Midbrain Flashcards
What are the surfaces of the midbrain?
Anterior
Posterior
What are the divisions of the midbrain?
Two halves each called cerebral peduncle
Which nerve arises from the medial border of the peduncle?
Oculomotor Nerve
What is the posterior surface of the midbrain called?
Tectum
What structures are formed from the tectum?
2 Superior Colliculi
2 Inferior Colliculi
Which nerve originates from the posterior surface of the tectum?
Trochlear Nerve
How is each Cerebral Peduncle divided?
Substantia Nigra divides peduncle into Crus Cerebri anteriorly and Tegmentum posteriorly
Crus Cerebri
Varying of the Crus Cerebri structure throughout the midbrain
Same structure throughout
Crus Cerebri
Fibers of the anterior part of the Crus Cerebri
Corticospinal fibers
Corticopontine fibers
Continue descending downwards converging at the pons
Substantia Nigra
Varying of the Substantia Nigra structure throughout the midbrain
Same structure throughout
Substantia Nigra
Structure
Lamina of grey matter formed of melanin pigmented nerve cells which synthesize dopamine
Substantia Nigra
Location
Behind the Crus Cerebri
Substantia Nigra
The Substantia Nigra is connected to the …
… Caudate Nucleus and Putamen of Basal Ganglia
Substantia Nigra
Damage to the Substatia Nigra causes …
… loss of dopamine secreting neurons leading to Parkinson’s Disease
Tegmentum
Location
Posterior to Substantia Nigra
Tegmentum
Components
Ascending Tracts
Nuclei
Tegmentum
Part of Tegmentum behind the aqueduct is called …
… Tectum
Tegmentum
Purpose of the Superior Colliculi
Reflex centres of vision
Tegmentum
Purpose of the Inferior Colliculi
Reflex centres of hearing
Tegmentum: Lower Midbrain at Inferior Colliculus
Structures
Nuclei
Ascending Tracts
Tegmentum: Lower Midbrain at Inferior Colliculus
Nuclei Names
Inferior Colliculus
Trochlear Nerve Nucleus
Mesencephalic Nucleus of Trigeminal
Decussation of Superior Cerebellar Peduncles
Tegmentum: Lower Midbrain at Inferior Colliculus
What fibers does the Inferior Colliculus Nucleus receive?
Ascending Auditory Fibers
Tegmentum: Lower Midbrain at Inferior Colliculus
Where do the fibers of the Inferior Colliculus Nucleus run?
In the Lateral Lemniscus
Tegmentum: Lower Midbrain at Inferior Colliculus
Location of the Trochlear Nerve Nucleus
Anterior to Cerebral Aqueduct
Tegmentum: Lower Midbrain at Inferior Colliculus
Trochlear Nerve Nucleus fiber pathway
Cross to opposite sides and emerge from back of midbrain
Tegmentum: Lower Midbrain at Inferior Colliculus
What does the Trochlear Nerve Nucleus supply?
Superior Oblique Muscle
Tegmentum: Lower Midbrain at Inferior Colliculus
What fibers does the Mesencephalic Nucleus of Trigeminal receive?
Proprioceptive fibers from Facial and Extra-Ocular Muscles and Muscles of Mastication
Tegmentum: Lower Midbrain at Inferior Colliculus
What is the Decussation of Superior Cerebellar Peduncles
Fibers of each peduncle cross to opposite sides in the central part of Tegmentum
Tegmentum: Lower Midbrain at Inferior Colliculus
Names of Ascending Tracts
Medial Lemniscus
Spinal Lemniscus
Trigeminal Lemniscus
Lateral Lemniscus
Anterior Spinocerebellar Tract
Tegmentum: Lower Midbrain at Inferior Colliculus
What is the Medial Lemniscus
Ascending fibers carrying prioperioceptive sensations from the opposite side of the body
Tegmentum: Lower Midbrain at Inferior Colliculus
The Medial Lemniscus is an upward continuation of …
… the Gracial and Cuneate tracts of the opposite side
Tegmentum: Upper Midbrain at Superior Colliculus
Nuclei Names
Superior Colliculus
Oculomotor nerve motor nucleus
Pretectal nucleus
Tegmentum: Upper Midbrain at Superior Colliculus
Superior Colliculus location
Upper part of tectum in midbrain
Tegmentum: Upper Midbrain at Superior Colliculus
Superior Colliculus nucleus is the centre of what impulses?
Visual Reflexes
Tegmentum: Upper Midbrain at Superior Colliculus
Oculomotor Nerve Nucleus Location
Anterior to aqueduct of midbrain
Tegmentum: Upper Midbrain at Superior Colliculus
Where do fibers of Oculomotor Nerve Nucleus emerge from?
Medial surface of crus cerebri
Tegmentum: Upper Midbrain at Superior Colliculus
What does the Oculomotor Nerve Nucleus supply?
Extra-ocular muscles of eye
Except for superior and lateral rectus muscles
Tegmentum: Upper Midbrain at Superior Colliculus
Pretectal Nucleus location
Dorsal to Superior Colliculus
Tegmentum: Upper Midbrain at Superior Colliculus
Pretectal Nucleus has connections with …
… parasympathetic nucleus of oculomotor nerves of both sides (Edinger-Westphal nucleus)
Tegmentum: Upper Midbrain at Superior Colliculus
Ascending Tract names
Medial Lemniscus
Spinal Lemniscus
Trigeminal Lemniscus
Anterior Spinocerebellar Tract
Which blood vessels supply the Medial Parts of the Crus Cerebri and Tegmentum?
Branches of Basilar Artery and Posterior Cerebral Artery
Which blood vessels supply the Lateral Parts of the Crus Cerebri and Tegmentum?
Branches of Posterior Cerebral and Superior Cerebellar