BSC2086 Anatomy & Physiology II Exam #1 “You Should Be Able To”Lesson 1: General Senses Describe the differences between the afferent and efferent divisions of the nervous system- The afferent division of the nervous system carries sensory information to the CNS (ascending)o Made up of: Sensory pathways, sensory neurons, and their receptors- The efferent division of the nervous system carries motor information/commands away from the CNS to effectors – muscles & glands (descending)o Made of up: Nuclei, motor tracts, and motor neurons that control peripheral effectors Describe the types of stimuli that are detected by our general senses and special sensesGeneral Senses Special Senses- Temperature- Pain- Touch- Pressure- Vibration- Proprioception- Olfaction (smell)- Vision (sight)- Gustation (taste)- Equilibrium (balance)- Hearing What is the difference between these two senses?- General senses describe our sensitivity to temperature, pain, touch, pressure, vibration, and proprioceptiono Sensory receptors distributed throughout the body & relatively simple in structure- Special senses are olfaction (smell), vision (sight), gustation (taste), equilibrium (balance), and hearingo Sensory receptors located in sense organs & are structurally complex Explain the difference between sensation and perception- Sensation is the arriving information from these senses- Perception is the conscious awareness of a sensation Explain why receptor specificity and the size of the receptive field are important in stimulus detection and localization- Receptor Specificity: The characteristic sensitivity of a receptoro The more specific the receptor, the more specific the type of information it provides1BSC2086 Anatomy & Physiology II Exam #1 “You Should Be Able To” May result from structure of receptor cell or the presence of accessory cells/structures Complex receptors are more specific – only respond to certain stimuli- Ex) Eyes usually only exposed to light & provide very specific information- Receptive Field: The area monitored by a single receptor cello The larger the receptive field, the more difficult it is to localize a stimuluso Skin – can only describe general area of stimulus (light touch)o Tongue – can be very precise about location of a stimulus Explain how specific stimuli are relayed to the central nervous system (what is labeled line?)- Sensory information routed according to location & nature of stimuluso Different sensations arrive at their corresponding regions of the cortex Ex) Visual information to visual cortex- Labeled Line: The link between a peripheral receptor and cortical neurono Each labeled line consists of axons carrying info about one modality – type of stimuluso CNS interprets the modality entirely off of the labeled line Ex) Rub your eyes & see a flash of light because it arrives at the visual cortex & is interpreted as a visual perceptiono Identity of active labeled line indicates the type of stimuluso Where the labeled line arrives within the sensory cortex determines its perceived location Ex) Activity in a labeled line that carries touch sensations stimulates facialregion of primary sensory cortex, you perceive a touch on the face Describe adaptation and how it can affect our perception of a stimulus- Adaptation: A reduction in sensitivity in the presence of a constant stimuluso You gradually become less aware of a stimulus that is constant and painlesso Incoming sensory information is then processed in centers along the spinal cord orbrain stem at the subconscious levelo Ex) Clothes on your skin, a temperature change What is the difference between central and peripheral adaptation?- Central Adaptation: Adaptation that occurs along sensory pathways inside the CNSo Sensory neurons remain activeo Generally involves inhibition of nuclei along a sensory pathwayo Restricts the amount of detail that arrives at the cerebral cortex- Peripheral Adaptation: Adaptation that occurs when the level of receptor activity changeso Responds strongly at first but gradually declines2BSC2086 Anatomy & Physiology II Exam #1 “You Should Be Able To”o Reduces the amount of information that reaches the CNSo Characteristic of phasic receptors (fast-adapting receptors) Thermoreceptors: Temperature receptors- You rarely notice room temperature unless it changes suddenly Explain the difference between tonic and phasic receptors- Tonic receptors are slow-adapting receptors that are always activeo Show little peripheral adaptationo Background level of stimulation- Phasic receptors are fast-adapting receptors that are normally inactiveo Become active whenever change occurso Provide info about the intensity & rate of change of a stimulus Describe the three broad categories of sensory receptors- Exteroceptors provide information about the external environment- Proprioceptors report the positions of skeletal muscles and joints- Interoceptors monitor visceral organs and functions Describe the four types of general sensory receptors. What are some specific examples of these receptors and their function?- Nociceptors: Pain receptorso Free nerve endings with large receptive fieldso Can be stimulated by many different stimulio Tonic receptors – slow-adaptingo Three types (based on what they’re sensitive to): Extremes of temperature Mechanical damage Dissolved chemicalso Function to make one aware of damage to the body & seek medical treatment- Thermoreceptors: Temperature receptorso Free nerve endings located in the dermis, skeletal muscles, liver, and hypothalamuso Phasic receptors – very active when temperature is changing, but quickly adapt toa stable temperatureo Function to detect the temperature of our environment- Mechanoreceptors: Sensitive to stimuli that distort their plasma membraneso Contain mechanically-gated ion channels Gates open or close in response to:- Stretching- Compression- Twisting- Other distortions of membrane3BSC2086 Anatomy & Physiology II Exam #1 “You Should Be Able To”o Three (3) classes: Tactile receptors Baroreceptors Proprioceptorso Generally function to provide us information related to touch, pressure, and position Source of stimulation, shape, size, texture, movement Changes in pressure in an organ Position of joints, tension, and state of muscular contraction- Chemoreceptors: Chemical receptorso Respond only to water-soluble & lipid-soluble substances
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