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30 Cards in this Set
- Front
- Back
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Cause of Leprosy
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bacteria infects the Schwann cells; armadillos get it too
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Symptoms of Leprosy
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continuous injuries, infections, etc.
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Shingles
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section of the skin that has a burning or stabbing pain, hypersensitivity, inflamed and blistered skin, and a scaly appearance; common on only one section (left arm, right leg)
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Cause of Shingles
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chicken pox virus
- virus gets into dorsal root ganglion neurons and lies dormant until activation |
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Shingles Reduction Cause
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vaccine proves much more effective than the natural way
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Phantom Limbs
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perception that the limb is still there and it hurts
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Cause of Phantom Limbs
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Neuroma: nerves will try to grow back, but there are no previous innervation sites so they become balled up and intertwined
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W. Haber and W. Teuber
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independently observed that soldiers were more likely to feel the pain
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Telescoping
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The phantom hand would stay the same size, but the phantom arm would shrink
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Three Basic Types of Somatosensations
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1) Touch and pressure on the skin
2) Pain and temperature 3) Limb orientation and posture <-- unimportant |
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Proprioception
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people fall down a lot
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Mechanoreceptors
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several classes of touch and pressure receptors that lie just under the skin and are activated by different types of mechanical energy; bending hair reaction
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Slowly-Adapting (SA) receptors
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respond best to pressure and will fire more action potentials with increasing pressure on the skin
pressure > rate of stimulus |
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Receptive Field
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energy required to change the activity of a neuron
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Rapidly-Acting (RA) receptors
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respond to transients in pressure, and will respond to the onset and offset of pressure to the skin; phase lock stimuli in the range of 5-50 Hz
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Pacinian/Vibratory receptors
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respond best to very high frequencies and will phase lock to stimuli in the range of 50-300 Hz, but have been observed at 1000 Hz
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Phase-Locking
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A neuron fires off an action potential at the same point (or close enough) of each stimulus cycle
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Peri-Stimulus Time Histogram (PSTH)
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common way of showing how a neuron responds by action potentials
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No Phase-Lock
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no regular structure from one stimulus to the next
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Flat PSTH
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SA neurons: stimuli greater than 5 Hz
RA neurons: mid-frequency ranges PC neurons: higher frequency ranges |
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Irregular Stimuli Phase-Locking
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SA: smooth
RA: rough PC: roughest/finely textured |
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Stretch-Activated Channels
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Pressure causes distortion of the end of the neuron which opens the stretch channels; this lets anything (Na+, K+, Ca++) cross the membrane
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Primary Somatosensory Cortex (SI)
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Large, myelinated axons make synapses in here and this causes projection of their axons across the midline to neurons in the lateral portion of the ventrobasal thalamus; thalamic nuclei project up into layers IV and VI
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Trigeminal System
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Trigeminal nerve, cranial nerve V, project to principle sensory trigeminal nucleus; those neurons cross the midline and project to the medial VBT
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IMPORTANT: Dorsal Root Ganglion Cells
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do not send their axon to just one dorsal column nucleus cell, rather every single dorsal root ganglion cell will make synapses with hundreds of dorsal column nuclei
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Divergence
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One neuron provides input to many post-synaptic neurons
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Convergence
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Many neurons converge and provide input onto a single post-synaptic neuron
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Somatotopy
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neurons with similar receptive fields are located next to each other; those with much different receptive fields are located farther away; gives rise a homunculus in the primary somatosensory cortex
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Owl Monkey Finger Amputation Expectations
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1) large "quiet zone" formerly represented the missing digit
2) neurons in the zone formerly representing the missing digit now respond to something else 3) A little of both |
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Owl Monkey Observation
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receptive fields of the neurons overlapped
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