[Note] The Midbrain (Anatomy)

Preface: One of my first dives into Anatomy and neuroscience. Dont remember the source material but still good.

The Midbrain is one of three regions of the brain stem. it is next to the other two regions, the pons and medullia. The midbrain is the superior region and acts as a conduit between forebrain and the pons&cerebellum. It is the smallest of the three regions, at ~2cm in lengths. It travels through the opening in the Tentorium Cerebelli.

The midbrain is made up of 2 major parts, the paired cerebral penducles, and the tectum. the former is found at the internior surface, the latter is found at the posterior.

The Paired Cerebral Peducles (PCP) consist of the Crud Cerebri and the Tegmentum, which is separated by the Substantia Nigra.
The Crub Cerebri is found at the front/center of the PCP, and contains 3 decending pathways, from the Cerebral Cortex to the Brain Stem. These pathways include The Coricospinal, the Corticonuclear, and Corticopontine pathways. All together these are called the Longitudinal Pontine Fibers.

The Tegmentum contains the Reticular Cranial Nerve, and several Neural Pathways. Particularly the Oculomotor Nerve III, Trochlear Nerver (CN IV), One nuclea of Trigeminal Nerve (CN V). You can also find the Red Nucleus, which is used as input from the Cerebellum. Important output is done using the Rubrospinal Tract, which is part of the Extraparyamidal System, used for regulating Moto Neuron Activity.

Tectum contains the superior and inferior colliculi relay nuclei. These are known as the Corpora Quadrigemina. Superior Colliculi Nuclei is used for Visual information, While Inferior is for auditory.

The midbrain contain many important tracts. This includes the Ascending Tract, which goes up the Stem into the Cortext. The AT includes the Superior Cerbellar Peduncles (Carries proprioceptive info to the cerebrellum, and out of cerebrellum to the Red Nucleus), The Medial Longitudinal Fasculus (MLF), and the Medial Lemniscus Tract (MLT).

The midbrains blood supply comes from the Basilar Artery and its branches. The major vessels are the Posterior Cerbral Artery and its Peduncular Branches, the Superior Cerebellar Artery, the Posterior Chordial Artery, and the Interduncular Branches of the Basilar Artery.
Clinical examples of this part of brains relevance include Parkisons, which is the deterioration/destruction of Dopaminergic Neurons in the Pars Compacta of the Substantia Nigra. Because of Dopamins importance to movement and function, the deteriorating of this  area causes motor loss, tremors, instability and more.

Another example is Argyll Robertson Pupil (ARP). This is when a patient has abnormally small pupils in both eyes, that does not ready to change of light, but DO constrict when focused on nearby object. This is possibly caused by a lesion on the Sylvian Aqueduct being damages, causing problems communicating with the EWN fibers which connect to the eyes. This is a higly a specific sign of a Late Stage Syphilis,but it can also be signs of Diabetes, Tumors, and more.