Anatomy of AcupunctureAnatomy of Acupuncture

Important Pathways for Pain Important Pathways for Pain Control & Acupuncture ReliefControl & Acupuncture Relief

Spinal CordSpinal CordA. Spinal cord anatomyA. Spinal cord anatomy

1. Protection and coverings1. Protection and coverings a. Vertebral columna. Vertebral column b. Meningesb. Meninges 2. External anatomy of the spinal cord2. External anatomy of the spinal cord 3. Internal anatomy of the spinal cord3. Internal anatomy of the spinal cord

B. Spinal cord physiologyB. Spinal cord physiology 1. Reflexes1. Reflexes 2. Reflex arc and homeostasis2. Reflex arc and homeostasis a. Physiology of the stretch reflexa. Physiology of the stretch reflex b. Physiology of the flexor (withdrawal)b. Physiology of the flexor (withdrawal) reflex and crossed extensor reflexesreflex and crossed extensor reflexes

C. Spinal nervesC. Spinal nerves 1. Composition and coverings1. Composition and coverings 2. Distribution of spinal nerves2. Distribution of spinal nerves 3. Dermatomes3. Dermatomes

The Spinal CordThe Spinal Cord1. is continuous with brain1. is continuous with brain

2. mediates spinal reflexes2. mediates spinal reflexes

3. is site for integration3. is site for integration

4. provides the pathways4. provides the pathways

Protection and CoveringsProtection and Coverings1. vertebral canal1. vertebral canal

2. meninges2. meninges

3. cerebrospinal fluid3. cerebrospinal fluid

Meninges and SpacesMeninges and Spaces

1. epidural space1. epidural space

2. dura mater2. dura mater

3. subdural space3. subdural space

4. arachnoid membrane4. arachnoid membrane

5. subarachnoid space5. subarachnoid space

6. pia mater6. pia mater

-- denticulate ligaments-- denticulate ligaments

External AnatomyExternal Anatomy

1. cylindrical1. cylindrical2. flattened A-P2. flattened A-P3. foramen magnum to L23. foramen magnum to L24. differential growth4. differential growth5. cervical enlargement5. cervical enlargement6. lumbar enlargement6. lumbar enlargement7. conus medullaris7. conus medullaris8. filum terminale8. filum terminale9. cauda equina9. cauda equina10. functional segments10. functional segments

Internal AnatomyInternal Anatomy

1. gray matter1. gray matter

2. white matter2. white matter

3. gray commissure3. gray commissure

4. central canal4. central canal

1. gray matter1. gray matter

2. white matter2. white matter

3. gray commissure3. gray commissure

4. central canal4. central canal

Gray MatterGray Matter

1. nuclei1. nuclei

2. horns2. horns

a. dorsal -- sensorya. dorsal -- sensory

b. ventral -- motorb. ventral -- motor

c. lateral -- autonomicc. lateral -- autonomic

Spinal Cord Grey MatterSpinal Cord Grey Matter

Spinal LayersSpinal Layers◦ Spinal grey matters Spinal grey matters

divided into 10 layersdivided into 10 layers

Substantia GelatinosaSubstantia Gelatinosa◦ Composed of a layer of cell Composed of a layer of cell

bodies running up and down bodies running up and down the dorsal horns of the spinal the dorsal horns of the spinal cordcord

◦ Receive input from A and C-Receive input from A and C-fibersfibers

◦ Activity in SG inhibits pain Activity in SG inhibits pain transmissiontransmission

Spinal Nerve RootsSpinal Nerve Roots1. dorsal root (axons of sensory neurons)1. dorsal root (axons of sensory neurons)

-- dorsal root ganglion (cell bodies of sensory -- dorsal root ganglion (cell bodies of sensory neurons)neurons)

2. ventral root (axons of motor neurons)2. ventral root (axons of motor neurons)

Dorsal root ganglion

Dorsal roots

Ventral roots

White MatterWhite Matter

1. columns1. columns

a. anteriora. anterior

b. posteriorb. posterior

c. lateralc. lateral

2. tracts2. tracts

a. ascendinga. ascending

b. descendingb. descending

Posterior columns

Anterior columns

Lateral columns

Lateral columns

Tracts of the Spinal CordTracts of the Spinal Cord

The Spinal Cord Has Two Essential The Spinal Cord Has Two Essential FunctionsFunctions

1. convey impulses between the periphery 1. convey impulses between the periphery and the brainand the brain

2. provide integrating centers for spinal 2. provide integrating centers for spinal reflexesreflexes

Reflexes are…Reflexes are…

1. inborn1. inborn

2. unlearned2. unlearned

3. unconscious3. unconscious

Somatic Reflexes Versus Visceral Somatic Reflexes Versus Visceral ReflexesReflexes

Somatic reflexes involve the somatic Somatic reflexes involve the somatic nervous system.nervous system.

Visceral reflexes involve the autonomic Visceral reflexes involve the autonomic nervous system.nervous system.

Reflex ArcReflex Arc

1. receptor1. receptor

2. sensory neuron2. sensory neuron

3. integration center3. integration center

4. motor neuron4. motor neuron

5. effector5. effector

sensory receptor

1

2

3

4

5

sensory (afferent) neuron

center of integration with association neuron

motor (efferent) neuron

effector

sensory receptor

2

3

4

5

sensory (afferent) neuron

center of integration with association neuron

motor (efferent) neuron

effector

THE REFLEX ARC AS A FEEDBACK SYSTEM

CONTROLLED CONDITION

A stimulus or stress disrupts membrane homeostasis by altering some controlled

condition

RECEPTORThe receptors in a reflex are sensory

neurons associated with a receptor device (transducer) and which relay nerve impulses to a central control center

CONTROL CENTERThe control center is an integrating center

of neurons in the CNS. It relays the information to motor neurons

EFFECTORSThe motor neurons initiate some response

by an effector (muscle or gland) to counteract the stimulus that originally

disrupted homeostasis

RETURN TO HOMEOSTASISThe action of the effector returns the

body process to within its normal homeostatic range

Stretch ReflexStretch Reflex

1. monosynaptic1. monosynaptic

2. muscle spindle2. muscle spindle

3. muscle tone3. muscle tone

4. ipsilateral4. ipsilateral

5. reciprocal innervation5. reciprocal innervation

The Flexor and Crossed Extensor ReflexThe Flexor and Crossed Extensor Reflex

IntersegmentalPolysynapticContralateral Pain receptorRole of association neuronsReciprocal innervationexcitatory neurons

inhibitory neurons

IntersegmentalPolysynapticIpsilateral Pain receptorRole of association neuronsReciprocal innervation

The Nervous System and Pain The Nervous System and Pain

Pain Pathways – Going UpPain Pathways – Going Up

Pain information travels Pain information travels up the spinal cord through up the spinal cord through the spinothalamic track (2 the spinothalamic track (2 parts)parts)– PSTT PSTT

Immediate warning of Immediate warning of the presence, location, the presence, location, and intensity of an and intensity of an injuryinjury

– NSTTNSTTSlow, aching reminder Slow, aching reminder that tissue damage has that tissue damage has occurredoccurred

Pain Pathways – Going DownPain Pathways – Going Down

Descending pain Descending pain pathway pathway responsible for pain responsible for pain inhibitioninhibition

The Neurochemicals of Pain The Neurochemicals of Pain

Pain InitiatorsPain Initiators◦Glutamate - CentralGlutamate - Central◦Substance P - CentralSubstance P - Central◦Brandykinin - PeripheralBrandykinin - Peripheral◦Prostaglandins - PeripheralProstaglandins - Peripheral

Pain InhibitorsPain Inhibitors◦SerotoninSerotonin◦EndorphinsEndorphins◦EnkephalinsEnkephalins◦DynorphinDynorphin

Theories of Pain Theories of Pain

Specificity TheorySpecificity Theory– Began with AristotleBegan with Aristotle– Pain is hardwiredPain is hardwired

Specific “pain” fibers bring info to a “pain center”Specific “pain” fibers bring info to a “pain center”

– Refuted in 1965Refuted in 1965

Gate Control TheoryGate Control Theory

Gate-Control Theory – Gate-Control Theory – Ronald Melzack (1960s)Ronald Melzack (1960s)

Described physiological mechanism by Described physiological mechanism by which psychological factors can affect the which psychological factors can affect the experience of pain.experience of pain.

Neural gate can open and close thereby Neural gate can open and close thereby modulating pain.modulating pain.

Gate is located in the spinal cord.Gate is located in the spinal cord.– It is the SGIt is the SG

Opening and Closing the GateOpening and Closing the Gate

When the gate is closed signals from small When the gate is closed signals from small diameter pain fibres do not excite the diameter pain fibres do not excite the dorsal horn transmission neurons.dorsal horn transmission neurons.

When the gate is open pain signals excite When the gate is open pain signals excite dorsal horn transmission cellsdorsal horn transmission cells

Three Factors Involved in Opening Three Factors Involved in Opening and Closing the Gateand Closing the Gate

The amount of activity in the pain fibers.The amount of activity in the pain fibers.

The amount of activity in other peripheral The amount of activity in other peripheral fibers.fibers.

Messages that descend from the brain.Messages that descend from the brain.

Conditions that Open the GateConditions that Open the Gate

Physical conditionsPhysical conditions– Extent of injuryExtent of injury– Inappropriate activity levelInappropriate activity level

Emotional conditionsEmotional conditions– Anxiety or worryAnxiety or worry– TensionTension– DepressionDepression

Mental ConditionsMental Conditions– Focusing on painFocusing on pain– BoredomBoredom

Conditions That Close the GateConditions That Close the Gate

Physical conditionsPhysical conditions– MedicationsMedications

– Counter stimulation (e.g., heat, massage)Counter stimulation (e.g., heat, massage)

Emotional conditionsEmotional conditions– Positive emotionsPositive emotions

– Relaxation, RestRelaxation, Rest

Mental conditionsMental conditions– Intense concentration or distractionIntense concentration or distraction

– Involvement and interest in life activitiesInvolvement and interest in life activities

Mechanisms that Regulate APMechanisms that Regulate AP

Inhibitor of APInhibitor of AP– CholecytokininCholecytokinin

Enhancer of APEnhancer of AP– L-phenylalanineL-phenylalanine

ConclusionConclusion

Knowledge of the functional anatomy of Knowledge of the functional anatomy of the nervous system may be useful in the nervous system may be useful in determining how acupuncture works since determining how acupuncture works since all evidence suggests that the effects all evidence suggests that the effects acupuncture can be explained only by its acupuncture can be explained only by its affects on the nervous system.affects on the nervous system.