Trigeminal Lecture

Question 1

What is chemesthesis?

What is an example of this?

Answer 1

The idea that free nerve endings can have a chemical sensitivity
An example of this would be eating something spicy or minty

Question 2

What sensations is the trigeminal nerve responsible for?

Answer 2

Pain
Touch
Temperature
Proprioception

Question 3

What is stereognosis?

Answer 3

The 3 dimensionality of something- size, texture, hardness

Question 4

What is Flavour?

Answer 4

Taste, olfaction, texture, temperature, and chemesthesis

Question 5

What are the three branches of the trigeminal nerve and what do they each contain?

Answer 5

Ophthalmic- sensory
Maxillary- sensory
Mandibular- sensory and motor

Question 6

What are 2 other names for the trigeminal ganglion?

Answer 6

Gasserian ganglion

Semilunar ganglion

Question 7

The afferent pathway of the trigeminal ganglion that is responsible for mostly touch end s on which nucleus in the brain?

Answer 7

The principal (main or chief) sensory nucleus

Question 8

The spinal trigeminal nucleus has three parts- oralis, interpolaris, and caudalis. What generally is found in each?

Answer 8

Oralis- mostly touch
Interpolaris- temperature and touch
Caudalis- pain

Question 9

A-beta fibers are responsible for what time of perception?

Answer 9

Touch

Proprioception

Question 10

A-delta fibers are responsible for what type of perception?

Answer 10

Touch
Temperature
Chemesthesis
Sharp pain

Question 11

C fibers are responsible for what type of perception?

Answer 11

Temperature
Chemesthesis
Dull and burning pain

Question 12

Meisnner corpuscles measure what?

Answer 12

Light touch/spatial discrimination

Question 13

Merkel receptors measure what?

Answer 13

Pressure

Question 14

Ruffini corpuscles measure what?

Answer 14

Skin strethc

Question 15

Pacinian corpuscles measure what?

Answer 15

Vibration

Question 16

The response properties of mechanoreceptors are influence by several sources. What are they? (3)

Answer 16

Degree of myelination
The location of the receptor (superficial or deep)
The structure of the nerve ending (Meissner, Ruffini etc)

Question 17

What happens with stretch or mechanical contact?

Answer 17

Cation channels open

Question 18

What are the three mechanisms of mechanotransduction?

Answer 18

ENaC (epithelial Na+ channels)
TRP channels (transient receptor potentials)
Piezo1 and Piezo2

Question 19

How are Merkel cells activated?

Answer 19

1. Pressure sensitive transduction by Piezo2 leads to depolarization
2. Voltage gated Ca++ channels open
3. Neurotransmitter released into synaptic cleft (glutamate)
4. Postsynaptic response leads to action potentials

Question 20

Is there a synapse involved Merkel cell activation?

Answer 20

Yes

Question 21

Is there a synapse involved in Pacinian corpuscle activation?

Answer 21

No- it’s right on the nerve ending

Question 22

Pacinian corpuscles- how do they work?

Answer 22

The nerve ending is surrounded by lamellae. These lamella, when compressed, only allow the initial impact of the stimulus to make it to the transduction site. When the force is removed, the compressed part of the lamellae give and off-response to the receptor resulting in the vibratory sensation.

Question 23

What are Von Frey Hairs?

Answer 23

They are instruments that measure touch discrimination using a monofilament that is weighted to bend at a specific pressure.

Question 24

T/F the lateral part of your face has a lower threshold for two-point discrimination than the midline of your face?

Answer 24

False! Two point discrimination is achieved far more easily in the midline (specifically the lips) than on the lateral part of your face.

Question 25

In the face, are there Pacinian corpuscles present? What does this mean?

Answer 25

Nope | Our face is not designed to detect vibration

Question 26

T/F the tip of the tongue is the highest area of sensitivity of the tongue?

Answer 26

True

Question 27

T/F the tongue has both rapidly and slowly adapting mechanoreceptors despite having one kind of ending?

Answer 27

True

Question 28

T/F Rapidly adapting receptors have an on/off type of response compared to slowly adapting receptors which seem to taper off?

Answer 28

True

Question 29

What are the receptor endings found in the tongue called?

Answer 29

Krause end bulbs

Question 30

TMJ mechanoreceptors are innervated by what?

Answer 30

The mandibular branch of the trigeminal nerve

Question 31

T/F, you anterior teeth are more sensitive (in PDL) than your posterior teeth?

Answer 31

Truth

Question 32

T/F the periodontal ligament mechanoreceptor is rate sensitive- i.e. fewer action potentials form as the stimulus is applied more slowly?

Answer 32

Truuuth!

Question 33

PDL mechanoreceptors have _______ sensitivity. Give an example.

Answer 33

Directional | i.e. more sensitive to labial and distal force than lingual or mesial force

Question 34

Denture and implant patients have trouble controlling their biting force (if asked to hold something like a peanut between their teeth without breaking it) because why?

Answer 34

Because they have no periodontal ligament and thats where the information comes from to do that correctly.

Question 35

Are PDL mechanoreceptors helpful with stereognosis?

Answer 35

Absolutley- they help you feel what the shape of something is in your mouth

Question 36

For warm stimuli, which part of mouth is most sensitive?

Answer 36

The tip of the tongue

Question 37

Temperature transduction is mediated by what type of channels?

Answer 37

TRP channels