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.

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

Explain the difference between a stimulus and a sensation, and give an example of each using a cup of hot chocolate.

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.

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.

Name the three parts into which the ear is divided and state in which of them the receptor cells that transform sound into nerve impulses are found.

Describe the path a sound follows from the moment it enters the pinna of the ear until the brain interprets it, naming the structures that transmit it and the place where it is transformed into a nerve impulse.

Some people with an inner ear infection feel dizzy and lose their balance. Taking into account that the inner ear does not only detect sounds, explain what other information it sends to the brain and which structures are responsible for it.

When we accidentally touch a hot frying pan, we feel pain instantly. Explain which skin receptors warn us of the danger and why this sensation, although unpleasant, is useful to the body.

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 flavour.

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 fibres 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.