9 - Molecular Cell Biology 32 Professor Andrew Wurmser...

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Molecular Cell Biology 32 Professor Andrew Wurmser 9/25/07 Lecture 9 Sharing or distribution of lecture notes, or sharing of your subscription, is ILLEGAL and will be prosecuted. Our non-profit, student-run program depends on your individual subscription for its continued existence. These notes are copyrighted by the University of California and are for your personal use only. Sharing or copying these notes is illegal and could end note taking for this course ANNOUNCEMENTS - Review Session in 10 Evans on Wednesday from 5-7pm. - Dr. Lew’s reader available Friday at Replica Copy (2138 Oxford, near Ben and Jerry’s). Bring it to class next Tuesday. Replica Copy Hours: 8:30 am – 7 pm M-F, 10 am – 6 pm Sat Phone number: 549-9991 - Midterm on Thursday; scantrons will be provided. LECTURE: Sensory Neurophysiology and Review of Important Concepts We will review a lot of primary topics taught thus far and highlight some points that I think will be important for the midterm. What I covered are basic terms and processes that you will need throughout the rest of the course. Sensory Neurophysiology Receptors that mediate sensation are classified according to structure and function. Mechanoreceptors are sensitive to deformation, roughness, and stretch. Thermoreceptors are responsible for detecting heat and cold. The hypothalamus has temperature receptors that cause depolarization of neurons to react to temperature. Chemoreceptors respond to chemical stimuli and operate in olfaction and taste. Photoreceptors are involved with rods and cones to detect light. Nociceptors are the pain receptors. How are these diverse sensory inputs converted into action potentials? Mechanical force is perceived by mechanoreceptors. This force temporarily deforms the cell, which causes a depolarization event and the initiation of an action potential. Photoreceptors are sensitive to light and initiate photochemical sensitive events that translate photons of light into action potentials. Tonic receptors respond to stimuli in a uniform way and initiate a constant level of action potentials (APs). With tonic receptors, there is a constant, uniform wave of action potentials until the stimulus is withdrawn. This phenomenon is found in the non-adaptive response involved in pain. Phasic receptors are sensitive to the application and withdrawal of stimulus. Unlike tonic receptors, there is a non-uniform burst of action potentials when the stimulus is initially applied. Sensory receptors couple to generator potentials . This results in the activation of a sensory cell to undergo an action potential. Generator potentials are additive in nature. Temporal summation is the number of action potentials that are occurring within the cell. Spatial summation is the number of pre-synaptic neurons that occur before a neuron. If a certain threshold is met, an action potential is generated. Remember that action potentials are an all or none process. Generator potentials are translated into action potentials. A stimulus can be
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9 - Molecular Cell Biology 32 Professor Andrew Wurmser...

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