Section 5

Regulation of the Visceral Function by the Nervous System

I Autonomic Nervous SystemI Autonomic Nervous System

1. Basic of the Anatomy1. Basic of the Anatomy

ANSANS

We subdivide the ANS into the parasympathetic, sympathetic, and enteric divisions.

The enteric system is essentially an independent nervous system responsible for regulation of digestive functions.

The ANS coordinates cardiovascular, respiratory, digestive, excretory and reproductive systems.

Somatic and Autonomic Nervous System

Somatic and Autonomic Somatic and Autonomic Nervous SystemNervous System

Somatic Skeletal muscle Conscious and

unconscious movement Skeletal muscle contracts One synapse Acetylcholine

Autonomic Smooth and cardiac muscl

e and glands Unconscious regulation Target tissues stimulated o

r inhibited Two synapses Acetycholine by pregangli

onic neurons and ACh or norepinephrine by postganglionic neurons

Preganglionic cell bodies in lateral horns of spinal cord T1-L2

Sympathetic Division

Parasympathetic DivisionParasympathetic Division

Preganglionic cell bodies in nuclei of brainstem or lateral parts of spinal cord gray matter from S2-S4– Preganglionic axons fro

m brain pass to ganglia through cranial nerves

– Preganglionic axons from sacral region pass through pelvic nerves to ganglia

Preganglionic axons pass to terminal ganglia within wall of or near organ innervated

Parasympathetic Parasympathetic and sympathetic and sympathetic

nerve nerve distributiondistribution

2. Neurotransmitters and Neurorecep2. Neurotransmitters and Neuroreceptorstors

Acetylcholine and Norepinephrine

All preganglionic neurons are cholinergic

Parasympathetic post ganglionic neurons are cholinergic

Sympathetic post ganglionic neurons are adrenergic except

Sympathetics innervating sweat glands, blood vessels in skeletal muscle, and piloerection muscles are cholinergic

NeurotransmittersNeurotransmitters

ACh AChSweatglands

Striatedmuscle

AChSOMATIC NERVOUS SYSTEM

HeartSm. mus.Glands

ACh AChParasympathetic

ACh E, NE

Ad. M.

HeartSm. mus.Glands

ACh NE

AUTONOMIC NERVOUS SYSTEM

Sympathetic

AcetylcholineAcetylcholine

Nicotinic receptors– Nm (muscular-type or N2): skeletal muscle

– Nn (neuron-type, or N1): autonomic ganglia, CNS

Muscarinic receptors– Postganglionic parasympathetic and a few sym

pathetic sites, CNS (also autonomic gang.)

– Receptor subtypes: M1-5

CatecholaminesCatecholamines Norepinephrine

– Postganglionic sympathetic, CNS, adrenal medulla– Receptors: 1, 2, 1

Epinephrine– Adrenal medulla, CNS– Receptors: 1, 2, 1 , 2

Dopamine– Autonomic ganglia, CNS– Receptors: D(1-5), 1, 1

Location of ANS ReceptorsLocation of ANS Receptors

3 Function of the Sympathetic and Parasympathetic Nerve

SNSSNS

Sympathetic nervous system prototypically “fight” or “flight”.

Associated with increased

energy expenditure,

cardiopulmonary adjustments for intense activity,

blood flow adjustments for maximum energy expenditure.

SNS - SNS - Fight & Flight ReactionFight & Flight Reaction

You’re walking alone at night and all the sudden you hear an unfamiliar noise near by… In a matter of seconds,

your heart rate increases dramatically, blood vessels in your skeletal muscles dilate, blood vessels in the visceral muscles constrict, digestion is ceased, your liver ramps up glucose release, your pupils dilate, salivary production decreases, sweat increases.

Parasympathetic Nervous Parasympathetic Nervous SystemSystem

If that noise turns out to be the result of wind, then the body is returned to “pre-noise” state.

This is the job of the parasympathetic nervous system.

Autonomic Nervous System• Parasympathicus• Wind down, relaxation,

digestion• Dominated by Acetylc

holine

• Sympathicus • Fight & Flight Reactio

n• Dominated by Noradre

naline (Adrenaline)• Fear, exercise, rage

Interactions of the ANSInteractions of the ANSMost visceral organs are innervated by both types of nerves.Most blood vessels are innervated only by sympathetic nerves. PS activity dominates the heart and GI tract.Activation of the sympathetic division causes wide spread,

long-lasting mobilization of the fight-or-flight response. PS effects are highly localized and short lived.

1. Spinal cord

bladder and rectum reflex (micturition and defecation)

the baroreceptor reflex,

sweating of the skin 

II. Central Regulation of Visceral Function

2. Medulla oblongata

Vital (respiratory and cardiovascular) center:

Other autonomic reflexes: Swallow, cough, sneeze, gag, and vomit.

Tu :19.17

 3. Hypothalamus

Hypothalamic FunctionsHypothalamic Functions

1). Body temperature: heat loss center in anterior HT (preoptic area)

stimulates sweating and peripheral vasodilation, lesions cause hyperthermia;

heat gain center in posterior HT stimulates cutaneous vasoconstriction, piloerection, shiv

ering; lesions cause poikilothermy(the difference between poikilothermal or cold-blooded a

nimal and homoiothermal or warm-blooded animal)

2). Food intake:

ventromedial and paraventricular nuclei are satiety centers, lesion causes obesity; lateral HT (feeding center) stimulates food and water intake

Hypothalamic Functions

3) Water balance

ADH (vasopressin)

Osmotic pressure in hypothalamus – Thirst - Drink

Hypothalamus Functions

4) Sleep/wake cycle: suprachiasmatic nuc is biological clock; preoptic nuc can initiate sleep; lat HT can change cortical arousal; post HT lesion can cause coma or impaired arousal

Hypothalamus FunctionsHypothalamus Functions

5). Emotions and behavior: ventromedial lesions can cause viciousness/rage Posterior HT stimulates sympathetic functions Anterior HT stimulates parasympathetic functions Mamillary nuclei: recent memory

6). Circadian:

Almost all land animals coordinate their behavior according to circadian rhythms, the daily cycles of lightness and darkness that result from the spin of the earth.

Most if not all living organisms have rhythmic fluctuation in bodily function that are about 24 hs in length. (sleep-wake, and body temperature cycles).

Suprachiasmatic muclei (SCN)

Hypothalamus Functions

Circadian rhythms of physiological

functions.

7) Regulation of the Endocrine Function

Hypothalamus Functions

4 Influence of Brain on 4 Influence of Brain on Autonomic FunctionsAutonomic Functions

III Function of Sympathetic and Parasympathetic nerve on the target organs

Physiology Physiology (Table 5-1)(Table 5-1)

Effector Sympathetic ParasympatheticRadialmuscle

Contraction(mydriasis, 1)

—

Sphinctor — Contraction(miosis)

Ciliarymuscle

Slight relaxa-tion (2)

Contraction (nearvision)

Eye

Cornea

Lens

Ciliary muscle

Iris

SA node

Atria

AV node

Ventricles

Heart

Effector Sympathetic ParasympatheticSA node Tachycardia

(1,2)Bradycardia

Atria contractilityand conduction(1,2)

contractility, conduction(usually)

AV node conductionand auto-maticity (1,2)

conduction

Ventricles contractility,conduction, andautomaticity(1,2,1)

—

Effector Sympathetic ParasympatheticSkin andmucosa

Constriction(1,2)

Dilation (?)

Skeletalmuscle

Constriction(), dilation(2)

—

Salivaryglands

Constriction(1,2)

Dilation

Erectiletissue

Constriction()

Dilation

Blood vessels

Effector Sympathetic ParasympatheticBronchialsm. musc.

Relaxation (2) Constriction

Bronchialglands

(1), (2),secretion

secretion

Salivaryglands

Viscous,amylasesecretion(1,1,2)

Profuse waterysecretion

Lungs and salivary glands

Effector Sympathetic ParasympatheticSmoothmuscle

motility andtone(1,2,1,2)

motility andtone

Sphincters Contraction(1)

Relaxation

Secretions secretion (2) secretionLiver Glycogenolysis,

gluconeogene-sis (1,2)

Glycogensynthesis

Gastrointestinal tract and liver