Ch.13-The Senses

Question 1

What are sensory receptors?

Answer 1

Sensory receptors sense change in their surroundings and include chemoreceptors, nociceptors, thermoreceptors, mechanoreceptors and photoreceptors.

Each type of receptor is most sensitive to a distinct type of stimulus.

Sensations are feelings resulting from sensory stimulation.

Question 2

What are general senses?

Answer 2

General senses include touch, pressure, temperature and pain.

They are associated with receptors in the skin, muscles, joints and viscera.

Question 3

What are special senses?

Answer 3

The special senses are smell, taste, hearing, equilibrium and sight.

Special senses have receptors within large, complex sensory organs of the head.

Question 4

Describe smell.

Answer 4

Olfactory organs consist of receptors and supporting cells in the nasal cavity.

Question 5

Describe taste.

Answer 5

Taste receptors consist of taste cells and supporting cells.

The 5 basic types of taste sensations are: sweetness, sourness, saltiness, bitterness and umami(deliciousness).

Question 6

Describe hearing and equilibrium.

Answer 6

The outer, middle and inner ear work together to receive vibrations, which are perceived as sounds.

The outer ear consists of the auricle(pinna), external acoustic meatus(external auditory canal) and the eardrum(tympanic membrane).

The middle ear(tympanic cavity) contains the auditory ossicles(malleus, incus, and stapes) and is connected to the throat via the auditory(eustachian) tube.

The complex inner ear is also important to establish the sense of equilibrium.
It contains chamber and tubes that form its bony labyrinth, which lies above a membranous labyrinth.
The semicircular canals aid in equilibrium, whereas the cochlea functions in hearing.

The sense of equilibrium consists of static and dynamic equilibrium.

In static equilibrium, the position of the head is sensed while the head and body are still.

In dynamic equilibrium, motion is detected when the head and body move or rotate, aiding in balance.

Question 7

Describe sight.

Answer 7

The sense of sight(vision) is the most dominant sense.

The eye has 3 distinct layers:

• the outer layer is fibrous and anterior in position, bulging forward to form the transparent cornea. The cornea and lens of each eye refract light waves to focus an image on the retina, which transmits visual perceptions to the brain. The white coloured sclera makes up most of the outer layer.
• the middle layer of the eye called the uvea, is vascular and includes the choroid coat, ciliary body and iris. The lens is held in position by many suspensory ligaments behind the iris and pupil.
• the inner layer of the eye is the nervous layer and consists of the retina and its millions of photoreceptors. When light waves bend to focus, the phenomenon is called refraction. Photoreceptors known as rods provide vision in dim light, without colour. Other photoreceptors called cones provide colour vision.