Sensation and the Sensory Organs (Vision and Audition)

With the help of our senses we are able to make sense of the world we live in. The study of sensation or senses is crucial from the point of view of psychology as because of it consciousness is possible. Let us understand the role played by different sense organs in the process of sensation.

Vision

Vision is the most crucial sense as without proper vision life will be very difficult. For the vision to be taking place one main stimulus is required and that is light. Light comprise of certain electromagnetic waves which has the ability to travel through vacuum as well. Electromagnetic waves are made up of magnetic and electrical fields. It’s because of the electromagnetic waves communication with the astronauts from earth is possible. These waves are called light which makes vision possible and the sensory organ eye helps in translating the light into meaningful information. In the front portion of the eye is the cornea which bends the light waves and makes it fall on the lens because of its convex shape.

Human eye has three layers

  • The Sclera: The sclera comprises of the cornea and is responsible for protecting, supporting and maintaining the eye.
  • The Choroid: The choroid includes the iris, pupil and the lens which ensures nourishment for the eye and keeps the eye oxygenated.
  • The Retina: The retina comprises of rods and cones which allows converging the images into one whole.

The cornea helps in focusing the rays as the light enters the eye through the pupil. The pupil plays the role of a gatekeeper, which regulates the light required for having a proper vision of the image. Iris is the pigmented portion around the pupil, which provides colour to the eye of a person and equally acts as the pupil’s sphincter or stop. Light enters the eye due to the contraction or dilation of the pupil which is done by the iris muscles. The lens which is behind the pupil, performs the function similar to that of a camera. Together along with the cornea, the lens adjusts the image to be seen by retina. Vision actually occurs at the retina with the help of cones and rods which provide image shadow and colour. The image is then translated into neural impulses which are then transferred to the brain through optic nerves for processing the information. The visual cortex interprets the image to extract meaning. Coloured vision occurs because of the photoreceptor cells comprising of rods and cones. Cones help in day time vision while the rods help in the night vision. Cones are responsible for coloured vision whereas rods are responsible for shadows and light images. Coloured vision plays a crucial role in both communication and perception. Cones have the coloured sensors, which respond to colour bands along the regions of red, green and blue. Colours have three important attributes namely brightness, hue and saturation. A combination of these three attributes contributes to the coloured vision. Apart from this, vision of other colours occurs with the activation of multiple cones by way of which the three colours are mixed for forming new colours just the way in which different colour combinations are formed by combining or mixing colours in painting.

Audition

The sense of hearing is attributed to the auditory system, which with the help of ear collects and interprets various sound waves. Ear has three parts: inner ear, outer ear and middle ear, which allow us to hear different sound waves by performing specialized functions.

The outer ear is the external portion of the ear much of which can be seen, which comprises of the tympanic membrane, the ear canal and the pinna. The outer ear gathers the sound from outside and amplifies the sound wave. The sound waves pass through the ear canal and the amplified version of the sound passes through the ear drum, after which the sound enters the middle ear by vibrating through the tympanic membrane.

The middle ear has three bones: The malleus which senses the sound vibration and transfers to the next level that is the Incus. The incus acts as a bridge between the next bone stapes and the malleus. The stapes transfer the sound waves from the incus to the inner portion of the ear. In this way, the middle ear plays the role of a gatekeeper or the protector which protects the ear from any kind of damage from loud or harsh sound.

The inner ear has fluid and when the stapes transfers the sound waves to the inner ear, it results in some fluid movement in the cochlea. The cochlea transforms the sound waves into neural or electrical signals which are then transmitted to the brain for processing the information. The cochlea has three fluid filled spaces namely the vestibular canal, the tympanic canal and the middle canal. The basiliar membrane in the cochlea play a similar kind of role in hearing as the retina does in vision. Through the auditory nerves, the sound is passed onto the brain, which then responds to these signals or frequencies to compose a complete sound out from them.

Human brain is also capable of sound localization, which is defined as our capability to judge sound from the source from where it has originated, which is dependent on the sound quality and also the hearing ability of both the ears.

Hearing occurs because of the stimulus that is the sound wave. Sound waves occur because of the vibration which involves a medium such as air or water for travelling. The pitch is determined by the sound wave frequency whereas the loudness is determined by the sound wave amplitude. Frequency is measured in terms of Hertz (Hz) and one vibration is equal to one hertz. Hence, with the increase in the vibration of the sound wave, the pitch which we will be able to hear will be higher. The sound wave intensity on the other hand is measured in terms of decibels (dB), which means the sound will be louder, in case of greater decibels. The sensations which are associated with hearing are Pitch, Loudness and Timbre (quality of the sound).


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