Sensory Receptors and the Five Senses

45 question-and-answer flashcards reviewing key concepts from Chapter 8 on sensory receptors, the eye, ear, nose, tongue, skin, pain mechanisms, and proprioception.

What are the five senses?

Touch, taste, sight, smell, and hearing.

What is a stimulus?

Any change to the internal or external environment.

How is stimulus intensity coded in sensory neurons?

By the frequency of action potentials; stronger stimuli produce higher firing rates.

What is receptor potential?

A graded change in membrane potential produced when a receptor transduces stimulus energy, sometimes leading to an action potential.

Outline the basic pathway from stimulus detection to CNS integration.

Receptor absorbs energy → transduction to electrical energy → receptor potential → action potential in sensory neuron → signal sent to CNS for integration.

What is sensory adaptation?

A decline in receptor firing rate and perception after prolonged exposure to a constant stimulus.

Which receptors respond to visible light?

Photoreceptors.

Which receptors convert mechanical forces into electrical signals?

Mechanoreceptors.

What do nociceptors detect?

Damaging stimuli such as extreme pressure, temperature, or chemicals (pain).

What is the tough white outer layer of the eye called?

The sclera.

Which transparent structure covers the iris and pupil and is known as the “window of the eye”?

The cornea.

Which pigmented layer absorbs stray light and nourishes the retina?

The choroid.

Which photoreceptors allow vision in dim light?

Rods.

Which photoreceptors are concentrated in the fovea and mediate color vision?

Cones.

What is accommodation in the eye?

Changing lens shape via the ciliary muscle to focus on near or distant objects.

How does the pupil react to bright light?

It constricts (gets smaller).

Which fluid fills the anterior cavity of the eye?

Aqueous humor.

Excess aqueous humor causing high intraocular pressure leads to what condition?

Glaucoma.

Describe the visual pathway from photoreceptors to the brain.

Photoreceptors → bipolar cells → ganglion cells → optic nerve → optic chiasm → lateral geniculate nuclei → primary visual cortex.

What happens to rhodopsin when exposed to light?

It splits into opsin and retinal, initiating phototransduction (This breakdown when exposed to light, leads to its transduction and transmission of neural signals.)

What is the function of the pinna?

It amplifies and directs sound waves into the external auditory canal.

Name the three auditory ossicles in order from tympanic membrane to oval window.

Malleus, incus, stapes.

Which tube equalizes pressure between the middle ear and nasopharynx?

The eustachian (auditory) tube.

What fluid fills the bony labyrinth of the inner ear?

Perilymph.

Which cochlear structure houses the hair cells for hearing?

The organ of Corti.

Which membrane’s movement bends stereocilia on hair cells?

The basilar membrane (in concert with the overlying tectorial membrane).

Which cranial nerve transmits auditory information to the brain?

The cochlear branch of the vestibulocochlear nerve (VIII).

Which inner-ear structures detect linear acceleration and gravity?

The utricle and saccule using otoliths.

Which structures detect rotational movements of the head?

The semicircular canals with their ampullae and cristae.

What frequency range can the average human ear detect?

About 20 to 20,000 hertz.

Which cranial nerve carries smell information?

The olfactory nerve (I).

Why are odors closely linked to emotions and memory?

The olfactory cortex is part of the limbic system.

List the five basic taste modalities.

Sweet, salty, sour, bitter, and umami.

Which cranial nerves transmit taste information?

Facial (VII), glossopharyngeal (IX), and vagus (X).

What skin receptors detect temperature changes?

Thermoreceptors (free nerve endings).

Which spinal tract conveys pain signals to the thalamus?

The spinothalamic tract.

How do endogenous opiates such as endorphins reduce pain?

They inhibit the release of substance P, lowering pain signal transmission.

What is referred pain?

Pain from an internal organ perceived as coming from the body surface.

What are proprioceptors? Give three examples.

Receptors informing the CNS about body position; examples:

Muscle spindles detect muscle movement

Golgi tendon organs determine stretch in tendons that attach muscle to bone

Joint receptors detect movement in ligaments

What age-related condition involves loss of lens elasticity for near focus?

Presbyopia.

Which part of the retina lacks rods and cones, creating a blind spot?

The optic disk.

Name the fluids in the cochlear duct and vestibular canal, respectively.

Endolymph in the cochlear duct; perilymph in the vestibular and tympanic canals.

What neurotransmitter do cochlear hair cells release?

Glutamate.

What protective secretion is produced by ceruminous glands in the ear canal?

Cerumen (earwax).