Block 3

Question 1

What is epiphora?

Answer 1

Overflow of tears onto the face - clinical sign that indicates insufficient tear drainage - Under control of the ANS (parasympathetic)

Question 2

Where is the refractive power greater, cornea or lens?

Answer 2

Cornea

Question 3

How does distance vision work?

Answer 3

• Rays are coming in parallel to eye/flat
• Muscle is relaxed and zonules are constricted
• Lens is flat and has less refracting power

Question 4

How does near vision work?

Answer 4

• First, the object is focused behind the retina
• Then eyeball is stimulated to accommodate
• Then the ciliary muscle contracts
• This makes lens fatter and corrects near vision
• Zonules are relaxed at this time

Question 5

What is myopia?

Answer 5

• Near-sightedness
• AL > FL
• Eyeball is too long and/or too strong of lens
• Corrected with concave lens

Question 6

What is hyperopia?

Answer 6

• Far-sightedness
• AL (axial length) < FL (focal length)
• Eyeball is too short and/or too weak lens
• Corrected with convex lens

Question 7

What is presbyopia?

Answer 7

Decrease in accommodative power of lens with age

Question 8

What does the ciliary muscle do?

Answer 8

Changes shape of lens, not diameter of the pupil when it contracts. The diameter of the muscle becomes less.

Question 9

What happens if the ciliary muscle is relaxed?

Answer 9

Zonules are tight –> pulls lens flatter (looking at long distance objects)

Question 10

What happens if the ciliary muscle is contracted?

Answer 10

Zonules are loose –> lens gets fatter/wider (looking at short distance objects)

Question 11

What is the innervation to the ciliary muscle?

Answer 11

• Mostly parasympathetic
• Preganglionic from Edinger-Westphal nucleus
• Post-ganglionic from ciliary ganglion via oculomotor nerve
• Activation of M3 receptors causes contraction -> dec. diameter of ring -> releases tension in zonular fibers -> rounding of lens

Question 12

What causes Mydiasis?

Answer 12

Sympathetic - Innervation from superior cervical ganglion -> releases NE & alpha1 -> contracts dilator muscle

Question 13

What causes miosis?

Answer 13

Parasympathetic - Innervation from Ciliary ganglion -> Releases ACh -> Contracts sphincter muscles

Question 14

Describe the pathway of the pupillary light reflex:

Answer 14

1. Light enters through the pupil and hits the retina
2. Transferred through optic tract to the 2nd order neuron
3. Message is sent to preganglionic parasympathetic neurons of the Edinger-Westphal Nucleus in Aqueduct
4. Information is transferred via the preganglionic parasympathetic part of the oculomotor nerve to the ciliary ganglion.
5. Ciliary ganglion causes pupil constriction (innervates constrictor muscle of the iris)

Question 15

What is the blind spot?

Answer 15

Where all the ganglion cell axons leave the retina to go to the brain. There are no photoreceptors here.

Question 16

What is the macula-lutea?

Answer 16

The yellow spot where blood vessels have been pushed away.

Question 17

What do photoreceptors encode?

Answer 17

Frequency which equates to color

Intensity which equates to brightness

Question 18

What kind of light is your eye detecting?

Answer 18

Reflected light!

Question 19

What are the three types of cones?

Answer 19

1. Blue (short wavelength)
2. Green (medium wavelength)
3. Red (long wavelength)

Question 20

What cells does energy pass through in the eye to get to the optic nerve?

Answer 20

Photoreceptors –> Bipolar cells –> Ganglion cells

Question 21

What are the steps in phototransduction?

Answer 21

1. Light activates rhodopsin (visual pigment)
2. Activation of G protein (conversion of GTP -> GDP)
3. Activation of PDE (phosphodiesterase)
4. PDE converts cGMP to GMP
5. Closing of cGMP dependent Na+ channels - Na+ no longer flows into the cell
6. Channel closing causes the cell to hyperpolarize (become more negative in Eqpot and generate a signal that is sent on to the optic nerve)

Question 22

Describe the visual cycle:

Answer 22

1. Rhodopsin is hit by light in the rod
2. Rhodopsin splits into opsin & all-trans-retinal
3. All trans-retinal becomes all-trans-retinol
4. All-trans-retinol is transported to the RPE (retinal pigment epithelium)
5. In RPE, all-trans-retinol is converted to 11-cis retinal
6. Then 11-cis-retinal is brought back into the rod converted to rhodopsin
   (all-trans-retinal originally comes from capillary to the RPE)

Question 23

What happens in conductive hearing loss?

Answer 23

Increase in hearing threshold due to decrease in sound transmission through the external and/or middle ear. Air conduction is reduced in these cases but bone conduction remains the same.

Question 24

What are common causes of conductive hearing loss?

Answer 24

• Ruptured eardrum
• Intra-tympanic fluid (caused by otitis media)
• Otosclerosis

Question 25

What are the two main structural components of the inner ear and what do they contain?

Answer 25

1. Bony (osseous) labyrinth - contains Na+ - rich perilymph | 2. Membranous labyrinth - contains K+ - rich endolymph

Question 26

What are the two types of inner ear receptors?

Answer 26

1. Type I (inner hair cells) - true sensory receptors | 2. Type II (outer hair cells) - biological amplifiers (act as motor units)

Question 27

What is the mechanical transduction that happens in the cochlea?

Answer 27

-Displacement toward the tallest stereo ciliacauses depolarization -In cochlea, this occurs when the basilar membrane moves toward the scala vestibuli [Negative deflection - toward scala tympani - results in hyperpolarization]

Question 28

What detects head rotation (angular acceleration)?

Answer 28

Semicircular canals

Question 29

What detects gravity (linear acceleration)?

Answer 29

Otolith organs (utricle & saccule)

Question 30

How do the saccule and utricle detect head position?

Answer 30

Otoconia (rocks) embedded in the otolith membrane produce drag on the stereo cilia when the head position changes relative to the ground.

Question 31

How are the semicircular canals paired?

Answer 31

Depolarization occurs on the same side as head rotation. Ex: head goes left and depolarization happens in left canals, hyperpolarization in the right canals

Question 32

If you tilt your head forward, what canals depolarize and what hyper polarize?

Answer 32

The canals tilting forward depolarize and the canals in the opposite plane that end up tilting up hyperpolarize.

Question 33

What does scala media contain?

Answer 33

Endolymph

Question 34

What does scale vestibule and scala tympani contain?

Answer 34

Perilymph

Question 35

What does the stria vascular produce?

Answer 35

Endolymph and it generates the endocochlear potential (+80 mV).

Question 36

On the cochlea, where are high and low frequencies transduced?

Answer 36

High frequencies - base | Low frequencies - apex

Question 37

Diuretics that affect the ion transporters in the kidney. . .

Answer 37

. . .are often ototoxic because the same ion transporters are in the ear - esp. loop diuretics - affect Na+/K+/Cl- transporter