Part 2: Dr. Steve I. Perlmutter

1
Sensorimotor Neurophysiology of Active Sensing
Part 2 Dr. Steve I. Perlmutter
Somatosensory System
Receptor Function Spinal Cord Circuitry
Proprioception
Touch
Temperature Pain
2
Signaling in the Nervous System Action Potential
Generation
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Ionic gradients generate a voltage across the
membranes of neurons membrane voltage is
regulated by ionic channels and pumps
4
The action potential is a brief, all-or-none
electrical depolarization of the neuron membrane
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The rate and timing of action potentials convey
information from one neuron to another.
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In primary sensory neurons, action potentials are
elicited by transduction of a sensory stimulus
into a receptor potential
Receptor potential
Spike generation
Spike conduction
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In mechanoreceptors, mechanical energy causes
ionic channels in the cells membrane to open,
leading to a change in membrane voltage, the
receptor potential
8
Touch receptors endings in the skin
Hair follicle Receptor (RA, SA)
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Touch acuity receptive field size of receptors
Meissner corpuscle
Merkel receptors
Ruffini corpuscle
Pacinian corpuscle
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Touch acuity receptor density
Meissner corpuscles
Merkel disk receptors
Johansson Valbo
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Touch acuity 2-point discrimination
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Temporal resolution of touch slowly vs. rapidly
adapting receptors
13
Meissner corpuscle
Merkel disk receptor
Ruffini ending
Torebjork Ochoa
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Touch sensitivity response to stimulus intensity
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Touch sensitivity frequency response of receptors
Activation Threshold
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Touch sensitivity receptor firing vs. perception
Monkey hand
Human psychophysics
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Primary sensory afferents enter the spinal cord
and project to 3 main targets
Axon branches to other CNS regions
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Information is transmitted from the primary
sensory afferent to other neurons in the CNS at
synapses.
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First main target for somatosensory information
is other neurons in the spinal cord