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Change environmental info into AP's - the common language of NS.
Transduce
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Each type of receptor responds to a particular...
- Modality.
- (form of info, eg, sound, light, pressure)
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Different modalities perceived as different because...
CNS pathways they stimulate.
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Can be simple dendritic endings of neurons.
Specialized endings of neurons or.
Non-neuronal cells.
Categories of Sensory Receptors
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Sense Chemical stimuli.
Chemo receptors.
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transduce light.
Photo receptors.
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Respond to temperature changes.
Thermo Receptors.
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Respond to deformation of their cell membrane.
Mechano Receptors.
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Respond to intense stimuli by signaling pain.
Nociceptors.
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Signal position info of body parts In muscles tendons joints.
Proprioceptors.
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Receptors are in the skin, respond to touch, pressure, temperature or pain.
Cutaneous Receptors
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Are part of a sensory organ, such as hearing, sight, equilibrium, taste, smell
Special Sense.
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Respond at constant rate as long as stimulus is applied (ex pain)
Tonic Receptors
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Respond with burst of activity but quickly reduce firing rate to constant stimulation - Adaptation ex smell, touch
Phasic Receptors.
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Stimulation of sensory fiber evokes only the sensation of its modality.
Law of Specific Nerve Energies
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Normal Stimulus is...
Adequate stimulus.
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Requires least energy to activate its receptor
Adequate stimulus.
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Like an EPSP (are sensory receptors)
Generator (receptor) Potential - graded.
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Produced in response to adequate stimulus.
Generator (receptor) Potential - graded.
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After threshold is reached AP frequency is proportional to amplitude of ...
- Generator potential.
- Proportional to stimulus intensity.
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Includes Touch, Pressure, Hot, Cold, Pair.
Cutaneous Sensations.
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Mediated by free and encapsulated nerve endings.
Cutaneous sensations.
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Pain mediated by
Nociceptors.
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Substance P called...
Pain NT.
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Heat elicits pain thru....
Capsaicin receptors.
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Is "hot" chemical in chili peppers.
Capsaicin.
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Cutaneous receptors include:
- free Nerve endings.
- ruffini endings.
- Merkel's disc.
- Meisner's.
- Pacinian corpuscles.
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Include sensations from cutaneous and proprioceptors.
Neural Pathways for Somastesthetic Sensations.
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A 3-neuron pathway carries info to ....
Cerebral Cortex.
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From sensory receptor to spinal cord/medula
1st order neurons.
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From spinal cord, medula to Thalmus.
2nd order Neurons.
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From Thalamus to sensory cortex (post central gyrus)
3rd Order Neurons.
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Pain felt in somatic locations resulting from damage to an internal organ.
Referred Pain.
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Angina Pectoris - Myocardial infarction - Left arm pain.
Example of Referred Pain.
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Results from two 1st order neurons synapsing on a common 2nd order neuron.
Referred Pain
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Sensory regions served by a particular spinal nerve.
Dermatomes.
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The area of skin whose stimulation results in changes in firing rate of a sensory neuron.
Receptive fields
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Area varies inversely with density of receptors
- Receptive Fields.
- Back of legs have low density of sensory receptors and receptive field are large.
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Minimum distance at which 2 points of touch can be perceived as seperate.
Two-point Touch Threshold
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Measure of ? or distance between receptive fields.
Tactile acuity.
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The CNS process that sharpens sensation.
Lateral Inhibition.
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Sensory neurons at center of stimulation area inhibit....
More lateral neurons.
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Taste (gustatory) receptors
Taste Buds
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Innervated by Cranial Nerves VII and IX.
Taste Buds.
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Detects sweet, sour, salty, bitter, savory (umami)
Taste
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50-100 ? in each taste bud.
Taste Receptor cells (chemoreceptors)
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Each bud can respond to ...
All categories of tastes.
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Located in olfactory epithelium at top of nose.
Olfactory chemoreceptors.
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Innervated by CN I
Smell (olfation)
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Orientation to gravity.
Equilibrium.
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Vestibular apparatus consists of
Otolith organs.
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Otolith organs
- Utricle, saccule, semicircular canals.
- Cranial Nerve VIII
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Sensory structures located within
Membranous Labyrinth
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Membranous Labyrinth filled with...
Endolymph and located within bony labyrinth.
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Detect Linear Acceleration.
Utricle and saccle
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Oriented in 3 planes, detect angular acceleration.
Semicircular Canals.
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Receptors for equilibrium
Hair Cells
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Contain 20-50 hairlike extensions
Sereocilia.
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