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Unformatted text preview: Neurophysiology Unit 1 Study Guide Ÿ Transduction: stimulus is changed into and electrical signal Ÿ different types of stimuli Ÿ mechanical deformation Ÿ chemical Ÿ change in temperature Ÿ electromagnetic Ÿ Sensory Systems: mediate 4 attributes of a stimulus no matter what type of sensation Ÿ modality (type of sensation) Ÿ location Ÿ intensity Ÿ timing Ÿ some receptors are specific or can detect different stimuli Ÿ same mechanism for general and special senses Ÿ Receptor Potential: membrane potential of the receptor Ÿ change in the receptor potential is associated with opening of ion channels (Na+) Ÿ above threshold as the receptor potential becomes less negative the frequency of AP into the CNS increases Ÿ Labeled Line Principle: Ÿ different modalities of sensation depend on the termination point in the CNS Ÿ type of sensation felt when a nerve fiber is stimulated is determined by termination point in the CNS Ÿ labeled line principle refers to the specificity of nerve fibers transmitting only one modality of sensation Ÿ Adaptation: Ÿ SLOW à provide continuous information (tonic) Ÿ Relatively non-adapting Ÿ Respond to sustained stimulus Ÿ Do not lose sensation even after time - sensation may decrease Ÿ Location: Ÿ Joint capsule Ÿ Muscle spindle Ÿ Merkel’s discs - punctuate receptive fields Ÿ Ruffini end organ’s (corpuscles) - activated by stretching the skin Ÿ FAST à phasic Ÿ React strongly when a change is taking place Ÿ Respond to vibration Ÿ Lose sensation - only get sensation when stimulus is applied and removed Ÿ Location: Ÿ Hair receptors Ÿ Pacinian corpuscles (250 Hz - optimum stimulation rate) Ÿ Meissner’s corpuscles (30-40 Hz) Ÿ Sensory Innervation of Spinal Joints: Ÿ tremendous amounts of innervation with cervical joints the most heavily innervated Ÿ size relationship is proportional to speed (1 micron diameter = 1 m/s à unmyelinated) Ÿ with myelination - speed in increased 6x Ÿ four types of sensory receptors à Ÿ Type I Mechanoreceptors: Ÿ Outer layers of joint capsule Ÿ Fire at a degree proportional to joint movement or traction Ÿ Low threshold Ÿ Dynamic-fire with movement Ÿ Slow adapting Ÿ Tonic effects on lower motor neuron pools Ÿ Largest Ÿ Myelinated Ÿ Type II Mechanoreceptors: Ÿ Deeper layers of joint capsule Ÿ Low threshold Ÿ Rapidly adapting Ÿ Completely inactive in immobilized joints Ÿ Functions in joint movement monitoring à decreased proprioception Ÿ Phasic effects on lower motor neuron pools Ÿ Myelinated Ÿ Smaller than type I Ÿ Type III Mechanoreceptors: Ÿ Recently found in spinal joints Ÿ Very high threshold Ÿ Slow adaptation (similar to type I)...
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This note was uploaded on 04/07/2008 for the course NEUROPHYS 201 taught by Professor F during the Spring '08 term at Palmer Chiropractic.
- Spring '08