The Peripheral and Autonomic Nervous System Anatomy and Physiology Lab II Medgar Evers College Fall 2017

The Peripheral Nervous System Nervous structures outside the brain and spinal cord Nerves allow the CNS to receive information and take action The peripheral nervous system is divided into 2 divisions based upon function! Motor (efferent) Sensory (afferent)

Sensory Input and Motor Output Sensory (afferent) signals picked up by sensor receptors, carried by nerve fibers of PNS to the CNS Motor (efferent) signals are carried away from the CNS, innervate muscles and glands Divided according to region they serve Somatic body region Visceral body region Results in four main subdivisions Somatic sensory Visceral sensory Somatic motor Visceral motor (autonomic nervous system)

Types of Sensory and Motor Information Figure 12.3

The Autonomic Nervous System 2 branches; sympathetic and parasympathetic

sympathetic “fight or flight response” SNS is activated by any excitement, emotion, or exercise. The axons release epinephrine, norepinephrine, and acetylcholine. Leads to increased heart rate, increased blood pressure, dilation of blood vessels serving the skeletal muscles, dilation of the airways passages in the lungs, decreased urinary function, decreased digestive functions, increased metabolic rate, increased released of fatty acids and glucose and dilation of pupils

parasympathetic “rest and recovery role” Axons secrete acetylcholine Leads to decreased heart rate, decreased blood pressure, dilation of blood vessels serving the skin and abdominal viscera, mild constriction of airways passages in the lungs, increased urinary function, increased digestive functions, storage of fats and glucose, adjustment of lens for near vision, and constriction of pupils.

Basic Structural Components of the PNS Sensory receptors – pick up stimuli from inside or outside the body Motor endings – axon terminals of motor neurons innervate effectors (muscle fibers and glands) Nerves and ganglia Nerves – bundles of peripheral axons Ganglia – clusters of peripheral neuronal cell bodies

Nerves Nerves – cable-like organs in the PNS Consists of numerous axons wrapped in connective tissue Endoneurium – layer of delicate connective tissue surrounding the axon Perineurium – connective tissue wrapping surrounding a nerve fascicle Nerve fascicles – groups of axons bound into bundles Epineurium – whole nerve is surrounded by tough fibrous sheath Axon is surrounded by Schwann cells

Cranial Nerves Attach to the brain and pass through foramina of the skull Numbered from I–XII Cranial nerves I and II attach to the forebrain All others attach to the brain stem Primarily serve head and neck structures The vagus nerve (X) extends into the abdomen

The 12 Pairs of Cranial Nerves Figure 14.5

Olfactory Nerves (I) Sensory nerves of smell olfactory nerve (I) Olfactory bulb Olfactory tract Optic nerve (II) Optic chiasma Optic tract Oculomotor nerve (III) Trochlear nerve (IV) Trigeminal nerve (V) Abducens nerve (VI) Cerebellum Medulla Table 14.3 (1 of 12)

Optic Nerve (II) Sensory nerve of vision Optic nerve (II) Filaments of olfactory nerve (I) Olfactory bulb Olfactory tract Optic nerve (II) Optic chiasma Optic tract Oculomotor nerve (III) Trochlear nerve (IV) Trigeminal nerve (V) Abducens nerve (VI) Cerebellum Medulla Table 14.3 (2 of 12)

Oculomotor Nerve (III) Innervates four of the extrinsic eye muscles Filaments of olfactory nerve (I) Olfactory bulb Olfactory tract Optic nerve (II) Optic chiasma Optic tract Oculomotor nerve (III) Trochlear nerve (IV) Trigeminal nerve (V) Abducens nerve (VI) Cerebellum Medulla Table 14.3 (3 of 12)

Trochlear Nerve (IV) Innervates the superior oblique muscle (an extrinsic eye muscle) Filaments of olfactory nerve (I) Olfactory bulb Olfactory tract Optic nerve (II) Optic chiasma Optic tract Oculomotor nerve (III) Trochlear nerve (IV) Trigeminal nerve (V) Abducens nerve (VI) Cerebellum Medulla Table 14.3 (4 of 12)

Trigeminal Nerve (V) Provides sensory innervation to the face Motor innervation to chewing muscles Filaments of olfactory nerve (I) Olfactory bulb Olfactory tract Optic nerve (II) Optic chiasma Optic tract Oculomotor nerve (III) Trochlear nerve (IV) Trigeminal nerve (V) Abducens nerve (VI) Cerebellum Medulla

Abducens Nerve (VI) Abducts the eyeball – innervates lateral rectus muscle Filaments of olfactory nerve (I) Olfactory bulb Olfactory tract Optic nerve (II) Optic chiasma Optic tract Oculomotor nerve (III) Trochlear nerve (IV) Trigeminal nerve (V) Abducens nerve (VI) Cerebellum Medulla Table 14.3 (6 of 12)

Facial Nerve (VII) Innervates muscles of facial expression Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Accessory nerve (XI) Hypoglossal nerve (XII) Table 14.3 (7 of 12)

Vestibulocochlear Nerve (VIII) Sensory nerve of hearing and balance Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Accessory nerve (XI) Hypoglossal nerve (XII) Table 14.3 (8 of 12)

Glossopharyngeal Nerve (IX) Innervates structures of the tongue and pharynx Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Accessory nerve (XI) Hypoglossal nerve (XII) Table 14.3 (9 of 12)

Vagus Nerve (X) A mixed sensory and motor nerve - “Wanders” into thorax and abdomen Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Accessory nerve (XI) Hypoglossal nerve (XII) Table 14.3 (10 of 12)

Accessory Nerve (XI) An accessory part of the vagus nerve -innervates trapezius muscle Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Accessory nerve (XI) Hypoglossal nerve (XII) Table 14.3 (11 of 12)

Hypoglossal Nerve (XII) Runs inferior to the tongue - innervates the tongue muscles Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Accessory nerve (XI) Hypoglossal nerve (XII) Table 14.3 (12 of 12)

Spinal Nerves 31 pairs – contain thousands of nerve fibers Connect to the spinal cord Named for point of issue from the spinal cord 8 pairs of cervical nerves (C1–C8) 12 pairs of thoracic nerves (T1–T12) 5 pairs of lumbar nerves (L1–L5) 5 pairs of sacral nerves (S1–S5) 1 pair of coccygeal nerves (Co1)

Spinal Nerves Connect to the spinal cord by the dorsal root and ventral root Dorsal root – contains sensory fibers Dorsal root ganglion – of afferent cell bodies Ventral root – contains motor fibers arising from anterior gray column Branch into dorsal ramus and ventral ramus both contain sensory and motor fibers and a small meningeal branch.

Innervation of the Back Dorsal rami Innervate back muscles, the skin, and joints

Innervation of the Thoracic region Ventral rami arranged in simple, segmented pattern Intercostal nerves – supply intercostal muscles, skin, and abdominal wall Each gives off lateral and anterior cutaneous branches

Introduction to Nerve Plexuses Nerve plexus – a network of nerves Ventral rami ,Form nerve plexuses Cervical Brachial Lumbar Sacral Primarily serve the limbs

The Cervical Plexus Buried deep in the neck under the sternocleidomastoid muscle Formed by ventral rami of first four cervical nerves (C 1 – 4) Most are cutaneous nerves Some innervate muscles of the anterior neck

Brachial Plexus Brachial plexus lies in the neck and axilla Formed by ventral rami of C5 – T1 give rise to cords Cords give rise to main nerves of the upper limb Figure 14.9d

Lumbar Plexus Arises from L1– L4 , small contribution from T12 Smaller branches innervate the posterior abdominal wall and psoas muscle Main branches innervate the anterior thigh

The Sacral Plexus Arises from spinal nerves L4–S4 Often considered with the lumbar plexus referred to as the lumbosacral plexus Sciatic nerve – the largest nerve of the sacral plexus is actually two nerves in one sheath Tibial nerve – innervates most of the posterior lower limb Common fibular (peroneal) nerve – innervates muscles of the anterolateral leg

Stretch reflex