L8 cranial nerves

Question 1

what are the cranial nerves?

Answer 1

• a set of **12 **paired nerves **arising directly **from the brain

Question 2

where do the cranial nerves emerge from?

Answer 2

• they emerge from the cranial cavity via the foramina or fissures in the cranium

Question 3

what are the 2 main origins of cranial nerves?

Answer 3

• The **cerebrum **( CN I & II)
• The brain stem (CN III- XII)

Question 4

where in the brain stem do the CN III- XII originate from?

Answer 4

* midbrain (pontine junction) - CN III - oculomotor
* **midbrain **- trochlear (IV) arises from posterior side of midbrain
* **Pons **- the trigeminal (3 branches) V
* **Medulla Oblongata **(IX - XI)

Question 5

what are the 12 cranial nerves?

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Answer 5

1. Olfactory
2. Optic
3. Oculomtor
4. Trochlear
5. Trigeminal
6. Abducent
7. Facial
8. Vestibulocochlear
9. Glossopharyngeal
10. Vagus
11. Accessory (spinal)
12. Hypoglossal nerve

Question 6

What is a motor (efferent) nerve?

Answer 6

carries information from the brain to the periphery

Question 7

what is a sensory (afferent) nerve?

Answer 7

• Carries information** from the periphery to the brain**

Question 8

Define general somatic afferent

Answer 8

converys general sensation from the skin

Question 9

Define** general visceral afferent **

Answer 9

converys general sensation from viscera

Question 10

Define special somatic afferent

Answer 10

conveys senses derived from ectoderm eg sight balance

Question 11

Define general somatic efferent

Answer 11

conveys motor innervation for skeletal muscles

Question 12

Define general visceral efferent

Answer 12

conveys motor innervation for smooth muscle, cardiac muscle and glands

Question 13

Describe the **olfactory nerve **

function

Answer 13

• CN I
• function : carries special sensory fibres for** sense of smell**
• speciailised nerve fibres located in olfactory mucosa
• these fibres** enter the cranial cavity** via the cribiform plate of ethmoid bone

Question 14

what can happen if there is severe head trauma / injury to the anterior cranial fossa (hint - to do with olfactory nerve)

Answer 14

• it can cause seperation of the olfactory bulb from the nerves
• can cause anosmia - loss of sense of smell

Question 15

what other cranial nerve also innervates the nasal mucosa and what is it’s function?

Answer 15

• CN V
• function - chemoreceptor - senses coldness

Question 16

Describe the optic nerve (CN II)

Answer 16

• special somatic afferent
• transmits all visual information - including colour & brightness perception

Question 17

what is the optic chiasm?

what is it formed from? function?

Answer 17

• formed by merging fibers from the optic nerve
• function - receives visual information from the optic nerve and **transmits this information to the optic tracts **

Question 18

what is the CNII surrounded by?

Answer 18

it is surrounded by extensions of the cranial meninges and subarachnoid space - which is filled with CSF

Question 19

what is the function of the visual pathway?

Answer 19

• the visual pathway transmits information interpreted from **visual light from the eyes to the visual cortex in the brain

Question 20

what is the** visual field**?

Answer 20

• the visual field is what is seen by a person with both eyes wide open and looking straight ahead

Question 21

Describe the visual pathway

the beginning - ie light - ocular bulb-retina-optic nerve - chiasm

Answer 21

• visual pathway begins with light entering the ocular bulb and being processed by the retina
• information then passed on from the retina by the optic nerve which travels to the optic chiasm

Question 22

Describe the visual pathway** from the optic chiasm**

Answer 22

• from the optic chiasm, the axons are now called the optic tract
• the axons then synapse at the** lateral geniculate nucleus**

Question 23

how do axons from the lateral geniculate nucleus reach the visual cortex of the brain?

Answer 23

they travel via the optic radiation

Question 24

where are inputs from the right and left visual field carried by?

Answer 24

• information from the left visual field carried in right optic tract
• information from right visual field carried in left optic tract

Question 25

where does **oculomotor nerve CNIII** supply?

Answer 25

* this nerve supplies **all extra ocular muscles** of the eye** EXCEPT** the** lateral rectus and superior oblique **

Question 26

what are the **functions of the oculomotor nerve**?

Answer 26

* eye movement * pupil constriction (through parasynpathetic innervation) * maintaining open eyelid NB - somatic efferent (motor) - as info goes from brain to periphery (eyes)

Question 27

Describe the **trochlear nerve** CN IV

Answer 27

* motor innervation of the** superior oblique muscle -** like a pulley system (trochlear = pulley) * unique - exits from posterior side of brain stem

Question 28

Describe the CN VI - abducens nerve

Answer 28

* provides motor innervation of the lateral rectus muscle * leaves brainstem at junction of pons and medulla

Question 29

Describe the **trigeminal nerve** - CN V

Answer 29

*** mixed nerve** - carries both sensory and motor information * primary sensory nerve for face and anterior scalp * motor nerve for muscles of mastication and other small muscles * trigeminal = triplet

Question 30

what **3 terminal nerves** does the sensory route of the trigeminal nerve CN V divide into?

Answer 30

* Ophthalmic nerve * maxillary nerve * mandibular nerve

Question 31

Describe the **facial nerve **

Answer 31

* CN VII * supplies motor innervation to the muscles of facial expression * supplies parasympathetic innervation to the salivary glands, lacrimal glands, and mucous glands

Question 32

Describe the **vestibulocochlear nerve** CN VIII

Answer 32

* carries special sensory fibres for hearing and balance * can be divided into 2 components - cochlear part (transmits auditory info to brain) and vestibular part (transmits info about balance to the brain)

Question 33

Describe the glossopharyngeal nerve

Answer 33

* transmits sensory info from the carotid body & sinus, posterior third of tongue, oropharynx etc * carries special sensory fibres for taste for posterior 2/3 of tongue

Question 34

what gland does the glossopharyngeal nerve innervate?

Answer 34

the parotid salivary gland

Question 35

what does the **glossopharyngeal nerve** **arise from** and where does it** exit the cranial cavity**?

Answer 35

* arises from the medulla oblongata * exits the cranial cavity via the jugular foramen

Question 36

Describe the **vagus nerve** CN X | vagus = wondering in latin

Answer 36

* most **widely distributed CN** *** mixed **nerve * provides sensory info to the **heart, lungs trachea, bronchi, pharynx ** and more... * also supplies **parasympathetic info** to **smooth muscle and glands** in the body

Question 37

where does the vagus nerve arise from and where does it exit the cranial cavity?

Answer 37

* it arises from the medulla oblongata * exits via the jugular foramen

Question 38

What 2 muscles does the spinal accessory nerve innervate?

Answer 38

* Trapeqius * SCM muscle in neck

Question 39

where do the fibres of the spinal accessory nerve originate from?

Answer 39

the spinal cord

Question 40

Describe the path of the accessory nerve

Answer 40

* it originates from the spinal cord and ascends into the cranial cavity via the foramen magnum * it then exits the cranial cavity via the jugular foramen where it innervates the 2 muscles

Question 41

is the hypoglossal a motor or sensory nerve?

Answer 41

motor

Question 42

Describe the hypoglossal nerve (CN XII)

Answer 42

* motor nerve * motor innervation to intrinsic and extrinsic muscles of tongue except for palatoglossus muscle

Question 43

which cranial nerve innervates the palatoglossus muscle ?

Answer 43

vagus nerve

Question 44

where does the hypoglossal nerve originate from and where does it exit the cranial cavity?

Answer 44

* it arises from the anterior surface of the medulla oblongata * it exits the cranial cavity via he hypoglossal canal

Question 45

which of the cranial nerves are** mixed** nerves?

Answer 45

* trigeminal nerve * facial nerve * glossopharyngeal nerve * vagus nerve