Cranial nerves Flashcards
Where are the receptors for CN I? where do their axons go?
Nasal mucosa; Axons travel through skull to the olfactory bulb; Information travels to medial temporal lobe of the cerebrum
loss of sense of smell
anosmia
- result from CN I damage
How do we lose function in CN I?
- Head injury – injure axons as they pass through the skull
- Smoking
- Excessive nasal secretions
- Chemicals
- These neurons can regenerate, and the sense of smell may return
What is the pathway that produce sight?
- Retina
- Optic Nerve - PNS
- Optic chiasm - Diencephalon
- Optic tract - CNS
- Lateral geniculate body/ nucleus – thalamus
- Primary Visual cortex
- Retinal field: middle of the eye and medial.
2. Retinal field: middle of the eye and lateral
- Nasal retinal fields
2. Temporal retinal field
R optic nerve carries info from? L optic nerve carries info from?
R eye; L eye
What fibers cross the midline in the optic chiasm?
Information from the nasal retinal field
The LGN and visual cortex receives information from the [ipsilateral/ contralateral] visual field.
Contralateral
R optic tract carries info from? L optic tract carries info from?
Vision from the L side of the world; Vision from the R side of the world
What visual field deficits will there be if there is injury to optic chiasm?
Bitemporal hemianopsia (nasal reticular fibers)
What is a common cause of bitemporal hemianopsia?
pituitary tumor
What visual field deficit will occur if there is injury anywhere past the optic chiasm?
homonymous hemianopsia - loss of cotralateral visual field from both sides
- Damage to optic radiations – may be just upper or lower contralateral quarter
What visual field deficit will you see if there is damage to the visual cortex?
homonymous hemianopsia with macular sparing
Where does CN III originate?
Midbrain
Where does CN IV originate?
Midbrain
- axons leave dorsal surface of brainstem
Where does CN VI originate?
Pons-medulla border
-cell bodies in pontine tegmentum
What are the somatic motor cell bodies of CN III parasympathetic cell bodies?
Oculomotor nucleus;
edinger-westphal nucleus in ciliary ganglia (constricts pupil, accommodation reflex)
What is CN VI’s function?
Abducens nerve - motor
- innervates lateral rectus muscle; abducts eye
What is the pupillary reflex stimulus and response? what is its afferent and efferent nerve?
Stimulus: Light that we shine into an eye
Response: pupil on that side constricts
Afferent nerve: Optic nerve
Efferent: Occulomotor
What is the consensual reflex stimulus and response? what is its afferent and efferent nerve?
Stimulus: shine light into an eye
Response: Constriction of the opposite pupil
Afferent nerve: Optic nerve
Efferent: Occulomotor nerve
What is the pathway for the pupillary and consensual reflex?
Retina –> Pretectal nucleus in midbrain –> parasympathetic nucleus of the oculomotor nerve –> Ciliary ganglion –> Pupillary sphincter