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Bio 137 > Cranial Nerves > Flashcards

Cranial Nerves Flashcards

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1
Q

The 12 pairs of cranial nerves are so named because

A

they pass through various foramina in the bones of the cranium and, with one exception, arise from the brain inside the cranial cavity

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2
Q

Like the 31 pairs of spinal nerves, they are part of the

A

peripheral nervous system (PNS).

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3
Q

For cranial nerves

A

The numbers indicate the order, from anterior to posterior, in which the nerves arise from the brain. The names designate a nerve’s distribution, structure, or function.

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4
Q

Three cranial nerves (I, II, and VIII) carry axons of sensory neurons and thus are called

A

special sensory nerves. These nerves are unique to the head and are associated with the special senses of smelling, seeing, and hearing.

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5
Q

Five cranial nerves (III, IV, VI, XI, and XII) are classified as

A

motor nerves because they contain only axons of motor neurons as they leave the brainstem

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6
Q

Pharyngeal (branchial) motor axons

A

innervate skeletal muscles that develop from the pharyngeal (branchial) arches (see Figure 14.28). These neurons leave the brain through the mixed cranial nerves and the accessory nerve

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7
Q

Somatic motor axons

A

innervate skeletal muscles that develop from head somites (eye muscles and tongue muscles). These neurons exit the brain through five motor cranial nerves (III, IV, VI, XI, and XII).

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8
Q

four cranial nerves (V, VII, IX, and X) are mixed nerves which means

A

—they contain axons both of sensory neurons entering the brainstem and motor neurons leaving the brainstem.

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9
Q

remember that all____________ are paired structures.

A

cranial and spinal nerves

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10
Q

The olfactory (I) nerve (ōl-FAK-tō-rē; olfact- = to smell) is

A

entirely sensory; it contains axons that conduct nerve impulses for olfaction, the sense of smell

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11
Q

The olfactory epithelium occupies

A

the superior part of the nasal cavity, covering the inferior surface of the cribriform plate and extending down along the superior nasal concha.

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12
Q

The olfactory sensory neurons within the olfactory epithelium are

A

bipolar neurons

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13
Q

Bundles of axons of olfactory sensory neurons extend through about 20 olfactory foramina in the cribriform plate of the ethmoid bone on each side of the nose. These 40 or so bundles of axons collectively form

A

the right and left olfactory nerves.

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14
Q

Olfactory nerves end in the brain in paired masses of gray matter called

A

the olfactory bulbs, two extensions of the brain that rest on the cribriform plate.

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15
Q

Within the olfactory bulbs, the axon terminals of olfactory sensory neurons form synapses with the dendrites and cell bodies of the next neurons in the olfactory pathway. The axons of these neurons make up

A

the olfactory tracts, which extend posteriorly from the olfactory bulbs

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16
Q

Axons in the olfactory tracts end

A

in the olfactory cortex in the temporal lobe of the cerebrum.

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17
Q

Loss of the sense of smell, is called

A

anosmia (an-OZ-mē-a),

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18
Q

The optic (II) nerve (OP-tik; opti- = the eye, vision)

A

is entirely sensory and is technically a tract of the brain and not a nerve; it contains axons that conduct nerve impulses for vision

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19
Q

Axons of all ganglion cells in the retina of each eye join to form

A

an optic nerve, which passes through the optic foramen.

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20
Q

About 10 mm (0.4 in.) posterior to the eyeball,

A

the two optic nerves merge to form the optic chiasm

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21
Q

Within the chiasm,

A

axons from the medial half of each eye cross to the opposite side; axons from the lateral half remain on the same side.

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22
Q

Posterior to the chiasm,

A

the regrouped axons, some from each eye, form the optic tracts.

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23
Q

Most axons in the optic tracts end

A

in the lateral geniculate nucleus of the thalamus

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24
Q

in the lateral geniculate nucleus of the thalamus optical neurons

A

synapse with neurons whose axons extend to the primary visual cortex in the occipital lobe of the cerebrum

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25
Q

In sequence, visual signals are relayed

A

from rods and cones to bipolar cells to ganglion cells.

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26
Q

Blindness due to a defect in or loss of one or both eyes is called

A

anopia (an-Ō-pē-a).

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27
Q

The oculomotor, trochlear, and abducens nerves are the cranial nerves

A

that control the muscles that move the eyeballs.

28
Q

The oculomotor, trochlear, and abducens nerves are all

A

motor nerves that contain only motor axons as they exit the brainstem.

29
Q

Sensory axons from the extraocular (extrinsic eyeball) muscles

A

begin their course toward the brain in each of these nerves, but eventually these sensory axons leave the nerves to join the ophthalmic branch of the trigeminal nerve

30
Q

sensory axons do not return to the brain in the

A

oculomotor, trochlear, or abducens nerves

31
Q

The oculomotor (III) nerve (ok′-ū-lō-MŌ-tor; oculo- = eye; -motor = a mover) has its motor nucleus

A

in the anterior part of the midbrain.

32
Q

The oculomotor nerve extends anteriorly and divides into

A

superior and inferior branches, both of which pass through the superior orbital fissure into the orbit

33
Q

Axons in the superior branch of the oculomotor nerve innervate the

A

superior rectus (an extraocular muscle) and the levator palpebrae superioris (the muscle of the upper eyelid)

34
Q

Axons in the inferior branch of the oculomotor nerve supply the

A

medial rectus, inferior rectus, and inferior oblique muscles—all extraocular muscles. These somatic motor neurons control movements of the eyeball and upper eyelid

35
Q

The oculomotor (III) nerve has

A

the widest distribution among extraocular muscles.

36
Q

Damage to the oculomotor (III) nerve causes

A

strabismus
ptosis
diplopia

37
Q

strabismus (stra-BIZ-mus)

A

(a condition in which both eyes do not fix on the same object, since one or both eyes may turn inward or outward)

38
Q

ptosis (TŌ-sis)

A

(drooping) of the upper eyelid, dilation of the pupil, movement of the eyeball downward and outward on the damaged side, loss of accommodation for near vision

39
Q

diplopia (di-PLŌ-pē-a)

A

(double vision).

40
Q

Trochlear (IV) nerve damage can result in

A

strabismus and diplopia.

41
Q

With damage to the abducens (VI) nerve,

A

the affected eyeball cannot move laterally beyond the midpoint, and the eyeball usually is directed medially. This leads to strabismus and diplopia.

42
Q

The inferior branch of the oculomotor nerve also supplies

A

parasympathetic motor axons to intrinsic eyeball muscles, which consist of smooth muscle. They include the ciliary muscle of the eyeball and the circular muscles (sphincter pupillae) of the iris.

43
Q

Describe how the oculomotor nerve stimulates the smooth muscle in the iris of the eye

A

Parasympathetic impulses propagate from a nucleus in the midbrain (accessory oculomotor nucleus) to the ciliary ganglion, a synaptic relay center for the two motor neurons of the parasympathetic nervous system. From the ciliary ganglion, craniosacral (parasympathetic) motor axons extend to the ciliary muscle, which adjusts the lens for near vision (accommodation). Other craniosacral motor axons stimulate the circular muscles of the iris to contract when bright light stimulates the eye, causing a decrease in the size of the pupil (constriction).

44
Q

what is the ciliary ganglion

A

a synaptic relay center for the two motor neurons of the parasympathetic nervous system.

45
Q

The trochlear (IV) nerve (TRŌK-lē-ar; trochle- = a pulley) is

A

the smallest of the 12 cranial nerves and is the only one that arises from the posterior aspect of the brainstem.

46
Q

describe the location of the trochlear nerve

A

The somatic motor neurons originate in a nucleus in the midbrain (trochlear nucleus), and axons from the nucleus cross to the opposite side as they exit the brain on its posterior aspect. The nerve then wraps around the pons and exits through the superior orbital fissure into the orbit.

47
Q

The somatic motor axons of the trochlear nerve innervate

A

the superior oblique muscle of the eyeball, another extraocular muscle that controls movement of the eyeball

48
Q

Neurons of the abducens (VI) nerve (ab-DOO-senz; ab- = away; -ducens = to lead)

A

originate from a nucleus in the pons (abducens nucleus). Somatic motor axons extend from the nucleus to the lateral rectus muscle of the eyeball, an extraocular muscle, through the superior orbital fissure of the orbit

49
Q

The abducens nerve is so named because

A

nerve impulses cause abduction (lateral rotation) of the eyeball.

50
Q

The trigeminal (V) nerve (trī-JEM-i-nal = triple, for its three branches) is

A

a mixed cranial nerve and the largest of the cranial nerves.

51
Q

The trigeminal nerve emerges from

A

two roots on the anterolateral surface of the pons.

52
Q

The large sensory root of the trigeminal nerve has a swelling called

A

the trigeminal (semilunar) ganglion

53
Q

the trigeminal (semilunar) ganglion

A

is located in a fossa on the inner surface of the petrous portion of the temporal bone.

54
Q

As indicated by its name, the trigeminal nerve has

A

three branches: ophthalmic, maxillary, and mandibular

55
Q

The ophthalmic nerve (of-THAL-mik; ophthalm- = the eye),

A

is the smallest branch of the trigeminal nerve, which passes into the orbit via the superior orbital fissure.

56
Q

The maxillary nerve (maxilla = upper jawbone) is

A

a branch of the trigeminal nerve that is intermediate in size between the ophthalmic and mandibular nerves and passes through the foramen rotundum.

57
Q

The mandibular nerve (mandibula = lower jawbone),is

A

the largest branch of the trigeminal nerve, which passes through the foramen ovale.

58
Q

The three branches of the trigeminal (V) nerve leave the cranium through

A

the superior orbital fissure, foramen rotundum, and foramen ovale.

59
Q

Neuralgia (pain) relayed via one or more branches of the trigeminal (V) nerve, caused by conditions such as inflammation or lesions, is called

A

trigeminal neuralgia (tic douloureux).

60
Q

Sensory axons in the trigeminal nerve carry nerve impulses for

A

touch, pain, and thermal sensations (heat and cold).

61
Q

The ophthalmic nerve contains

A

sensory axons from the skin over the upper eyelid, cornea, lacrimal glands, upper part of the nasal cavity, side of the nose, forehead, and anterior half of the scalp.

62
Q

The maxillary nerve includes

A

sensory axons from the mucosa of the nose, palate, part of the pharynx, upper teeth, upper lip, and lower eyelid.

63
Q

The mandibular nerve contains

A

sensory axons from the anterior two-thirds of the tongue (not taste), cheek and mucosa deep to it, lower teeth, skin over the mandible and side of the head anterior to the ear, and mucosa of the floor of the mouth.

64
Q

The sensory axons from the three branches of the trigeminal nerve enter

A

the trigeminal ganglion, where their cell bodies are located, and terminate in nuclei in the pons.

65
Q

Branchial motor neurons of the trigeminal nerve are

A

part of the mandibular nerve and supply muscles of mastication (masseter, temporalis, medial pterygoid, lateral pterygoid, anterior belly of digastric, and mylohyoid muscles, as well as the tensor veli palatini muscle in the soft palate and tensor tympani muscle in the middle ear). These motor neurons mainly control chewing movements.

66
Q

The facial (VII) nerve (FĀ-shal = face) is

A

a mixed cranial nerve

67
Q

the facial nerve’s sensory axons

A

extend from the taste buds of the anterior two-thirds of the tongue, which enter the temporal bone to join the facial nerve.

Bio 137 (9 decks)

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