brainstem Flashcards
brainstem
mesencephalon (midbrain) + pons + medulla oblongata
Functions
Conduit for ascending (sensory) & descending (motor) tracts
• Contains nuclei of cranial nerves III to XII (head’s equivalent of spinal nerves + special sensory)
• Reticular formation reticula = network
• Visceral reflex centres (respiratory & cardiovascular CPG’s)
• Muscle tone & postural reflexes
• Level of arousal / consciousness
• Modulation of pain transmission
BLOOD SUPPLY
vertebrobasilar system
Mesencephalon
Cerebral peduncles •Crus cerebri •Interpeduncular fossa •CN III •Superiorcolliculi (littlehills) •Inferior colliculi •CN IV
Pons
- Transverse fibres
- CN V
- CN VI
- CN VII & VIII
- Superior cerebellar peduncles
- Superior medullary velum
- Middle cerebellar peduncles
- Rostral floor of the 4th ventricle
- Median sulcus
- Medial eminence
- Sulcus limitans
- Facial colliculus
- Vestibular area
Medulla oblongata:
- Anterior median fissure
- Pyramids
- Decussation of pyramids
- Anterolateral sulci
- Olives
- CN IX, X, XI
- CN XII
- Open medulla
- Inferior cerebellar peduncles
- Closed medulla
- Gracile tubercle
- Cuneate tubercle
The internal structure of the brainstem can be divided anteroposteriorly into 3 longitudinal layers:
- Base = descending projection fibres (motor pathways)
- Tegmentum = ascending sensory pathways & descending extrapyramidal pathways;
cranial nerve nuclei; reticular formation neurons 3. 3. Tectum (roof) = superior & inferior colliculi in the midbrain
Reticular formation
- Network of neurons located in the tegmentum of the brainstem
- Large fields of dendrites allow them to receive inputs from multiple sources
- Extensive connections
- Spinal cord
- Throughout brainstem
- Diencephalon
- Basal nuclei
- Cerebral cortex
Reticular formation FUNCTIONS
- Control of movement (connections with cerebellum; CPG’s)
- Cranial nerve reflexes
- Visceral reflexes
- Modulation of pain
- Control of arousal and consciousness
Location of sensory & motor cranial nerve nuclei in the brainstem: Spinal cord
Sulcus limitans separates dorsal sensory from ventral motor
Location of sensory & motor cranial nerve nuclei in the brainstem: rostral medulla / caudal pons
Sulcus limitans separates
lateral sensory from
medial motor cranial nerve nuclei
Mesencephalon
•Cerebral peduncles
•Crus cerebri
•Substantia nigra
•Level of superior colliculus = oculomotor N & red nucleus* - *processes information
going from cerebellum to thalamus
•Level of inferior colliculus = trochlea N
Features of a lower cervical spinal cord cross section
- oval shape
- large amount of white matter
- fasciculus cuneatus & fasciculus gracilis
wide base of the ventral horn
Features of a thoracic spinal cord cross section
- lateral horn present
- narrow ventral horn
- Clarke’s nucleus present
- fasciculus cuneatus present in levels above T6, absent below
Clarke’s nucleus
extends from C8 to L3. It is formed by cell bodies of sensory neurons transmitting nonconscious proprioceptive information.
