Special Senses: Audition, Vestibular Perception, Olfaction, and Gustation

A comprehensive set of practice flashcards covering audition, vestibular perception, olfaction, and gustation based on the lecture transcript.

What are the two major characteristics of sound, and how are they measured?

Amplitude, which is intensity measured in decibels ($dB$) for loudness, and Frequency, which is the number of cycles per second measured in hertz ($Hz$) for pitch.

What is the human range of hearing in terms of frequency?

$$20-20,000\,Hz$$

What are the primary structures of the middle ear?

Tympanic membrane, ear ossicles, oval and round windows, tensor tympani, and stapedius.

Which specific area in the inner ear serves as the sensory organ for hearing?

The cochlea, containing receptor cells in the Organ of Corti.

What are the three fluid-filled compartments of the cochlea?

Scala vestibuli (entrance for sound vibrations), Scala media (houses the Organ of Corti), and Scala tympani.

What are the roles of the two types of hair cells in the Organ of Corti?

Inner hair cells are responsible for sound transduction, while outer hair cells "tune" the organ and do not detect sound.

Which cranial nerve transmits sensory information from the Organ of Corti to the brain?

Vestibulocochlear nerve ($CN\,VIII$).

During auditory transduction, what determines the influx of $K^+$ and $Ca^{2+}$ into a hair cell?

Vibrations reach the basilar membrane, displacing stereocilia under the tectorial membrane, which increases tension on tip links to open attached ion channels.

How do outer hair cells respond to changes in membrane potential?

Hyperpolarization causes them to lengthen by $5\%$, while depolarization causes them to shorten; this continuously changes the stiffness of the basilar membrane.

Where on the basilar membrane are high-frequency and low-frequency sounds processed?

High-frequency sounds (up to $20,000\,Hz$) are processed at the base (near the oval window), while low-frequency sounds (down to $20\,Hz$) are processed at the apex.

What is the sequence of the primary auditory pathway after the cochlea?

Cochlear nucleus (medulla), Superior olivary nucleus (pons), Inferior colliculus (midbrain), Medial geniculate nucleus (thalamus), and Primary auditory cortex (temporal lobe).

What are the two primary mechanisms for localizing sounds?

Intensity differences (loudness) and Latency differences (time of arrival).

In the superior olive, what are the specific functions of the Lateral superior olive (LSO) and Medial superior olive (MSO)?

The LSO processes interaural intensity differences, and the MSO processes interaural time differences.

In the left cerebral hemisphere, what is the role of Wernicke’s area regarding sound?

Speech recognition.

What characterizes conduction deafness?

Interference preventing sound waves from reaching the cochlea, such as the fusion of ossicles, with no CNS involvement.

What is sensorineural deafness?

Hearing loss where auditory nerve fibers cannot fire, usually caused by damaged hair cells or cochlear nerve dysfunction, and is typically permanent.

What causes central deafness, and what are two examples?

It is caused by brain lesions like a stroke; examples include word deafness and cortical deafness.

Which types of medications are known to be ototoxic?

Aminoglycoside antibiotics (gentamycin, kanamycin, streptomycin) and ethacrynic acid.

What is the cause of Presbyacusis?

Hearing loss associated with aging due to damage of the microvasculature of the inner ear.

What are the primary functions of the vestibular system?

Perception of self-motion, head position, and spatial orientation relative to gravity by measuring linear and angular acceleration.

What are the five receptor organs of the vestibular system located in the inner ear?

Three semicircular canals (Anterior, Posterior, Lateral), the utricle, and the saccule.

What type of movement do the utricle and saccule detect?

Straight line (linear) acceleration and deceleration.

What are otoconia?

Tiny crystals embedded on the otolithic membrane within the utricle and saccule.

What structure in the semicircular canals contains hair cells within a gelatinous mass called the cupula?

The ampulla.

What types of rotation correspond to the x, y, and z axes in the semicircular canals?

Pitch (x-axis), Yaw (y-axis), and Roll (z-axis).

What are the targets of the vestibulocochlear nerve ($CN\,VIII$) in the brain's vestibular pathway?

The vestibular nuclei of the pons, which then project to the Thalamus, Spinal cord, Motor nuclei of the eye, and Cerebellum.

What is the sense of spinning called?

Vertigo.

What is a Vestibular Schwannoma?

A Schwann cell tumor on the vestibular nerve that affects balance and may impinge on cranial nerves $V$ and $VII$.

What occurs in Meniere’s Disease?

An increase in endolymph leads to damage of the cochlea and vestibular apparatus, causing continuous vertigo and hearing loss.

Why is olfaction considered the oldest sensory system from an evolutionary perspective?

It is linked to visceral motor responses (salivation, gagging), endocrine functions (synchronizing menstrual cycles), and reproduction.

What are the sensory receptors for smell, and where are they located?

Olfactory receptor neurons (ORNs), located in the olfactory mucosa.

Where do the axons of the olfactory receptor neurons (ORNs) synapse?

They synapse in the glomeruli of the olfactory bulb onto mitral cells and tufted cells.

Match the higher brain centers for olfaction with their functions: Pyriform cortex, Amygdala, and Hippocampus.

Pyriform cortex (olfactory processing), Amygdala (visceral/sexual behaviors), and Hippocampus (olfactory-guided memories).

What is Anosmia and what are some common causes?

The inability to smell; causes include chronic sinus infection, head trauma, toxins, aging, and neurodegenerative diseases.

What are the five basic tastes?

Sweet, Savory (umami), Salty, Sour, and Bitter.

Where are taste receptors (epithelial taste cells) located?

Inside taste buds, which are found on papillae (circumvallate, foliate, and fungiform).

Which receptors and tongue regions correspond to Sweet and Bitter tastes?

Sweet uses $T1R2$ receptors on the anterior tongue; Bitter uses $T2R$ receptors on the back of the tongue.

What causes the perception of Sour and Umami tastes?

Sour is due to $H^+$ through TRP channels; Umami is savory and due to glutamate acting on $T1R1$ receptors.

Which three cranial nerves carry taste information from the tongue, soft palate, pharynx, and esophagus?

Facial nerve ($CN\,VII$), Glossopharyngeal nerve ($CN\,IX$), and Vagus nerve ($CN\,X$).

To which nucleus in the medulla do cranial nerves transmit taste and visceral sensations?

The gustatory nucleus (nucleus of the tractus solitarius).