Complexity of reflex action

Question 1

Name the eliciting stimulus in wiping reflex in frogs

Answer 1

Irritation at location of skin

Question 2

In the wiping reflex, what does the foot position depend upon?

Answer 2

Depends upon stimulus location

Question 3

List the 3 things the frogs spinal cord dealt with

Answer 3

Knee or ankle immobilised with cast, ankle weighed with heavy bracelet, stimulus on head & body bent over

Question 4

Explain goal-directedness

Answer 4

Response able to achieve same outcome under different circumstances

Question 5

Name the 2 reasons for making eye movements

Answer 5

Keep images on retina still, position images of interest onto fovea

Question 6

Define the vestibular organs

Answer 6

Inner ear complex that mediate reflex

Question 7

The semi-circular canals are responsible for which reflex?

Answer 7

Vestibular-ocular reflex

Question 8

What are the consequences of loss of VOR?

Answer 8

Unable to keep eyes still inside head

Question 9

Saccades allow what?

Answer 9

Allow direction change of eye (rapid jump)

Question 10

Define fixation

Answer 10

Period of staring at something

Question 11

In which two ways do the eyes move?

Answer 11

Rapid shifts from 1 position in orbit to another (saccades), much slower and smoother movements that gradually shift eye’s position in orbit (generated by VOR)

Question 12

What do reflex saccades involve?

Answer 12

Involve pathways from sensory organs and superior colliculi and then to the PPRF

Question 13

Define superior colliculi

Answer 13

Midbrain nuclei that are visible as 2 bumps on dorsal surface of midbrain

Question 14

What are horizontal eye movements

Answer 14

Contraction of medial and lateral recti

Question 15

Where are medial recti motorneurons located?

Answer 15

In oculomotor nuclei at midbrain level

Question 16

Where are lateral recti motorneurons located?

Answer 16

In abducens nuclei at pontine level

Question 17

How do eyes move left?

Answer 17

Signals from left abducens and right oculomotor nucleus

Question 18

Describe how the eyes move right

Answer 18

Signals from right abducens and left oculomotor nucleus

Question 19

What is a left saccade?

Answer 19

Simultaneous contraction of left eye lateral rectus and right eye medial rectus

Question 20

What would be the consequences of a loss of VOR?

Answer 20

Eyes would jiggle around, making clear vision impossible.

Question 21

Name the 3 dimensions VOR moves in

Answer 21

Horizontal, vertical and torsional

Question 22

Define conjugate eye movements

Answer 22

Eyes move together in the same direction

Question 23

What are disconjugate eye movements?

Answer 23

Eyes move together in opposite directions

Question 24

Name the 3 things visual elicited reflexes involve

Answer 24

Retina, superior colliculi, PPRF

Question 25

The role of the PPRF is to what?

Answer 25

Generate bursts of excitation so eyes move rapidly from one position to another

Question 26

What is the production of a VOR response dependent on?

Answer 26

Depends on your intent to keep looking in the same direction (VOR) and intent to look in new direction (no VOR)