PNS

Peripheral Nervous System (PNS) : 

Peripheral Nervous System (PNS) Mr. Mullins

Objectives : 

Objectives The students will understand the: Spinal nerves Cranial nerves and their function Divisions of the PNS Somatic motor nervous system Autonomic nervous system

Rational : 

Rational In continuing to understand the nervous system students must understand the function and importance of the PNS to include certain disorders involving the PNS

Overview of the Spinal Nerves : 

Overview of the Spinal Nerves 31 pairs of spinal nerves are connected to the spinal cord They are named by “numbers” by the levels of the vertebral column at which they emerge from the spinal cavity Eight cervical nerve pairs 12 thoracic nerve pairs 5 lumbar nerve pairs 5 sacral nerve pairs One coccygeal nerve pairs

Structure of Spinal Nerves : 

Structure of Spinal Nerves Each spinal nerve attaches to spinal cord by a ventral (anterior) root and a dorsal (posterior) root Dorsal root ganglion—swelling in the dorsal root of each spinal nerve All spinal nerves are mixed nerves Ramus: is one of several large branches formed after each spinal nerve emerges from the spinal cavity

Dorsal Ramus : 

Dorsal Ramus Dorsal ramus: supplies somatic motor and sensory fibers to smaller nerves that innervate the muscles and skin of the posterior surface of the following regions: Head Neck trunk

Ventral Ramus : 

Ventral Ramus Is more complex than that of the dorsal ramus Autonomic motor fibers split from the ventral ramus and head toward a ganglion of the sympathetic chain Some autonomic fibers synapse with neurons that continue to the autonomic effectors through splanchnic nerves Sympathetic rami—splitting and rejoining of autonomic fibers Motor and sensory fibers innervate muscles and glands in the extremities and lateral and ventral portions of the: Neck trunk

Nerve plexuses : 

Nerve plexuses Plexuses is a complex network formed by the ventral rami of most spinal nerves and subdividing and then joining together to form individual nerves Each individual nerve contains all the fibers that innervate a particular region of the body In plexuses, spinal nerve fibers are rearranged according to their ultimate destination, reducing the number of nerves needed to supply each body part There are four major pairs of plexuses

Major parts of plexuses : 

Major parts of plexuses Cervical plexus Brachial plexus Lumbar plexus Sacral plexus

Cervical plexus : 

Cervical plexus Located deep within the neck Made up of ventral rami of C1 thru C4 and a branch of the ventral ramus of C5 They innervate the muscles and skin of the neck, upper shoulders, and part of the head Phrenic nerve exits the cervical plexus and innervates the diaphragm.

Brachial plexus : 

Brachial plexus Located deep within the shoulder Made up of ventral rami of C5 through T1 Nerves emerging from brachial plexus innervate the lower part of the shoulder and the entire arm

Lumbar Plexus : 

Lumbar Plexus Located in the lumbar region of the back Formed by intermingling fibers of L1 through L4 Femoral nerve exits the lumbar plexus, divides into many branches, and supplies the thigh and leg

Sacral Plexus and Coccygeal Plexus : 

Sacral Plexus and Coccygeal Plexus Located in the pelvic cavity Formed by intermingling of fibers from L4 through S4 Tibial, common peroneal, and sciatic nerves exit the sacral plexus and supply nearly all the skin of the leg, posterior thigh muscles, and leg and foot muscle

Dermatomes and Myotomes : 

Dermatomes and Myotomes Dermatomes: Are region of skin surface area supplied by afferent (sensory) fibers of a given spinal nerve Myotomes: Skeletal muscle(s) supplied by efferent (motor) fibers of a given spinal nerve

Cranial Nerves : 

Cranial Nerves

Overview : 

Overview 12 pair of cranial nerves connect to the brain, mostly to the brainstem They are identified by their name and/or number They are made up of bundles of axons: Mixed cranial nerves: Axons of sensory and motor neurons Sensory cranial nerves: Axons of sensory neurons only Motor cranial nerves: Mainly axons of motor neurons and a small number of sensory fibers

12 Cranial Nerves : 

12 Cranial Nerves (1) Olfactory smell (2) Optic Carries visual information from the eyes to the brain (3) Oculomotor Control eye movement; and the amount of light entering the eye (4) Trochlear Oblique muscles of the eye (5) Trigeminal Has three branches ophthalmic; maxillary and mandibular Sensory form the skin and mucosa of head and teeth Used in mastication via the mandibular nerve

Cranial Nerves cont. : 

Cranial Nerves cont. (6) Abducens Lateral rectus muscles of the eye (7) Facial Extend to submaxillary and sublingual salivary glands Taste buds and the anterior two thirds of the tongue (8) Vestibulocochlear Deals with sensation of equilibrium (vestibular nerve) Deals with hearing (cochlear nerve) (9) Glossopharyngeal Tongue, pharynx, and carotid sinus

More Cranial Nerves : 

More Cranial Nerves (10) Vagus Supply pharynx, larynx, trachea, heart, carotid body, lungs, bronchi, diaphragm, esophagus, stomach, small intestine, and gallbladder (11) Accessory Accessory to the vagus nerve Innervates thoracic and abdominal viscera, pharynx, larynx, trapezius, and sternocleidomastoid (12) Hypoglossal Muscles of the tongue both motor and sensory

Division Of the Peripheral Nervous System : 

Division Of the Peripheral Nervous System

Division of PNS : 

Division of PNS Two functional divisions Afferent (sensory) Efferent (Motor) Divided into Somatic motor nervous system Efferent portions of the autonomic nervous system

Somatic Motor Nervous System : 

Somatic Motor Nervous System Includes all voluntary motor pathways outside the CNS Somatic effectors deals with the skeletal muscles

Somatic reflexes : 

Somatic reflexes Reflex is an action that results from a nerve impulse passing over a reflex arc; predictable response to a stimulus Cranial reflex: center of reflex arc is in the brain Spinal reflex: center of reflex arc is in the spinal cord

Slide 25: 

Reflex consists of either muscle contractions or glandular secretion: Somatic reflex: Contraction of skeletal muscles Autonomic (visceral) reflex: Either contraction of smooth or cardiac muscle or secretions by glands

Somatic reflexes clinical importance : 

Somatic reflexes clinical importance Deviate from normal in certain diseases and reflex testing as a diagnostic aid:

Reflexes : 

Reflexes Knee jerk (patellar reflex): via the patellar tendon

Slide 28: 

Ankle jerk (achilles reflex) Babinski reflex: