Spinal Cord
A. Spinal cord anatomy
1. Protection and coverings
a. Vertebral column
b. Meninges
2. External anatomy of the spinal cord
3. Internal anatomy of the spinal cord
B. Spinal cord physiology
1. Reflexes
2. Reflex arc and homeostasis
a. Physiology of the stretch reflex
b. Physiology of the flexor (withdrawal)
reflex and crossed extensor reflexes
C. Spinal nerves
1. Composition and coverings
2. Distribution of spinal nerves
3. Dermatomes
The Spinal Cord
1.
2.
3.
4.
is continuous with brain
mediates spinal reflexes
is site for integration
provides the pathways
Protection and Coverings
1. vertebral canal
2. meninges
3. cerebrospinal fluid
Meninges and Spaces
1. epidural space
2. dura mater
3. subdural space
4. arachnoid membrane
5. subarachnoid space
6. pia mater
-- denticulate ligaments
External Anatomy
1. cylindrical
2. flattened A-P
3. foramen magnum to L2
4. differential growth
5. cervical enlargement
6. lumbar enlargement
7. conus medullaris
8. filum terminale
9. cauda equina
10. functional segments
GROSS ANATOMY OF THE SPINAL CORD
Internal Anatomy
1.
2.
3.
4.
gray matter
white matter
gray commissure
central canal
Gray Matter
1. nuclei
2. horns
a. dorsal -- sensory
b. ventral -- motor
c. lateral -- autonomic
Spinal Nerve Roots
1. dorsal root (axons of sensory neurons)
-- dorsal root ganglion (cell bodies of sensory
neurons)
2. ventral root (axons of motor neurons)
Dorsal roots
Dorsal root ganglion
Ventral roots
White Matter
1. columns
a. anterior
b. posterior
c. lateral
2. tracts
a. ascending
b. descending
Posterior columns
Lateral columns
Lateral columns
Anterior columns
Tracts of the Spinal Cord
Terminology Review
The Spinal Cord Has Two Essential
Functions
1. convey impulses between the periphery
and the brain
2. provide integrating centers for spinal
reflexes
Reflexes are…
1. inborn
2. unlearned
3. unconscious
Somatic Reflexes Versus Visceral
Reflexes
Somatic reflexes involve the somatic
nervous system.
Visceral reflexes involve the autonomic
nervous system.
Reflex Arc
1
3
1.
2.
3.
4.
5.
receptor
sensory neuron
integration center
motor neuron
effector
sensory receptor
center of integration with
association neuron
3
center of integration with
association neuron
2
sensory (afferent) neuron sensory receptor
2
sensory (afferent) neuron
motor (efferent) neuron
4
motor (efferent) neuron
effector
4
5
effector
5
THE REFLEX ARC AS A FEEDBACK SYSTEM
CONTROLLED CONDITION
A stimulus or stress disrupts membrane
homeostasis by altering some controlled
condition
RETURN TO HOMEOSTASIS
The action of the effector returns the
body process to within its normal
homeostatic range
RECEPTOR
The receptors in a reflex are sensory
neurons associated with a receptor device
(transducer) and which relay nerve
impulses to a central control center
CONTROL CENTER
The control center is an integrating center
of neurons in the CNS. It relays the
information to motor neurons
EFFECTORS
The motor neurons initiate some response
by an effector (muscle or gland) to
counteract the stimulus that originally
disrupted homeostasis
Reflex arc
Stretch Reflex
1.
2.
3.
4.
5.
monosynaptic
muscle spindle
muscle tone
ipsilateral
reciprocal innervation
The Flexor and Crossed Extensor Reflex
Intersegmental
Polysynaptic
Ipsilateral
Pain receptor
Role of association neurons
Reciprocal innervation
Intersegmental
Polysynaptic
Contralateral
Pain receptor
Role of association
neurons
Reciprocal innervation
excitatory neurons
inhibitory neurons