Test: Sensory System: The Eye - 2 - A Level MCQ

The Range of Human Hearing:
- The range of human hearing refers to the frequencies that can be detected by the human ear.
- It is typically stated to be from 20 Hz to 20 kHz (20,000 Hz).
- This range covers most of the sounds that we encounter in our daily lives, including speech, music, and environmental sounds.
Conductive Hearing Loss:
- Conductive hearing loss occurs when there is a problem with the outer or middle ear that prevents sound from reaching the inner ear.
- If a person has a similar degree of hearing loss for both air conduction and bone conduction, it suggests that the problem is in the middle ear.
- This is because bone conduction bypasses the outer ear and directly stimulates the inner ear, so if there is a problem with the middle ear, it will affect both air and bone conduction.
Sensitivity of the Ear to Frequencies:
- The ear is most sensitive to frequencies between about 100 Hz and 3000 Hz.
- This is known as the speech frequency range because it encompasses the frequencies that are important for speech perception.
- However, the ear can detect frequencies across a much wider range, from 20 Hz to 20 kHz.
Composition of Endolymph:
- The endolymph is the fluid found in the scala media, which is part of the cochlea in the inner ear.
- It is different in composition from plasma, which is the liquid component of blood.
- The endolymph has a high concentration of potassium ions and a low concentration of sodium ions, whereas plasma has the opposite concentration gradient.
- This difference in composition is important for the function of the cochlea in converting sound vibrations into electrical signals that can be interpreted by the brain.
In conclusion, the correct statement is A: The range of human hearing is from 20 Hz to 20 kHz.

The eustachian tube is a canal that connects the middle ear to the nasopharynx, which consists of the upper throat and the back of the nasal cavity. It controls the pressure within the middle ear, making it equal with the air pressure outside the body.

The ear ossicles are three bones present in middle ear, they are among the smallest bones in the human body. They serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea).
Arrangement of ear ossicles, starting from ear drum is the malleus, incus, and stapes, shapes resembles of the hammer, anvil, and stirrup respectively.
As sound waves vibrate the tympanic membrane (eardrum), it in turn moves the nearest ossicle, the malleus, to which it is attached. The malleus then transmits the vibrations, via the incus, to the stapes, and so ultimately to the membrane of the fenestra ovalis, the opening to the vestibule of the inner ear. Hence option B is correct.

Organ of Corti
The Organ of Corti is a structure found in the internal ear. It is responsible for converting sound vibrations into electrical signals that can be interpreted by the brain. Here are the details:
Location:
The Organ of Corti is located within the cochlea of the inner ear. The cochlea is a snail-shaped structure filled with fluid and is responsible for our sense of hearing.
Anatomy:
The Organ of Corti consists of several key components:
1. Hair Cells: These are the sensory cells of the Organ of Corti. They are arranged in rows and have hair-like projections called stereocilia. When sound vibrations enter the cochlea, the stereocilia move, triggering electrical signals in the hair cells.
2. Tectorial Membrane: This is a gel-like structure that rests on top of the hair cells. When sound vibrations pass through the cochlea, they cause the tectorial membrane to move, further stimulating the hair cells.
3. Supporting Cells: These cells surround and support the hair cells, providing structural support and assisting in their function.
4. Nerve Fibers: The electrical signals generated by the hair cells are transmitted to the brain through nerve fibers, where they are interpreted as sound.
Function:
The Organ of Corti is responsible for the transduction of sound waves into electrical signals. When sound enters the ear, it causes vibrations in the fluid-filled cochlea. These vibrations are then detected by the hair cells in the Organ of Corti, which convert them into electrical signals that can be interpreted by the brain as sound.
In conclusion, the Organ of Corti is found in the internal ear, specifically within the cochlea. It plays a crucial role in our sense of hearing by converting sound vibrations into electrical signals.

The ears of the human body have two important functions. They help in collecting sound waves from the surrounding areas, transmitting and transducing them. They also help to maintain balance.

As the sound travels through the perilymph, it moves the endolymph in the cochlear duct. Movements of the endolymph move the tectorial membrane, which is attached to the sensory hairs of hair cells in the organ of Corti. The hair cells are attached to the basilar membrane, which also moves with the sound vibrations. The semicircular canals contain three main parts: the horizontal, posterior, and superior canals. Each of these canals provides a separate sense of directional balance. The superior canal detects head rotations on the anterior-posterior axis. The posterior canal detects rotations on the saggital plane. The horizontal canal senses movement on a vertical basis, as the head rotates up-and-down on the neck.

A cross section of the cochlea illustrating the organ of Corti. The organ of Corti, or spiral organ, is the receptor organ for hearing and is located in the mammalian cochlea. This highly varied strip of epithelial cells allows for transduction of auditory signals into nerve impulses' action potential.

Organ of Corti in Rabbit and its Function
The Organ of Corti is a structure located in the cochlea, which is a spiral-shaped structure in the inner ear. It plays a vital role in the sense of hearing. In the case of rabbits, the Organ of Corti is also involved in the auditory system.
Function of the Organ of Corti in Rabbit
The Organ of Corti is responsible for converting sound vibrations into electrical signals that can be interpreted by the brain. It contains specialized sensory hair cells that detect sound waves and transmit the information to the auditory nerve. Here is a detailed explanation of its function:
- Transduction of Sound Waves: The Organ of Corti contains hair cells that are arranged in rows along the basilar membrane. These hair cells have specialized structures called stereocilia that protrude into the fluid-filled cochlea.
- Detection of Sound Vibrations: When sound waves enter the ear, they cause the fluid in the cochlea to vibrate. These vibrations are then picked up by the stereocilia of the hair cells in the Organ of Corti.
- Mechanical to Electrical Signal Conversion: The movement of the stereocilia due to the vibrations causes the hair cells to bend. This bending triggers the opening of ion channels, leading to the generation of electrical signals.
- Transmission to Auditory Nerve: The electrical signals generated by the hair cells are transmitted to the auditory nerve fibers, which carry the information to the brain for interpretation.
- Frequency Discrimination: The Organ of Corti is also responsible for differentiating between different frequencies of sound. The basilar membrane, along with the hair cells, exhibits a tonotopic organization, meaning that different regions of the cochlea are sensitive to different frequencies.
Conclusion
In conclusion, the Organ of Corti in rabbits is primarily concerned with the sense of hearing. It plays a crucial role in converting sound vibrations into electrical signals and transmitting them to the brain for interpretation.

Structure that helps a person to maintain equilibrium:
Semicircular canal:
- The semicircular canals are a part of the inner ear and are responsible for maintaining balance and equilibrium.
- There are three semicircular canals: the anterior, posterior, and lateral canals. Each canal is positioned at a different angle to detect movement in different planes.
- The canals are filled with fluid and contain hair cells that are sensitive to motion. When the head moves, the fluid in the canals moves as well, causing the hair cells to bend and send signals to the brain.
- The brain then processes these signals to help maintain the body's balance and posture.
- The semicircular canals are particularly important in detecting rotational movements, such as turning the head or spinning.
Other structures:
- While the semicircular canals play a significant role in maintaining equilibrium, there are other structures involved as well. These include:
- The cochlea, which is responsible for hearing and does not directly contribute to balance.
- The eustachian tube, which helps equalize pressure between the middle ear and the environment. While it does not directly contribute to equilibrium, it can indirectly affect balance if there is an imbalance in pressure.
- The hammer-like bone (also known as the malleus), which is one of the three small bones in the middle ear. It transmits sound vibrations from the eardrum to the inner ear but does not directly contribute to balance or equilibrium.
In conclusion, the semicircular canal is the structure that specifically helps a person to maintain equilibrium. It detects rotational movements and sends signals to the brain to help maintain balance and posture. Other structures like the cochlea, eustachian tube, and hammer-like bone have different functions related to hearing and pressure equalization but do not directly contribute to equilibrium.

Explanation:
The cochlea is a spiral-shaped structure located in the inner ear of mammals. It is primarily responsible for hearing and plays a crucial role in the auditory system. Here is a detailed explanation of the cochlea's function:
1. Structure:
- The cochlea is a coiled, snail-like structure that is divided into three fluid-filled compartments: the scala vestibuli, the scala media, and the scala tympani.
- It is lined with sensory hair cells and contains the organ of Corti, which is responsible for converting sound vibrations into electrical signals that can be interpreted by the brain.
2. Hearing:
- The primary function of the cochlea is to convert sound waves into electrical signals that can be interpreted by the brain.
- Sound waves enter the cochlea through the oval window, causing fluid inside the cochlea to move and stimulate the sensory hair cells.
- The movement of the hair cells triggers the release of neurotransmitters, which then send electrical signals to the auditory nerve.
- The auditory nerve carries these signals to the brain, where they are processed and interpreted as sound.
In conclusion, the cochlea of the mammalian ear is primarily concerned with hearing. It is responsible for converting sound waves into electrical signals that can be interpreted by the brain.

Different Function of the Malleus Bone
The malleus bone, also known as the hammer bone, is one of the three small bones in the middle ear. It plays a crucial role in the process of hearing and has a different function compared to other bones in the body.
Function of the Malleus Bone:
- Transmit Sound Waves: The malleus bone, along with the incus and stapes bones, forms the ossicles in the middle ear. Its primary function is to transmit sound waves from the eardrum to the inner ear. This process is essential for converting sound vibrations into electrical signals that the brain can interpret.
Comparison to Other Bones:
- Ribs: Ribs provide support and protection to vital organs such as the heart and lungs. They do not have a direct role in the process of hearing like the malleus bone.
- Atlas Vertebra: The atlas vertebra, also known as the C1 vertebra, supports the skull and allows for nodding and rotation of the head. It does not play a role in hearing.
- Radius: The radius is one of the two long bones in the forearm and is involved in the movement of the arm and hand. It does not participate in the process of hearing like the malleus bone.
Conclusion:
While all bones provide support and protection to body parts, the malleus bone has a unique function related to the process of hearing. It transmits sound waves from the eardrum to the inner ear, allowing us to perceive and interpret sounds.

External Ear Characteristics in Mammals:
- Mammals have a distinct external ear, also known as the pinna or auricle.
- The external ear consists of a cartilaginous structure covered in skin.
- It is responsible for capturing sound waves and directing them into the ear canal.
- The shape and size of the external ear can vary greatly among different mammalian species.
- The external ear helps mammals in sound localization, allowing them to determine the direction of sound sources.
- The external ear also aids in the protection of the eardrum and middle ear from foreign objects and excessive noise.
Comparison with Other Animal Groups:
- Reptiles: Reptiles typically lack a well-developed external ear. They rely more on vibrations and bone conduction to detect sound.
- Amphibians: Amphibians also lack a prominent external ear. They have a thin layer of skin covering their ear openings, which helps in sound perception.
- Fishes: Fishes do not possess a pinna or external ear structure. They rely on their lateral line system and inner ear to detect sound and vibrations in water.
Conclusion:
The presence of a distinct external ear is characteristic of mammals. It plays a crucial role in sound reception, localization, and protection of the inner ear. This feature sets mammals apart from other animal groups such as reptiles, amphibians, and fishes.

The correct answer is D: 20-20,000 cycles/sec.
Explanation:
- Sound waves are vibrations that travel through a medium, such as air, and are detected by our ears.
- The frequency of a sound wave refers to the number of cycles or vibrations the wave completes in one second. It is measured in hertz (Hz).
- The range of human hearing is typically between 20 and 20,000 cycles/sec, also known as 20 Hz to 20 kHz.
- Frequencies above 20,000 cycles/sec are referred to as ultrasonic and are generally not detectable by the human ear.
- Frequencies below 20 cycles/sec are referred to as infrasonic and are also not typically detectable by the human ear.
- Therefore, our ears can hear sound waves within the frequency range of 20-20,000 cycles/sec, making option D the correct answer.

Answer:
The Eustachian tube is a connection between the middle ear and the pharynx. It plays a crucial role in regulating the pressure in the middle ear and allowing for the equalization of pressure on both sides of the eardrum.
The Eustachian tube is found in a variety of animals, but it is not present in all vertebrates.
Here is a breakdown of the options:
1. All the land vertebrates in general: This option is correct. The Eustachian tube is found in all land vertebrates, including mammals, reptiles, and birds. It allows for the equalization of pressure in the middle ear when these animals are on land.
2. All vertebrates: This option is incorrect. While the Eustachian tube is found in many vertebrates, it is not present in all of them. For example, fish do not have a Eustachian tube.
3. Amphibians only: This option is incorrect. While amphibians do have a Eustachian tube, it is not exclusive to them. It is found in other vertebrates as well.
4. Mammals only: This option is incorrect. While mammals do have a Eustachian tube, it is not exclusive to them. It is also found in other vertebrates.
In conclusion, the correct answer is A: All the land vertebrates in general. The Eustachian tube is a common anatomical feature in these animals and plays an important role in regulating pressure in the middle ear.

The ear is divided into three parts- the outer ear, the middle ear and the inner ear. The outer ear consists of the pinna, the external auditory meatus or auditory canal and the tympanic membrane.

• The tympanic membrane is also known as the eardrum.
• It is a part of the outer ear and is situated at the end of the external auditory meatus or auditory canal.
• It is made of connective tissue and skin.

Answer:
The cochlea is a spiral-shaped, fluid-filled structure located in the inner ear. It is responsible for converting sound vibrations into electrical signals that can be interpreted by the brain. The cochlea contains several important components, including the scala vestibule, scala tympani, and scala media.
- Scala vestibule: This is the upper chamber of the cochlea, situated above the scala media. It is filled with perilymph, a fluid that helps transmit sound vibrations through the cochlea.
- Scala tympani: This is the lower chamber of the cochlea, located below the scala media. It is also filled with perilymph and plays a role in transmitting sound vibrations.
- Scala media: Also known as the cochlear duct, this is the middle chamber of the cochlea. It is filled with endolymph, a fluid that contains special sensory cells called hair cells. These hair cells are responsible for converting sound vibrations into electrical signals that can be sent to the brain for processing.
Therefore, the correct answer is D: All of the above. The cochlea contains the scala vestibule, scala tympani, and scala media, all of which are essential for the process of hearing.

The Structure of Human Ear Involved in Perceiving Sound Waves
The structure of the human ear responsible for perceiving sound waves and transmitting them to the brain is the sensory hair cells of the organ of Corti, located in the cochlea. Here is a detailed explanation of how this process occurs:
1. Sound Waves
- Sound waves are produced by vibrating objects and travel through the air as a series of compressions and rarefactions.
- These sound waves enter the ear through the external auditory canal and reach the eardrum (tympanic membrane).
2. Tympanic Membrane
- The sound waves cause the tympanic membrane to vibrate.
- The tympanic membrane amplifies and transmits these vibrations to the middle ear.
3. Middle Ear
- The vibrations from the tympanic membrane are transferred to the three ossicles in the middle ear: the malleus (hammer), incus (anvil), and stapes (stirrup).
- The ossicles amplify the vibrations and transmit them to the inner ear.
4. Inner Ear
- The stapes is connected to the oval window, which separates the middle ear from the fluid-filled cochlea in the inner ear.
- The vibrations from the ossicles cause the fluid in the cochlea to move, specifically in the scala vestibuli.
5. Organ of Corti
- The movement of the fluid in the cochlea causes the basilar membrane within the organ of Corti to vibrate.
- The sensory hair cells, located on the basilar membrane, are stimulated by these vibrations.
6. Stimulation of Sensory Hair Cells
- The sensory hair cells have tiny hair-like structures called stereocilia on their surface.
- When the basilar membrane vibrates, it causes the stereocilia to bend.
7. Generation of Electrical Signals
- The bending of the stereocilia opens ion channels in the sensory hair cells.
- This allows ions to enter the cells, generating electrical signals.
8. Transmission to the Brain
- The electrical signals generated by the sensory hair cells are transmitted to the auditory nerve fibers.
- The auditory nerve fibers then carry these signals to the brain, specifically to the auditory cortex in the temporal lobe.
- The brain processes and interprets these signals as sound.
Therefore, the correct answer is D: Sensory hair cells of the organ of Corti. These hair cells play a crucial role in converting mechanical vibrations into electrical signals, which are then transmitted to the brain for perception of sound.

Answer:
Ear ossicles:
- Ear ossicles are tiny bones located in the middle ear that play a crucial role in transmitting sound vibrations from the eardrum to the inner ear.
- There are three ear ossicles: the malleus, incus, and stapes.
- These bones are connected in a chain-like structure, with the malleus attached to the eardrum, the incus in the middle, and the stapes connected to the inner ear.
The correct answer is C:
- The humerus is not an ear ossicle.
- The humerus is a long bone located in the upper arm, not involved in hearing.
- It forms part of the shoulder and elbow joints.
Summary:
- The three ear ossicles are the malleus, incus, and stapes.
- The humerus is not an ear ossicle, but a bone in the upper arm.
- The correct answer is C: Humerus.

The sacculus, or saccule, is a chamber of the inner ear from which the cochlea arises in reptiles, birds, and mammals. It has patches of sensory epithelium that are concerned with balance.

Membranous labyrinth are the groups of fluid-filled membranous sacs of the inner ear, that are associated with the senses of hearing and balance.

Ceruminous glands are specialized sudoriferous glands (sweat glands) located subcutaneously in the external auditory canal. Ceruminous glands are simple, coiled, tubular glands made up of an inner secretory layer of cells and an outer myoepithelial layer of cells. The glands drain into larger ducts, which then drain into the guard hairs that reside in the external auditory canal.

• The pinna is the portion of the ear which is visible on the body.
• It is a part of the outer ear along with the external auditory meatus or auditory canal and the tympanic membrane or eardrum.

Organ of Corti is located in the Scala Media of the Cochlea.
Explanation:
The Organ of Corti is a specialized structure located within the cochlea of the inner ear. It is responsible for converting sound vibrations into electrical signals that can be interpreted by the brain.
The cochlea is a spiral-shaped structure in the inner ear that is responsible for hearing. It is divided into three fluid-filled chambers called scalae: the Scala Vestibuli, the Scala Media, and the Scala Tympani.
The Scala Media, also known as the cochlear duct, is the middle chamber of the cochlea. It is filled with endolymph, a fluid that helps in the transmission of sound vibrations. The Organ of Corti is located within the Scala Media.
The Organ of Corti is composed of specialized hair cells called sensory hair cells. These hair cells are arranged in rows and are responsible for detecting sound vibrations. When sound waves enter the cochlea, they cause the fluid within the Scala Media to move, which in turn causes the hair cells to bend. This bending of hair cells triggers the generation of electrical signals that are sent to the brain for interpretation.
In summary, the Organ of Corti is located within the Scala Media of the cochlea. It plays a vital role in converting sound vibrations into electrical signals for auditory perception.

Otolith (otoconia) are CaCO₃ particles found in:
- Endolymph: Otoliths are calcium carbonate (CaCO₃) particles that are found in the inner ear within a structure called the vestibule. The vestibule contains the utricle and saccule, which are responsible for detecting linear acceleration and head position. Otoliths are embedded in a gelatinous matrix within the utricle and saccule and play a crucial role in sensing gravity and linear movements.
- Perilymph, Bones, and Vitreous humor are not the correct answers:
- Perilymph: Perilymph is a fluid that fills the space between the bony labyrinth and the membranous labyrinth in the inner ear. It helps transmit sound vibrations and plays a role in balance.
- Bones: Otoliths are not found in bones. Bones primarily consist of collagen and calcium phosphate, not calcium carbonate.
- Vitreous humor: Vitreous humor is a gel-like substance that fills the space between the lens and the retina in the eye. It helps maintain the shape of the eye.
Therefore, the correct answer is B: Endolymph. Otoliths are calcium carbonate particles found in the endolymph within the utricle and saccule of the inner ear.

Answer:
The anvil-shaped ear ossicle mentioned in the question refers to one of the three small bones in the middle ear that transmit sound vibrations from the eardrum to the inner ear. The correct answer is A: Incus.
Here is a detailed explanation:
1. Incus:
The incus, also known as the anvil, is one of the three ossicles in the human ear. It is located between the malleus (hammer) and the stapes (stirrup) in the middle ear. The incus has a distinctive anvil-like shape, hence its name. It plays a vital role in transmitting sound vibrations from the malleus to the stapes.
2. Malleus:
The malleus, also known as the hammer, is another one of the three ossicles in the middle ear. It is the first bone in the ossicular chain and is attached to the eardrum. The malleus receives vibrations from the eardrum and passes them on to the incus.
3. Stapes:
The stapes, also known as the stirrup, is the third and smallest of the three ossicles. It is connected to the incus and rests against the oval window of the cochlea. The stapes transmits the sound vibrations received from the incus to the fluid-filled inner ear.
4. Humerus:
The humerus is a bone in the human arm, specifically in the upper arm. It is not part of the ear ossicles and is unrelated to the question.
Therefore, the correct answer to the question is A: Incus.

Stirrup Shaped Ear Ossicle:
The stirrup-shaped ear ossicle is known as the Stapes. Let's break down the details to understand it better:
1. Incus:
- The incus is one of the three small bones, also known as ossicles, found in the middle ear.
- It connects the malleus (hammer) to the stapes (stirrup).
- The incus is anvil-shaped, not stirrup-shaped.
2. Stapes:
- The stapes is the smallest and lightest bone in the human body.
- It is shaped like a stirrup, hence its name.
- The stapes is connected to the incus on one end and the oval window of the inner ear on the other end.
- Its movement transmits sound vibrations from the middle ear to the inner ear.
3. Malleus:
- The malleus, also known as the hammer, is another one of the three ossicles in the middle ear.
- It is attached to the eardrum (tympanic membrane) and is shaped like a hammer.
- The malleus transmits sound vibrations from the eardrum to the incus.
4. Humerus:
- The humerus is a bone found in the upper arm of humans.
- It is not part of the ear ossicles, and it is not stirrup-shaped.
Therefore, the correct answer is B. Stapes, as it is the stirrup-shaped ear ossicle.

The muscles that move the pinnae (external part of the ear) in humans are vestigial. Here's a detailed explanation:
1. Absent: This option is incorrect because humans do have muscles that are responsible for moving the pinnae. These muscles are not completely absent.
2. Vestigial: This is the correct answer. The muscles that control the movement of the pinnae in humans are vestigial, which means they are present but have lost their original function over time. In our evolutionary history, these muscles were used to help orient the ears towards the source of sound, much like other animals. However, as humans have evolved, the pinnae have become less mobile and less important for sound localization. Thus, the muscles associated with moving the pinnae have also become less developed and functional.
3. Functional more: This option is incorrect because the muscles that move the pinnae in humans are not more functional. They are actually vestigial and have limited mobility compared to other animals.
4. Functional: This option is incorrect because the muscles that move the pinnae in humans are not fully functional. They have limited mobility and are considered vestigial.
In conclusion, the muscles that move the pinnae in humans are vestigial, meaning they have lost their original function and have limited mobility compared to other animals.

The external consists of an external flap, and auditory canal and is commonly called as pinna. External ears are present in all mammals except monotremes , a feature that links them with birds. Many mammals can move the external ear by its own and associated muscles to capture the4 maximum amplitude of sound waves and to discriminate between different sources of sound.
13.(1836864) Thalamus is not the part of the hindbrain. 
Hindbrain is also called rhombencephalon, a region of the developing vertebrate brain is composed of the medulla oblongata, the pons, and the cerebellum.
It is a limbic system structure that connects areas of the cerebral cortex that are involved in sensory perception and movement with other parts of the brain and the spinal cord.