oral physio script 4

8/2/2019 oral physio script 4

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ORAL PHYSIOLOGY 6/3/2012 |GENERAL SENSATION IN THE ORAL CAVITY

This lecture related to topic physiology of pulp & dental pain.

Oral mucosal sensations

1. Touch2. Pressure3. Temperature4. Pain5. Stereogenesis

a. Define - ability to detect the shape of objects.b. Example:

i. if we put a pin, we can feel the shape of piece of metal.ii. A dentist apply pressure on the mouth to see the tonsils, he put in a wooden instrument ,you

can feel of that instrument. So we can response to many different stimuli inside the mouth.

6. Proprioception Kinesthesiaa. Sense of movement & position of limbs & other body parts.b. Ex: I move my mandible up & down, my brain is aware that I am moving the mandible. Brain

helps in the precise movement open & close of the mouth (including the exact contact of lower &

upper teeth).When I ask anyone to open his mouth and after that closing it, unconsciously, he will beable to close up exactly, or he will be able to put the lower teeth exactly in their position against the

upper teeth .How that you do that? We have receptors that telling the brain that the mandible now is

moving and is moving into the right position until the teeth coming into contact, this is the

proprioception.

c. Without proprioception, we cannot put the lower teeth against the upper teeth appropriately.i. Periodontal ligament of lower teeth contain the proprioceptor for carrying/conveying

proprioception. People without teeth, means no periodontal ligament are unable to put the

lower exactly against the upper jaw.

d. Muscle spindles inside the musclei. role: sending information to the brain about the position of different part of the body.

7. Special sensation taste that exist in the mouth. Sweet, bitter, acid & salt.

Touch & pressure

A & A fibers (group II & III sensory neurons)- not the nociceptor. The cell bodies located in trigeminal ganglion. Secondary neurons convey signals to the other side of the brainstem. Then to thalamus & cerebral cortex. (remember that area responsible for receiving the information from the

right side is locating at the left side of the brain)(cross midline)


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Area of mouth on somatosensory cortex

(hint to understand the drawing: A large area means higher degree of sensitivity)

Here we have the red line, this is called the Central Groove. Anterior to the central groove, this

is called Pre-central Gyrus and posterior to the groove is called Post-central Gyrus.

Now, the area of the mouth on the somatosensory cortex is located at the lower part of the

post-central Gyrus. This is the area responsible for the sensation inside your mouth. What about

the pre-cental gyrus? It is important for the motor function of your mouth.

Here, we have something really funny, they drew a human being, but this human being looks very

disproportionate.

For example, see the

faceits very huge the hand is very big the leg is very small the trunk very small Why did they sketch of human being which is very disproportionate? Because they want to

reflex the important of the different area of your body on somatosensory cortex.


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Postcentralgyrus - somatosensory

Based on pictures: coronal section of precentralgyrus.The drawing reflect the important of different

area of the body in somatosecsory.

The eye is small, so the size of the eye in post-central gyrus is small.

Logically which is more important, hand or foot?Of coursehand because its very important in

touch. Thats why the size of the hand is much bigger than the foot.

The hand is not proportional because the size of the thumb is big but the size for others finger are

smaller. Why? Because the thumb is very important in sensation.

Notice that the foot is much bigger than the leg. (this is not important)

The most important for us is the area ofFACE, face is located at the lower part of post-central gyrus and notice that the biggest proportion is for the lips. The lower part of the

face is more important than the upper part of the face.

The TONGUE also occupied the huge area, why? Because your tongue is very important inperceiving sensation.

then the UPPER LIP AND LOWER LIP, because the lips contain too many nerves, so that whyyoull see the huge amount of information from your upper and lower lips, and thats why

the occupy a big area in the brain.

(look at the somatosensary cortex) remember all what we discuss.

Precentralgyrus- motor function of the body.

Important for motor function of the mouth.Based on pictures: coronal section of precentral gyrus.

Yellow (pre-central gyrus): this is responsible for the motor function in your body.

Motor fuction related to the HAND is really huge. Why?Because our hand is very importantfor writing, drawing and many different utility.

Face, the MOUTH is big, because the movement of mandible and the movement of differentmuscle related to mouth are very delicate and very detail. Thats why we need the big area

to be responsible on sending information to the muscle to all of this movement.

The TONGUE all the time is located at lower most area of the somatosensory cortex and alsothe motor cortex.

Q: the lowest area in the postcentralgyrus is related to? Ans: the face Q: the biggest area of the face that response to sensory inervation? Ans: upper &

lower lips/tongue


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Temperature sensation

Ranking of sensitivity

1. Palate(most sensitive)2. Lips3. Tongue(less sensitive)

Oral mucosa is very sensitive to hot & cold This high sensitivity is a protective mechanism

o brain should be able to response to something harm(extreme cold/hot) to avoid harming ourselves.o Ex: we able to avoid burn ourselves when drink hot water by stopping drink that hot water.

Receptors - that responsible for temperature sensationo Bare nerve endings - have no capsule at the end of the nerveo Respond to temps > threshold (hot) & < threshold (cold)

Usually threshold for cold is higher but the threshold for hot is lower. So, with slightly hot,we will be able to say that it is hot. But vice versa to cold.

The threshold for hot is low.o Receptors threshold for skin or lip is the temp of skin (25C).o Intraoral receptors have higher thresholds.

We can withstand higher temperature inside the mouth compared to the skin. Fibers are A & C fibers

o (sensory groups III & IV) but they are different to the pain nerve(nociceptor)o It is slow transmittingo In brain - no separate pathway to cortex for temp & pain sensation

Inside brain, we have common pathway for pain & temperature. (Gate Control theory) Repetitive temperature over a long time will inhibit transmission of

pain.

Ex: if we repeat temp sensation in one area over a long period of time, this will inhibittransmission of pain at another area. (Gate Control theory)

o In Spinal cord separate pathway exists, but when the nerve proceed to center, it will have commonpathway.

o Impulses reach thalamus through trigeminothalamic tract (trigeminal laminscus)*not to remember Max. tolerable temp in mouth = 70 80C

o More than this limit will burn the mouth.o Lips cannot detect temperature but pain instead due to tissue damage.

Postcentralgyrus Precentralgyrus

1. Face- biga. located at the lower part of

postcentralgyrus.

2. Lips-biga. contain many nerves to

receive huge amount of

information.

3. Moutha. is located at lower part of

postcentralgyrus.

4. Tongue-biga. Tongueis important in

perceiving many sensation.

5. Eye-small6. The hand(bigger in drawing) VS The

foot(smaller in drawing)

a. hand is more important intouch.

b. size of the thumb bigger.

a. Face-bigb. Mouth-big

i. Movement of muscle relatedto mandible is very

detail/delicate.

c. Tongueii. Is always located at the

lower part of the motor &

somatosensory.

d. Hand(big) VS Leg(small)iii. Hand is very important for

many actions

Neck-small


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o Lips are very sensitive to temperature. Tongue less sensitive than lips

o Tongue can withstand the hot temperature on tongue but lips cannot. Palate may blister at lower temps

o Palate is extremely sensitive. When we drink hot water, palate is the 1 st to burn.(remember thesequence ranking for sensitivity)

Hot stimuli on tongue lead to tissue damage which lead to stimulation of cold & warmth receptorso This is not reported elsewhere in the body.o Tongue can withstand high temperature. Even after tissue damage at the tongue, we still feel

temperature.

o Usually(at other part of body) if we have tissue damage, we will feel pain. But, at tongue particularly,even after tissue damage, instead of feeling pain, we still feel temperature. When the temperature is

extremely high, then it will stimulate the nociceptor.

Pain is the only sensation detected in teetho Evidence that heat may be discriminated

The sensation that detected by the teeth is ONLY PAIN.Pressure sensation

Teeth are sensitive to pressure applied axially or laterallyo The pressure will stimulate the receptors in periodontal ligamento Most sensitive- apex of the tooth.

Receptorso End-organs of the Ruffini type (just know that they are only mechanoreceptor)

A class of slowly adaptingmechanoreceptorthought to exist only in theglabrous dermisandsubcutaneous tissueof humans.

o Nerve fibers are Ao Response vary according to position with PDLo Usually the most sensitive is at the apex of the tooth.

because when we make axial movement, the one that respond first are the apical fibers. Mean, the periondontal ligament responses are not at the same rate.

Teeth respond as if they have axis of rotation between middle & apical 1/3s of rooto If apply : axial movement-tooth move axial slightly axially.o If apply : lateral movement-the tooth will rotate.

We have to imagine that the fulcrum of rotation located between apical 1/3 of the root andmiddle 1/3 of the root.

o Receptors near axis of rotation adapt rapidlyo Receptors furthest away adapt slowly

Proprioception

proprioception is the ability to feel the position of the different body part in relation to each other. Impulses(information of position of the muscle) from

o Muscles of the tongueo

Muscles of masticationo Temporomandibular joint

To tell the brain about the position of mandible. Muscles containing muscle spindles

o Tongue muscleso Mandibular elevators-temporalis,masseter, med.ptrygoid.

Cell bodies of fibers are located in specialized nucleus:o mesencephalic nucleus of trigeminal nerve- responsible for proprioception.o motor nucleus of trigeminal nerve- responsible for motor function associated with trigeminal nerve.

Trigeminal nerve inside the midbrain has many nuclei.

The one that responsible for sensory are called nucleus

of trigeminal nerve.
http://en.wikipedia.org/wiki/Mechanoreceptorhttp://en.wikipedia.org/wiki/Mechanoreceptorhttp://en.wikipedia.org/wiki/Mechanoreceptorhttp://en.wikipedia.org/wiki/Glabrous_dermishttp://en.wikipedia.org/wiki/Glabrous_dermishttp://en.wikipedia.org/wiki/Glabrous_dermishttp://en.wikipedia.org/wiki/Subcutaneous_tissuehttp://en.wikipedia.org/wiki/Subcutaneous_tissuehttp://en.wikipedia.org/wiki/Subcutaneous_tissuehttp://en.wikipedia.org/wiki/Glabrous_dermishttp://en.wikipedia.org/wiki/Mechanoreceptor


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Taste

Special sensation Considered as chemoreception (because we respond to chemical that are found in the food) perceived directly

in the cortex

o We detect chemical in the food.o It is parasympathetic.o Travel with branches of trigeminal nerve.

Receptors are only in the head region (cannot taste outside head), we can taste through:o Dorsum of the tongueo Soft palateo Epiglottis Have taste buds that respond to different chemicalo Pharyngeal wallo Esophagus

Significant of tasteo Taste is the main stimulant to saliva flow. When we taste something, our saliva is secreted.o Governs the use of oral hygiene aids like toothpaste.

Manufacturer put mint in the toothpaste so that it is accepted by users.o Governs food choice sweet cariogenico When we have good taste, we eat more and become fatter. : )o Tongue can withstand high temperature. Even after tissue damage at the tongue, we still feel

temperature. This is specific for tongue only.

o Not reported elsewhere in the body. At other part, pain is detected by nociceptor as pain. Pain is the only sensation detected in teeth

o Evidence that heat may be discriminatedTaste buds

Taste buds are specialized cells located in different areas inside the mouth. They are the area that perceive the chemicals present in that taste material and send impulses to the

brain.

Each bud is a group of taste receptors.

Develop early in fetal lifeo Ex: taste buds on the circumvallate papillae form by 14 weeks in utero

Taste buds have different type of cells: type I, II, III, IVTaste buds on the tongueTongue is derived from 2 branchial arches

1. Anterior 2/3 from 1st branchial arch Ant 2/3 taste buds of the tongue is provided by facial nerve through chorda tympani

TYPES OF PAPILLAE

Filiform white hair-like projections, rarely have taste buds/no taste buds Fungiform have taste buds on their top surface Foliate

o Buds are on lateral walls of their ridgeso Too many ~ 1500 buds

the doctor was explaining the figure on the TASTE BUDS slide: this is taste pore where

material of the food acts here and then it triggers these cells and these cells function in

carrying the impulse of taste to the brain


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Circumvallateo Location: They are situated on the dorsum of the tongue anterior of the sulcus terminaliso Number of buds

250 300 buds on each of 10 12 papillae Decrease with age old people tend to have decreased of taste sensitivity

o Von Ebners glands - specialized minor salivary gland associated with circumvallatepapillae : to wash out the previous taste and to make the area ready for new taste.

2. Posterior 1/3 from 3rd branchial archImportant note: 2

ndbranchial arch only provides taste buds to the tongue. So, the taste buds of the anterior

2/3 of tongue are supplied by facial nerve via chorda tympani.

Regional distribution of different taste sensations

Types of taste perceptiono Salt facial nerveo Sweet facial nerveo Acid facial nerveo Bitter buds in glossopharyngeal innervation area (cranial nerve IX)

Taste buds responsible for bitter taste located at the circumvallate papillae, foliatepapillae, pharynx & epiglottis.

Dorsum of tongue is more sensitive to acid & bitter taste Old people complain of decrease in taste sensation because of many things

o Bitter taste is not affected (meaning that old people complain about losing their tastesensation but they still CAN taste bitter)

o Losing taste sensation is not related to decreased population of buds on circumvallatepapillae

o In denture wearers palate is covered.o So, they found that old people cover their palate with denture (prosthesis ya3ni), so the

taste buds in the palate is covered by the denture resulting in no sensation on the palate.

By: IKMAL, SYADI, FUAD, SUHAIDI, IZHAM

through the chorda tympani branch & usually

located on the anterior 2/3 of the tongue

Wikipedia: circumvallate papillae are situated on the

dorsum of the tongue immediately in front of the foramen

cecum and sulcus terminalis, forming a row on either side;

the two rows run backward and medially, and meet in the

We said that when we increase in age, the numbers of the taste buds

on the circumvallate papillae decrease. But still we find that these old

people do not suffer decrease in bitter taste. So, they are not related

to the decrease in number of the taste buds on the circumvallate

papillae. They found that these people they cover their palate the

alate with their dentures. Because of that the taste sensation

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oral physio script 4