Forebrain and Ventricles Flashcards
General functions of brainstem
Conduit - allows ascending and descending pathways to reach thalamus and cerebellum from spinal cord (relay nuclei)
Integrative - control of CVS, respiratory and consciousness (reticular formation), plus complex motor patterns such as balance
Cranial nerves - sight, hearing, equilibrium, gustation, reflex centres
Three sections of the brainstem
Midbrain, pons, medulla oblongata
Rostral to brainstem
Continuous with the diencephalon
Caudal to brainstem
Continous with spinal cord at level of foramen magnum
Vental to brainstem
Clivus of occipital bone
Dorsal to brainstem
Cerebellum
Number of cranial nerves from brainstem
10 out of 12
Ventricular origins
Midbrain from aqueduct
Pons (and cerebellum) from mesencephalon of fourth
Medulla from myelencephalon of fourth
Three areas always identified in cross section
Tectum (roof) - posterior, mainly in midbrain
Tegmentum - middle, crain nerve nuclei and tracts, reticular formation and some ascending/descending pathways
Basal - most anterior, descending fibres from cerebral cortex
Ventral view of medulla
Anterior median fissure in the centre
Lateral to the anterior median tissue are the pyramids, behind which are descending motor fibres (down the pyramidal tract)
At the base of the anterior median fissure is the decussation of pyramids where descending motor fibres cross over to the other side of the body
Lateral to the pyramids is the olives
Lateral to the olives is the anterolateral sulcus
CN XII (hypoglossal nerve) emerges between the pyramids and olives
CN IX and X are found lateral to the olives in the anterolateral sulcus
CN XI is found below CN X as CN IX, X and XI all exit through the jugular foramen, whereas CN XII leaves through the foramen magnum with the spinal cord
Dorsal view of medulla
Most medially is the posterior median fissure
Lateral to the posterior median fissure is the fasciculus gracilis - sensory information from lower limb (remember gracilis muscle)
Lateral to fasciculus gracilis is fasciculus cuneatus, carrying sensory information from the upper limbs
At the ventral end of the FG is the gracile tubercle, and ventral end of the FC is the cuneate tubercle. Tubercles contain cell bodies.
Opening at the ventral end of the posterior median fissure is the obex
Caudal vs rostral medulla
Caudal = closed medulla, central canal, more circular
Rostral medulla = open medulla, butterfly shaped and opening into fourth ventricle. Rostral also begins the ICP (inferior cerebellar peduncle) which is the connection between medulla and cerebellum
Junctions around the pons
Ventrally: Pontomesencephalic junction
Caudally: Pontomedullary junction
Function of the pons
Bridge between two cerebellar hemisphere
Basilar groove
Basilic artery runs down it
Down the centre line of the ventral surface
Cranial nerves from the pons
Most medial: VI
More lateral: VII
Most lateral: VIII
VII and VIII emerge in the cerebellopontine angle
VII is found deeper into caudal pons behind CN VI, so damage to CN VI can have the side effect of damage to CN VII
Divisions of the pons
SCP = superior cerebellar peduncle
MCP (more lateral) = middle cerebellar peduncle
ICP = inferior cerebellar peduncle
Notable features in imagine of pons
Horizontal fibres - connection two halves of cerebellum
Dorsal side of caudal pons opens into 4th ventricle
Midbrain location
Just above pontomesencephalic junction
Below the mammillary bodies of the hypothalamus
Cerebral peduncles
Connects the midbrain to the cerebrum
Contain descending motor fibres
Curve around either side of the mammillary bodies
Also known as crus cerebri
Between the peduncles is the intrapedunclar fossa where CN III emerges
Emergence of CN IV
Emerges from dorsal side, then loops around just ventral to the line of the pontomesencephalic junction
Only cranial nerve emerging from the dorsal side of the brainstem
Dorsal view of midbrain
Bumps are superior and inferior colliculi
Superior deals with visual information
Inferior deals with auditory information
Colliculi form the tectum of the midbrain
Reticulum
Complex, multisynaptic network of neurons in the tegmenjtum
Descending motor pathway via the reticular nuclei
Vital autonomic centres
Ascending Reticular Activating System (coma association)
Pain modulation
Sleep-wake cycle
Arousal
Blood supply to brainstem
A lot
Includes SCA, PCA, AICA and PICA
