Answers to Revise Questions

What is the stimulus for sight?

Ans: The stimulus for sight is light or electromagnetic radiation.

What is the stimulus for equilibrium?

Ans: The stimulus for equilibrium is gravitational forces.

What is the receptor organ for hearing?

Ans: The receptor organ for hearing is the cochlea of the ear.

How is sound converted to mechanical energy for hearing?

Ans: Airborne waves are converted to mechanical vibrations by the tympanic membrane and the auditory ossicles.

In terms of sight, what is a direct reaction?

Ans: When the pupil constricts as a result of light, the response is called a direct reaction.

What are the different types of sensory organ and the types of sensation that they transmit?

Ans: Sensory receptors respond by initiating a nervous impulse when stimulated by the sensation to which they are sensitive. External and internal receptors provide the body with information about changes in both the external and internal environment.

  • Eye – Vision: carried by optic nerves, synapse in thalamus, and is perceived in the occipital lobe.
  • Ear – Hearing: carried by the vestibulocochlear nerve to the auditory area in the brain.
  • Ear – Balance: carried by the vestibulocochlear nerve to the vestibular nucleus and the cerebellum.
  • Nose – Smell: carried through the olfactory bulb and tract to the limbic system and then the olfactory area in the temporal lobe. The limbic system is strongly involved in emotion, and smell frequently invokes strong emotions.
  • Tongue – Taste: carried by several cranial nerves, synapse in the thalamus, and is transmitted to the cerebrum.
  • Skin – Pain, Touch, Heat and Cold.

What protects the eye?

Ans: The eyelids, conjunctivae and lacrimal apparatus.

What are the three layers of the wall of the eye?

Ans: The sclera, choroid and retina.

What is the retina made up of? How does it communicate to the brain?

Ans: Millions of photoreceptors, known as rods and cones, receive light through the lens and then convey signals to the optic nerve and subsequently to the visual cortex of the brain.

What prevents the eye from collapsing?

Ans: The vitreous and aqueous humours.

What is the function of the middle ear?

Ans: To transmit sound vibrations to the inner ear.

What are the two functions of the inner ear?


  1. To transmit sound waves through the cochlea to the division of the eighth cranial nerve.
  2. The semicircular canals and vestibule help maintain balance through the equilibrium receptors.

What is proprioception?

Ans: Awareness of the position and location of the body and its parts.

Where are proprioceptors located?

Ans: In the inner ear, joints and ligaments.

What are proprioceptive stimuli needed for?

Ans: Balance, coordinated movement, and deciding on the degree of muscular contraction.