BIO 111 CHP 10: The Senses

What are the general senses?

Considered widely disturbed and structurally simple.

• Touch, pressure, temperature and pain.

What are the special senses?

Considered to have complex, specialized sensory organs in the head.

• Vision, hearing, smell taste, and balance.

What are the protective structures of the eye?

Eyelid and lacrimal apparatus.

What is the sclera? Which tunic is this?

• White, fibrous outer layer of the wall of the eye; part of the fibrous tunic (outermost layer).

What is the cornea?

• Transparent anterior portion of the outer layer of the wall of the eye; Bends light, protects the eye, and filters out UV rays.

What is the lens?

• Structure in the eyeball responsible for focusing light rays onto the retina.

What is the choroid layer? Which tunic is this?

• Vascular, pigmented middle layer of the wall of the eye; belongs to the vascular tunic of the eye, also known as the uvea.

• supplying oxygen and nutrients to the outer retina, absorbing stray light to enhance visual clarity, and regulating temperature and fluid pressure within the eye.

What is the iris?

Colored, muscular part of the eye around the pupil that regulates its size.

What is the pupil?

Opening in the iris through which light enters the eye.

What is the retina? Which tunic is the retina?

Inner layer of the wall of the eye that includes the visual receptors; makes up the neural tunic (innermost layer)

Rods-

Type of light receptor that provides colorless (grayscale) vision.

Cones:

Type of light receptor that provides color vision.

Optic nerve

• Cranial nerve II. Provides sensory input from the retina for vision.

Blind spot-

small, light-insensitive area on the retina known as the optic disc

Fovea

a tiny, cone-rich pit located in the exact center of the eye's macula. It is responsible for our sharpest, most detailed central vision

Aqueous humor

Watery fluid that fills the anterior cavity of the eye.

Vitreous humor

Fluid between the lens and the retina of the eye.

List the structures in the pathway of light through the eye:

Cornea, aqueous humor, pupil, lens, vitreous humor, retina, optic nerve

Optic Nerve (CN II):

Transmits visual signals and interprets light.

Oculomotor Nerve (CN III):

Controls most eye muscles, eyelid movement, and pupil constriction.

Trochlear Nerve (CN IV):

Controls the superior oblique muscle, enabling downward and inward eye movement.

Trigeminal Nerve (CN V):

Specifically the ophthalmic branch; handles sensory input from the eyes, such as blinking reflexes.

Abducens Nerve (CN VI):

Controls the lateral rectus muscle, allowing the eyes to look side-to-side

Facial Nerve (CN VII):

Controls the muscles responsible for eye closure and tearing/lacrimation.

Wall of eye layers:

outer (fibrous) layer, middle (vascular) layer, and inner (nervous) layer.

What is normal vision/emmetropia?

normal vision, due to normal eye shape; light waves focus sharply on the retina

What is hyperopia?

Farsightedness; light rays focus in back of retina, but are not yet converged when they reach retina

What is myopia?

Nearsightedness; light rays focus in front of retina, and then scatter, causing blurry image

What is astigmatism?

eye condition caused by an irregular shape of the eye's cornea or lens.

What are mechanoreceptors?

Sensory receptors sensitive to mechanical stimulation, such as changes in pressure or tension.

Auricle/pinna:

An outpouching of the wall of an atrium of the heart. (outer ear)

External Acoustic meatus/External auditory canal:

Canal that leads from the outer ear to the eardrum. (outer ear)

Eardrum/Tympanic membrane:

Thin membrane that is part of the external ear; separates the external ear from the middle ear. (outer ear)

Middle ear (tympanic cavity):

Air filled space in the temporal bone.

What are the auditory ossicles in the middle ear?

malleus, incus, and stapes

Oval window:

Opening in the inner ear to which the stapes attaches.

Auditory tube/ Eustachian tube:

Tube that connects the middle ear cavity to the pharynx

Inner ear:

labyrinth; a communicating network of chambers and tubes.

Bony/osseus labyrinth:

Cavity within the temporal bone with bony passages filled with perilymph.

Membranous labyrinth:

Continuous series of sacs and ducts filled with endolymph

Cochlea:

Portion of inner ear that has hearing receptors; functions in hearing

Organ of Corti:

• Also called the spiral organ; Structure in the cochlea that contains hearing receptors called hair cells.

• The structure resting on the basilar membrane where mechanical vibrations are converted into electrical signals

Semicircular canals:

Bony, tubular structure in the inner ear that houses receptors providing the sense of dynamic equilibrium.

What is static equilibrium?

• Maintenance of balance when the head and body are motionless; aids to maintain position of head, posture, and balance when head + body are still.

What is dynamic equilibrium? What structures are responsible for this?

• Maintenance of balance when the head and body are suddenly rotated or otherwise moved.

• Aids to maintain balance when head + body suddenly moves or rotates.

Ampulla

Expansion at the end of each semicircular duct that houses a crista ampullaris, the sensory organ of dynamic equilibrium.

Crista Ampullaris

Sensory organ in a semicircular canal that functions in the sense of dynamic equilibrium.

How do we hear?

when our ears convert invisible sound waves into physical vibrations, which the brain then translates into meaningful sound.

1. Outer Ear (Sound Collection)

Pinna (Auricle) and External Auditory Canal (Ear Canal)

Pinna (Auricle):

The visible outer cartilage that funnels sound waves.

External Auditory Canal (Ear Canal):

A tube that directs sound waves inward.

2. Middle Ear (Vibration & Amplification)

Tympanic Membrane (Eardrum):

Ossicles: Three tiny bones that amplify the vibrations:

Malleus (Hammer)

Incus (Anvil)

Stapes (Stirrup)

Oval Window

Oval Window

The membrane that receives vibrations from the stapes and passes them to the inner ear.

3. Inner Ear (Transduction)

Cochlea, basilar membrane, organ of corti.

Basilar Membrane:

• Moves with the fluid waves, causing the hair cells to bend.

4. Neural Pathway (To the Brain)

Auditory Nerve (Cranial Nerve VIII):

Auditory Nerve (Cranial Nerve VIII):

Carries electrical signals from the cochlea to the brain.

Which cranial nerve(s) are involved in the sense of hearing

vestibulocochlear nerve, also known as Cranial Nerve VIII (CN VIII)

What are the 2 types of equilibrium:

static and dynamic equilibrium.

Static equilibrium

• Maintenance of balance when the head and body are motionless; aids to maintain position of head, posture, and balance when head + body are still.

Utricle (part of static equilibrium)

• Enlarged part of the membranous labyrinth of the inner ear. It contains some of the receptors involved in static equilibrium.

Saccule (part of static equilibrium)

• Enlarged part of the membranous labyrinth of the inner ear.

Macula (part of static equilibrium)

• Sensory structure in the utricle and saccule, consisting of hair cells and a gelatinous mass embedded with otoliths.

Dynamic equilibrium:

• Maintenance of balance when the head and body are suddenly rotated or otherwise moved.

• Aids to maintain balance when head + body suddenly moves or rotates.

Ampulla (part of dynamic equilibrium)

• Expansion at the end of each semicircular duct that houses a crista ampullaris, the sensory organ of dynamic equilibrium.

Crista Ampullaris (part of dynamic equilibrium):

• Sensory organ in a semicircular canal that functions in the sense of dynamic equilibrium.

How does static and dynamic equilibrium differ?

static equilibrium keeps you balanced while you are completely still, like standing perfectly still on one leg. Dynamic equilibrium keeps you balanced while you are in motion, like riding a bike or spinning.

Which cranial nerve(s) are involved in the sense of balance

The vestibulocochlear nerve (Cranial Nerve VIII)

What are chemoreceptors? -

Smell olfactory receptors; detect chemical changes in the body.

What cranial nerves are involved in the sense of smell

The olfactory nerves.

What are taste buds? Where are they located?

Taste buds: Organ containing receptors associated with the sense of taste.

Location- located along the papillae of the tongue.

What are the different taste sensations? Where is each located on the tongue?

•  sweet, sour, salty, bitter, and umami (savory or delicious)

What cranial nerves are involved in the sense of taste

The facial, glossopharyngeal and vagus.