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USC BISC 307L - Autonomic Nervous System I
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Sound LocalizationNetwork of neurons that receive inputs from the left and right ears- Coincidence detectors from both sidesOne input alone is not sufficient to generate an action potential but 2 simultaneous EPSPs can sum and produce an action potentialIf sound comes from in front of youThe peak will hit right in the middle – C on diagramInput from right earhas more time to get to point A before left input gets there so that’s where you will hear itSound coming from left earWill travel and hit point E as Right ear input is hitting that point and thus that is where you process the soundBinaural- Simultaneous excitation at the same time from both ears causes action potentialHow good is this?Humans can detect a 1-2 degree movement of the sound source half the time- corresponds to a very short difference in arrival time of about 1/45 of a microsecondSelf correcting for sloppinessSound Localization in Medical Superior OliveA model of a circuit in the medial superior olive of a catFound:Not only an array of place and coding neurons that looks like the diagram in the previous slide but there’s thousands of these diagramsThese different arrays map out the frequencies of the sounds (sensitive to different frequencies)Autonomic Nervous System 1Slide 1- General Properties of ANSProvides critical homeostatic mechanisms- More than any other systemWe will focus on efferent functions of ANS (as opposed to afferent)Efferent= carrying away from CNSMotor commandssecretionAfferent = carrying towards CNSSensoryReflexes mediated by local circuits in spinal cord and brainstemBoth sensory and effector“Local”- do not really involve brain (involves brain stem instead)An effector (efferent) and sensory (somatosensory and visceral afferents) systemSensory part:1. Somatosensory (touch)2. Visceral (organs)2 (or 3) divisions of Efferent:1. Sympatheticfight or flight2. Parasympatheticrest and digest3. (Enteric)Biggest part! Although not stressed as much for some reasonNerves (sensory and effector) in the walls of the digestive tractResponses to/ Recovery from Emergencies- Balance between the two responses1. Fight or flight response (Sympathetic)increase respiratory rateincrease heart ratevasodilation in limb muscles –also brainvasoconstriction in viscera-intestines, skindilation of lung airwaysdecrease secretion in mouth and gutincrease general alertnessopen iris to let in more lightfright2. Rest and digest (Parasympathetic)decrease respiration to resting leveldecrease heart rate to resting levelvasoconstriction in limb musclesvasodilation in visceraconstriction of lung airwayssecretion returns to normalalertness returns to normalCNS Centers regulating the ANSBrain- Some of the centers which are mostly in the brain stem which are important to autonomic control systemHypothalamusSmall but packed with small nuclei that are not well definedUltimate control of eating, water balance, thirst, control temperature, “appetitive behaviors”, sex, salt,Small number of neurons for such important thingsDamage in behavior with damage to hypothalamusPonsMedullaPre and postganglionic neuronsHow the ANS worksActivity originates in the brain stem as a result of sensory information coming inCommands go to preganglionic (collection of cell bodies outside of the CNS) neurons at brain stem or spinal cord--> send axons out to synapse onto the second neuron Synapse between the preganglion and the post ganglion which makes a synapse onto target tissuesynapses of the postganglion are different because no well defined terminal (look at diagram on slide)along the tissue are swellings which look like synaptic terminals but they are in the middle of the axon and do not get close too the postsynaptic cells (large distances of release) but releases a lot of transmitter even though not close (almost like paracrine signaling)Timing of action between sympathetic and parasympathetic synapses is slowPostganglionic Sympathetic synapsesKnow this: Synthetic pathwayTyrosineDPAdopaminenorepinephrinesepinephrineThe last 4 are catecholamines (structure)Last two are in the brain or PNSDepends on the enzyme it has for which one is releasedPostganglionic sympathetic synapseNot myelinated and are smallSynaptic vesicles with norepinephrine (NE) inside1. Action potential2. Causes influx of calcium through Ca2+ channels3. Causes fusion of vesicles to membrane and exocytosis of NE4. NE released into the synaptic cleft binds to adrenergic receptors on the effector cell5. ResponseReceptors for NE are called Adrenergic receptors because NE is also known as adrenalineUsually G protein coupled receptorsAction terminated by usual mechanismsCarried away by blood vesselsDegraded by enzymes in extracellular space(COMT)Active transport reuptake of NE into presynaptic membrane where it can be repackaged or digested by mitochondrial monoamine oxidase (often used for therapeutic purposes)Autonomic PathwaysDifference between the pathway flow of parasympathetic and sympathetic informationParasympathetic = CraniosacralAt the top and bottom in the cranial nerve and the sacral nucleiOutflow is said to be cranial sacralPresynaptic neurons are in bluePreganglionic axons are very long and in most cases there isn’t really a ganglion but if they are present they are really close or embedded into the target organPostganglionic axons very shortSympathetic = ThoracolumbarOutflow is in the middle partThorax lumbar region (red dots)Intermediate horn of the spinal cordSend their axons out of CNS and make synapses in ganglia1. Cervical ganglianeck2. Prevertebral sympathetic ganglia chainNext to the vertebraePreganglionic neurons make synapse onto postganglionic neuron which send neurons off to target (red lines)Can also make synapses in ganglia that are not part of the chain3. Adrenal medullaadrenal glandBISC 307L 1st Edition Lecture 9Current Lecture- Sound Localizationo Network of neurons that receive inputs from the left and right ears- Coincidence detectors from both sideso One input alone is not sufficient to generate an action potential but 2 simultaneous EPSPs can sum and produce an action potentialo If sound comes from in front of you The peak will hit right in the middle – C on diagramo Input from right ear  has more time to get to point A before left input gets there so that’s where you will hear it o Sound coming from left ear Will travel and hit point E as Right ear input is hitting that point and thus that is where


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USC BISC 307L - Autonomic Nervous System I

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