Materials for auditory self-work. List of study practical tasks necessary to perform at the practical class.
List of study practical tasks necessary to perform at the practical class.
Materials and methods: vertical myograph, stimulator, irritating electrods, kymograph, universal stand, preparating instruments set, pipette, gauze napkin, Ringer’s solution.
Investigation object: frog.
Task 1. Isolated impulse conducting law (through nervous fibers).
The students must prepare the preparation of frog’s lower extremities with skin taking off and with 3 lower vertebras saving. You should ligatured each of nervous fibers at the place of sciatic nerve exit from the spine and to separate from the spine. Students must irritate every fibre of sciatic nerve one after another with weak electrical current, while observing different irritation phenomena at it.
Task 2. Two-sized conduction law.
Students must make frog’s extremity and preparated sciatic nerve so that not to hurt branchlets passing to the musculus quadriceps femoris and gastrocnemius muscle. One should irritate the nerve by electrical current near gastrocnemius muscle and observe the contraction both musculus quadriceps femoris and gastrocnemius muscle.
Task 3. Physiological integrity law.
Put the preparation on glass plate. To irritate the preparation nerve by electrical current. Frog’s leg is bended. To put the ligature on sciatic nerve. To irritate the nerve by electrical current again. The muscle doesn’t contract. If you attach the electrodes so that the ligature is between 2 electrodes the leg will be contracted. To repeat the examination but to use cotton wool tampon washed in novocain solution despite ligature.
Task 4. To study fatigue (tiredness) ability in synapse.
To prepare nervous-muscular preparation and to fix it into myograph. To irritate this preparation nerve with optimal frequency and force (voltage 1-5 V, frequency 50-100 Herz), to registrate myogram till tiredness becoming; to move electrodes to the muscle having increased the irritation force till optimum for tired muscle (10-20 V) and to continue to registrate myogram. The contraction altitude must get increased at it.
In conclusion: students must underline main synapses tiredness reasons and to mark that synapse is the most highly-tired structure in a whole central nervous system.
5. Literature recommended:
1. Lecture course.
2. Mistchenko V.P., Tkachenko E.V. Methodical instructions for dental students (short lecture course).-Poltava, 2005.-P. 10-11.
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3. Mistchenko V.P., Tkachenko E.V. Methodical instructions for medical students (short lecture course).-Poltava, 2005.-P.12-13.
4. Mistchenko V.P., Tkachenko E.V. Methodical instructions on Normal Physiology on practical classes for dental and medical students.-Poltava, 2005.-P.23-25.
5.Ganong W.F. Review of Medical Physiology.-21st ed.-2003.-Section II.
6. Kapit W., Macey R.I., Meisami E. The Physiology Colouring Book: Harpers Collins Publishers, 1987.-P. 15-17.
7. Bullock J., Boyle III J., Wang M.B. Physiology.-1991.- P.18-28.
8. Guyton – Ganong – Chatterjee. Concise Physiology /Ed. By Dr Raja Shahzad Gull: M.B.B.S., F.C.P.S., King Edward Medical College.-Lahore, 1998 (1st Edition).-P. 254-257.
9. Guyton A.C. Textbook of Medical Physiology.-NY, 1992.-P. 546-579.
6. Materials for self-control:
A. Control questions:
1. Nervous fibre structure.
2. Nervous fibers 2 kinds and their peculiarities.
3. Nervous fibre action potential.
4. Excitement conducting laws through nervous fibre.
5. Excitement conducting ways (mechanisms) through nervous fibers of different types.
6. Conductance laws possibilities and prospects of application in dentistry.
7. Synapses structure peculiarities and classification.
8. Chemical synapses and electrical synapses functional features.
9. Ion mechanisms of exciting post-synaptic potential (EPSP).
10. Exciting mediators.
11. Nervous-muscular and central synapses distinguishing features.
12. Synaptic lack and its physiological role.
LESSON 7
Practical experience management on content credit 1,2: “Excitable tissues physiology”
1. To assess resting membrane potential as well as action potential of nervous and muscular fibers.
2. To draw action potential and excitability changings during it.
3. To estimate depolarization threshold.
4. To draw muscles contraction curves (dependently on irritation rate) and excitability changing during them.
5. To explain muscles contraction and relaxation mechanisms.
6. To explain ways of excitement nervous-muscular conductance and different factors influence on these processes.
7. To interpretate masticatory muscles electromyogram.
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CONTENT CREDIT 3: “ORGANISM FUNCTIONS NERVOUS REGULATION”
LESSON 8
Reflex arc investigation. Receptors physiology.
The topic studied actuality.
Nervous system diseases place one of the first places as for morbidity and lethality together with heart-vascular disorders and infectional pathology. Nervous regulation mechanisms dysregulation leads to functions dyscoordination and organism desadaptation. That is why nervous regulation functioning mechanisms and regularities knowledge is so essential for doctor of any speciality. Oral mucosa is often injured at dental diseases. It is expressed on its sensory function.
Knowledge about CNS functions is widely used by doctors of any profile for patients treatment, diseases prevention and diagnostics. CNS state investigation is applied in labor physiology, sport physiology, cosmic physiology and other physiology chapters.
2. Study aims:
To know: reflectory theory main principles; the term “reflex”; reflexes and reflectory arcs types; reflectory arcs main parts; receptors classification, features.
To be able to: draw reflectory arc and designate its main elements; to explain excitement conductance regularities (receptor and generator potentials).
3. Pre-auditory self-work materials.
3.1.Basic knowledge, skills, experiences, necessary for study the topic:
| Subject | To know | To be able to |
| Medical biophysics | The explanation of reflex time assessment and irritation threshold determining diagnostic methods physiological basements | Manage the skills of work on electrical and medical devices |
| Anatomy | Analyze of information about central nervous system structure | Determine the topographical-anatomical interrelations of human organs and systems |
| Histology | Neurons and receptors membranes structure | Determine total-biological laws action expressions during human ontogenesis; draw membrane structure and analize its functions |
| Biochemistry | Analyzis of bioorganic chemicals correspondence to physiological functions | Analize enzymatic processes functioning in membranes. |
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Topic content.
Nervous and endocrine system controls all activities of body. Primarily, nervous system is divided into two parts:
1) central nervous system;
2) peripheral nervous system.
CENTRAL NERVOUS SYSTEM
It includes brain and spine. It is formed by neurons and supporting cells called neuroglia. The structures of brain and spinal cord are arranged in two layers namely grey matter and white matter. Grey matter is formed by nerve cell bodies and proximal parts of axons and dendrites. White matter contains nerve fibers.
PERIPHERAL NERVOUS SYSTEM
It is formed by neurons and their processes present in all regions of body. This consists of cranial nerves arising from brain and spinal nerves arising from spinal cord. This is again divided into two subgroups:
a) Somatic nervous system and
b) Autonomic nervous system.
Somatic Nervous System
It includes nerves supplying skeletal muscles. Somatic nervous system controls movements of body by acting on skeletal muscles.
Autonomic Nervous System
It is concerned with regulation of visceral or vegetative functions. So, it is called vegetative or involuntary nervous system with other words. Autonomic nervous system consists of three parts:
a) sympathetic,
b) parasympathetic and
c) metasympathetic.
The idea about the fact that organism having nervous system has possibility to react to external stimuli action by type “buttom-answer” was pronounced by French phylosophist Reneh Decart (XVII-th century).
The term “reflex” was introduced by Irgi Prochazka at the end of XVIII-th century.
The theory of reflectory activity was developed by:
I.M.Sechenov (inhibiting phenomenon discovery; to his point of view, all conscious and unconscious reactions are the reflectory ones).
I.P.Pavlov (science about conditioned reflexes).
Reflex action – 1) is a protective phenomenon which occurs in response to a change inside or outside of the body;
2) responce resulting from passage of a nerve impulse through a reflex arc.
Reflex arc:
It is composed of 5 components i.e.:
1) Afferent neuron: from receptor to CNS.
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2) Inter Neuron (interneuron) or associative neuron: which lies inside CNS.
3) Synapse: which is the contact between 2 neurons.
4) Efferent Neuron: which comes from CNS upto the effector organ.
5) Efferent Organ: which may be:
– skeletal muscle.
– smooth muscle.
– glands.
Reflex arc types:
1. Simple – without associative link.
Complex – with associative link.
2. Monosynaptic (little amount).
Polysynaptic: tendinous, from skin flexors et al.
3. Somatic (animalous).
Vegetative (autonomic).
Reflex action properties:
1. The law of forward conduction.
2. Localization.
3. Summation:
– Temporal summation.
– Spatial summation.
4. Facilitation phenomenon.
5. Central fatigue phenomenon.
6. Central block phenomenon.
7. Central delay.
8. Fractionation phenomenon.
9. Irradiation phenomenon.
10. Recruitment and after discharge.
11. Reciprocal innervation.
12. Occlusion.
13. Central inhibiton.
14. Rebound phenomenon (feed-back reaction).
Reflexes classification:
І.According to reflectory arc formation:
| Uncondioned or non-conditioned | Conditioned |
| Inborn and transmitted by hereditary to all individuals; they are present at birth. Examples: swallowing, breathing, salivation (sialorrhea or ptyalorhea). | They are acquired by organism throughout his life. They are absent at birth. |
| They are species characteristics. | Individual ones. |
| They have constant reflectory arcs and are closed at spine and brain stem level. | Reflectory arcs are temporary, they are closed at brain hemispheres level. |
| They are practically constant, non-changed. | Changeable, may appear and disappear. |
| They are realized in response to specific (adequate) irritation without any conditions. | They are realized in response to any irritation percepted by organism. They are formed on the base of unconditioned reflexes. |
| They are realized at level of spine, stem and subcortex nuclei. | They are formed by subcortex but are realized by cortex. |
| Biological role: they provide organism’s existance at first moments after birth and then they are the base of conditioned reflexes development. | Biological role: they encourage to organism adaptation to environmental conditions. |
ІІ.According to reflectory arc components:
1. Monosynaptic.
2. Polysynaptic.
ІІІ.According to main arc neurons localization:
1. Spinal.
2. Stem:
– bulbar;
– of pons cerebri.
3. Cerebellar.
4. Mesencephalic.
5. Subcortical.
6. Cortical.
ІV.According to receptors character, the irritation of which causes given reflex:
1. Interoceptive.
2. Proprioceptive.
3. Exteroceptive or:
4. Nociceptive.
5. Visual.
6. Gustatory.
7. Auditory et al.
V.According to receptors localization:
1. Superficial:
A. Skin:
– cremasteric,
– planter,
– abdominal et al.
B. From mucous membranes:
– corneal;
– conjunctival et al.
2. Deep:
A. Muscular.
B. Tendinous:
– biceps jerk;
– triceps jerk;
– knee jerk;
– ankle jerk et al.
C. Periosteal:
– carpo-radial et al.
VI.According to biological significance:
1. Sexual.
2. Defensive.
3. Alimentary et al.
VII.According to principle - what part takes part in reflex realizing:
1. Somatic.
2. Vegetative.
VIII.According to ending result:
1. Alimentary.
2. Respiratory.
3. Cardiac.
4. Vessel.
5. Salivatory et al.
Receptor is a specialized structure at the terminoma (end) of afferent neurons. It responds to minor changes around it, inside or outside the body.
Receptors tasks:
1) giving information about stimulus nature;
2) giving information about stimulus force;
3) giving information about stimulus action time;
4) analysis can not be realized without them.
There are several approaches to the receptors classification (and, thus, several receptors types).
Receptors classification
I. According to the localization:
1. Exteroreceptors:
A. Skin
B. Visual mucosas (particularly of oral cavity)
2. Visceroreceptors:
A.Interoreceptors – in inner organs
B.Proprioreceptors – in motor apparatus and vestibular apparatus.
II. According to the activity character:
1. Exteroreceptors:
A. Contact:
a) tactile (cutaneous):
- tactile corpuscles for touch - Meissner's corpuscles and Merkel's discs;
- Pacinian corpuscles for pressure;
- Rouffinian bodies for vibration
b) temperature:
-free nervous terminals for heat;
-end bulb of Krause for cold;
-receptors of burning sensation
c)nociceptors (pain receptors):
-of skin;
-of mucosas (visual);
d) of taste (4):
-for bitter;
-for sugar;
-for salty;
-for sour.
B. Distant or telereceptors - give response to stimuli arising away from the body:
a) photoreceptors (to light);
b) phonoreceptors (to sound);
c)olfactory;
d) temperature (if the irritation source is very powerful)
2. Interoreceptors:
A. Presso- (baroreceptors):
-in vessels;
-in sexual organs.
B. Chemo-receptors.
C. Nociceptors.
D. Temperature.
3. Proprioreceptors - give response to change in the position of different parts of the body:
A. Muscular (muscle spindle)
B. Tendinous (Golgi tendon organ)
C. Of ligaments
D. Of joints
E. Receptors in labyrinthine apparatus namely, crista ampullaris in semicircular canals and macula in utricle and saccule.
III. By the nature:
1. Mechanoreceptors.
2. Thermoreceptors.
3. Nociceptors.
4. Electromagnetic receptors (which detect light on the retina of an eye)
5. Chemoreceptors – they detect:
– taste in the mouth;
– smell in the nose;
– oxygen level in the artery blood;
– osmolality of the body fluids;
– carbon dioxide.
IV. According to structure:
1. Simple (primary-sensing) – nerve ending:
– olfactory;
– cutaneous.
2. Complex (secondary-sensing) – they have a special receptor cell in front of nerve ending:
– photo-;
– phono-.
Fig.16.Cutaneous receptors.
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