This article will give the reader an idea of a significant part of the structure of the nervous system of the human body: the work of receptors. Everything that a literate person needs to know on this topic can be read below.
In this article, you can learn about the structure and mechanism of tactile receptors in the skin, muscles, ligaments, receptors in the organ of vision, and what pathologies can lead to.
A person learns the world, receives any information about the external environment using a variety of receptors. A receptor is a special specialized cell, the so-called sensitive neuron, which has nerve endings.
They perceive and stimulate external stimuli, such as light and heat, and stimuli from the internal environment of the body.
Everything you need to know about receptors
Associative neurons in the brain and spinal cord collect and translate information from sensory neurons. Sensitive neuron receives any irritation and converts it into nerve impulses that provide information transfer to the central nervous system and executive organs. From all parts of the body, impulses come to the spinal cord and, passing through it, end their journey in the cerebral cortex.
Information travels through neurons in the form of a weak electrical signal. This is what is meant by the concept of "nerve impulse".
When it reaches the junction of one neuron with another, fluid is released - neurotransmitter. If a sufficient amount of this substance is released in the next neuron, the impulse goes on.
Tactile receptors in the skin
Tactile receptors in the skin can be classified into different classifications, but generally they imply fast adapting and slow adapting. Adaptation, if we refer exclusively to the topic of receptors, is a special property of sensory receptors to reduce the frequency of irritation in the presence of a constant strong stimulus. Simply put, it can be compared to the so-called "acquisition of immunity" or "addiction."
Rapidly adapting receptors in the skin include:
- free nerve endings;
- cones Krause;
- little pacini corpuscle;
- Meissner bodies.
It is impossible to "give up" any of the receptors described above. Each of them fulfills its own unique role, thanks to which a person can interact with the world around him. Krause cones are a special capsule, lamellar type. It surrounds the nerve ending, which is a spiral or a rod. The cones get irritated and respond to low frequency vibrations.
Pacini's bodies are special oval-shaped structures. Their length ranges from zero point five millimeters to two millimeters. Located in the deep layers of the dermis, their main function is to recognize vibration. Receptors with a slow decrease in frequency from an irritant include:
- Merkel discs;
- Ruffini's little body;
- root plexus of hair;
- Meiner's little body.
Displacements of the skin for a long time cannot go unnoticed. If the skin has changed its location, then Ruffini's little bodies are irritated, which send the corresponding nerve impulses. They are specialized endings and are located in the deep layers of the epithelium. The endings of the sensitive process of the neuron form a network of thin threads in the capsule that connects the tissues.
The receptors, called the "hair root plexus", respond to any movement of hair on the human body. Sensory nerve endings form an intricate network near the hair root with the surrounding space, or, as they say, the root sheath. This network is located directly under the sebaceous glands. Meiner's bodies detect skin movements and low-frequency vibrations. Their nerve endings form a spiral in the capsule, the branches of which are isolated from each other.
Muscle receptors
Any, even insignificant change that has occurred in the muscles of the human body should not go unnoticed. The receptors responsible for the transmission of impulses from the muscles ensure a stable position of the body in space. These specialized cells provide the central nervous system with information about the displacement, extension, and rate of change in muscle length. These receptors include:
- tendon receptor;
- muscle spindle;
- sensory nerves;
- connective tissue sheath;
- motor nerves.
Tendon filaments extending from muscle fibers form a complex system called tendon receptors. When the fibers enter the capsule, they branch strongly among the tendon filaments, and this makes it possible to catch all the necessary stimuli.
Muscle spindles are the so-called "tension receptor". Special endings are connected to it, catching muscle tension and transmitting impulses to the executive organs. These fibers are surrounded by a connective tissue capsule. They belong to the so-called subgroup of muscle tension receptors.
Motor nerves are the next complex sensory receptors that contain processes of nerve cells. These processes lie directly in the nuclei of the nerves of the spinal cord.
Any feelings associated with tension or other muscle changes are formed in connection with the activity of muscle receptors in skeletal muscles located between the muscle fibers.
Muscle receptors play an important role in human movement if they are responsible for muscle contraction and the transmission of nerve impulses to the nephron and then to the axon.
Retinal receptors
Everyone understands that a person receives the largest percentage of information about the environment with the help of the organs of vision, that is, the eyes. The eyes are our organs of vision. We see objects, because the rays of light, as it were, grab objects and enter the image into the eyes. Light-sensitive cells located at the back of the eye send information to the brain, where the information is converted into pictures or images.
Only the retina has sensitivity to light rays from all organs of vision. It is on its rear grid that the image that we get with the eyes is located.
The retina consists of light-sensitive receptors, the main ones being rods and cones. They translate the image into nerve impulses that travel to the brain via the optic nerve. In the brain, these impulses are converted into an image.
The retina contains many receptors, such as:
- cones;
- sticks;
- pigment epithelium;
Rods and cones are photosensitive cells derived from neurons. There are many more rods in the human retina than cones. Each eye contains 125 million of the former and only seven million of the latter. The rods only recognize white and black images, but they function well in dim light. Cones allow you to see a color image, although they need bright light to work. At night we see everything in gray, because only sticks work in the dark. They are located on the far wall of the retina, and the cones are found in the central zone.
Everything in the human body needs nutrition, and cells that are particularly responsive to light are no exception. Their needs are satisfied by the pigment epithelium of the eye, which takes organic matter from the circulatory system, the vessels of the middle membrane of the eye.
Ligament receptors
Ligament receptors are of two types. The first type is similar to Ruffini's little bodies: the same complex network of thin threads in the connective tissue capsule. The second type is called "encapsulated" and implies the same type of nerve endings as the tactile bodies and, like the first type, is enclosed in a capsule.
What do receptor pathologies lead to?
Receptor pathology, like a disease, is endocrine in nature.
Nervous system disorders, that is, a deviation from the norm or damage to nerve endings, can be very dangerous, especially if they imply a change in the genotype of the organism.
Basically, damage to the nerve endings occurs due to severe burns or other damage to the hypodermis.
The first symptom is impaired sensitivity, which is divided into several subtypes: impaired contact sensitivity and distant sensitivity.
The first type involves deviations in tactile sensations. That is, pain and temperature. It takes place when not only the skin is damaged, but also mucous tissues.
The second type is disorders of vision, hearing, taste, smell.
Any deviations are fraught with either a decrease in sensitivity, or, conversely, an increased reaction to a stimulus.
