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Unformatted text preview: Neurophysiology Unit 1 Study Guide Transduction: stimulus is changed into and electrical signal different types of stimuli mechanical deformation chemical change in temperature electromagnetic Sensory Systems: mediate 4 attributes of a stimulus no matter what type of sensation modality (type of sensation) location intensity timing some receptors are specific or can detect different stimuli same mechanism for general and special senses Receptor Potential: membrane potential of the receptor change in the receptor potential is associated with opening of ion channels (Na+) above threshold as the receptor potential becomes less negative the frequency of AP into the CNS increases Labeled Line Principle: different modalities of sensation depend on the termination point in the CNS type of sensation felt when a nerve fiber is stimulated is determined by termination point in the CNS labeled line principle refers to the specificity of nerve fibers transmitting only one modality of sensation Adaptation: SLOW provide continuous information (tonic) Relatively non-adapting Respond to sustained stimulus Do not lose sensation even after time - sensation may decrease Location: Joint capsule Muscle spindle Merkels discs - punctuate receptive fields Ruffini end organs (corpuscles) - activated by stretching the skin FAST phasic React strongly when a change is taking place Respond to vibration Lose sensation - only get sensation when stimulus is applied and removed Location: Hair receptors Pacinian corpuscles (250 Hz - optimum stimulation rate) Meissners corpuscles (30-40 Hz) Sensory Innervation of Spinal Joints: tremendous amounts of innervation with cervical joints the most heavily innervated size relationship is proportional to speed (1 micron diameter = 1 m/s unmyelinated) with myelination - speed in increased 6x four types of sensory receptors Type I Mechanoreceptors: Outer layers of joint capsule Fire at a degree proportional to joint movement or traction Low threshold Dynamic-fire with movement Slow adapting Tonic effects on lower motor neuron pools Largest Myelinated Type II Mechanoreceptors: Deeper layers of joint capsule Low threshold Rapidly adapting Completely inactive in immobilized joints Functions in joint movement monitoring decreased proprioception Phasic effects on lower motor neuron pools Myelinated Smaller than type I Type III Mechanoreceptors: Recently found in spinal joints Very high threshold Slow adaptation (similar to type I)...
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- Spring '08