8 - Molecular and Cell Biology 32 Professor Andrew E....

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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: -No Announcements. LECTURE: Today we will review reflex reactions and will be introducing the autonomic and somatic nervous systems. We will talk about how the autonomic system enervates every organ in the body. Each of these effects on the organ is mediated by two different neurotransmitters. This allows diversity of signaling. The take-home message for today is that the interaction between the autonomic nervous system and organs is not diverse because of the number of neurotransmitters, but because of aspects of the target tissues themselves. These target tissues express different receptors for the neurotransmitters and have different second messenger systems that deliver signals from the receptors to trans-membrane ion channels within the cell. Review: Last lecture we introduced somatic motor reflexes. Reflexes occur in the autonomic nervous system. Remember the process from last lecture. First comes the input of sensory neurons into the spinal chord. Once the neuron is in the spinal chord it travels through the dorsal root and enervates an interneuron which in turn enervates a motor neuron that exits through the ventral root to stimulate an affector muscle. Sensory neurons typically have a pseudounipolar structure, meaning there is one process that extends from the cell body. Somatic motor neurons have multiple dendrites and a single axon. This is called a multipolar neuron. We’ll talk about bipolar neurons on Tuesday, which have two processes extending from their cell bodies. (One dendrite and one axon.) The Somatic and Autonomic Nervous System: Figure: The subdivisions of the central nervous system. Central Nervous System - - - - - - Autonomic Somatic - - - - - - Sympathetic Parasympathetic The somatic nervous system involves voluntary motor action through the mediation of descending motor neurons. The autonomic nervous system involuntarily enervates glands and smooth muscles that surround many of our organs in order to sustain vital functions. In this process, a single sensory neuron that is pseudounipolar goes into the spinal chord and enervates an interneuron. This interneuron enervates a pre-ganglionic neuron, which in turn stimulates a postganglionic neuron that emanates from the spinal chord. Finally, the
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8 - Molecular and Cell Biology 32 Professor Andrew E....

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