formative

Question 1

Cranial nerve 1 facts

Answer 1

• has only afferent component
• if damaged, will result in anosmia on the ipsilateral side
• enters the cranial cavity via small holes in the cribriform plate of the ethmoid bone
• is commonly damaged in fractures to the anterior cranial fossa

Question 2

Cranial nerve 2

Answer 2

• can be tested in the unconscious patient by observing pupillary constriction in response to light (pupillary reflex afferent limb via retino-hypothalamic tract)
• enters the skull via the optic canal
• first joins the opposite cranial nerve II within the optic chiasm
• Its fibres are closely related to the lateral geniculate body
• A lesion affecting the left optic nerve will result in total blindness in the left eye

Question 3

CN 3/4/5 key facts

Answer 3

• all take a course which runs through the cavernous sinus
• CN III carries parasympathetic fibres (from Edinger-Westphal nucleus in tegmentum to the ciliary muscles & sphincter pupillary muscle
• Damage of CN III will lead to ptosis of the eyelid on the same side
• Damage to the CN VI will result in the inability to abduct the affected eye
• A person with CN IV damage will complain of double vision as they look down

Question 4

Roles of the CNIII in eyes

Answer 4

• Eye movement
• Pupil constriction
• Maintains open eyelid (levator palpebrae superioris)

Question 5

Role of CNVI and CNIV in eyes

Answer 5

• CNVI: lateral rectus (abducts)

- CNIV: superior oblique (depress + adducts)

Question 6

Facts about CNV

Answer 6

• is sensory and motor
• passes through the superior orbital fissure (ophth)/rotundum (max)/ovale (man)
• Damage will result in the loss of the corneal reflex on the affected side

Question 7

Facts about CN VII

Answer 7

• Runs a course which is closely related to the middle ear
• Exits skull via the internal auditory meatus
• Has its nucleus in the tegmentum (not tectum) of the pons

Question 8

Branches of CNVII

Answer 8

1. ) Branchial motor
2. ) Visceral motor
3. ) Special sensory
4. ) General sensory

Question 9

Role of branchial motor

Answer 9

Supplies muscles of facial expression/posterior belly of digastric muscle/stylohyoid/stapedius

Question 10

Role of visceral motor

Answer 10

Parasympathetic innervation of the lacrimal/submandibular/sublingual glands as well as mucous membranes of nasopharynx/hard + soft palate

Question 11

Role of special sensory

Answer 11

Taste sensation from the anterior 2/3 of tongue/hard and soft palate

Question 12

Role of general sensory

Answer 12

General sensation from the skin of the concha of the auricle and from a small area behind the ear

Question 13

Five major facial branches (In parotid gland) from top to bottom

Answer 13

1. ) Temporal
2. ) Zygomatic
3. ) Buccal
4. ) Marginal mandibular
5. ) Cervical
   - Ten Zebras Buggered My Cat

Question 14

Key facts about CN VIII

Answer 14

• concerned with hearing and balance
• exits the cranial cavity via the internal auditory meatus
• when diseased it may cause rapid eye movements: nystagmus
• with complete damage, when a tuning fork is placed in the middle of the forehead, the sound is heard best on the opposite side as the damage
• a tumour of the nerve may cause paralysis of the muscles of facial expression

Question 15

Key facts about CNIX

Answer 15

• sensory and motor
• carries parasympathetic fibres to the parotid glands
• Supplies muscles of the hypoglossal and pharynx
• Leaves the cranium through the jugular foramen

Question 16

Key facts about cranial nerve X

Answer 16

• Made up of both sensory and motor components
• Carries parasympathetic fibres to the heart/lungs/bowel
  Leaves brain at the level of the medulla
• Has a branch which supplies motor control to all pharyngeal muscle EXCEPT stylopharyngeus
• Causes decreased heart rate and blood pressure when stimulated

Question 17

Facts about the cranial nerve XI

Answer 17

• carries purely motor fibres
• has two roots: cranial and spinal
• runs in close proximity to the internal jugular vein
• exits the cranial cavity via the internal jugular foramen alongside the spinal cord
• Injury to the nerve causes paralysis of the sternocleidomastoid and superior trapezius muscles on the same side of the lesion

Question 18

Key facts about CN XII

Answer 18

• Contains motor component for tongue muscles
• supplies extrinsic and intrinsic muscles of the tongue
• leaves the cranial cavity via the hypoglossal canal
• its nerve cell bodies are located within the medulla
• damage to the nerve will cause paralysis of the ipsilateral half of the tongue

Question 19

Key facts about the spinothalamic tract

Answer 19

• Is
• Conveys nociceptive information to the contralateral thalamus
• Is found in the anterolateral white matter of the spinal cord
• conveys nociceptive information contralaterally up the spinal cord (crosses over as ascends over 2-3 vertebral segments)
• after they desscate the fibres of the spinothalamic tract synapse in the thalamus first

Question 20

Key facts about brown-sequard syndrome

Answer 20

• get a right-sided hemiplegia
• lower motor neuron paralysis at the level of C7 on the ipsilateral side
• loss of two point discrimination appreciation below the level of the lesion on the right
• loss of pain + temp appreciation at all segments below the level of the lesion on the left
• loss of proprioceptive information conveyed to the spinocerebellar tract

Question 21

Key facts about the middle ear

Answer 21

• middle ear is fillef with air
• conductive deafness is a reduction in the mechaninical transmission of sound waves to the round window
• The chain of three ossicles have synovial joints between them
• the stiffness of the ossicular chain can be modified by two muscles of the middle ear