Biology Chapter: Sensory Receptors and the Eye

Sensory Receptors

• Sensory receptors detect and respond to changes in the internal or external environment.
• Sensory receptors generate electrochemical messages
• Sensations occur when the brain receives impulses.
• Perceptions occur when the cerebral cortex integrates sensory input.
• Sensory adaptation occurs when sensory receptors stop responding to continuous stimulation.
• Pressure and touch receptors adapt quickly, while muscle and joint receptors do not.

The Eye

• The eye is made up of the outer tunic, the middle tunic, and the inner tunic.
• The outer tunic is composed of the sclera, the cornea, and the conjunctiva.
• The middle tunic is composed of the choroid, the ciliary body, and the iris.
• The inner tunic is composed of the retina.
• The retina contains photoreceptors called rods and cones.
• Rods are responsible for black and white vision in dim light.
• Cones are responsible for color vision and visual acuity.
• The fovea is a small pit in the retina concentrated with cones that provides detailed color vision.
• The lens focuses light onto the retina.
• Aqueous humor refracts light and helps maintain the shape of the eyeball.
• Vitreous humor refracts light and also helps maintain the shape of the eyeball.
• The optic nerve transmits impulses from the retina to the brain.

Hearing

• The loudness of a sound is determined by the amplitude of the sound wave.
• The pitch of a sound is determined by the frequency of the sound waves.
• The ear is made up of the outer ear, the middle ear, and the inner ear.
• The outer ear collects sound.
• The pinna gathers sound and channels it to the external auditory canal, which helps determine sound direction.
• The tympanic membrane separates the outer ear from the middle ear and vibrates at the same frequency as sound waves.
• The middle ear:
  • Contains the malleus, incus, and stapes.
  • Is an air-filled cavity that amplifies sound.
• The Eustachian tube connects the middle ear to the throat.
• The inner ear:
  • Contains the cochlea and the vestibular apparatus.
  • The cochlea is fluid-filled and houses the spiral organ (of Corti).
  • The spiral organ contains the hair cells.
  • The oval window is a membrane between the middle and inner ear that the stapes presses against.
  • The round window is a membrane at the end of the lower canal in the cochlea that relieves pressure created by movements of the oval window.
• The vestibular apparatus, composed of the vestibule and semicircular canals, is responsible for balance.
  • The vestibule contains the utricle and saccule.
  • Semicircular canals are oriented at right angles to one another.
  • The vestibular apparatus monitors the position and movement of the head.
• The vestibule maintains static equilibrium, which is the awareness of the position of the head when the body is still.
• The semicircular canals maintain dynamic equilibrium, which is the awareness of the position of the head when the body is in motion.
• Deafness can be conductive or sensorineural.
• Conductive deafness occurs when sound waves cannot be transmitted properly to the inner ear.
• Sensorineural deafness occurs when there is damage to the hair cells, the auditory nerve, or both.
• Loud sounds can cause sensorineural deafness.

Vision

• Glaucoma occurs when drainage of the aqueous humor is blocked.
• This blockage results in increased pressure in the eye, which damages blood vessels supplying the optic nerve and retina.
• Glaucoma causes progressive and painless loss of vision.
• Cones are responsible for color vision.
• There are three types of cones: red, blue, and green.
• Lack of or reduced number of cone types results in color blindness.

Explore the fascinating world of sensory receptors and the structure of the eye in this quiz. Understand how sensations and perceptions are formed, as well as the role of different parts of the eye in vision. Test your knowledge on the adaptation of sensory receptors and the functions of rods and cones.