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Midterm

PSL300H1 Study Guide - Midterm Guide: Stimulus Modality, Nociception, Somatosensory System

by

Department
Physiology
Course Code
PSL300H1
Professor
Doug Mac Kay
Study Guide
Midterm

Page:
of 2
SPECIAL AND SOMATIC SENSES
5 special senses: vision, hearing, equilibrium, taste and smell
4 somatic sense: touch, temperature, proprioception and nocioception
unconscious to visceral data: blood pressure, blood-glucose concentration, internal
body temp.
Receptors and Neurons
every sensory system begins w/ receptors: cells, not necessarily neurons, convert
stimulus energy into electrical signals. transduction
receptor convert stimulus E. if receptor = neuron, then fires AP. if not neuron = can
release NT to excite neuron.
***each receptor adequate stimulus: form of E to which it's most responsive. but
can also respond to other sensory modalities.***
receptors classed according to adequate stimuli:
receptor response
chemoreceptors chemical ligands. monitor lvls of O, pH and organic molecules
(glucose)
mechanoreceptors mechanical E: pressure, vibration, gravity, acceleration, sound
thermoreceptors temperature
photoreceptors light
simple receptors: neurons w/ free nerve endings. sense temp. + noxiouos stimuli.
myelinated or unmyelinated axons.
complex neural receptors: neurons w/ endings in many layer connective tissue
envelope. when pressure applied capsule compressed inside of capsule
activated.
most special sense receptors = cells that release NT onto sensory neurons.
stimulus specialized cell (ex. hair cell) synapses on nerve responds and
releases NT
transduction involves ion channels on receptor's membrane:
stim opens/closes ion channels directly/via second messenger. usually channel
opened Na+ or other cation enters into cell depolarization. some cases K+
leaves cell hyperpolarization. in vision light closes cation channels =
hyperpolarization.
threshold for every receptor. minimal stimulus that activates it producing AP.
some photoreceptors activated by a single photon. chemoreceptors activated by
single odurant. perceptual threshold: minimal stimulus that will make you aware of a
sensation. depends on attention.
sensory systems involve series of neurons: first neuron = primary (first order)
sensory neuron synapse onto secondary sensory neurons tertiary sensory
neurons. etc...
at each stage presynaptic neurons = input to one or few postsynaptic neurons
convergence, allowing secondary, tertiary and higher neurons to combine info from
many receptors.
stimulus modality: sensory systems indicate modality by labeled lines (ex. activity on
neurons in visual pathway in interpreted by CNS to mean light)
somatic senses
special senses
transduction
adequate stimulus
chemoreceptors
mechanoreceptors
thermoreceptors
photoreceptors
simple receptors
complex neural receptors
threshold
perceptual threshold
primary sensory neuron
(first order)
secondary sensory neuron
(second order)
tertiary sensory neuron
convergence
stimulus modality
labeled lines
INTRO TO SENSES
May-25-135:40 PM