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Section 5
Regulation of the Visceral Function by the
Nervous System
I Autonomic Nervous System
1. Basic of the Anatomy
ANS

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
Nervous 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
Sympathetic
Division

Preganglionic cell bodies in lateral horns of spinal cord T1-L2
Parasympathetic Division

Preganglionic axons
organ innervated
Preganglionic cell bodies in
nuclei of brainstem or
lateral parts of spinal cord
gray matter from S2-S4
– Preganglionic axons
from brain pass to
ganglia through cranial
nerves
– Preganglionic axons
from sacral region pass
through pelvic nerves to
ganglia
pass to terminal ganglia within wall of or near
Parasympathetic
and sympathetic
nerve
distribution
2. Neurotransmitters and
Neuroreceptors

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
Neurotransmitters
SOMATIC NERVOUS SYSTEM
AUTONOMIC NERVOUS SYSTEM
Sympathetic
ACh
ACh
ACh
Parasympathetic
Ad. M. 
ACh
ACh
Striated
muscle
NE
Heart
Sm. mus.
Glands
ACh
Sweat
glands
ACh
Heart
Sm. mus.
Glands
E,

NE
Acetylcholine

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 (also autonomic gang.)
– Receptor subtypes: M1-5
Catecholamines

Norepinephrine
– Postganglionic sympathetic, CNS, adrenal medulla
– Receptors: a1, a2, b1

Epinephrine
– Adrenal medulla, CNS
– Receptors: a1, a2, b1 , b2

Dopamine
– Autonomic ganglia, CNS
– Receptors: D(1-5), a1, b1
Location of ANS Receptors
3 Function of the Sympathetic and
Parasympathetic Nerve
SNS

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 - Fight & 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
System

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
• Sympathicus
• Wind down, relaxation,
digestion
• Dominated by
Acetylcholine
• Fight & Flight
Reaction
• Dominated by
Noradrenaline
(Adrenaline)
• Fear, exercise, rage
Interactions of the ANS

Most 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-orflight response.
 PS effects are highly localized and short lived.
II. Central Regulation of Visceral Function
1. Spinal cord
 bladder and rectum reflex (micturition and
defecation)
 the baroreceptor reflex,
 sweating of the skin
2. Medulla oblongata
 Vital (respiratory and cardiovascular) center:
 Other autonomic reflexes: Swallow, cough, sneeze,
gag, and vomit.
3. Hypothalamus
Tu :19.17
Hypothalamic 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,
shivering;
 lesions cause poikilothermy
 (the difference between poikilothermal or cold-blooded
animal and homoiothermal or warm-blooded animal)
Hypothalamic Functions
2). Food intake:
ventromedial and paraventricular nuclei are satiety
centers,
lesion causes obesity;
lateral HT (feeding center) stimulates food and water
intake
Hypothalamus Functions
3) Water balance
ADH (vasopressin)
Osmotic pressure in hypothalamus – Thirst - Drink
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 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
Hypothalamus Functions
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)
Circadian
rhythms of
physiologic
al
functions.
Hypothalamus Functions
7) Regulation of the Endocrine Function
4 Influence of Brain on
Autonomic Functions
III Function of Sympathetic and
Parasympathetic nerve on the
target organs
Physiology
(Table 5-1)
Eye
Effector
Radial
muscle
Sphinctor
Ciliary
muscle
Cornea
Iris
Lens
Ciliary
muscle
Sympathetic
Parasympathetic
Contraction
—
(mydriasis, a1)
—
Contraction
(miosis)
Slight relaxa- Contraction (near
tion (b2)
vision)
Heart
Atria
SA node
AV node
Ventricles
Effector
SA node
Atria
AV node
Ventricles
Sympathetic
Tachycardia
(b1,b2)
contractility
and conduction
(b1,b2)
conduction
and automaticity (b1,b2)
contractility,
conduction, and
automaticity
(b1,b2,a1)
Parasympathetic
Bradycardia
contractility,
conduction
(usually)
conduction
—
Blood vessels
Effector
Skin and
mucosa
Skeletal
muscle
Salivary
glands
Erectile
tissue
Sympathetic
Constriction
(a1,a2)
Constriction
(a), dilation
(b2)
Constriction
(a1,a2)
Constriction
(a)
Parasympathetic
Dilation (?)
—
Dilation
Dilation
Lungs and salivary glands
Effector
Bronchial
sm. musc.
Bronchial
glands
Salivary
glands
Sympathetic
Parasympathetic
Relaxation (b2) Constriction
(a1),(b2),
secretion
Viscous,
amylase
secretion
(a1,b1,b2)
secretion
Profuse watery
secretion
Gastrointestinal tract and liver
Effector
Smooth
muscle
Sympathetic
Parasympathetic
motility and motility and
tone
tone
(a1,a2,b1,b2)
Sphincters Contraction
Relaxation
(a1)
Secretions secretion (a2) secretion
Liver
Glycogenolysis, Glycogen
gluconeogene- synthesis
sis (a1,b2)