1. Human Anatomy 5th ed. 2005 Benjamin Cummings General Anatomy of the Autonomic Nervous System

2. Human Anatomy 5th ed. 2005 Benjamin Cummings Introduction to ANS Regulates activity of smooth muscle, cardiac muscle and glands Operates without conscious control Named autonomic because was thought to be AUTONOMUS (working without CNS)

3. Human Anatomy 5th ed. 2005 Benjamin Cummings Autonomic Nervous System But to operate it depends on continuous flow of sensory input from: –Visceral organs and –Blood vessels ( not consciously perceived ) into –INTEGRATING CENTERS IN THE CNS.

4. Human Anatomy 5th ed. 2005 Benjamin Cummings Autonomic Nervous System Structurally then ANS includes: –Autonomic sensory neurons –Integrating centers in the CNS –Autonomic motor neurons to smooth muscle, cardiac muscle and glands Where in the CNS? Hypothalamus and brain stem

5. Human Anatomy 5th ed. 2005 Benjamin Cummings Comparing the ANS and Somatic NS Structurally then SNS includes: –Somatic sensory neurons –Integrating centers in the CNS (Cortex) –Somatic motor neuron to skeletal muscles only

6. Human Anatomy 5th ed. 2005 Benjamin Cummings Comparing the ANS and Somatic NS Somatic- the effect of a motor neuron is always excitation Autonomic- the effect of a motor neuron is either excitatory or inhibitory

7. Human Anatomy 5th ed. 2005 Benjamin Cummings Autonomic Nervous System Makes all routine adjustments in physiological systems. The ANS pathway from the CNS to the effector always involves 2 neurons synapsing in an autonomic ganglion

8. Human Anatomy 5th ed. 2005 Benjamin Cummings ANS –Preganglionic (neuron #1) – cell body is in the CNS, axon extends to the ganglion outside the CNS –Postganglionic (neuron #2) – cell body is in the ganglion, axon extends to the visceral effector

9. Human Anatomy 5th ed. 2005 Benjamin Cummings Nerve Fibers of the ANS Preganglionic (neuron #1) –Always myelinated –Neurotransmitter is always ACh Postganglionic (neuron #2) –Always nonmyelinated –Neurotransmitter is Ach or norepinephrine

10. Human Anatomy 5th ed. 2005 Benjamin Cummings

11. Human Anatomy 5th ed. 2005 Benjamin Cummings Subdivisions of the ANS Sympathetic Division –Fight-or-flight Parasympathetic Division –Rest-and-digest These divisions are anatomically distinct

12. Human Anatomy 5th ed. 2005 Benjamin Cummings Sympathetic Sympathetic division (thoracolumbar) –Cell bodies for all the neurons #1 reside in the thoracic and lumbar portions of the spinal cord. T 1 – L 2

13. Human Anatomy 5th ed. 2005 Benjamin Cummings Sympathetic –Stimulates heart beat tissue metabolism, increases alertness, prepares the body to deal with emergencies (“fight or flight” division)

14. Human Anatomy 5th ed. 2005 Benjamin Cummings T 1 -L 2

15. Human Anatomy 5th ed. 2005 Benjamin Cummings Parasympathetic Parasympathetic division (craniosacral) –Cell bodies reside in the brain stem (cranial nerves) or in the sacral portion of the spinal cord.

16. Human Anatomy 5th ed. 2005 Benjamin Cummings Cranial & Sacral

17. Human Anatomy 5th ed. 2005 Benjamin Cummings Parasympathetic –Slows the heart rate, –inhibits senses, –prepares the body for rest and relaxation; (“rest and digest” division).

18. Human Anatomy 5th ed. 2005 Benjamin Cummings The Sympathetic Division

19. Human Anatomy 5th ed. 2005 Benjamin Cummings Sympathetic Chain Ganglia –Synapses of neurons #1 and #2 are in a chain of ganglia that run alongside the spinal cord –Extends on both sides of the vertebral column –Carries preganglionic fibers and cell bodies of postganglionic neurons

20. Human Anatomy 5th ed. 2005 Benjamin Cummings Ganglia

21. Human Anatomy 5th ed. 2005 Benjamin Cummings Anatomy of the chain Rami communicantes from the spinal nerves connect to the chain

22. Human Anatomy 5th ed. 2005 Benjamin Cummings

23. Human Anatomy 5th ed. 2005 Benjamin Cummings A closer look at spinal nerves

24. Human Anatomy 5th ed. 2005 Benjamin Cummings Routes of Preganglionic Axons Cell bodies of neurons #1 lie in the lateral gray horns of the spinal cord The axons of neurons #1 leave the spinal cord via the ventral root These axons pass to the spinal nerve Axons leave the spinal nerve via the white branches (rami communicantes) Connect with the sympathetic chain ganglia

25. Human Anatomy 5th ed. 2005 Benjamin Cummings Routes of Preganglionic Axons There are 3 possible routes that sympathetic neurons may follow Possibility #1: synapses within the ganglion at that level and –Second neuron leaves at that level via the gray ramus communicans, exits to the visceral effector

26. Human Anatomy 5th ed. 2005 Benjamin Cummings

27. Human Anatomy 5th ed. 2005 Benjamin Cummings Routes of Preganglionic Axons Possibility #2: neuron #1 goes up or down the chain and synapses at some other level. –Second neuron: leaves at that other level via the gray ramus communicantes, and exits to the visceral effector.

28. Human Anatomy 5th ed. 2005 Benjamin Cummings

29. Human Anatomy 5th ed. 2005 Benjamin Cummings Routes of Preganglionic Axons Possibility #3: neuron #1 does not synapse in the chain (exception!!) but exits and synapses in a collateral ganglion near a major blood vessel. –Neuron #2 travels from that ganglion to the visceral effector.

30. Human Anatomy 5th ed. 2005 Benjamin Cummings

31. Human Anatomy 5th ed. 2005 Benjamin Cummings Where are the Collateral Ganglia ? Location –Near a major blood vessel –Celiac ganglion Innervates upper abdominal viscera –Superior mesenteric Innervates middle abdominal viscera –Inferior mesenteric Innervates lower abdominal & pelvic organs

32. Human Anatomy 5th ed. 2005 Benjamin Cummings The Adrenal Medulla Yet another type of innervation: –Going to the adrenal medulla –No synapse in ganglia –No synapse in collateral ganglia –YES synapse in the adrenal medulla

33. Human Anatomy 5th ed. 2005 Benjamin Cummings

34. Human Anatomy 5th ed. 2005 Benjamin Cummings Adrenal Medulla Only preganglionic neurons are in this pathway Neuron #1 stimulates the medulla, The medulla releases norepinephrine and epinephrine (adrenaline) to blood

35. Human Anatomy 5th ed. 2005 Benjamin Cummings Adrenal Medulla

36. Human Anatomy 5th ed. 2005 Benjamin Cummings Effects of Sympathetic Stimulation Widespread –The sympathetic chain allows one preganglionic fiber to synapse with many postganglionic neurons Enhanced & prolonged by the adrenal medulla

37. Human Anatomy 5th ed. 2005 Benjamin Cummings Convergence See heart

38. Human Anatomy 5th ed. 2005 Benjamin Cummings Neurotransmitters of Sympathetic Division Preganglionic fibers release acetylcholine (Ach) Therefore they are called: –Cholinergic Postganglionic fibers (most) release norepinephrine (NE) (=noradrenaline) –Adrenergic Adrenal medulla releases norepinephrine and epinephrine (adrenalin)

39. Human Anatomy 5th ed. 2005 Benjamin Cummings

40. Human Anatomy 5th ed. 2005 Benjamin Cummings Functions of the Sympathetic Division Heart: increases rate Lung bronchioles: dilates bronchioles Salivary glands: produce viscous fluid Stomach: decreases motility Pupil: dilates Sweat glands: produce secretions

41. Human Anatomy 5th ed. 2005 Benjamin Cummings Summary of Sympathetic Division Cell bodies are found in the thoracic and lumbar portions of the spinal cord Preganglionic fibers are short, connect to the sympathetic chain, and synapse with long postganglionic fibers Preganglionic fibers produce ACh, postganglionic fibers produce NE or Ach “Fight or flight” division

42. Human Anatomy 5th ed. 2005 Benjamin Cummings

43. Human Anatomy 5th ed. 2005 Benjamin Cummings The Parasympathetic Division

44. Human Anatomy 5th ed. 2005 Benjamin Cummings Parasympathetic division Cell bodies are in the brain or in the gray matter of the spinal cord (sacral region) Neurons #1 exit the cranial region through cranial nerves 3, 7, 9, & 10 or Neurons #1 exit the spinal cord through the sacral spinal nerves

45. Human Anatomy 5th ed. 2005 Benjamin Cummings Parasympathetic

46. Human Anatomy 5th ed. 2005 Benjamin Cummings Parasympathetic Neurons #1 are long and synapse with neurons #2 (short) in ganglia Ganglia are found on, or –near the visceral effector

47. Human Anatomy 5th ed. 2005 Benjamin Cummings Parasympathetic

48. Human Anatomy 5th ed. 2005 Benjamin Cummings Parasympathetic ganglia

49. Human Anatomy 5th ed. 2005 Benjamin Cummings Neurotransmitter of Parasympathetic Division Preganglionic fibers: Acetylcholine Postganglionic fibers: Acetylcholine

50. Human Anatomy 5th ed. 2005 Benjamin Cummings

51. Human Anatomy 5th ed. 2005 Benjamin Cummings General Functions of the Parasympathetic Prepares the individual for rest and repose “Rest & digest” division

52. Human Anatomy 5th ed. 2005 Benjamin Cummings Effects on various organs: Heart: decreases rate Lung bronchioles: constricts bronchioles Salivary glands: produces watery fluid fluid Stomach: increases motility Pupil: constricts Sweat glands: reduces secretions

53. Human Anatomy 5th ed. 2005 Benjamin Cummings Summary of the Parasympathetic Division Cell bodies are found in the brain and in the sacral region of the spinal cord Preganglionic fibers are long and synapse with short postganglionic fibers on or near the target viscera Both preganglionic and postganglionic fibers produce Ach “Rest & digest” division

54. Human Anatomy 5th ed. 2005 Benjamin Cummings Relationship Between the Sympathetic and Parasympathetic Divisions Most organs receive dual innervation It is a tug of war between the two

55. Human Anatomy 5th ed. 2005 Benjamin Cummings ANS either increases excitation or inhibits the activity –Ex. Sympathetic fibers increase heart rate, parasympathetic fibers decrease heart rate. –Homeostasis comes from the balance of the two.

56. Human Anatomy 5th ed. 2005 Benjamin Cummings ANS either increases excitation or inhibits the activity Ex.#2 Sympathetic fibers decreases stomach motility. Parasympathetic fibers increase stomach motitlity

57. Human Anatomy 5th ed. 2005 Benjamin Cummings Parasympathetic innervation The cranial nerve fibers involved are motor - control smooth muscle & glands in the upper body –Cranial nerve #3 – lens & pupil –Cranial nerve #7 – lacrimal glands, submandibular & submaxillary glands (salivary) –Cranial nerve #9 – parotid gland (salivary) –Cranial nerve #10 - viscera of thorax & abdomen Sacral nerves innervate the kidneys, colon, & sex organs