Cranial nerves and the brainstem Flashcards
The brainstem consists of which structures
the midbrain, pons and medulla
Describe the structure of the midbrain
it is the most superior portion of the brainstem
in longitudinal section, there are three main components:
1. tectum (roof) which is made up of the superior and inferior colliculi
the 4th ventricle and the cerebral aquaduct are located between the tectum and tegmentum
- tegmentum which contacts CN nuclei, MLF, the reticular formation and sensory tracts (lemnisci)
- basis which contains the corticospinal and corticobulbar tracts
above the intact midbrain lies the cerebral peduncles
the oculomotor nerve arises from the front
the trochlear nerve arises from the back (longest CN)
it is commonly identified as having a Mickey Mouse face shape
contain the substantia nigra (basal ganglia dopamine input)
above the midbrain which cranial nerves are present
CN I, CN II
Describe the structure of the pons
it is the middle portion of the brainstem
it is attached to the cerebellum by three cerebellar peduncles. the trigeminal nerves are prominent when viewing the pons anteriorly eminating from it centrally.
Describe the structure of the medulla oblongata
it is the most inferior portion of the brainstem, as the spinal cord starts to appear
it has two medial bulges (known as the pyramids - where corticospinal tracts decussate) and two lateral bulges in addition to the pyramids known as the inferior olives
the posterior parts of the medulla are an extension of tracts from the spinal cord (the fasiculus gracilis and cuneatus)
CN 9, 10, 11, 12 emerge from the medulla
In embryology the neural tubes have two sections or plates which carry motor and sensory nuclei
these are known as the alar and basal plates which are demarcated by the sulcus limitans
In the spinal cord the motor nuclei are ventral and the sensory nuclei are dorsal, how does this compare with the brain stem
The neural tube has been flattened out like a book
so in the brain stem the motor nuclei are medial and the sensory nuclei are to the side or lateral
what is the definition of cranial nerves
cranial nerves are any major nerve that transverses skull foraminae
which cranial nerves have parasympathetic components
3,7,9 and 10
Motor cranial nerves are also known as efferents (they do things i.e. respond to stimuli) what are the categories of their function
1. general somatic tongue, extraocular muscles 2. general visceral glands and smooth muscle of viscera 3. special visceral striated muscle like the jaw, ear, face, laryngophaynx
Sensory cranial nerves are also known as afferents (they sense things i.e. detect stimuli) what are the categories of their function
1. general somatic touch, pain proprioception 2. general visceral cardiorespiratory, GIT 3. special somatic olfaction, vision, vestibular, auditory 4. special visceral taste
which cranial nerve exits the cribriform plate in the anterior fossa
the olfactory
what are the names of the middle fossa formainae for the CNs to exit from. what are the cranial nerves which exit from these foraminae in the middle cranial fossa.
optic foramen 2
superior orbital fissure 3, 4, V1, 6
rotundum V2
ovale V3
which cranial nerves exits from the internal auditory meatus
cranial nerve 8 - vestibulocochlear, but also 7 (but also follows the stylomastoid foramen
which cranial nerves exits from the jugular foramen
9, 10, and 11
