Post on 04-Jan-2016
Physiology of autonomic nervous system
Comparison of 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
Autonomic nervous system
Chain of two motor neurons Preganglionic neuron Postganglionic neuron
Conduction is slower due to thinly or unmyelinated axons
Pre-ganglionic
Ganglion
Post-ganglionic
Comparison of ANS & PNS
Figure 15.2
Compare the one motor neuron of the somatic motor division with the two neuron chain of the autonomic nervous system
Somatic and Autonomic Nervous System
Divisions of ANS There are two division of the ANS
Parasympathetic Sympathetic Metasympathetic
Generally the two divisions have chains of two motor neurons that innervate same visceral organs but cause essentially opposite effects
If one division stimulates certain smooth muscle to contract or a gland to secrete, the other division inhibits that action
Through this process of duel innervation the two systems counterbalance each other
Divisions of ANS Both the sympathetic
and parasympathetic divisions issue from the brain and spinal cord
Two neuron pathways are shown for both divisions
Solid lines indicate pre-ganglionic axons while broken lines indicate post-ganglionic axons
Where they come from
Parasympathetic:craniosacral
Sympathetic:thoracolumbar
N
αβ
SympatheticACh
NE
Nicotine
Tyramine, Ephedrineamphetamine
+
+
Divisions of the Autonomic Nervous System
Sympathetic – “fight, flight, or fright” Activated during exercise,
excitement, and emergencies Parasympathetic – “rest and digest”
Concerned with conserving energy
Functions of the Functions of the Autonomic Nervous Autonomic Nervous SystemSystem
Sympathetic activitiesSympathetic activities
““E situations”E situations” ExerciseExercise EmergencyEmergency ExcitementExcitement EmbarrassmentEmbarrassment
Functions of the Functions of the Autonomic Nervous Autonomic Nervous SystemSystem
Parasympathetic activitiesParasympathetic activities Stimulated by: Stimulated by:
Quiet periodsQuiet periods Paradoxical fearParadoxical fear
Produces “rest-and-digest” responseProduces “rest-and-digest” response Supports body functions that conserve and restore Supports body functions that conserve and restore
body energy body energy Reduce body functions that support physical activityReduce body functions that support physical activity
SLUDD
Function of the Sympathetic Nerve 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 ReactionYou’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.
Sympathetic
Preganglionic cell bodies in lateral horns of spinal cord T1-L2
Sympathetic Trunk Ganglia
Located on both sides of the vertebral column
Linked by short nerves into sympathetic trunks
Joined to ventral rami by white and gray rami communicantes
Fusion of ganglia fewer ganglia than spinal nerves
Sympathetic Pathways to Periphery
Figure 15.9
Sympathetic Pathways to the Head
Figure 15.10
Sympathetic Pathways to Thoracic Organs
Figure 15.11
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• Wind down, relaxation,
digestion• Dominated by
Acetylcholine
• Sympathicus • Fight & Flight Reaction• Dominated by
Noradrenaline (Adrenaline)
• Fear, exercise, rage
Different Lengths of their Fibers
Sympathetic is the opposite with short preganglionic and long postganglionic fibers Parasympathetic division has long preganglionic and short postganglionic fibers
Anatomical Differences in Sympatheticand Parasympathetic Divisions
Figure 15.4a
Divisions of ANS Therefore, all
sympathetic ganglia lie near the spinal cord and vertebral column, and all parasympathetic ganglia lie far from the CNS, in or near the organs innervated
Parasympathetic
Parasympathetic Division
The parasympathetic division is most effective in non-stressful situations
This division is chiefly concerned with keeping body energy use as low as possible, even as it directs body processes such as digestion and elimination
Resting and digesting division
N
M
ACh
ACh
Parasympathetic
Nicotine+
Black widowSpider venom
+
Parasympathetic Nervous System: Sacral Outflow
Emerges from S2-S4
Innervates organs of the pelvis and lower abdomen
Preganglionic cell bodies Located in visceral motor region of
spinal gray matter Form splanchnic nerves
Sacral Outflow The sacral outflow
arises from neurons located in the lateral horn of the spinal cord at S2 - S4
The axons of these neurons run in the ventral roots of the spinal nerves to the ventral rami
Sacral Outflow
From the ventral rami the neurons branch to form the pelvic splanchnic nerves
Most neurons synapse in the intramural ganglia located in the walls of the distal large intestine, urinary bladder and reproductive organs
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
Cholinergic Receptors
The two types of receptors that bind ACh are nicotinic and muscarinic
These are named after drugs that bind to them and mimic ACh effects
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
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