The Spinal Cord and Spinal Nerves Chapter 12

THE SPINAL CORD

Spinal Cord Anatomy

THE SPINAL NERVES

Spinal Nerve Anatomy

Spinal Nerve Distribution

Spinal Nerves of the Body

The Cervical Plexus

Cervical Plexus  Most branches are cutaneous nerves that supply sensory impulses from the skin of the neck, ear, back of the head and shoulders  Other branches innervate the muscles of the anterior neck  Phrenic nerve = sole motor nerve supply to the diaphragm for breathing

The Brachial Plexus

o Median nerve: Flexor muscles of the anterior forearm and intrinsic muscles in palm; pronates the forearm, flex the wrist and fingers, and oppose the thumb o Radial nerve: largest branch; posterior muscles of the arm and forearm; innervates all the extensor muscles for elbow, wrist, and finger extension, forearm supination, and thumb abduction

The Brachial Plexus o Ulnar nerve: produces wrist and finger flexion and adduction as well as abduction of the medial fingers o Suprascapular nerve: innervates the supraspinatus and infraspinatus muscles for movement of the shoulder

Intercostal Nerves

The Lumbar Plexus

o Femoral nerve: the largest terminal nerve of this plexus and innervates the anterior muscles of the thigh (thigh flexors and knee extensors). Branches to form the saphenous nerve on the medial thigh and knee extending to the foot. o Obturator nerve: innervates the adductor muscles of the leg.

The Sacral Plexus

o Sciatic nerve: which supplies the entire lower limb (leg) except the anteromedial thigh.  Tibial nerve – flexors of the knee and extensors of the ankle, flexors of the toes, and plantar surface of the foot.  Fibular nerve. – biceps femoris muscle and tibialis anterior muscle; extensors of the toes, surface of the leg and dorsal surface of the foot.

The Sacral Plexus o Pudendal nerve - innervates muscles of the perineum, urogenital diaphragm and external anal and urethral sphincter muscles; skin of the genitalia.

REFLEXES

NEURAL CIRCUITS Divergence Parallel Serial Convergence Reverberation

Neural Circuits

Steps of the Reflex Arc

Classification of Reflexes

Monosynaptic Reflexes

Polysynaptic Reflexes

Types of Reflexes  Stretch  Flexor reflex  Crossed extensor reflex

Stretch Reflex

Flexor Reflex

Crossed Extensor Reflex

Reflexes Used in Diagnostic Testing