Sensory Receptors: Functions, Classifications, and Pathways in Human Senses

What are the general functions of sensory receptors?

To detect and respond to stimuli from the environment, converting them into neural signals.

How do sensory receptors act as transducers?

They convert different forms of energy (like light, sound, or chemical signals) into electrical impulses.

What is a receptive field?

The area in which a sensory receptor can detect stimuli; its size affects the localization of the stimulus.

What is sensory adaptation?

The process by which sensory receptors become less sensitive to constant stimuli over time.

What is the difference between tonic and phasic receptors?

Tonic receptors maintain their response to a stimulus over time, while phasic receptors respond quickly but adapt and cease firing.

How are sensory receptors classified by stimulus origin?

They are classified as exteroceptors (external stimuli), interoceptors (internal stimuli), and proprioceptors (body position).

What is the difference between somatic and visceral sensory receptors?

Somatic receptors detect external stimuli from the skin and muscles, while visceral receptors monitor internal organ conditions.

What are the major types of sensory receptors based on modality?

Mechanoreceptors, thermoreceptors, photoreceptors, chemoreceptors, and nociceptors.

What is referred pain?

Pain perceived at a location other than the site of the painful stimulus, significant for diagnosing internal organ issues.

What is olfaction?

The sense of smell, with olfactory organs located in the nasal cavity.

What are the three types of cells found in the olfactory epithelium?

Olfactory receptor cells, supporting cells, and basal cells.

What is the function of olfactory receptor cells?

To detect odor molecules and initiate the sense of smell.

Describe the olfactory pathway from receptor to brain.

Olfactory receptor cells send signals to the olfactory bulb, which then transmits information to the olfactory cortex.

What role does the olfactory bulb play in smell perception?

It processes olfactory information and relays it to other brain areas for interpretation.

How does olfactory discrimination occur?

Through the activation of different combinations of olfactory receptors by various odorants.

What is gustation?

The sense of taste, with taste buds located primarily on the tongue.

What are the five basic taste sensations?

Sweet, sour, salty, bitter, and umami.

What are the three types of cells found in taste buds?

Gustatory receptor cells, supporting cells, and basal cells.

Describe the gustatory pathway from taste receptor to brain.

Taste receptors activate sensory neurons that transmit signals to the brain via cranial nerves.

What cranial nerves are involved in taste sensation?

The facial nerve (VII), glossopharyngeal nerve (IX), and vagus nerve (X).

What are the three tunics of the eye?

The fibrous tunic, vascular tunic, and retina, each serving different functions in vision.

What are the components of the fibrous tunic?

The sclera and cornea.

What are the components of the vascular tunic?

The choroid, ciliary body, and iris.

What is the function of the pupil?

To regulate the amount of light entering the eye, controlled by the iris.

What are rods and cones?

Photoreceptors in the retina; rods detect low light levels, while cones are responsible for color vision.

What is the fovea centralis?

A small pit in the retina that provides the clearest vision due to a high concentration of cones.

What is the optic disc?

The point where the optic nerve exits the eye, creating a blind spot due to lack of photoreceptors.

What is the function of the lens?

To focus light onto the retina by changing shape through ciliary muscle contraction.

Describe the visual pathway from photoreceptors to the brain.

Light is converted into electrical signals by photoreceptors, which travel through the optic nerve to the visual cortex.

What is the role of the optic chiasm in vision?

To allow the crossing of optic nerve fibers, enabling visual information from both eyes to be processed together.

What are the three regions of the ear?

The outer ear, middle ear, and inner ear, each with distinct functions in hearing and balance.

What is the function of the auricle?

To collect sound waves and direct them into the external acoustic meatus.

What is the role of the tympanic membrane?

To vibrate in response to sound waves, transmitting sound to the ossicles.

Name the auditory ossicles.

Malleus, incus, and stapes, which transmit sound vibrations from the tympanic membrane to the inner ear.

What is the function of the auditory (Eustachian) tube?

To equalize pressure in the middle ear with atmospheric pressure.

What structures are found in the cochlea?

The organ of Corti, hair cells, and fluid-filled chambers.

Describe the pathway of sound from the external ear to the cochlea.

Sound waves travel through the external ear, vibrate the tympanic membrane, and are transmitted through the ossicles to the cochlea.

What is the function of the organ of Corti?

To convert sound vibrations into neural signals through hair cell activation.

Describe the auditory pathway from cochlear nerve to auditory cortex.

Signals travel from the cochlear nerve to the brainstem, then to the thalamus, and finally to the auditory cortex.

What structures detect equilibrium?

The vestibule and semicircular canals in the inner ear.

What is the function of the vestibule?

To detect static equilibrium and linear acceleration.

What is the role of the maculae in static equilibrium?

To sense the position of the head relative to gravity.

How do the crista ampullaris and cupula function in dynamic equilibrium?

They detect rotational movements of the head through fluid movement in the semicircular canals.

Describe the equilibrium pathway from vestibular receptors to the brain.

Signals from vestibular receptors travel through the vestibular nerve to the brainstem and cerebellum.

How do the special senses integrate with the central nervous system?

Through neural pathways that connect sensory receptors to specific brain regions for processing.

What are common disorders associated with each special sense?

Examples include hearing loss, taste disorders, olfactory dysfunction, and vision impairments.

How does damage to cranial nerves affect sensory perception?

It can lead to loss or alteration of sensory functions, such as taste or smell.

What diagnostic tools are used to assess sensory system function?

Tools include audiometers for hearing, olfactometers for smell, and visual field tests for sight.

How do aging and disease affect the special senses?

They can lead to diminished sensitivity, loss of function, and increased risk of disorders in sensory systems.