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.
Functions
?Sympathetic & parasympathetic divisions typically
function in opposition to each other.
?But this opposition is better termed
complementary in nature rather than antagonistic.
?Sympathetic as accelerator and parasympathetic as
brake.
?Sympathetic quick responses.
?Parasympathetic functions with actions that do not
require immediate reaction.
?Sympathetic "fight or flight"
?Parasympathetic "rest and digest".
Autonomic Nervous System
? 2 divisions:
? Sympathetic
?"Fight or flight"
?"E" division
? Exercise, Excitement,
Emergency &
Embarrassment
? Parasympathetic
?"Rest and digest"
?"D" division
? Digestion, Defecation, &
Diuresis
Functions
?Sympathetic & parasympathetic divisions typically
function in opposition to each other.
?But this opposition is better termed
complementary in nature rather than antagonistic.
?Sympathetic as accelerator and parasympathetic as
brake.
?Sympathetic quick responses.
?Parasympathetic functions with actions that do not
require immediate reaction.
?Sympathetic "fight or flight"
?Parasympathetic "rest and digest".
Receptors
?Parasympathetic nervous system uses only acetylcholine
(ACh) as its neurotransmitter.
?ACh acts on two types of receptors, muscarinic and
nicotinic cholinergic receptors.
?Most transmissions occur in two stages:
?When stimulated, preganglionic nerve releases ACh at
ganglion, which acts on nicotinic receptors of
postganglionic nerve.
?Postganglionic nerve then releases ACh to stimulate
muscarinic receptors of target organ.
Neurotransmitters
?At effector organs, sympathetic ganglionic neurons release
noradrenaline (norepinephrine) to act on adrenergic
receptors, with exception of sweat glands and adrenal
medulla:
?At sweat glands, it is acetylcholine muscarinic receptors.
?At adrenal cortex, there is no postsynapic neuron. Instead
presynaptic neuron releases acetylcholine to act on
nicotinic receptors.
?Stimulation of adrenal medulla releases adrenaline
(epinephrine) into bloodstream which acts on
adrenoceptors, producing a widespread increase in
sympathetic activity.
?In parasympathetic system, ganglionic neurons use
acetylcholine, to stimulate muscarinic receptors.
Sympathetic (adrenergic, with exceptions)
? cardiac output increases
? SA node: heart rate (chronotropic) 1, 2: increases
? cardiac muscle: contractility (inotropic )1, 2: increases
? conduction at AV node 1: increases
? vascular smooth muscle M3: contracts; = contracts & 2 =
relaxes
? smooth muscles of bronchioles 2: relaxes (major
contribution); 1: contracts (minor contribution)
? pupil of eye 1: relaxes
? ciliary muscle 2: relaxes
? salivary glands: secretions: stimulates viscous, amylase
secretions; 1 = stimulates potassium cation
? smooth muscles of GI tract - , 2: relaxes
? sphincters of GI tract - 1: contracts
? glands of GI tract - inhibits
Parasympathetic (muscarinic)
? cardiac output M2: decreases
? SA node: heart rate (chronotropic) M2: decreases
? cardiac muscle: contractility (inotropic) M2: decreases (atria
only)
? conduction at AV node M2: decreases
? smooth muscles of bronchioles M3: contracts
? pupil of eye M3: contracts
? ciliary muscle M3: contracts
? 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
Autonomic regulation & stress
?A stressful situation activates three major communication
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
sensory information.
?Second communication system is autonomic nervous
system. It combines sympathetic or emergency branch,
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
responses to the emergency branch.
?Third major communication process is neuroendocrine
system, which also maintains body's internal functioning.
Specific task
?Emergency branch causes arteries to muscles to relax in
order to deliver more blood, allowing greater capacity to
act and At same time,reduces blood flow to skin,
kidneys, and digestive tract.
?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.
?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
response to stress.
?Various "stress hormones" travel through blood and
stimulate release of other hormones, which affect bodily
processes such as metabolic rate and sexual functions.
Stress reaction
? When stress occurs,
sympathetic nervous
system is triggered.
? Norepinephrine is released
by nerves, and epinephrine
is secreted by adrenal
glands. By activating
receptors in blood vessels
and other structures, these
substances ready heart and
working muscles for action.
? Acetylcholine is released in
parasympathetic nervous
system, producing calming
effects.
? Digestive tract is
stimulated to digest a meal,
heart rate slows, and pupils
of eyes become smaller.
? Neuroendocrine system
also maintains the body's
normal internal
functioning.
Chronic stress
?When glucocorticoids or adrenaline are secreted in
response to prolonged psychological stress commonly
encountered by humans, results are not ideal.
?Normally, bodily systems gear up under stress and release
hormones to improve memory, increase immune
function, enhance muscular activity and restore
homeostasis.
?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.
?When stimulated chronically, there are consequences:
?Memory is impaired,
?Immune function is suppressed, and
?Energy is stored as fat.
Response to stress
This post was last modified on 05 April 2022