Lecture 14 Sensory Physiology Flashcards Preview

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Flashcards in Lecture 14 Sensory Physiology Deck (29):
1

Sensory receptors

-specialized cells that detect a specific type of stimulus
-sensory receptors are transducers that convert stimuli into changes in membrane potential

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Transducer

a device that converts variations in a physical quantity, such as pressure or brightness, into an electrical signal, or vice versa.

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Structural types of sensory receptors

free nerve endings
modified nerve ending
separate sensory receptor cells

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Sensitivity of sensory receptors

each sensory receptor has an adequate stimulus that it responds best to

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Functional classes of sensory receptors

responsive to particular sensory modalities
(chemoreceptors, mechanoreceptors, photoreceptors, thermoreceptors, nociceptors)

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Chemoreceptors

specific chemicals (taste, olfaction), pH, O2

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Mechanoreceptors

touch, pressure, stretch, vibration, sound, acceleration

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photoreceptors

light

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nociceptors

pain
noxious stimuli (chemical, mechanical, thermal)
*noxious is harmful, poisonous or unpleasant

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Sensory transduction

sensory receptors produce graded receptor potentials in response to sensory stimuli
sensory neurons convert receptor potentials into streams of action potentials.

Stimulus -> sensory receptor(receptor potential) -> sensory neuron(action potentials) -> CNS

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receptive field

area supplied by one sensory neuron

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two point discrimination test

smaller receptive fields result in more sensitive discrimination

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Afferent Division of PNS

Conveys APs from sensory neurons to the CNS
(somatic sensory, visceral sensory, special senses)

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Somatic Sensory

touch, temperature, pain, proprioception (general sesnes)

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Visceral Sensory

Mechanical and chemical stimuli from internal organs

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special senses

vision, hearing, equilibrium, olfaction, taste

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Sensory pathways in the CNS

ascending tracts in the spinal cord (somatic senses)
1st order neurons, second order neurons, third order neurons.
Cranial nerve sensory pathways

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First order sensory neurons

from receptors to spinal cord or brainstem

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second order neurons

from spinal cord or brainstem to thalamus

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third order neurons

from thalamus to cerebral cortex

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Sensory areas of the cerebral cortex

somatosensory cortex - parietal lobe
visual cortex - occipital lobe
auditory cortex - temporal lobe

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CNS integration of sensory information
Properties of stimuli

modality, location, intensity, duration

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Modality of stimulus indicated by

specificity of receptors and sensory neurons activated
specific neural pathways in the CNS -> specific areas in the brain ("labeled line coding")

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Location of stimulus

specific neural pathways connect receptive fields to specific locations in the cortex
sound localization uses differences in timing form R and L ears
lateral inhibition- increases contrast between adjacent receptive fields

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Intensity of stimulus encoded by

number of receptors activated
frequency of action potentials in sensory neurons

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Duration of stimulus

coded by duration of APs

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Receptor Adaptation

decreases in response to a persistent stimulus over time
Tonic receptors and Phasic receptors

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Tonic Receptors

non-adapting or slowly adapting
fairly constant response to sustained stimulus
e.g. muscle spindle stretch receptors

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Phasic receptors

rapidly adapting
respond to initial change in stimulus, then decrease response
e.g. olfactory receptors