Unit 4 Chapter 16 (Special Senses)

Question 1

Describe olfactory receptor cells and the physiology of olfaction

Answer 1

-Located in the olfactory epithelium, axons pass through Cribriform plates and synapse in the olfactory bulb, one of the few neurons that can regenerate
-Odorant binding proteins of olfactory cell: Bind with dissolved odorant, Produces depolarization event, Leads to action potential if threshold reached
-Low threshold (very sensitive!!)
-Rapid adaptation: Decrease sensitivity within seconds after stimulation. Explains why you stop smelling something after being exposed to it for a while

Question 2

Describe gustatory receptor cells and the physiology of gustation

Answer 2

-Single receptor “hair”, regeneration diminishes with age
-Receptor on gustatory hair: Bind with tastant (the molecule you are tasting) dissolved in saliva (again, has to be dissolved in liquid or you to taste it!), Neurotransmitter released, Leads to action potential if threshold
-Variable threshold (sensitivity): Lowest threshold for bitter, then sour (very sensitive), Higher threshold for salty and sweet (less sensitive)
-Quick adaptation: Decrease sensitivity within minutes after continuous stimulation

Question 3

State the functions of eyelids, eyelashes, and eyebrows

Answer 3

-Eyelids: Shade and protect the eye, Spread lubricant over the eyeballs, Orbicularis oculi (closes eyelid), Other glands (secrete fluid that keeps eyelids from adhering to each other), Conjunctiva (protective mucous membrane)
-Eyelashes: Help protect the eyeballs from foreign objects,
perspiration, and direct rays of the sun
-Eyebrows: Help protect the eyeballs from foreign objects,
perspiration, and direct rays of the sun

Question 4

Define conjunctivitis

Answer 4

-Inflammation of the conjunctiva membrane of the eye.

Question 5

Describe the movement of lacrimal fluid (tears) through the lacrimal apparatus and state its function

Answer 5

-Lacrimal glands over the eyes
❑Into Lacrimal Canals at the corner of the eye
❑ Into Lacrimal Sac
❑ Into Nasolacrimal Duct
❑ Into the Nasal Cavity (that’s why your nose runs when you
cry!)
-Functions include protecting, cleaning, and lubricating the eyeball

Question 6

Explain why corneal transplants are highly successful

Answer 6

-The cornea is avascular, minimizing the risk of graft rejection due to the lack of antibodies

Question 7

Explain the mechanism by which the iris regulates pupil size

Answer 7

The iris regulates the amount of light entering the eyeball through the pupil, the hole in the center of the iris. Autonomic reflexes regulate pupil diameter in response to light levels

Question 8

Describe the retina by:
▪ Distinguishing between the functions of rods and cones
▪ Stating the types of cones and how color vision results from their stimulation
▪ Describing the flow of visual impulses from photoreceptors to the optic nerve
▪ Explaining why the optic disc is also called the blind spot

Answer 8

-Rods allow us to see dim light, such as moonlight while Cones are stimulated by bright light, producing color vision.
-There three types of cones, which allow us to produce color vision:
* Blue cones (sensitive to blue light)
* Green cones (sensitive to green light)
* Red cones (sensitive to red light)
-From photoreceptors, visual information flows to bipolar cells through the outer synaptic layer, to bipolar cells, and then through the inner synaptic layer to ganglion cells. The axons of ganglion cells extend posteriorly to the optic disc and exit the eyeball as the optic nerve.
- There are no light sensitive rods or cones to respond to a light stimulus at this point which causes a break in the visual field, giving the nickname “the blind spot”

Question 9

Describe the sequence of eye components a light ray encounters from the time it enters the eye until it reaches the retina.

Answer 9

-cornea -> anterior chamber with aqueous humor -> pupil -> lens -> vitreous body in the vitreous chamber -> retina

Question 10

Describe glaucoma

Answer 10

-Build-up of aqueous humor in anterior cavity, abnormally high intraocular pressure
-Result if untreated: irreversible damage to neurons of retina, optic nerve & blindness

Question 11

Describe cataracts

Answer 11

-Loss of transparency of lens
-Caused by: injury, excessive UV light, increased risk with smoking or age

Question 12

Describe image formation by describing:
▪ Refraction of light rays by the eye
▪ The role of accommodation
▪ The mechanism that allows focusing of distant and close objects

Answer 12

-the cornea provides most of the eye’s optical power or light- bending ability. After the light passes through the cornea, it is bent again – to a more finely adjusted focus – by the crystalline lens inside the eye. The lens focuses the light on the retina
-accommodation is the the change in focal power and allows for focusing on close or far objects
-the mechanism that allows for this to occur is the accommodation–convergence reflex

Question 13

Explain photoreceptor operation by describing:
▪ The process by which photoreceptors respond to light
▪ Stimulation of bipolar cells and ganglion cells by photoreceptors (the exam will not ask about specific retinal neurotransmitters)

Answer 13

-cell gets hyperpolarized; Light enters the eye, reaches the photoreceptors, and causes a conformational change in a special protein called an opsin.
-photoreceptors will release onto bipolar cells. Then a bipolar cell in the retina is connected to a ganglion cell to contribute to retinal processing

Question 14

Define color blindness and night blindness and state the most common cause of each

Answer 14

-color blindness is the inability to distinguish certain colors; most common cause is genetic inheritance from parents
-night blindness is poor vision at night or in dim light; most common cause is vitamin A deficiency

Question 15

Explain the physiology of hearing by:
▪ Distinguish between the frequency and intensity of sound
▪ Describing events involved in hearing
▪ Explaining how the spiral organ distinguishes the frequency and intensity of sound

Answer 15

-frequency is the number of sound waves in a given time; pitch. intensity of sound is the size of the wave; loudness
-The eardrum vibrates. The vibrations are then passed to 3 tiny bones in the middle ear called the ossicles. The ossicles amplify the sound. They send the sound waves to the inner ear and into the cochlea
-the basilar membrane, which exhibits different degrees of stiffness, or resonance, along its length

Question 16

Define otitis media and explain the involvement of the auditory tube

Answer 16

-otitis media is a middle ear infection
-the involvement of the auditory tube is that it is like the highway for the infection to travel from the nasopharynx to the throat and then to the middle ear

Question 17

Explain how loud sounds can result in hair cell damage

Answer 17

-hair cells are sensitive to big movements. if sounds are loud, they move the fluid in the inner ear more, and that can damage the hair cells and result in poorer sound transmission.

Question 18

Distinguish between static and dynamic equilibrium and explain the physiology of equilibrium.

Answer 18

-static equilibrium is detecting head tilt and moving in a straight line. dynamic equilibrium is detecting rotational acceleration or deceleration
-Equilibrium involves the stimulation of Hair Cells,
The Hair Cells have their hairs embedded in some kind of membrane (the names of the membranes vary) that pull on the Hairs (Stereocilia),
The Hair Cells have ion channels that are mechanically pulled open,
K+ from the Endolymph depolarizes the Hair Cells,
Action potentials will then be generated and sent via the Vestibular branch of the Vestibulocochlear Nerve to the Cerebellum,
Head/body MOVMENTS (not sound waves) cause movements in the fluid and activate Hair Cells for Equilibrium