Brent Cornell

    
The human eye is the sensory organ responsible for vision (sight perception)

• It consists of two fluid-filled cavities separated by a lens (anterior = aqueous humour, posterior = vitreous humour)
• The lens is attached to ciliary muscles, which can contract or relax to change the focus of the lens
• The amount of light that enters the eye via the pupil is controlled by the constriction and dilation of the iris
• The exposed portion of the eye is coated by a transparent layer called the cornea, which is lubricated by conjunctiva
• The internal surface of the eye is composed of three layers – the sclera (outer), choroid (middle) and retina (inner)
• The region of the retina responsible for sharpest vision (i.e. focal point) is the fovea centralis (or fovea for short)
• Nerve signals from the retina are sent via an optic nerve to the brain (no retina in this region creates a visual blind spot)

Diagram of the Human Eye

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The retina is the light-sensitive layer of tissue that forms the innermost coat of the internal surface of the eye

• Two types of photoreceptors (rods and cones) convert light stimuli into electrical nerve impulses
• These nerve impulses are transmitted via bipolar cells to ganglion cells, whose fibres from the optic nerve tract
• The photoreceptors line the rear of the retina (adjacent to the choroid), meaning light passes through the other cell layers

Diagram of the Human Retina

   
The human ear is the sensory organ responsible for hearing (sound perception)

• The external part of the ear is called the pinna, whereas the internal part of the ear is divided into three sections
• The outer ear contains the auditory canal, which channel sound waves to the tympanic membrane (or eardrum)
• The middle ear contains three small bones called the ossicles, which transfer vibrations to the oval window
• The inner ear consists of the cochlea and semicircular canals, as well as a round window which dissipates vibrations
• The cochlear converts sound stimuli into electrical nerve impulses, which are transmitted via the auditory nerve to the brain

Diagram of the Human Ear

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