NSCI 2101 Exam 2 Lec 3

spinal nerves exit through ______

the intervertebral foramina

how do cranial nerves enter and exit the CNS?

through foramina in the skull

how many pairs of cranial nerves do humans have?

12

cranial nerves are organized by ____

function

which three pairs of cranial nerves ONLY carry special senses?

olfactory (CN1), optic (CN2), and vestibulocochlear (CN8)

olfactory nerve

• senses smell

• bunch of nerve cells derived from the olfactory placodes that extend their axons down into the nasal cavity

• cells that form the olfactory nerves are sensitive to odorants

• olfactory tracts carry information about smell into the cerebral cortex

how does information travel from the olfactory nerve to the cerebral cortex?

odorant binds to cell → cell fires → info is sent along axons that go through the cribriform plates → synapse on the olfactory bulb → olfactory tracts carry information about smell into the cerebral cortex

optic nerve

looks like an x and transmits information about sight

vestibulocochlear nerve

• sticks out of the inferior pontine sulcus that forms the boundary between the medulla and pons

• out on the lateral side of the brain

• most lateral nerves, also the biggest

• made of two parts: vestibular apparatus and cochlea

vestibular apparatus

part of the vestibulocochlear nerve that is in control of balance

• senses head position and movement through cilia

cochlea

part of the vestibulocochlear nerve

• physically connected to vestibular apparatus

• senses sound through movement of cilia

which five cranial nerves ONLY innervate skeletal muscle?

oculomotor (CN3), trochlear (CN4), abducens (CN6), spinal accessory (CN11), hypoglossal (CN12)

which cranial nerves allow the eyes to move?

oculomotor, trochlear, and abducens

oculomotor nerve

• controls 4/6 extraocular skeletal muscles (plus the eyelid)

• includes the superior rectus on the top of the eye

• inferior rectus on the bottom of the eye

• inferior oblique which twists and upholds the eye medially, but causes it to rotate a bit

• medial rectus on medial side of the eye

• also deals with parasympathetic output of the oculomotor nerve: focuses lens and constricts pupil

trochlear nerve

• only nerve not visible from the ventral view of the brain

• only nerve that exits the dorsal side of the brain

• between the pons and the midbrain

  • can see it on the dorsal side of the brainstem kind of

• includes superior oblique

  • on the top and goes out the back of the eye and directs the gaze down and out

  • corresponds to interior oblique but in the opposite direction

abducens nerve

• exits the inferior pontine sulcus, most medial nerve

• innervates the lateral rectus muscle

  • pulls on your eye to the left or to the right

  • the muscles move in tandem to the opposite direction

Spinal accessory nerve

• neck and shoulders

  • Weird because the cell bodies are not in the brain, they are in the upper spinal cord 

  • From C5 up, the motor neurons in the spinal cord don’t send their axons out to the ventral roots, they send their axons straight up the side of the spinal cord and enter the skull through the foramen magnum 

  • The nerve then exits the skull through the jugular foramen 

  • Innervates trapezius and sternocleidomastoid

sternocleidomastoid

is on the side of your neck and allows you to turn your head

hypoglossal nerve

• innervates the tongue 

• only motor to the tongue but not sensory to the tongue

what are the three mixed-function cranial nerves?

facial (CN7), glossopharyngeal (CN9), and vagus (CN10)

what nerve innervates muscle but also carries “general sensation” information (touch, vibration, pain)?

trigeminal nerve

trigeminal nerve

• (jaw muscles, sensation for face, head, mouth)

  • next biggest nerve in the head after the optic nerve 

  • exits the middle side of the pons 

  • Muscles of mastication 

    • allow for chewing 

  • Cutaneous sensation to face and head

  • Three branches to the trigeminal nerve

facial nerve

• Exits from the inferior pontine sulcus

• Innervates muscles of facial expression

• Innervates some autonomic ganglia 

• Special sensory (taste)

  • Innervates taste receptors in the anterior ⅔ of the tongue

glossopharyngeal nerve

• Tongue and throat 

• Innervates the posterior ⅓ of the tongue 

• Does both taste and general sensation 

• Also senses blood pressure and oxygen level in carotid artery

Vagus nerve

• Innervates skeletal muscles of throat and larynx 

• Allows us to talk 

• Muscles involved in swallowing 

• Autonomic input to heart and gut

  • Slows heart, speeds digestion 

• Special sensation (taste) 

  • back of throat

• General sensation

  • Behind ear (small region)

  • Larynx

• Also senses blood oxygenation and CO2

  • Sensors in aortic arch

what do the mixed function nerves all have in common?

• All innervate skeletal muscle

• All innervate autonomic ganglia

• All carry general sensory afferents

• All carry special sensory afferents

• Two (glossopharyngeal and vagus) carry afferents relaying information about O2, CO2, and/or blood pressure

what is the mnemonic for cranial nerves?

• On (olfactory)

• Old (optic)

• Olympus’s (oculomotor)

• Towering (trochlear)

• Tops (trigeminal)

• A (abducens)

• Finn (facial)

• And (“auditory”, i.e. vestibulocochlear)

• German (glossopharyngeal)

• Viewed (vagus)

• Some (spinal accessory)

• Hops (hypoglossal)

what are the lines pointing to?

cranial foramena

what is the arrow pointing at?

cribiform plate

what is 1?

olfactory bulb

what is 2?

cribriform plate

what is 3?

olfactory nerves

cribriform plate

transmits the olfactory nerves that carry the sense of smell

olfactory bulb

the region in the brain receiving input from the olfactory neurons in the nasal olfactory epithelium. olfactory nerves synapse on them

what are 1?

olfactory tracts

what are 2?

olfactory bulbs

what are the arrows pointing at?

the optic nerve

what are the arrows pointing at?

vestibulocochlear nerve

what is 1?

vestibular apparatus

what is 2?

cochlea

what is 1?

oculomotor nerve

what is 2?

trochlear nerve

what is 3?

abducens nerve

what is 1?

superior rectus muscles

what is 2?

inferior rectus muscles

what is 3?

inferior oblique muscles

what is 4?

medial rectus muscles

what are the arrows pointing at?

trochlear nerve

what dat

superior oblique muscle

what are the arrows pointing at?

abducens nerve

what are the lines pointing at

lateral rectus muscles

what are the arrows pointing at?

spinal accessory nerve

what dat

hypoglossal nerve

IGNORE THE RED ARROW but what is the black arrow pointing at

trigeminal nerve

name these muscles

1 is temporalis and 2 is masseter

what are the arrows pointing at

facial nerves

autonomic ganglia in the facial nerves result in what?

tearing, nose-running, and salivating

WHAT DIS

glossopharyngeal nerve

autonomic ganglia in the glossopharyngeal nerve result in…

salivation

what dis

vagus nerve