Autonomic Nervous System I

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Autonomic Nervous System I

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University of Southern California
Bisc 307l - General Physiology
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BISC 307L 1st Edition Lecture 9 Current Lecture  Sound Localization o Network of neurons that receive inputs from the left and right ears- Coincidence detectors from both sides o One input alone is not sufficient to generate an action potential but 2 simultaneous EPSPs can sum and produce an action potential o If sound comes from in front of you  The peak will hit right in the middle – C on diagram o 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 you process the sound o Binaural- Simultaneous excitation at the same time from both ears causes action potential o How 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 microsecond  Self correcting for sloppiness  Sound Localization in Medical Superior Olive o A model of a circuit in the medial superior olive of a cat  Found:  Not only an array of place and coding neurons that looks like the diagram in the previous slide but there’s thousands of these diagrams  These different arrays map out the frequencies of the sounds (sensitive to different frequencies) More like 10,000 neurons in an array Autonomic Nervous System 1  Slide 1- General Properties of ANS o Provides critical homeostatic mechanisms- More than any other system  We will focus on efferent functions of ANS (as opposed to afferent)  Efferent= carrying away from CNS  Motor commands  secretion  Afferent = carrying towards CNS  Sensory o Reflexes mediated by local circuits in spinal cord and brainstem  Both sensory and effector  “Local”- do not really involve brain (involves brain stem instead) o An effector (efferent) and sensory (somatosensory and visceral afferents) system  Sensory part:  1. Somatosensory (touch)  2. Visceral (organs) o 2 (or 3) divisions of Efferent:  1. Sympathetic  fight or flight  2. Parasympathetic  rest and digest  3. (Enteric)  Biggest part! Although not stressed as much for some reason  Nerves (sensory and effector) in the walls of the digestive tract  Responses to/ Recovery from Emergencies- Balance between the two responses o 1. Fight or flight response (Sympathetic)  increase respiratory rate  increase heart rate

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