Exam 1 Learning Objectives Lesson 1 the nervous system o Afferent Describe the differences between the afferent and efferent divisions of 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 that deliver sensory information to the CNS o Efferent 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 o General senses describe our sensitivity to Temperature Pain Touch Pressure Vibration Proprioception monitors the position and movements of skeletal muscles and joints o Special senses sensory receptors are all located in the head Olfaction smell Vision sight Gustation taste Equilibrium balance Hearing o What is the difference between these two senses Special senses are provided by special sensory receptors and are located in sense organs such as the eye or ear and are protected by surrounding tissues Explain the difference between sensation and perception the arriving information from these senses conscious awareness of a sensation o Sensation o Perception Explain why receptor specificity and the size of the receptive field are important in stimulus detection and localization o Receptor specificity Each receptor has a characteristic sensitivity Example your hands do not smell nor taste your eyes do not hear etc o Receptive field a stimulus what is labeled line Area is monitored by a single receptor cell The larger the receptive field the more difficult it is to localize Explain how specific stimuli are relayed to the central nervous system 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 constant adaptation Central in the CNS Describe adaptation and how it can affect our perception of a stimulus o Reduction in sensitivity of a constant stimulus o Your nervous system quickly adapts to stimuli that are painless and Ex New smells pressure wearing jewelry o What is the difference between central and peripheral inhibition of nuclei along a sensory pathway occurs Ex New smells still stimulate sensory receptor but cortical neurons no longer respond to the stimulation Peripheral responds initially to stimulus then stops occurs at the level of the receptor receptor Ex thermoreceptors Explain the difference between tonic and phasic receptors o Tonic receptors Show little peripheral adaptation Are always active Are slow adapting receptors Remind you of an injury long after the initial damage has occurred Ex Pain receptors nociceptors o Phasic receptors 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 Ex Thermoreceptors detect rapid changes in temperature Describe the three broad categories of 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 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 o Nociceptors pain o Thermoreceptors temperature o Mechanoreceptors physical distortion o Chemoreceptors chemical concentration o What are some specific example of these receptors and their function Nociceptors Pain Receptors Are common o In the superficial portions of the skin o In joint capsules o Within the periostea of bones o Around the walls of blood vessels Analgesia inability to feel pain Hypergesia increased sensitivity to pain May be sensitive to o Temperature extremes o Mechanical damage o Dissolved chemicals such as chemicals released by injured cells Are free nerve endings with large receptive fields 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 and Type C small unmyelinated fibers 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 attention 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 affected Thermoreceptors Also called temperature receptors Are free nerve endings located in o The dermis o Skeletal muscles o The liver o The hypothalamus Temperature sensations pain sensations o Sent to o Conducted along the same pathways that carry The reticular formation The thalamus The primary sensory cortex to a lesser Mechanoreceptors extent Chemoreceptors Sensitive to stimuli that distort their plasma membranes Contain mechanically gated ion channels whose gates open or close in response to o Stretching o Compression o Twisting o Other distortions of the membrane Respond only to water soluble and lipid soluble substances dissolved in surrounding fluid Receptors exhibit peripheral adaptation over period of seconds o Central adaptation may also occur Receptors that monitor pH carbon dioxide and oxygen levels in arterial blood are located in o Carotid bodies Near the origin of the internal carotid arteries on each side of the neck Aortic bodies Between the major branches of the o What are the different classes of mechanoreceptors aortic arch Tactile receptors Provide the sensations of touch pressure and vibration o Touch sensations provide information about shape or texture o Pressure sensations indicate degree of mechanical distortion o Vibration sensations indicate pulsing or oscillating pressure Fine touch and pressure receptors o Are extremely sensitive o Have a relatively narrow receptive field o Provide detailed information about a source of o Including its exact location shape size texture stimulation movement Crude touch and pressure
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