Lecture 17 - Brain and Cranial Nerves

Question 1

What parts of the brain are proportionally larger in humans compared to other primates?

Answer 1

Frontal and parietal lobes

-humans have largest relative brain size compared to other primates

Question 2

Which germ layer forms the central nervous system (and skin)?

Answer 2

Ectoderm

Question 3

Neurulation

Answer 3

1st: gene signaling from the notochord causes rapid growth in nearby ectoderm
2nd: thickening neural crest comes together, forming neural tube

Question 4

What does the prosencephalon give rise to?

Answer 4

Prosencephalon gives rise to forebrain structures.

• Telencephalon = Cerebrum
• Diencephalon = Thalamus/Hypothalamus

Question 5

What does the mesencephalon give rise to?

Answer 5

Midbrain

Question 6

What does the rhombencephalon give rise to?

Answer 6

Rhombencephalon gives rise to hindbrain structures.

• Metencephalon = Pons/Cerebellum
• Myelencephalon = Medulla Oblongata

Question 7

Synaptic Pruning

Answer 7

Little used dendritic connections are selectively pruned at several stages during adolescence, continuing into adulthood.

*Schizophrenia may be due to excessive pruning

Question 8

Which arteries provide all blood supply to the brain?

Answer 8

Carotid and vertebral arteries.

• Vertebral arteries pass through foramen magnum
• Internal carotid supplies blood to brain (enters through carotid canal on temporal bone)
• External carotid supplies blood to face and scalp

Question 9

Circle of Willis

Answer 9

• circular arterial connection at the base of the skull
• forms an anastomosis

*aneurysms most commonly formed here

Question 10

Anastomosis

Answer 10

• series of connections between blood vessels
• provides redundant blood flow in case of blockages

Question 11

The brain takes up 2% of body mass but 20% of basal metabolic consumption. Why?

Answer 11

The brain is so expensive because we need to maintain ion cencentration gradients for neuron firing.

Question 12

Cerebrospinal Fluid

Answer 12

• brain is suspended in CSF
• fills the subarachnoid space
• provides buoyancy and cushion for the brain
• produced and stored in the ventricles, connected spaces/canals located in the center of the brain
• drains into the venous system

Question 13

What holds the veins (sinuses) of the brain in place?

Answer 13

Dural bands

Question 14

CN I

Answer 14

Olfactory Nerve

• sensory (smell)
• passes through the cribiform plate on the ethmoid bone
• origintes at the cerebrum

Question 15

CN II

Answer 15

Optic Nerve

• sensory (sight)
• passes through the optic canal on the sphenoid bone
• originates at thte cerebrum

Question 16

CN III

Answer 16

Oculomotor Nerve

• motor: eye and eyelid movement, pupil constriction, lens deformation (superior rectus, medial rectus, inferior rectus, inferior oblique)
• autonomic (parasympathetic) innervation of the constrictor pupillae and ciliary muscles
• passes through superior orbital fissure on the sphenoid
• originates at the midbrain

Question 17

CN IV

Answer 17

Trochlear Nerve

• motor: eye movement
  (voluntary: superior oblique muscle)
• passes through superior orbital fissure on the sphenoid
• originates at the midbrain

Question 18

CN VI

Answer 18

Abducens Nerve

• motor: eye movement
  (voluntary: lateral rectus muscle)
• passes through superior orbital fissure on the sphenoid
• originates at the hindbrain

Question 19

CN V

Answer 19

Trigeminal Nerve

• trigeminal ganglion: afferent (sensory) bodies
• separated into 3 divisions: opthalmic, maxillary, mandibular

Question 20

CN V¹

Answer 20

Opthalmic Division of the Trigeminal Nerve

• sensory: eye (cornea, iris, conjunctive, lacrimal glands), part of nasal mucosa, skin of eyelids, brows, forehead, nose
• passes through superior orbital fissure on the sphenoid

Question 21

CN V²

Answer 21

Maxillary Division of the Trigeminal Nerve

• sensory: nasal cavity, palate, upper teeth, skin of cheek, temple, lower eyelid, lateral nose, upper lip
• passes through the foramen rotundum on the sphenoid

Question 22

CN V³

Answer 22

Mandibular Division of the Trigeminal Nerve

• sensory: anterior 2/3 of tongue (not taste), lower teeth, skin of ear, temple, lateral cheek, lower lip, chin
• motor: chewing muscles, jaw/palate/ear muscles
• passes through foramen ovale on the sphenoid

Question 23

CN VII

Answer 23

Facial Nerve

motor - voluntary: digastric, stylohyoid, stapedius, facial expression msucles

motor -parasympathetic: lacrimal and salivary glands

sensory: anterior 2/3 of tongue (taste)

• passes through internal auditory meatus
• exits skull through stylomastoid foramen

Question 24

CN VIII

Answer 24

Vestibularcochlear Nerve

• sensory: equilibrium (vestibular nerve) and hearing (cochlear nerve)
• passes through external auditory meatus

Question 25

CN IX

Answer 25

Glossopharyngeal Nerve _motor_ - voluntary: stylopharyngeus _motor_ - parasympathetic: parotid (salivary) glands _sensory_: posterior 1/3 of tongue (sensation and taste) -passes through jugular foramen on temporal & occiptal bones

Question 26

CN X

Answer 26

Vagus Nerve motor - voluntary: throat, palate, larynx muscles motor - parasympathetic: heart, digestive tract, lungs sensory: throat, palate, larynx \*MANY, MANY FUNCTIONS -passes through jugular foramen intemporal & occipital bones

Question 27

CN XI

Answer 27

Accessory Nerve - motor: sternocleidomastoid & trapezius (voluntary) - passes through jugular foramen on temporal & occipital bones

Question 28

CN XII

Answer 28

Hypoglossal Nerve - motor: most tongue muscles (voluntary) - passes through hypoglossal canal

Question 29

Which cranial nerves innervate the nose?

Answer 29

CN I (olfaction) CN V^1,2 (sensation)

Question 30

Which cranial nerves innervate the eyes?

Answer 30

CN II (vision) CN V¹ (sensation) CN III, IV, VI (motor)

Question 31

Which cranial nerve(s) innervate the ears?

Answer 31

CN VIII (hearing, balance)

Question 32

Which cranial nerves innervate the facial structures?

Answer 32

CN V^1,2,3 (sensory) CN VII (motor)

Question 33

Which cranial nerves innervate the tongue?

Answer 33

CN V³ (sensory - anterior 2/3 sensation) CN VII (sensory - anterior 2/3 taste) CN IX (sensory - posterior 1/3 sensation and taste) CN XII (motor)

Question 34

Which cranial nerve(s) pass through the cribiform plate on the ethmoid bone?

Answer 34

CN I - Olfactory

Question 35

Which cranial nerve(s) pass through the optic canal?

Answer 35

CN II - Optic

Question 36

Which cranial nerves pass through the superior orbital fissure?

Answer 36

CN III - Oculomotor CN IV - Trochlear CN V¹ - Opthalmic division of the Trigeminal CN VI - Abducens

Question 37

Which cranial nerve(s) passes through the foramen rotundum?

Answer 37

CN V² - Maxillary division of the Trigeminal

Question 38

Which cranial nerve(s) pass through the foramen ovale?

Answer 38

CN V³ - Mandibular division of the Trigeminal

Question 39

Which cranial nerves pass through the internal auditory/acoustic meatus?

Answer 39

CN VII - Facial CN VIII - Vestibulocochlear

Question 40

Which cranial nerves pass through the jugular foramen?

Answer 40

CN IX - Glossopharyngeal CN X - Vagus CN XI - Accessory

Question 41

Which cranial nerve(s) pass through the hypoglossal canal?

Answer 41

CN XII - Hypoglossal

Question 42

Cranial nerve names mneumonic

Answer 42

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Question 43

Cranial nerve function mneumonic

Answer 43

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