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Chp. 8 General Principles of Sensory Processing, Touch, and Pain

Terms in this set (36)

Basic principles of Sensory Processing
touch and pain
Sensory receptor organs
are organs specialized to detect a certain stimulus.
Receptor cells
within the organ convert the stimulus into an electrical signal. Receptor organs are very diverse.
adequate stimulus
is the type of stimulus to which a sensory organ is particularly adapted.
touch
many sensations blended together; skin is a complex organ that contains a variety of sensory receptors
dorsal column system
carries somatosensory information from the skin to the brain
Sensory transduction
The conversion of electrical energy from a stimulus into a change in membrane potential in a receptor cell.
Receptor potentials
(or generator potentials) are local changes in membrane potential.
Skin has three separate layers:
Epidermis—outermost layer; thinnest

Dermis—middle layer; contains nerve fibers

Hypodermis—innermost layer; anchors muscles and helps shape body
epidermis
outermost layer of skin; thinnest
dermis
middle layer; contains nerve fibers
hypodermis
inntermost layer; anchors muscles and helps shape body
Four tactile receptors detect touch:
Pacinian corpuscles—vibration, fast-adapting
Meissner's corpuscles—touch, fast-adapting
Merkel's discs—touch, slow-adapting
Ruffini's endings—stretch, slow-adapting
Pacinian corpuscles
vibration, fast-adapting. A stimulus to the corpuscle produces a graded electrical potential.
When the potential is big enough, the receptor reaches threshold and generates an action potential.
.
Meissner's corpuscles
touch, fast-adapting
Merkel's discs
touch, slow-adapting
Ruffini's endings
stretch, slow-adapting
The Structure and Function of the Pacinian Corpuscle
1) Mechanical stimulation deforms the corpuscle
2) Deformation of the corpuscle stretches the tip of the axon
3) Stretching the axon open mechanically gated ions cannels in the membrane allowing + charged ions to enter
4) The receptor potential reaches threshold amplitude
5) Action potential
Coding
Patterns of electrical activity in the sensory system convey information about the original stimulus.
A single neuron can convey stimulus intensity
by changing the frequency of its action potentials.
Multiple neurons can act in parallel
as the stimulus strengthens, more neurons are recruited.
Range fractionation
takes place when different cells have different thresholds for firing, over a range of stimulus intensities.
The somatosensory system
detects body sensations, including touch and pain.
Spatial properties of the stimulus
Tonic receptors
show slow or no decline in action potential frequency.
Adaptation:
The progressive loss of response to a maintained stimulus.
Phasic receptors
display adaptation and decrease frequency of action potentials
The dorsal column system
delivers touch information to the brain.
dermatome
a strip of skin innervated by a particular spinal nerve.
Each sensory system has a distinct
sensory pathway in the brain and passes through stations during processing.
Most sensory pathways pass through regions of the
thalamus and terminate in the cerebral cortex
receptive field
field is the space in which a stimulus will alter a neuron's firing rate. It defines the perception threshold. Receptive fields differ in size, shape, and response to types of stimulation.
Receptive fields in the cortex S1 and S2:
A separate primary sensory cortex exists for each modality.

Secondary sensory cortex, or nonprimary sensory cortex, receives its main input from the primary cortical area for that modality.
A separate primary sensory cortex
exists for each modality
Secondary sensory cortex, or nonprimary sensory cortex
receives its main input from the primary cortical area for that modality.
Attention
is a state, or condition, of selective awareness or perceptual receptivity, by which specific stimuli are selected for enhanced processing. It may also be the process that allows selection of some inputs over others
Certain brain regions are important in attention.
Posterior parietal
Cingulate cortex
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