PERIPHERAL AUTONOMIC NERVOUS SYSTEMS Leonardo Da Vinci The

PERIPHERAL & AUTONOMIC NERVOUS SYSTEMS Leonardo Da Vinci, The Battle of Anghiari Human Anatomy Sonya Schuh-Huerta, Ph. D.

The Peripheral Nervous System • The PNS – Is the nervous system outside the brain & spinal cord – Provides vital links to the body & outside world – Nerves allow the CNS to receive info & initiate action • Sensory inputs & motor outputs – Categorized as • Somatic or visceral • General or special

Functional Organization of the PNS Central nervous system (CNS) Peripheral nervous system (PNS) Sensory (afferent) division Somatic sensory General: Touch, pain, pressure, vibration, temperature, and proprioception in skin, body wall, and limbs Visceral sensory General: Stretch, pain, temperature, chemical changes, and irritation in viscera; nausea and hunger Special: Hearing, equilibrium, vision Special: Taste, smell Motor (efferent) division Somatic nervous system Motor innervation of all skeletal muscles Sympathetic division Autonomic nervous system (ANS) Motor innervation of smooth muscle, cardiac muscle, and glands Parasympathetic division

Basic Structural Components of PNS • Sensory receptors pick up stimuli from inside or outside body (we’ll cover later) • Nerves & ganglia – Nerves bundles of peripheral axons – Ganglia clusters of peripheral neuronal cell bodies • Motor endings axon terminals of motor neurons – Innervate effectors (muscle fibers & glands)

The Cranial Nerves – Yes you have to know them… • Attach to brain & pass through foramina of the skull • Numbered I–XII (1 -12) • Cranial nerves I & II attach to the forebrain – All others attach to brain stem • Primarily serve head & neck structures – The vagus nerve (X) is the only cranial nerve that extends into abdomen

The Cranial Nerves Filaments of olfactory nerve (I) Frontal lobe Olfactory bulb Olfactory tract Optic nerve (II) Optic chiasma Optic tract Oculomotor (III) Trochlear (IV) Temporal lobe Infundibulum Facial (VII) Trigeminal (V) Vestibulocochlear (VIII) Abducens (VI) Glossopharyngeal (IX) Cerebellum Medulla oblongata Vagus (X) Accessory (XI) Hypoglossal (XII)

The Cranial Nerves Cranial nerves Sensory function Somatic sensory (SS) Somatic motor (SM) Visceral motor: parasympathetic (VM) III Oculomotor SM VM IV Trochlear SM I Olfactory II Optic V Trigeminal VI Abducens Visceral sensory (VS) Motor function Smell Vision General SM SM Odessa Ofelia O’Conner Takes Tests Amazingly!

The Cranial Nerves Cranial nerves VII Facial VIII Vestibulocochlear IX Glossopharyngeal X Vagus Sensory function Motor function Somatic sensory (SS) Visceral sensory (VS) Somatic motor (SM) Visceral motor: parasympathetic (VM) General; taste SM VM Hearing; equilibrium General Some General; taste SM VM XI Accessory SM XII Hypoglossal SM Fiesty Victor Gets Very Agitated Here…

I ) Olfactory Nerves • Sensory nerves of smell

II) The Optic Nerves • Sensory nerve of vision

III) The Oculomotor Nerves • Innervates 4 extrinsic eye muscles Table 14. 2 (3 of 12)

IV) The Trochlear Nerves • Innervates the superior oblique muscle (an extrinsic eye muscle)

The Trigeminal Nerves • Largest of the cranial nerves – Has 3 divisions • Ophthalmic • Maxillary • Mandibular • Cell bodies of sensory neurons located in the trigeminal ganglion • Mandibular division contains motor fibers that innervate the chewing muscles

V) The Trigeminal Nerves

VI) The Abducens Nerves • Abducts the eyeball innervates lateral rectus muscle

VII) The Facial Nerves • Innervates muscles of facial expression

VIII) The Vestibulocochlear Nerves • Sensory nerve of hearing & balance

IX) The Glossopharyngeal Nerves • Innervates structures of the tongue & pharynx

X) The Vagus Nerves • A mixed sensory & motor nerve – “Wanders” into thorax & abdomen – Parasympathetic innervation of organs

XI) The Accessory Nerves • • • Unique among cranial nerves Accessory nerves come from ventral rootlets of spinal cord Do not arise from the brainstem

XII) The Hypoglossal Nerves • Runs inferior to the tongue – Innervates the tongue muscles

The Spinal Nerves • 31 pairs contain thousands of nerve fibers Formula C 8, T 12, L 5, S 5, Cx 1 = 31 • Connect to spinal cord • Named for region of vertebral column – – – 8 pairs cervical nerves (C 1–C 8) 12 pairs thoracic nerves (T 1–T 12) 5 pairs lumbar nerves (L 1–L 5) 5 pairs sacral nerves (S 1–S 5) 1 pair coccygeal nerves (Cx 1)

Spinal Nerves – Posterior View Cervical plexus Brachial plexus Cervical nerves C 1 – C 8 Cervical enlargement Intercostal nerves Thoracic nerves T 1 – T 12 Lumbar enlargement Lumbar plexus Sacral plexus Cauda equina Lumbar nerves L 1 – L 5 Sacral nerves S 1 – S 5 Coccygeal nerve Co 1

Spinal Nerves • Branch into dorsal ramus & ventral ramus – Dorsal & ventral rami contain sensory and motor fibers • Rami communicantes connect to the base of the ventral ramus – Lead to the sympathetic chain ganglia

Spinal Nerves Sensory axon and cell body Dorsal root ganglion Dorsal ramus Nerves Spinal nerve Ventral ramus Axon of motor neuron Ventral root Neuromuscular junction Sensory receptors in skin (e. g. , free nerve endings of sensory neuron)

Spinal Nerves White matter Gray matter Ventral root Dorsal & ventral rootlets of spinal nerve Dorsal root ganglion Dorsal ramus of spinal nerve Ventral ramus of spinal nerve Spinal nerve Rami communicantes Sympathetic trunk ganglion

Innervation of the Back • Dorsal rami – Innervate back muscles – Follow a neat, segmented pattern • Innervate a horizontal strip of muscle & skin – In line with emergence point from the vertebral column

Innervation of the Anterior Thoracic & Abdominal Wall • Thoracic region – Ventral rami arranged in simple, segmented pattern – Intercostal nerves supply intercostal muscles, skin, & abdominal wall

Introduction to Nerve Plexuses & Peripheral Nerves • Nerve plexus a network of nerves! • Branch from ventral rami (except T 2–T 12) – Branch & join with one another – Form nerve plexuses • In cervical, brachial, lumbar, & sacral regions – Primarily serve the limbs – Fibers from ventral rami criss-cross

The Cervical Plexus • Buried deep in the neck – Under the sternocleidomastoid m. • Most are cutaneous nerves • Some innervate muscles of the anterior neck • Phrenic nerve the most important nerve of the cervical plexus -Innervates diaphragm, mediastinal pleura & pericardium Control of breathing!

The Cervical Plexus Ventral rami Segmental branches Hypoglossal nerve (XII) Lesser occipital nerve Greater auricular nerve Transverse cervical nerve Ansa cervicalis Ventral rami: C 1 C 2 C 3 C 4 Accessory nerve (XI) Phrenic nerve Supraclavicular nerves C 5

The Brachial Plexus & Innervation of the Upper Limb • Brachial plexus lies in the neck & axilla • Formed by ventral rami of C 5–C 8 • Cords give rise to main nerves of upper limb Major terminal branches (peripheral nerves) Cords Anterior Musculocutaneous Lateral Median Medial Ulnar Posterior Anterior Trunks Upper Posterior Anterior Posterior Roots (ventral rami) C 5 C 6 Middle Posterior Radial Axillary Divisions C 7 C 8 Lower T 1 (c) Flowchart summarizing relationships within the brachial plexus

Innervation of the Upper Limb • Musculocutaneous – Innervates the biceps brachii & brachialis m. • Median – Innervates anterior forearm muscles & palm • Ulnar – Innervates intrinsic hand muscles & skin of hand

Innervation of the Upper Limb • Radial – Largest branch of the brachial plexus – Innervates muscles of the posterior upper limb • Axillary – Innervates the deltoid & teres minor m.

Major Nerves of the Upper Limb Axillary nerve Humerus Radial nerve Musculocutaneous nerve Ulna Radius Ulnar nerve Median nerve Radial nerve (superficial branch) Dorsal branch of ulnar nerve Superficial branch of ulnar nerve Digital branch of ulnar nerve Anterior divisions Posterior divisions Muscular branch Digital branch Median nerve

Major Nerves of the Upper Limb Axillary nerve Branches of axillary nerve Radial nerve Ulnar nerve (cut) Median nerve (cut) Posterior cutaneous nerve Deep radial nerve Superficial branch of radial nerve Anterior divisions Posterior divisions

The Lumbar Plexus & Innervation of the Lower Limb • Lumbar plexus – Arises from L 1– L 4 – Main branches innervate the anterior thigh • Femoral nerve innervates anterior thigh muscles • Obturator nerve innervates adductor muscles

The Lumbar Plexus & Nerves Iliohypogastric Ilioinguinal Femoral Lateral femoral cutaneous Obturator Anterior femoral cutaneous Saphenous (c) Distribution of the major nerves from the lumbar plexus to the lower limb

The Sacral Plexus • Arises from spinal nerves L 4–S 4 • Caudal to the lumbar plexus • Often considered with the lumbar plexus – Lumbosacral plexus

The Sacral Plexus & Innervation of the Lower Limb • Sciatic nerve the largest nerve of the sacral plexus – Actually 2 nerves in one sheath • Tibial nerve innervates most of the posterior lower limb • Common fibular (peroneal) nerve innervates muscles of the anterolateral leg

The Sacral Plexus & Nerves Superior gluteal Inferior gluteal Pudendal Sciatic Posterior femoral cutaneous Common fibular Tibial Sural (cut) Deep fibular Superficial fibular Plantar branches (c) Distribution of the major nerves from the sacral plexus to the lower limb

A Case Study… • Black lab hit in car accident – Initial inability to walk or move limbs – Hospitalized for 1 week – Regained motor control of lower limbs & front right limb – However, front left limb completely paralyzed - no sensation or motor control • What spinal nerves, plexus(es) or peripheral nerves were likely damaged?

• Damage to: – Left spinal nerves C 5 -C 8 – Left Brachial plexus – Peripheral nerves: axillary, musculocutaneous, radial, median, & ulnar

Innervation of the Skin: Dermatomes • Dermatome an area of skin innervated by cutaneous branches of a single spinal nerve! – Important diagnostic implications • Upper limb – Skin is supplied by nerves of the brachial plexus • Lower limb – Lumbar nerves anterior surface – Sacral nerves posterior surface

Map of Dermatomes C 2 C 3 C 4 C 5 C 6 C 7 C 8 T 1 T 2 T 3 T 4 T 5 T 6 T 7 T 8 T 9 T 10 C 2 C 3 C 4 C 5 T 1 T 2 T 3 T 4 T 5 T 6 T 7 T 8 T 9 T 10 T 11 T 2 C 6 C 5 C 6 C 7 L 1 C 8 L 2 T 12 S 3 T 2 C 6 C 5 L 1 C 8 L 2 C 6 C 7 C 8 L 2 S 1 L 4 S 2 S 3 S 4 S 5 C 6 C 7 S 1 S 2 L 3 C 7 C 8 S 1 L 3 L 5 L 4 S 2 C 6 T 11 T 12 L 1 L 3 L 5 L 2 L 5 L 4 L 3 L 5 L 4 S 1 L 4 L 5 (a) Anterior view L 4 L 5 S 1 (b) Posterior view

Disorders of the PNS • Shingles (Herpes zoster) – Viral infection – Inside of neuron cell bodies of peripheral nerves – breaks out & affects skin of that region - dermatome – Stems from childhood chicken pox – Often brought on by stress – Mostly experienced by those over age 50 Varicella zoster virus (chicken pox) can become dormant in the nerve cell bodies and less frequently in non-neuronal satellite cells of dorsal root, cranial nerve or autonomic ganglion, without causing any symptoms. Years or decades after a chickenpox infection, the virus may break out of nerve cell bodies and travel down nerve axons to cause viral infection of the skin in the region of the nerve. The virus may spread from one or more ganglia along nerves of an affected segment and infect the corresponding dermatome causing a painful itching rash. Although the rash usually heals within 2 -4 weeks, some sufferers experience residual nerve pain for months or years, a condition called postherpetic neuralgia. Exactly how the virus remains latent in the body, and subsequently re-activates is not understood.

Disorders of the PNS • Migraine headache – Relates to sensory innervation of cerebral arteries • Arteries dilate & compress & irritate sensory nerve endings • Myasthenia gravis – Progressive weakening of skeletal muscles – Autoimmune disorder – Antibodies destroy acetylcholine receptors

Disorders of the PNS • Carpal Tunnel syndrome – Swelling/inflammation & compression of the median nerve of the wrist due to repetitive, non-ergonomic movements – Pain, discomfort, tingling, loss of feeling

The PNS Throughout Life • Spinal nerves form late in week 4 • Each of the 31 pairs of spinal nerves: – Sends motor fibers to an individual myotome – Sends sensory fibers to overlying band of skin • During week 5, nerves reach the organs they innervate

The Autonomic Nervous System (Ch 15)

The Autonomic Nervous System • Autonomic nervous system (ANS) – General visceral motor part of the PNS – ANS has 2 divisions: • Parasympathetic • Sympathetic • Innervates: • Smooth muscle • Cardiac muscle • Glands

The ANS • The ANS a system of motor neurons – Regulates visceral functions including: • • Heart rate Blood pressure Digestion Urination

Comparison of Autonomic & Somatic Motor Systems • Autonomic nervous system – Chain of 2 motor neurons • Preganglionic neuron • Post-ganglionic neuron – Conduction is slower than somatic nervous system: • Thinly myelinated or unmyelinated axons • Motor neuron synapses in a ganglion

Divisions of the ANS • Sympathetic & Parasympathetic – Chains of 2 motor neurons • Innervate mostly the same structures • Cause opposite effects!

–Sympathetic division mobilizes the body during extreme situations Fight or Flight! –Parasympathetic division controls routine maintenance functions Rest & Digest

Divisions of the ANS • Sympathetic “fight, flight, or fright” – Activated during EXTREME situations • Exercise • Excitement • Emergencies

Divisions of the ANS • Sympathetic responses help us respond to dangerous situations – Increase heart rate & breathing rate – Increase blood & oxygen to skeletal muscles – Dilates pupils & airways – Sweating – Motility of the digestive tract & urinary tracts is inhibited – don’t need to digest or urinate now!

Divisions of the ANS • Parasympathetic division – Active when the body is at rest – Concerned with conserving energy – Directs “housekeeping” activities • • Heart rate & breathing are at low-normal levels Gastrointestinal tract digests food Urination/defecation, etc. Pupils are constricted

Anatomical Differences in Sympathetic & Parasympathetic Divisions Parasympathetic • Issue from different regions of the CNS: Eye Brain stem Salivary glands Heart – Sympathetic also called thoracolumbar division – Parasympathetic also called the craniosacral division Sympathetic Eye Skin* Cranial Cervical Sympathetic ganglia Salivary glands Lungs T 1 Heart Stomach Thoracic Stomach Pancreas L 1 Liver and gallbladder Lumbar Adrenal gland Liver and gallbladder Bladder Genitals Sacral

Anatomical Differences in Sympathetic & Parasympathetic Divisions • Length of postganglionic fibers: – Sympathetic long postganglionic fibers – Parasympathetic short postganglionic fibers; long preganglionic fibers • Branching of axons: – Sympathetic axons highly branched • Influences many organs – Parasympathetic axons less branching • Localized effect (more precise output) • Location of ganglia differ between both

Anatomical Differences in Sympathetic & Parasympathetic Divisions • Neurotransmitter released by postganglionic axons: – Sympathetic • Release Norepinephrine (NE) (adrenergic) – Parasympathetic • Release Acetylcholine (ACh) (cholinergic)

Differences Between Sympathetic & Parasympathetic Divisions SOMATIC NERVOUS SYSTEM Cell bodies in central nervous system Peripheral nervous system Neurotransmitter Effector at effector organs Effect Single neuron from CNS to effector organs ACh Stimulatory Heavily myelinated axon Skeletal muscle SYMPATHETIC NE ACh Unmyelinated postganglionic axon Lightly myelinated Ganglion preganglionic axons Epinephrine and ACh norepinephrine Adrenal medulla PARASYMPATHETIC AUTONOMIC NERVOUS SYSTEM Two-neuron chain from CNS to effector organs Blood vessel ACh Lightly myelinated preganglionic axon Unmyelinated Ganglion postganglionic axon ACh Smooth muscle (e. g. , in gut), glands, cardiac muscle Stimulatory or inhibitory, depending on neurotransmitter and receptors on effector organs

The Parasympathetic Division • Cranial outflow – Comes from the brain – Innervates • Organs of the head, neck, thorax, & abdomen • Sacral outflow – Comes from the sacral region – Innervates • Remaining abdominal & pelvic organs

Parasympathetic Division – Cranial Outflow CN III CN VII CN IX CN X Ciliary ganglion Eye Lacrimal gland Nasal mucosa Pterygopalatine ganglion Submandibular ganglion Otic ganglion Submandibular and sublingual glands Parotid gland Heart Cardiac and pulmonary plexuses Lung Preganglionic Postganglionic CN Cranial nerve

Parasympathetic Division – Sacral Outflow Celiac plexus Liver and gallbladder Stomach Pancreas S 2 Large intestine S 4 Small intestine Pelvic splanchnic nerves Inferior hypogastric plexus Urinary bladder and ureters Preganglionic Postganglionic CN Cranial nerve Rectum Genitalia (penis, clitoris, and vagina)

The Sympathetic Division • Basic organization – Issues from T 1–L 2 – Preganglionic fibers form the lateral gray horn of the spinal cord – Supplies visceral organs & structures of superficial body regions – Contains more ganglia than parasympathetic

Sympathetic Pathways to the Body Periphery • Innervate – Sweat glands – Arrector pili muscles – Peripheral blood vessels

Sympathetic Pathways Eye Lacrimal gland Nasal mucosa Pons Sympathetic trunk (chain) ganglia Blood vessels; skin (arrector pili muscles and sweat glands) Superior cervical ganglion Middle cervical ganglion T 1 Inferior cervical ganglion Salivary glands Heart Cardiac and pulmonary plexuses Lung Greater splanchnic nerve Lesser splanchnic nerve Celiac ganglion L 2 Liver and gallbladder Stomach White rami communicantes Superior mesenteric ganglion Spleen Adrenal medulla Kidney Sacral splanchnic nerves Lumbar splanchnic nerves Inferior mesenteric ganglion Small intestine Large intestine Rectum Preganglionic Postganglionic Genitalia (uterus, vagina, and penis) and urinary bladder

Sympathetic Trunk Ganglia • Located on both sides of the vertebral column • Linked by short nerves into sympathetic trunks • Sympathetic trunk ganglia also called – “Chain ganglia”

Sympathetic Trunk Ganglia • Joined to ventral rami by white & gray rami communicantes • Fusion of ganglia fewer ganglia than spinal nerves • Fusion of ganglia most apparent in cervical region – Superior, middle, & inferior cervical ganglia

Sympathetic Trunk Ganglia Spinal cord Lateral horn (visceral motor zone) Dorsal root Ventral root Dorsal root ganglion Rib Dorsal ramus of spinal nerve Ventral ramus of spinal nerve Gray ramus communicans White ramus communicans Sympathetic trunk ganglion Sympathetic trunk Ventral ramus of spinal nerve Ventral root Sympathetic trunk ganglion Sympathetic trunk Skin (arrector pili muscles and sweat glands) Gray ramus communicans White ramus communicans Thoracic splanchnic nerves 1 Synapse at the same level To effector Blood vessels (a) Location of the sympathetic trunk Splanchnic nerve Collateral ganglion (such as the celiac) Skin (arrector pili muscles and sweat glands) Blood vessels Target organ in abdomen (e. g. , intestine) To effector 2 Synapse at a higher or lower level 3 Synapse in a distant collateral ganglion anterior to the vertebral column (b) Three pathways of sympathetic innervation

Autonomic Nerves, Plexuses & Ganglia Superior cervical ganglion Middle cervical ganglion Stellate ganglion Sympathetic cardiac nerves Aortic arch Sympathetic trunk ganglia Esophagus Thoracic splanchnic nerves Adrenal (suprarenal) gland Kidney Lumbar and sacral splanchnic nerves Left vagus nerve Cardiac branches of the vagus Trachea Thoracic spinal nerves (ventral rami) Cardiac plexus Pulmonary plexus on the bronchus Aorta Vagus nerve Esophageal plexus Diaphragm Stomach with vagus nerve Celiac ganglion and plexus Superior mesenteric ganglion and plexus Aortic plexus Inferior mesenteric ganglion and plexus Superior hypogastric plexus Inferior hypogastric (pelvic) plexus Pelvic sympathetic trunk

Role of Adrenal Medulla in the Sympathetic NS • Major organ of the sympathetic nervous system • Is the largest sympathetic ganglia • Secretes great quantities of norepinephrine & epinephrine • Stimulated to secrete by preganglionic sympathetic fibers

The Adrenal Medulla Sympathetic trunk Spinal cord: Ventral T 8–L 1 root Thoracic splanchnic nerves Kidney Adrenal medulla Adrenal gland Epinephrine and norepinephrine Adrenal medulla cells Capillary

A Map of Referred Pain Heart Lungs and diaphragm Liver Gallbladder Appendix Heart Liver Stomach Pancreas Small intestine Ovaries Colon Kidneys Urinary bladder Ureters -Visceral pain – detected by visceral sensory neurons -No pain results when visceral organs are cut -Visceral pain results from chem. irritation or inflammation -Visceral pain often perceived to be of somatic origin Phenomenon of referred pain

Central Control of the ANS Communication at subconscious level Cerebral cortex (frontal lobe) Limbic system (emotional input) Hypothalamus Overall integration of ANS, the boss Brain stem (reticular formation, etc. ) Regulation of pupil size, respiration, heart, blood pressure, swallowing, etc. Spinal cord Urination, defecation, erection, and ejaculation reflexes

The ANS Throughout Life • Efficiency of the ANS declines with age – Constipation due to reduced mobility of GI tract – Dry eyes due to reduced tear formation – Fight or flight reaction still intact, but may be slowe to respond

Questions…? What’s Next? Lab: PNS & ANS; & Review Next week: Spring Break! Mon 4/8 Lecture: no class study! Mon 4/8 Lab at 8: 00 pm: Lab Exam 3 (You will have sub – Andrew Allen)

Extra…. . Baroreceptor Reflex Increased blood pressure 1 Baroreceptors in carotid sinus are stimulated. 2 Sensory impulses are carried on visceral sensory fibers in the glossopharyngeal nerves (CN IX). 3 2 4 1 3 Integration occurs in cardiac center of medulla oblongata. 4 Efferent pathway via the vagus nerves (CN X) 5 Parasympathetic stimulation of heart decreases heart rate. Blood pressure decreases 5