Organisation of the Brainstem and Cranial Nerves Flashcards
Where does the brainstem lie? What are its major divisions?
Brainstem = a part of the CNS exclusive of the cerebellum which lies between the cerebrum and spinal cord.
Major divisions:
- Medulla oblongata
- Pons
- Midbrain
Label this.
Where are the colliculi found and what are their functions?
Roof of the midbrain - 4 bumps (“low lying hill”)
- Superior colliculi – important for the coordination of eye and head movements at the same time
- Inferior colliculi – auditory stimulus reflexes (for survival) e.g. turning your head in the direction of a loud noise
Describe the location of the pons relative to the ventricular system.
The pons makes up the floor of the 4th ventricle
Name an important unpaired, midline structure on the posterior aspect of the brainstem.
Pineal gland
Everything in the brainstem is bilateral except the pineal gland.
What is the role of the pineal gland?
It produces melatonin, which is involved in regulating the circadian rhythm
- Disrupted in people who work shifts
- Melatonin release is controlled by connections from retina to the pineal gland
Which cranial nerve emerges from the back of the brainstem?
Trochlear nerve CNIV - the only cranial nerve to emerge posteriorly from the brain stem
What is the role of CNIV?
It supplies the superior oblique muscle – one of the extrinsic muscles of the eye
It is one of the three nerves supplying the eyes
What structure defines the medulla in the dorsal aspect and what pathways are found within this structure?
Dorsal Columns – sensory pathways –fine touch and proprioception
Label this.
What three significant structures can be seen superior to the pons when viewing the brainstem from an anteroinferior view?
Optic Chiasm
Pituitary Stalk (infundibulum)
Mammillary Bodies
What are the mammillary bodies? What causes them to become dark?
“little breats” - involved in housekeeping, homeostasis and memory
They are the inferior part of the hypothalamus, part of the diencephalon – it is part of the limbic system
- Become dark due to chronic alcoholism causing neovascularisation.
Which cranial nerve emerges in the midline between the cerebral peduncles?
Oculomotor Nerve (CN III)
What are the cerebral peduncles? What is the significance of the word ‘peduncle’?
Peduncle is specifically a structure that has a functional (are the descending motor tracts coming from the motor cortex) AND structural role (it holds the cerebrum onto the brainstem)
Name the cranial nerve that emerges from the lateral aspect of the pons. What are its 3 branches?
Trigeminal (CN V) (motor and sensory) - ophthalmic, maxillary and mandibular nerves.
What is the role of this nerve? (CNV)
Touch and sensation throughout the head and neck
It has a small root next to the larger one as it emerges out of the transverse fibres – this is the motor root providing motor innervation of the muscles of mastication
Which three nerves emerge at the pontomedullary junction (from medial to lateral)?
Abducens, Facial, Vestibulocochlear (CN6,7,8)
Briefly state the role of each of these cranial nerves CN VI, VII, VIII (which emerge at the pontomedullary junction.
Abducens – innervates the lateral rectus which is involved in abducting the eye
Facial – innervates the muscles of facial expression and is involved in taste sensation for the anterior 2/3 of the tongue
Vestibulocochlear – involved in balance and hearing