Innervations and reflexes Flashcards
How many nerves are involved with the eye?
8
What are the 8 nerves involved with the eye?
Facial CNVII Abducens CNVI Trochlea CNIV Oculomotor CNIII Short ciliary nerve Optic nerve CNII Trigeminal Ophthalmic nerve CNV1 Sympathetic motor/Long ciliary nerve
What four nerve types are present in the eye?
Autonomic sensory
Autonomic parasympathetic
Autonomic sympathetic
Somatic motor
Which two nerves provide sensory input from the eyes?
Optic nerve CNII
Trigeminal ophthalmic nerve CNV1
What type of stimuli does the optic nerve (CNII) sense?
Light
What type of stimuli does the ophthalmic nerve sense?
Mechanical
What nerve supplies sensory information from the face?
Trigeminal
What to branches of the trigeminal nerve are important for sensing the eye?
V1
V2
What area of the face does the CNV1 nerve cover?
Forehead, upper eyelid, cornea, conjunctiva, bridge of nose.
What area of the face does the CNV2 nerve cover?
Lower eyelid, maxilla, upper lip and side of nose
How is the parasympathetic outflow described?
Craniosacral
What cranial nerves provide the cranial outflow of the parasympathetics?
CNIII
CNVII
CNIX
CNX
Which cranial nerves are parasympathetic?
CNIII
CNVII
CNIX
CNX
Where do parasympathetic fibres synapse from presynaptic to postsynaptic?
Near their target organ
Describe sympathetic axons
Presynaptic sympathetic spinal nerves exit SC between T1 and L2 where they synapse in the sympathetic chain next to the SC. From here postsynaptic splanchnic nerves go to organs and body wall.
What are spinal nerves made up of?
Anterior and posterior rami
Where are the sympathetic chains located?
Parallel to the SC
What do splanchnic nerves do?
Supply the organs
What does splanchnic mean?
Relating to viscera
What happens at the cervical ganglia?
Postsynaptic splanchnic nerves to organs of the head branch off.
Where do the postsynaptic splanchnic nerves to organs of the head branch off?
Cervical ganglia
What are the postsynaptic splanchnic nerves to the organs of the head called?
Internal and external carotid nerves
Where do the internal and external carotid nerves run?
Along the internal and external carotid arteries
What do the internal and external carotid nerves form?
Periarterial sympathetic plexus
What vessel carries the sympathetic nerve input to the orbit?
Ophthalmic artery
What two tissues related to the eye receive sympathetic input?
Levator Palpebrae Superioris
Dilator pupillae
How does the dilator pupillae receive its sympathetic input?
Long ciliary nerve
What flows through the centre of the optic nerve?
Central artery and vein of the retina
Where does the ophthalmic nerve enter the orbit?
Superior orbital fissure
Where does the optic nerve exit the orbit?
Optic canal
What three nerves supply somatic motor innervation to the eye?
Oculomotor CNIII
Trochlea CNIV
Abducens CNVI
What does the abducens CNVI innervate?
Lateral rectus
What does the trochlea CNIV innervate?
Superior oblique
What does the oculomotor CNIII innervate?
Superior, inferior and medial rectus
Inferior oblique
Levator Palpebrae Superioris
Ciliary ganglion
In addition to somatic motor what other fibres does the oculomotor CNIII carry and where to?
Parasympathetic to ciliary ganglion
What arises from the ciliary ganglion?
SHort ciliary nerve
What does the short ciliary nerve innervate?
Ciliary muscles
Sphincter pupillae
Is the short ciliary nerve sympathetic or parasympathetic?
Parasympathetic
What nerves synapse, arise and pass through the ciliary ganglion?
Synapse- CNIII
Arise- SHort ciliary
Pass through- Long ciliary
In addition to the CNIII/Short ciliary nerve what other parasympathetic nerve is involved with the eye?
Facial CNVII nerve
What does the facial CNVII nerve innervate?
Orbicularis oculi
Lacrimal gland
Where does the oculomotor CNIII enter the orbit?
Superior orbital fissure
What two features does the oculomotor (CNIII) nerve pass through to reach the eye?
Cavernous sinus
Superior orbital fissure
How many divisions does the oculomotor nerve have?
2:
Superior
Inferior
Which divisions of the oculomotor nerve (CNIII) supply which muscles?
Superior- SR and LPS
Inferior- IR, MR, IO and ciliary muscles
Where does the CNIII (Oculomotor) arise?
Between pons and midline
Where is the pons found?
Brainstem
What does pons mean?
‘Bridge’
What do ciliary nerves do?
Control iris and ciliary muscles
What do ciliary muscles do?
Control lens focus
What do iris muscles do?
Control aperture
Where do all ciliary nerves pass through or arise from?
Ciliary ganglion
What two types of ciliary nerve are there?
Long ciliary nerve
Short ciliary nerve
Are long ciliary nerves sympathetic or parasympathetic?
Sympathetic
Are short ciliary nerves sympathetic or parasympathetic?
Parasympathetic
Where does the trochlear nerve CNIV enter the orbit?
Superior orbital fissure
What does the trochlear nerve pass through?
Cavernous sinus
Where does the abducens nerve CNVI enter the orbit?
Superior orbital fissure
What does the abducens nerve pass through?
Cavernous sinus
Which nerves enter the orbit through the superior orbital fissure?
Oculomotor CNIII
Trochlear VNIV
Ophthalmic CNV1
Abducens CNVI
Which nerves pass through the cavernous sinus?
Oculomotor CNIII
Trochlear VNIV
Ophthalmic CNV1
Abducens CNVI
Where does the optic nerve pass in relation to the cavernous sinus?
Superiorly
Where does the facial CNVII nerve arise from?
Pons (in brain stem)
Where does the abducens CNVI nerve arise from?
Pons/medulla junction
Where does the trochlear CNIV nerve arise from?
Dorsal brain stem
Where does the trigeminal CNV nerve arise from?
Pons
Where does the optic nerve arise from?
Forebrain
Which nerves are involved in the blink reflex?
CNV1
CNV
CNVII
Describe the blink/corneal reflex
Adverse stimuli activates CNV1 fibres in cornea
CNV1 pass to trigeminal ganglion where they become CNV fibres
CNV fibres integrate in pons in brainstem
Pons activates CNVII fibres which cause closure of eyelid.
Where is the ciliary ganglion located?
Posterior orbit
Which nerve innervates the SR, IR, MR, IO, LPS and ciliary ganglia?
CNIII
What nerve innervates the SO?
Trochlear
What nerve innervates the LR?
Abducens
What does the sphincter pupillae muscle do and what innervates it?
Constricts iris
Parasympathetic short ciliary nerve
What does the dilator pupillae do and what innervates it?
Dilates iris
Sympathetic long ciliary nerve
Describe the pupillae muscles?
Sphincter pupillae fibres form central ring round pupil
Dilator pupillae fibres radiate out like spokes
What is a non-physiological dilation of the iris called?
Mydriatic
What is a non-physiological constriction of the iris called?
Miotic
is the facial CNVII nerve sympathetic or parasympathetic?
Parasympathetic
What does the orbicularis oculi muscle do?
Closes the eye
What do the ciliary muscles do?
Adjust the focus on the lens allowing for focus
What happens when the ciliary muscles are relaxed?
The lens is stretched- good for distance vision
What happens when the ciliary muscles are contracted?
The lens thickens- good for near vision
What innervates the ciliary muscles?
Parasympathetic short ciliary nerve
Can the ciliary muscles be actively relaxed?
No, can be actively contract but must wait for parasympathetic innervation to stop before can dilate
What are the 6 reflex arcs it is important for us to know?
Maximal eyelid opening Pupil contraction/dilation Lens focusing Lacrimation Vestibulo-ocular reflex Blink reflex
When is maximal eyelid opening useful and what nerves control it?
Fight or flight
Somatic motor CNIII and sympathetic input
What is pupil contraction/dilation used for and what nerves control it?
Regulate the amount of light entering the eye
Parasympathetic short ciliary nerve and sympathetic long ciliary nerve
What is lens focusing used for and what nerve controls it?
Focusing on object at different distances
Parasympathetic short ciliary nerve
What is lacrimation used for and what nerve controls it?
Lubricate, clean and protect the eyes
Parasympathetic CNVII
What is the vestibulo-ocular reflex used for?
Eyes go opposite direction to head to keep them focused as head moves
What is a pinpoint pupil and what can it be a sign of?
Fixed constricted pupil.
Opiate use
What is a ‘Blown’ pupil and what can it be a sign of?
Fixed dilated pupil
CNIII damage
What is accommodation?
When eyes converge the lens thickens and pupils constrict.