The topic studied actuality. Dentist should remember that oral cavity different functions (afferent, secretory, motor, adsorbtive) disorders can be determined by local factors

Dentist should remember that oral cavity different functions (afferent, secretory, motor, adsorbtive) disorders can be determined by local factors, peripheral nerves diseases as well as central cerebral structures injures. Medulla oblongata and pons cerebri belong to such central structures. They contain nuclei of such nerves which provide oral cavity organs and face functioning. Trigeminal, facial, glosso-pharyngeal, hypoglossal cranial nerves belong to them.

Dentists can get in touch with patients with oral cavity afferent function disorders when different sensitivity types (tactile, temperature and gustatory) are disturbed. Masticatory and mimic musculature activity became changed due to oral cavity motor function disorder. Also one can meet secretory dysfunction. It is expressed in salivary glands activity changing. Patient complaints on general sensitivity loosing, sharpening, reducing or injure (anesthesia, hyperesthesia, hypoesthesia, dysesthesia), speech and mastication injury, hypo- or hypersalivation.

Normal functioning of this brain part is vital because even the least injury of this area as a rule leads to grave vital activity disorders (respiration, heart and vessels, digestion activity disturbances).

 

2. Study aims:

To know: posterior brain reflectory activity; posterior brain morphological-functional peculiarities; reticular formation ascendant and descendant influence mechanism; cranial-cerebral nerves role; medulla oblongata centers.

To be able to: investigate cranial-cerebral nerves function and posture static reflexes.

 

Pre-auditory self-work materials.

Basic knowledge, skills, experiences, necessary for study the topic:

Subject	To know	To be able to
Histology	Posterior brain histological structure	Recognize posterior brain preparation
Anatomy	Posterior brain anatomical structure and conductive ways, cranial-cerebral nerves location	Draw posterior brain ascending and descending conductive ways
Biochemistry	Nervous tissue metabolism peculiarities
Neurology	Posterior brain external and internal structure, conductive ways, cranial-cerebral nerves (VIII-XII pairs in medulla oblongata; V and VII pairs in pons) morphology and functions (norm and pathology)	Draw posterior brain conductive ways, cranial-cerebral nerves nuclei location.
Dentistry	Mentioned cranial-cerebral nerves anatomy, physiology	Analize posterior brain and cranial-cerebral nerves pathology signs.

 

Topic content.

 

Posterior brain consists of pons and medulla oblongata.

 

Medulla oblongata functions:

I. Reflectory:

1. Defencive:

· cough;

· blinking;

· tears releasing;

· vomiting.

2. Alimentary:

· sucking;

· swallowing;

· releasing of digestive juices.

3. Cardio-vascular (heart and vessels activity regulation).

4. Respiratory.

5. Control of volume of information conducting by spinal column.

6. Sound frequency, intensivity and origin recognizing.

II. Conductive.

 

Brainstem is the part of brain formed by medulla oblongata, pons and midbrain. It forms:

1) the pathway for ascending and descending tracts of nerve fibers between brain and spinal cord and

2) location of many important centers for regulation of vital functions in the body.

 

Medulla oblongata is continued downwards as spinal cord. This forms main pathway for the ascending and descending tracts of spinal cord. It also has many important centers, which control the vital functions.

Respiratory centers: Inspiratory and expiratory centers are the medullary respiratory centers maintaining normal rhythmic respiration.

Vasomotor center: This center controls blood pressure and heart rate.

Deglutition center: This center regulates the pharyngeal and esophageal stages of deglutition.

Vomiting center: It induces vomiting during irritation or inflammation of Gl tract.

Superior and inferior salivatory nuclei: The salivatory nuclei control the secretion of saliva.

Cranial nerve nuclei: The nuclei of 12th, 11th, 10th and some nuclei of 8th and 5th cranial nerves are located in the medulla oblongata. 12th cranial (hypoglossal) nerve controls the movements of tongue. 11^th cranial (accessory) nerve controls the movements of shoulder. 10th cranial (vagus) nerve controls almost all the vital functions in the body: cardiovascular system, respiratory system, Gl, etc. 8th cranial nerve (the cochlear division of this nerve), which has the relay in medulla oblongata is concerned with the auditory function.

Vestibular nuclei: Vestibular nuclei contain the second order neurons of vestibular nerve. There are four vestibular nuclei situated in the rostral part of medulla and caudal part of pons namely, superior, medial, lateral and inferior vestibular nuclei. The medial and inferior vestibular nuclei extend into the medulla. All the medullary centers and nuclei of cranial nerves are controlled by the higher centers situated in cerebral cortex and hypothalamus.

Pons cerebri

This forms a bridge between medulla and midbrain. The functions of pons are:

1. The axons of pontine nuclei join to form the middle cerebellar peduncle or the brachium pontis, Pons forms the pathway connecting the cerebellum with the cerebral cortex.

2. The pyramidal tracts pass through the pons.

3. The medial lemniscus is joined by the fibers of 10th, 9th, 7th and 5th cranial nerves in pons.

4. The nuclei of 8th, 7th, 6th and 5th cranial nerves are located in pons.

5. It contains the pneumotaxic and apneustic centers for regulation of respiration.

6. Pons also contains the vestibular nuclei, which are already mentioned in medulla oblongata.