Chapter 15: Autonomic Nervous System

1. Chapter 15: Autonomic Nervous System

2. Overview of ANS Main input to ANS comes from autonomic sensory neurons that are associated with interoceptors. Chemoreceptors that monitor pH Mechanoreceptors that monitor stretch Pain receptors produce conscious sensations Autonomic motor neurons regulate visceral activities. Limited conscious control of autonomic responses INteroceptors monitor the internal environment.INteroceptors monitor the internal environment.

3. ANS vs SNS

4. Sympathetic and Parasympathetic

5. Sympathetic and Parasympathetic

6. ANS anatomy Motor neurons Preganglionic neuron Cell body in CNS Type B myelinated axon that extends to autonomic ganglion. Postganglionic neuron Cell body in autonomic ganglion Forms synapses with preganglionic neuron Type C unmyelinated fiber that terminates on visceral effector

7. Preganglionic neurons Sympathetic division has cell bodies in the lateral horns of the gray matter in T1-12 and L1,2 and sometimes 3. Axonal output referred to as thoracolumbar outflow Parasympathetic division has cell bodies in cranial nerves III, VII, IX, and X and in the gray horns of S2-4. Axonal output referred to as craniosacral outflow.

10. Sympathetic ganglia Sympathetic trunk ganglia lie in a vertical row close to both sides of the vertebral column from the base of skull to coccyx Superior, middle and inferior cervical ganglia Postganglionic neurons innervate organs above diaphragm. Prevertebral ganglia lie anterior to vertebral column and close to abdominal arteries. Celiac, superior and inferior mesenteric ganglia Postganglionic neurons innervate organs below the diaphragm.

11. Parasympathetic ganglia Terminal ganglia are located close to area within wall of the visceral organ. Ciliary ganglion Pterygopalatine ganglion Submandibular ganglion Otic ganglion Axons are longer than those found in the sympathetic division.

12. Sympathetic postganglionic neurons Preganglionic neurons connect to postganglionic neurons in the following ways: Preganglionic neuron synapses with postganglionic neuron in first ganglion it reaches Preganglionic neuron ascends or descends to another ganglion along sympathetic chain before synapsing with postganglionic neuron. An axon may project through a ganglion and synapse with a postglanglionic neuron in one of the prevertebral ganglia. Preganglionic sympathetic fibers synapse on the adrenal medulla. Preganglionic neurons can have numerous branches.

13. Parasympathetic postganglionic neurons Axons of preganglionic neurons project to visceral effectors and synapse on 4-5 postganglionic neurons supplying a single visceral organ.

14. Autonomic plexuses Made up a tangled web of ganglia and axons found close to major arteries. Cardiac plexus—heart Pulmonary plexus—pulmonary branches Celiac plexus—celiac and mesenteric arteries, liver, gall bladder, pancreas, stomach, spleen, and kidneys Mesenteric plexus—large and small intestines Hypogastric plexus—pelvic viscera Renal plexus—kidneys and ureters

16. Structure of sympathetic division Cervical portion Superior cervical ganglion postganglionic neurons project to head and heart Middle and inferior cervical ganglia project to heart. Thoracic portion—postganglionic neurons project to thoracic viscera Lumbar portion

17. Structure of parasympathetic division Ciliary ganglion preganglionic nerves are in the oculomotor (III) nerve postganglionic neurons go to smooth muscles of the eye. Pterygopalatine Preganglionic neurons from facial (VII) nerve Postganglionic neurons project to nasal mucosa, palate, pharynx, and lacrimal glands.

18. Structure of parasympathetic division Submandibular ganglion preganglionic nerves from facial (VII) nerve postganglionic neurons go to sublingual and submandibular salivary glands Otic ganglia Preganglionic neurons from glossopharyngeal (IX) nerve Postganglionic neurons project to parotid salivary glands.

19. Cholinergic neurons and receptors Cholinergic neurons release ACh Cholinergic receptors Nicotinic receptors are present in postganglionic neurons and motor endplate Muscarinic receptors are present in membrane of all effectors (smooth muscle, cardiac muscle, and glands)

20. Cholinergic neurons and receptors

21. Cholinergic neurons and receptors

22. Cholinergic neurons and receptors

23. Adrenergic neurons and receptors Adrenergic neurons release norepinephrine (NE) Adrenergic receptors Alpha and beta receptors are on visceral effectors a1 and b1 are excitatory a1 and b2 are inhibitory b3 is on brown adipose tissue and is involved in thermogenesis

24. Adrenergic neurons and receptors

25. Physiological effects of ANS Autonomic tone—the balance between both sympathetic and parasympathetic activity. Sweat glands, arrector pili muscles, kidneys, spleen, and most blood vessels only get sympathetic input. Sympathetic response supports vigorous activity and rapid production of ATP Parasympathetic response supports functions that conserve and restore energy.

26. Sympathetic responses: Fight or flight Pupils dilate Heart rate and blood pressure increase Airways dilate Blood vessels that supply kidneys and GI tract constrict Blood vessels that supply muscles, liver and adipose tissue dilate Liver cells break down glycogen to glucose and adipose tissue breaksdown triglycerides

27. Parasympathetic responses: rest and digest SLUDD—salivation, lacrimation, urination, digestion, defecation Decreased heart rate Decreased diameter of airways Decreased diameter of the pupils

28. Autonomic reflexes Regulate controlled conditions in the body Blood pressure Digestion Defecation Urination The reflex arc organizes the response. Receptor Sensory neuron Integration center Motor neuron Effector

29. Autonomic reflexes Receptor—distal end of the sensory neuron Sensory neuron--projects to CNS Integration center—hypothalamus and brain stem and spinal cord Motor neurons project from CNS through one or two synapses Effector—effects on smooth muscle, cardiac muscle, and glands.

30. Autonomic control in CNS Hypothalamus is major control and integrator Receives sensory input Is connected to both ANS divisions Posterior and lateral parts control the sympathetic division. Anterior and medial parts control the parasympathetic division