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Midbrain and Pretectum
N/A
40
Anatomy
Graduate
03/02/2012

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Cards

Term
What is the developmental origin of the midbrain?
Definition
Mesencephalon
Term
What make up the tectum of the midbrain?
Definition
Acts as roof of the midbrain, consists of the superior and inferior colliculi
Term
What makes up the tegmentum of the midbrain?
Definition
Nuclear area and fiber tracts around the ventricle, includes the periaqueductal grey and red nucleus
Term
What make up the basis pedunculi of the midbrain?
Definition
Crus cerebri and the substantia nigra
Term
The large bundle of descending tracts originating from the cerebrum that is found in the midbrain is known as what?
Definition
Crus cerebri
Term
The space between the peduncles on the ventral surface of the midbrain is known as what?
Definition
Interpeduncular fossa
Term
What nerve exits from the interpeduncular fossa?
Definition
CN III (oculomotor n.)
Term
What GSE function does CN III (oculomotor n.) serve?
Definition
Motor to the levator palpebrae muscles and the 4 extraocular muscles - superior, medial, and inferior rectus and the inferior oblique
Term
What GVE function does CN III (oculomotor n.) serve?
Definition
Preganglionic parasympathetic fibers to ciliary ganglion which innervates sphincter pupillae and ciliary muscles
Term
What does CN III (oculomotor n.) arise from?
Definition
Oculomotor nucleus
Term
Where is the Edinger-Westphal nucleus located?
Definition
ANterior median part of the oculomotor complex
Term
What is the function of the Edinger-Wesphal nucleus?
Definition
Axons run alongside CN III from the ciliary ganglion, is affected by pressure and causes pupil dilation if conduction is blocked
Term
Where is the CN IV (trochlear n.) nucleus located?
Definition
Midbrain at the level of the inferior colliculus
Term
What is unique about how CN IV (trochlear n.) exits from the brainstem?
Definition
Only cranial nerve to exit dorsally from the brainstem
Term
CN IV (trochlear n.) supplies GSE motor innervation to what structures?
Definition
Superior oblique muscle which intorts and depresses the eye. Lesions result in difficulty going down stairs
Term
What is the function of the superior colliculus?
Definition
Coordinates reflexes to visual stimuli via conjugate eye movements, reflex closure of the eye, and accommodation focusing of lens for near vision
Term
What efferent tracts are found int he superior colliculus?
Definition
Tectobulbar and tectospinal tracts
Term
What is the function of the tectobulbar tract?
Definition
Controls eye movements, reflex closure
Term
What is the function of the tectospinal tract?
Definition
Crossed to upper spinal cord for neck muscle used in tracking objects in the visual field
Term
What is the function of the inferior colliculus?
Definition
Acts as a nuclear relay station of the auditory pathway and coordinates reflexes to auditory stimuli with the help of the superior colliculus and the tectobulbospinal tract
Term
What is the main afferent input of the inferior colliculus?
Definition
Lateral lemniscus which is the fiber tract primarily originating in the cochlear nuclei
Term
What is the main efferent output of the inferior colliculus?
Definition
To inferior brachium which connects it to the medial geniculate nucleus of the thalamus
Term
What are the main afferents of the red nucleus?
Definition
From cerebellar nuclei via the superior cerebellar peduncle as well as corticorubral fibers for motor function
Term
What are the main efferents of the red nucleus?
Definition
Rubrospinal tract - crossed spinal projection that is flexor biased to upper limb
Term
What are the two divisions of the substantia nigra?
Definition
Pars compacta and pars reticulata
Term
What neurotransmitter is found in the pars compacta?
Definition
Contains dark pigments of neuromelanin that is a complex of the neurotransmitter dopamine
Term
Spontaneous degeneration of pars compacta neurons is associated with what disease?
Definition
Idiopathic Parkinson's disease
Term
What neurotransmitter is found in the pars reticulata?
Definition
GABAergic neurons that project to the thalamus and serve as an output nucleus of the basal ganglia system
Term
What are the major connections of the substantia nigra?
Definition
Reciprocal contacts with subcortical motor nuclei such as the corpus striatum and subthalamic nucleus which are associated with basal ganglia
Term
What type or neurotransmitter receptor neurons are found in the ventral tegmental area?
Definition
Dopaminergic neurons
Term
The ventral tegmental area of the midbrain projects to what areas?
Definition
Areas associated with the limbic system such as the hippocampus, hypothalamus, and ventral striatum. Associated with the central reward pathways and possible mental disorders
Term
What are the major divisions of the crus cerebri from medial to lateral within the midbrain?
Definition
Fronotpontine, corticobulbar, corticospinal, and parietotemporopontine tracts
Term
Where do the descending fiber tracts of the crus cerebri originate?
Definition
Cerebral cortex
Term
Where is the nuclei of the pretectum located?
Definition
Found rostral to the superior colliculus at the level of the posterior commissure
Term
What is located at the pretectum nuclei?
Definition
Contains five nuclei related to visual function - Nucleus of the optic tract, sublentiform nucleus, nucleus of the pretectal area, pretectal olivary nucleus, principal pretectal nucleus
Term
What is the function of the prectum nuclei?
Definition
Receives fibers from the optic tract, lateral geniculate nucleus, cortex, and posterior thalamic nuclei and mediates the pupillary light reflex. Large lesions are required to impair this reflex
Term
What mediates the vertical conjugate gaze mechanism?
Definition
Vertical gaze center in the midbrain-diencephalon junction
Term
What is the primary nucleus of vertical gaze center?
Definition
Rostral interstitial nucleus of the medial longitudinal fasciculus
Term
What nuclei aids the vertical gaze center to hold eye position in vertical gaze as well as in coordination of rotary eye movements?
Definition
Interstitial nucleus of cajal
Term
How does the interstitial nucleus of cajal and the rostral interstitial nucleus of the medial longitudinal fasciculus communicate?
Definition
Via posterior commissure
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