L37 Cranial Nerves Flashcards
Which cranial nerves are connected to the cerebrum?
Cranial nerves 1 & 2.
Olfactory nerve (I)
Optic nerve (II)
Which cranial nerves are connected to the brain stem?
Cranial nerves 3 to 12
How are cranial nerves arranged?
Cranial nerves are arranged in sequence from 1 to 12 anterior to posterior
What are the 3 divisions of the brain stem called?
Midbrain , Pons and Medulla oblongata.
The medulla oblongata is the part of the brainstem closest to the spine.
The pons Is the part of the brainstem which is between the midbrain and medulla oblongata.
Olfactory (I)
Purpose:
Composition:
Region/tissues supplied:
Foramen, fissure or canal it passes through:
Function(s) & simple tests:
Effects of nerve damage/lesions:
Sense of smell - purely sensory nerve.
It begins with olfactory receptors in the mucous membrane (up your nose) and those receptors are attached to axons which are given the name olfactory filaments.
Foramen: Olfactory filaments pass through cribform plate of ethmoid bone to olfactory bulbs underneath the brain and then via olfactory tracts to higher brain centres for conscious smell perception.
Olfactory filaments can be ruptured by head injury, causing loss of sense of smell (anosmia).
Optic nerve (II)
Purpose:
Composition:
Region/tissues supplied:
Foramen, fissure or canal it passes through:
Function(s) & simple tests:
Effects of nerve damage/lesions:
Vision - purely sensory.
Retinal ganglion cell axons leave the back of the eye to form the optic nerve. As they leave the back of the eye as the optic nerve they pass through a hole called the optic canal at the back of the orbit.
The optic nerve then continues towards the brain as the optic chaism then optic tract. The destination of these axons is to the lateral geniculate nucleus (LGN)of the thalamus (synapse).
The LGN axons then pass to the area of the brain responsible for conscious visual perception.
Tumours in the pituitary gland (adenomas) tend to grow upwards cutting nasal axons from both eyes as they cross in the chiasm —> leading to bi-lateral loss of the temporal half fields. This condition is called Bi-temporal hemi-Anopsia.
At the optic chiasm which axons cross the midline and which axons remain uncrossed?
At the optic chiasm, nasal retina axons cross the midline whereas temporal axons remain uncrossed.
What passes through the optic canal?
The optic nerve passes out through the optic canal.
The ophthalmic artery passes in through the optic nerve.
Where does the pituitary gland sit?
Directly below the optic chiasm
What does the prefix “an” or “a” suggest?
A lack of something (whatever follows).
Define fossa ( and where we might see this terminology)
Fossa - Latin for depression or cavity.
Used for cranial nomenclature e.g anterior fossa, middle fossa and posterior fossa.
What is the cribriform plate ?
A perforated plate present in the anterior fossa (of the ethmoid bone).
How can you identify the foramen magnum (hole) of the skull?
It is the biggest hole in the skull present at the bottom of the skull.
What does the foramen magnum contain?
The brainstem which connects to the spinal chord at that point
What is a frontal lobotomy ?
An outdated practice where the frontal lobes of the brain were disconnected from the rest of the brain in an attempt to ‘mellow’ schizophrenic and other such patients.
What is a fissure?
Narrow opening or line. (Think orbital fissure)
