The Autonomic Nervous System

1. The Autonomic Nervous System Saja Hamed, Ph.D

2. Autonomic drugs: drugs that produce their primary therapeutic effect by mimicking or altering the functions of the autonomic nervous system. They act by: a. stimulating portions of the ANS b. blocking the action of the autonomic nerves Saja Hamed, Ph.D

3. Nervous system divisions: • CNS (brain & spinal cord) • PNS: • Somatic motor system (Control movement of voluntary muscle) • Autonomic nervous system (Regulate involuntary processes): Parasympathetic Sympathetic Saja Hamed, Ph.D

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9. the adrenal medulla receives pre-ganglionic fibers from the sympathetic system>>>>>secrete the hormone epinephrine (adrenaline) and lesser amounts of norepinephrine into the blood >>>>> influences other organs • Most organs are innervated by both divisions of ANS. e.g. The heart has vagal parasympathetic innervations that slows rate of contraction and sympathetic innervations that speeds contraction • One system usually predominates in controlling the activity of a given organ. e.g.The vagus is the predominant factor for rate. • Adrenal medulla, kidney, pilomotor muscles, blood vessels, and sweat glands >>>> innervations only from sympathetic systems Saja Hamed, Ph.D

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11. Sympathetic division: • Fight or flight response (direct sympathetic activation and stimulation of the adrenal medulla) • Increase heart rate, force of heart contraction, and blood pressure • Mobilize energy stores of the body • The blood vessels that supply nonessential organs constrict, which reduces blood flow through these organs • Blood vessels that supply organs involved in exercise or fighting off danger dilate • Dilation of the pupils and bronchioles Saja Hamed, Ph.D

12. Sympathetic division: • Liver cells breakdown glycogen to glucose, and adipose cells break down triglycerides to F.A and glycerol • Release of glucose by the liver • Processes that are not essential for meeting the stressful situation are inhibited  Saja Hamed, Ph.D

13. Sympathetic division: Functions of the SNS: • regulation of the CVS: increases CO, vasoconstriction of veins and arterioles, • regulation of body temperature: regulate blood flow to skin: - dilating surface vessels  inc blood flow to skin and accelerate heat loss - sweat gland secretion help body cool down - piloerection promote heat conservation • fight or flight reaction • Therapeutic agents that alter functions under sympathetic control are used primarily for effects on heart (Hypertension, heart failure, angina pectoris), blood vessels, and lungs (Primarily for asthma). Saja Hamed, Ph.D

14. Parasympathetic division • Maintains essential bodily functions such as digestive processes and elimination of wastes • SLUDD • Three decreases • Dominant over the sympathetic system in “rest and digest” situations Saja Hamed, Ph.D

15. Functions of the PSNS (house keeping chores): • slowing of heart rate • increased gastric secretion • emptying of the bladder • emptying of the bowel • focusing of the eye for the near vision • constriction of the pupil • contraction of bronchial smooth muscle • Therapeutic agents that work by altering PSNS function are used primarily for their effects on GIT, the bladder, and the eye Saja Hamed, Ph.D

16. Chemical signaling between cells: • Hormones: Endocrine cells secret hormones into blood stream and thruogh blood they travel to broadly distributed target cells • Neurotransmitters: - chemical substances released by neurons at synapses - their signals are mediated by binding to specific receptors on cell surface of target organs Saja Hamed, Ph.D

17. Cholinergic and adrenergic neurotransmitters: The autonomic nerve fibers can be classified into two groups based on NT released A. Acetylcholine: - all sympathetic and parasympathetic preganglionic neurons - all parasympathetic postganglionic neurons - a few sympathetic postganglionic neurons B. Norepinephrine and epinephrine: - Most sympathetic postganglionic neurons use NE Saja Hamed, Ph.D

18. Neurotransmitter receptors are membrane proteins that provide a binding site that recognizes and responds to neurotransmitter molecules • Binding of chemical signals to receptors activates enzymatic processes within the cell membrane that result in cellular response Saja Hamed, Ph.D

19. some receptors are directly linked to membrane ion channels •  Some receptors are not directly coupled to ion gates: - Second messenger: Molecules that intervene between the original message (NT, hormones) and the effect in the cell. Part of the cascade of events that translate NT binding into a cellular response Saja Hamed, Ph.D

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