BIOL 2457 1st Edition Lecture 33Outline of Last Lecture The Autonomic Nervous System Outline of Current LectureThe Autonomic Nervous System  Parasympathetic division Preganglionic neurons in the brainstem and sacral segments of spinal cord (cranialsacrial) Ganglionic neurons in peripheral ganglia located within or near target organs (short postganglionic fibers) Parasympathetic Organization Preganglionic fibers leave the brain as cranial nerves III, VI, IX, X Sacral neurons form the pelvic nerves S2-S4 Parasympathetic activation Effects produced by the parasympathetic division  relaxation food processing energy absorption Parasympathetic Division Craniosacral division Preganglionic neurons originate from the cranial nerves III, VII, IX and X and sacral spinal nerves S2-S4 Parasympathetic ganglia Terminal ganglia Presynaptic neuron usually synapses with 4-5 postsynaptic neurons all of which supply a single visceral effector Neurotransmitters & parasympathetic functions All parasympathetic fibers release ACh Short-lived response as ACH is broken down by AChE and tissue cholinesterase Postsynaptic membranes have two kinds of receptors Muscarinic Nicotinic Autonomic Plexuses A network of sympathetic and parasympathetic axons Cardiac plexus - heart Pulmonary plexus - the bronchial tree Celiac plexus Largest  Supplies the stomach, spleen, pancreas, liver, gallbladder, and adrenal medullae Superior mesenteric plexus- small intestine and proximal colon Inferior mesenteric plexus- distal colon and rectum Hypogastric plexus- urinary bladder and genital organs Renal plexus- kidneys and ureters Cranial Parasympathetic Outflow The cranial outflow has four pairs of ganglia and are associated with the vagus nerve Ciliary ganglia Pterygopalatine ganglia Submandibular ganglia Otic ganglia Vagus nerve carries nearly 80% of the total craniosacral flow Sacral Parasympathetic Outflow Consists of S2-S4 Pelvic splanchnic nerves Cholinergic Neurons Cholinergic neurons → acetylcholine (ACh) Cholinergic neurons include All sympathetic and parasympathetic preganglionic neurons Sympathetic postganglionic neurons that innervate most sweat glands All parasympathetic postganglionic neurons Cholinergic receptors release acetylcholine Types of receptors Nicotinic receptors Muscarinic receptors Adrenergic Neurons & Receptors Release norepinephrine (noradrenalin) Most sympathetic postganglionic neurons are adrenergic Types of receptors Alpha receptors Beta receptors Physiology of the ANS Autonomic tone- a balance between the sympathetic and parasympathetic activity Regulated by the hypothalamus Sympathetic Responses Stress ↑ sympathetic system ↑ fight-or-flight response ↑ production of ATP Dilation of the pupils ↑ heart rate and blood pressure Dilation of the airways Constriction of blood vessels that supply the kidneys & gastrointestinal tract ↑ blood supply to the skeletal muscles, cardiac muscle, liver and adipose tissue ↑ glycogenolysis ↑ blood glucose ↑ lipolysis  Parasympathetic Responses Rest-and-digest response Conserve and restore body energy ↑ digestive and urinary function ↓ body functions that support physical activity Integration and Control of Autonomic Functions Direct innervation- brain stem and spinal cord Hypothalamus is the major control and integration center of the ANS It receives input from the limbic system Visceral reflexes Visceral reflex arcs are the simplest function of the ANS Long reflexes (interneurons) Short reflexes (bypassing CNS) Parasympathetic reflexes govern respiration, cardiovascular function and other visceral activities Higher levels of autonomic control Activity in the ANS is controlled by centers in the brainstem that deal with visceral functioning Higher order functions Are performed by the cerebral cortex and involve complex interactions  Involve conscious and unconscious information processing Are subject to modification and adjustment over time Memory Short term or long term Memory consolidation is moving from short term to long term Primary - | Secondary & Tertiary  Amnesia is the loss of memory due to disease or trauma Consciousness Deep sleep, the body relaxes and cerebral cortex activity is low REM sleep active dreaming occurs The reticular activating system (RAS) is important to arousal and maintenance of consciousness Neurotransmitters & the brain Neurotransmitters and brain functionChanges in balance between neurotransmitters can profoundly alter brain function Personality and self-awarenessCharacteristics of the brain as an integrated system rather than one specific