Sense Organs – Class 11 | Chapter – 21 | Biology Short Notes Series PDF

Sense Organs: We have five sense organs that can receive and relay sensory information to the brain. These senses provide an organism with information crucial for perception. The different sense organs and the senses they provide are mentioned below:

Sense Organs

Eyes – Sight or Ophthalmoception

These are the visual sensory organs in our body. These are sensitive to light images. The eyes vary in colour depending upon the amount of melanin present in our body. It helps in the sense of sight by detecting and focussing on the light images.

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 that perform functions distinct from each other. These are Rod and Cones.

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

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

Ears – Hearing or Audioception

Ears are the auditory sense organs of our body. They help us to perceive sounds. Our auditory system detects vibrations in the air and this is how we hear sounds. This is known as hearing or audio caption.

The ears are divided into three sections, namely, the outer ear, the inner ear, and the middle ear. All sounds are basically vibrations, so the outer ear transfers 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 balancing our body or equilibrium.

Tongue – Taste or Gustaoception

The tongue helps in perceiving various tastes and flavours. The taste buds are present between the papillae on the tongue—these help in sensing different tastes.

The senses of smell and taste tend to work together. If one could not smell something, they could not taste it either. The sense of taste is also known as gustaoception.

Taste buds on the tongue contain chemoreceptors that work similarly to the chemoreceptors in the nasal cavity.

However, 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.

Nose – Smell or Olfalcoception

The nose is an olfactory organ. Our olfactory system helps us to perceive different smells. This sense of organ also aids our sense of taste. The sense of smell is also known as olfaction.

The olfactory cells tend to line the top of the 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 in, the air enters into the nasal cavity. The olfactory cells are chemoreceptors, which means that the olfactory cells have protein receptors that can detect subtle differences in chemicals. These chemicals bind to the cilia, which conducts a nerve impulse that is carried to the 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 is the reason why the food which we eat tastes bland.

Skin – Touch or Tactioception

Skin is the largest organ of our body. It is related to the sense of touch. The sense of touch is also referred to as 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, and when activated, is carried to the spinal cord and then to the brain.

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By Team Learning Mantras