7. Brain & Cranial Nerves Pt. 1 Flashcards
Describe the meninges layers of the brain.
dura mater (most outside) -> arachnoid mater (stuck onto dura mater) ->pia mater (envelops brain)
Identify the artery shown below. Why is this artery extremely vulnerable?
middle meningeal artery: travels through foramen spinosum to enter skull and splits at Pterion
Pterion is is very fragile (weakest spot of brain) because sutures => bones less durable => can be easily ruptured
Identify these three parts of the brain.
pink: cerebrum
green: brainstem
blue: cerebellum
Identify the various lobes of the brain
purple: occipital lobe
green: parietal lobe
turquoise: frontal lobe
blue: temporal lobe
(we have 2 of each lobe! one on each side)
Explain what each lobe is responsibe for?
- occipital and parietal lobe: for sensory and somatosensory = CONCRETE EXPERIENCE
- Temporal lobe: temporal intergrative cortex = REFLECTIVE OBSERVATION (ex: studying)
- frontal lobe: frontal intergrative cortex = ABSTRACT HYPOTHESIS (develop thoughts and questions)
- parietal lobe: premotor and motor cortex =ACTIVE TESTING
What separates the two hemispheres of the brain?
longitudinal fissure
Where is the grey matter situated in the brain? white matter?
- grey mater = cortex = outside (c bodies)
- white matter = inside brain (myelinated axon)
What is sulcus? gyrus? what is their function?
sulcus = valleys = dips
gyrus = peaks
function: increase surface area of brain
What is another name of cerebrum?
telencephalon
Identify the brainstem on the picture and its various sub structures.
blue+green+orange = brainstem
orange= medulla oblangate
green= pons
blue =midbrain
Identify the structure in yellow and its different sub parts. What is the function of each sub part. What binds all of these structures?
yellow = diacephelon = thalamus (integrates all sensory except smell)+ hypothalamus + pituatary gland (regulates hormones)
dura mater binds all these structures
Where is the pituatary gland situated?
in the hypophyseal fossa near the infundibulum
What is the function of the corpus callosum?
allows for communication between 2 hemispheres
What causes a seizure?
miscommunication between 2 hemispheres via the corpus callosum
Identify the structures.
yellow = diacephelon
blue = midbrain
green = pons
orange = medulla oblangata
What parts of the brain inserts in the anterior, middle and posterior cranial fossa?
anterior cranial fossa = frontal love
middle cranial fossa = temporal lobe
posterior cranial fossa = cerebellum and brainstem
Where do most cranial nerves come off from?
brainstem
What develops out of the pons? What is its function?
cerebellum (responsible for motor function)
Where does the medulla oblongata dip out of the skull from?
foramen magnum
Name all 12 pairs of cranial nerve and the foramina in which they enter.
Identify what there nerves innervate:
a) general somatic
b) general visceral
c) special somatic
d) special visceral
a) general somatic: skeletal muscle and skin
b) general visceral: blood vessels, glands, intraocular muscle
c) special somatic: vision, hearing
d) special visceral: taste, smell
Name the ‘false’ cranial nerves. Why are they called false?
olfactory n and optic n
they are called false because they come from brain tissue in development
Identify the nerve shown at A, B, C. Identify the different part of this nerve. What type of nerve is it? What is it responsible for? What foramina does it travel through?
OLFACTORY NERVE (CN I)
c) olfactory tract -> b) olfactory bulb which then sends out fibers into the cribiform foramina
it is responsible for smell which is a special visceral
olfactory n = special sensory nerve
Identify the nerve shown at D, E, F. Identify the different part of this nerve. What type of nerve is it? What is it responsible for? What foramina does it travel through?
OPTIC NERVE (CN II)
F) optic tract -> e) optic chiasm -> d) optic n which travels through the optic canal
responsible for sight = special somatic
optic nerve = special somatic n
Why is it important to check on the optic nerve pressure?
in your optic nerve, there is an artery that runs right in the middle: it is important to check optic nerve pressure because if there is too much pressure it can damage the blood vessel and the eye wont receive any oxygenated blood => glycoma
Looking at the inferior part of the brain, how are all 12 pairs of cranial nerves organized?
CN I, II, III: down the middle
CN IV, V: round the pons
CN VI: back to center
CN VII, VIII, IX, X, XI: on side of medulla oblongata
CNXII: back in center
What is the junction called between the pons and medulla oblongata?
pontomedullary junction
Which cranial nerves are found in the midbrain? pons? pontomedullary junction? medulla oblongata?
midbrain: 3, 4
pons: 5
pontomedullary junction: 6, 7, 8
medulla oblongata: 9, 10, 11, 12
Identify this muscle? Where does it originate from? What movement is it responsible for?
LEVATOR PALPEBRAE SUPERIORIS M
- originates from common tendinous ring
- is not responsible for eye movement
- elevates eyelids
(is the most superficial muscle when looking in the lab)
inn: oculomotor n
Where do all extraocular muscles connect from? What is the exception?
common tendinous ring (central angle of pull) except inferior oblique
Where do all rectus muscle attach? oblique muscles?
rectus muscles attach on the anterior part of the eyeball
oblique muscle attach on the posterior part of the eyeball
Identify all the extraocular muscles. Identify the various axis in the eye.
- red: levator palpebrae superior muscle
- yellow: superior oblique
- orange: superior rectus muscle
- purple: medial rectus
- blue: lateral rectus
green: inferior oblique
pink: inferior rectus
(in black: common tendinous ring)
red axis = optic axis (straight at what were looking at)
longitudinal axis: side to side
What is torsion of the eye?
movement of superior pupil torwards or away from midline
Identify the muscle in orange: what movement is it responsible for
SUPERIOR RECTUS M = elevated intorsion (torwards nose)
inn oculomotor n
Identify the muscle in purple: what movement is it responsible?
MEDIAL RECTUS M= ADDUCTION
inn oculomotor n
Identify the muscle in pink: what movement is it responsible for?
INFERIOR RECTUS M = depression extorsion
inn oculomotor n
Identify the muscle in blue: what movement is it responsible for?
LATERAL RECTUS: abduction m
inn abducent n
Identify the muscle in green: what movement is it responsible for?
inferior oblique: elevation extorsion (not on tendinous ring)
(bc from bottom: pulls eye up)
attaches onto trochlea uses it as lever
inn oculomotor n
Identify the muscle in yellow: what movement is it responsible for?
superior oblique: depression intorsion
attaches onto trochlea
inn trochlear n
Identify the three nerves. What do theu innervate? What foramina can they be found in? What type of nerves are these?
a) OCULOMOTOR N (CN III)
inn levator palpabrae superios m, superior rectus, medial rectus, inferior rectus, inferior oblique
b) trochlear n (cn iv)
superior oblique
c) abducent (cn v)
lateral rectus
all found in the superior orbital rectus
=motor nerves
Explain the automatic innervation of the eye.
- Bright light: constriction of the pupil by the oculomotor nerve, its parasympathetic part (presynaptic-postsynaptic) acts on sphincter pupillae m
- dim light: dilation of pupil by sympathetic trunk T1-T4) (post synaptic neuron) acts on dilator pupillae
Draw out the eye and the summarize the actions and the innervation of each eye muscle.
inferior muscles do extortion
superior muscles do intorsion
What occurs during a concussion to your brain? Which nerves are most vulnerable to concussions? How can you test if someone has a concussion?
Concussions: hit head on one side, spring back effect
=> brain moves around which may lead to lobe issues and problems at the base of the brain when CN are anchored by meninges but concussions put a strain on the cranial nerves especially
CNIII: oculomotor nerve
CNIV: trochlear n
CN VI: abducent n
You can test if someone has a concussion by testing their vision as trochlear n, oculomotor n and abducent n travel through the superior orbital fissure to the eyes
Testing for Cranial Nerve Damage: How do you test for the oculomotor nerve?
The parasympathetic branch of the oculomotor nerve is responsible for the constriction of the pupil.
=> shine line in patient’s eye to see for pupillary constriction
Testing for Cranial Nerve Damage: How do you test if the abducent nerve is damaged?
Abducent nerve innervates the lateral rectus muscle: test to see if patient can abduct eye
Testing for Cranial Nerve Damage: How do you test if your trochlear nerve is damaged?
trochlear nerve is responsible for innervation to the superior oblique muscle (function: intorsion and depression)
but other muscles such as superior rectus does intorsion and inferior rectus does depression
=> need to isolate superior oblique: ask patient to adduct eye and look down (then only the superior oblique would be performing adduction)
How do you isolate superior rectus?
Superior rectus is innervated by the occulomotor n and is reponsible for elevation and intorsion
=> ask patient to look up and out (only SR will perform elevation)
How do you isolate the inferior oblique muscle?
inferior oblique is innervated by the oculomotor n and does extorsion and elevation
=> have patient adduct eye and look up (only muscle that contributes to elevation)
How do you isolate the inferior rectus muscle?
inferior rectus is innervated by the oculomotor n and is responsible for extorsion and depression
=> ask patient to abduct and depress eye (only muscle that will depress eye)
