic nerve issues.

General Senses

Sensation & Perception

• Sensation: Activation of sensory receptors.
• Perception: Processed awareness of stimuli.

Tactile Sensations

• Merkel Cells, Pacinian Corpuscles, Meissner's Corpuscles: Different touch receptors.

Thermal & Pain Sensations

• Thermoreceptors: Temperature.
• Nociceptors: Pain.

Dermatomes

• Dermatome: Skin area linked to spinal nerves.
• Referred Pain: Pain felt in a different location.

Pain Relief

• Aspirin, Acupuncture: Methods to relieve pain.

Proprioception and Balance

• Stretch Receptors, Muscle Spindles, Tendon Organs: Monitor body position.

Reflexes

Reflex Arc

• Components: Sensory receptor, sensory neuron, integration center, motor neuron, effector.

Spinal Cord Injury

• Types: Paresis, Paraplegia, Quadriplegia.

Brown-Se'quard Syndrome

• Hemisection of the spinal cord, affects sensation and movement depending on the side of injury.

Neurological Exams

Sensory Testing

• Two-Point Discrimination: Tests skin sensation.

Motor Testing

• Tests muscle function and reflexes.

Proprioception

• Tests: Touch, gait observation, Romberg test.

Shingles

• Varicella-Zoster Virus: Causes chickenpox and can reactivate as shingles affecting nerves.