The Autonomic Nervous System

The autonomic nervous system by Jingying T.A. department of Physiology

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neuron neuronal circuit sensory receptors, and sensory ascending tracts motor neuron, motor regulation motor centers

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autonomic nervous system comparing efferent nerve of ANS to skeletal motor nerve adrenal glands one of the non-specific reflex: “fight or flight ”response

Autonomic nervous system The portion of the nervous system that controls most visceral functions of the body is called the autonomic nervous system.

Visceral functions:  Arterial pressure  Gastrointestinal motility  Gastrointestinal secretion  Urinary bladder emptying  Sweating  Body temperature Etc.

Controlling fashion: rapidly and intensely

1 organization of the autonomic nervous system centers in: spinal cord brain stem hypothalamus visceral reflexes:  organ  autonomic ganglia  brain stem /hypothalamus  organ

ANS: afferent efferent sympathetic NS parasympathetic NS Structurally charactered by ganglia Peripheral portion of the SNS

Autonomic ganglia:  

Para-vertebral g. and pre-vertebral g. Para-organ g. (peripheral)

Comparing the structure of efferent n. between ANS and non-ANS

Skeletal motor n

Autonomic n

Comparing sympathetic n. to skeletal motor n.

1 two neuron levels: Pre-ganglionic & post-ganglionic 2 neuron location

Comparing sympathetic n. to skeletal motor n 3 derivation: segmental 4 passing way 5 effectors: smooth m. cardiac m. glands 6 regulation 7 neuro-transmitters Ach, NE, and neuropeptide

2 autonomic nervous system and their effectors Sympathetic neurons:  derive from T1 to L3;  pre-ganglionic neurons enter the paravertabral ganglia;  post-ganglionic neurons have their axons mixed in the spinal nerves or distributed in the blood walls, to their targets.

parasympathetic neurons:  derive: from nuclei in brain stem , or sacral spinal cord.  pre-ganglionic axons enter into cranial nerves (vagus n.) or pelvic splanchnic nerves.  tagets: vagus: heart, airway, gastro-intestine (to transverse colon) ; pelvic n: the rest of the gut, and bladder.  ganglia: near the controlled organ.

3 autonomic transmitters and receptors Ganglionic transmission: ACh post-ganglionic neuron: n-receptors (nicotine) Post-ganglionic neuron of sympathetic n.: NE receptors: α-: β-: inhibit smooth m. but enhance the cardiac contraction.

Post-ganglionic neuron of parasympathetic n: ACh Receptors: M-receptors (muscarinic) n less widely distributed and little effect on the vasculature or metabolism.

Sympathetic effect parasympathetic (αreceptors)

sympathetic effects (βreceptors)

vasodilatation increased heart rate increased heart contraction Sphincter contraction intestinal relaxation contraction bronchodilatation bronchoconstriction uterine relaxation Sphincter contraction bladder relaxation contraction Pupillary dilatation constriction

effects

Vasoconstriction

decrease HR intestinal

bladder pupillary

Some important autonomic effects lens

axxommodation metabolic stimulation

4 adrenal meddulla adrenal meddulla is the central part of the adrenal glands. 

is regulated by preganglionic sympathetic n.

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n- cholinergic receptors

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effect: secretion of catecholamines (including noradrenaline & adrenaline)

nonadrenaline is potent α- adrenoceptor agonist; adrenaline is potent to both α- and βadrenoceptors. so, resulted in different cardiovascular effects. α-effect: bp hr β-effect: hr bp

5 autonomic reflexes, “fight or flight” autonomic reflexes:  blood pressure control  regulation of gut and bladder motility  regulation of digestive secretion

non specific reflex : fight or flight (anxiety or rage) to prepare the body for vigorous exercise and involves: a generalized increase in sympathetic n activity secretion of adrenal catecholamines

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Cardiovascular effects predominate, with increases in heart rate, blood pressure and skeletal muscle blood flow. Pallor results from cutaneous vasoconstriction. Metabolism is stimulated and sweating increases but gastrointestinal blood flow and motility are reduced. nausea is produced. Alivary secretion is inhibited, making the mouth dry and sticky, and there may be a fine, skeletal muscle tremor.