Topic 6 Exam 2

Question 1

What are the parts of the Equilibrium Triad?

Answer 1

Vestibular System

+ Visual System
+ Proprioceptors

Question 2

Static -

Answer 2

position of the
head with respect to
gravity

Question 3

Dynamic -

Answer 3

motion of the
head

Question 4

What motion is detected by the following portions of the vestibular system?

a. Saccule, Utricle, Semicircular canals

Answer 4

STATIC PORTION

Saccule:

oriented in a vertical plane = __Vertical__ Motions detected

• Utricle:

oriented in a horizontal plane = ____ horizontal Motions detected
*linear accelerometers

Semicircular Canals =

rotation, dynamic equilibrium

Running

Question 5

How are neural signals generated to detect motion in the vestibular apparatus (hair cell)? [Movement + 6 steps]

Answer 5

1. Mechanical deformation opens ions channels (K+)
2. K+ enters (concentration gradient – high outside)
3. Membrane potential generated in hair cell
4. Opens voltage-gated Ca2+ channels
5. Vesicles fuse to membrane and release NT
6. EPSP generated in post-synaptic sensory neuron
   (vestibular nerve)

Question 6

Be able to determine whether hyperpolarization or depolarization response in a hair cell would
occur in the horizontal canal of the right [or left] ear in response to a right or leftward head
rotation.

Answer 6

Turn head to left - fluid goes to the right - depolarized to the left hair cell and action potentials are sent to the CNS - right hyperpolarizes and fewer action potentials are generated

and vise versa

Question 7

Kinoocilium is the

Answer 7

longest hair cell

Question 8

Be able to label parts of the eye: pupil, iris, sclera, lens, cornea, choroid, retina

Answer 8

Pupil (B) - hole in the central iris
Iris (D) - muscles that regulate the amount
of light entering the eye
Sclera (E) - (white) shapes and protects
eye
Lens (C) - focuses light rays onto the retina
Cornea (A) - transparent iris covering;
helps focus light!
Choriod (G) - lies within the sclera;
provides nutrients to the retina
Retina (F) - lines ¾ of the eyeball; start of
visual pathway; contains receptors
(rods/cones)

Question 9

What structure regulates the amount of light entering the eye? How?

Answer 9

Iris (D)

By contracting

Constrict muscle to bright light

Dilate muscle for dim light

Question 10

What structure focuses light rays onto the retina? How?

LABELing parts of eye and deforamtion of lens and contriction of the pupil will be on the test

Answer 10

Lens (C)

How?
Deformed the lens and stretch it

Question 11

What portion of the retina does not contain photoreceptors and results in a “blind spot”?

Answer 11

Optic Disc

The fovea is the largest # of cones that “sees” most clearly and is connected to the optic disc

Question 12

Name and describe the two types of eye movements associated with head-eye coordination for
a stationary head (saccades and smooth pursuit) and their function both separately and
together. Explain an example of how they are used.

Answer 12

Saccades—

moves the eyes (fovea)
closer to the position of interest

• Fastest muscular movements in
  humans
• Position dependent
• Tracking

Examples:

Question 13

Name and describe one of the types of eye movements associated with head-eye coordination for
a stationary head (saccades and smooth pursuit) and their function both separately and
together. Explain an example of how they are used.

Answer 13

Smooth-Pursuit—

keeps the eyes
(fovea) on a moving object

• Velocity dependent
• Tracking

Saccade brings that back to it

Examples: Tracking a movement

Question 14

Name and describe one of the reflexive eye movements associated with head-eye coordination for
a moving head (VOR & OKR) and their functions. Explain examples of how they are used.

Answer 14

Vestibulo-Ocular Reflex (VOR) —

holds eye fixation during head
movement (fast head movements)
- fast—for quick movements, provides a quick response (20 ms)

Example: Looking in the mirror and moving your head around to see different sides of your face.

Question 15

Name and describe one of the reflexive eye movements associated with head-eye coordination for
a moving head and their functions. Explain examples of how they are used.

Answer 15

Optokinetic reflex (OKR) —

stabilizes the eyes with respect to the
environment (normal movement in stationary environment)

• slow—for relatively slower movements (than VOR) with a slower response (100 ms)
• track an object out of field of view then return to original eye position it was viewed from (head moves) [combination of smooth pursuit & saccade]
  (Disorder = Nystagmus – repetitive uncontrolled movements)

Example: Sitting in the car and watching the enviorment outside

Question 16

Optokinetic reflex (OKR) — Disorder

Answer 16

(Disorder = Nystagmus – repetitive uncontrolled movements)