BIOL 200B 1st Edition Lecture 17 Chapter 46.3 Synapse (pgs 938)Chapter 47.1 Sensory Signals (pgs 952-955)Synapse – junction of 2 neurons- Neurotransmitter carries information across synaptic clef- Presynaptic neuron synthesizes and packages neurotransmitters in synaptic vesicles- Voltage gated Ca2+ channels respond to action potential = influx of Ca2+- Causes release of neurotransmitter- Neurotransmitter diffuses across synaptic clef and binds receptor channels on postsynaptic cellNeurotransmitters- Dopamine in brain controls body movement - Epinephrine (adrenaline) “fight or flight” response- Serotonin – sleep regulation- Neuropeptides release from sensory neurons activated by painful stimuli – intensity of pain perception depends on endorphinsDrug addiction- Cocaine affects neurons in brain’s “pleasure pathways”- Binds dopamine transporters and prevents dopamine reuptakePostsynaptic Potential- Neuron may induce or inhibit depolarization by downstream neuron:o Excitatory postsynaptic potential (EPSPs) – depolarizationo Inhibitory postsynaptic potential (IPSPs) – hyperpolarization- Postsynaptic cells perform summation on all incoming signalsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Results in graded responses (not all-or-none)Sensory Transduction: Sense organs are transducers, they convert external stimuliSensory organs and receptors fall into 6 categories:1. Mechanoreceptors2. Thermoreceptors3. Pain receptors4. Chemoreceptors 5. Electromagnetic receptors6. PhotoreceptorsAnatomy of each sensory organ determined by its functionEx: mechanoreceptor - Hair cells – respond to changes in pressure waves in water or air (lateral lines of fish, found in human ears)- Fluid movement causes inhibition or excitation as stereocilia moves towards or away from kinocilium - Causes depolarization or hyperpolarization- Neurotransmitter release regulates action potential in sensory neuron- Amount of depolarization or hyperpolarization = intensity of stimulusSound Transduction and Hearing - Hair cells in ear depolarize in response to sound- Loud sounds produe more frequent nerve impulses- Neurons from each category of sensory organs have synapse connections….Specialized sound detection in vertebrates: - Elephants hear infrasound (low frequency, beyond human range)- Bats emit and hear ultrasound (higher frequency, beyond human
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