PERIPHERAL & AUTONOMICPERIPHERAL & AUTONOMICNERVOUS SYSTEMSNERVOUS SYSTEMS

Human AnatomyHuman Anatomy

Sonya Schuh-Huerta, Ph.D.Sonya Schuh-Huerta, Ph.D.

Leonardo Da Vinci, The Battle of Anghiari

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)

Motor (efferent) divisionSensory (afferent) division

Sympatheticdivision

Parasympatheticdivision

Somatic sensoryGeneral: Touch, pain, pressure, vibration, temperature, and proprioception in skin, body wall, and limbs

Special: Hearing, equilibrium, vision

Visceral sensoryGeneral: Stretch, pain, temperature, chemical changes, and irritation in viscera; nausea and hunger

Special: Taste, smell

Somatic nervoussystem

Motor innervation of all skeletal muscles

Autonomicnervous system

(ANS)

Motor innervationof smooth muscle, cardiac muscle, and glands

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

Frontal lobe

Temporal lobe

Infundibulum

Facial (VII)

Vestibulocochlear (VIII)

Glossopharyngeal (IX)

Vagus (X)

Accessory (XI)

Hypoglossal (XII)

Filaments ofolfactory nerve (I)

Olfactory bulb

Olfactory tract

Optic chiasma

Optic nerve (II)

Optic tract

Oculomotor (III)

Trochlear (IV)

Trigeminal (V)

Abducens (VI)

Cerebellum

Medulla oblongata

The Cranial Nerves

Cranial nerves

I

II

III

IV

V

VI

Olfactory

Optic

Oculomotor

Trochlear

Trigeminal

Abducens

Vision

General

Smell

Somaticsensory

(SS)

Visceralsensory

(VS)

Somaticmotor(SM)

Visceral motor:parasympathetic

(VM)

SM

SM

SM

SM

VM

Sensory function Motor function

OdessaOfeliaO’ConnerTakesTestsAmazingly!

The Cranial Nerves

Cranial nerves Sensory function Motor function

VII

VIII

IX

X

XI

XII

Facial

Vestibulocochlear

Glossopharyngeal

Vagus

Accessory

Hypoglossal

General;taste

General;taste

General

General

General;taste

General

Hearing;equilibrium

SM

Some

SM

SM

SM

SM

VM

VM

VM

Somaticsensory

(SS)

Visceralsensory

(VS)

Somaticmotor(SM)

Visceral motor:parasympathetic

(VM) FiestyVictorGetsVeryAgitatedHere…

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 C8, T12, L5, S5, Cx1 = 31

• Connect to spinal cord• Named for region of vertebral column

– 8 pairs cervical nerves (C1–C8)

– 12 pairs thoracic nerves (T1–T12)

– 5 pairs lumbar nerves (L1–L5)

– 5 pairs sacral nerves (S1–S5)

– 1 pair coccygeal nerves (Cx1)

Spinal Nerves – Posterior View

CervicalnervesC1 – C8

ThoracicnervesT1 – T12

LumbarnervesL1 – L5

SacralnervesS1 – S5 Coccygeal

nerveCo1

Cervical plexus

Intercostalnerves

Cervicalenlargement

Lumbarenlargement

Cauda equina

Brachial plexus

Lumbar plexus

Sacral plexus

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

Spinalnerve

Axon ofmotorneuron

Ventralramus

Ventralroot

Neuromuscularjunction

Sensory receptors inskin (e.g., free nerveendings of sensoryneuron)

Dorsal rootDorsal rootganglion

Dorsalramus

Sensory axonand cell body

Nerves

Spinal Nerves

Dorsal rootganglion

Gray matterWhite matter

Ventral root

Dorsal root

Dorsal & ventralrootlets of spinal nerve

Dorsal ramusof spinal nerve

Ventral ramusof spinal nerve

Sympathetic trunkganglion

Spinal nerve

Rami communicantes

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 T2–T12)

– 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

Hypoglossalnerve (XII)

C1

C2

C3

C4

C5

Segmentalbranches

Lesser occipitalnerve

Greater auricularnerve

Ansa cervicalis

Phrenic nerve

Supraclavicularnerves

Accessory nerve (XI)

Transversecervical nerve

Ventralrami:

Ventral rami

The Brachial Plexus & Innervation of the Upper Limb

• Brachial plexus lies in the neck & axilla

• Formed by ventral rami of C5–C8

• Cords give rise to main nerves of upper limb

(c) Flowchart summarizing relationships within the brachial plexus

Major terminalbranches(peripheral nerves)

Cords Divisions TrunksRoots(ventralrami)

Musculocutaneous

Median

Ulnar

Radial

Axillary

C5

C6

C7

C8

T1

Anterior

Posterior

Anterior

Posterior

Posterior

Anterior

Upper

Middle

Lower

Lateral

Medial

Posterior

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

Median nerve

Musculocutaneous nerve

Radial nerve

Humerus

Ulna

Ulnar nerve

Median nerve

Radius

Radial nerve (superficial branch)

Superficial branch of ulnar nerve

Dorsal branch of ulnar nerve

Digital branch of ulnar nerve

Muscular branch

Digital branch

Axillary nerve

Anteriordivisions

Posteriordivisions

Radial nerve

Branches of axillary nerve

Axillary nerve

Ulnar nerve (cut)Median nerve (cut)

Deep radial nerve

Posterior cutaneous nerve

Superficial branch of radial nerve

Anteriordivisions

Posteriordivisions

Major Nerves of the Upper Limb

The Lumbar Plexus & Innervation of the Lower Limb

• Lumbar plexus – Arises from L1– L4

– Main branches innervate the anterior thigh• Femoral nerve innervates anterior thigh

muscles• Obturator nerve innervates adductor muscles

The Lumbar Plexus & Nerves

Lateral femoralcutaneous

Anterior femoralcutaneous

Saphenous

Obturator

Iliohypogastric

Ilioinguinal

Femoral

(c) Distribution of the major nerves from the lumbar plexus to the lower limb

The Sacral Plexus

• Arises from spinal nerves L4–S4

• 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

Common fibular

Deep fibular

Superficial fibular

Plantar branches

Tibial

Sural (cut)

Posterior femoralcutaneous

Pudendal

Sciatic

(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 C5-C8– 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

C2C3

C4

C5T1

T2

T2T3T4T5

C6

C8C7 C7

C6

T6T7T8T9

T10

T11

T12L1

S2S3

L1

L2

L3

L4

L5

L2

L3

L4

L5

S1

C6

C5

C8

T2

C6

C5

S1

C2

C3

C4C5C6C7C8

C8 C8

C7 C7

T1T2T3T4T5T6T7T8T9T10

T11T12

L1L2 L3

S1

(b) Posterior view

L5S2

S1

S1

S3

S2 S1S2

S4S5

L5L5

L4L5L5

L4

C6 C6

L4

L3

L2

L1

L4

Map of Dermatomes

(a) Anterior 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

• Issue from different regions of the CNS:

– Sympathetic also called thoracolumbar division

– Parasympathetic also called the craniosacral division

Anatomical Differences in Sympathetic & Parasympathetic Divisions

Salivaryglands

Eye

Skin*

Heart

Lungs

Liverand gall-bladder

Genitals

Pancreas

Eye

Lungs

Bladder

Liver and gall-bladder

Pancreas

Stomach

Cervical

Sympatheticganglia

Cranial

Lumbar

Thoracic

Genitals

Heart

Salivaryglands

Stomach

Bladder

Adrenalgland

Parasympathetic Sympathetic

Sacral

Brain stem

L1

T1

• 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)

Anatomical Differences in Sympathetic& Parasympathetic Divisions

Differences Between Sympathetic & Parasympathetic Divisions

Skeletal muscle

Cell bodies in centralnervous system Peripheral nervous system Effect

Effectororgans

ACh

AChSmooth muscle(e.g., in gut), glands,cardiac muscle

Ganglion

Adrenal medulla Blood vessel

ACh

ACh

ACh

NE

Epinephrine andnorepinephrine

Ganglion

Heavily myelinated axon

Lightly myelinated preganglionic axon

Lightly myelinated preganglionic axons

Neurotransmitterat effector

Unmyelinatedpostganglionic axon

Unmyelinatedpostganglionic axon

Stimulatory

Stimulatoryor inhibitory,dependingon neuro-transmitterand receptorson effectororgans

Single neuron from CNS to effector organs

Two-neuron chain from CNS to effector organs

SO

MA

TIC

NER

VO

US

SYS

TEM

AU

TO

NO

MIC

NER

VO

US

SYS

TEM

PA

RA

SYM

PA

TH

ETIC

SYM

PA

TH

ETIC

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

Eye

Lacrimalgland

Nasalmucosa

Ciliary ganglion

Pterygopalatineganglion

Submandibularganglion

Submandibularand sublingualglands

CN III

CN VII

CN IXCN X

Otic ganglion

Parotid gland

Heart

Lung

Cardiac and pulmonary plexuses

Preganglionic

Postganglionic

Cranial nerveCN

Liver andgallbladder

Stomach

Pancreas

Urinary bladder and ureters

Smallintestine

Large intestine

S2

Pelvicsplanchnicnerves

Genitalia (penis, clitoris, and vagina)

Rectum

Celiacplexus

Inferiorhypogastric plexus

S4

Preganglionic

Postganglionic

Cranial nerveCN

Parasympathetic Division – Sacral Outflow

The Sympathetic Division

• Basic organization– Issues from T1–L2

– 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

Superiorcervicalganglion

Middlecervicalganglion

Inferiorcervicalganglion

Sympathetic trunk(chain) ganglia

Pons

L2

T1

White ramicommunicantes

Liver and gallbladder

Stomach

Spleen

Kidney

Adrenal medulla

Smallintestine

Largeintestine

Genitalia (uterus, vagina, andpenis) and urinary bladder

Celiac ganglion

Inferiormesenteric ganglion

Lesser splanchnic nerveGreater splanchnic nerve

Superiormesentericganglion

Lumbarsplanchnicnerves

EyeLacrimal gland

Nasal mucosa

Blood vessels;skin (arrector pilimuscles andsweat glands)

Salivary glands

Heart

Lung

Rectum

Cardiac and pulmonaryplexuses

PreganglionicPostganglionic

Sacralsplanchnicnerves

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

Spinal cord

Dorsal root

Ventral root

Sympathetictrunk ganglion

Sympathetictrunk

Rib

Ventral ramusof spinal nerve

Gray ramuscommunicans

White ramuscommunicans

Thoracicsplanchnic nerves

(a) Location of the sympathetic trunk

To effector

Blood vessels

Skin (arrectorpili musclesand sweatglands)

Dorsal root ganglion

Dorsal ramus ofspinal nerve

Dorsal root

Sympathetictrunk ganglion

Lateral horn(visceralmotor zone)

Ventral root

Sympathetic trunk

Gray ramuscommunicansWhite ramuscommunicans

Ventral ramus ofspinal nerve

Synapse at the same level1

Splanchnic nerve

Collateral ganglion(such as the celiac)

Target organin abdomen(e.g., intestine)

Synapse in a distant collateral ganglion anterior to the vertebral column

(b) Three pathways of sympathetic innervation

3

Sympathetic Trunk Ganglia

2

To effector

Blood vessels

Skin (arrectorpili musclesand sweatglands)

Synapse at a higher or lower level

Autonomic Nerves, Plexuses & GangliaLeft vagus nerve

Cardiac branches of the vagus

TracheaThoracic spinalnerves (ventral rami)

Cardiac plexusPulmonary plexuson the bronchus

Vagus nerveEsophageal plexus

DiaphragmStomach withvagus nerveCeliac ganglion and plexus

Superior mesentericganglion and plexus

Inferior mesentericganglion and plexus

Aortic plexus

Inferior hypogastric(pelvic) plexus

Pelvic sympathetictrunk

Superior cervicalganglion

Middle cervical ganglion

Sympathetic cardiac nerves

Stellate ganglion

Aortic arch

Sympathetictrunk ganglia

Esophagus

Thoracicsplanchnicnerves

Adrenal(suprarenal)gland

Kidney

Lumbarand sacral splanchnicnerves

Superior hypogastricplexus

Aorta

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

Spinal cord:T8–L1

Adrenalmedulla cells

Sympathetic trunk

Ventralroot

Thoracicsplanchnicnerves

Epinephrine andnorepinephrine

Adrenal glandAdrenalmedulla

Capillary

Kidney

A Map of Referred Pain

Heart

Lungs anddiaphragm

Liver

Stomach

Kidneys

Ovaries

Small intestine

Ureters

Urinarybladder

Colon

Pancreas

Liver

Heart

Appendix

Gallbladder

-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

Cerebral cortex(frontal lobe)

Limbic system(emotional input)

Communication atsubconscious level

HypothalamusOverall integrationof ANS, the boss

Spinal cordUrination, defecation,

erection, and ejaculationreflexes

Brain stem(reticular formation, etc.)

Regulation of pupil size,respiration, heart, blood

pressure, swallowing, etc.

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

slower to respond

Questions…?

What’s Next?Lab: PNS & ANS; & ReviewNext 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)

Baroreceptor Reflex

Increased blood pressure

Blood pressure decreases

Sensory impulses are carried on visceral sensory fibers in the glossopharyngeal nerves (CN IX).

Integration occurs in cardiac center of medulla oblongata.

Baroreceptors in carotid sinus are stimulated.

Parasympathetic stimulation of heart decreases heart rate.

Efferent pathway via the vagus nerves (CN X)

1

2

3

4

5

1

2

3

4

5

Extra…..