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16 Cards in this Set

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Each somatosensory pathway consists of what three neurons?
PRIMARY SENSORY NEURON - Ganglion Cell

SECONDARY SENSORY NEURON - Projection Cell

TERTIARY SENSORY NEURON - Thalamic Cell
Each neuron of the somatosensory pathway contains what?
Receptive field
Describe the ganglion cell neuron.
Unipolar with a receptor
Describe the projection cell neuron.
Axon decussates (projects from one side of CNS to the other side)
Describe the thalamic cell neuron.
Projects to the sensory cortex
Define receptive field.
Area of skin, when stimulated, either increases or decreases the firing rate of that cell.
Each receptive field has what two regions?
Excitatory center

Inhibitory surround
What two components create the properties of lateral inhibition?
Excitatory center

Inhibitory surround
What does lateral inhibition increase?
The signal to noise ratio, thus enhancing contrast between stimulated and unstimulated areas.
Describe the size of receptive fields on various parts of the body.
The larger receptive fields tend to be proximal, while the smaller receptive fields are more distal.
Describe the innervation density on various parts of the body.
The innervation density is proportional to the receptive field. Thus, greater innervation density is seen distally, while the lesser innervation density is seen proximally.
Define receptors.
Sensory terminal whose membrane responds to a stimulus by producing a local, graded, usually depolarizing potential (increased Na+ & K+ conductance)
Action potentials are initiated by what?
Threshold Receptor Potential
For each receptor there is a unique what?
Adequate stimulus

which will cause the receptor membrane to be depolarized.
T/F - Adequate stimulus is the same for each type of receptor.
False - Adequate stimulus is different for each type of receptor.
What does the fact that each type of receptor has a different adequate stimulus mean?
Implies that each receptor makes a unique contribution to somatic sensation.