NVC BIOL 105 - The General and Special Senses

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Copyright © 2010 Pearson Education, Inc.C h a p t e r9The General and Special SensesPowerPoint® Lecture Slides prepared by Jason LaPresLone Star College - North HarrisCopyright © 2010 Pearson Education, Inc.Copyright © 2010 Pearson Education, Inc.9-1 Sensory receptors connect our internal and external environments with the nervous systemCopyright © 2010 Pearson Education, Inc.Sensory Receptors• Specialized cells that monitor specific conditions in the body or external environment• When stimulated, a receptor passes information to the CNS in the form of action potentials along the axon of a sensory neuronCopyright © 2010 Pearson Education, Inc.Sensory Receptors• Sensation– The arriving information from these senses• Perception– Conscious awareness of a sensationCopyright © 2010 Pearson Education, Inc.Sensory Receptors• The Detection of Stimuli– Receptor sensitivity:• Each receptor has a characteristic sensitivity– Receptive field:• Area is monitored by a single receptor cell• The larger the receptive field, the more difficult it is to localize a stimulusCopyright © 2010 Pearson Education, Inc.Receptors and Receptive FieldsFigure 9-1Copyright © 2010 Pearson Education, Inc.Sensory Receptors• The Interpretation of Sensory Information– Arriving stimulus: • Takes many forms:– physical force (such as pressure)– dissolved chemical– sound– lightCopyright © 2010 Pearson Education, Inc.Sensory Receptors• The Interpretation of Sensory Information – Sensations: • Taste, hearing, equilibrium, and vision provided by specialized receptor cells• Communicate with sensory neurons across chemical synapsesCopyright © 2010 Pearson Education, Inc.Sensory Receptors• Adaptation– Reduction in sensitivity of a constant stimulus– Your nervous system quickly adapts to stimuli that are painless and constantCopyright © 2010 Pearson Education, Inc.Sensory Receptors• General Senses – Describe our sensitivity to:• Temperature• Pain• Touch• Pressure• Vibration• ProprioceptionCopyright © 2010 Pearson Education, Inc.Sensory Receptors• Special Senses– Olfaction (smell)– Vision (sight)– Gustation (taste)– Equilibrium (balance)– HearingCopyright © 2010 Pearson Education, Inc.Sensory Receptors• Stimulation of a receptor produces action potentials along the axon of a sensory neuron • The frequency and pattern of action potentials contain information about the strength, duration, and variation of the stimulus • Your perception of the nature of that stimulus depends on the path it takes inside the CNSCopyright © 2010 Pearson Education, Inc.9-2 General sensory receptorscan be classified by the typeof stimulus that excites themCopyright © 2010 Pearson Education, Inc.Classifying Sensory Receptors• General sensory receptors are divided into four types by the nature of the stimulus that excites them– Nociceptors (pain)– Thermoreceptors (temperature)– Mechanoreceptors (physical distortion)– Chemoreceptors (chemical concentration)Copyright © 2010 Pearson Education, Inc.Pain• Nociceptors (also called pain receptors)– Are common in the superficial portions of the skin, joint capsules, within the periostea of bones, and around the walls of blood vessels– May be sensitive to temperature extremes, mechanical damage, and dissolved chemicals, such as chemicals released by injured cellsFigure 15–2Copyright © 2010 Pearson Education, Inc.Pain• Nociceptors – 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 and Type C fibersCopyright © 2010 Pearson Education, Inc.Pain• Nociceptors – Myelinated Type A fibers: • Carry sensations of fast pain, or prickling pain, such as that caused by an injection or a deep cut• Sensations reach the CNS quickly and often trigger somatic reflexes• Relayed to the primary sensory cortex and receive conscious attentionCopyright © 2010 Pearson Education, Inc.Pain• Nociceptors – Type C fibers:• Carry sensations of slow pain, or burning and aching pain• Cause a generalized activation of the reticular formation and thalamus• You become aware of the pain but only have a general idea of the area affectedCopyright © 2010 Pearson Education, Inc.Referred PainFigure 9-2Copyright © 2010 Pearson Education, Inc.Temperature• Thermoreceptors – Also called temperature receptors– Are free nerve endings located in:• The dermis• Skeletal muscles• The liver• The hypothalamusCopyright © 2010 Pearson Education, Inc.Temperature• Thermoreceptors– Temperature sensations:• Conducted along the same pathways that carry pain sensations• Sent to:– the reticular formation– the thalamus– the primary sensory cortex (to a lesser extent)Copyright © 2010 Pearson Education, Inc.Touch, Pressure, and Position• Mechanoreceptors – Sensitive to stimuli that distort their plasma membranes– Contain mechanically gated ion channels whose gates open or close in response to• Stretching• Compression• Twisting• Other distortions of the membraneCopyright © 2010 Pearson Education, Inc.Touch, Pressure, and Position• Tactile receptors– Provide the sensations of touch, pressure, and vibration:• Touch sensations provide information about shape or texture• Pressure sensations indicate degree of mechanical distortion• Vibration sensations indicate pulsing or oscillating pressureCopyright © 2010 Pearson Education, Inc.Tactile Receptors in the SkinFigure 9-3Copyright © 2010 Pearson Education, Inc.Tactile Receptors in the SkinFigure 9-3Copyright © 2010 Pearson Education, Inc.Tactile Receptors in the SkinFigure 9-3Copyright © 2010 Pearson Education, Inc.Tactile Receptors in the SkinFigure 9-3Copyright © 2010 Pearson Education, Inc.Tactile Receptors in the SkinFigure 9-3Copyright © 2010 Pearson Education, Inc.Tactile Receptors in the SkinFigure 9-3Copyright © 2010 Pearson Education, Inc.Touch, Pressure, and Position• Baroreceptors – Monitor change in pressure– Consist of free nerve endings that branch within elastic tissues in wall of distensible organ (such as a blood vessel)– Respond immediately to a change in pressure, but adapt rapidlyCopyright © 2010 Pearson Education, Inc.BaroreceptorsFigure 9-4Copyright © 2010 Pearson Education, Inc.Touch, Pressure, and Position• Proprioceptors – Monitor:•


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