Download Chapter 13: The Spinal Cord, Spinal Nerves, and Spinal Reflexes

Chapter 13: The Spinal Cord and
Spinal Nerves
BIO 210 Lab
Instructor: Dr. Rebecca Clarke
Spinal Cord
 Structurally and functionally integrated with brain
 Occupies upper two-thirds of vertebral column (adult: 1.5 ft
long, 0.5 in. wide)
 Ends between vertebrae L1 and L2
Gross Anatomy of the Spinal Cord
 Divided into 4 regions (like
vertebrae):
 Cervical (C)
 Thoracic (T)
 Lumbar (L)
 Sacral (S)
 31 Pairs of spinal nerves
 Named for regions
 Cervical numbered for
vertebra below
 Rest numbered for vertebra
above
Figure 13-2
Gross Anatomy of the Spinal Cord: Distal End
 Conus medullaris (medullary
cone):
 Conical structure at T-L junction
 Filum terminale (terminal filum):
 Thin strand of fibrous tissue at end of
conus medullaris
 Cauda equina (“horse tail”):
 Bundle of elongated nerve roots
extending below conus medullaris
(L2-S5)
 Note: After age 4, vertebral column continues
to elongate but spinal cord does not therefore
roots elongate)
Figure 13-2
Sectional Anatomy
of the Spinal Cord
 Posterior median sulcus: Groove on posterior side
 Anterior median fissure: Deeper, wider groove on anterior side
 Gray matter covered by thick layer of white matter
Figure 13–5a
Sectional Anatomy of the Spinal Cord: Gray
Matter
 Neuron cell bodies, neuroglia, unmyelinated axons
 H- or butterfly-shape with horns (projections)
 Gray commissure – where axons connect R/L sides
 Central canal in middle; contains CSF
Figure 13–5a
Sectional Anatomy of the Spinal Cord: Gray
Matter
 Cell bodies organized in nuclei in horns of gray matter:
 Somatic and visceral
 Sensory (dorsal) and motor (ventral)
Figure 13–5a
Sectional Anatomy of the Spinal Cord: White
Matter
 Spinal tracts (bundles of myelinated axons) arranged in columns
 Have similar distribution as nuclei in gray matter
 Relay same type of info (sensory or motor) in same direction (ascending
or descending) to brain
Figure 13–5a
Gross Anatomy of a Spinal Nerve
 Forms 2 branches on each
side of spinal cord:
 Dorsal root:
 Contains axons of sensory
(afferent) neurons coming from
receptors
 Ventral root:
 Contains axons of motor
(efferent) neurons going to
effectors
 Dorsal root ganglion:
 Contains cell bodies of sensory
neurons
Figure 13-2
Mixed Nerves
 Carry both sensory (afferent) and motor (efferent) fibers
 Spinal nerves are mixed nerves
Spinal Nerves and Plexuses
Spinal Nerves and Plexuses
Nerve Plexus
 Complex interwoven network of nerve fibers of adjacent
spinal nerves
 Formed during development
 Nerves arising at a plexus:
 Are mixed nerves (like spinal nerves)
 Control skeletal muscles of neck, upper torso, limbs
4 Major Nerve Plexuses
 Cervical plexus
  Neck, thoracic cavity, diaphragm
  Phrenic nerve
 Brachial
  Shoulder/pectoral girdle and upper limbs
  Radial and ulnar nerves
 Lumbar
  Pelvic girdle and lower limbs
  Femoral nerve
 Sacral
  Pelvic girdle and lower limbs
  Sciatic nerve
Figure 13–9
Brachial Plexus
Meninges
 Specialized, protective membranes
 Separate, isolate, protect soft tissue of:
 Spinal cord from bones of vertebra (spinal meninges)
 Brain from bones of skull (cranial meninges)
 Spinal meninges continuous with cranial meninges
 Have 3 layers:
 Dura (“hard”) mater – outermost covering
 Arachnoid mater – middle layer
 Pia (“delicate”) mater – innermost layer
Gross Anatomy of Spinal Cord and Meninges
 Spinal cord located in vertebral foramen
 Epidural space
 Between vertebra and dura mater
 Contains loose connective tissue, blood vessels, adipose tissue
 Epidural block
 Injection of anesthetic
 Used to control pain
Figure 13–3
Gross Anatomy of Spinal Cord and Meninges
 Dura mater
 Arachnoid mater
 Subarachnoid space
 Between arachnoid membrane and pia mater
 Filled with CSF
 Acts as shock absorber
 Carries dissolved gases, nutrients, chemical messengers, waste products
 Spinal tap
 Withdrawal of CSF for diagnostic purposes when CNS infection suspected, for back pain,
headaches, disc problems, etc.
 Pia mater
Figure 13–3
Meningitis
 Meningitis:
 Viral or bacterial infection of meninges
Sympathetic Chain Ganglia
 String of ganglia alongside spinal cord
Figure 16–5
Sympathetic Chain Ganglia
Figure 16–4a