CBIO 2200 1nd Edition Lecture 21 Outline of Last Lecture I. Dermatomes and Cutaneous InnervationII. DiseasesIII. ReflexesIV. Spinal Cord TraumaOutline of Current Lecture I. Visceral ReflexesII. Functional OrganizationIII. The Enteric Nervous SystemIV. Neurotransmitters and Their ReceptorsCurrent LectureChapter 15 – The Autonomic Nervous System and Visceral ReflexesI. Visceral Reflexesa. The ANS is responsible for the body’s visceral reflexes (e.g. heart rate, blood pressure, body temp.)b. Visceral reflex arci. Receptorsii. Afferent neuronsiii. Interneuronsiv. Efferent neuronsv. Effectorsc. Baro-reflexi. High blood pressure detected by arterial stretch receptors (baroreceptors)1. Receptors are right at the aorta where blood is pumped from the heart2. Sent to CNS to interpretThese 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.a. Too high – slow down heart rate & vasodilationb. Too low – raise heart rate & vasoconstrictionii. Example of homeostatic negative feedback loopd. Autonomic Motor Pathways vs. Somatic Motor Pathwaysi. ANS – two neurons from CNS to effectors1. Myelinated preganglionic fiber will synapse onto ganglion, which gives rise to a un-myelinated postganglionic fiberII. Functional Organizationa. Somatic = voluntary; autonomic = involuntaryb. Sympathetic divisioni. Prepares for physical activityii. “Fight or flight” division; stressful situationsiii. 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 chainv. Preganglionic neurosomas1. Lead to nearby sympathetic chain of ganglia (aka paravertebral ganglia)vi. White communicating ramus – myelinated 1. Splanchnic nerves – innervate internal organsvii. Gray communicating ramus – unmyelinated viii. Neural divergence – not 1 to 1 relationship of post and preganglionic fibers1. One preganglionic fiber may synapse with multiple postganglionic fibers2. Allows wide spread affects of info coming from spinal cordix. The adrenal gland1. Each is two glands with different functionsa. Adrenal cortex (outer layer) – secretes steroid hormaonesb. Adrenal medulla (inner core) – essentially a sympathetic ganglionc. Parasympathetic divisioni. Calms many body functionsii. “Rest and digest” divisioniii. Craniosacral division – named for where nerves arise1. Brain – nerves arise from midbrain, pons, and medulla2. Sacrum S2-S4iv. Long preganglionic and short postganglionic fibersv. Oculomotor nerve (III)vi. Facial nerve (VII)vii. Glossopharyngeal nerve (IX)viii. Vagus nerve (X)ix. Remaining parasympathetic fibers arise from levels S2 to S4 of the spinal cordx. Very little neural divergenceIII. The Enteric Nervous Systema. The nervous system of the digestive tractb. Composed of 100 million neurons found in the walls of the digestive tractc. Regulates esophagus, stomach, and intestinal motility and secretion of digestive enzymes and acidd. Parasympathetic and sympathetic nervous systems can modulate its activitye. Megacolon: massive dilation of the boweli. Usually evident in newborns who fail to have their first bowel movementii. Hirschsprung’s disease – missing enteric nervous system (also called aganglionic mega-colon)IV. Neurotransmitters and their Receptorsa. How can different autonomic neurons have different effects?b. Two fundamental reasonsi. Different receptorsii.c. Cholinergic fibersi. All preganglionic fibers in parasympathetic and sympathetic divisions secrete acetylcholineii. 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 receptors2. Muscarinic receptors – Ach can be excitatory or inhibitory to muscarinic receptorse. NE is secreted by many sympathetic postganglionic neuronsi. Adrenergic fibersii. Adrenergic receptors1. Alpha-adrenergic receptors – usually excitatory2. Beta-adrenergic receptors – usually inhibitory f. Dual innervationi. Antagonistic effects – example in irisii. Cooperative effects1. Parasympathetic increase salivary serous cell secretion2. Sympathetic increase salivary mucous cell secretioniii. Both divisions do not normally innervate an organ equallyiv. Control without dual innervation1. Effectors receive only sympathetic fibersa. Examples: adrenal medulla, arrector pili muscles, sweat glands, and many blood vesselsb. Sympathetic vasomotor tone -= baseline frequency of sympathetic firing2. Reduction in firing