physiology ch10 lecture

physiology ch10 lecture - LECTURE OUTLINE (CHAPTER 10)...

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LECTURE OUTLINE (CHAPTER 10) LECTURE OBJECTIVES 1. Establish how sensory neurons interpret specific stimuli. 2. How is this sensory information processed in the PNS and CNS? 3. Discuss some of the conditions that result from malfunction of sensory input. LECTURE OUTLINE I. INTRODUCTION A. Primary functions of the Peripheral Nervous System (PNS) 1. Sensory input 2. Motor output B. Types of sensory neurons C. General characteristics of sensory neurons 1. Graded response which results in an action potential once threshold is reached. 2. Two types of potentials: Receptor and Generator Potentials Generator potentials- ex. As result of painful stimulus-an action potential would start under receptor portion of cell and moves to terminal. This is dif. from starting at hillock, essentially starts at dendrite here. Some sensory fibers don’t have myelin, info gets there fairly quickly, but when myelinated much much quicker. Some stimulus that is directly causing development of an action potential=generator potential. Ex. Is pain. Receptor potential= receptor cell first and then synapse- neurotransmitter activates the postsynaptic sensory afferent to fire an action potential. Stimulus uses neurotransmitter release. Ex. Is taste a. Dendritic action potentials-cell fires in a number of ways- tonic and phasic are types: 3. Tonic verses Phasic firing - cell that fires regularly=tonic sensory receptor, ex. In arm while holding arm up, not moving. Phasic receptors fire primarily when there’s a change in an event- something happens or something stops. Determines changes in events, like raising arm (not holding it up). Tonic-continuity; phasic-change. 4. Lateral inhibition -both receptors have this; a number of receptors are lined up and sensory receptors release neurotransmitters, but then secondary neurons inhibit release of outer two- this is presynaptic inhibition. Purpose is it permits you
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to feel a specific point (pin prick on back of hand) feel is well b/c all cells around where prick is are shut down. Permits us to feel things more precisely or see points of light more clearly. 5. Receptive fields - both have again. One sensory afferent fires if there’s stimulus in this certain area (in this receptive field). Receptive fields can cross over. D. Introduction to sensory pathways to brain 1. Sensory systems often map to specific cortical locations. Thalamus projects up to somatosensory cortex. Somatotopic map= Point-to-point map in the brain of the entire body. Lips and tongue-tremendous abilities w/ lip and tongue movement, not so much knee-it just bends. A lot of these maps exist in the brain and they are point-on-point maps. II. PAIN A. Nociceptor (a sensory receptor associated w/ pain) structure and function: pain receptors can be myelinated or unmyelinated (fast or slow). Two types of pain (slow and fast pain). 1. Similarities between nociceptors (pain) and thermoreceptors
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This note was uploaded on 04/07/2008 for the course IPHY 3430 taught by Professor Lynch,robe during the Spring '08 term at Colorado.

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physiology ch10 lecture - LECTURE OUTLINE (CHAPTER 10)...

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