Railway Science (Biology – Sensory Organs)

Fovea (fovea centralis) - It is a small depression within the neurosensory retina where visual acuity is the highest. Vitreous body - The clear gel that fills the space between the lens and the retina of the eyeball (the vitreous chamber) in humans and other vertebrates.
Blind spot - Small portion of the visual field of each eye that corresponds to the position of the optic disk (also known as the optic nerve head) within the retina.

Sclera is the white outer coating of the eye. It helps maintain the eyeball's shape and protects it from injury. Ciliary body contains the ciliary muscle, which changes the shape of the lens when your eyes focus on a near object.
Iris is behind the cornea with an adjustable circular opening in the centre called a pupil. Choroid is part of the middle layer of the wall of the eye between the sclera and the retina.

auditory canal’s function is to transmit sound from the pinna to the eardrum. Pinna (Auricle) is the visible portion of the outer ear. It collects sound waves and channels them into the ear canal. The Tympanic Membrane (eardrum) separates the middle ear and the external ear. It has a rather simple function, sound transmission and amplification.

Olfactory indicator : A substance whose smell varies when it is mixed with an acidic or basic solution. Example - Vanilla, Onion and clove.
Natural Indicator : A type of indicator that can be found naturally and can determine whether the substance is an acidic or a basic. Example - Turmeric, grape juice, petunia leaves, litmus.

Eye contains two types of photoreceptor cells. These cells contain light sensitive proteins called photopigments. These photoreceptor cells are responsible for color vision. Cones - sensitive to bright light and produce color sensation. Rods are sensitive to dim light and give twilight vision.

Tympanic membrane:- It is made up of a thin connective tissue membrane covered by skin on the outside and mucosa on the internal surface.
Eustachian tubes - Connect the middle ears to the back of your throat.
They help drain fluid and equalize the air pressure inside your ears.
Cochlea - A fluid-filled, spiral-shaped cavity found in the inner ear that plays a vital role in the sense of hearing.
Pinna - External part of the ear consists of funnel-like curves that collect sound waves and transmit them to the middle ear.

Iris: The colored part of the eye that surrounds the pupil and adjusts the size of the pupil.

Cartilages - It is a type of connective tissue in the body. Cartilage smoothens bone surfaces at joints and is also present in the nose, trachea and larynx. The different types of connective tissues in our body include areolar tissue, adipose tissue, bone, tendon, ligament and blood.

The middle ear transmits the amplified pressure variations received from the sound wave to the inner ear. In the inner ear, the pressure variations are turned into electrical signals by the Cochlea. These electrical signals are sent to the brain via the auditory nerve, and the brain interprets them as sound. Pinna - It is the part of the outer ear that directs the sound waves to travel through the ear canal to reach the eardrum.

Rods and cones are the two types of photoreceptor cells found in the human retina that gather light. The rods are in incharge of low-light vision, whereas the cones are in incharge of high-light vision.