Spinal Cord Functions and Disorders Quiz

Chapter 13: The Spinal Cord and Spinal Nerves

• The purpose of this chapter is to identify and describe the anatomical features of the spinal cord and spinal nerves, discuss the functions of the spinal cord and spinal nerves, and understand spinal reflex arcs.
• The spinal cord is protected by bone (vertebrae), connective tissue (meninges), and fluid (cerebrospinal fluid).

Introduction

• The purpose of this chapter is to:
  • Identify and describe the anatomical features of the spinal cord and spinal nerves.
  • Discuss the functions of the spinal cord and spinal nerves, and their role in maintaining homeostasis.
  • Understand spinal reflex arcs.

Functions of the Spinal Cord

• Processes reflexes.
• Integrates EPSPs and IPSPs.
• Conducts sensory impulses to the brain and motor impulses to effectors.

Spinal Cord Anatomy

• (Information about spinal cord anatomy is omitted)

Protection of the Spinal Cord

• Protected by bone (vertebrae), connective tissue (meninges), and fluid (cerebrospinal fluid)-

Meninges

• The meninges consist of three layers:
  • Dura mater
  • Arachnoid mater
  • Pia mater

External Anatomy of the Spinal Cord

• The spinal cord begins as an extension of the medulla oblongata at the foramen magnum, terminating at the level of L2.
• The cauda equina (horses tail) is the roots of the lower spinal nerves.
• There are two enlargements: cervical and lumbar. The cervical enlargement controls sensory and motor input for upper extremities, while the lumbar enlargement handles that of legs.

Internal Anatomy of the Spinal Cord

• White matter is on the outside, gray matter is on the inside.
• Information about spinal nerve details, including specific sections, nerve roots etc omitted.

Sensory and Motor Processing

• The internal anatomy of the spinal cord allows for organized processing of sensory and motor information

Spinal Nerves

• Spinal nerves connect the CNS to sensory receptors, muscles, and glands, functioning as part of the peripheral nervous system.
• There are 31 pairs of spinal nerves
• Roots attach to a spinal nerve to the spinal cord segment.

Connective Tissue Covering of Spinal Nerves

• Three connective tissue layers cover spinal nerves:
  • Epineurium
  • Perineurium
  • Endoneurium

Peripheral Nerves

• Spinal nerves communicate between the spinal cord and specific areas of the body.
• Nerves are grouped into fascicles surrounded by perineurium
• Entire nerve sheathed by epineurium

Peripheral Nerves

• Spinal nerves exit the CNS and immediately split into three major branches: anterior ramus, posterior ramus, and rami communicantes.
• Some nerves travel alone while others join into large "braided ropes" called plexuses.

Branches of a Spinal Nerve

• Spinal nerves branch into rami
• Branches include posterior ramus, anterior ramus and meningeal branches

Dermatomes

• Certain skin segments are supplied by spinal nerves that carry somatic sensory nerve impulses to the brain.

Cervical Plexus

• Supplies the skin and muscles of the head, neck, upper part of the shoulders and chest, and the diaphragm.
• A main nerve within this plexus is the phrenic nerve that controls the diaphragm.

Brachial Plexus

• Provides the major nerve supply for the shoulders and upper limbs.
• Median nerve injury results in carpal tunnel syndrome, characterized by numbness and tingling in the palm and fingers.

Nerve Plexuses

• The long thoracic nerve emerges, supplying the serratus anterior muscle
• Injuries can happen to any of the brachial plexuses.
• The ulnar nerve is the largest unprotected nerve in the human body. Damages often result in abnormal sensations in the 4th and 5th fingers.

Lumbar Plexus

• Originates from various spinal nerves, with different branches supplying various parts of the lower body.

Sacral Plexus

• Primarily concerns itself with the sciatic nerve

Spinal Cord Physiology

• To regulate homeostasis, the spinal cord conducts nerve impulses and processes information.
• White matter transmits nerve impulses to and from the brain; gray matter processes incoming and outgoing information, executing spinal reflexes.

Sensory and Motor Tracts

• White matter tracts conduct nerve impulses to and from the brain.
• Gray matter receives and integrates information, performing spinal reflexes.

Reflexes and Reflex Arcs

• Reflexes are fast, involuntary, and unplanned responses to stimuli.
• Gray matter acts as the coordinating center for spinal reflexes

Reflexes

• Contains various important spinal reflexes in the body; including knee-jerk (patellar) reflex, Achilles reflex & plantar reflex.

Disorders

• Traumatic injuries causing monoplegia, paraplegia, hemiplegia, quadriplegia
• Damage from other processes (examples: spinal cord compression, degenerative diseases, shingles, Polio)