Exercises: Sensory receptors

Match each of the five senses with the type of stimulus it detects and with the organ where its main receptors are located.

In the cross-sectional image of the eye, several structures have been marked with numbers. Write the name of the five marked structures and state in which of them light receptor cells are located.

Explain what a sensory receptor is and why we say that the senses are the "gateway" for information entering the nervous system.

Describe the path followed by light information from the moment light from an object enters the eye until the image is formed, naming the structures it passes through and the location where it is converted into a nerve impulse.

When you go from a dark room to a very sunny street, you are dazzled for a few seconds. Explain which structure of the eye regulates the amount of light entering, how it acts in that situation, and what this adaptation mechanism is called.

Taste buds and olfactory cells work together when we eat: this is why, with your nose held, a raw apple and a raw onion "taste" almost the same. Explain what each sense contributes to the perception of food flavor.

A classmate claims the following: "A person with myopia cannot see distant objects well because their lens focuses light too weakly; therefore, to correct it, a convergent lens must be used, which focuses light rays more strongly towards the back of the eye."

1. a) Refute your classmate's claim in a reasoned manner, explaining why the optical problem of myopia is not due to a lack of light convergence.
2. b) Predict what would happen to that person's distance vision if they used glasses with convergent lenses: would they see more clearly or even more blurrily? Justify your answer by indicating where the focal point would form relative to the retina.
3. c) Justify what type of lens they actually need and explain how it must deviate the path of light rays before they enter the eye in order to correct the defect.

A young man visits the doctor after noticing severe hearing loss due to continuous headphone use at very high volume. Diagnostic tests reveal that his tympanic membrane and ossicular chain are intact and transmit vibrations completely normally, but the ciliated mechanoreceptors of the cochlea (inner ear) have been destroyed.

1. a) Justify why the patient suffers from deafness if the elements responsible for capturing and transmitting sound in the outer and middle ear are working properly. In your answer, distinguish between the physical transmission of vibrations and their transduction into nerve impulses.
2. b) The patient asks if the injury will heal in a few weeks with rest, just as a skin wound or a perforated eardrum heals. Argue why doctors rule out this possibility based on the regenerative capacity of receptor cells compared to epithelial cells.
3. c) Predict with reasoning whether a conventional hearing aid (which amplifies sound vibration in the ear canal) would solve the hearing loss at the frequencies where the ciliated receptors have completely disappeared.

With your eyes closed, you hold a very cold glass that is slipping through your fingers. As you squeeze it tightly to keep it from falling, a broken edge causes a superficial cut on your fingertip. Simultaneously and immediately, you distinguish three sensations: the coldness of the water, the pressure you exert on the glass, and the pain from the cut.

1. a) Identify which specific type of cutaneous receptor captured each of those three stimuli and classify them according to the nature of the stimulus they detect.
2. b) Knowing that all nerve fibers transmit information via identical electrochemical impulses, justify how the brain manages to distinguish and interpret all three sensations at once without confusing pain with cold or pressure.
3. c) If a local anaesthetic exclusively blocked the nociceptors in the area, predict what stimuli you would still perceive and explain why the congenital insensitivity to pain poses a serious threat to survival.