Cranial Nerves I-VI 21.02.23 Flashcards
Are the cranial nerves part of the CNS or PNS?
- PNS
- 12 pairs of cranial nerves: head and neck (except vagus which is odd one as it innervates thorax and abdomen etc)
- 31 pairs of spinal nerves
What is the function cranial nerves?
- Carry sensory/motor/autonomic information between the brain and the head and the neck
- Contain different combinations of fibre types (motor, general, sensory)
What are the 12 cranial nerves (names)?
I Olfactory
II Optic
III Oculomotor
IV Trochlear
V Trigeminal
VI Abducens
VII Facial
VIII Vestibulocochlear
IX Glossopharyngeal
X Vagus
XI Accessory
XII Hypoglossal
Are the 12 cranial nerves sensory, motor or both?
I Olfactory Some
II Optic Say
III Oculomotor Money
IV Trochlear Matters
V Trigeminal But
VI Abducens My
VII Facial Brother
VIII Vestibulocochlear Says
IX Glossopharyngeal Big
X Vagus Brains
XI Accessory Matter
XII Hypoglossal Most
Which four cranial nerves carry parasympathetic fibres?
III - Oculomotor
VII - Facial
IX - Glossopharyngeal
X - Vagus
How are sympathetic fibres carried?
Start in the spinal chord then they form a trunk and then innervate the head and neck. They are carried alongside the arteries entering the brain. They are not carried in cranial nerves
Which cranial nerves are found in the brainstem?
III - XII
What does carrying sensory or motor signals mean?
- Either receive sensory/ afferent input from the periphery
- Contain cells whose axons convey motor/ efferent signals to the periphery
- Some nerves with motor and sensory components have two separate nuclei
Where is the first cranial nerve connected to the brain?
- Not in the brainstem
- On the cerebrum
What is the function of the first cranial nerve?
Smell
what is the connection to the skull foramen of the first CN?
The cribriform plate
Where are the receptors for the first CN?
The nasal cavity
- Then axons travel through the cribriform plate to the olfactory bulb to the tracts then to the temporal lobe
What is the brain connection, function and skull foramen of the second CN?
Brain connection: Cerebrum (not brainstem)
Function: sight
Skull foramen: Optic canal
Where do the fibres of the second CN travel?
From the retina to the primary visual cortex. giving meaning to the images we see
How can we test the second CN?
- visual acuity (chart of letters)
- Visual fields
- Pupillary light reflex
- Fundoscopy (looking at retina when light shone into their eye)
What is the brain connection, function and skull foramen of the third CN?
Brain connection: Midbrain
Function: eye movements, eyelid opening, pupil constriction, accommodation
Skull foramen: superior orbital fissure
How does the pupillary light reflex work (direct and consensual response)?
When light is shone into one eye
- Ipsilateral pupil constricts (direct response)
- Contralateral pupil constricts (consensual response)
Is Pupil constriction parasympathetic or sympathetic?
parasympathetic - constriction so if that doesn’t work pupil will be dilated and vice versa for sympathetic
What is the brain connection, function and skull foramen of the fourth CN?
Brain Connection: midbrain
Function: eye movement (Superior oblique only)
Skull foramen: Superior orbital fissure
What would a deficit of this nerve result in?
Diplopia on looking down. inability to depress an adducted eye
- Only CN to leave brainstem posteriorly
What is the brain connection, function and skull foramen of the sixth CN?
Brain connection: pons
Function: eye movement (lateral rectus muscle only)
Skull foramen: superior orbital fissure
A deficit in this nerve would result in an inability to abduct the eye
How do we test the sixth cranial nerve?
able to look right but unable to look left
What are the three branches of the fifth CN?
The trigeminal nerve is split into:
V1. Ophthalmic
V2. Maxillary
V3. Mandibular
What is the brain connection, function and skull foramen of the fifth CN?
Brain connection: pons
Function: sensation to the anterior head and face AND motor to the muscles of mastication (chewing)
Skull foramen: V1 - superior orbital fissure, V2 - foramen rotundum, V3 - foramen ovale
What are the functions of the three branches of the trigeminal CN?
V1 - sensation from the anterior head (superior 1/3)and face including scalp, forehead, cornea and tip of the nose
V2 - Sensation from the face (middle 1/3) including cheek, nose and upper lip, upper teeth and palate
V3 - sensation from the face (inferior 1/3) including lower lip, lower teeth, chin, jaw, anterior 2/3 of the tongue and muscles of chewing
How do we test sensation of the fifth cranial nerve?
Test the general sensation over the face (compare the left and right) by touch and the three sections of the face
What does injury to the fifth nerve cause?
- Paralysis of muscles of mastication
- Pain in the face (trigeminal neuralgia)
