7
Peripheral Nervous Peripheral Nervous System System Cranial Nerves Cranial Nerves Spinal Nerves Spinal Nerves Reflex Activity Reflex Activity Autonomic Nervous System Autonomic Nervous System General Organization General Organization Exit Exit Home Home BASIM ZWAIN LECTURE NOTES BASIM ZWAIN LECTURE NOTES Somatic Sensory System Somatic Sensory System

Peripheral Nervous System Cranial Nerves Cranial Nerves Spinal Nerves Spinal Nerves Reflex Activity Reflex Activity Autonomic Nervous System Autonomic

Embed Size (px)

Citation preview

Peripheral Nervous SystemPeripheral Nervous System

Cranial NervesCranial Nerves

Spinal NervesSpinal Nerves

Reflex ActivityReflex Activity

Autonomic Nervous SystemAutonomic Nervous System

General OrganizationGeneral Organization

ExitExit HomeHomeBASIM ZWAIN LECTURE NOTESBASIM ZWAIN LECTURE NOTES

Somatic Sensory SystemSomatic Sensory System

BASIM ZWAIN LECTURE NOTESBASIM ZWAIN LECTURE NOTESExitExit HomeHome

General OrganizationGeneral Organization

BackgroundBackground

1. Function1. Functiona. Connect brain with outside worlda. Connect brain with outside world i. CNS function is dependent on information i. CNS function is dependent on information 2. Structural components2. Structural componentsa. Sensory receptorsa. Sensory receptorsb. Peripheral nerves and gangliab. Peripheral nerves and gangliac. Efferent motor endingsc. Efferent motor endings

Sensory receptorsSensory receptorsNature of stimulus detectedNature of stimulus detecteda. Mechanoreceptorsa. Mechanoreceptors i. Touch, vibration, pressure, stretchi. Touch, vibration, pressure, stretchb. Thermoreceptorsb. Thermoreceptors i. Temperature changesi. Temperature changesc. Photoreceptorsc. Photoreceptors i. Light energyi. Light energy ii. Exclusively in the retinaii. Exclusively in the retinad. Chemoreceptorsd. Chemoreceptors i. Chemical in solutioni. Chemical in solutione. Nociceptorse. Nociceptors i. Paini. Pain

LocationLocationa. Exteroceptorsa. Exteroceptors i. Surface of skini. Surface of skinb. Interoceptorsb. Interoceptors i. Visceroceptorsi. Visceroceptors ii. Visceral organs and blood vesselsii. Visceral organs and blood vesselsc. Proprioceptorsc. Proprioceptors i. Musculoskeletal organsi. Musculoskeletal organs

ComplexityComplexitya. Simplea. Simple i. Most sensory receptors (generalized)i. Most sensory receptors (generalized)b. Complexb. Complex i. Special senses (vision, audition,i. Special senses (vision, audition,olfaction, gustation)olfaction, gustation)

Generalized sensory receptorsGeneralized sensory receptors

a. Free dendritic endings (unencapsulated)a. Free dendritic endings (unencapsulated) i. Freei. Free ii. Merkel discsii. Merkel discs iii. Root hair plexusiii. Root hair plexus

b. Encapsulatedb. Encapsulated i. Meisner’s corpuscles—low frequency vibration)i. Meisner’s corpuscles—low frequency vibration) ii. Pacinian corpuscles—high frequencyii. Pacinian corpuscles—high frequency iii. Ruffini’s corpuscles—deep pressureiii. Ruffini’s corpuscles—deep pressure iv. Muscle spindles—muscle stretchiv. Muscle spindles—muscle stretch v. Golgi tendon organs—tendon stretchv. Golgi tendon organs—tendon stretch

NervesNerves

Parallel bundles of peripheral axonsParallel bundles of peripheral axonsa. Enclosed by connective tissuea. Enclosed by connective tissueb. Some may be myelinatedb. Some may be myelinated

Classification based on nature of informationClassification based on nature of informationa. Sensory (afferent) nervesa. Sensory (afferent) nerves i. Sensory information from periphery to CNSi. Sensory information from periphery to CNSb. Motor (efferent) nervesb. Motor (efferent) nerves i. Motor information from CNS to peripheryi. Motor information from CNS to peripheryc. Mixed nervesc. Mixed nerves i. Include sensory and motori. Include sensory and motor

Classification based on site of originClassification based on site of origina. Cranial nervesa. Cranial nerves i. Brain origini. Brain originb. Spinal nervesb. Spinal nerves i. Arise from spinal cordi. Arise from spinal cord

Motor endingsMotor endings

FunctionFunctiona. Activate effectorsa. Activate effectors i. Release of neurotransmitteri. Release of neurotransmitter

TypesTypesa. Neuromuscular junctiona. Neuromuscular junction i. Contact between motor neuron and musclei. Contact between motor neuron and muscle ii. Release AChii. Release AChb. Varicositiesb. Varicosities i. Contact between autonomic motori. Contact between autonomic motorEndings and visceral effectors and organs,Endings and visceral effectors and organs,Smooth and cardiac muscleSmooth and cardiac muscle

BASIM ZWAIN LECTURE NOTESBASIM ZWAIN LECTURE NOTESExitExit HomeHome

Cranial Nerves Cranial Nerves

BASIM ZWAIN LECTURE NOTESBASIM ZWAIN LECTURE NOTES

Spinal Nerves Spinal Nerves

ExitExit HomeHome

NomenclatureNomenclature

Named for the level of the vertebralNamed for the level of the vertebralcolumn from which the nerves exitscolumn from which the nerves exitsa. 31 spinal nervesa. 31 spinal nerves i. 8 cervical (C1 – C8)i. 8 cervical (C1 – C8) ii. 12 Thoracic (T1 – T8)ii. 12 Thoracic (T1 – T8) iii. 5 Lumbar (L1 – L8)iii. 5 Lumbar (L1 – L8) iv. 5 Sacral (S1 – S8)iv. 5 Sacral (S1 – S8) v. 1 Coccygeal (C0) v. 1 Coccygeal (C0)

StructureStructure

1. Dorsal and ventral rootlets1. Dorsal and ventral rootlets2. Dorsal and ventral root2. Dorsal and ventral root3. Dorsal root ganglion3. Dorsal root ganglion4. Spinal nerve4. Spinal nerve5. Dorsal ramus of spinal nerve5. Dorsal ramus of spinal nerve6. Ventral ramus of spinal nerve6. Ventral ramus of spinal nerve7. Rami communicantes7. Rami communicantes a. Autonomic fibersa. Autonomic fibers8. Sympathetic chain ganglion8. Sympathetic chain ganglion

Nerves plexusesNerves plexuses

1. Specific to ventral rami1. Specific to ventral rami2. Types2. Types a. Cervicala. Cervical b. Brachialb. Brachial c. Lumbarc. Lumbar d. Sacral regionsd. Sacral regions

3. Fibers of different ventral rami3. Fibers of different ventral ramicross and are redistributedcross and are redistributed a.Branches contain fibers originatinga.Branches contain fibers originatingfrom different spinal nervesfrom different spinal nerves b.Innervation arrives via multipleb.Innervation arrives via multipleroutesroutes i. More than a single spinal nervei. More than a single spinal nerveserves each limb muscle serves each limb muscle

DermatomesDermatomes

1.1.Area of skin innervated by the Area of skin innervated by the cutaneous branch of a single cutaneous branch of a single spinal nervespinal nerve2. All spinal nerves (except C1)2. All spinal nerves (except C1)Have dermatomesHave dermatomes3. Dermatomes overlap3. Dermatomes overlap

BASIM ZWAIN LECTURE NOTESBASIM ZWAIN LECTURE NOTES

Reflex Activity Reflex Activity

ExitExit HomeHome

BackgroundBackground

1. Stimulus-response sequence1. Stimulus-response sequence a. Unlearneda. Unlearned b. Unpremeditatedb. Unpremeditated c. Involuntaryc. Involuntary2. Mediated by spinal cord circuits2. Mediated by spinal cord circuits a. Information may ultimately a. Information may ultimately relayed to the brainrelayed to the brain

Components of a reflex arcComponents of a reflex arc

1. Receptor (site of stimulus action)1. Receptor (site of stimulus action)2. Sensory neuron (transmits the afferent 2. Sensory neuron (transmits the afferent impulse to the CNS)impulse to the CNS)3. Integration center 3. Integration center a. Monosynaptic reflex (single synapse)a. Monosynaptic reflex (single synapse) b. Polysynaptic (multiple synapses with b. Polysynaptic (multiple synapses with chains of interneurons)chains of interneurons)4. Motor neuron (conducts efferent impulse4. Motor neuron (conducts efferent impulsefrom integration center to effectorfrom integration center to effector5. Effector (muscle fiber or gland)5. Effector (muscle fiber or gland)

Stretch and deep tendon reflexesStretch and deep tendon reflexes

Muscle spindlesMuscle spindles

a. Consist of intrafusal fibersa. Consist of intrafusal fibersb. Wrapped by afferent sensory endingsb. Wrapped by afferent sensory endings i. Type Ia fibersi. Type Ia fibers ii. Type II fibersii. Type II fibersc. Gamma (g) efferent fibersc. Gamma (g) efferent fibers i. Innervate contractile region of spindlei. Innervate contractile region of spindle ii. Maintain spindle sensitivityii. Maintain spindle sensitivity

Extrafusal muscle fibersExtrafusal muscle fibers a. Skeletal musclea. Skeletal muscle b. Innervated by alpha (a) motor b. Innervated by alpha (a) motor neuronsneurons

Sequence of eventsSequence of eventsa. Stretching muscle activates muscle spindlea. Stretching muscle activates muscle spindleb. Impulse carried by primary sensory fiber to b. Impulse carried by primary sensory fiber to spinal cordspinal cordc. Activates alpha motor neuronc. Activates alpha motor neuron i. Sends efferent signal to muscle (effect)i. Sends efferent signal to muscle (effect)d. Stretched muscle contractsd. Stretched muscle contractse. Antagonist muscle is reciprocally inhibitede. Antagonist muscle is reciprocally inhibited

Autonomic Nervous System Autonomic Nervous System

ExitExit HomeHome

Somatic Nervous SystemSomatic Nervous System1. Voluntary1. Voluntary a. Voluntary muscle movementa. Voluntary muscle movement2. Sensory information to the CNS2. Sensory information to the CNS3. Organization of cell bodies3. Organization of cell bodies a. Lie within spinal cord or brainstema. Lie within spinal cord or brainstem b. Targets are controlled monosynapticallyb. Targets are controlled monosynaptically

1.Autonomic Nervous System is involuntary1.Autonomic Nervous System is involuntary(autonomic functions are carried out (autonomic functions are carried out without conscious, voluntary control)without conscious, voluntary control)

2.Cell bodies of all lower autonomic motor 2.Cell bodies of all lower autonomic motor neurons lie outside the CNSneurons lie outside the CNS a. Autonomic gangliaa. Autonomic ganglia b. Neurons are postganglionicb. Neurons are postganglionic c. Driven by preganglionic neurons whose c. Driven by preganglionic neurons whose cell bodies are in the spinal cord or brainstemcell bodies are in the spinal cord or brainstem

3. Divisions3. Divisions a. Sympathetica. Sympathetic b. Parasympatheticb. Parasympathetic

4. Divisions differ based on:4. Divisions differ based on:a. Neurotransmitter typea. Neurotransmitter typeb. Fiber lengthb. Fiber lengthc. Location of gangliac. Location of gangliad. Functiond. Function

5. Neurotransmitter5. Neurotransmitter

Division Preganglionic Postganglionic

Sympathetic ACh NE

Parasympathetic ACh ACh

a. ACh acts locallya. ACh acts locally i. ACh always has a stimulatory effecti. ACh always has a stimulatory effectb. NE has spreads far and can exert its effectsb. NE has spreads far and can exert its effectsover long distances when circulated in the bloodover long distances when circulated in the bloodc. Adrenergic receptorsc. Adrenergic receptors i. Alpha—stimulatoryi. Alpha—stimulatory ii. Beta—inhibitory (except in the heart whenii. Beta—inhibitory (except in the heart whenit is excitatory)it is excitatory)

6. Fiber length6. Fiber lengtha. Parasympathetica. Parasympathetic i. Long preganglionici. Long preganglionic ii. Short postganglionicii. Short postganglionicb. Sympatheticb. Sympathetic i. Short preganglionici. Short preganglionic ii. Long postganglionicii. Long postganglionic

8. Function8. Functiona. Divisions work in concerta. Divisions work in concertb. Parasympathetic disionb. Parasympathetic dision i. Maintenance of functioni. Maintenance of function ii. Energy conservationii. Energy conservationc. Sympathetic divisionc. Sympathetic division i. Emergencei. Emergence ii. Intense muscular activityii. Intense muscular activity

9. Sympathetic response9. Sympathetic response

a. Pupil dilateda. Pupil dilatedb. Secretory responses inhibitedb. Secretory responses inhibitedc. Stimulates sweatingc. Stimulates sweatingd. Heart functiond. Heart function i. Increases ratei. Increases rate ii. Dilates coronary vesselsii. Dilates coronary vessels

e. Increased blood pressuree. Increased blood pressure i. Constricts most vesselsi. Constricts most vesselsf. Bronchioles dilatef. Bronchioles dilateg. Decreased activity of digestive systemg. Decreased activity of digestive systemh. Piloerectionh. Piloerection

i. Increase metabolic ratei. Increase metabolic rate i. Glucose is released into bloodi. Glucose is released into blood ii. Lipolysisii. Lipolysisj. Increased alertnessj. Increased alertnessh. Causes ejaculation (vaginal reverse peristalsis)h. Causes ejaculation (vaginal reverse peristalsis)

10. Parasympathetic response10. Parasympathetic response

a. Pupils constricta. Pupils constrictb. Stimulates secretory activityb. Stimulates secretory activity i. Salivationi. Salivationc. Heart functionc. Heart function i. Decreases ratei. Decreases rate ii. Constricts coronary vesselsii. Constricts coronary vessels

d. Constricts bronchiolesd. Constricts bronchiolese. Increases activity of digestive systeme. Increases activity of digestive systemf. Causes erection (penis and clitoris)f. Causes erection (penis and clitoris) i. Vasodilation i. Vasodilation

BASIM ZWAIN LECTURE NOTESBASIM ZWAIN LECTURE NOTES

ExitExit HomeHomeBASIM ZWAIN LECTURE NOTESBASIM ZWAIN LECTURE NOTES

Somatic Sensory System Somatic Sensory System

BackgroundBackground

Differences between somatic senses andDifferences between somatic senses andother sensesother senses1. Receptors are distributed throughout 1. Receptors are distributed throughout the body as opposed to being concentratedthe body as opposed to being concentratedat small, specialized locationsat small, specialized locations

2. Responds to many kinds of stimuli 2. Responds to many kinds of stimuli (usually mechanical)(usually mechanical)3. At least four senses (temperature, body3. At least four senses (temperature, bodyposition, touch & pain)position, touch & pain)4. Place, pressure, sharpness, texture, and4. Place, pressure, sharpness, texture, andduration can be accurately gaugesduration can be accurately gauges

Types of somatic sensation receptorsTypes of somatic sensation receptors1. Mechanoreceptors--sensitive to physical 1. Mechanoreceptors--sensitive to physical distortiondistortion2. Nociceptors--respond to damaging stimuli2. Nociceptors--respond to damaging stimuli3. Thermoreceptors--sensitive to changes in 3. Thermoreceptors--sensitive to changes in temperaturetemperature4. Proprioceptors--monitor body position4. Proprioceptors--monitor body position5. Chemoreceptors--respond to certain 5. Chemoreceptors--respond to certain chemicalschemicals

ClassificationClassification1. Free nerve endings1. Free nerve endingsa. Nociceptorsa. Nociceptorsb. Thermoreceptorsb. Thermoreceptors2. Encapsulated2. Encapsulateda. Most cutaneous receptorsa. Most cutaneous receptors

Mechanism of functionMechanism of function1. Stimuli applied to skin deform or change 1. Stimuli applied to skin deform or change receptorreceptora. Alters the ionic permeability of the receptor a. Alters the ionic permeability of the receptor creating generator potentialscreating generator potentialsi. Trigger action potentialsi. Trigger action potentials

Mechanical SensesMechanical Senses

Mechanical energyMechanical energy1. Easily differentiated1. Easily differentiateda.a.Stimulus frequencyStimulus frequencyb. Stimulus pressureb. Stimulus pressurec. Receptive fieldc. Receptive field

Types of receptorsTypes of receptors

1. Mechanoreceptors1. Mechanoreceptors

a.a.Pacinian (sensitive Pacinian (sensitive toto vibration (250-350 Hz), vibration (250-350 Hz),involved in fine discrimination of texture orinvolved in fine discrimination of texture orother moving stimuli that cause vibrations other moving stimuli that cause vibrations b. Meissner's corpuscle (most common b. Meissner's corpuscle (most common receptor in glabrous skin (smooth, hairless),receptor in glabrous skin (smooth, hairless),sensitive to vibration (sensitive to vibration (low frequencylow frequency, 30-50 Hz), 30-50 Hz)

c. Ruffini's ending-not well understoodc. Ruffini's ending-not well understoodd. Mercel's disks (light pressure and d. Mercel's disks (light pressure and Tactile discriminationTactile discriminatione. Hair follicle receptore. Hair follicle receptor

2. Nociceptors2. Nociceptorsa. Free, unmyelinated nerve endingsa. Free, unmyelinated nerve endingsb. Signal that body tissue is being damagedb. Signal that body tissue is being damagedc. In most tissues, not brainc. In most tissues, not braind. Types of damage detectedd. Types of damage detected i. Mechanical--i. Mechanical--strong pressurestrong pressure (sharp objects) (sharp objects) ii. Thermal (different from temperature)--ii. Thermal (different from temperature)--Active when tissues begin to be destroyedActive when tissues begin to be destroyed iii. Chemical--environmental agents or those iii. Chemical--environmental agents or those from tissues itself--pH, histamine, etc.from tissues itself--pH, histamine, etc.

3. Thermoreceptors3. Thermoreceptorsa. Brain temperature is tightly regulateda. Brain temperature is tightly regulated(close to 37C, brain function changes above(close to 37C, brain function changes aboveand below that temperature)and below that temperature)b. Specialized receptors that can perceive b. Specialized receptors that can perceive changes in temperature as small as 0.01C.changes in temperature as small as 0.01C.c. Two types (warm--begin firing at 30C-45C c. Two types (warm--begin firing at 30C-45C (above causes damage and pain) & cold--(above causes damage and pain) & cold--below 35C to 10C)below 35C to 10C)

Note: Like other sensory receptors, Note: Like other sensory receptors, temperature receptors adapt. They respond to temperature receptors adapt. They respond to sudden changes in temperature.sudden changes in temperature.

Experiment--three beakers of water: one cold, one Experiment--three beakers of water: one cold, one hot, one lukewarm. One finger from one hand into hot, one lukewarm. One finger from one hand into hot; one finger from the other hand into cold. After hot; one finger from the other hand into cold. After some time period, immerse both simultaneously into some time period, immerse both simultaneously into the lukewarm. The finger from the hot senses the the lukewarm. The finger from the hot senses the water to be cold and the finger from the cold senses water to be cold and the finger from the cold senses the same water to be hot. Why? Adaptation--the hot the same water to be hot. Why? Adaptation--the hot and cold receptors adapted (stopped firing). When and cold receptors adapted (stopped firing). When immersed in lukewarm, only the unadapted immersed in lukewarm, only the unadapted receptors were available. You need both to sense receptors were available. You need both to sense lukewarm, etc.lukewarm, etc.

4. Proprioceptors4. Proprioceptorsa. Body positiona. Body position i. Where the body isi. Where the body is ii. Direction of movementii. Direction of movement iii. Speed of movementiii. Speed of movementb. Receptors in the skeletal muscles (more in b. Receptors in the skeletal muscles (more in movement lecture)movement lecture)

c. Two different mechanosensitive c. Two different mechanosensitive proprioceptors:proprioceptors: i. Muscle spindles-consist of specialized i. Muscle spindles-consist of specialized intrafusal muscle fibers distributed among intrafusal muscle fibers distributed among ordinary (extrafusal) muscle fibers; detect ordinary (extrafusal) muscle fibers; detect changes in muscle lengthchanges in muscle length ii. Golgi tendon organs-distributed among ii. Golgi tendon organs-distributed among collagen fibers in tendons and detects collagen fibers in tendons and detects changes in muscle tensionchanges in muscle tension

Organization of Somatic Sensory InformationOrganization of Somatic Sensory Information

Spinal segmentsSpinal segments1. 30 spinal segments consisting of paired 1. 30 spinal segments consisting of paired dorsal and ventral rootsdorsal and ventral roots2. Spinal segments are divided into 4 groups: 2. Spinal segments are divided into 4 groups: cervical, thoracic, lumbar, sacralcervical, thoracic, lumbar, sacral3. Each segment is named after vertebra from 3. Each segment is named after vertebra from which nerves emerge (cervical: C1 - C8, which nerves emerge (cervical: C1 - C8, thoracic: T1 - T12, lumbar: L1 - L5 & sacral: S1 thoracic: T1 - T12, lumbar: L1 - L5 & sacral: S1 - S5)- S5)

DermatomesDermatomes 1. Segmental organization of spinal nerves & 1. Segmental organization of spinal nerves & sensory innervation of skin are relatedsensory innervation of skin are related2. Area of skin innervated by the dorsal roots 2. Area of skin innervated by the dorsal roots of a single spinal segment is a dermatomeof a single spinal segment is a dermatome

3. Characteristics3. Characteristicsa. Overlap between the dermatomesa. Overlap between the dermatomesb. Cervical b. Cervical dermatomes: dermatomes: above the sternumabove the sternumc.Thoracic c.Thoracic dermatomes: top ofdermatomes: top of sternum to waist sternum to waistd.Lumbar dermatomes: d.Lumbar dermatomes: front of front of legs &stomachlegs &stomache.Sacral dermatomes (back of legs & genitals)e.Sacral dermatomes (back of legs & genitals)

Somatic Sensory PathwaysSomatic Sensory Pathways

Two basic systemsTwo basic systems1. Pain and temperature1. Pain and temperature2. Touch and Proprioception2. Touch and Proprioception

PathwaysPathways1. Dorsal column-medial 1. Dorsal column-medial lemniscal pathway DCMLlemniscal pathway DCMLa. Touch and proprioceptiona. Touch and proprioception2. Spinothalamic pathway ST2. Spinothalamic pathway STa. Pain and temperaturea. Pain and temperature

DCML PathwayDCML Pathway1. In the DCML pathway information ascends 1. In the DCML pathway information ascends through the dorsal column on the ipsilateral through the dorsal column on the ipsilateral side of the spinal cordside of the spinal cord2. Synapses in the medulla2. Synapses in the medulla3. Crosses over and ascends via the medial 3. Crosses over and ascends via the medial lemniscus to the thalamus (VP)lemniscus to the thalamus (VP)4. Synapses in VP thalamus4. Synapses in VP thalamus5. Projects to the cortex5. Projects to the cortex

ST PathwayST Pathway1. Information crosses to the contralateral 1. Information crosses to the contralateral side in the spinal cordside in the spinal cord2. Ascends via the spinothalamic tract2. Ascends via the spinothalamic tract3. Synapses in the thalamus (VP)3. Synapses in the thalamus (VP)4. Projects to the cortex.4. Projects to the cortex.

Information carried in each pathway remains Information carried in each pathway remains separateseparate1. Segregated all the way to the cortex1. Segregated all the way to the cortex2. Thalamus2. Thalamusa. Ventral posterior (VP) nucleus receives the a. Ventral posterior (VP) nucleus receives the information and projects to the information and projects to the somatosensory cortexsomatosensory cortex

Somatosensory CortexSomatosensory Cortex

AnatomyAnatomy1. Parietal lobe1. Parietal lobea. Post-central gyrusa. Post-central gyrus i. Most complex processing occurs in cortexi. Most complex processing occurs in cortex

Somatotopy Somatotopy 1. Mapping of the body's surface sensations onto a 1. Mapping of the body's surface sensations onto a brain structurebrain structure2. Features of the map: a. Not continuous, b. Not 2. Features of the map: a. Not continuous, b. Not scaled to the human body, c. Relative size of the scaled to the human body, c. Relative size of the cortex devoted to each body part is correlated with cortex devoted to each body part is correlated with the density of sensory input (i.e., lips versus the skin the density of sensory input (i.e., lips versus the skin on your calf) & d. Size is related to importance of the on your calf) & d. Size is related to importance of the sensory input (i.e., finger tip versus elbow)sensory input (i.e., finger tip versus elbow)

Posterior parietal lobePosterior parietal lobe1. Primary somatosensory cortex receives 1. Primary somatosensory cortex receives simple segregated streams of sensory simple segregated streams of sensory informationinformation2. Integration takes place in the posterior 2. Integration takes place in the posterior parietal cortexparietal cortex

Pain and Its ControlPain and Its Control

NociceptionNociception1. Sensory process that provides signals that 1. Sensory process that provides signals that trigger paintrigger pain

CharacteristicsCharacteristics1. Pain is influenced cognitively1. Pain is influenced cognitively2. Hyperalgesia2. Hyperalgesiaa. Tissue already damaged is much more a. Tissue already damaged is much more sensitive to painsensitive to pain i. Nociceptors are sensitized by various i. Nociceptors are sensitized by various substances released by damaged tissue substances released by damaged tissue (protaglandins, histamines, etc.)(protaglandins, histamines, etc.)

Regulation of painRegulation of pain1. Pain can be modified by non-painful 1. Pain can be modified by non-painful sensory input (i.e., rub the skin around a sensory input (i.e., rub the skin around a bruise)bruise)a. Gate Theory of Pain-circuit in spinal cord a. Gate Theory of Pain-circuit in spinal cord dorsal rootdorsal root

2. Several brain regions can suppress pain2. Several brain regions can suppress paina. PAG (periacqueductal gray matter) project a. PAG (periacqueductal gray matter) project to the raphe (serotonin) that sends axons to to the raphe (serotonin) that sends axons to the spinal cord (5-HT is inhibitory, block the spinal cord (5-HT is inhibitory, block synaptic activity)synaptic activity)

3. Brain chemicals3. Brain chemicalsa. Endorphinsa. Endorphins i. Share many opioid properties and bind to i. Share many opioid properties and bind to opioid receptors in the brainopioid receptors in the brain ii. Opioid receptors are throughout body, but ii. Opioid receptors are throughout body, but especially in brain and particularly in brain especially in brain and particularly in brain areas that process and modulate nociceptive areas that process and modulate nociceptive information (PA, raphe, and spinal cord)information (PA, raphe, and spinal cord)