Unlike every living organism, human beings are blessed with certain organs which contain receptors that receive signals through the sensory neurons and relay it to the respective places within the nervous system. These organs are known as the sense organs. These signals help in the defense mechanism. There are two main types of receptors.
- General Receptors: These receptors are found in the muscles, skin, joints and the abdominal cavity.
- Special Receptors: These receptors are specifically present in the mouth and nose (chemoreceptors), eyes (photoreceptors), hypothalamus and skin (thermoreceptors), and ears (mechanoreceptors).
The chemoreceptors respond to taste, smell and blood pH, the photoreceptors respond to vision, the mechanoreceptors are triggered by the mechanical forces, and the thermoreceptors observe the changes in temperature.
Let us have a detailed view of the different senses and sense organs a human body has:
- Vision: The retina in the eyes contains the photoreceptors that detect the electromagnetic waves, and send the signals to the brain interpreting the image as vision.
- Sound: The sense of sound is perceived by the vibration of the eardrum in response to the changes in pressure. This motion is detected by the tiny hair-like fibre in the inner ear.
- Taste: Taste and smell go hand in hand. If you cannot smell something, you cannot taste it as well. The chemoreceptors are present on the taste buds that are responsible for the sense of taste. Sweet, sour, bitter and salty are the different types of tastes perceived by the four different kinds of taste buds.
- Touch: The skin contains the general receptors that are stimulated by touch, pain, temperature, and pressure. The skin receptors are activated on receiving the signals, which are carried to the brain via the spinal cord.
- Smell: The olfactory cells are present on the top of the nasal cavity. These olfactory cells are chemoreceptors which detect the differences in the chemicals. The olfactory nerve fibres carry the impulse stimulated by the chemicals and pass it to the olfactory bulb, which is directly attached to the cortex of the brain. The brain then detects what you are smelling.
Heart as a Sensory Organ: In addition to supplying oxygen and nutrients to various parts of the body, the heart is also known to be a sensory organ. The researchers had identified it to be the most powerful magnetic generator and receiver owing to the structure of heart. They had also discovered that 50-60 % of the heart cells are similar to the neural cells in the brain. That is why our heart reflects emotions during certain situations. The heart also consists of different groups of receptors that are stimulated by the changes in the pressure in the cardiac chambers. Thus, our heart is also considered as one of the sensory organs in our body and is imagined to be linked with the brain.
We now know what the different senses are, and how important they are for a normal human being. These are an integral part of our body and help us to lead a comfortable life.
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