Midbrain Flashcards
What is the periaqueductal gray?
It surrounds the cerebral aqueduct. It is thought to be involved in the perception of pain.
What is the tectum?
It is located dorsal to the midbrain central gray. It includes superior and inferior colliculi and receives visual and auditory information.
What is the tegmentum?
It is the main portion of the midbrain and lies inferior to the central grey. It includes the nuclei for CN II, IV, red nucleus, long tracts and the decussation of the superior cerebellar peduncles.
What are the cerebral peduncles?
Includes corticospinal, corticobulbar and corticopontine fibers.
What is the substantia nigra?
It separates the cerebral peduncles from the tegmentum. it produces dopamine. It is the major source of dopaminergic input to the caudate and putamen and the nigrostriatal pathway
What is the VTA?
it is in the medial aspect of the ventral midbrain. Dopamine neurons of the mesolimbic tract that originate in the VTA project to the cortex and limbic structures.
What is the red nucleus?
It is located in the midbraintegmentum and receives fibers from the cerebellum. They comprise one component of the superior cerebellar peduncle.
What is the inferior colliculus?
It is a collection of nuclei that receives input from the lateral lemiscus. The brachium of the inferior colliculus projects to the medial geniculate body of the thalamus which in turn projects ot primary auditory cortex in the temporal lobe.
What is the superior colliculus?
It is a collection of nuclei that receives input from the retina via the brachium of the superior colliculus. It is concerned with reflexes that influence the position of the head and eyes in response to visual cues and auditory stimuli. Fibers from here cross and descend to cervical segments in the Tectospinal Tract.
Nucleus of the trochlear nerve
The nucleus of the trochlear nerve is present in the tegmentum at caudal lvels of the midbrain. Rootlets cross before they exit the dorsal surface of the brainstem just caudal to the inferior colliculi. It is the only cranial nerve that crosses before exiting the brainstem. It is the only cranial nerve that exists from the dorsal aspect of the brainstem.
Nucleus of the oculomotor nerve
Present in the tegmentum at sueprior levels of the midbrain. It innervates the levator plapebrae and all extraocular muscles except the superior oblique and lateral rectus.
Edinger-Westphal Nucleus
Parasympathetic preganglionic cells. THey project to the ipsilteral ciliary ganglion which innervates the pupillary sphincter.
