Introduction
There are four types of mechanoreceptors in the somatosensory system—receptors that respond to mechanical stimulation or pressure. Because the receptor types are named after their discoverers rather than their functional roles, it can be difficult to remember which is which. This activity is designed to help you review the functional characteristics of the four mechanoreceptor populations and learn their names.
Activity Description
The user can click on the receptors or their label names in the diagram to see their characteristics listed. Below, we list all of the parts from the diagram, along with their descriptions.
Skin Layers, From Outer to Inner
Epidermis
The epidermis is the outermost layer of your skin. Meissner and Merkel receptors are embedded in the junction between the epidermis and the deeper dermis. Note that these two types of receptors have the smallest receptive fields.
Dermis
The dermis is the middle of the three layers of skin in this figure, located between the epidermis and the subcutis. Meissner and Merkel receptors are embedded in the junction between the dermis and epidermis, and Ruffini receptors are located deeper in the dermis.
Subcutis
The subcutis (“under the skin”) is the layer of tissue just below the dermal and epidermal skin layers. Pacinian corpuscles, the largest of the touch receptor types, are located in this tissue layer, just below the dermis.
Mechanoreceptors
Meissner Receptors
Meissner receptors (also called Meissner’s corpuscles) have the following characteristics:
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They have small receptive fields.
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They have a fast adaptation rate.
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They respond to low-frequency vibrations.
If you are holding a coffee cup and it starts to slip from your fingers, the motion across your skin will cause low-frequency vibrations that will activate Meissner receptors.
Merkel Receptors
Merkel receptors (also called Merkel disks or Merkel cell neurite complexes) have the following characteristics:
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They have small receptive fields.
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They have a slow adaptation rate.
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They respond to fine spatial details.
If you are trying to drive a screw in a location you can reach but cannot see, Merkel receptors will be essential for the task. They are the receptors that let you feel the top of the screw so that you can determine the orientation of the slot.
Ruffini Receptors
Ruffini receptors (also called Ruffini endings) have the following characteristics:
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They have large receptive fields.
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They have a slow adaptation rate.
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They respond to sustained downward pressure and skin stretching.
If you wear glasses and grope for them in the morning before opening your eyes, your Ruffini receptors will help you determine if your fingers are in the right position to pick them up.
Pacinian Receptors
Pacinian receptors (also called Pacinian corpuscles) have the following characteristics:
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They have large receptive fields.
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They have a fast adaptation rate.
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They respond to high-frequency vibrations and initial skin contact.
When a mosquito lands on your arm, you feel it because your Pacinian receptors register the vibration of the wings and the slight increase in pressure the insect makes when it lands.