Neuroanatomy part 1 Flashcards
1
Q
Brainstem
A
- Consists of Medulla Oblongated, Pons and Midbrain.
- Archaic name for brainstem: Bulb.
- Medulla oblongata continuous with spinal cord.
- Midbrain is continuous with the diencephalon.
2
Q
Posterior Surface of the Brainstem
A
- Covered by cerebellum.
- Can be viewed by cutting through cerebellar peduncles and removing the cerebellum.
- Cerebellar peduncles contains fibres coming to/going from cerebellum.
3
Q
Posterior Surface of the Brainstem (Medulla Oblongata)
A
- In midline: Posterior median sulcus continuous with that of spinal cord.
- Gracile tubercles are on either side of the sulcus; mark the position of the underlying gracile nucleus (nucleus gracilis)
- Inferior to the tubercles: Elongated elevations indicating the location of fasciculi gracilis and cuneatus (Fasciculis is a bundle of nerve fibres in CNS).
- Nuclei and tract are part of dorsal column/medial leminiscus system.
- Lateral to cuneate tubercle is an inconspicuos ridge, tuberculum cinerium, which marks the position of the dorsal (posterior) spinocerebellar tract and the more deeply situated spinal tract and spinal nucleus of the trigeminal nerve.
- Inferior part of medulla oblongata contains the continuation of the central canal of the spinal cord (this part of the medulla oblongata is sometmes called the closed portion of the medulla oblongata).
- Superior part of medulla oblongata forms part of floor of fourth ventricle.
- Here, the central canal has moved posteriorly and open out into the fourth ventricle - (Open portion of medulla oblongata).
4
Q
Posterior Surface of Brainstem (Pons)
A
-Forms the superior part of floor of fourth ventricle.
5
Q
Posterior Surface of Brainstem (Midbrain)
A
- Four rounded elevations: Superior and Inferior Colliculi (Corpora Quadrigemina).
- Superior colliculi are part of the visual system.
- Inferior colliculi are part of the auditory system.
- Superior Medullary Velum, a membrane, stretches between the two superior cerebellar peduncles.
- Trochlear nerves emerge through the superior medullary velum (only cranial nerves emerging from posterior aspect of brainstem.
6
Q
Anterior Surface of Brainstem (Medulla Oblongata)
A
- Anterior Median Fissure in midline.
- Longitudinal elevations on either side: Pyramids.
- Pyramids indicate the positions of the underlying Pyramidal/Corticospinal tracts (motor tracts; descending fibres of the ipsilateral cerebral cortex).
- Inferior part of medulla oblongata: Majority of corticospinal fibres cross over in the decussation of the pyramids.
- Lateral to pyramids are oval shaped elevations, the Olives, caused by the underlyingIinferior Olivary nuclei (have connections with cerebellum; involved in control of movement).
7
Q
Anterior Surface of Brainstem (Pons)
A
- Basal portion of pons.
- Contains transverse potine fibres (Pontocerebellar fibres) originating from pontine nuclei; They pass through the contralateral middle cerebellar peduncle to the cerebellar hemisphere.
- Point of attachment of the trigeminal nerve indicates the transition to the middle cerebellar peduncle.
- Transverse potine fibres obscure underlying corticospinal tracts.
- In midline: Groove for Basilar Artery (Basilar Sulcus)
8
Q
Anterior Surface of Brainstem (Midbrain)
A
- Either side: Crus Cerebri (Basis Pedunculi)
- Separated in midline by depression, the interpeduncular fossa (fossa and most of its contents are not part of the midbrain, but part of the hypothalamus).
- Crura contain descending fibres that are continuous with the internal capsules of the cerebral hemispheres.
9
Q
Floor of Fourth Ventricle (Rhomboid Fossa)
A
- Viewed when cerebellum (and thus roof of ventricle) is removed.
- Space of the fourth ventricle is continuous rostrally with the Cerebral Aqueduct of the midbrain and caudally with the central canal with the lower part of medulla oblongata.
- The transition between the medulla and pons is not clearly delinated, but the position of striae medullares give and approximate indication of the transition.
- The superior portion of the floor is part of the pons, and the inferior portion is part of the medulla oblongata.
- Diamond-shaped.
- Median sulcus divides the floor into two halves.
- Nerve fibres emerge from median sulcus approximately between the junction of the inferior 1/3 and superior 2/3 , and run laterally to enter the inferior cerebella puduncles = Striae medullares of fourth ventricle.
- Sulcus Limitans divides each half into medial and lateral areas.
- Vestibular nuclear complex lies deep to most of the lateral area (Vestibular area).
- Medial area has motor nuclei located deep to it and is called the Medial Eminence.
- Sulcus limitans widens at two areas to cause two shallow depressions; one superior to and one inferior to striae medullares.
- Depressions: Inferior and Superior Fovea.
- Caudal part of floor contains the Hypoglossal Trigone medially and Vagal Trigone laterally (rostral ends of hypoglossal nucleus and dorsal nucleus of vagus runs deep to trigones.
- Four trigones together resemble the tip of a pen (Calamus Scriptorius)
- A slight elevation in the medial eminence just rostral to the striae medullares is called the Facial Colliculus.
- Facial Colliculus is formed by fibres from the motor nucleus of the facial nerve looping over the Abducent Nucleus (Abducens)
- At rostral end of vestibular area is a small dark spot, called the Locus Coeruleus (Locus Cinereus/Substantia Ferruginia)
- Locus Coeruleus indicates the site of the cluster of noradrenegic neuron that contain melanin pigment.
- Lateral recess extends laterally from the widest part of the floor and leads to the lateral aperture of the fourth ventricle (foramen of Luschka) to open up into the subarachnoid space.
10
Q
Internal Features of Brainstem
A
- Ascending and descending fibre tracts.
- Brainstem nuclei
- Cranial nerve nuclei (receieve and send fibres from and to cranial nerves)
- Reticular formation, a complex matrix of neurons (Functions: control level of conciousness and regulate cardiovascular and repiratory systems.)
