Ch 15 Sensory Information 01 13 2016 Describe the differences between the afferent and efferent divisions of the nervous system Afferent Approaches CNS Division of the Nervous System Receptors detects stimuli Sensory neurons relays sensory information towards the CNS receives input from dendrite uses axon to send it to CNS Sensory pathways nerves nuclei and tracts bundle of axons that deliver sensory information to the CNS Efferent Exits CNS Division of Nervous System Nuclei contain cell bodies of motor neurons Motor neurons send commands to effectors through motor tracts axons in the CNS or nerves axons in the PNS Describe the types of stimuli that are detected by our general senses and special senses General Senses Describe our sensitivity to o Temperature o Pain o Touch o Pressure o Vibration o Proprioception monitors the position and movements of skeletal muscles and joints Special Senses sensory receptors are all located in the head Olfaction smell Vision sight Gustation taste Equilibrium balance Hearing What is the difference between these two senses o The Special Senses Are provided by special sensory receptors o Special Sensory Receptors Are located in sense organs such as the eye or ear Are protected by surrounding tissues Explain the difference between sensation and perception Sensation The arriving information from these senses Perception Conscious awareness of a sensation Explain why receptor specificity and the size of the receptive field are important in stimulus detection and localization The Detection of Stimuli Receptor specificity o Each receptor has a characteristic sensitivity Ex Your hands do not smell nor taste your eyes do not hear etc Receptive field o Area is monitored by a single receptor cell o Can only detect a stimulus within a certain range poke your finger with a pencil only a few receptors are stimulated o The larger the receptive field the more difficult it is to localize o Smaller the receptor field the more accurate you can a stimulus pinpoint a stimulus Explain how specific stimuli are relayed to the central nervous system what is labeled line The Interpretation of Sensory Information Arriving stimulus reaches cortical neurons via labeled line link between the receptor and cortical neuron o Only one pathway will send info about temp while another one is sending info about pain o Each labeled line consists of axons carrying info about one type of stimulus modality Physical force such as pressure Dissolved chemical Sound Light Sensations receptor cells o Taste hearing equilibrium and vision provided by specialized o Communicate with sensory neurons across chemical synapses Describe adaptation and how it can affect our perception of a stimulus What is the difference between central and peripheral adaptation Adaptation Reduction in sensitivity of a constant stimulus ex Walking into an elevator someone is wearing too much cologne eventually get used to smell Your nervous system quickly adapts to stimuli that are painless and constant o Ex New smells pressure wearing jewelry Types of adaptation o Central Adaptation Inhibition of nuclei along a sensory pathway CNS ignores input occurs in the CNS Ex New smells still stimulate sensory receptor but cortical neurons no longer respond to the stimulation o Peripheral Adaptation Occurs at the level of the receptor become less sensitive to stimulus receptor responds initially to stimulus then stops Ex Thermoreceptors go into a hot tub but your body eventually adjusts Stimulation of a receptor produces action potentials o Along the axon of a sensory neuron The frequency and pattern of action potentials contain information o About the strength duration and variation of the stimulus Your perception of the nature of that stimulus o Depends on the path it takes inside the CNS Explain the difference between tonic and phasic receptors Tonic receptors Are always active Show little peripheral adaptation Are slow adapting receptors don t lose ability to respond to stimulus Phasic receptors Remind you of an injury long after the initial damage has occurred o Ex Pain receptors nociceptors Are normally inactive Become active for a short time whenever a change occurs Are fast adapting receptors Provide information about the intensity and rate of change of a stimulus o Ex Thermoreceptors detect rapid changes in temperature Describe the three broad categories of sensory receptors Classifying Sensory Receptors Exteroceptors provide information about the external environment Proprioceptors report the positions of skeletal muscles and joints Interoceptors monitor visceral organs and functions Proprioceptors Provide a purely somatic sensation No proprioceptors in the visceral organs of the thoracic and abdominopelvic cavities the moment o You cannot tell where your spleen appendix or pancreas is at Describe the four types of general sensory receptors 1 Nociceptors pain 2 Thermoreceptors temperature 3 Mechanoreceptors physical distortion 4 Chemoreceptors chemical concentration What are some specific example of these receptors and their function Nociceptors Pain Receptors o Are common In the superficial portions of the skin In joint capsules Within the periostea of bones Around the walls of blood vessels o Analgesia inability to feel pain o Hypergesia increased sensitivity to pain o May be sensitive to Temperature extremes Mechanical damage Dissolved chemicals such as chemicals released by injured cells o Are free nerve endings with large receptive fields Branching tips of dendrites Not protected by accessory structures Can be stimulated by many different stimuli Two types of axons Type A large myelinated and Type C small unmyelinated fibers Thermoreceptors o Also called temperature receptors o Are free nerve endings located in The dermis Skeletal muscles The liver The hypothalamus Mechanoreceptors o Sensitive to stimuli that distort their plasma membranes o Contain mechanically gated ion channels whose gates open or close in response to Stretching Compression Twisting Other distortions of the membrane Chemoreceptors o Respond only to water soluble and lipid soluble substances dissolved in surrounding fluid o Receptors exhibit peripheral adaptation over period of seconds Central adaptation may also occur o Receptors that monitor pH carbon dioxide and oxygen levels in arterial blood are located in Carotid bodies each side of the neck Aortic bodies Near the origin of the internal carotid arteries on Between the major branches of
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