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39 Cards in this Set

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Sensory receptors
Referring to a specialized epithelial (in tissue detecting stimulus) or neural cell which transduces sensory stimuli. Applying term to cell itself, don't confuse with receptor proteins.
Referring to a specialized epithelial (in tissue detecting stimulus) or neural cell which transduces sensory stimuli. Applying term to cell itself, don't confuse with receptor proteins.
Afferent fibers
Fibers that send signals to the CNS
Efferent fibers
Fibers that send signals out from the CNS. Ex. motor neurons.
Classification of sensory receptors
Classified by the stimulus they detect.
Mechanoreceptors, photoreceptors, chemoreceptors, thermoreceptors, nociceptors.
Sensory transduction
Describes the process by which sensory receptors convert sensory/stimulus energy to membrane potentials, via ion channels.
Describes the process by which sensory receptors convert sensory/stimulus energy to membrane potentials, via ion channels.
How does sensory transduction happen?
Accomplished by sensory receptor ion channels which gate in response to the stimulus energy. These ion channels do not always DIRECTLY gate in response to stimuli, could be GPCR, etc.
Receptor potential
Describes the change in potential that occurs when a stimulus is transduced by a sensory receptor.
Sensory transmission to CNS
You don't always expect a receptor potential to result in transmission of a sensory signal to the CNS. Have to have a sufficient enough receptor potential created that would reach threshold level in order for an action potential to occur and trans...
You don't always expect a receptor potential to result in transmission of a sensory signal to the CNS. Have to have a sufficient enough receptor potential created that would reach threshold level in order for an action potential to occur and transmission to CNS to happen.
Sensory encoding
A way to have different receptors dedicated to different stimuli. Modality, location, intensity, duration.
Modality
Labeled lines. Using different nerve fibers to transmit different modalities to the brain (ex. neuron dedicated to vibration NOT pressure)
Location
Dedicated neurons, "neural maps", or areas of the brain dedicated to one kind of stimulus. Enhanced by lateral inhibition.
Intensity
Firing rate (frequency of action potentials), number of receptors activated (really strong pressure in the skin might activate more receptors), different types of receptors (pressure so intense that nociceptors become involved).
Duration
Duration of firing for the sensory receptor, when it starts you perceive, when it stops you know the stimulus is no longer there.
Sensory receptor adaptation
Two major categories; phasic or tonic receptors.
Phasic receptors
Encode onset and offset, adapt quickly by rapidly reducing the firing rate after a stimulus is applied, even if stimulus is continuing. Ex. Pacinian corpuscles detecting vibration (oscillating very quickly).
Encode onset and offset, adapt quickly by rapidly reducing the firing rate after a stimulus is applied, even if stimulus is continuing. Ex. Pacinian corpuscles detecting vibration (oscillating very quickly).
Tonic receptors
Encode intensity and duration, adapt slowly by reducing the firing rate only marginally as a stimulus is applied. Ex. Merkel's receptors detecting steady pressure.
Encode intensity and duration, adapt slowly by reducing the firing rate only marginally as a stimulus is applied. Ex. Merkel's receptors detecting steady pressure.
Receptive fields
Area of the body that, when stimulated, results in a change in firing rate or a sensory neuron. Small and large receptive fields.
Area of the body that, when stimulated, results in a change in firing rate or a sensory neuron. Small and large receptive fields.
First/Second...etc Order neurons
First-order neuron is the sensory receptor itself, synapses in a relay nucleus (in spine or brainstem) with second-order neurons.
Small receptive fields
One first order neuron synapses with one second order neuron. Allows advantage of discriminating location of sensation, ex. in fingertips and lips.
Large receptive fields
Many first order neurons synapse with one second order neuron. More conservative design, for areas where discrimination of location isn't so important, ex. skin on back.
Lateral inhibition
Enhances the ability to localize a stimulus, inhibitory receptive fields surround excitatory receptive fields. All converge on a common second-order neuron/afferent. The amount of 2nd order afferent firing depends on balance of excitatory vs. inhi...
Enhances the ability to localize a stimulus, inhibitory receptive fields surround excitatory receptive fields. All converge on a common second-order neuron/afferent. The amount of 2nd order afferent firing depends on balance of excitatory vs. inhibitory input.
Inhibitory interneuron
First order neuron in inhibitory field generates action potential but does not send it directly to the 2nd order, it sends it to an inhibitory interneuron. The inhibitory interneuron is depolarized, generates an action potential, releases inhibitory NT onto 2nd order, decreasing the likelihood of an action potential at the 2nd order neuron.
Mechanoreceptors
Touch sensation, most occur in dermal layer. Nerve endings often encapsulated. Pacinian corpuscles (vibrations), Meissner's corpuscles (2pt discrimination in fingertips), hair-follice receptors (velocity and direction of movement), Ruffini's corpuscles (skin stretch and joint rotation), Merkel's corpuscles (vertical indentations).
Thermoreceptors
Have free, unencapsulated nerve endings, have ion channels that detect temp changes. Two major classes; cold and warm with overlapping activity.
Have free, unencapsulated nerve endings, have ion channels that detect temp changes. Two major classes; cold and warm with overlapping activity.
Temp ranges
Around ~36 degrees that activity switches b/t the two, cold activity goes down, warm goes up.
If temp gets really high, warm receptors stop firing, but nociceptors start firing, that's why really hot temps are perceived as painful.
Around ~36 degrees that activity switches b/t the two, cold activity goes down, warm goes up.
If temp gets really high, warm receptors stop firing, but nociceptors start firing, that's why really hot temps are perceived as painful.
Transient receptor potential vanilloid receptors (TRPVs)
Ion channels that respond to varying stimuli, including temp.
TRPV 1 - responds to warm temp & vanilloid compounds (ex. capsacin in chili peppers)
Nociceptors
Have free nerve endings that respond to potentially damaging (noxious) stimuli. Different types; mechanical and polymodal.
Have free nerve endings that respond to potentially damaging (noxious) stimuli. Different types; mechanical and polymodal.
Mechanical nociceptors
Ex. a thorn, a needle stick. Sharp pain, fibers of medium diameter and have some myelination. Called A-delta fibers, very fast.
Polymodal nociceptors
Detect variety, mechanical, chemical, temp. Fibers are narrower and unmyelinated, called C fibers, are slower at transmitting action potentials. Associated with longer duration, throbbing pain.
Nociceptors and inflammation
When you have tissue damages, inflammatory substances are released that activate nociceptors, generate action potentials, causing pain.
When you have tissue damages, inflammatory substances are released that activate nociceptors, generate action potentials, causing pain.
Hyperalgesia
After inflammation, nociceptor fibers are more sensitive and normally non-painful stimuli can become painful.
Dorsal column pathway
Transmits discriminative touch, pressure, vibration, and proprioceptive information.
First-order afferent enters dorsal spine, ascends in the dorsal column, and synapses with second-order afferent in the medulla (nucleus gracilis or nucleus cunea...
Transmits discriminative touch, pressure, vibration, and proprioceptive information.
First-order afferent enters dorsal spine, ascends in the dorsal column, and synapses with second-order afferent in the medulla (nucleus gracilis or nucleus cuneatus). The second-order afferent crosses to the contralateral side, ascends, and synapses with a third-order neuron in the thalamus. The third-order afferent ascends and synapses with a fourth-order afferent in the somatosensory cortex.
Anterolateral pathway
Transmits pain, temperature, and light touch information.
First-order afferent enters dorsal spine and synapses with second-order afferent in the dorsal horn. The second-order afferent crosses to the contralateral side of the spine, ascends in th...
Transmits pain, temperature, and light touch information.
First-order afferent enters dorsal spine and synapses with second-order afferent in the dorsal horn. The second-order afferent crosses to the contralateral side of the spine, ascends in the anterolateral column, and synapses with a third-order neuron in the thalamus. The third-order afferent ascends and synapses with a fourth-order afferent in the somatosensory cortex.
Localizing a spinal lesion
If you cut all the fibers on the L side of the spine, pt will have reduced sensation of temp and pain on R side, but on ipsilateral side pt will have reduced sensation of 2pt discrimination, vibration, and proprioception. Work through picture.
If you cut all the fibers on the L side of the spine, pt will have reduced sensation of temp and pain on R side, but on ipsilateral side pt will have reduced sensation of 2pt discrimination, vibration, and proprioception. Work through picture.
Somatosensory cortex
Found just behind the central gyrus (postcentral gyrus), includes primary (S1), secondary (S2), and association areas.
Found just behind the central gyrus (postcentral gyrus), includes primary (S1), secondary (S2), and association areas.
Primary somatosensory cortex (S1)
Involved in direct perception of somatosensory stimuli. There is a disproportionate dedication of tissue to different areas of the body.
Secondary somatosensory cortex (S2)
Involved in processing of stimuli, more neural connectivity.
Association areas of cortex
Very high order processing, doing things like recognizing what is causing stimulus, etc.
Referred pain
Describes the sensation of pain on the body surface as a result of a noxious stimulus w/n an organ of the body. This occurs b/c a nociceptor innervating an organ may contact the same 2nd order afferent in the spine as a nociceptor innervating some...
Describes the sensation of pain on the body surface as a result of a noxious stimulus w/n an organ of the body. This occurs b/c a nociceptor innervating an organ may contact the same 2nd order afferent in the spine as a nociceptor innervating some location on the skin.