Sense Organs

What are sense organs?

Sense organs are specialized organs that help to perceive the world around us. These senses govern our association and our interaction with the environment. The list of sense organs include:

  1. Eyes
  2. Ears
  3. Nose
  4. Tongue
  5. Skin

These sense organs and organ systems contain receptors that relay information through the sensory neurons to the appropriate places within the nervous system. The receptors could be classified into two parts viz. the general and special receptors. The former is present throughout the body while the latter includes chemoreceptors, photoreceptors, and mechanoreceptors.

Five senses

  1. Sight or Ophthalmoception:

  2. The iris in the eye is the coloured part that controls the size and diameter of the pupil, which directly affects the amount of light entering the eyes. Behind the lens of the eye lies the vitreous body. It is filled with a gelatinous material called the vitreous humour. This substance gives shape to the eyeball and also transmits light to the very back of the eyeball, where the retina is found.

    This retina contains photoreceptors, which detect light. There are two types of cells present which perform functions distinct from each other.

    • Rods

    These sensors function in low light and are found at the edges of the retina. They also aid in peripheral vision.

    • Cones

    These type of retinal cells work best in bright light, detecting fine details and colour. There are three types of cones for detecting 3 primary colours of light, namely: blue, red and green. Typically, colour blindness occurs when any one of these types of cones are not present.

  1. Hearing or Audioception:

The ears are divided into 3 sections, namely, outer ear, inner ear, and the middle ear. All sounds are essentially vibrations, so the outer ear channels these vibrations into the ear canal, where these vibrations are transformed by the brain into meaningful sound. Apart from hearing, this sense is also important for balance or equilibrium.

  1. Taste or Gustaoception:

The senses, smell and taste tend to work together. The key sense organ for taste would be the tongue. If one could not smell something, they could not taste it either. Taste buds on the tongue contain chemoreceptors that work similar to the chemoreceptors in the nasal cavity.

But, the chemoreceptors in the nose would detect any kind of smell, whereas there are four different types of taste buds and each one can detect different types of tastes like sweetness, sourness, bitterness, and saltiness.

  1. Smell or Olfalcoception:

The olfactory cells tend to line the top of your nasal cavity. On one end, olfactory cells have cilia that project into the nasal cavity and on the other end of the cell, are the olfactory nerve fibres.

As one breathes, anything that is in the air enters your nasal cavity. The olfactory cells are the chemoreceptors, which means that the olfactory cells have protein receptors that can detect subtle differences in chemicals. The chemicals bind to the cilia, which generate a nerve impulse that is carried to your brain. The brain then translates these impulses into a meaningful smell. During a cold, the body produces mucus which blocks the sense of smell, this means that the food which we eat tastes bland.

  1. Touch or Tactioception:

The skin contains general receptors which can detect touch, pain, pressure, and temperature. They are present throughout the skin. Skin receptors generate an impulse, once activated is carried to the spinal cord and then to the brain.

Other Senses:

But besides these 5 senses, there are another two that helps to orient us with the world, they are:

  • Vestibular system

This sense helps us to identify the orientation and posture of our bodies in relation to the environment.

  • Proprioception system

This sense helps the body to identify where every muscle, joint or limb is located in 3D space and the direction it is moving in relation to the body.

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