Autonomic nervous system (ANS)2


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Introduction to Autonomic nervous system

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Autonomic nervous system (ANS)2

  1. 1. Saddam Ansari2nd YearTbilisi State Medical UniversityAutonomic Nervous System (ANS)
  2. 2. Parasympathetic divisionCraniosacraldivisionCranial portioninnervates Blood vessels ofhead and neck Thoracoabdominalvisceral organs
  3. 3. Continued…Sacral portioninnervates Smooth musclesforming the walls ofviscera Glands Large intestine Liver, spleen, kidneys,bladder, genitalia
  4. 4. Characteristics of Sympatheticand Parasympathetic FunctionNeurotransmitters of ANS Cholinergic and Adrenergic Fibers
  5. 5. Synthesis of Acetylcholine Synthesized in terminal endings of cholinergicfibers. Most of the synthesis occurs in axoplasmoutside the vesicles.
  6. 6. Destruction of Acetylcholine
  7. 7. Synthesis of Norepinephrine Synthesis begins in axoplasm of terminal nerveendings of adrenergic nerve fibers But its completed in vesicles In adrenal medulla 80 % of norepinephrine istransformed in epinephrine
  8. 8. Continued…
  9. 9. Continued…After secretion of NE, it is removed fromthe site by three ways:1. Reuptake into adrenergic nerve endings byactive transport process (50 to 80 % of NE)2. Diffusion away from the nerve endings intothe body fluids and then to the blood (remainingNE)
  10. 10. Continued…3. Destruction of small amount by tissueenzyme:Monoamine oxidaseCatechol-O-methyl transferase (occursmainly in liver)
  11. 11. Receptors on Effector Organs To stimulate effector organ, neurotransmittersmust bind with receptors on the effector cells Receptors are present outside the cellmembrane that penetrates cell membrane Binding causes conformational change in theprotein In turn, altered protein molecule excites orinhibits the cell, most often by 2 means :
  12. 12. Continued…1.Causing a change in the cellmembrane permeability to one or moreions2. Activating or inactivating an enzymeattached to the other end of the receptorprotein
  13. 13. Types of Acetylcholine ReceptorsMainly 2 types1.Muscarinic Origin- Muscarine means poison fromtoadstool Activates only muscarinic receptors Found on all effector cells stimulated byparasympathetic nervous system And also stimulated by cholinergicneurons of sympathetic system
  14. 14. Continued…2.Nicotinic Found at synapses between the pre andpostganglionic neurons of both sympathetic andparasympathetic system Also present at nonautonomic nerve endings e.g.neuromuscular junction in skeletal muscle Activated by nicotine , not muscarineNOTE: Acetylcholine can activate both of thereceptors.
  15. 15. Adrenergic ReceptorsAlpha Receptors (alpha1 andalpha2)Beta Receptors (beta1 and beta2 and beta 3)
  16. 16. Function of Alpha Receptors Vasoconstriction Iris dilation Intestinal relaxation Intestinal sphincter contraction Pilomotor contraction Bladder sphincter contraction
  17. 17. Function of Beta Receptors Vasodilation -beta 2 Cardioacceleration – beta 1 Increased myocardial strength – beta 1 Intestinal relaxation – beta 2 Uterus relaxation – beta 2
  18. 18. Continued… Bronchodilation – beta 2 Calorigenesis – beta 2 Glycogenolysis – beta 2 Lipolysis – beta 1 Bladder wall relaxation – beta 2