Meissner corpuscle, Pacinian corpuscle, Ruffini ending , Merkel disc

Summary

This video provides an in-depth look at the different types of touch and pain receptors in the skin, categorizing them into two groups: the apical group (Merkel disk and Meissner's corpuscles) and the basal group (Pacinian corpuscles and Ruffini endings). It explains the functions of each receptor, including their sensitivity to fine touch, vibration, and stretch, as well as their differences in adaptation rates (slow vs. fast). Additionally, it covers pain receptors (free nerve endings) and the axon types involved in signal transmission, offering a clear and engaging explanation of skin sensory perception.

Takeaways

• 😀 Merkel disks are fine touch receptors found in the stratum basale of the epidermis, and they adapt slowly to stimuli.
• 😀 Meissner's corpuscles, located in the dermal papillae, sense fine touch and 50 Hz vibration, and they adapt rapidly.
• 😀 The apical group of receptors includes Merkel disks and Meissner's corpuscles, both with small receptive fields and distinct adaptation types.
• 😀 Pacinian corpuscles and Ruffini endings are found in the reticular dermis and make up the basal group of receptors.
• 😀 Pacinian corpuscles sense deep touch and high-frequency vibration (200-300 Hz), adapting rapidly to stimuli.
• 😀 Ruffini endings sense skin stretch and adapt slowly, continuing to send signals as long as the stretch persists.
• 😀 Pain is sensed by free nerve endings, which extend into the epidermis and adapt rapidly to stimuli like heat or sharp pain.
• 😀 Adaptation rates of skin receptors vary: slow adaptation (Merkel disks, Ruffini endings) vs. rapid adaptation (Meissner's corpuscles, Pacinian corpuscles).
• 😀 Pain receptors (free nerve endings) use Aδ and C fibers, which transmit pain signals at slower speeds compared to touch receptors using Aβ fibers.
• 😀 The size of receptive fields also varies, with apical receptors (Merkel and Meissner) covering smaller areas, while basal receptors (Pacinian and Ruffini) cover larger areas.

Q & A

What are the two main groups of skin receptors discussed in the video?

The two main groups of skin receptors are the apical group and the basal group. The apical group includes Merkel disks and Meissner's corpuscles, while the basal group includes Pacinian corpuscles and Ruffini endings.

What is the key difference between the Merkel disk and Meissner's corpuscle?

Both Merkel disks and Meissner's corpuscles detect fine touch, but Meissner's corpuscle also senses low-frequency vibration (around 50 Hz), whereas the Merkel disk is primarily sensitive to fine touch. Additionally, Meissner’s corpuscles adapt more quickly than Merkel disks.

How do Merkel disks and Meissner’s corpuscles differ in terms of adaptation?

Merkel disks are slowly adapting receptors, meaning they continue to send signals as long as the stimulus is present. In contrast, Meissner’s corpuscles are rapidly adapting, meaning they stop sending signals quickly once the stimulus is no longer detected.

What is the function of Ruffini endings and where are they located?

Ruffini endings are located in the reticular dermis and they detect skin stretch. They are slowly adapting, providing continuous feedback about skin deformation over time.

What kind of stimuli do Pacinian corpuscles sense, and where are they located?

Pacinian corpuscles, located in the reticular dermis, sense deep touch and high-frequency vibrations (200-300 Hz). They are rapidly adapting receptors, meaning they stop responding quickly to a constant stimulus.

What is the role of free nerve endings in the skin?

Free nerve endings are responsible for sensing pain and temperature. They are found in the epidermis, extending into the stratum spinosum, and are rapidly adapting to quickly detect harmful stimuli such as heat or sharp pressure.

How do the receptive fields of apical and basal group receptors differ?

Apical group receptors, like Merkel disks and Meissner's corpuscles, have smaller receptive fields, which allow for more precise detection of stimuli. In contrast, basal group receptors, like Pacinian corpuscles and Ruffini endings, have larger receptive fields, which are suited for detecting broader, deeper stimuli.

What does 'adaptation' mean in the context of skin receptors, and how does it affect sensation?

Adaptation refers to how receptors stop responding to a continuous stimulus over time. For example, when wearing a t-shirt, Meissner’s corpuscles will quickly stop sensing the touch, while Merkel disks will continue to send signals for a longer period. This helps us focus on changes in stimuli rather than constant sensations.

What are the different types of axons involved in skin receptor signaling, and how do they differ?

A-beta fibers carry signals from touch receptors (Merkel disks, Meissner’s corpuscles, Pacinian corpuscles, and Ruffini endings) and are myelinated, transmitting signals quickly. A-delta fibers carry fast pain signals, while C fibers carry slow pain signals. A-delta fibers transmit signals at 20 meters per second, while C fibers are slower at 2 meters per second.

What is the purpose of using 'A-beta fibers' for touch receptor signaling?

A-beta fibers are myelinated and allow for the rapid transmission of touch information from receptors like Merkel disks and Meissner’s corpuscles. This allows us to quickly sense fine touch, vibrations, and pressure changes in the skin.