Anatomy - Important Reflexes of the Orbital Region

Question 1

Sensory innervation of the face is as a result of which nerve?

Answer 1

Trigeminal nerve (CN V)

Question 2

Which regions of the face does the opthalmic nerve provide sensory innervation to?

Answer 2

1. Upper eyelid
2. Cornea
3. Conjunctiva
4. Skin of root/bridge/tip of nose

Question 3

Which regions of the face does the maxillary nerve nerve provide sensory innervation to?

Answer 3

1. Skin over lower eyelid
2. Skin over maxilla
3. Skin over ala of nose
4. Skin/mucosa of the upper lip

Question 4

Which regions of the face does the mandibular nerve provide sensory innervation to?

Answer 4

1. Skin over mandible*
2. Skin over TMJ

(*Excludes angle of mandible)

Question 5

What is the function of the blink/corneal reflex?

Answer 5

Protects eye

Question 6

Describe the path of a sensory action potential during the blink/corneal relfex

Answer 6

1. Cornea via CN V1 branches
2. Trigeminal ganglion
3. CN V
4. Pons

Question 7

During the blink/corneal relfex, which nerve carries the motor response?

Answer 7

CN VII

(to eyelid part of orbicularis oculi)

Question 8

Sympathetic axons can exit the spinal cord between whcih levels?

Answer 8

T1-L2

Question 9

Where can sympathetic signals pass?

Answer 9

1. Up/down sympathetic chain
2. Spinal nerves via anterior/posterior rami
3. Splanchnic nerves

Question 10

Where do presynpatic sympathetic axons synapse?

Answer 10

Superior cervical sympathetic ganglion

Question 11

How do post-synaptic sympathetic axons travel to organs in the head?

Answer 11

Via internal and external carotid arteries

Question 12

Parasympathetic axons leave the spinal cord via which nerves?

Answer 12

1. Cranial nerves III, VII, IX and X
2. Sacral spinal nerves

Question 13

Where does the oculomotor nerve connect with the CNS?

Answer 13

Junction between midline and pons

Question 14

Where does the oculomotor nerve enter the orbit?

Answer 14

Superior orbital fissure

(via cavernous sinus)

Question 15

What does the oculomotor nerve supply?

Answer 15

Somatic motor to:

1. Superior rectus (superior division)
2. Levator palpebrae superioris (superior division)
3. Medial rectus (inferior division)
4. Inferior rectus (inferior division)
5. Inferior oblique (inferior division)

It also innervates the ciliary ganglion (inferior division)

Question 16

What is the function of ciliary nerves?

Answer 16

Supply autonomic axons to control iris diameter and refractive shape of lens

Question 17

What types of innervation do long ciliary nerves provide?

Answer 17

1. Somatic sensory
2. Sympathetic (to dilator pupillae muscle)

Question 18

What types of innervation do short ciliary nerves provide?

Answer 18

1. Sympathetic
2. Parasympathetic (ciliary body and iris)

Question 19

What are the main autonomic reflexes of the eye?

Answer 19

1. Maximal eyelid elevation (fight or flight)
2. Pupillary dilation/constriction (light reflex)
3. Focussing lens far and near (accomodation reflex)
4. Tear production (lacrimation reflex)
5. Turns eyes in opposite direction to head movement to maintain gaze (vestibulo-ocular reflex)
6. Reflex bradycardia in response to tension on extraocular muscles or pressure on eye (oculocardiac reflex)

Question 20

The sympathetic system functions to focus on _____ objects

Answer 20

The sympathetic system functions to focus on far objects

Question 21

Which muscle is involved in widening the eyes during sympathetic stimulation?

Answer 21

Levator palpebrae superioris

(contains both skeletal and smooth muscle)

Question 22

Which branch of the autonomic nervous system will dilate the pupil?

Answer 22

Sympathetic

Question 23

Which types of drugs dilate the pupil?

Answer 23

Mydriatic drugs

Question 24

Which muscle will dilate the pupil?

Answer 24

Dilator pupillae muscle

Question 25

What is the term used to describe a non-physiologically constricted pupil?

Answer 25

Miotic

Question 26

Which muscle is responsible for constricting the pupil?

Answer 26

Sphincter pupillae muscle

Question 27

The pupillary light reflex involves a _-neurone chain

Answer 27

The pupillary light reflex involves a 4-neurone chain

Question 28

Describe the pathway of the neurones involved in the pupillary light reflex

Answer 28

1. Optic nerve
2. Synapse in midbrain
3. Pass (via 2nd neurone within midbrain) and synapse in Edinger-Westphal nucleus
4. CN III inferior division
5. Synpase in ciliary division
6. Coarse in short ciliary nerves to sphincter pupillae muscles

Question 29

When does the the ciliary muscle contract?

Answer 29

Under parasympathetic stimulation

(To focus on near vision)

Question 30

What are the three components of the accomodation reflex?

Answer 30

1. Bilateral pupillary constriction
2. Bilateral convergence of both eyes towards to midline
3. Bilateral relaxation of the lens

Question 31

How do tears provide a protective action against infection?

Answer 31

Conatin lysozyme which hydrolyses bacterial cell walls

Question 32

What are the afferent and efferent limbs associated with reflex tears?

Answer 32

1. CN V1 (afferent from cornea/conjunctiva)
2. CN VII (efferent)

Question 33

What are the 4 main symptoms of Horner’s syndrome?

Answer 33

1. Miosis (constricted pupil)
2. Ptosis (drooping of eyelid)
3. Anhydrosis (reduced sweating)
4. Increased warmth and redness

Question 34

Horner’s syndrome involves impaired __________ innervation to the head

Answer 34

Horner’s syndrome involves impaired sympathetic innervation to the head

Question 35

What may be causes of compression on the cervical aspect of the sympathetic trunk which may cause Horner’s syndrome?

Answer 35

1. Root of neck trauma
2. Carotid dissection
3. Internal jugular vein engorgement
4. Deep cervical node metastases
5. Pancoast tumour (lung apex)