CBIO 2200 1nd Edition Lecture 21 Outline of Last Lecture I Dermatomes and Cutaneous Innervation II Diseases III Reflexes IV Spinal Cord Trauma Outline of Current Lecture I Visceral Reflexes II Functional Organization III The Enteric Nervous System IV Neurotransmitters and Their Receptors Current Lecture Chapter 15 The Autonomic Nervous System and Visceral Reflexes I Visceral Reflexes a The ANS is responsible for the body s visceral reflexes e g heart rate blood pressure body temp b Visceral reflex arc i Receptors ii Afferent neurons iii Interneurons iv Efferent neurons v Effectors c Baro reflex i High blood pressure detected by arterial stretch receptors baroreceptors 1 Receptors are right at the aorta where blood is pumped from the heart 2 Sent to CNS to interpret These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute II a Too high slow down heart rate vasodilation b Too low raise heart rate vasoconstriction ii Example of homeostatic negative feedback loop d Autonomic Motor Pathways vs Somatic Motor Pathways i ANS two neurons from CNS to effectors 1 Myelinated preganglionic fiber will synapse onto ganglion which gives rise to a un myelinated postganglionic fiber Functional Organization a Somatic voluntary autonomic involuntary b Sympathetic division i Prepares for physical activity ii Fight or flight division stressful situations iii The thoracolumbar division name comes from where the nerves arrive from thoracic and lumbar regions of the spinal cord iv Short preganglionic and long postganglionic fibers gives rise to the sympathetic ganglion chain v Preganglionic neurosomas 1 Lead to nearby sympathetic chain of ganglia aka paravertebral ganglia vi White communicating ramus myelinated 1 Splanchnic nerves innervate internal organs vii Gray communicating ramus unmyelinated viii Neural divergence not 1 to 1 relationship of post and preganglionic fibers 1 One preganglionic fiber may synapse with multiple postganglionic fibers 2 Allows wide spread affects of info coming from spinal cord ix The adrenal gland 1 Each is two glands with different functions a Adrenal cortex outer layer secretes steroid hormaones b Adrenal medulla inner core essentially a sympathetic ganglion c Parasympathetic division i Calms many body functions ii Rest and digest division iii Craniosacral division named for where nerves arise 1 Brain nerves arise from midbrain pons and medulla 2 Sacrum S2 S4 iv Long preganglionic and short postganglionic fibers v Oculomotor nerve III vi Facial nerve VII vii Glossopharyngeal nerve IX viii Vagus nerve X III IV ix Remaining parasympathetic fibers arise from levels S2 to S4 of the spinal cord x Very little neural divergence The Enteric Nervous System a The nervous system of the digestive tract b Composed of 100 million neurons found in the walls of the digestive tract c Regulates esophagus stomach and intestinal motility and secretion of digestive enzymes and acid d Parasympathetic and sympathetic nervous systems can modulate its activity e Megacolon massive dilation of the bowel i Usually evident in newborns who fail to have their first bowel movement ii Hirschsprung s disease missing enteric nervous system also called aganglionic mega colon Neurotransmitters and their Receptors a How can different autonomic neurons have different effects b Two fundamental reasons i Different receptors ii c Cholinergic fibers i All preganglionic fibers in parasympathetic and sympathetic divisions secrete acetylcholine ii All postganglionic fibers in parasympathetic division secret acetylcholine and some in the sympathetic division others secrete norepinephrine d Cholinergic receptor acetylcholine receptors i Two types that receive acetylcholine 1 Nicotinic receptor Ach is excitatory to nicotinic receptors 2 Muscarinic receptors Ach can be excitatory or inhibitory to muscarinic receptors e NE is secreted by many sympathetic postganglionic neurons i Adrenergic fibers ii Adrenergic receptors 1 Alpha adrenergic receptors usually excitatory 2 Beta adrenergic receptors usually inhibitory f Dual innervation i Antagonistic effects example in iris ii Cooperative effects 1 Parasympathetic increase salivary serous cell secretion 2 Sympathetic increase salivary mucous cell secretion iii Both divisions do not normally innervate an organ equally iv Control without dual innervation 1 Effectors receive only sympathetic fibers a Examples adrenal medulla arrector pili muscles sweat glands and many blood vessels b Sympathetic vasomotor tone baseline frequency of sympathetic firing 2 Reduction in firing frequency