Download AP-Anatomy

Anatomy of Acupuncture
Important Pathways for Pain
Control & Acupuncture Relief
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
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 Cord Grey Matter
 Spinal Layers
◦ Spinal grey matters
divided into 10 layers
 Substantia Gelatinosa
◦ Composed of a layer of cell
bodies running up and down
the dorsal horns of the spinal
cord
◦ Receive input from A and Cfibers
◦ Activity in SG inhibits pain
transmission
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
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.
2.
3.
4.
5.
receptor
sensory neuron
integration center
motor neuron
effector
1
3
sensory receptor
center of integration with
association neuron
3
2
sensory (afferent) neuronsensory receptor
center of integration with
association neuron
2
sensory (afferent) neuron
motor (efferent) neuron
4
motor (efferent) neuron
effector
5
4
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
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
The Nervous System and Pain
Somatosensory
System
Brain
Spinal Cord
PNS
Somatosensory
Cortex
Dorsal Horn
Ventral Root
Afferent Neuron
Efferent Neuron
Thalamus
A-delta Fibers
C-Fibers
Pain Pathways – Going Up
Pain information travels
up the spinal cord through
the spinothalamic track (2
parts)
– PSTT
Immediate warning of
the presence, location,
and intensity of an
injury
– NSTT
Slow, aching reminder
that tissue damage has
occurred
Pain Pathways – Going Down
Descending pain
pathway
responsible for pain
inhibition
The Neurochemicals of Pain
 Pain Initiators
◦ Glutamate - Central
◦ Substance P - Central
◦ Brandykinin - Peripheral
◦ Prostaglandins - Peripheral
 Pain Inhibitors
◦ Serotonin
◦ Endorphins
◦ Enkephalins
◦ Dynorphin
Theories of Pain
Specificity Theory
– Began with Aristotle
– Pain is hardwired
Specific “pain” fibers bring info to a “pain center”
– Refuted in 1965
Gate Control Theory
Gate-Control Theory –
Ronald Melzack (1960s)
Described physiological mechanism by
which psychological factors can affect the
experience of pain.
Neural gate can open and close thereby
modulating pain.
Gate is located in the spinal cord.
– It is the SG
Opening and Closing the Gate
When the gate is closed signals from small
diameter pain fibres do not excite the
dorsal horn transmission neurons.
When the gate is open pain signals excite
dorsal horn transmission cells
Three Factors Involved in Opening
and Closing the Gate
The amount of activity in the pain fibers.
The amount of activity in other peripheral
fibers.
Messages that descend from the brain.
Conditions that Open the Gate
Physical conditions
– Extent of injury
– Inappropriate activity level
Emotional conditions
– Anxiety or worry
– Tension
– Depression
Mental Conditions
– Focusing on pain
– Boredom
Conditions That Close the Gate
Physical conditions
– Medications
– Counter stimulation (e.g., heat, massage)
Emotional conditions
– Positive emotions
– Relaxation, Rest
Mental conditions
– Intense concentration or distraction
– Involvement and interest in life activities
Mechanisms that Regulate AP
Inhibitor of AP
– Cholecytokinin
Enhancer of AP
– L-phenylalanine
Conclusion
Knowledge of the functional anatomy of
the nervous system may be useful in
determining how acupuncture works since
all evidence suggests that the effects
acupuncture can be explained only by its
affects on the nervous system.