BN Ch.21 The Sensory System Flashcards
1
Q
Identify the location of receptors for each of the five senses; explain how these stimuli are interpreted in the brain.
A
- Taste (Tongue)
- Chemoreceptors in the mouth obtain information about tastes (gustatory sense).
- Smell (Nose)
- Chemoreceptors in the nose receive sensations of odors (olfactory sense).
- Touch (Skin)
- Touch receptors receive information about the surrounding world (e.g., touch, pressure, hot, cold, pain).
- Internal organs receive sensations of pain, pressure, fullness, and vibration.
- Hearing (Ears)
- Hearing receptors process sound waves (auditory sense).
- Through proprioceptors and the inner ear, the system helps to maintain a sense of balance, equilibrium, and position in space.
- Sight (Eyes)
- Visual sense receives images (light).
2
Q
Describe major structures of the eye and functions of each; differentiate between aqueous and vitreous humor.
A
- Superior Rectus Muscle
- Controls upward movement
- Lacrimal Gland
- The lacrimal glands produce tears (lacrimal fluid), about 1 mL/day, to moisten and lubricate the eye’s surface.
- Lacrimal glands are located at the outer corner (lateral canthus ) of each eye.
- Tears drain from the eye through a small opening, the punctum, into the nasolacrimal duct, located in the inner corner of the eye ( medial canthus ).
- Iris
- Over the front of the eyeball, the choroid develops into a pigmented section, the iris , which gives the eye its specific color.
- The amount of pigment in the iris determines eye color.
- Smooth and radial muscles in the iris control the size of the pupillary opening
- Pupil
- The pupil is the black center opening within the eye that allows light to enter.
- In strong light, iris muscles constrict the pupil, to allow less light to enter.
- The reverse occurs under low-light situations (the Purkinje effect).
- When a bright light is suddenly shined into the eye, the pupil should contract quickly, as a protective mechanism.
- This pupillary reflex is tested in a routine eye examination and to determine cerebral function
- Lateral palpebral ligament
- The lateral palpebral raphe is a ligamentous band near the eye.
- Its existence is contentious, and many sources describe it as the continuation of nearby muscles.
- It is formed from the lateral ends of the orbicularis oculi muscle.
- Inferior Rectus Muscles
- Controls downward movement
- Inferior Oblique Muscle
- Controls downward and inward movement
- Tendon of Superior Oblique Muscle
- Controls upward and outward movement
- Superior Lacrimal Duct
- The lacrimal duct system transmits tears from the surface of the eye to the nasal cavity.
- Tears enter the duct system at the lacrimal punctae and conduct through canaliculi within the eyelids. The canaliculi drain into the lacrimal sac.
- Lacrimal Sac
- The lacrimal sac is anterior to the orbital septum, nestled in its own fascia in the lacrimal fossa. The lacrimal crest of the maxillary bone forms the anterior border of the lacrimal fossa. The lacrimal crest of the small lacrimal bone forms the posterior border of the lacrimal fossa.
- Medial Palpebral Ligament
- The medial palpebral ligament (medial canthal tendon) is a ligament of the face. It attaches to the frontal process of the maxilla, the lacrimal groove, and the tarsus of each eyelid. It has a superficial (anterior) and a deep (posterior) layer, with many surrounding attachments.
- Inferior Lacrimal Duct
- The lacrimal duct system transmits tears from the surface of the eye to the nasal cavity.
- Tears enter the duct system at the lacrimal punctae and conduct through canaliculi within the eyelids. The canaliculi drain into the lacrimal sac.
- Nasolacrimal Duct
- The nasolacrimal ducts drain tears into the nose.
- Tears contain an enzyme that helps protect the eyes from bacterial infections.
- Chemical and mechanical irritants (e.g., onions or dust) or foreign objects cause over secretion by the lacrimal glands to wash irritants away.
- Humans are the only species that form tears in response to emotions.
- Opening of duct into Inferior Nasal Meatus
- The inferior meatus is below and lateral to the inferior nasal concha;
- The nasolacrimal duct opens into this meatus under cover of the anterior part of the inferior concha.
- The anterior chamber of the eye contains aqueous humor.
- Aqueous humor is thin and is produced by the ciliary body and supplies oxygen, glucose, and proteins to the eye.
- The posterior chamber contains vitreous humor.
- A thicker, clear gel.
3
Q
Identify which cranial nerves are responsible for the blink reflex, pupillary changes, visualization, and pain sensation in the eye.
A
- VII Facial
- Controls blinking reflex
- V Trigeminal (ophthalmic branch)
- Carries sensations of eye pain and temperature
- II Optic
- Carries visual images to the brain
- III Oculomotor
- Constricts and dilates pupil;
- Elevates eyelid;
- Innervates superior, inferior, and medial rectus and inferior oblique muscles
4
Q
Differentiate between myopia, hyperopia, and astigmatism.
A
- In nearsightedness (myopia), light rays are focused in front of the retina because the lens muscles contract too tightly, not allowing enough light to enter the eye, or because the eyeball is too long.
- The nearsighted person sees close objects clearly, but distant objects are blurry.
- If the eyeball is too short, the light rays land behind the retina, causing farsightedness (hyperopia or hypermetropia).
- In this instance, the refracted light rays do not come together directly on the retina but are absorbed by it.
- Therefore, the farsighted person cannot see close objects clearly.
- Astigmatism is caused by irregularities in the curvature of the cornea and lens.
- The eye cannot bring horizontal and vertical lines into focus at the same time, causing blurry vision.
5
Q
Identify structures and dividing lines between the outer, middle, and inner ear.
A
- The division between the middle ear and inner ear is the oval window (fenestra ovalis).
- The inner ear is embedded in the temporal bone, the densest bone in the body.
- Here, the bony labyrinth contains the membranous labyrinth (or just labyrinth).
- Both labyrinths are filled with fluid similar to cerebrospinal fluid.
- The tympanic membrane contains fibrous tissue and mucous membrane
- It separates the external from the middle ear. (When reacting to sound, the eardrum moves less than the diameter of a hydrogen molecule.)
- The external ear, the pinna or auricle, is the only readily visible part of the ear.
- It is composed mostly of cartilage and is funnel shaped, to gather and guide sound waves into its small opening, which extends into the auditory canal.
- This opening is the external auditory meatus.
- This canal is covered with tiny hairs and contains ceruminous glands, which secrete a waxy substance, cerumen, or ear wax.
- The hairs and wax aid in protecting the ear from foreign objects
6
Q
Trace the path of light rays as they enter the eye and focus on the retina; describe transmission to the brain.
A
- Cornea (refraction)
- Anterior chamber and aqueous humor (refraction)
- Pupil (constriction and dilation)
- Lens (accommodation)
- Vitreous chamber and vitreous humor (refraction)
- Retina—rods and cones (receiving images of black/white and color)
- Central fovea (light rays focus for sharpest vision)
- Optic disk (nerve fibers converge, called the blind spot)
- Optic nerve (cranial nerve II)
- Optic chiasm (cranial nerves cross)
- Thalamus Cerebral cortex (interprets impulses)
7
Q
Trace the path of sound waves through the external, middle, and inner ear. Describe amplification and interpretation of sound waves.
A
- Path taken by sound waves reaching the inner ear.
- Sound travels from the external environment → external auditory canal → tympanic membrane, where vibrations begin.
- The vibrations travel through the middle ear → oval window into the inner ear, where they travel through the cochlear fluid (perilymph and endolymph) → receptors (hair cells) of organ of Corti.
- From here, the vibrations are transmitted to auditory nerve fibers → vestibulocochlear nerve → cerebral cortex, where they are interpreted.
8
Q
Explain how cerumen, ossicles, and eustachian tubes protect the ear.
A
- This canal is covered with tiny hairs and contains ceruminous glands, which secrete a waxy substance, cerumen, or ear wax.
- The hairs and wax aid in protecting the ear from foreign objects.
- The auditory canal is very short, approximately 1 in. (2.54 cm) in an adult, and extends to a thin membrane, the eardrum
- The middle ear consists of the tympanic membrane and the bony ossicles called the malleus, incus, and stapes.
- These three ossicles connect the tympanic membrane to the inner ear allowing for the transmission of sound waves.
- Two small muscles attach to the stapes and malleus.
- These muscles reflexively contract at sudden, loud noises.
- This reflex stops the ossicles’ vibration, thereby protecting the vital internal organs of the middle and inner ear from injury.
- The Eustachian tubes
- This structure allows the equalization of pressure in the middle ear in order to maintain proper pressure.
- Without proper pressure, hearing would be very painful and potentially cause the eardrum, to rupture.
- The eustachian tube also helps drain the middle ear.
- The middle ear, eustachian tube, nasopharynx, and the passage to the mastoid cells are lined with a continuous coating of mucous membrane.
- Clenching the jaw inhibits eardrum movement and impairs hearing.
9
Q
Discuss how the organs of the inner ear provide a sense of balance.
A
- Another section of the inner ear includes the semicircular canals.
- Shaped like horseshoes, they lie behind the cochlea and are primarily concerned with balance when the body is moving (acceleration/deceleration or head movements).
- Sensory receptors for equilibrium (balance) in the moving body are on nerve endings in the semicircular canals (active balance).
10
Q
Describe locations and functions of taste buds; identify the associated flavors of each.
A
- The sense of taste (gustation) is based on perceptions of sweet, salty, sour, bitter, metallic, and fatty or meaty (umami) flavors and their combinations.
- Over 10,000 taste receptors, the taste buds , are located in the mouth.
- Chemoreceptors (gustatory cells) in taste buds detect chemicals in solution in the mouth.
- Basic tastes are perceived by taste buds on the tongue, as well as in the lining of the cheek and roof of the mouth.
- Most foods have a combination of taste sensations.
- In addition, many characteristic tastes are greatly influenced by the sense of smell, such as the taste of an onion.
- Two cranial nerves carry the sensation of taste to the brain:
- the facial nerve (CN VII) and
- the glossopharyngeal nerve (CN IX).
- The sense of taste is interpreted in the parietal and temporal lobes of the cerebral cortex (the anterior cingulate).
11
Q
Identify the structures related to the sense of smell; describe how they function.
A
. Identify the structures related to the sense of smell; describe how they function.
- Even though olfactory Smell Receptors cells are in your nose, they are part of your brain!
- These nerve cells are in direct contact with the outside world.
- Unlike any other nervous tissue in your body, they can regrow.
- Each one lasts about a month before it is replaced by a fresh cell.
- Tiny particles in the air you. Breathe dissolve in the mucus lining in your nose
- The particles attach to hairs on the smell receptors cells lying in the mucus
- The Smell receptor cells send signals up their fibers.
- The Signals pass through tiny holes in the bony Cribriform Plate
- The Signal reaches the Olfactory Bulb
- Travels through your brain along the Olfactory Tract
Smell centers in your brain process the signal
12
Q
Describe the effects of aging on the sensory system.
A
- Vision/Eye Changes
- Lens accommodation decreases: lens loses elasticity
- Presbyopia (farsighted); difficulty seeing close objects or reading
- Depth perception decreases
- Difficulty judging height of curbs and steps Falls common
- Peripheral vision decreases
- Driving may be dangerous
- Pupil size decreases: ability to react to darkness and bright light decreases; night vision decreases
- Takes longer for eyes to adjust when entering a dark room or bright sunlight May require additional light for reading
- Color perception decreases Depth perception decreases
- Clouding of lens
- Difficulty discerning hues of blue, green, and violet and distances Cataract (may occur at any age)
- Grayish white ring (arcus senilis ) forms around iris due to deposits of calcium and cholesterol salts
- May lower self-esteem and body image (does not affect vision)
- Vitreous gel liquefies
- Posterior visual detachment (PVD), causing “floaters” in eyeball
- Tear formation decreases
- Dry, itchy eyes More susceptible to infections
- Fluid circulation in eye decreases
- Increased risk for glaucoma
13
Q
The __________ of the eye is the transparent, tough section over the front of the eyeball.
A
cornea
14
Q
__________ receptors are located in areas such as the fingertips and around the lips, constantly receiving nerve impulses with regard to pain and pleasure.
A
Tactile
15
Q
__________ is the high-pitched, buzzing
sound or ringing in the ear that often
accompanies vertigo.
A
Tinnitus
