Brainstem
The brainstem is made of 3 parts: the midbrain, pons and medulla oblongata.
It is a compact and intricate structure with lots of tracts and pathways as well as nuclei for processing. It is also where 10 of the 12 cranial nerves emerge from.
The brainstem is made of 3 sections, the midbrain, pons and medulla.
The midbrain
The midbrain is immediatly below the diencephalon and is a big bridge for motor sensory and autonomic function (basically everything).
Important superficial structures are:
- Cerebral peduncles Crus Cerebri - little feet of cerebrum NOT cerebellar peduncles these are fibres descending from the cores to the brainstem and spinal cord. They also help anchor the cerebrum to the brainstem.
- Corpora quadrigemia Quadruplets This is a group of 4 colliculi (hills), a pair of superior colliculi which deals with certain visual signals (like fast moving or flying objects) and the inferior colliculi which deals with reflexive responses to noises which startle you.
- Substantia nigra Black substance These are neurons which contain melanin, as it is a chemical precursor to dopamine. They are involves with dopamine release and are thus atrophied in parkinsons disease. It is functionally linked to the basal nuclei
- Red nucleus This has extensive blood supply, leading to its red colour. it is a relay nucleus in some motor pathways.
- Cerebral aquaduct This is the passage from the 3rd to 4th vetnricle
- superior cerebellar peduncles These are 1 of 3 peduncles and connect the cerebellum to the brainstem and CNS
The pons
The pons means bridge, and it is a major connection between the cerebral cortex, cerebellum and spinal cord. It also had nuclei involved with breathing sleep-wake cycles and arousal. it also the origin of 4 cranial nerves, 5-8.
it had the pontine nuclei and the pneumotaxic centre, together with the medullary centre
The medulla
The medulla connects the pons to the spinal cord and the cerebellum to the spinal cord. It has the pyramidal decussation and 4th ventricle. It also is the origin of cranial nerves 9-12. It has many reflex centres which are important in controlling heart beat, vasocular tone, breathing as well as more refelxes.