Eye and head movements Flashcards Preview

Neuroscience > Eye and head movements > Flashcards

Flashcards in Eye and head movements Deck (28):

What are the components that control gaze and stabilise an image on the retina?

Oculomotor system: moves eyes in orbit whilst head is still

Head-movement system: moves eye sockets as a whole whilst head moves


Describe the different types of eye movements?

Saccadic: shift fovea rapidly to new visual target

Smooth pusruits: keep image of a moving target on fovea

Vergence: moves eyes in opposite directions

Vesticular ocular: holds image still on retina during brief head movements

Optokinetic: holds image stationery during sustained head rotation or translation


Describe the extraocular muscles?

4 rectus muscles: superior, inferior, lateral, medial

2 obliques: inferior, superior 

A image thumb

Describe the movements that can be performed by the eye?




A image thumb

What determines the actions of the rectus muscles?


Their insertion onto the eyeball


Describe the primary actions of the rectus muscles?


SR: elevation

IR: depression

MR: adduction

LR: abduction


Describe the insertions of the oblique muscles?


Insert a long way down the back of the eyeball

SO: well behind equator at an oblique angle close to LR (tendon runs through trochlea)

IO: behind equator close to LR

A image thumb

Describe the primary actions of the oblique muscles?

SO: torsion (also involved in depression)

IO: torsion (also involved in elevation)


How can each of the six eye muscles be tested in isolation?


A image thumb

Which lower motor neurons are involved in the neural control of eye movements?


Oculomotor nerve (CN III): SR, IR, MR, IO

Abducens nerve (CN VI): LR

Trochlear nerve (CN IV): SO


Describe the neural control of eye movements?


Hierarchical control of eye movement involving:

LMNs (CNs)

Brainstem centres (reticular formation)

Higher cortical areas



How does the neural supply of CN IV to the SO muscle differ to the innervation of the other extraocular muscles?


CN IV innervates contralateral SO

Others all have ipsilateral innervation


Which structures are responsible for coordinating the movements from one eye with the other?

Medial longitudinal fasiculus

Reticular formation: PPRF (pontine paramedian reticular formation) and MPRF (mesencephalic paramedian reticular formation)

A image thumb

What is the MLF?

Medial longitudinal fasiculus

White matter tract that connects the various cranial nerve nuclei


A image thumb

What is the function of the pontine paramedian reticular formation?

Horizontal gaze centre

Coordination of MR and LR of each eye (CN III and CN VI)

A image thumb

What is the function of the mesencephalic paramedian reticular formation?

Vertical gaze centre 

Coordination of SO and SR of each eye (CN IV and CN III)

A image thumb

Where is a patient's lesion if they cannot coordinate horizontal movement of the eyes?


A image thumb

Where is a patient's lesion if they cannot coordinate vertical movement of the eyes?


A image thumb

Describe the neural control of horizontal saccades?

Requires simultaneous excitation of burst neurons and inhibition of omnipause neurons 


Message from cortex > excites burst neurons > stimulates ipsilateral abducens > contraction of ipsilateral LR

At same time, activates neuron in MLF > stimulates part of contralateral oculomotor nucleus > contraction of contralateral MR 


Communication from PPRF inhibits contralateral abducens nucleus > contralateral LR inhbited 

At same time, via MLF, inhibitory signal from contralteral abducens nucleus to ipsilateral oculomotor nucleus > ipsilateral MR inhibited

A image thumb

Describe the function of burst neurons in the PPRF?

Fire at high frequency just before movement

Two types: excitatory and inhibitory

Excitatory: provide excitatory connections with ipsilateral abducens

Inhibitory: suppress activity of contralateral abducens 

A image thumb

Describe the function of omnipause neurons in the MPRF?

Fire continuously during the saccade, excpet when the eyes move (tell eyeballs when to stop moving)

Project to contralteral abducens nucleus 


A image thumb

Which neurotransmitter do omnipause neurons in the MPRF use?



What drives saccadic eye movements?

Higher cortical processing

Frontal eye fields, superior colliculus and basal ganglia play important roles 

A image thumb

How is the abducens nucleus connected to the contralteral oculomotor nucleus?



How are we able to maintain focus on a stationary object while moving our heads, without loss of visual focus or dizziness?

Input from vestibular system 


How does the vestibular system help us to maintain focus on a stationary object when our head is moving?

Three semiciruclar canals provide information about the head in space (fluid movement across hair cells > neural signal)

In addition, otolith organs give information about linear acceleration 


A image thumb

How does neural signalling within semicicrcular canals alter eye movements?

When fluid goes in one direction through the semicircular canal > increase in AP firing

At the same time, fluid going through the oppsoite ear will cause a decrease in AP firing

This signalling goes to the vestibular nucleus in the brainstem > integrates with eye movement system (CN III, CN VI nuclei)

A image thumb

Describe the vestibular-ocular reflex?

A image thumb