Anatomy and Physiology 2 - Special Senses Study Questions

What are the differences between high-pitched and low-pitched sound, and loud versus quiet sounds?

High-pitched sounds are produced by fast vibrations, resulting in a high frequency, while low-pitched sounds are the result of slower vibrations, leading to a lower frequency. Loud sounds have a greater amplitude, or height of the sound wave, and more energy, while quiet sounds have a smaller amplitude and less energy.

What are the parts of the external ear, and what are their functions?

The external ear consists of two major parts: the pinna (or auricle) and the external auditory canal. The pinna is the visible part of the ear that resides outside of the head. Its function is to collect sound from the environment and direct it into the ear canal. The external auditory canal is a tube running from the outer ear to the middle ear. It carries sound from the pinna to the eardrum. Its lining contains glands that produce cerumen, commonly known as earwax, which helps keep the ear clean and protects it from bacteria and foreign particles.

How is an external ear infection different from a middle ear infection?

Otitis externa or swimmer's ear, is an outer ear infection often caused by trapped water post-swimming, promoting bacterial growth. Symptoms include ear pain, discharge, and possible temporary hearing loss.

Contrarily, otitis media, a middle ear infection behind the eardrum, often results from colds, throat infections, or allergies leading to fluid accumulation. Symptoms include severe ear pain, fever, and hearing loss, and it's more common in children.

Where is the tympanic membrane, and what is it's function?

The tympanic membrane, also known as the eardrum, is located between the outer ear and the middle ear. Its primary function is to transmit sound from the air to the ossicles (small bones) inside the middle ear, and then to the oval window in the fluid-filled cochlea, ultimately converting the sound waves into nerve impulses.

Which parts of the ear (external, middle, inner) are filled with fluid in a healthy person?

In a healthy person, the inner ear, specifically the cochlea and the semicircular canals, are filled with fluid. This fluid aids in the processes of hearing and maintaining balance.

What are the names of the ossicles, where are they located, and what is their function?

The ossicles are three tiny bones in the middle ear, specifically known as the malleus (hammer), incus (anvil), and stapes (stirrup). They are located in the middle ear, between the tympanic membrane (eardrum) and the inner ear. Their primary function is to amplify and transfer sound vibrations from the tympanic membrane to the fluid of the inner ear.

What is the purpose of the auditory (eustachian) tube?

The purpose of the auditory (eustachian) tube is to equalize pressure on both sides of the eardrum. The tube connects the middle ear to the back of the nose and throat, and it opens and closes to allow air to flow in or out. This is especially important during changes in altitude, such as during air travel or when driving in mountains, to prevent discomfort or damage to the eardrum.

What are the different parts and functions of the inner ear?

The inner ear comprises the cochlea, responsible for hearing, and the vestibular system, maintaining balance. The cochlea translates sound vibrations into nerve signals. The vestibular system, including three semicircular canals and the utricle and saccule, detects head movements and position relative to gravity.

What's inside the cochlea?

Inside the cochlea, there are three fluid-filled sections, but the most crucial part for hearing is the middle section, known as the cochlear duct or scala media. This contains the organ of Corti, a structure which has hair cells, the sensory cells of hearing. These hair cells transform the sound vibrations into electrical signals that are then sent to the brain via the auditory nerve.

How does sound stimulate hair cells in the cochlea?

Sound waves enter the ear, causing the eardrum and ossicles to vibrate. These vibrations create a wave in the cochlear fluid, moving the basilar membrane and bending the hair cells' stereocilia. This opens ion channels, generating signals that the auditory nerve sends to the brain, interpreting it as sound.

What is the utricle and saccule of the vestibule, and what do they do?

The utricle and saccule are parts of the inner ear's vestibule. They detect gravity and linear movement, helping maintain balance and spatial orientation.

How do the semicircular canals work?

The semicircular canals are three fluid-filled tubes in the inner ear that help maintain balance. Each canal detects a different movement type: up-down, side-to-side, and tilt. Head movements cause the fluid to shift, moving tiny hair cells. These cells signal the brain about the head's motion, aiding in balance and spatial orientation.

What are the six external eye muscles, and what does each do to the eye?

• The superior and inferior rectus muscles move the eye up and down, respectively.

• The lateral and medial rectus muscles move the eye out and in, respectively.

• The superior and inferior oblique muscles both rotate the eye and move it down and up, respectively.

Which cranial nerves control the external eye muscles?

The cranial nerves that control the external eye muscles are the oculomotor nerve (III), the trochlear nerve (IV), and the abducens nerve (VI).

Which muscles close and open the eye? What about the muscles that control the iris?

The orbicularis oculi muscle closes the eye, while the levator palpebrae superioris muscle opens the eye. The iris, which controls the size of the pupil and thus the amount of light that enters the eye, is controlled by two muscles: the sphincter pupillae contracts to constrict the pupil, and the dilator pupillae contracts to dilate the pupil.

What and where is the conjunctiva?

The conjunctiva is a thin, transparent tissue that covers the inner surface of the eyelid and the white part of the eyeball (sclera). Its primary functions are to keep the eye moist and to help protect it from dust, debris, and infection-causing microorganisms.

What gland produces tears, and how do tears flow into and out of the eye?

The lacrimal gland, located in the upper outer region of the eye socket, produces tears. Tears flow from this gland across the surface of the eye, lubricating and keeping it moist, while helping to remove any dust or debris. Tears then drain into the lacrimal puncta, small openings in the inner corners of the upper and lower eyelids, before flowing through the lacrimal canaliculi into the lacrimal sac and finally draining down the nasolacrimal duct into the nose.

What are the different layers and parts of the eye? What is the function of each?

The human eye is composed of several layers and parts, each with its specific function:

1. Sclera: This is the white outer layer of the eye. It provides protection and serves as an attachment point for the eye muscles.

2. Cornea: This is a transparent layer at the front of the eye that helps focus light onto the retina.

3. Iris: This is the colored part of the eye. It controls the amount of light that enters the eye by adjusting the size of the pupil.

4. Pupil: This is the opening in the center of the iris that allows light to enter the eye.

5. Lens: This is a clear structure located behind the iris and pupil. It focuses light onto the retina.

6. Retina: This is the innermost layer at the back of the eye. It contains photoreceptor cells (rods and cones) that convert light into electrical signals.

7. Rods and Cones: These are photoreceptor cells in the retina. Rods detect light and dark and help with peripheral and night vision. Cones are responsible for color vision and detail.

8. Optic Nerve: This transmits electrical signals from the retina to the brain, where they are interpreted as visual images.

9. Choroid: This is a layer between the retina and sclera, filled with blood vessels that nourish the retina.

10. Macula: This is a small area in the retina that contains a high concentration of cones and is responsible for sharp, central vision.

11. Fovea: This is a tiny pit located in the macula that provides the clearest vision of all.

12. Vitreous Humor: This is a clear, jelly-like substance that fills the space between the lens and the retina, helping to maintain the eye's shape.

What types of fluids fill the eye, and how are they different?

Two types of fluids fill the eye: the aqueous humor and the vitreous humor. The aqueous humor is a clear, watery fluid located in the anterior and posterior chambers of the eye (between the lens and the cornea). It helps maintain intraocular pressure and provides nutrients to the cornea and lens. Vitreous humor is a clear, jelly-like substance located in the large space behind the lens (the vitreous body). It helps maintain the shape of the eye and also helps transmit light to the retina.

How does the ciliary body control the shape of the lens? When is the lens fat? When is the lens thin?

The ciliary body controls the shape of the lens through the zonular fibers (suspensory ligaments). When the ciliary muscle contracts, it releases tension on the zonular fibers, allowing the lens to become thicker (or "fatter"). This happens during near vision. When the ciliary muscle relaxes, tension on the zonular fibers increases, causing the lens to become thinner. This occurs during distant vision.

What is the fovea centralis, and where is it located?

The fovea centralis is a small, pit-like area located within the macula of the retina. This area contains the highest concentration of cone cells and is responsible for sharp, central vision.

What's the difference between rods and cones?

Rods and cones are two types of photoreceptor cells found in the retina. Rods are responsible for vision in low light conditions and peripheral vision but do not perceive color. Cones, on the other hand, are responsible for color vision and function best in bright light conditions.

Describe what causes conditions of the eye like glaucoma, cataracts, and a detached retina.

Glaucoma is caused by increased intraocular pressure damaging the optic nerve. Cataracts are caused by the clouding of the lens, often due to aging or exposure to UV light. A detached retina involves the retina peeling away from the underlying layer of support tissue, which can be caused by trauma, aging, or certain medical conditions.

How does light affect the photoreceptors, the connected bipolar neurons, and the afferent neurons comprising the optic nerve?

Light affects the photoreceptors (rods and cones) by triggering a chemical change that sends an electrical signal to the bipolar neurons. These neurons, in turn, transmit the signal to the ganglion cells. The axons of the ganglion cells converge to form the optic nerve, which carries the visual information to the brain for interpretation.