chapter 33 regulation of the visceral function by the nervous system

Chapter 33

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

Autonomic Nervous SystemAutonomic Nervous System

Including parasympathetic, sympathetic, and enteric divisions.

Coordinates cardiovascular, respiratory, digestive, excretory and reproductive systems.

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

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

muscle and glands Unconscious regulation Target tissues stimulated

or inhibited Two synapses Acetycholine by

preganglionic neurons and ACh or norepinephrine by postganglionic neurons

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

Sympathetic Division

侧副神经节

Parasympathetic DivisionParasympathetic Division

Preganglionic cell bodies in nuclei of brainstem or lateral parts of spinal cord （ S2-S4）– Preganglionic axons

from brain pass to ganglia through cranial nerves

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

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

Parasympathetic Parasympathetic and sympathetic and sympathetic

nerve nerve distributiondistribution

2. Neurotransmitters and 2. Neurotransmitters and NeuroreceptorsNeuroreceptors

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

sympathetic sites, CNS

– 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

Properties of the ANSProperties of the ANSTonic dischargeDouble innervation

– Most blood vessels are innervated only by sympathetic nerves.

– Parasympathetic activity dominates the heart and GI tract.

Dependent on the states of the target organDifferent physiological significance

– Sympathetic nerve: fight and flight reaction– Parasympathetic nerve: Wind down, relaxation, digestion

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,

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

Acetylcholine

• Sympathicus • Fight & Flight

Reaction• Dominated by

Noradrenaline (Adrenaline)

• Fear, exercise, rage

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 Food Intake Water Balance Sleep/wake cycle Emotions and behavior Circadian Endocrine Functions Body Temperature Autonomic Nervous System

Food IntakeFood Intake Ventromedial and Paraventricular Nuclei are satiety centers

– Lesion causes obesity– Through disrupting satiety input to the periventricular nucleus

Lateral HT is feeding center – Stimulation cause food and water intake– Lesion causes starvation behavior– Through damage the medial forebrain bundle, leading to neglect syndrome – no motivation

to eat

Water BalanceWater Balance

Thirst center in the hypothalamus (supraotic nucleus) is stimulated by:– Cellular dehydration– Decreased salivary production– Increased blood osmotic pressure– Decreased blood volume

Thirst center response– Release vasopressin– Cause sensation of thirst

Sleep/Wake CycleSleep/Wake Cycle

suprachiasmatic nuc is biological clock

preoptic nuc can initiate sleep

lateral hypothalamus can change cortical arousal

post hypothalamus lesion can cause coma or impaired

arousal

Emotions and BehaviorEmotions and Behavior

Ventromedial lesions can cause viciousness/rage

Posterior HT stimulates sympathetic functions

Anterior HT stimulates parasympathetic functions

Mamillary nuclei recent memory

Almost all land animals coordinate their behavior

according to circadian rhythms

Suprachiasmatic Nuclei (SCN)

Circadian

Circadian Rhythms of Physiological Functions

Endocrine FunctionEndocrine Function

Regulation of Adenohypophysis

Secretion of Hormones (Vasopressin and Oxytocin)

Functions of the Functions of the HypothalamusHypothalamus

Food intakeWater balanceSleep/wake cycleEmotions and behaviorCircadianEndocrine FunctionBody temperatureAutonomic Nervous System

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