cranial nerves Flashcards
motor neurones
motor neurons emerge from the CNS and they go outwards to muscles or glands and other structures
- they convey information to those structures and cause them to perform an action
sensory neurones
start at the receptor cells somewhere in the periphery, not in the CNS, and they convey information about the outside world or the inside world or the workings of that structure back to the CNS
somatic motor neurones
innervate skeletal muscles
- Skeletal muscles are under voluntary control so we can choose to contract those muscles
-some of them are able to involuntarily contract due to reflex arcs
visceral motor (sympathetic) neurons
innervate smooth/ cardiac muscles, glands
- never have conscious control over these
- fight or flight - stressful situations
visceral motor - parasympathetic
innervate smooth/ cardiac muscle, glands
- vegetative situations
somatic sensory neurones
- the modality they convey is called somatic sensation.
- We often just call that General sensation
○ E.g. touch, pressure, temp, pain, chemical stimulation
special sensation sensory neurones
- all of those other senses
olfaction, smell, Vision, sight, gustation, taste equilibrium (balance) sort of detection of the position of our head in space and how our head is moving in space and finally audition
visceral sensation sensory neurones
- the information about what’s going on in with our viscera (our organs)
what is the nervous system divided into
- CNS
- PNS
what does the central nervous system consist of
the brain and the spinal cord
- and the role of the central nervous system is to coordinate and integrate incoming and outgoing neural signals.
○ So thinking and learning for example but also reflexes as well.
○ We’ll have interneurons and our central nervous system which basically take an incoming signal, act on it and activate an outgoing signal
So it’s not just conscious functions., It’s also can be unconscious functions as well
PNS
Peripheral nervous system are always other nerves which are conveying information
to the periphery or conveying information back from the periphery.
pairs of spinal nerves
- 8 pairs of cervical
- 12 pairs of thoracic
- 5 pairs of lumbar
- 5 pairs of sacral
- 1 pair of coccygeal nerves
how are spinal nerves numbered
each set is numbered superior to inferior
what are the spinal nerves
always mixed nerves (motor and sensory) when they leave the vertebral column
- conduct neural impulses to and from CNS
cranial nerves
- 12 pairs
- they emerge from the central nervous system again and the vast majority of them emerge from the brain and emerge anteriorly to posteriorly.
They exit the skull anteriorly to posteriorly as well
Cranial nerves a little bit different in terms of where they emerge, how they are
named and how they function
- they emerge from the central nervous system again and the vast majority of them emerge from the brain and the emerge anteriorly to posteriorly.
- And they exit the skull anteriorly to posteriorly as well
Other way that they differ from the spinal nerves is that unlike spinal nerves They’re not necessarily mixed so much more specific in their function
- conduct neural impulses to and from CNS
.
where do cranial nerves leave the skull
through foramina
cranial nerve 1-3
1 - olfactory
2- optic
3 - oculometer
cranial nerve 4- 6
4 - trochlear
5 - trigeminal
6 - abducens
cranial nerve 7-9
7- facial
8 - vestibulocochlear
9 - glossopharyngeal
cranial nerve 10-12
10 -vagus
11 - spinal accessory
12 - hypoglossal
olfactory nerve
The olfactory nerve conveys sensory fibers only and those sensory fibers come from the nasal epithelium concerning olfaction (smell) it’s
associated with it is also something called cranial nerve 0
○ associated with possibly detecting pheromones, but it’s kind of not well understood in humans.
where does olfactory nerve enter skull
cribriform foramina.
optic nerve
Optic nerve is also sensory only and it conveys special sensory fibres from the retina concerning Vision.
So light waves hit your retina, they are transduced by the rod and Cone cells into action potentials both to convey that through neurons in your optic nerve
the left and the right sides merge together in this kind of eight shape and then split
again
that’s an easy way of spotting the optic nerve it got this 8 shape.
where does optic nerve enter the skull
optic canal
oculomotor nerve motor function
motor function in the orbital cavity
- We have two sets of muscles in the orbital cavity
○ We call them extraocular muscles and intraocular muscles
○ extraocular muscles are outside the eyeball - they move the eyeball
intraocular muscles are inside the eyeball and they alter the size and position of structures inside the eyeball to allow us to focus light waves and also to regulate the amount of light entering the eye ball
where does the oculomotor nerve convey somatic motor fibres to
the oculomotor nerve conveys somatic motor fibres to the medial rectus Superior, the inferior rectus and inferior oblique muscles
- these are all muscles that move the eyeball.
It also send somatic motor fibres over to the levator palpebrae superioris.
Contraction of this muscle elevates the upper eyelid and open your eyelids.
where does the oculomotor nerve convey parasympathetic fibres to
They go to the sphincter pupillae which is going to constrict the pupil to stop light waves getting in and the ciliary muscle which is important in focusing light onto the retina.
where does the oculomotor nerve convey proprioceptive fibres from
- LPS, MR, SR, IR, and IO
where does the oculomotor nerve enter the orbital into the skull
- it enters the orbital cavity because that’s where the eyeball is, but in a different opening to the optic nerve
- lateral to the optic nerve on each side, There’s this big crack in the back of the orbital cavity (a fissure) - called the superior orbital fissure and that’s where the oculomotor nerve enters
trochlear nerve
trochlear nerve is also a motor nerve and it conveys somatic motor fibers to another
one of the extraocular muscles.
It only innervates, The one muscle called The Superior oblique.
we’re going to have proprioceptive fibres coming from the superior oblique and they also pass through
the trochlear nerve.
where does trochlear nerve exit the skull
superior orbital fissure
trigeminal nerve
originates in the brain stem and arises between the pons and the cerebellum
- It is the largest of the cranial nerves
has 3 divisions:
- ophthalmic nerve (sensory only)
- maxillary nerve (sensory only)
- mandibular nerve (sensory and motor)
trigeminal sensory and motor route
There’s a large sensory route going to where it splits into three divisions
and there’s a small motor route going to the third division
what do the different divisions of the trigeminal nerve innervate
- Opthalmic nerve innervates the area above the upper eyelid and the scalp
○ Also the bridge of the nose - Maxillary division generally innervates the area from the lower eyelid to the upper lip
- The mandibular division generally innervates the area from the lower eyelid to the upper lip
Also the area immediately in front of the external ear
where does the trigeminal nerve convey somatic fibres to
- muscles of mastication
- mylohyoid
- tensor tympani
- tensor veli palatini
- anterior belly of digastric
where does the trigeminal nerve convey general sensory fibres from
- face
- oral, orbital and nasal cavities
- anterior part of the ehad
- most of the dura mater
where does the trigeminal nerve convey proprioceptive fibres from
- muscles of mastication
- mylohyoid, TVP, etc
- maxillary teeth
- mandibular teeth
where does trigeminal nerve enter the skull
- superior orbital fissue - first division
- foramen rotundum - 2nd division
- foramen ovale - conveys mandibualr division
where does the abducens nerve exit the skull through
superior orbital fissure
abducens nerve - motor
the abducens nerve conveys somatic motor fibres to lateral rectus
and proprioceptive fibres from the lateral rectus
where does the facial nerve convey somatic motor fibres to
muscles of facial expression
where does the facial nerve arise from
the ventral part of the brainstem between the pons and medulla
where does the facial nerve convey parasympathetic fibres to
- lacrimal gland
- submandibular gland
- sublingual gland
where does the facial nerve convey special sensory fibres from
- anterior 2/3 tongue - gustation (taste)
where does the facial nerve convey proprioceptive fibres from
muscles of facial expression
where does main part of facial nerve exit skull through
stylomastoid foramen
vestibulocochlear nerve - where does the vestibular division of the nerve convey
special sensory fibres from the vestibular system concerning equilibrium
vestibulocochlear nerve - where does the cochlear division of the nerve convey
special sensory fibres from the cochlea concerning hearing
where does the vestibulocochlear nerve enter the cranial cavity
through the interal acoustic meatus
what does the glossopharyngeal nerve convey motor fibres to
somatic motor fibres to: - stylopharyngeus
parasympathetic motor fibres to: parotid gland
where does the glossopharyngeal nerve convey general sensory fibres from
skin of external ear
where does the glossopharyngeal nerve convey special sensory fibres from
posterior 1/3 tongue - gustation (taste)
where does the glossopharyngeal nerve convey visceral sensory fibres from
- pharynx
- middle ear
- carotid body and sinus
- parotid gland
where does glossopharyngeal nerve enter/ exit the skull
through the jugular foramen
where does the vagus nerve convey somatic motor fibres to
- intrinsic muscles of larynx
- palatine muscles (except tensor veli palatini)
- pharyngeal muscles (except stylopharyngess)
- striated muscles in superior 2/3 oesophagus
where does the vagus nerve convey parasympathetic motor fibres to
- smooth muscles of the superior GI tract
- smooth muscles of trachea
- smooth muscles of bronchioles
- cardiac muscle
where does the vagus nerve convey general sensory fibres from
- pinna
- external auditory meatus
- dura matter of posterior cranial fossa
where does the vagus nerve convey special sensory fibres from
epiglottis and palate - gustation (taste)
where does the vagus nerve convey visceral sensory fibres from
- base of tongue
- pharynx
- larynx
- trachea
- bronchi
- superior GI tract
- heart
where does the vagus nerve enter/ exit the skull through
jugular foramen
where does spinal accessory nerve convey somativ motor fibres to
sternocleidomastoid
trapezius
spinal accessory nerve
emerges from the lateral surface of superior part of spinal cord
superior to the rootlets of C1 (the first spinal nerve)
where does spinal accessory nerve enter and exit the skull through
enters at the foramen magnum
exits at the jugular foramen
where foes the hypoglossal nerve convey somatic motor fibres to
all intrinsic muscles of the tongue
- extrinsic muscles of the tongue (except palatoglossus)
hypoglossal nerve
emerges from ventral surface of medulla
where does hypoglossal nerve exit the skull
hypoglossal canal
