BISC 307L 1st Edition Lecture 9 Current Lecture Sound Localization o Network of neurons that receive inputs from the left and right earsCoincidence 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 vasodilation in limb muscles also brain vasoconstriction in viscera intestines skin dilation of lung airways decrease secretion in mouth and gut increase general alertness open iris to let in more light fright o 2 Rest and digest Parasympathetic decrease respiration to resting level decrease heart rate to resting level vasoconstriction in limb muscles vasodilation in viscera constriction of lung airways secretion returns to normal alertness returns to normal CNS Centers regulating the ANS o o Brain Some of the centers which are mostly in the brain stem which are important to autonomic control system o Hypothalamus Small but packed with small nuclei that are not well defined Ultimate control of eating water balance thirst control temperature appetitive behaviors sex salt Small number of neurons for such important things Damage in behavior with damage to hypothalamus o Pons o Medulla Pre and postganglionic neurons o o How the ANS works Activity originates in the brain stem as a result of sensory information coming in Commands 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 slow Postganglionic Sympathetic synapses o Know this Synthetic pathway Tyrosine DPA dopamine norepinephrines epinephrine The last 4 are catecholamines structure Last two are in the brain or PNS Depends on the enzyme it has for which one is released o o Postganglionic sympathetic synapse Not myelinated and are small Synaptic vesicles with norepinephrine NE inside 1 Action potential 2 Causes influx of calcium through Ca2 channels 3 Causes fusion of vesicles to membrane and exocytosis of NE 4 NE released into the synaptic cleft binds to adrenergic receptors on the effector cell 5 Response Receptors for NE are called Adrenergic receptors because NE is also known as adrenaline Usually G protein coupled receptors Action terminated by usual mechanisms Carried away by blood vessels Degraded 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 Pathways o Difference between the pathway flow of parasympathetic and sympathetic information Parasympathetic Craniosacral At the top and bottom in the cranial nerve and the sacral nuclei Outflow is said to be cranial sacral Presynaptic neurons are in blue Preganglionic 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 organ Postganglionic axons very short Sympathetic Thoracolumbar Outflow is in the middle part Thorax lumbar region red dots Intermediate horn of the spinal cord Send their axons out of CNS and make synapses in ganglia 1 Cervical ganglia neck 2 Prevertebral sympathetic ganglia chain Next to the vertebrae Preganglionic 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 chain 3 Adrenal medulla adrenal gland