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Download MBBS Anatomy PPT 56 Autonomic Nervous Notes

Download MBBS (Bachelor of Medicine, Bachelor of Surgery) Human Anatomy ppt lectures Topic 56 Autonomic Nervous Notes. - anatomy ppt free download human anatomy ppt lectures, medicine notes ppt, anatomy handwritten notes pdf, mbbs 1st year anatomy notes pdf download, best anatomy notes pdf, human anatomy notes pdf, anatomy easy notes pdf, anatomy notes online, anatomy short notes, Anatomy ppt, Powerpoint Presentations and lecture notes.

This post was last modified on 05 April 2022


Functions

?Sympathetic & parasympathetic divisions typically

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function in opposition to each other.

?But this opposition is better termed

complementary in nature rather than antagonistic.

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?Sympathetic as accelerator and parasympathetic as

brake.

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?Sympathetic quick responses.

?Parasympathetic functions with actions that do not

require immediate reaction.

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?Sympathetic "fight or flight"

?Parasympathetic "rest and digest".

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Autonomic Nervous System

? 2 divisions:

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? Sympathetic

?"Fight or flight"

?"E" division

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? Exercise, Excitement,

Emergency &
Embarrassment

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? Parasympathetic

?"Rest and digest"

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?"D" division

? Digestion, Defecation, &

Diuresis

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Functions

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?Sympathetic & parasympathetic divisions typically

function in opposition to each other.

?But this opposition is better termed

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complementary in nature rather than antagonistic.

?Sympathetic as accelerator and parasympathetic as

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brake.

?Sympathetic quick responses.

?Parasympathetic functions with actions that do not

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require immediate reaction.

?Sympathetic "fight or flight"

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?Parasympathetic "rest and digest".


Receptors

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?Parasympathetic nervous system uses only acetylcholine

(ACh) as its neurotransmitter.

?ACh acts on two types of receptors, muscarinic and

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nicotinic cholinergic receptors.

?Most transmissions occur in two stages:
?When stimulated, preganglionic nerve releases ACh at

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ganglion, which acts on nicotinic receptors of
postganglionic nerve.

?Postganglionic nerve then releases ACh to stimulate

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muscarinic receptors of target organ.
Neurotransmitters

?At effector organs, sympathetic ganglionic neurons release

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noradrenaline (norepinephrine) to act on adrenergic
receptors, with exception of sweat glands and adrenal
medulla:

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?At sweat glands, it is acetylcholine muscarinic receptors.

?At adrenal cortex, there is no postsynapic neuron. Instead

presynaptic neuron releases acetylcholine to act on

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nicotinic receptors.

?Stimulation of adrenal medulla releases adrenaline

(epinephrine) into bloodstream which acts on

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adrenoceptors, producing a widespread increase in
sympathetic activity.

?In parasympathetic system, ganglionic neurons use

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acetylcholine, to stimulate muscarinic receptors.

Sympathetic (adrenergic, with exceptions)

? cardiac output increases

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? SA node: heart rate (chronotropic) 1, 2: increases

? cardiac muscle: contractility (inotropic )1, 2: increases

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? conduction at AV node 1: increases

? vascular smooth muscle M3: contracts; = contracts & 2 =

relaxes

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? smooth muscles of bronchioles 2: relaxes (major

contribution); 1: contracts (minor contribution)

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? pupil of eye 1: relaxes

? ciliary muscle 2: relaxes

? salivary glands: secretions: stimulates viscous, amylase

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secretions; 1 = stimulates potassium cation

? smooth muscles of GI tract - , 2: relaxes

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? sphincters of GI tract - 1: contracts

? glands of GI tract - inhibits
Parasympathetic (muscarinic)

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? cardiac output M2: decreases
? SA node: heart rate (chronotropic) M2: decreases
? cardiac muscle: contractility (inotropic) M2: decreases (atria

only)

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? conduction at AV node M2: decreases
? smooth muscles of bronchioles M3: contracts
? pupil of eye M3: contracts
? ciliary muscle M3: contracts

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? salivary glands: secretions stimulates watery secretions
? GI tract motility M1, M3: increases
? smooth muscles of GI tract M3: contracts
? sphincters of GI tract M3: relaxes
? glands of GI tract M3: secretes

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Autonomic regulation & stress

?A stressful situation activates three major communication

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systems in brain that regulate bodily functions.

?First of these systems is voluntary nervous system, which

sends messages to muscles so that we may respond to

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sensory information.

?Second communication system is autonomic nervous

system. It combines sympathetic or emergency branch,

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which gets us going in emergencies, and parasympathetic
or calming branch, which keeps body's maintenance

systems, such as digestion, in order and calms body's

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responses to the emergency branch.

?Third major communication process is neuroendocrine

system, which also maintains body's internal functioning.

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Specific task

?Emergency branch causes arteries to muscles to relax in

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order to deliver more blood, allowing greater capacity to
act and At same time,reduces blood flow to skin,
kidneys, and digestive tract.

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?In contrast, calming branch helps to regulate bodily

functions and soothe body once stressor has passed,
preventing body from remaining too long in a state of
mobilization.

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?Left mobilized and unchecked, these body functions

could lead to disease. Some actions of calming branch
appear to reduce harmful effects of emergency branch's

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response to stress.

?Various "stress hormones" travel through blood and

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stimulate release of other hormones, which affect bodily
processes such as metabolic rate and sexual functions.

Stress reaction

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? When stress occurs,

sympathetic nervous

system is triggered.

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? Norepinephrine is released

by nerves, and epinephrine

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is secreted by adrenal

glands. By activating

receptors in blood vessels

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and other structures, these

substances ready heart and

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working muscles for action.

? Acetylcholine is released in

parasympathetic nervous

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system, producing calming

effects.

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? Digestive tract is

stimulated to digest a meal,

heart rate slows, and pupils

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of eyes become smaller.

? Neuroendocrine system

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also maintains the body's

normal internal

functioning.

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Chronic stress

?When glucocorticoids or adrenaline are secreted in

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response to prolonged psychological stress commonly
encountered by humans, results are not ideal.

?Normally, bodily systems gear up under stress and release

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hormones to improve memory, increase immune
function, enhance muscular activity and restore
homeostasis.

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?If you are not fighting or fleeing, but standing frustrated

in a supermarket checkout line or sitting in a traffc jam,
you are not engaging in muscular exercise.

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?When stimulated chronically, there are consequences:
?Memory is impaired,
?Immune function is suppressed, and
?Energy is stored as fat.

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Response to stress