Term
| How many axes are used to describe the rotary movements of the eye? |
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Definition
| 3 (they pass through the center & are oriented perpendicular to each other) |
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Term
| 3 planes used to describe the movements of the eye |
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Definition
1. frontal
2. saggital
3. transverse (horizontal) |
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Term
| When do we perform horizontal eye movements? |
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Definition
| when looking to one side; ex) when looking to the left, the left eye rotates laterally & the right eye rotates medially |
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Term
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Definition
| movements that direct the gaze up & down |
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Term
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Definition
| movements around a sagittal axis |
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Term
| What do the six extraocular muscle ensure? |
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Definition
| that the visual axes of the eyes can be directed precisely toward any point in the visual field |
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Term
| To what to the extraocular muscles attach & where do they all originate from? |
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Definition
| attach to the sclera; originate from the wall of the orbit |
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Term
| How many straight extraocular muscles are there? How many oblique? |
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Definition
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Term
| What is the difference in movement between the lateral rectus muscle & the medial rectus muscle? |
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Definition
lateral = pulls the front of the eye laterally
medial = pulls it medially |
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Term
| What is the difference in movement between the superior rectus muscle & the inferior rectus muscle? |
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Definition
superior = pulls the eye upward
inferior = pulls it downward |
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Term
| Do the oblique muscles have a more or less complicated course than the rectus muscles? |
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Definition
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Term
| Where does the inferior oblique muscle originate from & where does it run? |
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Definition
| originates from the bottom of the orbit in its anteromedial part; runs posterolaterally to insert behind the equator (like the superior oblique) |
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Term
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Definition
| when the eye is viewing a distant object straight ahead |
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Term
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Definition
| the two eyes move together to ensure that the image always falls on corresponding points of the two retinas; all natural eye movements are conjugated |
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Term
| When does double vision (diplopia) occur? |
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Definition
| if the eye movements do not occur in conjugation |
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Term
| Are there muscle spindles in the extraocular muscles? |
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Definition
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Term
| What is the difference between saccadic movements & pursuit movements? |
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Definition
saccadic = the gaze moving quickly from one point of fixation to another
pursuit = the gaze being kept stationary on an object when the object or the head moves |
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Term
| Can eye movements be voluntary or reflex? |
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Definition
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Term
| Where do the different premotor networks that control each of the kinds of eye movement all converge? |
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Definition
| on the motoneurons of the extraocular muscles |
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Term
| When are saccades voluntary? |
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Definition
| when we look at a stationary landscape & fix the gaze at one point for a moment & then move on to another point of fixation |
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Term
| When are saccades reflexes? |
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Definition
| as part of vestibular or optokinetic nystagmus |
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Term
| Why do we constantly scan the visual scene? |
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Definition
| to provide maximal information |
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Term
| How are smooth-pursuit movements voluntary? |
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Definition
| they require that our attention be directed to something in the visual field; the gaze is voluntarily fixed |
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Term
| optokinetic reflex movements |
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Definition
| movements intended to stabilize the retinal image when the whole visual field moves relative to the head |
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Term
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Definition
| the stimulus for optokinetic reflex movements; movement of the image on the retina |
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Term
| vestibulo-ocular reflex movements |
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Definition
| eye movements elicited by movements of the head |
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Term
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Definition
| change the visual axes of the eyes in relation to each other when the point of fixation moves away from or toward the eyes |
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Term
| convergence of the visual axes |
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Definition
| takes place when an object is approaching the eyes; depends primarily on the activity of the medial muscles with some contribution also from the superior & inferior recti |
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Term
| 2 phenomena that accompany convergence movements |
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Definition
1. accommodation
2. pupillary constriction |
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Term
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Definition
1. saccades
2. smooth-pursuit movements
3. optokinetic reflex movements
4. vestibulo-ocular reflex movements
5. vergence movements |
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Term
| What structure integrates information about desired eye position, actual position, retinal slip, & position of the head? |
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Definition
| the reticular formation close to the eye muscle nuclei |
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Term
| Where are commands from reticular formation premotor neuron groups sent? |
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Definition
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Term
| What type of eye movements is the paramedian pontine reticular formation (PPRF) a "center" for? |
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Definition
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Term
| Where do internuclear neurons in the abducens nucleus send their axons? |
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Definition
| to the medial rectus motoneurons of the opposite side |
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Term
| What results from a lesion in the region of the PPRF? |
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Definition
| reduced horizontal conjugate movements to the side of the lesion |
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Term
| Where is the center for vertical & rotary eye movements? |
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Definition
| in the reticular formation close to the oculomotor nucleus |
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Term
| 2 cell groups in the region of the reticular formation close to the oculomotor nucleus that controls vertical & rotary eye movements |
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Definition
1. rostral interstitial nucleus of the medial longitudinal fasciculus
2. interstitial nucleus of Cajal |
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Term
| 3 places the reticular formation close to the oculomotor nucleus that controls vertical & rotary eye movements receives afferents from |
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Definition
1. vestibular nuclei
2. pretectum
3. frontal eye field |
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Term
| Do visual signals pass directly from the retina to the eye muscle nuclei? |
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Definition
| no! they are mediated by several brain stem nuclei which receive impulses other than visual information |
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Term
| 2 nuclei that mediate signals from the retina on their way to the eye muscle nuclei |
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Definition
1. superior colliculus
2. pretectal nuclei |
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Term
| By means of what structure do the vestibular nuclei reach all the cranial nerve nuclei of the eye muscles? |
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Definition
| medial longitudinal fasciculus |
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Term
| 2 reflexes mediates by the direct & indirect impulse pathways from the vestibular nuclei to the eye muscle nuclei |
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Definition
1. vestibulo-ocular reflexes
2. optokinetic reflexes |
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Term
| mesencephalic trigeminal nucleus |
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Definition
| brings proprioceptive signals from muscle spindles of the extraocular muscles to the eye muscle nuclei |
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Term
| What is the difference between the vermis' involvement in eye movement and the flocculus/adjoining parts of the posterior lobe of the cerebellum (paraflocculus)'s involvement in eye movement? |
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Definition
vermis = particularly concerned with the performance of saccades
flocculus/paraflocculus = most important for pursuit movements |
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Term
| What eye movements are the lateral parts of the pontine nuclei necessary for? |
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Definition
| voluntary pursuit movements & the slow phase of optokinetic nystagmus |
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Term
| Where do the relevant parts of the pontine nuclei receive afferents from? |
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Definition
| the middle superior temporal area (MST) (related to visual analysis of moving objects) |
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Term
| Does a distributed or concentrated cortical network control eye movements? |
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Definition
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Term
| Do cortical areas for control of eye movements overlap areas related to shift of attention? |
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Definition
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Term
| What type of eye movements is the frontal eye field of the cortex of particular importance for? |
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Definition
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Term
| 3 places where the frontal eye field effects are mediated |
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Definition
1. superior colliculus
2. pretectal nuclei
3. PPRF |
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Term
| Besides the frontal eye field, 3 cortical areas associated with voluntary saccades |
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Definition
1. SMA
2. dorsolateral prefrontal cortex
3. posterior parietal cortex |
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Term
| When is the supplementary eye field (a cortical area close to the frontal eye field) particularly active? |
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Definition
| when saccades are coordinated with hand movements |
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Term
| What are the superior colliculus & vermal oculomotor area of the cerebellum both necessary for? |
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Definition
| proper execution of saccades |
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Term
| 2 cortical areas particular important for smooth-pursuit movements |
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Definition
1. several small areas in the parietal lobe
2. the temporo-occipital junction |
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Term
| What is the middle temporal area (MT) important for? |
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Definition
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Term
| What does the middle superior temporal area (MST) respond preferentially to? |
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Definition
| moving visual stimuli in a specific direction |
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Term
| What ability is a prerequisite for voluntary slow-pursuit movements? |
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Definition
| the ability to fix the gaze |
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Term
| 3 cortical regions that become active in conjunction with directed attention (lesions to these areas produce an impaired ability to fix the gaze) |
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Definition
1. frontal eye field
2. anterior cingulate gyrus
3. prefrontal cortex |
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Term
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Definition
| an expression of the strong tendency to fix the gaze |
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