brazerzkidailine.blogg.se - Medical term that means unequal pupil size

sends its axons in the trochlear (IV cranial) nerve.

controls the lateral rectus of the ipsilateral eye.

sends its axons in the abducens (VI cranial) nerve.

Activation of the motor neurons produces contraction of the innervated muscle. Three cranial motor nuclei provide efferent control of the extraocular muscles. The inferior rectus and superior oblique working together pull the eye downward without rotating the eye. To depress the eye while looking straight ahead, the inferior rectus and superior oblique contract together as the superior rectus and inferior oblique relax. The superior rectus and inferior oblique muscles working together pull the eye upward without rotating the eye. For example, to elevate the eye while looking straight ahead, the superior rectus and inferior oblique contract together as the inferior rectus and superior oblique relax. To direct the eye upward or downward, two muscles contract synergistically as the two antagonist muscles relax.

other movements: lateral rotation and abduction.

minor movements: lateral rotation and adduction.

other movements: medial rotation and abduction.

minor movements: medial rotation and adduction.

Four other extraocular muscles working together control vertical eye movements and eye rotation around the mid-orbital axis (Figure 8.1, right). The actions of these two muscles are antagonistic: one muscle must relax while the other contracts to execute horizontal eye movements.

Contraction of the lateral rectus pulls the eye away from the nose ( abduction or lateral movement).

Contraction of the medial rectus pulls the eye towards the nose ( adduction or medial movement).

Two extraocular muscles, the medial rectus and lateral rectus, work together to control horizontal eye movements (Figure 8.1, left). Antagonistic actions pull the eye in opposite directions whereas synergistic actions pull the eye in the same direction.įor each eye, six muscles work together to control eye position and movement. The extraocular muscles of the right eye and their actions. The cranial lower motor neurons innervate these muscles and thereby control their contractions. Contraction of the muscles produce movement of the eyes within the orbit. The muscles are attached to the sclera of the eye at one end and are anchored to the bony orbit of the eye at their opposite ends. The extraocular muscles execute eye movements and are innervated by three cranial nerves. When this fails, diplopia (double vision) results.Ĩ.2 Extraocular Muscles and their Innervation

They coordinate the movement of the two eyes to ensure that the images on the two retinas fall on corresponding areas of the binocular field. Such eye movements are controlled by gaze systems. Eye movements are also controlled to direct the eyes towards a visual target and to follow the movements of the visual target. For example, in addition to producing adjustments in pupil size and lens refraction, accommodation involves the convergence of the two eyes to direct onto the foveae the images of near objects. Normal visual perception requires the proper functioning of ocular motor systems that control the position and movement of the eyes to focus the image of the object-of-interest (i.e., the visual target) on corresponding areas of the retinas of the two eyes.