Cranial nerves Flashcards
What types of nerves can be in cranial nerves?
Somatic motor fibres:
- Supply striated muscle
Autonomic motor fibres (aka visceral motor fibres):
- Parasympathetic - supplies smooth muscle & glands
Visceral sensory/afferent:
- inputs from pharynx, larynx, heart, lung, gut etc - not normally conscious
General sensory:
- Touch, temp etc from skin & mucous membranes
Special sensory:
- taste, smell, vision, hearing & balance
Why is there no sympathetic motor fibres in the cranial nerves?
Parasympathetic outflow is Craniosacral
Sympathetic outflow is Thoracolumbar thus cant be through any cranial nerves
Where are the cell bodies located for:
- Sensory (afferent) fibres?
- Somatic motor (efferent) fibres?
- Autonomic motor (efferent) fibres?
Sensory (afferent):
- Cell bodies located within ganglia that are outside of the CNS (ie dorsal root ganglia)
Somatic motor (efferent):
- Cell bodies located within the CNS in ‘Nuclei’
Autonomic motor (efferent):
- Pre-ganglionic fibres have cell bodies within the CNS
- Post-ganglionic fibres have theirs in autonomic ganglia (outside of the CNS)
What type of nerve is the Olfactory nerve?
CN I
Sensory nerve (smell)
(special sensory)
Describe the anatomical pathway that signals travel through the Olfactory nerve?
- Receptors located in olfactory epithelium of nasal cavity - moves on to…
- Fibres through foraminifera in cribriform plate of ethmoid bone - after which the…
- Fibres enter olfactory bulb in ant. cranial fossa
What are the clinical applications of the Olfactory nerve?
A fractured cribriform plate may tear olfactory nerve fibres causing anosmia
What type of nerve is the Optic nerve?
CN II
Special sensory - vision
What is the pathway of the Optic nerve?
CN II
enters via optic canal, nerves join to form optic chiasm, fibres from medial (nasal) half of each retina cross to form optic tract
What are the clinical applications of the Optic nerve?
–increase in CSF pressure can cause papilloedema
–section of right optic nerve causes blindness through right eye
–section of optic chiasm causes loss of peripheral vision (bitemporal hemianopsia)
–section of right optic tract causes blindness in left temporal and right nasal fields (left homonymous hemianopsia)
What type of nerve is the Oculomotor nerve?
CN III
Motor - eye movement
Has both a Somatic and Autonomic aspect:
- Somatic motor - Extraocular muscles & eyelid
- Autonomic motor - Parasympathetic Pupil control
Describe the pathway of the Occulomotor nerve
CN III
Emerges from midbrain and exits via superior orbital fissure into orbit
What are the clinical applications of the oculomotor nerve?
CN III
–drooping of upper eyelid (ptosis)
–eyeball abducted and pointing down
–no pupillary reflex
–no accommodation of the lens
What type of nerve is the trochlear nerve?
CN IV
Somatic motor - eye movement
Motor information to superior oblique
What is the pathway of the trochlear nerve?
CN IV
emerges from dorsal surface of the mid brain and exits via the superior orbital fissure
What are the clinical applications of the trochlear nerve?
Diplopia when looking down
What type of nerve is the Abducens nerve?
CN VI
somatic motor - extraocular muscle (lateral rectus abducts the eye)
What is the pathway of the abducent nerve?
CN VI
emerges between pons and medulla and exits via the superior orbital fissure
What is the clinical application of the Abducent nerve?
CN VI
Medial deviation of the affected eye causing diplopia
What type of nerve is the Trigeminal nerve?
CN V
mixed (sensation from face & mouth, muscles of mastication)