Summers

Neurobiology acronyms

text: Fundamental Neuroscience - Zigmond, et al.,: Read pages 1027-1049 for this lecture end

XXVIII. Autonomic Function  			back to XXVII. Nitric Oxide


	A. Visceral and involuntary motor system


		1. controlling smooth muscle, heart muscle, exocrine glands, &
		   endocrine glands


	B. Autonomic motor neurons are located peripherally within ganglia
	   outside the CNS


		1. somatic motor neurons (by contrast) are within
		   CNS and monosynaptic


		2. these autonomic motor neurons are called postganglionic or
		    postsynaptic neurons


			a. innervated by preganglionic or presynaptic neurons


				i. presynaptic somata are in the brainstem or spinal cord


					(1) \ the autonomic NS is disynaptic


	C. Three Autonomic divisions: Sympathetic, Parasympathetic, Enteric


		1. Sympathetic (thoracolumbar) NS				     


			a. governs fight or flight response


			b. presynaptic cell bodies are in the intermediolateral gray of the
			   spinal cord from the 1st thoracic to lower lumbar segments


			c. exit spinal cord via ventral root (at the segmental level which the
			   cell bodies are located) and project to paravertebral chain ganglia


				i. may innervate rostral or caudal postsynaptic cells by travelling
				   within the ganglionic connective (or trunk)


					(1) each presynaptic cell synapses with many postsynaptic
					    cells (ratio = 1:10)


						(a) sympathetic action is coordinated, relatively systemic


				ii. preganglionic cells secrete ACh


			d. secretes NE at peripheral nerve terminals (i.e. postsynaptic terminals)


			e. dilates pupils (via superior cervical ganlion to head and neck)


			f. ­ HR, heart metabolism and contractility
			  (via middle cervical ganglion to heart and lungs)


				i. also ­ respiratory rate


				ii. via stellate ganglion dilates bronchi


			g. sympathetic chain ganlia to body wall: ­ vascular constriction
			   and blood pressure


				i.  ­ muscular blood flow


			h. Adrenal gland (medullary chromaffin tissue) is like the postsynaptic
			   cell, but is endocrine


				i. monosynaptic: secretes ACh


				ii. secretes 2/3 Epi, 1/3 NE into vasculature   (humans)


				iii. in this way the autonomic NS is truely systemic


			i. celiac, superior & inferior mesenteric ganglia: ¯ digestive function
											     

				i.  ¯ blood flow, motility, secretion of digestive fluids


		2. Parasympathetic (craniosacral) NS


			a. rest and digest


			b. presynaptic cell bodies are in the brainstem or
			   sacral (S2-24) spinal cord


				i. very long axons


				ii. cranial nerves (I-XII) eminate from the brainstem


				iii. presynaptic terminals secrete ACh


			c. postsynaptic ganglia are close to cell targets or embedded in them


				i. postganglionic terminals also secrete ACh


			d. ciliary ganglion cell axons innervate pupillary constrictor
			   and ciliary muscles 


				i.  ciliary ganglion innervated by cranial nerve III (oculomotor)


			e. lacrimal and salivary glands connected via
			   pterygopalatine (VII, facial), submandibular (VII), and
			   otic (IX, glossopharyngeal) ganglia


	`			i. increase secretion


			f. heart, lungs, bronchi, GI tract, liver, and kidneys all have
			   the 1st synapse and ganglion embedded within the organ


				i. all innervated by the vagal (X) nerve


					(1) X comes from the dorsal vagal nucleus and the nucleus
					    ambiguus in the medulla and pons


				ii. slows HR, constricts bronchi, dilates skin capillaries


				iii. increases motility and exocrine secretions of digestive tract


			g. bladder, decending colon, uterus, & genetalia innervated via
			   the sacral spinal cord


		3. Enteric


			a. 3 types of neurons


				i. sensory


					(1) information from the digestive tract and associated organs


					(2) excited by stretching and contractions  of intestinal wall


				ii. motor: innervate circular and longitudinal smooth muscle


				iii.  interneurons: 5-HT, peptides


			b. regulated by parasympathetic and sympathetic systems


				i. can function without central inputs


	D. Regulation of Autonomic output					


		1. Hypothalamus (especially PVN and lateral hypothal.) integrates influences
		   from cortex, hippocampus, amygdala, thalamus, basal ganglia, and cerebellum


			a. PVN neurons project  (via MFB) to autonomic nuclei in the brainstem


				i. AVP and Oxy


				ii. solitary tract ® vagal, reticular nuclei


				iii. project directly to reticular and raphe nuclei


					(1) produce 5-HT


			b. also influences autonomic function via endocrine control


			c. continuous monitoring by hypothalamus unnecessary


		2. Nucleus of the Solitary Tract controls simple autonomic function by
		   reflex circuits and relays information to higher brain and brainstem
																		
																		
			a.  reciprocal innervation to limbic structures


				i. central amygdala


			b. input from lateral tegmental area ® NST, vagal nucleus &
			   spinal sympathetic preganglionic neurons


				i. NE ®  ¯ preganglionic  neurons ® ¯ ACh ® ¯ postganglionic
                                 neurons ® ¯ NE peripherally


			c. input from raphe and reticular nuclei


				ii. 5-HT ® ­ preganglionic neurons ® ­ ACh ® ­ post ® ­ NE


			d. central NE ­ while 5-HT ¯  parasympathetic activity


		3. Autonomic events are coordinated with behavior via limbic structures


			a. hippocampus, central amygdala, septal nuclei project to 


				i. lateral hypothalamus, periaqueductal grey which project to


					(1) reticular formation


					(2) reticulospinal tract


				ii. spinal neurons ® skeletal muscle (for behavior)


	D. Integration of central control and output is a balance


		1. balance of 5-HT and NE centrally


		2. balance of ACh and NE peripherally


		3. never all or none


			a. rebound effect


				i. fainting

XIX. Perception and Movement

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