BSC2086 Anatomy Physiology II Exam 1 Study Guide Lesson 1 General Senses Sensory Information Afferent division of the nervous system involves o Receptors detect the stimuli o Sensory neurons relay the info down their axons o Sensory pathways nerves nuclei tracts that deliver sensory info to the CNS Efferent division of the nervous system involves o Nuclei contain the cell bodies of motor neurons o Motor tracts nerves carry commands to effectors muscles glands Sensory Receptors Specialized cells that monitor specific conditions in the body or external environment o Passes information as action potentials along the axon of a sensory neuron to the CNS when stimulated Sensory Pathways Deliver somatic visceral sensory information to their final destinations in the CNS using o Nerves Axon bundles in the PNS o Nuclei Cell bodies located in the CNS o Tracts Axon bundles in the CNS Somatic motor portion of the efferent division controls peripheral effectors Somatic motor commands travel from motor centers in the brain along somatic Somatic Nervous System SNS Motor neurons and pathways that control motor pathways of o Motor nuclei o Tracts o Nerves skeletal muscles 1 BSC2086 Anatomy Physiology II Exam 1 Study Guide Sensory Receptors 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 Sensation The arriving information from these senses Perception Conscious awareness of a sensation Special Senses o Olfaction Smell o Vision Sight o Gustation Taste o Equilibrium Balance o Hearing Special senses are provided by special sensory receptors Special Sensory Receptors Located in sense organs i e eye or ear o Protected by surrounding tissues Receptor specificity each receptor has a characteristic sensitivity o Your hands don t smell or taste your eyes don t hear etc Receptive field o Area monitored by a single receptor cell o Larger receptive fields make it more difficult to localize a stimulus Interpretation of Sensory Information Arriving stimulus reaches cortical neurons via labeled line link between receptor and cortical neuron o Each labeled line carries info about one modality form Such as Physical force pressure Dissolved chemical Sound Light 2 BSC2086 Anatomy Physiology II Exam 1 Study Guide Taste hearing equilibrium and vision provided by specialized receptor cells Sensory Receptor Adaptation Adaptation Reduction in sensitivity of a constant stimulus o Nervous system quickly adapts to stimuli that are painless constant Ex New smells clothes earrings Tonic Receptors Slow adapting receptors that are always active o Show little peripheral adaptation Ex Pain receptors nociceptors remind you of an injury long after the initial damage has occurred Phasic Receptors Fast adapting receptors that are normally inactive o Become active for a short time whenever a change occurs o Provide information about the intensity and rate of change of a stimulus Ex Thermoreceptors detect rapid changes in temperature Stimulation of a receptor produces action potentials along the axon of a sensory neuron The frequency 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 in the CNS Types of Sensory Receptors Exteroceptors Provide information about the external environment Proprioceptors Report the positions of skeletal muscles and joints o Provide purely somatic sensation o Not located in the visceral organs of the thoracic abdominopelvic cavities now You can t tell where your spleen appendix or pancreas is right Interoceptors Monitor visceral organs and functions General Sensory Receptors divided into four 4 types by the nature of the Nociceptors Pain Receptors Free nerve endings with large receptive fields stimulus that excites them o Nociceptors pain o Thermoceptors temperature o Mechanoreceptors physical distortion o Chemoreceptors chemical concentration o Branching tips of dendrites o Not protected by accessory structures o Can be stimulated by many different stimuli o Two types of axons Type A Large myelinated fibers Carry sensations of fast pain prickling pain o Ex Pain caused by injection or a deep cut Sensations reach the CNS quickly and often trigger somatic Relayed to the primary sensory cortex and receive reflexes conscious attention 3 BSC2086 Anatomy Physiology II Exam 1 Study Guide Type C Small unmyelinated fibers Carry sensations of slow pain burning aching pain Cause a generalized activation of the reticular formation You become aware of the pain but only have a general idea thalamus of the area affected o Common in Superficial portions of skin Joint capsules Periostea of bones Walls of blood vessels o May be sensitive to Temperature extremes Mechanical damage Dissolved chemicals Ex Chemicals released by injured cells o Analgesia Inability to feel pain o Hyperalgesia Increased sensitivity to pain Thermoreceptors Temperature Receptors Free nerve endings o Located in Dermis Skeletal muscles Liver Hypothalamus sensations o Sent to o 3 4x more cold receptors than warm receptors o Temperature sensations conducted along the same pathways as pain Reticular formation Thalamus Primary sensory cortex lesser extent Mechanoreceptors o Sensitive to stimuli that distort their plasma membranes o Contain mechanically gated ion channels Gates open or close in response to Stretching Compression Twisting Other distortions of the membrane o Three 3 classes vibration Tactile Receptors Provide the sensations of touch pressure and Touch sensations information about shape texture Pressure sensations degree of mechanical distortion Vibration sensations pulsing or oscillating pressure Fine touch and pressure receptors 4 BSC2086 Anatomy Physiology II Exam 1 Study Guide o Extremely sensitive o Have relatively narrow receptive fields o Detailed information about a source of stimulation Exact location shape size texture Crude and pressure receptors movement o Have relatively large receptive fields o Provide poor localization o Give little information about the stimulus Six 6 types of tactile receptors in the skin o Free Nerve Endings Sensitive to touch pressure Located between epidermal cells Free nerve endings providing touch sensations tonic receptors have small receptive fields o Root Hair Plexus Nerve Endings Monitor distortions movements across body surface wherever hairs
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