section 5 regulation of the visceral function by the nervous system
TRANSCRIPT
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 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
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
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.
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
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
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