martin chapter 6

Question 1

what does the trigeminal system mediate?

Answer 1

somatic sensations (mechanosensations and the protective senses-temperature, pain and itch) from the face and head

Question 2

how many pairs of cranial nerves do we have?

Answer 2

12

Question 3

what do cranial nerves innervate?

Answer 3

face and head

Question 4

where does the olfactory nerve (I) enter?

Answer 4

in the cerebral hemisphere. it mediates the sense of smell

Question 5

where does the optic nerve (II) enter?

Answer 5

in the thalamus. it mediates vision

Question 6

the other 10 cranial nerves enter and leave which structure?

Answer 6

the brain stem

Question 7

which is the only cranial nerve located in the dorsal brain stem surface?

Answer 7

the trochlear nerve (IV)

Question 8

in which part of the brain stem do the oculomotor (III) and trochlear (IV) nerve exit?

Answer 8

in the midbrain

Question 9

how many cranial nerves does the pons contain?

Answer 9

4

Question 10

which cranial nerve is located in the middle of the pons?

Answer 10

the trigeminal nerve (V). it consists of both sensory and motor functions->is characterized by both sensory and motor roots
the sensory root innervates the facial skin and mucous membranes of the oral and nasal cavities and the teeth.
The motor root contains axons that innervate jaw muscles

Question 11

what does the abducens (VI) nerve innervate?

Answer 11

it is a motor nerve and innervates eye muscles

Question 12

the facial nerve (VII)

Answer 12

-mixed nerve
-the motor root innervates the facial muscles that determine our expressions
-the sensory root innervates taste buds and mediates taste

Question 13

what’s the name of the facial sensory root?

Answer 13

intermediate nerve

Question 14

the vestibulocochlear nerve (VIII)

Answer 14

-sensory nerve
-2 separate components
vestibular component innervates the semicircular canals, utricle and saccule and mediates balance
chochlear component innervates the organ of Corti and serves hearing

Question 15

the 4 cranial nerves associated with the pons

Answer 15

-facial (VII)
-Abducens (VI)
-Trigeminal (V)
-Vestibulocochlear (VIII)

Question 16

how many cranial nerves does the medulla have?

Answer 16

4

Question 17

name of the cranial nerves in the medulla

Answer 17

-glossopharyngeal (IX)->mixed nerve, major function is to provide the sensory innervation of the pharynx and to innervate the posterior 1/3 of the tongue. its motor function is to innervate a single pharyngeal muscle and peripheral autonomic ganglion.
-vagus nerve (X)->mixed nerve, myriad sensory and motor functions that include somatic and visceral sensation, innervation of pharyngeal muscles and much of the visceral autonomic innervation.
-spinal accessory (XI) and hypoglossal (XII) subserve motor functions innervating neck and tongue muscles respectively

Question 18

Primary Sensory Neurons

Answer 18

the first neurons that receive the stimulus from the environment (touch, pain, temperature, proprioception) and send it towards the CNS (spinal cord or brainstem).

Question 19

primary sensory neurons in cranial nerves can have 2 different types of morphologies:

Answer 19

pseudounipolar (2 axons) or bipolar (one axon and one dendrite)

Question 20

most primary sensory neurons derive from?

Answer 20

neural crest cells, that derive from the dorsal region of the neural tube

Question 21

the developing pons and medulla have 8 segments called

Answer 21

rhombomeres

Question 22

how many categories of cranial nerve nuclei do we have ?

Answer 22

7
nuclei of each of these categories form discontinuous columns that extend rostrocaudally through the brain stem

Question 23

the 7 functional categories are distributed through only 6 discrete columns, why?

Answer 23

2 of the sensory categories synapse on neurons in a single column but at separate rostrocaudal locations

Question 24

where are the sensory columns disposed within respect to the motor columns?

Answer 24

sensory columns are lateral respect to the motor columns

Question 25

what does the sulcus limitans represent in the adult brain?

Answer 25

an important anatomical landmark on the floor of the 4th ventricle that roughly divides the sensory columns from the motor columns

Question 26

somatic sensations of the head, including the oral cavity, is carried by 4 cranial nerves:

Answer 26

trigeminal, glossopharyngeal, vagus and facial the trigeminal innervates most of the head and the oral cavity and is the most important one out of the 4 nerves the facial, glossopharyngeal and vagus innervates mucous membranes and organs of the body and small areas of the skin around the external ear.

Question 27

where do the sensory fibers that innervate surface skin and oral mucosa project?

Answer 27

into central trigeminal nuclei

Question 28

where do the sensory fibers that innervate the mucous membranes of the pharynx and larynx and other internal (visceral) structures project?

Answer 28

to the caudal portion of the solitary nucleus

Question 29

these sensory fibers terminate into 2 of the trigeminal sensory nuclei

Answer 29

main trigeminal sensory nucleus and spinal trigeminal nucleus

Question 30

mesencephalic trigeminal nucleus

Answer 30

third sensory nucleus not a site of termination of primary sensory fibers it is equivalent to a peripheral ganglion cause it contains the cell bodies of certain trigeminal primary sensory fibers

Question 31

the ascending second order trigeminal fibers are called

Answer 31

trigeminal lemniscus

Question 32

where in the thalamus do the ascending second order trigeminal fibers synapse?

Answer 32

in the ventral posterior medial nucleus in the thalamus

Question 33

where do the axons of the ventral posterior medial nucleus in the thalamus project?

Answer 33

to the lateral part of the primary somatic sensory cortex, in the postcentral gyrus (via the posterior limb of the internal capsule).

Question 34

from where do the secondary somatic sensory cortex and posterior parietal cortex receive their major input ?

Answer 34

from the primary somatic sensory cortex

Question 35

the dorsal trigeminothalamic tract originates from?

Answer 35

the dorsal portion of the main trigeminal sensory nucleus it ascends ipsilaterally to the ventral posterior medial nucleus and processes mechanical stimuli from the teeth and soft tissues of the oral cavity

Question 36

what is jaw proprioception

Answer 36

the conscious awareness of how much we open our mouth

Question 37

the spinal trigeminal nucleus has a rostrocaudal anatomical organization with three components:

Answer 37

1. oral nucleus 2. interpolar nucleus 3. caudal nucleus

Question 38

functions of the spinal trigeminal nucleus

Answer 38

similar to the functions of the dorsal horn of the spinal cord plays an essential role in dental and facial pain, temperature sensation and itch. a much lesser role in facial mehcanical sensations

Question 39

what is the major ascending trigeminal pathway from the spinal trigeminal nucleus?

Answer 39

the trigeminothalamic tract

Question 40

trigeminothalamic axons terminate in 3 principal locations in the thalamus:

Answer 40

1. ventral posterior medial nucleus 2. ventromedial posterior nucleus 3. medial dorsal nucleus

Question 41

where does the ventral posterior medial nucleus project?

Answer 41

to the primary somatic sensory cortex

Question 42

where does the ventral medial posterior nucleus project?

Answer 42

insular cortex

Question 43

where does the medial dorsal nucleus project?

Answer 43

the anterior cingulate gyrus

Question 44

after entering the brain stem, the central branches of glossopharyngeal and vagal axons collect in what?

Answer 44

in the solitary tract of the dorsal medulla and terminate in the surrounding caudal solitary nucleus.

Question 45

the caudal solitary nucleus is divided into 2 parts

Answer 45

a rostral portion for taste and a caudal portion that serves viscerosensory functions.

Question 46

the trigeminal nerve consists of 3 sensory roots that innervate different regions and mucous membranes of the head. name the 3 divisions

Answer 46

-ophtalmic division -maxillary division -mandibular division

Question 47

where are the cell bodies of the trigeminal sensory fibers?

Answer 47

in the trigeminal ganglion, a peripheral sensory ganglion.

Question 48

where are the cell bodies of stretch receptors found in jaw muscles located?

Answer 48

in the CNS, in the mesencephalic trigeminal nucleus

Question 49

what is the trigeminal dermatome?

Answer 49

the area of the skin of the face or head innervated by sensory fibers from a single trigeminal sensory nerve division

Question 50

the cell bodies of the sensory fibers of the facial nerve are located in?

Answer 50

the geniculate ganglion

Question 51

the cell bodies of the sensory fibers of the glossopharyngeal and vagus nerve are located in?

Answer 51

the superior ganglion of each nerve

Question 52

which is the nucleus that contains the cell bodies of stretch receptors that signal jaw muscle length (key sensory signal for jaw proprioception)?

Answer 52

mesencephalic trigeminal nucleus, located in the rostral pons and in the midbrain

Question 53

where is the spinal trigeminal nucleus located? and the main trigeminal sensory nucleus?

Answer 53

1. medulla and caudal pons 2. in the pons

Question 54

the dorsal horn extends rostrally into the medulla as?

Answer 54

spinal trigeminal nucleus

Question 55

the caudal nucleus (one of the 3 subdivisions of the spinal trigeminal nucleus) is also called?

Answer 55

medullary dorsal horn, cause very similar in structure to the spinal cord dorsal horn

Question 56

the caudal nucleus extends from where to where?

Answer 56

from the first/second cervical segment of the spinal cord till the point in the medulla where the central canal opens to form the 4th ventricle

Question 57

the inter polar nucleus extends from where to where?

Answer 57

from the rostral boundary of the caudal nucleus to the rostral medulla

Question 58

the oral nucleus extends from where to where?

Answer 58

from the rostral boundary of the inter polar nucleus till the point in which the trigeminal nerve enters the pons