Cranial nerves Flashcards
What are cranial nerves part of?
Peripheral nervous system
How many cranial nerves are there?
12 pairs
Where do cranial nerves arise?
Irregular intervals from the CNS
What do cranial nerves supply?
Head and neck except for vagus nerves which also supply structures in the thorax and abdomen
How are cranial nerves named?
Have a name and roman numeral which relates to there order
What kind of axons do cranial nerve carry?
some will be mixed but some are purely sensory or purely motor or autonomics (don’t all carry autonomic nerves)
What does the brain stem adjoin?
The brain to the spinal cord
What is the brainstem important for?
Cadio-respiratory functions and maintaining consciousness
Where are most of the cranial nerve nuclei?
in the brain stem
What is a nuclei?
Collection of the cell bodies of nerve fibres that make up the whole cranial nerve
Label the brain, midbrain, pons and medulla and how many CNs there are
2,2,4,4
What two Cranial nerves come from the forebrain?
Olfactory
Optic
What number is the olfactory nerve?
I
What does the olfactory nerve do?
special sensory
sense of smell (olfaction)
What is the route of the olfactory nerve?
- Temporal lobe
- Olfactory tract and bulb
- Cribriform foramina (esmoid bone)
- Through roof of nose to top of nasal cavity
How is the olfactory nerve tested?
Not usually tested- ask if lost sense of smell
Test one nostril at a time- uses smelling salts or whatever you have e.g. coffee
What is anosmia?
Losing sense of smell
What is the most common reason for losing your sense of smell?
Common cold
What can cause a loss of sense of smell?
Head injury
Intracranial tumours at base of frontal lobe
What is the number of the optic nerve?
II
What is the function of the optic nerve?
Special sense
Vision
Where does the optic nerve travel?
- Visual cortex of the brain
- Optic canal
- Optic tract
- Chiasm
- Retina
How do you test the optic nerve?
Test one eye at a time
Visual tests
Testing pupil responses/reflexes
How can you see the optic nerve?
Use an opthalmoscope
Can see the optic disk- origin of optic nerve
What is a papillodema?
If intracranial pressure raises, optic disc may swell due to extension of meinges the nerve carries
What will lesions fot the retina or optic nerve cause?
Visual disturbance affecting only one eye
Where will lesions causing visual defects in both eyes occur?
Chiasm or further back
What can cause compression of the optic chiasm?
Pituitary tumour
What is the function of the occulomotor nerve?
- Motor
- Autonomic (parasympathetic)
- Moves the eye
- Opens eyelid
- Control lens and pupil of eye
- Innervates extra ocular muscles, LPS, Sphincter papillae, ciliary muscle
What is the number of the oculomotor nerve?
III