Pacinian corpuscles are receptors in your skin that respond to touch. They're part of a group called mechanoreceptors. Mechanoreceptors are like sensors that change physical pressure into electrical signals that your brain understands. Pacinian corpuscles only respond to physical pressure, like when you step down on your foot. They work by creating a generator potential, which is like an electrical signal that travels through your nerves. This signal can vary in strength, unlike an action potential which is always the same. Pacinian corpuscles are really important for helping you feel things!

An overview of receptors

Let's talk about receptors before diving into Pacinian corpuscles. Receptors are like messengers that receive information from different parts of our body. They can detect changes in the environment, like a drop in temperature, or changes inside our body, like hunger. This is called sensory reception. The brain then processes this information, which is called sensory perception. Receptors are crucial because they help us adjust to the world around us. They're special proteins in our body that receive signals. For example, when you touch a piece of paper, the Pacinian corpuscles in your skin detect the pressure of the paper on your fingertip. This sends a signal to your brain, which lets you feel the paper.

Where is the Pacinian corpuscle located?

Pacinian corpuscles are located all over our body, including deep in the skin's hypodermis layer which is mostly made of fat. They're most abundant on our fingers, the soles of our feet, and external genitalia, which makes these areas very sensitive to touch. Pacinian corpuscles are also commonly found in joints, ligaments, and tendons. These tissues are crucial for movement because joints connect bones, ligaments join bones, and tendons connect bones to muscles. Knowing which joints are changing direction is important, which is why having Pacinian corpuscles is helpful. Other sensory receptors in our skin can detect different changes, but the Pacinian Corpuscle (Figure 2) is the most important one to remember.

What is the structure of a Pacinian corpuscle?

The structure of Pacinian Corpuscles is intricate, consisting of layers of connective tissue separated by a gel-like substance called lamellae. When sliced vertically, the layered structure resembles an onion. At the core of these tissue layers is the ending of a single sensory neuron's axon. The sensory neuron's ending has a specific type of sodium channel called stretch-mediated sodium channels. These channels are named 'stretch-mediated' because their permeability to sodium changes when they're deformed, such as by stretching. This will be explained further below.

How does a Pacinian corpuscle perform its function?

As mentioned above, the Pacinian corpuscle responds to mechanical pressure, its stimulus. How does the Pacinian corpuscle transduce this mechanical energy into a nerve impulse that the brain can understand? This has to do with sodium ions.

Resting state

In the normal state of the Pacinian corpuscle, i.e. when no mechanical pressure is applied, we say that it is in its 'resting state'. During this state, the stretch-mediated sodium channels of the connective tissue membrane are too narrow, so sodium ions cannot pass through them. We refer to this as the resting membrane potential in the Pacinian corpuscle.

Application of pressure

In summary, Pacinian Corpuscles are a type of receptor cell that receives information from stimuli such as changes in mechanical pressure. They are located in the skin, joints, ligaments, and tendons. The structure of a Pacinian corpuscle consists of a single sensory neuron surrounded by connective tissue, separated by a gel-like substance. Stretch-mediated sodium channels are embedded in the membrane of the sensory neuron. When pressure is applied to the Pacinian corpuscle, the membrane is stretched, causing the sodium channels to open and allowing sodium ions to enter and depolarize the membrane. This leads to a generator potential and an action potential that passes to the central nervous system.

Pacinian Corpuscle

What is the importance of the Pacinian corpuscle?

Pacinian corpuscles allow us to distinguish between different levels of pressure that we touch as they respond differently to different levels of pressure.

Why is the Pacinian corpuscle described as a transducer?

A transducer is simply something that converts energy from one form to another. So, because the Pacinian corpuscle converts mechanical energy into a nervous impulse, we can describe it as a transducer. 

Which layer of skin contains Pacinian corpuscles?

The hypodermis contains the Pacinian corpuscle. This is found deep below the skin below the dermis. 

What are Pacinian corpuscles?

Pacinian corpuscles are mechanoreceptors in the body. They act as transducers by converting mechanical energy into nerve impulses which are sent to the brain. 

Which type of sensation can Pacinian corpuscles detect?

They detect mechanical energy in the form of pressure and movement, so are very important for distinguishing touch.

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