Cranial nerves 1 Flashcards
1
Q
What are cranial nerves?
A
12 pairs which Link the face, head and neck to the brain
2
Q
How many spinal nerves are there?
A
31 pairs which connect to the rest of the body to the spinal cord.
3
Q
What are the 12 cranial nerves names?
A
|- Olfactory nerve || -Optic nerve |||- Oculomotor nerve |V - Trochlear nerve V - Trigeminal nerve V| -Abducent nerve VV||- Facial nerve V|||- Vestibulo- cochlear nerve |X- Glossopharyngeal nerve X - Vagus nerve X|- Accessory nerve X||- Hypoglossal nerve
4
Q
What nerves are connected to the cerebrum?
A
| || - Optic nerve
- Olfactory nerve
5
Q
What are the other 10 nerves connected to?
A
Brainstem
6
Q
What are the olfactory bulbs?
A
collection of neurones that sit underneath the first part of your brain received direct input from receptors up your nose.
-The chemoreceptors attaché themselves to chemical receptors up your nose which are attached to axons which send info to the olfactory bulb
7
Q
What is the optic nerve?
A
-begin with a bunch of neurones infront of the eye especially in retina.
8
Q
What are the 3 main divisions of the brainstem?
A
- Midbrain
- Pons- bridge between midbrain and medulla
- Medulla
9
Q
What is anopcia?
A
Damage to optic nerve
10
Q
What do the prefixes a- and an- mean?
A
can’t (nerve damage)
11
Q
What are each cranial nerve : important features?
A
- Number and name
- Composition- sensory, voluntary motor , autonomic
- Region/tissues supplied: sensory or motor
- Foramen, fissure or canal nerve passes through
- Function and simple tests
- Effects of nerve damage/lesions
12
Q
What are all involuntary autonomic systems?
A
- Parasympathetic : for resting and digesting
- Increase smooth muscle contraction and glandular secretion
13
Q
What are sensory nerves?
A
- Have receptors which are connected to an axon which sends sensory information to neurone inside CNS and the synapse activate excitatory neurones in the CNS
14
Q
What are the neurones that convey sensory info from these tissue to neurone in the CNS?
A
- Ganglion cells- primary sensory neurones
e. g cells in retina which send info to your brain down optic nerve which are called retinal ganglion cells
15
Q
What are the somatic motor neurones?
A
Inside CNS - that have axons which come out and send signals to directly innovate via excitatory synapses skeletal or voluntary muscles.
16
Q
What are the autonomic motor neurones?
A
-Inside CNS- send axons out into the peripheral system but don’t directly innervate target tissue such as a smooth muscle or gland, they stop off and make synaptic contact with neurones in peripheral NS (autonomic ganglion cells)- which make synaptic contact with the target tissues they are innervating.
17
Q
What are the cranial nerves composition of somatic and special senses?
A
- Smell (1 olfactory); vision (2 optic)
- Somatic (5 trigeminal and 9 glossopharngeal)
- Taste ( 7 facial and 9 glossopharyngeal)
- Vestibular and hiring/auditory (8 vestibular cochlear)
18
Q
What are the cranial composition of motor: voluntary movements of skeletal muscles?
A
-Eyes (3, Oculomotor; 4, Trochlear; 6, Abducent)
-Chewing/Mastication (5, Trigeminal): Facial expression (7, Facial)
-Swallowing/Vocal apparatus (9, Glosspharyngeal, 10 Vagus)
Neck (11, Accessory): Tongue (12, Hypoglossal)
19
Q
What are the cranial nerves composition of motor: autonomic/parasympathetic to smooth muscle and glands?
A
- Iris sphincter + ciliary (pupil constriction + accommodation = 3 Oculomotor)
- Lacrimal gland (for aqueous tear production = 7 Facial)
- Salivary glands (for digesting = 7 Facial & 9 Glosspharyngeal)
- Heart, lungs, stomach glands etc (for resting & digesting = 10 Vagus)
20
Q
How do cranial nerves pass?
A
Each cranial nerve enters (sensory neurones) or exits (motor, autonomic neurones ) the skull through a specific hole (aka: canal, foramen, fissure). -Several small; some large (foramen magnum)
21
Q
What is are the 3 pairs of spaces the skull is made from?
A
- 2 Anteroir fossa
- 2 Middle fossa
- 2 Posterior fossa
22
Q
What is a cribriform plate?
A
perforated plate of bone- tiny holes
- Is part of a bone which sits behind your nose.
- Olfactory bulb sit above these tiny holes
23
Q
What do these holes in the skull do (tiny holes)?
A
- These holes are designed are designed to take axons coming from your nose directly up to target neurones in your skull.
24
Q
What is the foramen magnum?
A
- Big whole in skull - brainstem connects to spinal cord and big arteries come in to your skull through this too.
25
What is the | - Olfactory nerve?
- Purely sensory nerve
- Sense of smell
- Olfactory receptors in the nasal mucosa
26
What is the foramen of the |- olfactory nerve?
-Those olfactory receptors are attached to axons (olfactory filaments) which pass through cribriform plate (holes) in the ethmoid bone
27
What is the destination of the | - olfactory nerves?
-neurones of the olfactory bulbs are underneath the brain and then activate those neurones and those neurones send axons of their own via olfactory tracts to higher brain centres for conscious smell perception.
28
How can |- olfactory nerves be damaged?
- can be ruptured by head injury- (rupture olfactory filaments which means there is no longer a connection in receptors of nose to olfactory bulbs )
- causing loss of sense of smell
29
What is anosmia?
loss of sense of smell
30
What is the process of |- Olfactory nerve ( and tract )?
there is mucous membrane up your nose- have receptors for various stimuli that you may inhale up your nose which are attached to olfactory filaments
-These travel up the tiny holes in the cribriform plate- to make excitatory synaptic contact with neurones in then olfactory bulbs which send axons down olfactory tract to higher centres in the brain.
31
What is the 2nd cranial nerve ?
Optic nerve - ||
32
What is the optic nerve ||?
- Purely sensory nerve
- Concerned with a special sense of vision/sight.
- Start with a group of cells in retina- RETINAL Ganglion cell - their axons leaves the baxck of your eye to form the optic nerve
33
What is the foramen of the optic nerve ||?
-axons pass through a hole at baxck of your orbit which is called optic canal
34
What happens after the Forman of the optic nerve ||?
- the nerve continues through the brain as optic chiasm, then the optic tract
35
What is the destination of the optic nerve ||?
- is called the Lateral geniculate nucleus ( LGN) of the thalamus (synapse)- in this nucleus is where the retinal ganglion cells axons from excitatory synapse with LGN neurones then pass to the area of the brain responsible for conscious visual perception.
36
What is the LGN?
A particular nucleus ( group of neurones in the cerebrum)
37
What happens in the optic chiasm region?
-when 2 optic nerves form left and right come together in the region of the optic chiams
38
What happens in the region of the optic chiasm in the optic nerve ||?
nasal retina axons cross the midline but temporal axons remain uncrossed.
39
What are. the 3 orbital cavities?
1 : Optic canal- circular hole - where optic nerve leaves the orbit and goes to brain
In: Opthalmic artery - massive artery comes in the hole.
2: Superior orbital fissure - slit hole
3: Inferior orbital fissure- slit
40
What is the ophthalmic artery ?
pair of artery that supplies everything inside your orbital cavity
41
What is a left and right HEMI fields?
- hemi- half of visual field
42
What is the left half of visual field (left half of left eye and right eye)?
right side of brain
43
What is the right half of visual field?
left side of brain
44
What is the left half of your left eye?
temporal half-
45
What happens when the retinal ganglion axons that are recieving information from the right half of visual field in left temporal retina?
- They send axons down optic nerve, remain crossed ( due to being temporal) as they go into the chiasms and tract and end up on the left side of the brain
46
What happens with the axons from the nasal retina of your right eye (left half of visual field)?
- they send axons down the nerve and when get to chiasm they cross the midline and end up on left side of brain
- as a consequence off that right half of visual field
47
What does the left temporal retina and right nasal retina then end up being represnett?
At the left side of the brain (from the right half of the visual field)
48
What happens with the right temporal retina (from left side of brain) and left nasal retina?
(left half of visual brain) go to right side of brain
49
What is the significance of the left side and right side controlling opposite sides?
- the axons damage at different optic pathway locations cause different visual field loss.
50
What is a type of visual field loss?
- Bi temporal hemi anopsia- cased by tumour in your pituitary gland
- Pituitary Gland sits directly below the optic chiasm
- Tumours in the gland (adenomas- benign and gross slowly) tend to grow upwards (red & yellow arrows)
- Surrounded by bones hence grows up
- It hits the optic chiasm.
- Cutting the Nasal axons from both eyes as they cross in the chiasm.( splits optic chiasm right at the midline)
51
What is the damage caused by the bi temporal hemi anopsia?
Leading to bi-lateral loss of the
Temporal half-fields = the black regions in these Visual Field plots of the Left & Right eyes
-Can not see the temporal half of visual field in left and right eye.
(NB: temporal axons are spared, so these regions of Visual Field can still be seen as the Nasal hemi-fields in each eye)
bi- both sides
temporal - vision missing
hemi- half the field missing
anopsia- can't see it
52
What is the function of the ||| Oculomotor, |V Trochlear. and V| Abducent nerve? (nerves 3, 4 and 6)
have voluntary motor components that innervate extra ocular muscles
- Eye movements are controlled by 6 extraocular muscles (EOMs) innervated by these nerves
- originate from Motor nuclei in midbrain (III,IV) & pons (VI)
53
What is the foramen of the ||| Oculomotor, |V Trochlear. and V| Abducent nerve?
Superior Orbital Fissure, back of orbit- enter orbit through slit - heading for different extra ocular muscle
54
What does the oculomotor nerve supply?
buggest nerve- reguires 4 EOMs: medial rectus, inferior rectus & superior rectus & inferior oblique
55
What does the trochlear supplies ?
one muscle - the super oblique
56
What does the abducent supply?
only 1- lacteal rectus
57
What does the 3rd oculotomor nerve also supply ?
also sends input to voluntary muscle in upper eyelid and has a Parasympathetic component (more later)
58
What enters the superior orbital fissure?
the 3 nerves - oculomotor , trochlear and abducent
59
What are the EOMs attached to?
sclera
60
What is the medial rectus muscle in right eye?
- muscle on side of eyeball, next to nose, close to midline, medial rectus
61
What happens when medial rectus contracts in right eye?
medial rectus contracts the eye moves towards the nose
| -called adduction
62
What is the lateral rectus?
on other side, sits on lateral side of eyeball
63
What happens when lateral rectus contracts?
eye moves outwards away from nose called abduction
64
What are the lateral and medial rectus?
move eyes in horizontal direction
| -pair of antagonistic muscles
65
What are the 2 muscles the move the eye vertically (up and down)?
- Superior rectus - up
| - Inferior rectus - down
66
What are the 2 oblique muscles ?
Superior oblique
inferior oblique
-Twist eyeball - toritional direction
67
What are the EOMS that are innervated by the oculomotor nerve?
```
SR
IR
MR
LR
IO
```
68
What are the EOMS that are innervated by the trochlear?
SO
69
What are the EOMS that are innervated by the abducent?
LR
70
What can represent this?
LR6SO4
(lr6- purple- 6th abducent nerve
so4- 4th trochlear nerve)
Rest by the oculomotor nerve.
71
What are the consequences if you damage oculomotor, trochlear and abducent?
- Damage to these nerves results in ‘ocular palsy’- weakness of eye movement
- The affected EOM(s) are paralysed/weak
- Opposing muscles still work & ‘over-act’
- So the eye adopts an abnormal position in the orbit (a.k.a; strabismus or tropia) & the Px experiences double vision (diplopia)
- The direction of the strabismus/tropia depends on which particular nerve/muscles are affected
72
What are the simple tests of EOM and nerve function 'ocular motility'?
- to test the integrity of the nerves and the muscles they innervate
- You Examine the position of each eye in primary (straight ahead) gaze (1)
- Examine whether the Px is able to move their eyes horizontally, obliquely & vertically into different positions (2-9)
73
How does ocular palsy occur if damage to the oculomotor Nerve (|||)? (referring to example in powerpoint)
-nerve supply to her medial rectus muscle on right side is gone so can't move eye towards nose but supply to lateral rectus is working which could move her eye outwards.
-Exotropia- when eye pulled outside
out (exo-tropia); MR paralyzed, LR over-acts
drooping upper eyelid (ptosis)
dilated pupil
74
What is the levator palpebrae ?
in upper eyelid
| levator palpebrae superioris a skeletal muscle which lifts the upper eyelid
75
What are the internal eye muscles?
internal eye muscles = iris sphincter (pupil constriction) & ciliary (accommodation ); parasympathetic via the Ciliary Ganglion
76
How does ocular palsy happen when damage is to the trochlear nerve? in powerpoint example
Affected Right eye:
- SO paralyzed
other 5 EOMs over-act
-Usually the SO muscle usually pulls eye downward and outward direction- so if it doesn't work/weak the eye then looks up and in .
-up (hyper-tropia) & in (eso-tropia);
77
How does ocular palsy happen when damage is to the abducent nerve? in powerpoint example
-Nerve which innervates LR muscle- side of right eye can't pull out
-Medial rectus still works hence eye pulled toward nose
-in (eso-tropia); LR paralyzed
other 5 EOMs, especially MR, over-act
78
What would happen if the right optic nerve was crushed?
blindness in right eye
