HEAD AND NECK PART 2

INTEGRATED CURRICULUM = Integrate Basic Science and Clinical Training

1- ENT PATIENT EXAM IN ICS COURSE - Today and next week

- Review/Preview Anatomy underlying ENT exam

2- NEUROANATOMY/NEUROLOGY - tomorrow Dr. Jeanette Norden -review Spinal Cord, everything else.

- Integrate with Gross Anatomy of Cranial Nerves, Hematomas, etc.

3. ANATOMY OF NECK- Dissection of Neck - Thursday 1/5/17 - see Thyroid Gland,

Muscles of Neck, Carotid Arteries, Jugular Veins, Lymph Nodes

1. REVIEW GROSS ANATOMY OF SPINAL CORD

2. GROSS ANATOMY OF BLOOD SUPPLY TO SPINAL CORD

3. SPINAL REFLEXES

4. REFLEX CHANGES IN LOWER AND UPPER MOTOR NEURON DISORDERS

1) GROSS ANATOMY OF SPINAL CORD

DURA MATER - tubearound spinal cord;separate from vertebral canal

ARACHNOID -closelyadherent to innerside of Dura

PIA MATER - closelyadherent to SpinalCord

grey matter -cells, etc.

white matter -axons (tracts)

Dorsal root -sensory

Ventral root -motor

2) ARTERIES OF SPINAL CORD

Anterior spinal artery -single artery onventral (anterior surface)

Posterior spinal arteries - paired on dorsal surface

LEFT AND RIGHT VERTEBRALARTERIES

BASILARARTERY

ARTERIES OF SPINAL CORD ARISEFROM VERTEBRAL ARTERY (OR ITS BRANCHES)

ARTERIES OF SPINAL CORD ARISEFROM VERTEBRAL ARTERY (OR ITS BRANCHES)

Vertebral artery courses on ventral surface of brainstem (medulla)

Vertebral arterygives rise to Anterior and Posterior Spinal arteries

VERTEBRALARTERY

BASILARARTERY

VERTEBRAL ARTERY

VERTEBRALARTERY

ANTERIOR SPINAL ARTERY

ARTERIES OF SPINAL CORD

Anterior spinal artery - branch of Vertebral A.

Posterior spinal arteries - branches of Vertebral or PosteriorInferior Cerebellar artery (branch of Vertebral)

Radicular arteries

Radicular arteries (Lateral Spinal Arteries) - enter vertebral canal via intervertebral foramina; reinforce supply to Anterior and Posterior Spinal Arteries

SENSORY STIMULUS

MOTORRESPONSE

DEFINITION OF A REFLEX - SENSORY STIMULUS PRODUCES STEREOTYPED MOTOR RESPONSE

FOR REFLEX TO OCCUR ALL ELEMENTS MUSTBE FUNCTIONAL; PATHWAYS MUST BE INTACT

3) AND 4) SPINAL REFLEXES AND DIAGNOSIS OF UPPER AND LOWER MOTOR NEURON LESIONS

3) Flexion reflex -produced by activating cutaneous, pain afferents

THREE CLASSIC SPINAL REFLEXES

1) Stretch reflex -produced by activating muscle spindles

2) Autogenic inhibition -produced by activating Golgi tendon organs

3) Flexion reflex -produced by activating cutaneous, pain afferents - avoid obstacle or painful stimulus (stepping on nail)

FUNCTIONS OF SPINAL REFLEXES

1) Stretch reflex -produced by activating muscle spindles - contributes to maintaining postural stability, countering sudden loads

2) Autogenic inhibition - produced by activating Golgi tendon organs - aids in regulating muscle tension, prevents damage to tendon, bone

STRETCH (DEEP TENDON) REFLEX

Muscle spindle -Sensoryneurons (Ia, II) SIGNALMUSCLELENGTH

Excites Lower (Alpha) motor neuron in Ventral Horn

Two methods:1) Rapidly Stretch

muscle (changemuscle length)

2) TAP ONMUSCLE TENDON

Stretched muscle contracts rapidly

Activate- Muscle spindle(Group Ia and II); monosynapticallyexcite Alpha (Lower) motor neuronto same muscle.

Note: Response large because also excite motor neurons to muscles with similar action and inhibit muscles with opposite action

SENSORY STIMULUS

MOTORRESPONSE

MUSCLE TONUS = resting tension in muscle

Activity in muscle spindles at rest is important in determining Tonus because connection is monosynaptic

REFLEXES CHANGED BY GAMMA MOTOR NEURONS - GET PATIENT TO RELAX BEFORE TESTING TONUS OR STRETCH REFLEX

Gamma motor neurons innervate muscle cells in muscle spindles; Gamma motor neurons can heighten stretch reflexes (Gamma dynamic motor neurons specifically effect Ia sensory neurons)

ALPHAMOTORNEURONS -innervateregular skeletalmuscle cells

GAMMAMOTORNEURONS -innervatemuscle cellsin musclespindles

Tonus reflects firing of alphamotor neurons at rest

TONUS - Tested by physician slowly extending or flexing joints (stretching patient's muscle)

Upper motor neurons can modulate (change) reflexes by:1) Changing excitability of alpha motor neurons2) Pre-synaptic Inhibition of Ia terminals; reduces the amount of transmitter release at the synapse upon motor neuron

REFLEXES CAN ALSO BE CHANGED BY ACTIVITY IN UPPER MOTOR NEURONS

UPPER MOTOR NEURONS -all descending inputs that affect Lower Motor Neurons (ex. Corticospinal orReticulospinal neurons)

LOWER MOTOR NEURONS =Alpha motor neurons that innervatemuscle

MUSCLE

MUSCLE SPINDLE

LOWER MOTOR NEURON DISORDERS

1) Decreased stretch (tendon) reflexes - no activation of muscle2) Decreased tonus - no tonic alpha motor neuron activity3) Muscle atrophy - Fasciculations (twitches) precede atrophy -Alpha motor neurons fire spontaneously4) No Babinski sign - no effect descending control

LOWER MOTORNEURON

Flaccid Paralysis - muscle is effectively denervated (can affect single muscles)

UPPER MOTOR NEURONS -descending systems

Examples:1) Compression of spinal nerve2) Poliomyelitis - viral infections affecting motor neurons

UPPER MOTOR NEURON DISORDERS

1) Increased stretch (tendon) reflexes - No modulation, remove inhibition of reflex pathways2) Increased tone - Remove inhibition of reflex pathways3) No Fasciculations4) Babinski sign - effect descending control of Flexor reflex5) Clasped Knife Reflex - high forces activate Golgi tendon organs

LOWER MOTORNEURON

Spastic Paralysis - affect groups of muscles

UPPER MOTOR NEURONS -descending systems

Example: Damage to Corticospinal (Corticobulbar) tracts - can occur at all levels from cortex to spinal cord (brainstem)

HYPERREFLEXIA: INCREASED STRETCH REFLEX ON ONE SIDE [used by permission of Paul D. Larsen, M.D., University of Nebraska Medical Center;

http://library.med.utah.edu/neurologicexam]

Hand of clinician

AUTOGENIC INHIBITION: GOLGI TENDON ORGANS DECREASE FORCEGOLGI TENDON ORGANS SIGNAL MUSCLE FORCE - when force is high, activate Golgi TendonOrgan reflexes (Autogenicinhibition); inhibits alpha motor neurons, DECREASE FORCE

GOLGITENDON ORGAN (GTO)

AUTOGENIC INHIBITION

Physician applies, gradual forceful stretch of muscle: resistance to stretch builds until it suddenly gives way.

GTO(Ib)

muscletendon

GTO(Ib)

Alpha motor neuron (inhibited)

CLASP-KNIFE PHENOMENON

stretch muscle

SENSORY STIMULUS: FORCE ON MUSCLE TENDON

MOTORRESPONSE: FORCE DECREASES

CLASPED KNIFE REFLEX: is an example of Autogenic inhibition.It is elicited in patients with UMN lesions due to high tonus in muscle.

ENCOUNTERSHIGH RESISTANCE DUE TO HIGH TONUS IN TRICEPS ANDHIGH STRETCH REFLEXES

PHYSICIANHOLDS WRIST ANDPUSHES HEREAFTER TELLING PATIENT TORELAX

HIGH IMPOSEDFORCEEXCITESGOLGITENDON ORGANS IN TRICEPS TENDONWHICH INHIBITS MOTOR NEURONS TO TRICEPS MUSCLE

ELBOW JOINT SNAPS SHUTLIKE A POCKETKNIFE =CLASPED KNIFEREFLEX

2) KEEP TRYING AND TENSION ONTRICEPS TENDON EXCITES GOLGITENDON ORGANS

3) TRICEPS RELAXES AND RESISTANCE SUDDENLY DECREASES: ELBOW JOINT FLEXES

1) PHYSICIAN TRIES TO FLEXELBOW JOINT OF PATIENT WITHUPPER MOTOR NEURON LESION

FLEXOR REFLEX

- Cutaneous afferentsynapse onto Interneurons

- Interneurons make excitatory synapse onto Flexor motor neurons

- Note: Also excite extensormotor neurons in opposite leg (not fall down)

Cutaneous afferent

Interneurons

Flexor motor neuron

Step onnail

Liftleg

KNEE JOINT

SENSORY STIMULUS -painful, irritatingstimulus to skin

MOTORRESPONSE

ExtendOppositeleg

FLEXOR REFLEXES ALSO CHANGE IN UPPER MOTOR NEURON LESIONS: BABINSKI SIGN

Babinski sign - seen after Upper Motor neuron lesion-direction of movement changes from flexing toes to extending and fanning (abducting) toes

FLEXTOES(DOWN)

EXTEND BIGTOE, FANNING(ABDUCTION)OF OTHERTOES

NORMAL RESPONSE BABINSKI SIGN –(EXTENSOR PLANTAR RESPONSE)

STIMULUS –TO SKINOF SOLEOF FOOT

PLANTAR REFLEX: ABNORMAL, (POSITIVE) BABINSKISIGN ON ONE SIDE [used by permission of Paul D. Larsen, M.D., University of Nebraska Medical Center; http://library.med.utah.edu/neurologicexam]