oculomotor nerve development

Definition

Target type: biologicalprocess

The process whose specific outcome is the progression of the oculomotor nerve over time, from its formation to the mature structure. This motor nerve innervates all extraocular muscles except the superior oblique and the lateral rectus muscles. The superior division supplies the levator palpebrae superioris and superior rectus muscles. The inferior division supplies the medial rectus, inferior rectus and inferior oblique muscles. This nerve also innervates the striated muscles of the eyelid. Pupillary constriction and lens movement are mediated by this nerve for near vision. In the orbit the inferior division sends branches that enter the ciliary ganglion where they form functional contacts (synapses) with the ganglion cells. The ganglion cells send nerve fibers into the back of the eye where they travel to ultimately innervate the ciliary muscle and the constrictor pupillae muscle. [GO_REF:0000021, GOC:cls, GOC:dgh, GOC:dph, GOC:jid, ISBN:0838580343]

The oculomotor nerve, the third cranial nerve, controls eye movements, pupil constriction, and eyelid elevation. Its development is a complex process that begins during embryogenesis and continues into adulthood. Here's a detailed description:

**Early Development:**

* **Neural Tube Formation:** The oculomotor nerve arises from the basal plate of the midbrain, a region of the developing brain that forms during neurulation.
* **Neurogenesis:** Specialized progenitor cells in the midbrain give rise to neurons and glial cells that will constitute the nerve.
* **Migration:** Neurons migrate from their birthplace in the midbrain to their final locations within the oculomotor nucleus, a collection of nerve cell bodies that controls the nerve's functions.

**Axon Growth and Targeting:**

* **Axon Outgrowth:** As neurons mature, they extend axons, long projections that transmit nerve impulses. Oculomotor nerve axons grow from the oculomotor nucleus towards their targets, which include the four extraocular muscles that control eye movements (superior rectus, medial rectus, inferior rectus, and inferior oblique), the levator palpebrae superioris muscle (which lifts the eyelid), and the ciliary ganglion (which controls pupil constriction).
* **Guidance Cues:** The path of axon growth is guided by a complex interplay of attractive and repulsive cues present in the surrounding environment. These cues include molecules like netrins, semaphorins, and ephrins, which act as signals to direct the axons towards their correct targets.
* **Target Recognition:** Axons from the oculomotor nerve recognize and establish synapses with their specific target muscle fibers or neurons within the ciliary ganglion. This recognition involves interactions between specific receptors on the axons and ligands expressed by the target cells.

**Myelination and Maturation:**

* **Myelination:** Once axons reach their targets, they become wrapped in myelin, a fatty substance that insulates the nerve and increases the speed of signal transmission. This process is carried out by glial cells called oligodendrocytes in the central nervous system.
* **Synapse Formation:** As the nerve matures, the synapses between the oculomotor nerve and its target muscles and neurons become refined and stabilized. This involves changes in the structure and function of the synapses, ensuring efficient and reliable communication between the nerve and its targets.

**Later Development:**

* **Plasticity:** The oculomotor nerve retains some degree of plasticity even in adulthood, allowing it to adapt to changes in the environment or injury. For example, if one oculomotor nerve is damaged, the other eye may take over some of the functions of the damaged nerve.
* **Age-Related Changes:** As we age, the oculomotor nerve can undergo some age-related changes, such as a reduction in the number of neurons and the speed of nerve conduction. These changes can contribute to age-related eye conditions like presbyopia (difficulty focusing on near objects).

The development of the oculomotor nerve is a complex and precise process that is essential for proper eye function. Any disruption in this process can lead to a variety of eye disorders, including strabismus (crossed eyes), ptosis (drooping eyelid), and nystagmus (involuntary eye movements). '
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Proteins (1)

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