Lesson 1 Check Off List Describe the differences between the afferent and efferent divisions of the nervous system o Afferent Division of the Nervous system Receptors detects stimuli Sensory pathways the CNS Sensory Receptors Sensory neurons dendrite uses axon to send it to CNS relays sensory info towards the CNS receives input from nerves nuclei and tracts that deliver sensory information to Sensory Pathways Specialized cells that monitor specific conditions in the body or external environment When stimulated a receptor passes information to the CNS o In the form of action potentials along the axon of a sensory neuron inside the body o Can be either interoceptors inside the body or exteroceptors o Review ch 12 pages 398 416 if you need to refresh memory on APs and synaptic transmission Deliver somatic and visceral sensory information to their final destinations inside the CNS using o Nerves bundle of axons located in the PNS o Nuclei cluster of cell bodies located in the CNS o Tracts bundle of axons located in the CNS For example nerves from arm bring sensory information to spinal cord o Axon terminal synapse onto interneurons in spinal cord cell bodies clustered together nucleus These cell bodies send info up to brain through axon bundles now called tracts since inside the CNS o Efferent Division of the 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 Somatic Motor Portion of the Efferent Division controls peripheral effectors Somatic Motor Commands Travel from motor centers in the brain along somatic motor pathways of o Motor Nuclei o Tracts o Nerves Describe the types of stimuli that are detected by our general senses and special senses Somatic Nervous System SNS motor neurons and pathways that control skeletal muscles 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 o Olfaction smell o Vision sight o Gustation taste o Equilibrium balance o Hearing What is the difference between these two senses o The Special Senses are provided by special sensory receptors 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 o Receptor specificity Each receptor has a characteristic sensitivity Ex Your hands do not smell nor taste your eyes do not hear etc Can only detect the stimuli that they are for o Receptive Field Area is monitored by a single receptor cell The larger the receptive field the more difficult it is to localize a stimulus Explain how specific stimuli are relayed to the central nervous system what is labeled line The Interpretation of Sensory Information o Arriving stimulus reaches cortical neurons via labeled line link between the receptor and cortical neuron Each labeled line consists of axons carrying info about one type of stimulus modality Physical force such as pressure Dissolved chemical Sound Light o Sensations Taste hearing equilibrium and vision provided by specialized receptor cells Communicate with sensory neurons across chemical synapses Describe adaptation and how it can affect our perception of a stimulus Reduction in sensitivity of a constant stimulus Your nervous system quickly adapts to stimuli that are painless and constant o Ex New smells pressure wearing jewelry Adaptation o Stimulation of a receptor produces action potentials along the axon of a sensory o The frequency and pattern of action potentials contain information about the strength duration and variation of the stimulus o Your perception of the nature of that stimulus depends on the path it takes inside neuron the CNS What is the difference between central and peripheral adaptation Types of Adaptation a Central inhibition of nuclei along a sensory pathway occurs in the CNS i Ex New smells still stimulate sensory receptor but cortical neurons no longer respond to the stimulation b Peripheral occurs at the level of the receptor receptor responds initially to stimulus then stops i Ex thermoreceptors Explain the difference between tonic and phasic receptors Tonic receptors are always active o Show little peripheral adaptation o Are slow adapting receptors o Remind you of an injury long after the initial damage has occurred Ex Pain receptors nociceptors Phasic Receptors are normally inactive o Become active for a short time whenever a change occurs o Are fast adapting receptors o Provide information about the intensity and rate of change of a stimulus Ex Thermoreceptors detect rapid changes in temperature Describe the three broad categories of sensory receptors Classifying Sensory Receptors o Exteroceptors provide information about the external environment o Proprioceptors report the positions of skeletal muscles and joints Provide a purely somatic sensation No proprioceptors in the visceral organs of the thoracic and abdominopelvic cavities so only attached to muscles bones You cannot tell where your spleen appendix or pancreas is at the moment o Interoceptors monitor visceral organs and functions Describe the four types of general sensory receptors General Sensory Receptors are divided into 4 types by the nature of the stimulus that excites them 1 Nociceptors pain are common In the superficial portions of the skin In joint capsules Within the periostea of bones Around the walls of blood vessels Analgesia inability to feel pain Hypergesia May be sensitive to increased sensitivity to pain Temperature extremes Mechanical damage Dissolved chemicals such as chemicals released by injured cells 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 o Myelinated Type A fibers o Type C 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
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