Parasympathetic Nervous System & Central Integration Lecture PDF

lecture 2, 10/09/23 Fernando Gómez-Pinilla, Ph.D. Professor, Dept. Neurosurgery, Med. School Dept. Integrative Biology and Physiology. UCLA c144/244 -- F. Gomez-Pinilla - UCLA Autonomic Nervous System Parasympathetic Nervous System (PNS) • Energy conservation (“rest and digest”). • Anabolic pro...

lecture 2, 10/09/23 Fernando Gómez-Pinilla, Ph.D. Professor, Dept. Neurosurgery, Med. School Dept. Integrative Biology and Physiology. UCLA c144/244 -- F. Gomez-Pinilla - UCLA Autonomic Nervous System Parasympathetic Nervous System (PNS) • Energy conservation (“rest and digest”). • Anabolic processing. • Promotes GI processes required to digest and absorb nutrients. • Storage and efficient use of energy. • Craniosacral or bulbosacral c144/244 -- F. Gomez-Pinilla - UCLA PNS involves a two-neuron circuit • Preganglionic neuron in brainstem and sacral segments of spinal cord (S2-S4) • Postganglionic: close to target tissue c144/244 -- F. Gomez-Pinilla - UCLA Innervation of head and neck region • Preganglionic neurons in brain stem send axons to periphery via cranial nerves (III, VII, IX, X): • Edinger-Westphal Nucleus - III nerve - ciliary ganglion-sphincter pupillae, ciliary muscle • Sup. Salivatory nucleus - VII nerve - pterygopalatine ganglion and submandibular ganglion -- palate, nasal cavity • Inf. Salivatory nucleus: IX nerve - otic ganglion -parotid gland -- floor of mouth c144/244 -- F. Gomez-Pinilla - UCLA c144/244 -- F. Gomez-Pinilla - UCLA Innervation of thorax and abdomen via vagus nerve (X) • Cell bodies of nerve X in brain stem nuclei: • Dorsal motor nucleus – innervate smooth muscle and glands of the entire GI tract (pharynx to colon) • Nucleus Ambiguus: innervate striated muscle of pharynx, larynx, and esophagus, and cardiac muscle c144/244 -- F. Gomez-Pinilla - UCLA Innervation of abdomen and pelvis follows same pattern as SNS with cell bodies in Sacral spinal cord • Preganglionic neuron in Intermediolateral cell column of sacral spinal cord (S2-S4) -- similar to SNS. • Postganglionic neurons located in plexuses nearby or within the target organ. • control of vasomotor, and secremotor function of kidneys, bladder, transverse/distal colon, and sexual organs. c144/244 -- F. Gomez-Pinilla - UCLA PNS neurons in sacral spinal cord are in the IML (similar to SNS) c144/244 -- F. Gomez-Pinilla - UCLA How SNS and PNS produce antagonistic actions in the same tissue/organ? • Different neurotransmitter systems enables opposite actions on same organ • (exception: white/brown adipose tissue, peripheral blood vessels, and sweat glands are innervated only by SNS). • Receptor specialization (adrenergic and cholinergic receptor subtypes). • Other neuropeptides can be released by postganglionic cells, e.g., somatostatin, NPY are associated with the SNS. • Firing pattern can change the proportion of transmitter/cotransmitter released by single fiber • Large variety of neurotransmitters and modulators in the ENS c144/244 -- F. Gomez-Pinilla - UCLA two transmitter systems in ANS (acetylcholine and norepinephrine): • Preganglionic neurons in SNS and PNS use acetylcholine (ACH). • Postganglionic cells in PNS also use ACH (Nicotine considered as a general ganglionic blocker). • Postganglionic sympathetic neurons release norepinephrine Different neurotransmitter system in postganglionic neurons enables opposite actions • Sympathetic neurons release norepinephrine • Parasympathetic neurons release ACH • The action of two different neurotransmitter system enables opposite actions on same target organ. c144/244 -- F. Gomez-Pinilla - UCLA ANS neurotransmission is used as a powerful pharmacological target to control organ function Preganglionic neurons in SNS and PNS secrete acetylcholine, and their target neurons in ganglia of both have Nicotinic Cholinergic receptors. Postganglionic neurons: SNS neurons secrete norepinephrine and their target tissue has Adrenergic receptors (Catecholaminergic receptors; exceptions: sweat glands and adrenal medulla) PNS neurons secrete acetylcholine and their target tissue has Muscarinic cholinergic receptors. Note that these are G-protein coupled receptors (GPCRs). ANS neurotransmission useful pharmacological target: Some toxins are deadly because they interfere with GPCR signals and thus disable the ANS. Two examples are cholera toxin and pertussis toxin which are secreted by bacteria. These toxins are often used in research to examine signal transduction. Most snake venom attack the ANS: Institute of Butantan in Brazil specialized in studying snake and spider venom Sensory Information from the periphery reaches the CNS via afferent axons (make sure to know the difference between afferent Vs efferent) c144/244 -- F. Gomez-Pinilla - UCLA Visceral afferents from SNS have cell bodies in DRG (from periphery going to brain) • Cell body located in dorsal root ganglion (DRG) • Enter spinal cord (SC) via Lissauer’s tract ending in dorsal horn laminae I and V. • SC laminae I and V relay sensory information to spinal centers (IML), or suprasegmental centers • rely on Nucleus solitary tract (NST) and projects to midbrain central gray, hypothalamus, amygdala, nucleus of stria terminalis F. Gomez-Pinilla, C144/244 PNS afferents from pelvic/sacral regions use SNS-like pattern • Information from viscera travels in mixed peripheral (somatic) nerves -- generally same nerve carrying afferent/efferents • Nucleus solitary tract (NST) and spinal lamina V project to midbrain central • gray, hypothalamus, amygdala, • nucleus of stria terminalis c144/244 -- F. Gomez-Pinilla - UCLA PNS Afferents from head/neck • Cell body of afferents located in ganglia outside the cranium • Central terminals end in a cranial nerve sensory nuclei • Afferents enter the brain stem through the cranial nerve V (trigeminal), and afferents related to VII, IX, X nerves terminate in the nucleus of the solitary tract (NST) in brain stem • Most visceral afferents use substance P and other tachynins as neurotransmitters, while CCK is main central neurotransmitter for vagal afferents c144/244 -- F. Gomez-Pinilla - UCLA Afferents of VII, XI, and X nerve end in NST c144/244 -- F. Gomez-Pinilla - UCLA c144/244 -- F. Gomez-Pinilla - UCLA c144/244 -- F. Gomez-Pinilla - UCLA ANS Integration is accomplished by many reflexes involving multiple organs and tissues. • Largely based on reflexes involving visceral afferent information and efferent response. • Some reflexes are local without involving the CNS. • Other reflexes are modulated by central connections from brainstem and higher centers c144/244 -- F. Gomez-Pinilla - UCLA Hypothalamic integration of autonomic reflexes • Autonomic reflexes: coordinates mouth, stomach, intestines, pancreas after a meal • Links autonomic with somatic activity -- e.g., cardiovascular and postural adjustment • Autonomic adjustment in response to environmental events F. Gomez-Pinilla, C144/244 Example of Autonomic Reflex: Cardiovascular adjustment (baroreceptor reflex) • • • • 1. Increase in SNS activity 2. Increase heart rate (tachychardia) and vasoconstriction. 3. Vagal baroreceptors detect increase in blood pressure. 4. Increase in vagal PNS activity leading to bradycardia c144/244 -- F. Gomez-Pinilla - UCLA Axon Reflex only involving the afferent neuron typical local response to visceral pain • Occurs in target tissue, action potential is propagated centrally but CNS is not involved • Low intensity stimuli that may not reach the CNS -only involving the afferent neuron • System may respond by a local release of tachykinins producing an inflammatory response: “Wheal and flare” c144/244 -- F. Gomez-Pinilla - UCLA Enteric Nervous system • • • • “Little brain of gut” Two major organized plexuses in GI tract: Myenteric plexus Submucosal or submucous plexus c144/244 -- F. Gomez-Pinilla - UCLA c144/244 -- F. Gomez-Pinilla - UCLA Kulkarni et al, J Neurosci, 2018