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NPB 112 11 somato - NPB 112 Winter 2011 1/18 Outline I Sensory physiology overview(Ch 9 II Skin mechanoreceptor types A Mechanoreceptor B

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1 NPB 112, Winter 2011: 1/18- 1/20/11 Outline: I. Sensory physiology: overview (Ch. 9) II. Skin mechanoreceptor types A. Mechanoreceptor B. Thermoreceptors (Ch. 10) 1. Warm receptors 2. Cold receptors C. Nociceptors (pain) 1. A-delta mechanical nociceptor 2. polymodal nociceptor RECEPTOR : specialized neuron or epithelial cell that responds to a specific type or wavelength of environmental energy (process by which environmental energy is transformed by receptor into an electrical signal) ADEQUATE (or appropriate) STIMULUS : type of stimulus energy that activates receptor at the lowest relative intensity
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2 Sensory Modality Quality (sub-modality) vision color, motion hearing pitch smell > 20 odors (950 genes, 400 functional receptors) taste sweet, sour, salt, bitter, "umami" (MSG, other amino acids) somatic touch-pressure warm-cold flutter-vibration pain, itch, tingle, tickle , pleasurable touch? position and movement senses Aristotelian Senses Sensory systems signal what, where, when, and how much stimulation occurs •Wh a t (modality): accomplished by labeled line (specificity) or some kind of population coding e r e : topographic map in sensory cortex •How mu ch : population and rate coding en (duration): rate of adaptation to stimulus
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3 WHAT? Johannes Mueller (1826): “law of specific nerve energies” Modality is property of sensory nerve fiber • nerve fiber is activated primarily by a certain type of stimulus energy, and makes specific connections to structures in the brain whose activity gives rise to a specific sensation • Modality is encoded by “labeled line” – Receptor’s afferent fiber is modality-specific line of communication – Activation of sensory neuron naturally or electrically elicits the same sensation – Modality is represented by sensory system , an ensemble of neurons connected to specific receptor class – Submodalities (qualities): can divide modality into constituent qualities based on sensitivity of receptors to specific bandwidths of energy (e.g., somatosensory includes touch, pressure, vibration, pain, itch, temperature, etc.) Some terminology • RECEPTOR: specialized neuron or epithelial cell that responds to a specific type or wavelength of environmental energy • RECEPTIVE FIELD: region on body surface, or area in visual and auditory space, within which an appropriate stimulus activates the receptor (or changes the firing rate of neurons along the sensory pathway) • STIMULUS TRANSDUCTION: process by which environmental energy is transformed by receptor into an electrical signal • ADEQUATE (or appropriate) STIMULUS: type of stimulus energy that activates receptor at the lowest relative intensity • RECEPTOR POTENTIAL (or generator potential): change in receptor membrane potential elicited by appropriate stimulus • THRESHOLD: lowest stimulus intensity evoking a measurable change in receptor membrane potential (or perceived on >50% of trials of repeated stimuli)
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4 Cool: TRPM8 Intense cold: TRPA1 Heat: TRPV1 (VR-1) (From Julius & Basbaum, Nature, 2001) Acid-sensing ion channel
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NPB 112 11 somato - NPB 112 Winter 2011 1/18 Outline I Sensory physiology overview(Ch 9 II Skin mechanoreceptor types A Mechanoreceptor B

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