cranial nerves Flashcards
(15 cards)
what does the floor of the skull consist of ?
3 fossas:
1) anterior fossa
2) middle fossa
3) posterior fossa
what is the foramen magnum?
foreamen = hole
magnum = big
through the foramen magnum your brain stem connects to your spinal cord
CN1
olfactory nerve
- purely sensory nerve
- sense of smell
- begins with olfactory receptors in the nasal mucosa, these receptors are attached to axons, these axons pass through the cribriform plate of the ethmoid bone
- destination: olfactory bulb underneath the brain & then via olfactory tracts to higher brain centres
when is it important to test pls for a fault in the CN1?
is important to test ppl who have had a head injury, blow to front or back of head, causing loss of sense of smell
what is the term used to define “loss of sense to smell”?
anosmia
CNII
Optic nerve
- purely sensory nerve
- vision, sight
- begins with retinal ganglion cells, which leave the back of the eye to form the optic nerve
- when they leave the back of the eye, they pass through a hole called the optic canal
- the nerve then continues towards the brain as the optic chiasm and then optic tract
- destination: destination of the axons is mainly to LGN (lateral geniculate nucleus) of the thalamus (synapse)
- LGN will make axons of their own, which will pass to the area of the brain that is responsible for conscious visual perception
- when the 2 optic nerves (on the RHS & LHS) come together to form the optic chiasm. axons from the nasal side of retina cross the midline, but the temporal axons remain uncrossed
what is the destination of CNII?
destination of the axons is mainly to LGN (lateral geniculate nucleus) of the thalamus (synapse)
what are the 3 holes of the orbital cavity?
1) optic canal
2) superior orbital fissure
3) inferior orbital fissure
Why do some of the axons in the optics pathway cross the midline?
- there’s essentially a vertical line in the middle of your field of view, which splits the RHS from the LHS of the visual field
- the cornea + lens invert the image of the visual field
- lower part of the field of view is seen by the upper part of your eye
- Upper field of view seen by the lower part of the eye
- The image of what we’re looking at is inverted on the retina
fact
Damage to the axon at different optic pathways cause different visual field loss
how is bi-temporal hemi-anopsia caused?
Caused: by tumour in the pituitary gland
where does the pituitary gland sit ?
sits in a bony well directly below optic chiasm
bi-temporal hemi-anopsia
- tumour in the pituitary gland tends to be benign, so tend to grow slowly
–> tumours known as adenomas - tumour grows up as its surrounded by bones on either side, it can’t grow down or sidewards. It grows up (no bone there)
- as it grows it hits the optic chiasm
- it’s a split optic chiasm right at the midline, those axons are no longer reporting signals to the brain
- so px can’t see temporal field of vision in both RHS + LHS
From CNIII, CNIV, CNVI, which is the largest and why?
CNIII - Oculomotor
- supplies 3 of the ex
