Brainstem II: Midbrain Flashcards
3 components of midbrain
Tectum (2 suprior colliculi, 2 inferior colliculi)
Tegmentum (cerebral aqueduct, periaqueductal grey, red nucleus, decussation of SCPs, substantia nigra that separates tegmentum and crus cerebri)
crus cerebri (CBT and CST)
Cerebral peduncle = everything except tectum
What CN can you see exiting dorsally right below the inferior colliculus?
CN IV! (the only one that you can’t see from the front), comes out from dorsal part of brainstem
CNs associated with midbrain
CN III and IV
Match CNs in midbrain with which colliculus they associate with
CN III - superior colliculus
CN IV - inferior colliculus
Inferior colliculus important for what kind of pathways?
AUDITORY
Input and output for inferior colliculus?
Input from lateral leminiscus - originating from the superior olivary nucleus of the pons, and cochlear nuclei of medulla
Output to medial geniculate nucleus of thalamus
What is the periaqueductal grey rich in?
Enkephalins for modulation of autonomics and pain, closely associated with reticular system
Medial longitudinal fasiculus (MLF)
located right under nucleus of CN IV) , plays role in vision has fibers that go to III and IV and VI, helps coordinate muscles of eye with muscles of neck
What is the reticular formation/activating system for?
Important in wakefulness, serotonin, at the level of inf colliculus
Where does the decussation of the SCP occur?
Inferior colliculus (traveling to red nucleus and ventrolateral nucleus of thalamus
What important NTs are in substantia nigra?
Dopamine (important in Parkinsons) and GABA (from pars reticulata)
If you see the red nucleus and nuclei of CN III, what level of midbrain are you at?
superior colliculus
Superior colliculus is associated with what kind of pathways?
VISUAL
Inputs and outputs of superior colliculus?
Input from retina
output to cervical muscles for coordination of visual tracking
Superior colliculus contains nucleus of which CN?
CN III
Red nucleus
Prominent in superior colliculus.
Receives fibers from SCP (important for motor activity) and projects to flexor muscles as well as inferior olivary nucleus
Pretectal area is an important area in which location with respect to colliculi?
Above. at the extreme rostral end of the midbrian.
important in coordinating structures of eye
Edinger Westphal nucleus
presynaptic parasympathetic fibers of III to ciliary ganglion for pupillary constriction of pupillary light reflex as well as accomodation for near vision
Posterior commissure important for what?
coordinated movement of both eyes. (i.e. bilateral pupillary constriction when light is shined in one eye)
Weber’s syndrome
ipsilateral oculomotor (CN III) paralysis with contralateral upper motor neuron lesion (this is because decussation of CST is down in the medullary pyramids), hyperreflexia Results form vascular insufficiency in medial aspect of midbrain at level of superior colliculus
Benedikt’s syndrome
ipsilateral III paralysis with contralateral tremor (from substantia nigra) and possible contralateral somatosensory loss.
Vascular lesion to III and red nucleus and SCP, and medial leminiscus (dorsal columns) and possible STT
Gaze palsy (Parinaud’s syndrome)
from pineal tumor which affects pretectal area and posterior commissure. Upward gaze paralysis, large pupil, abnormal elevation of upper eyelid and paralysis of accommodation
