midbrain ppt Flashcards
What is the midbrain?
The midbrain is the shortest segment of the brainstem, measuring approximately 2cm in length.
Where is the midbrain situated?
in the posterior cranial fossa, with its superior part extending above the tentorial notch.
What are the functions of the midbrain?
- enables auditory and ocular reflexive movements,
- controls pain, mood, and breathing,
-promotes survival instincts, and - provides a passageway for pathways between the cerebral cortex and spinal cord.
What structures lie between the midbrain?
The midbrain lies between the thalamus (rostrally) and pons (caudally).
What marks the anterior surface of the midbrain?
The anterior surface is marked by the two stalks called the cerebral peduncles.
What is the interpeduncular fossa?
The interpeduncular fossa is bounded by the cerebral peduncles and contains important vascular and neural structures.
What is the tectum?
The posterior surface of the midbrain is called the tectum, which features four tubercles known as the superior and inferior colliculi.
What is the role of the periaqueductal gray matter?
The periaqueductal gray modulates pain by releasing endogenous opioids and connects to the somatosensory areas of the cerebral cortex.
What are the major parts of the midbrain?
The midbrain consists of two major parts: the cerebral peduncles and the tectum.
What is the function of the red nucleus?
The red nucleus adjusts the movements of the upper limbs to maintain body balance.
What pathways does the midbrain provide passage for?
The midbrain provides passage for several ascending pathways including the superior cerebellar peduncles and various lemnisci.
What is the substantia nigra?
The substantia nigra is a semilunar lamina of heavily pigmented neurons that contributes to the control of movements.
What cranial nerve nuclei are located in the midbrain?
The nuclei of the oculomotor (CN III), trochlear (CN IV), and trigeminal nerves (CN V) are located near the periaqueductal gray matter.
What is the function of the oculomotor nerve nucleus?
It provides fibers for the innervation of all extraocular muscles except for the superior oblique and lateral rectus muscles.
What is the role of the accessory oculomotor nucleus?
It innervates the ciliary and sphincter pupillae muscles, enabling miosis of the pupil.
What is the function of the trochlear nerve nucleus?
It innervates the superior oblique muscle.
What is the role of the mesencephalic nucleus of the trigeminal nerve?
It receives proprioceptive information from the muscles of the face.
What are the components of the red nucleus?
The red nucleus consists of the caudal (magnocellular) and rostral (parvocellular) portions.
What is the rubrospinal tract?
The rubrospinal tract originates from the magnocellular part of the red nucleus and adjusts upper limb movements.
What does the medial longitudinal fasciculus connect?
It connects the oculomotor, trochlear, abducens, Edinger-Westphal, vestibular, reticular, and spinal accessory nuclei.
What sensory information does the medial lemniscus carry?
It carries information about vibration, touch, proprioception, and pressure to the thalamus.
What is the function of the trigeminal lemniscus?
It carries tactile, pain, and temperature sensations from the head to the thalamus.
What does the lateral lemniscus convey?
It conveys auditory information from the cochlear nucleus to the contralateral inferior colliculus.
What is the location of the substantia nigra?
The substantia nigra is located between the crus cerebri and the mesencephalic tegmentum.
