PNS:Somatic and Visceral

Biol. 211 Anatomy & Physiology 1

Tony Serino, Ph.D.

Biology Department

Misericordia University

(Visceral)

Cranial Nerves

CN I: Olfactory Nerve

CN II: Optic Nerve

CN III: Occulomotor NerveSuperior Orbital Fissure Midbrain

PonsOculomotor N. (III)

Ciliaryganglion

InferiorRectus muscle

InferiorOblique muscle

Superior Rectusmuscle

Medial Rectusmuscle

Levator Palpabraemuscle

ParasympatheticMotor fibers

CN IV: Trochlear Nerve

CN V: Trigeminal Nerve

CN VI: Abducens Nerve

CN VII: Facial Nerve

CN VIII: Vestibulocochlear Nerve

CN IX: Glossopharyngeal Nerve

CN X: Vagus Nerve

CN XI: Accessory Nerve

CN XII: Hypoglossal Nerve

Spinal Nerves and Plexuses

Spinal Nerve Anatomy

Cervical Plexus

Serves neck and diaphragm

Brachial Plexus and pectoral nerves

Brachial Plexus

Innervates most of the arm and someof the body wall.

Lumbar Plexus

Innervate the anterior leg.

Sacral Plexus

Innervates the posterior leg

• A dermatome is the area of skin innervated by the cutaneous branches of a single sensory spinal nerve

• All spinal nerves except C1 participate in dermatomes

Dermatomes

Reflex Arc

Stretch Reflex

Stretch Reflex•Stretching the muscle activates the muscle spindle•Excited motor neurons of the spindle cause the stretched muscle to contract•Afferent impulses from the spindle result in inhibition of the antagonist•Example: patellar reflex

–Tapping the patellar tendon stretches the quadriceps and starts the reflex action–The quadriceps contract and the antagonistic hamstrings relax

• The opposite of the stretch reflex

• Contracting the muscle activates the Golgi tendon organs

• Afferent Golgi tendon neurons are stimulated, neurons inhibit the contracting muscle, and the antagonistic muscle is activated

• As a result, the contracting muscle relaxes and the antagonist contracts

Golgi Tendon Reflex

Flexor and Crossed Extensor Reflexes

•The flexor reflex is initiated by a painful stimulus (actual or perceived) that causes automatic withdrawal of the threatened body part

•The crossed extensor reflex has two parts–The stimulated side is withdrawn–The contralateral side is extended

Neurotransmission Scenario

ANS Divsions

Parasympathetic (Craniosacral)

Sympathetic (Thoracolumbar)

Sympathetic Ganglia

Levels of Control in ANS