BMD 310: SOMANTIC NERVOUS SYSTEM
34 Cards in this Set
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For a sensation to occur 4 things must happen...
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–A stimulus must occur
–A sensory receptor must change the stimulus into an impulse
–The impulse must be conducted along a pathway (sensory receptor to the brain)
–The brain must receive the impulse and integrate the information to produce a sensation
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Stimulus can be...
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–Light
–Heat
–Mechanical energy
–Chemical energy
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Perception is
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–Conscious interpretation of a sensation
–Integrated within the cerebral cortex
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Each sensory neuron can only carry
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one specific type of modality
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Sensory modality
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–Each unique type of sensation
•Touch, pain, vision, hearing
–Sensory neurons carry information for only ONE type of modality
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Adaptation
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–A decrease in sensation during prolonged stimulus
–Perception decreases or disappears
–Can you think of any examples?
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Somatic Senses
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•Tactile
–touch, pressure, vibration, itch, tickle
•Thermal
–Warm, cold
•Pain
•Proprioception
Static positioning and movements of the limbs and head
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Visceral Senses
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•Information regarding conditions of the internal organs
–Pressure, stretch, chemicals, nausea, hunger and temperature
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General Senses (two types)
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Somatic and Visceral
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Special Senses
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–Smell, taste, vision, hearing, equilibrium
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Sensory Receptors can be defined by...
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1. Location of receptor or origin of stimuli
2. Structure
3. Types of stimulus
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location or origin
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–Exteroceptors
•Near or at external body surface
–Interoceptors
•In blood vessels, visceral organs and muscles
–Proprioceptors
•In muscles, tendons, joints and inner ear
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defined by structure
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–Free nerve endings
–Encapsulated nerve endings
–Separate cells
•Synapse with sensory neurons
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Touch sensations
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–Fine: provides specific information about a touch
•Meissner corpuscles
–Dermal papillae of hairless skin
–Crude: ability to perceive something has touched the skin, but is not specific
•Hair root plexuses: rapidly adapting
–Slow adapting receptors
•Type I cutaneous mechanoreceptors…
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defined by stimulus type
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–Photoreceptors
•Detects light
–Mechanoreceptors
•Sensitive to touch or pressure
–Thermoreceptors
•Changes in temperature
–Osmoreceptors
•Osmotic pressure of body fluids
–Chemoreceptors
•Chemical detection
–Nociceptors
•Painful stimuli from chemical or physical tissue damage
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Pressure and Vibration Sensation
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–Pressure is sustained sensation over a large area and occurs in deeper tissues
–Pacinian corpusles adapt rapidly, are widely dispursed throughout the body
–Corpuscles of touch and pacinian corpusles related feelings of vibration
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tactile sensations
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–Touch, pressure, vibration, itch and tickle
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Itch and tickle sensations
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–Free nerve endings mediate the sensation of both itch and tickle
–You cannot tickle yourself due to integrate with signals from the cerebellum
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Vibration terms to know
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Corpuscles of touch=lower frequency vibrations
Pacinian (lamellated) corpuscles= higher frequency vibrations
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Pain Sensations
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–IMPORTANT for survival!
–Protects us be letting us know of noxious substances/conditions which can damage tissue
–Nocioceptors are EVERYWHERE except in the brain
–Types of pain
•Fast: occurs within 0.1 second after stimulus
–ACUTE
•Slow: occurs >1 second after stimulus and graduall…
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Did you know?
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You cannot tickle yourself. Due to intefrate with signals from the cerebellum.
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Thermal Sensations
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–Thermoreceptors
•Cold: located in stratum basale of the epidermis
–Activated at 50-105 degrees Fahrenheit
–Adapt rapidly
•Warm: located in the dermis
–Activated at 90-118 degrees Fahrenheit
–Adapt rapidly
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Did you know?
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temps less than 50 degrees are perceived as pain not cold.
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•Kinesthesia
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–Perception of body movements
–Proprioceptors are embedded in our muscles and tendons to relay information regarding contraction, the amount of tension and joint position.
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•Types of Proprioceptors
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1. Muscle Spindles
2. Tendon Organs
3. Joint kinesthetic receptors.
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Muscle Spindles
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•Monitors changes in muscle length (main function)
–Also contains motor neurons called gamma motor neurons which adjust tension
–Also alpha motor neurons which innervate extrafusal motor fibers
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Tendon organs
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•Located at junction of the muscle and the tendon
•Protects from damage due to excessive muscle tension
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Joint kinesthetic receptors
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•Within the synovial joints
•Free nerve endings and Ruffini corpuscles which respond to pressure
•Pacinian corpuscles are within the surrounding connective tissue which respond to acceleration and deceleration of the joint
•There are also receptors similar to tendon organs which adjust…
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Spinothalamic Sensation is responsible for...
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–Pain
–Temperature
–Tickle
–Crude touch
–Pressure
–Vibration
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Proprioception
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Recognition of self.
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Somatic Sensory Pathways
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See slide and figure 21.4 in textbook.
*know dorsal column-medial lemniscal pathway vs spinothalamic tract.
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Dorsal Column-Medial Lemniscus is responsible for...
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–Fine touch
–Stereognosis
•Ability to recognize the size, shape and texture of an object by feeling
–Proprioception
•Including weight discrimination
–Vibratory sensation
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Somatic Motor Pathways
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See slide and Figure 21.6 in textbook.
*know the two different motor pathways.
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Homunculus
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Figure 21.5 in textbook
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BMD 310: SOMANTIC NERVOUS SYSTEM