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.

Instructions

Click on the receptors or their label names in the diagram at left to see their characteristics listed here. You can also click on the three skin layers (located via the brackets on the right side of the image) to learn their names and characteristics.

You can click the “Show Labels” link to reveal the names of the receptors and skin layers.

Click the “Start Quiz” link when you are ready to test yourself on the receptor types and functions.

Meissner Receptors

Meissner receptors (also called Meissner’s corpuscles) have the following characteristics:

• They have small receptive fields.
• They have a fast adaptation rate.
• 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:

• They have small receptive fields.
• They have a slow adaptation rate.
• 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.

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.

Ruffini Receptors

Ruffini receptors (also called Ruffini endings) have the following characteristics:

• They have large receptive fields.
• They have a slow adaptation rate.
• 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.

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.

Pacinian Receptors

Pacinian receptors (also called Pacinian corpuscles) have the following characteristics:

• They have large receptive fields.
• They have a fast adaptation rate.
• 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.

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.

You are now starting the quiz. You will have to click on each receptor type three times during the course of the quiz. (For skin layers, click on the brackets on the right side of the figure.)