Chapter 2Chapter 2

The Nervous SystemThe Nervous System

OverviewOverview

The human nervous system is an The human nervous system is an extremely complex entity that extremely complex entity that performs a multitude of functions, performs a multitude of functions, in much the same way as a in much the same way as a dynamic network of dynamic network of interconnected computersinterconnected computers

ANATOMYANATOMY

Nervous systemNervous system

The nervous system can be divided The nervous system can be divided into two anatomical divisionsinto two anatomical divisions, each , each with their own subdivisions:with their own subdivisions:– Central nervous system (CNS)Central nervous system (CNS)

BrainBrain Spinal cordSpinal cord

– Peripheral nervous system (PNS)Peripheral nervous system (PNS) Cranial nervesCranial nerves Spinal nervesSpinal nerves

NerveNerve

The nerve cell, or neuron, is the The nerve cell, or neuron, is the functional unit of the nervous functional unit of the nervous systemsystem

There are four functional parts to There are four functional parts to each nerve:each nerve:– Dendrite Dendrite – AxonAxon– Cell bodyCell body– Axon terminalAxon terminal

Central Nervous Central Nervous SystemSystem Spinal cord - Spinal cord - participates directly participates directly

with the control of body with the control of body movements, the processing and movements, the processing and transmission of sensory transmission of sensory information from the trunk and information from the trunk and limbs, and the regulation of limbs, and the regulation of visceral functionsvisceral functions

Brain – central processorBrain – central processor

MeningesMeninges

Three membranes, or meninges, Three membranes, or meninges, envelop the structures of the CNS: envelop the structures of the CNS: – The dura. The outermost and strongest of The dura. The outermost and strongest of

the layers the layers – The arachnoid. A thin and delicate The arachnoid. A thin and delicate

avascular layer avascular layer – The pia. Conveys the blood vessels that The pia. Conveys the blood vessels that

supply the spinal cord, and has a series of supply the spinal cord, and has a series of lateral specializations, the denticulate lateral specializations, the denticulate (dentate) ligaments (dentate) ligaments

Peripheral Nervous Peripheral Nervous System System Somatic NervesSomatic Nerves

– Consists of the cranial nerves and Consists of the cranial nerves and the spinal nervesthe spinal nerves

Cranial NervesCranial Nerves

The cranial nerves (CN) are The cranial nerves (CN) are typically described as comprising typically described as comprising 12 pairs, which are referred to by 12 pairs, which are referred to by the Roman numerals I through XIIthe Roman numerals I through XII

CN I (olfactory) and II (optic) are CN I (olfactory) and II (optic) are not true nerves but are fiber not true nerves but are fiber tracts of the braintracts of the brain

Cranial nervesCranial nerves

CN I – OlfactoryCN I – Olfactory. . The olfactory The olfactory nerve is responsible for the sense nerve is responsible for the sense of smellof smell

CN II – Optic. The optic nerve is CN II – Optic. The optic nerve is responsible for visionresponsible for vision

Cranial nervesCranial nerves

CN III – OculomotorCN III – Oculomotor– The somatic portion supplies the levator The somatic portion supplies the levator

palpabrae superioris muscle, the superior, palpabrae superioris muscle, the superior, medial and inferior rectus muscles, and medial and inferior rectus muscles, and the inferior oblique muscles. These the inferior oblique muscles. These muscles are responsible for some eye muscles are responsible for some eye movements.movements.

– The visceral efferent portion of this nerve The visceral efferent portion of this nerve innervates two smooth intraocular innervates two smooth intraocular muscles: the ciliary and the constrictor muscles: the ciliary and the constrictor pupillae. These muscles are responsible pupillae. These muscles are responsible for papillary constriction.for papillary constriction.

Cranial nervesCranial nerves

CN IV – TrochlearCN IV – Trochlear. . Supplies the Supplies the superior oblique musclesuperior oblique muscle

CN VI – AbducensCN VI – Abducens. . Supplies the Supplies the lateral rectus musclelateral rectus muscle

Cranial nervesCranial nerves

CN V – TrigeminalCN V – Trigeminal. . Maxillary, ophthalmic and Maxillary, ophthalmic and mandibular branches. Ophthalmic and mandibular branches. Ophthalmic and maxillary are exclusively sensory, the latter maxillary are exclusively sensory, the latter supplying the soft and hard palate, maxillary supplying the soft and hard palate, maxillary sinuses, upper teeth and upper lip and the sinuses, upper teeth and upper lip and the mucous membrane of the pharynx. The mucous membrane of the pharynx. The mandibular branch carries sensory mandibular branch carries sensory information but also represents the motor information but also represents the motor component of the nerve, supplying the component of the nerve, supplying the muscles of mastication, both pterygoids, the muscles of mastication, both pterygoids, the anterior belly of digastric, tensor tympani, anterior belly of digastric, tensor tympani, tensor veli palatini and mylohyoid.tensor veli palatini and mylohyoid.

Cranial nervesCranial nerves

CN VII – FacialCN VII – Facial. . Comprised of a Comprised of a sensory (intermediate) root, sensory (intermediate) root, which conveys taste, and a motor which conveys taste, and a motor root, the facial nerve proper, root, the facial nerve proper, which supplies the muscles of which supplies the muscles of facial expression, the platysma facial expression, the platysma muscle, and the stapedius muscle muscle, and the stapedius muscle of the inner earof the inner ear

Cranial nervesCranial nerves

CN VIII – Vestibulocochlear. CN VIII – Vestibulocochlear. Subserves two different senses – Subserves two different senses – balance and hearing balance and hearing

CN IX – Glossopharyngeal. CN IX – Glossopharyngeal. Contains somatic motor, visceral Contains somatic motor, visceral efferent, visceral sensory, and efferent, visceral sensory, and somatic sensory fibers somatic sensory fibers

Cranial nervesCranial nerves

CN X – Vagus. Contains somatic CN X – Vagus. Contains somatic motor, visceral efferent, visceral motor, visceral efferent, visceral sensory, and somatic sensory sensory, and somatic sensory fibers fibers

CN XI – Accessory. Cranial and CN XI – Accessory. Cranial and spinal component spinal component

CN XII – HypoglossalCN XII – Hypoglossal. . The motor The motor nerve of the tonguenerve of the tongue

The Spinal NervesThe Spinal Nerves

A total of 31 symmetrically arranged pairsA total of 31 symmetrically arranged pairs– Divided topographically into 8 cervical pairs (C Divided topographically into 8 cervical pairs (C

1-8), 12 thoracic pairs (T 1-12), 5 lumbar pairs 1-8), 12 thoracic pairs (T 1-12), 5 lumbar pairs (L 1-5), 5 sacral pairs (S 1-5), and a coccygeal (L 1-5), 5 sacral pairs (S 1-5), and a coccygeal pairpair

Peripheral nerves are enclosed in three Peripheral nerves are enclosed in three layers of tissue of differing character. layers of tissue of differing character. From the inside outward, these are the From the inside outward, these are the endoneurium, perineurium, and endoneurium, perineurium, and epineurium epineurium

Cervical NervesCervical Nerves

The 8 pairs of cervical nerves are The 8 pairs of cervical nerves are derived from cord segments derived from cord segments between the level of the foramen between the level of the foramen magnum and the middle of the magnum and the middle of the seventh cervical vertebraseventh cervical vertebra– Divide into a larger ventral ramus, Divide into a larger ventral ramus,

and a smaller dorsal ramus and a smaller dorsal ramus

Cervical PlexusCervical Plexus

Sensory branchesSensory branches– The small occipital nerve (C 2, 3)The small occipital nerve (C 2, 3)– The great auricular nerve (C 2, 3)The great auricular nerve (C 2, 3)– The cervical cutaneous nerve (cutaneous The cervical cutaneous nerve (cutaneous

coli) (C 2, 3)coli) (C 2, 3)– Supraclavicular branches (C 3, 4)Supraclavicular branches (C 3, 4)

Communication branchesCommunication branches– Ansa cervicalisAnsa cervicalis

Muscular branchesMuscular branches

Brachial PlexusBrachial Plexus

Arises from the anterior primary Arises from the anterior primary divisions of the fifth cervical divisions of the fifth cervical through the first thoracic nerve through the first thoracic nerve roots, with occasional roots, with occasional contributions from the fourth contributions from the fourth cervical and second thoracic rootscervical and second thoracic roots

Plexus RootsPlexus Roots

The roots of the plexus, which The roots of the plexus, which consist of C 5 and C 6, join to form consist of C 5 and C 6, join to form the upper trunk, C 7 becomes the the upper trunk, C 7 becomes the middle trunk, and C 8 and T 1 join middle trunk, and C 8 and T 1 join to form the lower trunksto form the lower trunks

Each of the trunks divides into Each of the trunks divides into anterior and posterior divisions, anterior and posterior divisions, which then form cords which then form cords

Plexus BranchesPlexus Branches

The branches give rise to the The branches give rise to the peripheral nerves: peripheral nerves: – Musculocutaneous (lateral cord)Musculocutaneous (lateral cord)– AxillaryAxillary– Radial (posterior cord)Radial (posterior cord)– Ulnar (medial cord)Ulnar (medial cord)– Median (medial and lateral cords)Median (medial and lateral cords)

Nerves from the RootsNerves from the Roots

The dorsal scapular nerve (C 5)The dorsal scapular nerve (C 5)– Supplies the rhomboids and levator Supplies the rhomboids and levator

scapulae muscles scapulae muscles The long thoracic nerve (C 5-7)The long thoracic nerve (C 5-7)

– Supplies the serratus anterior Supplies the serratus anterior muscle muscle

Nerves from the Nerves from the TrunksTrunks SubclaviusSubclavius Suprascapular nerve. Motor Suprascapular nerve. Motor

supply to the supraspinatus and supply to the supraspinatus and infraspinatus muscles, and infraspinatus muscles, and sensory innervation to the sensory innervation to the shoulder jointshoulder joint

Nerves from the CordsNerves from the Cords

The medial and lateral pectoral nerves.The medial and lateral pectoral nerves.– Supply the pectoralis major and pectoralis Supply the pectoralis major and pectoralis

minor muscles minor muscles Subscapular nerveSubscapular nerve

– Supplies the subscapularis muscle Supplies the subscapularis muscle Thoracodorsal nerveThoracodorsal nerve

– Supplies the latissimus dorsi muscleSupplies the latissimus dorsi muscle Medial antebrachial cutaneous nerveMedial antebrachial cutaneous nerve Medial brachial cutaneous nerve Medial brachial cutaneous nerve

The Musculocutaneous The Musculocutaneous Nerve (C 5-6)Nerve (C 5-6) Motor - supplies the Motor - supplies the

coracobrachialis, biceps brachii coracobrachialis, biceps brachii and brachialis musclesand brachialis muscles

Sensory - lateral antebrachial Sensory - lateral antebrachial cutaneous nerve cutaneous nerve

Axillary Nerve (C5–6)Axillary Nerve (C5–6)

Motor - Motor - Teres minor, deltoid Teres minor, deltoid musclemuscle

Sensory - Superior lateral brachial Sensory - Superior lateral brachial cutaneous nerve cutaneous nerve

The Radial Nerve (C 6-8, T The Radial Nerve (C 6-8, T 1)1)

Motor Motor – In the arm - supplies the triceps, anconeus, In the arm - supplies the triceps, anconeus,

and the upper portion of the extensor-and the upper portion of the extensor-supinator group of forearm musclessupinator group of forearm muscles

– In the forearm, the posterior interosseous In the forearm, the posterior interosseous nerve innervates all of the muscles of the nerve innervates all of the muscles of the six extensor compartments of the wrist, six extensor compartments of the wrist, with the exception of the extensor carpi with the exception of the extensor carpi radialis brevis (ECRB) and extensor carpi radialis brevis (ECRB) and extensor carpi radialis longus (ECRL) radialis longus (ECRL)

The Radial Nerve (C 6-8, T The Radial Nerve (C 6-8, T 1)1)

SensorySensory– The posterior brachial cutaneous The posterior brachial cutaneous

nerve: the dorsal aspect of the armnerve: the dorsal aspect of the arm– The posterior antebrachial The posterior antebrachial

cutaneous nerve: the dorsal surface cutaneous nerve: the dorsal surface of the forearmof the forearm

– The superficial radial nerve: the The superficial radial nerve: the dorsal aspect of the radial half of the dorsal aspect of the radial half of the hand hand

The Median Nerve (C 5-T The Median Nerve (C 5-T 1)1)

Motor (Motor (anterior interosseous nerve)anterior interosseous nerve)– Innervation to flexor pollicis longus (FPL), Innervation to flexor pollicis longus (FPL),

and to the pronator quadratus (PQ)and to the pronator quadratus (PQ)– May supply all or none of the flexor May supply all or none of the flexor

digitorum profundus and part of the flexor digitorum profundus and part of the flexor digitorum superficialisdigitorum superficialis

Sensory - Sensory - supplies the skin of the supplies the skin of the palmar aspect of the thumb and the palmar aspect of the thumb and the lateral 2 ½ fingers, and the distal ends lateral 2 ½ fingers, and the distal ends of the same fingers of the same fingers

The Ulnar Nerve (C 8, T The Ulnar Nerve (C 8, T 1)1) Motor – Motor – supplies the flexor carpi ulnaris, supplies the flexor carpi ulnaris,

the ulnar head of the flexor digitorum the ulnar head of the flexor digitorum profundus, and all of the small muscles profundus, and all of the small muscles deep and medial to the long flexor deep and medial to the long flexor tendon of the thumb, except the first 2 tendon of the thumb, except the first 2 lumbricales lumbricales

Sensory - supplies the ulnar side of the Sensory - supplies the ulnar side of the dorsum of the hand, the dorsal aspect of dorsum of the hand, the dorsal aspect of the fifth finger and the ulnar half of the the fifth finger and the ulnar half of the forefinger forefinger

The Thoracic NervesThe Thoracic Nerves

Dorsal ramiDorsal rami Ventral ramiVentral rami

The Lumbar PlexusThe Lumbar Plexus

Formed from the ventral nerve Formed from the ventral nerve roots of the second, third, and roots of the second, third, and fourth lumbar nerves (in fourth lumbar nerves (in approximately 50% of cases, the approximately 50% of cases, the plexus also receives a plexus also receives a contribution from the last thoracic contribution from the last thoracic nerve)nerve)

BranchesBranches

L 1, L 2, and L 4 divide into upper L 1, L 2, and L 4 divide into upper and lower branches. and lower branches. – The upper branch of L 1 forms the The upper branch of L 1 forms the

iliohypogastric and ilioinguinal nervesiliohypogastric and ilioinguinal nerves– The lower branch of L 1 joins the The lower branch of L 1 joins the

upper branch of L 2 to form the upper branch of L 2 to form the genitofemoral nerve genitofemoral nerve

– The lower branch of L 4 joins L 5 to The lower branch of L 4 joins L 5 to form the lumbosacral trunkform the lumbosacral trunk

Femoral Nerve (L2-4)Femoral Nerve (L2-4)

The motor component supplies The motor component supplies the iliopsoas muscle, while in the the iliopsoas muscle, while in the thigh it supplies the sartorius, thigh it supplies the sartorius, pectineus, and quadriceps pectineus, and quadriceps femoris musclesfemoris muscles

Femoral Nerve (L2-4)Femoral Nerve (L2-4)

The sensory distribution of the The sensory distribution of the femoral nerve includes the femoral nerve includes the anterior and medial surfaces of anterior and medial surfaces of the thigh via the anterior femoral the thigh via the anterior femoral cutaneous nerve, and the medial cutaneous nerve, and the medial aspect of the knee, the proximal aspect of the knee, the proximal leg and articular branches to the leg and articular branches to the knee, via the saphenous nerve knee, via the saphenous nerve

Obturator Nerve (L2-4)Obturator Nerve (L2-4)

The anterior division - supplies The anterior division - supplies muscular branches to the muscular branches to the adductors longus, brevis and the adductors longus, brevis and the gracilis, and rarely to the gracilis, and rarely to the pectineuspectineus

The posterior division - supplies The posterior division - supplies the obturator externus, and the the obturator externus, and the adductors magnus and brevis adductors magnus and brevis

Lateral Cutaneous Lateral Cutaneous NerveNerve (LCN) of the (LCN) of the ThighThigh A A purely sensory nerve that is purely sensory nerve that is

derived primarily from the second derived primarily from the second and third lumbar nerve roots, with and third lumbar nerve roots, with occasional contributions from the occasional contributions from the first lumbar nerve rootfirst lumbar nerve root

Associated with Associated with meralgia meralgia paresthetica paresthetica

The Sacral PlexusThe Sacral Plexus

The sacral plexus is formed by the The sacral plexus is formed by the ventral rami of the L4‑5 and the S1‑4 ventral rami of the L4‑5 and the S1‑4 nervesnerves

The upper 3 nerves of the plexus The upper 3 nerves of the plexus divide into 2 sets of branches; the divide into 2 sets of branches; the medial branches, which are distributed medial branches, which are distributed to the multifidi muscles, and the to the multifidi muscles, and the lateral branches, which become the lateral branches, which become the medial cluneal nervesmedial cluneal nerves

Superior Gluteal NerveSuperior Gluteal Nerve

The roots of the superior gluteal The roots of the superior gluteal nerve (L4, L5, S1) arise within the nerve (L4, L5, S1) arise within the pelvis from the sacral plexus pelvis from the sacral plexus

Supplies the gluteus medius and Supplies the gluteus medius and gluteus minimus gluteus minimus

Inferior Gluteal NerveInferior Gluteal Nerve

Supplies the Supplies the gluteus maximus gluteus maximus

Sciatic NerveSciatic Nerve

The largest nerve in the bodyThe largest nerve in the body Arises from the L 4, L 5 and S 1-3 Arises from the L 4, L 5 and S 1-3

nerve roots as a continuation of nerve roots as a continuation of the lumbosacral plexusthe lumbosacral plexus

Composed of the independent Composed of the independent tibial (medial) and common tibial (medial) and common peroneal (lateral) divisions peroneal (lateral) divisions

Common Fibular Common Fibular (Peroneal) Nerve(Peroneal) Nerve Formed by the upper 4 posterior Formed by the upper 4 posterior

divisions (L 4, 5 and S 1, 2) of the divisions (L 4, 5 and S 1, 2) of the sacral plexussacral plexus

Three terminal rami: the Three terminal rami: the recurrent articular, the superficial recurrent articular, the superficial peroneal, and deep peroneal peroneal, and deep peroneal

The Superficial Fibular The Superficial Fibular (Peroneal) (Peroneal) Motor supply to Motor supply to the peroneus the peroneus

longus and brevis muscleslongus and brevis muscles Sensory distribution to the lower Sensory distribution to the lower

front of the leg, to the dorsum of front of the leg, to the dorsum of the foot, part of the big toe, and the foot, part of the big toe, and adjacent sides of the second to adjacent sides of the second to fifth toes up to the second fifth toes up to the second phalangesphalanges

The Deep Fibular The Deep Fibular (Peroneal) (Peroneal) Supplies the tibialis anterior, Supplies the tibialis anterior,

extensor digitorum longus, extensor digitorum longus, extensor hallucis longus, and extensor hallucis longus, and peroneus tertius muscles peroneus tertius muscles

Divides into a medial and lateral Divides into a medial and lateral branchesbranches

The Pudendal Plexus The Pudendal Plexus

Supplies the coccygeus, levator Supplies the coccygeus, levator ani, and sphincter ani externus ani, and sphincter ani externus musclesmuscles

Coccygeal Plexus Coccygeal Plexus

Small sensory anococcygeal Small sensory anococcygeal nerves derived from the last three nerves derived from the last three segments (S 4, 5, C)segments (S 4, 5, C)

The Tibial NerveThe Tibial Nerve

Formed from all 5 anterior divisions (L Formed from all 5 anterior divisions (L 4, 5 and S 1, 2, 3)4, 5 and S 1, 2, 3)

Supplies the gastrocnemius, plantaris, Supplies the gastrocnemius, plantaris, soleus, popliteus, tibialis posterior, soleus, popliteus, tibialis posterior, flexor digitorum longus pedis, and flexor digitorum longus pedis, and flexor hallucis longus muscles flexor hallucis longus muscles

The portion of the tibial trunk below The portion of the tibial trunk below the popliteal space is often called the the popliteal space is often called the posterior tibial nerveposterior tibial nerve

Sural nerveSural nerve

A sensory branch of the tibial A sensory branch of the tibial nervenerve

Formed by the lateral sural Formed by the lateral sural cutaneous nerve from the cutaneous nerve from the common peroneal nerve and the common peroneal nerve and the medial calcaneal nerve from the medial calcaneal nerve from the tibial nervetibial nerve

ProprioceptionProprioception

A specialized variation of the sensory A specialized variation of the sensory modality of touch, which plays an modality of touch, which plays an important role in coordinating muscle important role in coordinating muscle activity, involves the integration of activity, involves the integration of sensory input concerning static joint sensory input concerning static joint position (joint position sensibility), joint position (joint position sensibility), joint movement (kinesthetic sensibility), movement (kinesthetic sensibility), velocity of movement, and force of velocity of movement, and force of muscular contraction, from the skin, muscular contraction, from the skin, muscles, and jointsmuscles, and joints

MechanoreceptorsMechanoreceptors

Four different types:Four different types:– Type I. Type I. Small Ruffini endings. Slow-Small Ruffini endings. Slow-

adapting, low thresholdadapting, low threshold– Type II. Type II. Pacinian corpusclesPacinian corpuscles. Rapidly . Rapidly

adapting, low thresholdadapting, low threshold– Type III. Type III. Large RuffiniLarge Ruffini. Slowly . Slowly

adapting, high threshold adapting, high threshold – Type IV. Slowly adapting, high Type IV. Slowly adapting, high

threshold threshold

BalanceBalance

Balance is the process by which the Balance is the process by which the body’s center of mass is controlled body’s center of mass is controlled with respect to the base of support, with respect to the base of support, whether that base of support is whether that base of support is stationary or movingstationary or moving

Three components of balanceThree components of balance– VisionVision– Inner earInner ear– Vestibular systemVestibular system

Pain transmissionPain transmission

Common free nerve endings have Common free nerve endings have two distinct pathways into the two distinct pathways into the central nervous system, which central nervous system, which correspond to the two different correspond to the two different types of pain:types of pain:– Fast conducting - A-delta fibersFast conducting - A-delta fibers– Slow conducting - C-fibersSlow conducting - C-fibers

Pain ControlPain Control

Gate theoryGate theory The peri-aquaductal grey (PAG) The peri-aquaductal grey (PAG)

systemsystem

EXAMINATIONEXAMINATION

Upper Motor Neuron Upper Motor Neuron LesionLesion Characterized by spastic paralysis Characterized by spastic paralysis

or paresis, little or no muscle or paresis, little or no muscle atrophy, hyperreflexive deep atrophy, hyperreflexive deep tendon reflexes in a non-tendon reflexes in a non-segmental distribution, and the segmental distribution, and the presence of pathological signs presence of pathological signs and reflexesand reflexes

UMN Signs and UMN Signs and SymptomsSymptoms

– Periodic loss of consciousnessPeriodic loss of consciousness– DysphasiaDysphasia– DiplopiaDiplopia– HemianopiaHemianopia– AtaxiaAtaxia– HyperreflexiaHyperreflexia– Babinski responseBabinski response

UMN Signs and UMN Signs and SymptomsSymptoms

– Positive Hoffman or Oppenheim testPositive Hoffman or Oppenheim test– Flexor withdrawalFlexor withdrawal– NystagmusNystagmus– Quadrilateral paresthesiaQuadrilateral paresthesia– Bilateral upper limb paresthesiaBilateral upper limb paresthesia– Peri-oral anesthesiaPeri-oral anesthesia– Drop attacksDrop attacks– Wallenberg syndromeWallenberg syndrome

Lower Motor Neuron Lower Motor Neuron LesionLesion Characteristics of a LMN include Characteristics of a LMN include

muscle atrophy and hypotonus, a muscle atrophy and hypotonus, a diminished or absent deep tendon diminished or absent deep tendon reflex (DTR) of the areas served reflex (DTR) of the areas served by a spinal nerve root, or a by a spinal nerve root, or a peripheral nerve and an absence peripheral nerve and an absence of pathological signs or reflexesof pathological signs or reflexes

Deep Tendon ReflexDeep Tendon Reflex

A reflex is a subconscious A reflex is a subconscious programmed unit of behavior in which programmed unit of behavior in which a certain type of stimulus from a a certain type of stimulus from a receptor automatically leads to the receptor automatically leads to the response of an effectorresponse of an effector

The spinal reflexes are the simplest The spinal reflexes are the simplest (e.g., stretch reflex, withdrawal reflex) (e.g., stretch reflex, withdrawal reflex) and are entirely contained in the spinal and are entirely contained in the spinal cordcord

Pathological Reflexes Pathological Reflexes

Pathological reflexes are normally Pathological reflexes are normally integrated by individuals as they integrated by individuals as they develop, unless an injury or disease develop, unless an injury or disease process results in a loss of this process results in a loss of this normal suppression by the normal suppression by the cerebrum on the segmental level of cerebrum on the segmental level of the brainstem or spinal cord, the brainstem or spinal cord, resulting in a release of the resulting in a release of the primitive reflexprimitive reflex

Pathological reflexesPathological reflexes

BabinskiBabinski OppenheimOppenheim ClonusClonus Hoffmann’s SignHoffmann’s Sign

Supraspinal reflexesSupraspinal reflexes

The supraspinal reflexes produce The supraspinal reflexes produce movement patterns that can be movement patterns that can be modulated by descending modulated by descending pathways and the cortexpathways and the cortex

Integrate vision with balance Integrate vision with balance Include the cervico-ocular Include the cervico-ocular

reflexes (COR) and vestibulo-reflexes (COR) and vestibulo-ocular reflexes (VOR) ocular reflexes (VOR)

Sensory testingSensory testing

The dorsal roots of the spinal The dorsal roots of the spinal nerves are represented by nerves are represented by restricted peripheral sensory restricted peripheral sensory regions called dermatomesregions called dermatomes

The peripheral sensory nerves are The peripheral sensory nerves are represented by more distinct and represented by more distinct and circumscribed areas circumscribed areas

Specific sensory testsSpecific sensory tests

PainPain– Origin: Lateral spinothalamic tractOrigin: Lateral spinothalamic tract– Test: Pin-prickTest: Pin-prick

Temperature Temperature – Origin: Lateral spinothalamic tract Origin: Lateral spinothalamic tract – Test: Using two test tubes, filled with Test: Using two test tubes, filled with

hot and cold water, the clinician hot and cold water, the clinician touches the skin and asks the touches the skin and asks the patient to identify “hot” or “cold.” patient to identify “hot” or “cold.”

Specific sensory testsSpecific sensory tests

PressurePressure– Origin: Spinothalamic tractOrigin: Spinothalamic tract– Test: Test: Firm pressure is applied to the Firm pressure is applied to the

patient’s muscle bellypatient’s muscle belly VibrationVibration

– Origin: Origin: Dorsal column/medial Dorsal column/medial lemniscal tractlemniscal tract

– Test: Low-pitched tuning fork Test: Low-pitched tuning fork applied over a bony process applied over a bony process

Specific sensory testsSpecific sensory tests

Position sense (Proprioception)Position sense (Proprioception)– Origin: Origin: Dorsal column/medial lemniscal Dorsal column/medial lemniscal

tract tract – Test: Ability to perceive passive Test: Ability to perceive passive

movements of the extremities movements of the extremities Movement sense (Kinesthesia) Movement sense (Kinesthesia)

– Origin: Dorsal column/medial lemniscal Origin: Dorsal column/medial lemniscal tract tract

– Test: Indicate verbally the direction of Test: Indicate verbally the direction of movement while the extremity is in motion movement while the extremity is in motion

Specific sensory testsSpecific sensory tests

StereognosisStereognosis– Origin: Origin: Dorsal column/medial lemniscal tract Dorsal column/medial lemniscal tract – Test: Ability to Test: Ability to recognize, through touch recognize, through touch

alone, a variety of small objects such as alone, a variety of small objects such as comb, coins, pencils, safety pins that are comb, coins, pencils, safety pins that are placed in the handplaced in the hand

GraphesthesiaGraphesthesia– Origin: Dorsal column/medial lemniscal tract Origin: Dorsal column/medial lemniscal tract – Test: Ability to recognize letters, numbers Test: Ability to recognize letters, numbers

or designs traced on the skin or designs traced on the skin

Specific sensory testsSpecific sensory tests

Two point discriminationTwo point discrimination– Origin: Dorsal column/medial Origin: Dorsal column/medial

lemniscal tractlemniscal tract– Test: A measure is taken of the Test: A measure is taken of the

smallest distance between two smallest distance between two stimuli that can still be perceived by stimuli that can still be perceived by the patient as two distinct stimuli the patient as two distinct stimuli

Tonal AbnormalityTonal Abnormality

SpasticitySpasticity RigidityRigidity

Cranial Nerve Cranial Nerve ExaminationExamination CN I – The Olfactory NerveCN I – The Olfactory Nerve

– The sense of smell is tested by having The sense of smell is tested by having the patient identify familiar odors the patient identify familiar odors

CN II – The Optic NerveCN II – The Optic Nerve– The optic nerve is tested by examining The optic nerve is tested by examining

visual acuity, and confrontationvisual acuity, and confrontation Visual acuity - Snellen eye chart Visual acuity - Snellen eye chart Confrontation - Test of peripheral vision Confrontation - Test of peripheral vision

Cranial Nerve Cranial Nerve ExaminationExamination CN III - Oculomotor; CN IV - CN III - Oculomotor; CN IV -

Trochlear; CN VI - AbducensTrochlear; CN VI - Abducens (tested together)(tested together)– Observation for pupil size, and ptosis Observation for pupil size, and ptosis

of the upper eyelids of the upper eyelids – Consensual pupillary response to lightConsensual pupillary response to light– Ability of the eyes to track movement Ability of the eyes to track movement

in the six fields of gaze in the six fields of gaze

Cranial Nerve Cranial Nerve ExaminationExamination CN V - TrigeminalCN V - Trigeminal

– Motor: The patient is asked to clench Motor: The patient is asked to clench the teeth, and the clinician palpates the teeth, and the clinician palpates the temporal and masseter muscles.the temporal and masseter muscles.

– Sensory: The three sensory Sensory: The three sensory branches of the trigeminal nerve are branches of the trigeminal nerve are tested, with pin-prick, close to the tested, with pin-prick, close to the mid-line of the facemid-line of the face

– The jaw tendon reflex is assessed for The jaw tendon reflex is assessed for the presence of hyperreflexiathe presence of hyperreflexia

Cranial Nerve Cranial Nerve ExaminationExamination CN VII – FacialCN VII – Facial

– The patient is asked to smile. If there The patient is asked to smile. If there is asymmetry, the patient is asked to is asymmetry, the patient is asked to frown, or wrinkle the foreheadfrown, or wrinkle the forehead

CN VIII – VestibulocochlearCN VIII – Vestibulocochlear– Balance testingBalance testing– Caloric stimulation or the ability of Caloric stimulation or the ability of

the eyes to follow a moving objectthe eyes to follow a moving object– Hearing Hearing

Cranial Nerve Cranial Nerve ExaminationExamination CN IX - GlossopharyngealCN IX - Glossopharyngeal

– The gag reflex is used to test this The gag reflex is used to test this nerve, but is only reserved for the nerve, but is only reserved for the severely affected patientsseverely affected patients

CN X - VagusCN X - Vagus – Voice qualityVoice quality– Ability to say “aah”Ability to say “aah”

Cranial Nerve Cranial Nerve ExaminationExamination CN XI - Spinal AccessoryCN XI - Spinal Accessory

– Resisted shoulder shrugResisted shoulder shrug– Resisted head rotationResisted head rotation

CN XII - HypoglossalCN XII - Hypoglossal – The patient is asked to stick out the The patient is asked to stick out the

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