SENSING&RESPONDING: reflex eye movements

Question 1

what are the 2 ways that eyes move?

Answer 1

• saccades
• VOR generated

Question 2

what are saccades?

Answer 2

rapid shifts from one position in the orbit to another

Question 3

what is the vestibular ocular reflex?

Answer 3

a reflex involving vestibular organs which keeps eyes steady despite head movement

Question 4

what is the effect of losing vestibular ocular organs?

Answer 4

you lose the vestibular ocular reflex but you don’t lose a sense of balance

Question 5

describe how the vestibular ocular reflex works

Answer 5

it keeps eyes fixated on an object of interest as your head moves
- the eyes counter rotate so they remain pointing in the same direction

Question 6

what is the role of the vestibulocollic reflex?

Answer 6

balances head on shoulders

Question 7

what is the cervicocollic reflex?

Answer 7

response driven by stimulation of muscle spindles in neck muscles and tissue

Question 8

which components are used to generate saccades?

Answer 8

nuclei and motor neurons
- in brainstem

Question 9

what is the purpose of a saccade?

Answer 9

brings images or objects of interest on the foveas

Question 10

what are fixations?

Answer 10

brief stationery periods between saccades where the eyes do not move

Question 11

define conjugate eye movements

Answer 11

when eyes move together in the same direction through the same angle
- ocular motor nuclei in midbrain and abducens nuclei in pons (connected by interneurons) are activated simultaneously

Question 12

define disconjugate eye movements

Answer 12

eyes move together in opposite directions
- simultaneous contraction of left and right eye lateral rectus

Question 13

describe how a leftward saccade occurs

Answer 13

• activating signals are sent to the left abducens
• motor and interneurons are excited and carry the signal to the right oculomotor nucleus
• inhibitory interneurons ensure that the muscles on the right side are relaxed and muscles on the left can contract
• paramedian pontine reticular formation in pons produces excitatory signals
• eyes move rapidly to new position

Question 14

how do eyes avoid drifting from fixation?

Answer 14

nucleus prepositus hypoglossi transforms the burst of action potentials into a sustained action potential

Question 15

describe the process of voluntary saccades

Answer 15

signal enters frontal cortex
superior colliculi
PPRF

Question 16

describe the process of reflex saccades

Answer 16

signal enters retina
superior colliculi
PPRF