Physiology of pain

Good morningwww.indiandentalacademy.com

PHYSIOLOGY OF PAIN,
SYMPATHETIC AND PARA
SYMPATHETIC MOTOR NERVOUS
SYSTEM
AND NEUROMUSCULAR CO-
ORDINATION OF
STOMATOGNATHIC SYSTEM
www.indiandentalacademy.com

Contents
Physiology of pain
•Types of pain
•Pain receptors
•Pain pathways
•Pain suppression system
•Referred pain
Sympathetic and parasympathetic nervous systems
•Physiologic anatomy
•Basic characteristics
•Neurotransmitters and receptors
•Effect on different organs
Neuromuscular coordination of stomatognathic
system
•Neuromuscular structures and function
•Mastication ,Swallowing, Speech
•Protective mechanisms like sneezing, coughing

Introduction

Muscles of mastication :Muscles of mastication :Muscles of mastication :
Pain:
An unpleasant sensation associated
with actual or potential tissue damage,
and mediated by specific nerve fibers to
the brain where its conscious
appreciation may be modified by various
factors.

Types of pain and their qualities :
Pain has been classified into 2 major types :
1)Fast pain 2) Slow pain
- Fast pain -Sharp pain, pricking pain, acute pain
and electric pain.
- Fast, sharp pain is not felt in most of the deeper
tissues of the body.
- Slow pain - burning pain, aching pain, throbbing
pain, nauseous pain and chronic pain. This type of
pain is associated with tissue destruction.

Pain receptors and their stimulation :
 Are all free nerve endings.
Distribution of pain endings.
 3 types of stimuli excite pain receptors
Mechanical
Thermal
Chemical e.g. bradykinin, serotonin,
histamine, K+ ions, acids, ACh,
proteolytic enzymes. Prostaglandins and
substance P enhance the stimulus.
 Fast pain is elicited by the mechanical and
thermal types of stimulus whereas slow pain can
be elicited by all three types.www.indiandentalacademy.com

Non adapting nature of pain receptors .
Hyperalgesia
Tissue damage as a stimulus of pain.
Rate of tissue damage.
Tissue ischemia as a cause of pain.
Accumulation of large amounts of
lactic acid in the tissues formed as a
consequence of anaerobic metabolism is
the cause of pain during ischemia.
Bradykinin and proteolytic enzymes.www.indiandentalacademy.com

Muscle spasm as a cause of pain
•Direct effect of muscle spasm in
stimulating mechanosensitive pain
receptors may cause pain.
•It also possibly results from indirect effect
of muscle spasm to compress the blood
vessels and cause ischemia.

Dual transmission of pain signals into CNS
The two pathways of the two types of pain are :
Fast sharp pain pathway
Slow chronic pain pathway.
The fast sharp pain signals are elicited by either
mechanical or thermal pain stimuli; they are
transmitted in the peripheral nerves to the spinal cord
by small type A δ fibers at velocities between 6 and 30
m/sec.
The slow chronic pain is mostly elicited by chemical
types of pain but also by persisting mechanical or
thermal stimuli; this pain is transmitted by type C fibers
at velocities between 0.5 and 2 m/sec.

There are 2 systems for processing the pain
signals on their way to the brain :
1) The neospinothalamic tract for fast pain.
2)The paleospinothalamic tract for slow pain.

i) Neospinothalamic tract
 The fast type A δ pain fibers terminate
mainly in lamina I of dorsal horns and
there excite second order neurons of
neospinothalamic tract.
 It is believed that glutamate is the
neurotransmitter substance secreted in
the spinal cord at the type of A δ pain
nerve fiber endings.www.indiandentalacademy.com

ii) Paleospinothalamic pathway for transmitting slow
chronic pain
The peripheral fibers (type C pain fibers) terminate
almost entirely in laminae II and III of the dorsal horns
which together are called substantia gelatinosa.
Substance P
•Glutamate transmitter acts instantaneously and lasts
for only few milliseconds.
•Substance P is released much more slowly, building up in
concentration over a period of seconds or even minutes.
•“Double” pain sensation

•The slow chronic
paleospinothalamic pathway
terminates widely in the brain
stem.
1/10th to 1/4th of the fibers
pass all the way to the
thalamus.
Others terminates
principally in one of three
areas :
•The reticular nuclei
•Tectal area
•The periaqueductal
gray region

Pain suppression (Analgesia)
system :
The analgesia system consists
of 3 major components :
•The periaqueductal gray and
periventricular areas of the
mesencephalon and upper pons.
•The raphe magnus nucleus, a thin
midline nucleus located in lower pons
and the nucleus reticularis
paragingantocellualris located laterally
in medulla.
•Pain inhibitory complex located in the dorsal
horns of the spinal cord.

Transmitter substances are involved in the
analgesia system; especially are enkephalins
and serotonin.
Periventricular nuclei and periaqueductal gray
area secrete enkephalins at their endings.
Raphe magnus nucleus release enkephalin.
The fibers originating in the nucleus and then
terminating in the dorsal horns of the spinal cord
secrete serotonin.

The brain’s opiate system – the endorphins
and enkephalins :
About a dozen of opiate like substances have
been found in different points of the nervous
system ; all are broken down products of three
large protein molecules :
•Pro opiomelanocortin
•Proenkephalin
•Prodynorphin
Among the most important of the opiate
substances are β-endorphin, met-enkephalin, leu-
enkephalin and dynorphin.www.indiandentalacademy.com

Inhibition of pain transmission by tactile
sensory signals :
Stimulation of large type Aβ sensory
fibers from the peripheral tactile receptors
can depress the transmission of pain
signals.
Referred pain :
Often a person feels pain in a part of his
or her body that is considerably remote
from the tissue causing the pain. This
pain is called referred pain.

The autonomic nervous system :
The portion of the nervous system that controls
most visceral functions of the body is called the
autonomic nervous system.
The system helps to control arterial pressure,
gastrointestinal motility, gastrointestinal secretion,
urinary bladder emptying, sweating, body
temperature and many other activities.
The efferent autonomic signals are transmitted to
the various organs of the body through two major
subdivisions called the sympathetic and
parasympathetic nervous system.www.indiandentalacademy.com

Sympathetic nervous system :
The sympathetic nerve fibers originate in the
spinal cord between cord segments T-1 and L-2
and pass first into sympathetic chain and then
into tissues and organs.
Celiac and hypogastric ganglia.
Preganglionic and postganglionic neurons.
The cell body of preganglionic neuron lies in the
intermediolateral horn of the spinal cord.

Segmental distribution of sympathetic nerves
T – 1  Pass up the sympathetic chain to head.
T – 2  Neck
T – 3, 4, 5, 6  Thorax
T – 7, 8, 9, 10, 11  Abdomen
T – 12, L-1, L-2  Legs
Special nature of the sympathetic nerve ending in
adrenal medulla :
Preganglionic sympathetic nerve fibers pass,
without synapsing, all the way from the spinal
cord, through the sympathetic chains, then
through splanchnic nerves and finally into the two
adrenal medullae.www.indiandentalacademy.com

Parasympathetic nervous system –
physiologic anatomy :
Parasympathetic fibers leave the central NS through
cranial nerves III, VII, IX and X and additional
parasympathetic fibers leave the lowermost part of the
spinal cord through the second and 3rd sacral spinal
nerves.
About 75% of all parasympathetic nerve fibers are in
vagus nerves.
Vagus nerves supply parasympathetic nerves to the
heart, lungs, esophagus, stomach, entire small
intestine, proximal half of the colon, liver, gall bladder,
pancreas and upper portions of the ureters.

Parasympathetic fibers from the 3rd cranial
nerve go to the papillary sphincters and ciliary
muscles of the eye.
Fibers from 7th cranial nerve pass to the
lacrimal, nasal and submandibular glands.
9th cranial nerve – to the parotid gland.
Preganglionic and postganglionic neurons.

Basic characteristics of sympathetic and
parasympathetic function :
Cholinergic and adrenergic fibers :
•Fibers that secrete ACh – Cholenergic
•Fibers that secrete nor epinephrine (adrenaline) –
Adrenergic
•All pre ganglionic neurons are cholinergic in both the
sympathetic and parasympathetic nervous systems.
•Either all or almost all of the postganglionic neurons of
parasympathetic system are cholenergic.
•Most of the postganglionic sympathetic neurons are
adrenergic.

Mechanisms of transmitter secretion
Some of the parasympathetic nerve fibers and almost
all the sympathetic fibers touch or pass over or near the
cells to be stimulated. These fibers here have bulbous
enlargements called varicosities.
Varicosities contain secretary vesicles of
neurotransmitters.

Synthesis of Ach, its destruction after secretion and duration of action:
Choline acetyl
transferase
Most of the synthesis of Ach occurs in the
axoplasm outside the vesicles.
Choline acetyl transferase
Acetyl – Co.A + choline------- Acetylocholine
The most of the ACh is split into an acetate ion
and choline catalysed by the enzyme
acetylcholinesterase.
Synthesis of Ach, its destruction after
secretion :

Synthesis of norepinephrine, its removal and
duration of action :
-Synthesis of nor epinephrine begins in the axoplasm of
the terminal nerve endings of adrenergic nerve fibers but
is completed inside the secretary vesicles.
The basic steps are the following :
Hydroxylation
•Tyrosine --------- Dopa
Decarboxylation
•Dopa --------- Dopamine
•Transport of dopamine into the vesicles
Hydroxylation-
Dopamine -------- Norepinephrine

In adrenal medulla, this reaction goes as (about 80%)
Methylation
Norepinephrine ---------- Epinephrine
Removal
Norepinephrine secreted directly into a tissue remains
active for only few seconds.
Norepinephrine and epinephrine secreted into the blood
by adrenal medullae remain active for 10-30 seconds; their
activity declines over 1 to several minutes.

Receptors for neurotransmitters :
Acetylcholine receptors :
There are 2 main types of receptors :
Muscarinic
Nitotinic
Muscarinic receptors are found on all effector cells
stimulated by the post ganglionic neurons of the
parasympathetic and sympathetic nervous system.
Nicotinic receptors are found at the synapses
between the preganglionic and post ganglionic
neurons of both the sympathetic and
parasympathetic systems.

Adrenergic receptors
Two types – alpha and beta receptors.
Beta receptors are inturn divided into β1 and
β2.
Norepinephrine excites mainly alpha
receptors but excites the β receptors to lesser
extent.
Epinephrine excites both types of receptors
approximately equally.
Isopropyl norepinephrine –beta receptors.

-Adrenergic receptors and function :
Alpha receptor Beta receptor
Vasoconstriction Vasodilatation (β2)
Iris dilatation Cardioacceleration (β1)
Intestinal relaxation Increase myocardial strength
(β1)
Intestinal sphincter
contraction
Intestinal relaxation (β2)
Pilomotor contraction Uterus relaxation (β2)
Bladder sphincter contraction Calorigenesis (β2)
Glycogenolysis (β2)
Lipolysis (β1)
Bladder wall relaxation (β2)

Sympathetic stimulation has also multiple metabolic
effects such as glucose release from liver, increase in
blood glucose concentration, increase in glycogenolysis
in both liver and muscle, increase in skeletal muscle
strength, increase in basal metabolic rate and increase in
mental activity.
Value of the adrenal medullae to the function of the
sympathetic nervous system.
The organs are actually stimulated in the two ways
simultaneously : direct by sympathetic nerves and
indirectly by the medullary harmones.

Mass stimulation by the sympathetic and
parasympathetic systems
In some instances, almost all portions of the
sympathetic nervous system discharge simultaneously
as a complete unit, a phenomenon called mass
discharge.
This frequently occurs when the hypothalamus is
activated by fright or fear or severe pain.

“Alarm” or “Stress” response of sympathetic
nervous system :
Mass discharge increases in many ways the ability of
the body to perform vigorous muscle activity :
•Increase arterial pressure.
•Increase blood flow to active muscles concurrent
with decreased blood flow to organs, that are not
needed for rapid motor activity like GIT, kidneys.
•Increase rates of cellular metabolism throughout the
body.
•Increase blood glucose concentration,
glycogenolysis.
•Increase muscle strength, mental activity.
•Increase rate of blood coagulation.

Neuromuscular coordination of
stomatognathic system
Neuromuscular system is divided into two major
components :
The neurologic structures
The muscles
Muscles :
The motor unit :
The basic component of the neuromuscular system
is the motor unit, which consists of a number of
muscle fibers that are innervated by one motor
neuron.

Each neuron joins with the muscle fiber at a motor
endplate.
The inferior lateral pterygoid muscle has a
relatively low muscle fiber / motor neuron ratio.
Masseter www.indiandentalacademy.com

Masseter :
Muscles of mastication :
 Contraction elevates mandible.
 Superficial portion may also aid in protruding the
mandible.
 When the mandible is protruded and biting force
is applied, the fibers of the deep portion stabilize
the condyle against the articular eminence.

Temporalis :
Contraction elevates the mandible
When anterior portion contracts, the mandible is raised
vertically.
Contraction of middle portion will elevate and retrude the
mandible.
Posterior portion may retrude the mandible.www.indiandentalacademy.com

Medial pterygoid :
Contraction elevates the mandible
This muscle is also active in protruding the mandible.
Lateral pterygoid :
Has 2 distinct portions
1) Inferior 2) superior

Inferior lateral pterygoid :
When right and left inferior lateral pterygoids contract
simultaneously, the condyles are pulled down the
articular eminences and the mandible is protruded.
Unilateral contraction
Superior lateral pterygoid :
Becomes active in conjunction with the elevator
muscles. It is especially active during the power stroke
and when the teeth are held together.

Digastricus :
Although it is not considered a muscle of mastication, it
has an important influence on the function of the
mandible.
When right and left digastric contract and the suprahyoid
and infrahyoid muscles fix the hyoid bone, the mandible is
depressed and pulled backward and teeth are brought out
of contact.
When mandible is stabilized, the digastric muscles with
the suprahyoid and infrahyoid muscles elevate the hyoid
bone, which is necessary function for swallowing.

Neurologic structures :
Brainstem :
Rhombencephalon+mesencehalon

Spinal tract nucleus :
The brainstem trigeminal – nucleus complex
consists of 2 main parts.
 Main sensory trigeminal nucleus.
 Spinal tract of trigeminal nucleus.
Spinal tract nucleus further divided into :
Subnucleus oralis
Subnucleus interpolaris
Subnucleus caudalis.

Reticular formation :
After the primary afferent neurons synapse in the
spinal tract nucleus, the internueurons transmit the
impulses up to the higher centers.
The interneurons ascend by way of several tracts
passing through an area of the brainstem called the
reticular formation.

Thalamus
Thalamus acts as a relay station for most of the
communication between the brainstem,
cerebellum and cerebrum.

Hypothalamus :
Is the major center of the brain for controlling internal
body functions such as body temperature, hunger and
thirst.
Stimulation of hypothalamus excites sympathetic
nervous system.

Limbic structures :
Function to control our emotional and behavioural
activities.
Within limbic structures are centers, or nuclei that are
responsible for specific behaviors such as anger, rage,
docility.
Cortex :
 Associated with thinking process.
 Portion of brain in which essentially all of our memories
are stored.
 It is also the area most responsible for our ability to
acquire our many muscle skills.

SENSORY RECEPTORS :
Masticatory system uses four major types of sensory
receptors to monitor the status of its structures :
1)Muscle spindle
2)Golgi tendon
organs

3)Pacinian corpuscles 4)Nociceptors

Neuromuscular function :
Reflex action :
A reflex action is the response resulting from a
stimulus that passes as an impulse along an afferent
neuron to a posterior nerve root or its cranial
equivalent.

Myotatic reflex :
Myotatic or stretch reflex is the only monosynaptic
jaw reflex. When a skeletal muscle is quickly stretched,
this protective reflex is elicited and brings about a
contraction of the stretched muscle.
Nociceptive reflex :
The nociceptive or flexor reflex is a polysynaptic
reflex to noxious stimuli and therefore is considered to be
protective.

Mastication :
Is defined as the act of chewing foods.
There are several general classes movements which are
controlled in different ways.
a) Voluntary movements
b) Movements that purely reflex
c) Cyclical movements : eg. chewing

Central pattern generator :
There are a number of structures in the central
nervous system which interact in a rather complex
manner to produce rhythmical activation of jaw
opening muscles alternating with the activation of
jaw closing muscles.
Reflexes automatically fine tune the centrally
generated masticatory movements to give the best
possible control of position and force.

Control of mandibular rest position :
The vertical position of the mandible is maintained
in its postural position by visco elastic forces when the
head is stationary or moving only slowly, but by stretch
reflexes when the head is moving more vigorously up and
down during running and jumping.
Mechanisms that modulate jaw muscle activity during
chewing:
The most important signals that help the chewing
muscles to adapt to different types of food, and the
changing texture of food as it is chewed come from
muscle spindle receptors and from mechanoreceptors in
the periodontal ligament.

Unloading responses of the jaw closing muscles:
It is equally or even more important for the jaw
muscles to stop contracting when the resistance to
closing suddenly decreases. There are 2 reasons for this.
Periodontal reflexes :
Two different periodontal reflexes are been
described.
• Firstly, brisk taps on a tooth elicit rapid and
profound inhibition of activity in the jaw closing muscles.
• Secondly, pressing weakly on a tooth activates a
different population of receptors in the periodontal
ligament.
Weak pressure reflexly excites the jaw closing motor
neurons and therefore increase the biting force.www.indiandentalacademy.com

Tendon organ reflexes :
Masticatory muscles contain other sensory
receptors which are known as golgi tendon organs
that give a signal that is related to the force exerted
by the muscle.
Joint reflexes :
Receptors in the capsule of the TMJ may refelxly
activate motor neurons of the muscles whose actions
oppose excessive jaw opening movements that
threaten to dislocate the joint.
Painful stimuli in the TMJ area activate nociceptors
which in turn cause strong coactivation of the jaw
opening and closing muscles.www.indiandentalacademy.com

The chewing cycle :
In chewing, the pattern generator programs the
following phases.
1)Preparatory phase : the jaw may initially move away from
its working side as it begins to open, but then swings
towards the working side.
2)Food contact phase : as the generator switches off the
activation of the jaw opening muscles, it almost
immediately switches on the activity of jaw closing
muscles to produce the initial closing movement (at abt
10cm/s).

3)Food crushing phase : in this phase, the output
from the pattern generator to the closing muscles
forces the teeth through the food bolus with the
assistance of the muscle spindle reflex system.
4)Tooth contact phase : during this phase, the
outputs from the periodontal ligament receptors
reflexly control the jaw closing muscles to ensure that
the teeth slide in correct direction towards intercuspal
position.
A bilateral chewing pattern in denture wearers.

Bite forces during normal mastication in denture
wearers:
The maximal bite force of subjects who have lost all of
their natural teeth is decreased by about 50%, even when
they wear well fitted full dentures.
Chewing efficiency is also substantially diminished with
denture wearers usually requiring 3-6 times the number of
chewing strokes to break down a given food load.
Role of tongue in mastication :
Position of the tongue during chewing is highly
coordinated with the activity of the masticatory muscles. It
is through linked control of the motor nerves to the intrinsic
and extrinsic tongue muscles from the masticatory pattern
generator.

SWALLOWING :
The highly coordinated swallowing response
seals the back of the nose and the entrance to the
trachea to prevent the entry of foreign bodies into
these vulnerable areas.
25 pairs of skeletal muscles.
Swallowing can be initiated by
Sensory signals
↓
Superior laryngeal nerve
↓
Nucleus of solitary tractwww.indiandentalacademy.com

Despite its complexity, swallowing can be
considered to be a reflex response, because the
appropriate stimulus will cause it to occur in a
highly stereotyped manner.
Swallowing frequency – 600 times during a 24
hour period.
Because the events that comprise swallowing are
so complex, it is usual to consider this integrated
response as a series of over lapping phases.

The phases of swallowing include :
(1) Oral preparatory phase :
In this stage the food is chewed and mixed
with saliva to form a moist, cohesive bolus ready
to be swallowed.
Swallows are integrated with normal rhythmic
chewing movements.
To stabilize the mandible so that the swallow
can begin, the teeth are brought together by the
jaw-closing muscles, and the lips usually seal.

(2) Pharyngeal phase :
Food bolus comes into contact with the mucosa
of the pharynx and larynx.
Nucleus ambiguous in the brainstem.
These and other interconnected nuclei in the
medulla near the floor of the fourth ventricle
comprise the so-called “swallowing centre” that
controls the sequence of the events manifest as a
swallow.
The next event in this complex sequence of
events is the inhibition of respiration.www.indiandentalacademy.com

The entrance to the larynx is pulled upwards
into the pharynx to a level at which food is less
likely to enter it.
The so-called pharyngo-oesophageal
sphincter then opens, and the food bolus or
liquid passes into the entrance to the
oesophagus.
Swallowing enables the pressure in the
middle ear to equalize with the pressure in the
pharynx.

(3) Esophageal phase :
Once in the oesophagus, the food bolus is
propelled towards the stomach by
peristalsis.
When the bolus nears the entrance to the
stomach, the gastro-oesophageal sphincter
opens and food enters the stomach.
Gravity

Infantile swallow :
The normal human fetus can swallow by the twelfth
week of gestation, which is before most cortical and
subcortical structures have developed in the central
nervous system.
The swallowing response is purely reflex in nature in the
new born.
Infantile swallowing is clearly adapted to suckling where
the diet is fluid only.
Infantile swallowing is characterized by swallowing with
the jaws (alveolar pads) apart, with the mandible stabilized
by the muscles of facial expression and the tongue.www.indiandentalacademy.com

The mother’s milk ejection reflex also causes the
milk to spurt from the nipple so that the milk is
deposited directly into the pharynx.
In swallowing, the entrance to the infant larynx is
elevated so that the epiglottis sits behind the soft palate.
As the infant matures, its swallowing pattern is
progressively modified in response to a number of
important changes.
•Firstly, the anatomy of the pharynx changes
•Secondly, the consistency of the food changes from
liquid to semisolid and solid.

Tongue thrust :
People may swallow 600 times per day or more and that, if
the tongue continues to be thrust forward with each
swallow during the phase of rapid growth, it will prevent the
anterior teeth from growing into their normal occlusal
relationship.
Even though the tongue may press on the anterior teeth
with forces of up to 20 N during a swallow, the total
duration of tongue thrusts is not sufficient to cause an open
bite.
Older denture-wearers.

Dysphagia :
Dysphagia is the subjective sense of difficulty in
swallowing which is caused by impaired progression of
food or liquid from pharynx to stomach.
Dysphagia can be the result of lesions of the pharynx,
oesophagus and adjacent organs.
It is also a common symptom in a number of
functional disorders of the neuromuscular system,
including stroke, cerebral palsy, multiple sclerosis,
Parkinson’s disease and scleroderma.

Dysphagia may be preoesphageal, resulting from
abnormal function proximal to the oesophagus.
Patients with oesophageal dysphagia have
difficulty moving food through the oesophagus.
Globus sensation

Vomiting, gagging and retching :
Vomiting is induced by gastric distension or irritation,
mechanical stimulation of the pharynx, or some drugs
(including narcotics and chemotherapeutic agents).
Like swallowing, vomiting is a highly-coordinated
response.
Vomiting is usually preceded by pallor, sweating and
salivation, reflecting the activation of the sympathetic
nervous system.

Vomiting is usually said to have three stages:
•First stage is nausea, characterized by a sudden
feeling of “sinking” in the epigastrium.
•Second stage of retching or gagging. Retching or
gagging consists of unpleasant spasmodic and
abortive respiratory movements with the glottis
closed.
A common stimulus for patients reclining in a
dental chair is the accumulation of fluid in the
pharynx which cannot be swallowed.
The making of dental impression can also
stimulate gagging.
•Gagging may or may not continue to the ejection
phase of vomiting which is called emesis.www.indiandentalacademy.com

Disorders :
Bulimia (often called bulimia nervosa) is a disorder
characterized by repeated bouts of overeating and an
excessive preoccupation with the control of body
weight.
Repeated vomiting has many consequences
including disturbances of electrolyte balance and
cardiac arrhythmias.
Acid dissolution of enamel particularly on the lingual
surfaces, and break-down of metal restoration and
orthodontic appliances.
GERD www.indiandentalacademy.com

SPEECH :

The neurophysiology of speech and language :
The cerebral cortex of the left hemisphere mostly
contributes to language processing and production.
The right hemisphere probably contributes to speech
melody (prosody).
Isolated lesions in the inferior aspect of the left frontal
lobe (Broca’s area) often result in slow, laboured language
production with only rudimentary grammatical structures.
Isolated lesions around the posterior end of the left
sylvian fissure (Wernicke’s area) can result in speech that
is more fluent but sometimes devoid of meaning.

The main structures responsible for motor coordination
of the articulators are found bilaterally in the pre-central
gyri.
The main cranial nerves that are responsible for voice
production and articulation of speech sounds are –
•Trigeminal – control of jaw movement and cranial facial
sensation.
•Facial – lip movement
•Vagus – pharyngeal and laryngeal muscles, pharyngeal
and laryngeal sensation.
•Hypoglossal – tongue movement

Functional subsystems of motor speech :
Speech production is broken down into five separate, but
interacting functional subsystems.
1)Respiration : airflow from the lungs is necessary to drive
the larynx and generate voice and speech.
2)Phonation (sound production) : air stream from the lungs
makes the soft cover of the vocal folds vibrate. This
generates a sound that is raw and unmodulated.

3)Resonance : the pharynx provides a resonating
cavity that helps shape the sound for speech or song.
The velopharyngeal sphincter mechanism also
regulates the nasality of a speech sound.
4)Articulation : sound stream that has been emitted
from the vocal folds and filtered in the pharynx is
further modified through multiple quick movements or
“gestures” by the articulators in the oral cavity.
5)Suprasegmental characteristics : this comprises
features of speech such as pitch, inflection and
rhythm of speech and is also referred to as prosody or
“speech melody”.

The exact articulatory gestures require precise fine motor
control and coordination of the motor speech subsystems.
Speech disorders related to cleft lip and palate
Many patients with clefts that involve the soft palate have
persisting difficulties with their velopharyngeal closure
mechanisms.
Many patients with cleft lip and palate exhibit hypernasal
speech.
Typical cleft palate compensatory articulation, which is
characterized by glottal and pharyngeal speech sounds.

Speech disorders related to dentition or occlusion
For speech articulation, the most crucial teeth are
front teeth.
Lisps.
In class II and class III occlusion.
Inverted and cross bite.

PROTECTIVE MECHANISMS
Sneezing:
Sneezing is a coordinated reflex that expels foreign
objects that have lodged into the nose.
The stimulus can be either particulate matter that
activates mechanoreceptors, or chemicals such as
ammonia and histamine that irritate chemoreceptors.
Stiff hairs in the nose.
These receptors send signals through the anterior
ethmoidal branch of the trigeminal nerve to the
medulla to trigger the series of reflex events that we
know as a sneeze.

Swallowing :
Swallowing is undoubtedly the most important
reflex that prevents foreign objects from entering the
airways.
The coordinated swallowing response reflexly seals
the back of the nose and the entrance to the trachea
to prevent the entry of foreign bodies and fluids into
these vulnerable areas.

Coughing :
This is an important defense mechanism of the
body that clears the larynx and upper airway of
excessive secretions and foreign matter.
The sensory signal is transmitted to the medulla
where the motor events mechanism of coughing are
triggered.
The efferent pathways are primarily cranial nerve X
and the cervical spinal motor nerves, including the
phrenic nerve. www.indiandentalacademy.com

Coughing can also be triggered by irritation of the
mucosa which often happens in the “dry” phase of upper
respiratory tract infections.
Coughing may occasionally also be the result of a
centrally-initiated signal in the absence of peripheral
stimulation.
In dentistry, it is not uncommon for patients to present
for treatment after taking codeine and / or alcohol to help
alleviate a painful intra-oral condition. The depression or
even absence of a cough reflex that these drugs induce
increases in the susceptibility of these patients to the
invasion of the respiratory tract by foreign particles.
The cough reflex may be absent in patients suffering
from severe cerebral palsy.www.indiandentalacademy.com

conclusion

References:
1) Understanding medical physiology.
- Bijlani
- 3rd edition.
2)Textbook of medical physiology.
- Guyton and hall
- 10th
edition.
3)Clinical oral physiology.
- Timothy S Miles.
4)Essentials of oral physiology.
- Robert M Bradley.
5)Management of temporomandibular disorders and
occlusion.
- Jeffrey P okeson
- 5th
edition
6)Oral bioscience.
- David B Fergusion

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