Lecture 12-Midbrain Flashcards
What is the unique pathway of the trochlear nucleus in the brainstem?
The trochlear nucleus features a distinctive pathway where its fascicles leave laterally, wrap around the periaqueductal gray (PAG) matter, decussate, and exit below the inferior colliculus in the rostral pons or caudal midbrain.
Which cranial nerve has the only dorsal exit?
The trochlear nerve (CN IV) is the only cranial nerve with a dorsal exit.
What is the primary muscle innervated by the trochlear nucleus, and what kind of eye movement does it control?
The trochlear nucleus primarily innervates the superior oblique muscle of the eye, leading to a “down and out” turning movement.
What is the pathway of efferent projections to the eyes?
Efferent projections to the eyes rise through the Medial Longitudinal Fasciculus (MLF) to reach the oculomotor nuclear complex
Oculomotor Nuclear Complex
Includes the oculomotor nuclei and Edinger-Westphal nuclei.
How do the oculomotor nuclei project and where do they exit?
The oculomotor nuclei project ventrally and exit at the ventral boundary of the pons and midbrain.
Which extraocular muscles do the oculomotor nuclei project to?
The oculomotor nuclei project to four out of the six extraocular muscles: superior, inferior, and medial rectus muscles, as well as the inferior oblique muscle. They also project to the levator palpebrae muscle.
What muscles does the oculomotor nuclei not project to?
The muscles they do not innervate are the lateral rectus muscle and the superior oblique muscle. These muscles are primarily controlled by the abducens nerve (CN VI) and the trochlear nerve (CN IV), respectively
What are the two distinct populations of neurons in the Edinger-Westphal (EW) nuclei?
Consist of two distinct populations of neurons: EW preganglionic parasympathetic (EWpg) neurons and EW centrally-projecting (EWcp) neurons.
What is the primary function of EW preganglionic parasympathetic (EWpg) neurons?
EWpg neurons follow the oculomotor nerve to innervate the sphincter pupillae and ciliary muscles, controlling pupil dilation and accommodation.
Where do EW centrally-projecting (EWcp) neurons project?
EW centrally-projecting (EWcp) neurons project to various nuclei in the brain and spinal cord, playing a role in a range of fdiplpunctions beyond pupillary and ciliary muscle control.
What information does the superior colliculus receive?
1) afferent fibres from retina,
2)corticotectal fibres from FEF (tracking moving object)
3) Corticotectal fibres from visual cortex (accommodation)
4) Auditory information from inferior colliculus (audiovisual reflexes)
Which structure in the auditory system is associated with dorsal nuclei and commissure?
The inferior colliculus is associated with dorsal nuclei and commissure in the auditory system.
Where do the efferent projections from the brachium of the inferior colliculus extend to?
The efferent projections from the brachium of the inferior colliculus extend to the superior colliculus and the medial geniculate nucleus in the thalamus.
What is the pathway of afferent projections to the inferior colliculus in the auditory system?
Afferent projections to the inferior colliculus originate from various auditory nuclei in the pons and medulla and travel up the lateral lemniscus.
What is the general role of the tectum across different species?
The tectum is involved in localizing and responding to stimuli in body-centered space.