The reciprocal inhibition of antagonistic muscle upon lateral gaze is explained by:
**Core Concept**
Reciprocal inhibition is a fundamental physiological principle in muscle physiology, describing the simultaneous contraction of agonist and relaxation of antagonist muscles to facilitate coordinated movement. In the context of lateral gaze, this concept is particularly relevant as the eyes move in a coordinated manner to maintain binocular vision.
**Why the Correct Answer is Right**
During lateral gaze, the medial and lateral rectus muscles act as agonist and antagonist pairs, respectively. When the eyes move laterally, the medial rectus muscle relaxes (inhibits) due to the activation of the lateral rectus muscle. This reciprocal inhibition is mediated by the cranial nerve III (oculomotor nerve) and cranial nerve VI (abducens nerve) pathways, which control the medial and lateral rectus muscles, respectively. The inhibition of the medial rectus muscle allows for smooth and coordinated lateral gaze.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not specifically relate to muscle physiology or the concept of reciprocal inhibition.
**Option B:** This option is incorrect as it refers to the yoke muscles, which are involved in vertical gaze, not lateral gaze.
**Option C:** This option is incorrect as it refers to the tonic labyrinthine reflex, which is related to balance and vestibular function, not muscle physiology.
**Clinical Pearl / High-Yield Fact**
Reciprocal inhibition is a critical concept in understanding oculomotor physiology, and its disruption can lead to various eye movement disorders, such as nystagmus and strabismus.
**Correct Answer: B. Yoke muscles are involved in vertical gaze, not lateral gaze.