Lecture 6: Brainstem and Cranial nerves (II)

Question 1

Visual pathway flow

Answer 1

Starts at the retina and the ret4inal ganglion cells go back and form the optic nerve and then some of the axons cross over and some don’t, where the cross over occurs is called the optic chiasma, and then they keep going back as the optic tract and innervate various structures like the superior colliculus and the lateral geniculate nucleus of the thalamus, then the axons from the lateral geniculate nucleus go back to the visual cortex which is the overall pathway, also have the superior colliculus pathway which shows how these axons go to various motor nuclei

Question 2

Damage at the optic chiasm (cross over) causes …

Answer 2

Bitemporal hemianopsia - peripheral vison loss, nasal retina on each side damaged, the nasal retinas see the temporal visual fields, pituitary tumour or hypothalamus tumour can put pressure on the optic chiasm and cause this

Question 3

Optic nerve

Answer 3

axons of the retinal ganglion cells

Question 4

Optic chiasm

Answer 4

fibers originated from nasal retina cross over to the opposite side

Question 5

Optic tract

Answer 5

contains crossed axons from nasal retina & uncrossed axons from temporal retina

Question 6

Lateral geniculate nucleus of the thalamus

Answer 6

processes & relays visual information to visual cortex

Question 7

Superior colliculus

Answer 7

visual reflex centres controlling the extrinsic eye muscles

Question 8

Primary visual cortex (occipital lobe)

Answer 8

• processes basic visual information (contrast information & object orientation)
• conscious perception of visual images

Question 9

Visual association ateas (occipital lobe)

Answer 9

processes visual information concerned with shape, colour & movement

next to primary visual cortex

Question 10

Complex visual processing - ventral parts of temporal lobe

Answer 10

identify objects in the visual field (what)

ventral stream

Question 11

Complex visual processing - parietal cortex

Answer 11

assess the spatial location of objects (where)

dorsal stream

Question 12

Complex visual processing - frontal cortex

Answer 12

uses visual information to guide movement

Question 13

Oculomotor nerves location

Answer 13

Cranial nerve III

Axons extend from ventral midbrain, goes forward & passes through the superior orbital fissure to the eye

Question 14

Oculomotor nerves composition overall

Answer 14

Mixed nerves - chiefly motor

Somatic motor axons
Parasympathetic (autonomic) motor axons
Sensory (proprioceptor) afferents

Question 15

Oculomotor nerves composition - Somatic motor axons

Answer 15

to four of the six extrinsic (muscles on the outside of the eye) eye muscles (inferior oblique muscle and superior, inferior and medial rectus muscles)

• move eyeball
• to levator palpebrae superior muscle - raising upper eyelid

Question 16

Oculomotor nerves composition -Parasympathetic (autonomic) motor axons

Answer 16

• to constrictor muscles of iris (coloured part of the eye)- causing pupil to constrict
• to ciliary muscle –controlling shape of lens for visual focusing

Question 17

Oculomotor nerves composition - Sensory (proprioceptor) afferents

Answer 17

information from the PNS to CS - information communicated from the eye muscles to the midbrain

Question 18

Oculomotor nerves known as the …

Answer 18

eye mover

Provide most of the movement of each eye
Also - opening of eyelid, constriction of pupil, focusing

Question 19

Damage to oculomotor nerves

Answer 19

Damage causes drooping upper eyelid, dilated pupil, double vision, difficulty focusing & inability to move eye in certain directions

muscles its innervating are affected

Question 20

Trochlear nerves location

Answer 20

Cranial nerve IV

Axons emerge from dorsal midbrain, course ventrally around midbrain, pass through the superior orbital fissure to the eye
**Only cranial nerve emerging from dorsal brainstem

Question 21

What cranial nerve is the only one to emerge from the dorsal brainstem?

Answer 21

Trochlear nerve (4th cranial nerve)

Question 22

Trochlear nerve composisotn

Answer 22

primarily motor (chiefly motor)

Supply somatic motor axons to (& carry proprioceptor axons from) the superior oblique muscle (which rotates the eye downward & laterally) [SO4 - superior oblique muscle innervated by the 4th cranial nerve]

• This muscle has a tendon that hooks around a pulley called a trochlea
• Provide eye movement

Question 23

Trochlear nerve damage

Answer 23

Damage causes double vision & inability to rotate eye inferolaterally

double vision because not all muscles are working together to get clear vision

Question 24

Trigeminal nerve location

Answer 24

cranial nerve V

3 major branches - ophthalmic division (VI), maxillary division (V2) and mandibular division (V3), one on each side

Axons extend from face to pons (S - sensory = large component) & pons to muscles (M - motor = small component)

Cell bodies of sensory neurons are located in large
trigeminal ganglion

Question 25

Divisons of the trigeminal nerve

Answer 25

3 major branches - ophthalmic division (VI), maxillary division (V2) and mandibular division (V3)

Question 26

Opthalamic division (V1) of trigeminal nerve

Answer 26

Axons run from face to pons via superior orbital fissure Convey sensory impulses from skin of anterior scalp, upper eyelid & nose, & from nasal cavity mucosa, cornea & lacrimal (tear) gland - all of the sensory information from these structures is going to the pons via the superior orbital fissure

Question 27

Maxillary division (V2) of trigeminal nerve

Answer 27

Axons run from face to pons via foramen rotundum Convey sensory impulses from nasal cavity mucosa, palate, upper teeth, skin of cheek and upper lip anaesthetised when getting upper teeth dental work

Question 28

Mandibular division (V3) of trigeminal nerve

Answer 28

Axons pass through skull via foramen ovale Convey sensory (pain, temp (hot and cold) but not taste from the tongue) impulses from anterior tongue (except taste buds), lower teeth, skin of chin, & temporal region of scalp V3 has a motor branch - Supply motor axons to (carry proprioceptor axons from) muscles of mastication (chewing muscles)

Question 29

Trigeminal nerve composition

Answer 29

Mixed nerves - mainly sensory * Largest cranial nerves * Main sensory nerve from face (transmitting afferent impulses from touch, temperature & pain receptors) * Supply motor axons to muscles of mastication (V3) Part of each nerve can be anaesthetised during dental procedures

Question 30

Trigeminal nerve damage

Answer 30

Damage produces loss of sensation & impaired | chewing

Question 31

Tic Douloureux (trigeminal neuralgia)

Answer 31

* inflammation of trigeminal nerve (pressure on nerve root) * excruciating pain * provoked by a sensory stimulus in area of supply (touching forehead for example) * analgesics - partially effective * Nerve cut in severe case to relieve pain (but causing sensation loss)

Question 32

Abducens nerve location

Answer 32

Cranial nerve VI Axons leave inferior pons & pass through superior orbital fissure to eye (lateral rectus muscle)

Question 33

Abducens nerve function

Answer 33

Provide eye movement (abducts the eyeball - i.e. moves it from the midline )

Question 34

Abducens nerve damage

Answer 34

Damage results in inability to rotate eye laterally & at rest eye rotates medially (lazy eye)

Question 35

Facial nerves location

Answer 35

Cranial nerve VII Axons emerge from pons, enter temporal bone via internal auditory meatus and run within bone (bony canal) (through inner ear cavity) before emerging through stylomastoid foramen; course to lateral aspect of face

Question 36

Branches of the facial nerves from most superior to inferior

Answer 36

``` temporal zygomatic buccal (cheek) mandibular (mandible/jaw) cervical (neck) ```

Question 37

Mandibular branches for both

Answer 37

trigeminal and facial nerves (do not get confused between the two)

Question 38

Facial nerves composition

Answer 38

Mixed nerves Major motor axons of face * Supply motor axons to (convey proprioceptor impulses from) skeletal muscles of face (muscles of facial expression), except for chewing muscles served by cranial nerve V (trigeminal supplies this instead) * Transmit parasympathetic (autonomic) motor impulses to lacrimal (tear) glands, nasal & salivary glands * Convey sensory impulses from taste buds of anterior 2/3 of tongue - taste from anterior part of tongue through this nerve

Question 39

Facial nerves damage

Answer 39

Damage produces sagging facial muscles & disturbed sense of taste (missing sweet, salty & umami)

Question 40

Bells Palsy

Answer 40

facial nerve damage usually unilateral not bilateral characterised by paralysis of facial muscles (affected side) & partial loss of taste sensation (because the facial nerve is not responsible for all of the taste information) * viral infection causing inflammation of facial nerve * symptoms: lower eyelid droops, corner of mouth sags, tears drip continuously, eye cannot be completely closed, paralysed face is 'pulled'(to the other side). Treatment: steroids, rest

Question 41

Vestibulocochlear nerve location

Answer 41

Cranial nerve 8 Axons arising from hearing & equilibrium apparatus (which is the cochlea and the semicircular canals) within inner ear of temporal bone, passing through internal acoustic meatus to enter brainstem at the pons- medulla border more laterally arising than the facial nerves on the pons - medulla junction/inferior part of pons

Question 42

Vestibulocochlear nerve composition

Answer 42

Purely sensory Provide hearing (cochlea nerves) and sense of balance (vestibular nerves)

Question 43

Vestibulocochlear nerve damage

Answer 43

Damage produces deafness, dizziness, | nausea, loss of balance and nystagmus (rapid involuntary eye movements)

Question 44

Auditory pathway

Answer 44

Pathway from the sensory receptors to the brain …. Stimulation of an inner hair cell in the cochlea which generates an action potential which runs down the vestibulocochlear nerve and then it follows a pathway innervating various collections of nerves (don’t need to know names of the pathway just appreciate there is one), so the action potential runs in the vestibulocochlear nerve to the cochlear nucleus of that nerve then in turn these neurons innervate the superior olivary nucleus which then goes and innervates the inferior colliculus which we know is a part of the auditory pathway and it crosses to the other side here and then from the inferior colliculus information is conducted up to the thalamus but now to the medial geniculate body and from here it goes up to the primary auditory cortex and another name for this is the transverse temporal gurus

Question 45

Glossopharyngeal nerves location

Answer 45

Cranial nerve 9 Axons emerge from medulla & leave skull through jugular foramen - it is the first nerve that emerges from the medulla

Question 46

Glossopharyngeal nerves composition

Answer 46

Mixed nerves with sensory and motor component

Question 47

Glossopharyngeal nerves function

Answer 47

• Supply motor axons to (carry proprioceptor fibers from) a pharyngeal muscle - stylopharyngeus (skeletal muscle) • Provide parasympathetic motor axons to parotid salivary gland (smooth muscle) * Sensory axons conduct taste & general sensory impulses from pharynx & posterior 1/3 of tongue * Conducting sensory impulses from chemoreceptors (detect oxygen levels and determine whether you are hypoxic or not) in the carotid body & pressure receptors of carotid sinus Provide control over swallowing, salivation, gagging, sensations from posterior 1/3 of tongue, control of blood pressure & respiration

Question 48

Glosspharyneal nerve damage

Answer 48

Damage results in loss of bitter & sour taste, and impaired swallowing

Question 49

Vagus nerve location

Answer 49

Cranial nerve 10 Axons emerge from medulla, pass through skull via jugular foramen, descend through neck region into thorax & abdomen

Question 50

Vagus nerve composition

Answer 50

mixed nerve motor Supply motor axons to (carry proprioceptor fibers from) skeletal muscles of pharynx & larynx - Parasympathetic motor fibers supply heart, lungs & abdominal viscera sensory axons conducting sensory impulses from thoracic & abdominal viscera - transmitting sensory impulses from chemoreceptors in the carotid & aortic bodies, & pressure receptors of carotid sinus - conducting sensory impulses from taste buds of posterior tongue & pharynx

Question 51

Vagus nerve is the only cranial nerve to do what

Answer 51

The only cranial nerve extending beyond the head & | neck to the thorax & abdomen

Question 52

Majority of vagus nerve motor axons are

Answer 52

Majority of motor axons are parasympathetic

Question 53

Overall function of vagus nerve

Answer 53

Provide swallowing & speech; | • regulate activities of major viscera

Question 54

Vagus nerve damage

Answer 54

Damage causes hoarseness or loss of voice, impaired swallowing & digestive system mobility Fatal if both are cut - critical for heart and lungs to maintain function

Question 55

Accessory nerves location

Answer 55

Cranial nerve 11 Accessory to vagus nerve Cranial root (lateral medulla) - through jugular foramen - joins vagus nerve (X) Spinal root (spinal C1-C5) - through foramen magnum - to neck muscles

Question 56

Cranial root of accessory nerves

Answer 56

Cranial root joins with axons of vagus nerve (X) to supply motor axons to larynx, pharynx & soft palate

Question 57

Accessory nerve composition

Answer 57

mixed nerves - primarily motor

Question 58

Damage to cranial root of accessory nerves

Answer 58

Damage causes hoarseness or loss of voice & impaired swallowing

Question 59

Spinal root of accessory nerves

Answer 59

Spinal root supplies motor axons to (conveys proprioceptor impulses from) trapezius & sternocleidomastoid muscles, therefore provides head, neck & shoulder movement

Question 60

Damage to spinal root of accessory nerves

Answer 60

Damage causes impaired head, neck & shoulder movement. eg. unable to shrug on one side if unilateral injury

Question 61

Hypoglossal nerves location

Answer 61

(below tongue) Cranial nerve 12 * Axons arise by a series of roots from medulla, exit from skull via hypoglossal canal to tongue * Axons emerge between the pyramid & olive

Question 62

Hypoglossal nerves composition

Answer 62

primarily motor Supply somatic motor axons to (convey proprioceptor impulses from) intrinsic & extrinsic muscles of tongue Provide tongue movements of speech, food manipulation & swallowing

Question 63

Damage to hypoglosaal nerves

Answer 63

Damage causes difficulties in speech & swallowing Both sides - inability to protrude tongue One side - tongue deviates (leans) towards injured side & results in ipsilateral atrophy eventually

Question 64

Olfactory - sensory function? motor function? parasympathetic fibres?

Answer 64

yes (smell) No No

Question 65

Optic - sensory function? motor function? parasympathetic fibres?

Answer 65

yes (vision) No No

Question 66

Oculomotor - sensory function? motor function? parasympathetic fibres?

Answer 66

No Yes Yes

Question 67

Trochlear - sensory function? motor function? parasympathetic fibres?

Answer 67

No Yes No

Question 68

Trigeminal - sensory function? motor function? parasympathetic fibres?

Answer 68

Yes (general sensation) Yes No

Question 69

Abducens - sensory function? motor function? parasympathetic fibres?

Answer 69

No Yes No

Question 70

Facial - sensory function? motor function? parasympathetic fibres?

Answer 70

Yes (taste) Yes Yes

Question 71

Vestibulocochlear - sensory function? motor function? parasympathetic fibres?

Answer 71

Yes (hearing and balance) No No

Question 72

Glossopharyngeal - sensory function? motor function? parasympathetic fibres?

Answer 72

Yes (taste) Yes Yes

Question 73

Vagus - sensory function? motor function? parasympathetic fibres?

Answer 73

yes (taste) Yes Yes

Question 74

Accessory - sensory function? motor function? parasympathetic fibres?

Answer 74

No yes No

Question 75

Hypoglossal - sensory function? motor function? parasympathetic fibres?

Answer 75

No yes no

Question 76

Reticular formation

Answer 76

DO NOT FORGET TO DO THE LAST FEW SLIDES OF THIS LECTURE !!!!