Materials for auditory self-work. 4.1.List of study practical tasks necessary to perform at the practical class.



4.1.List of study practical tasks necessary to perform at the practical class.

Materials and methods: current source, electrodes, preparating plank, glass plate, kymograph, current source, metronom, cotton wool, napkin, sodium chloridum, 0,5% solution of sulfuric acid.

Investigation object: frog.

 

Task 1. Temporary excitement summation.

The experiment must be performed on thalamic frog. For this aim it’s necessary to cut frog’s head behind her eyes. Then students should put the animal to the operation table. You should fix the electrodes on one of posterior legs. The electrodes must be connected with the stimulator. The electrodes must be put above and below knee joint over the distance at least 0,5 cm between each other. One should find threshold irritation force. Then one must observe the reaction at irritation with the frequency of 1 Herz, 20 Herz.

Task 2. Excitement summation.

Thalamic frog must be hanged by her inferior jaw on hook. You must put cork at the end of the hook till the end of the animal’s movements. Spatial summation can be observed while flexing reflex. You must wash frog’s posterior leg fingers ends in threshold concentration acid and determine reflex time having counted seconds number from the beginning of fingers sinking till the leg’s jerking back moment. Then after leg’s washing in the glass of water you must determine reflex time at foot sinking in acid.

 

5. Literature recommended:

1. Lecture course.

2. Mistchenko V.P., Tkachenko E.V. Methodical instructions for medical students (short lecture course).-Poltava, 2005.-P. 13-14.

3. Mistchenko V.P., Tkachenko E.V. Methodical instructions on Normal Physiology on practical classes for dental and medical students.-Poltava, 2005.-P.34-36.

4. Mistchenko V.P., Tkachenko E.V. Methodical instructions for dental students (short lecture course).-Poltava, 2005.-P.12-13.

5. Kapit W., Macey R.I., Meisami E. The Physiology Colouring Book: Harpers Collins Publishers, 1987.-P.16, 82.

6. Guyton A.C. Textbook of Medical Physiology.-NY, 1992.-P. 562-571.

 

6.Materials for self-control:

A. Control questions:

1. Neuron. Neurons main features and functions.

2. Synapses structural and functional peculiarities.

3. Chemical and electrical synapses functional distinguishing features.

4. Exciting mediators.

5. Nervous center and its part.

6. Excitement conductive mechanism in nervous centers.

7. Exciting post-synaptic potential. EPSP ionic mechanisms.

8. How to explain one-sided and retarded (lacked) excitement conductance in synapses?

9. How to explain nervous centers fatigue?

10. Temporal (consequent) excitement summation.

11. Spatial summation (realized at the same time).

12. Excitement rhythm transformation (decreasing and increasing).

13. Excitement afteraction and its significance.

14. Explain significance of nervous centers sensitivity to oxygen deficiency and chemicals.

15. Inhibitory neurons and their functions. Inhibitory mediators.

16. Central inhibition main types. Inhibitory synapses.

17. Presynaptic inhibiting developmental mechanisms.

18. Postsynaptic inhibiting developmental mechanisms.

19. Inhibitory postsynaptic potential (IPSP).

 

 

LESSON 10
Reflex activity co-ordination mechanisms investigation.

The topic studied actuality.

CNS belongs to highly-regulated and at the same time to quite sensitive (vulnerable) systems. As it was mentioned above, CNS pathology nowadays takes one of dominant places in diseases, morbidity and lethality spectra.

At teeth and other organs diseases in facial-maxillar region afferent impulsation is increased significantly. It leads to excitement generalized spreading. Excitement irradiation under very splitting pain conditions (for instance, at pulpits) leads to such circumstances when the sick person can not locate the pain observed and so to indicate injured tooth.

Prolonged noceoceptive (pain) syndrome can create dominant excitement focus in corresponding nervous centers. Any side stimuli (touching, bright light, strong sound) enforce pain under such conditions.

As it is known, there can be pain sensations in places located far away from pathological focus or increased sensitivity development there at different inner organs diseases. Separate skin and mucosae locusi correspondingly to one or other visceral organ are known as Zahar’in-Ged’s zones. They are used particularly in acupuncture. Pain in zones located on face can be observed as a result of teeth diseases (pulpits, periodontits) as well as result of inner organs pathology due to excitement irradiation from far places from injured organ through vagus and diaphragmal nerve.

Zones location in face and head areas at somatic pathology is less strong than at odontogenic pain and pain has distinct boarders with pain syndrome maximal determining.

 

2. Study aims:

To know: reflexes co-ordination principles with corresponding neuronal chains participation in organism adaptive reaction providing; irradiation, concentration, divergence, convergence, occlusion, dominanta, general ending ways mechanisms.

To be able to: mark schematically CNS neuronal links different types structure; draw several co-ordination principles (divergence, convergence, ending general way).

 

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 Nervous impulse occurrence biophysical mechanisms explanation. Manage the skills of work on electrical and medical devices
Histology Neurons structure and functions; synapses and nervous centersss structure Draw chemical synapses structure
Biochemistry Nervous tissue metabolism distinguishing features  
Neurology Nervous centers features and their possible disorders, representation about reflectory activity main co-ordination types, their significance and possible disorders.  

Topic content.

These principles make one’s reflectory activity urgent, well-singleminded, accompanied by less energy consumption and so more comfortable for performance by organism. Main of them are:

Convergency (convergence) - is many afferent ways gathering to one neuron (associative or efferent one); with other words – it is so when many presynaptic neurons terminate on singular postsynaptic neuron.

Divergency (divergence) – is an ability to form polysynaptic bonds (it lies on the base of irradiation); with other words – it is so when one presynaptic neuron terminates on many postsynaptic neurons; this principle is opposite to convergence.

Total ending way principle (discovered by Charles Sherrington in 1906). Essence: impulses from many receptors of different body parts come to one motoneuron (convergence is on its base). Information through afferents come to associative neurons, efferents and finally to axon of 1 motoneuron. This axon represents total ending way. Such a principle realizing is possible because afferents number is bigger than efferents in 5 times. This principle second name is watering-can principle. Role: only several, the mostly important and essential at the moment impulses (of all coming through all different ways) will give answer reaction.

Irradiation – (from Latin word “irradiare” – “shine, beam”) – excitement distribution through CNS. 2 main types:

a) elective – it is physiological one – impulses are distributed through definite ways involving just essential organs and muscles in the reaction; if one needs to wake up more rapidly and to have better mental abilities he can make following procedure in the morning right after standing up: washing face with cold water (at the biggest degree – “drinking through nose”) will activate trigeminal nerve, reticular formation and finally cortex. It is so-called activation reaction lying on the base of human consciousness. Use this during exam – and you will see that your mental abilities will be great;

b) diffused (generalized) – other muscles get involved into the reaction, disturbing the movement and making it constrained (bound). Examples: “start fever” in sportsmen, epilepsy. This type of irradiation is physiological one for lower animals such as amphibias (their subcortex is developed more than cortex).

Concentration – phenomenon opposite to irradiation. It is information coming from different presynaptic neurons to one postsynaptic one on the base of convergence. So, convergence is primary, information concentration – secondary process (like divergence is primary, irradiation is secondary process).

Occlusion is nervous centers interference. Final result of such an interference is less, quicker. This principle is known from dentistry (occlusion of jaws mean denturing).

Dominanta (Alexei Uhtomsky, 1904) – temporally prevailing excitement focus determining answer reactions character to all external and internal stimuli. External expression of dominanta is a definite activity or organism working posture (pose) supported by different stimuli and excluding other activities and poses for a given moment. Reasons: leading motivation, impulsation increasing to the excitement locus from effector, biologically-active substances (hormones and others) level increasing in blood. Examples: sexual (hormones increasing), dominanta of urinary vesicle or stomach (increased impulsation from urinary vesicle and from stomach).

Dominant focus 5 main characteristics:

– increased excitability;

– excitement stability;

– increased ability to excitement summation;

– inertia – ability to preserve excitement for long after stimulus action stoppage;

– ability to cause conjugated inhibition in neighboring nervous centers.

Feed-back reaction or opposite afferentation principle – afferentation from effector about action final result.

Induction of excitement and inhibiting. Excitement and inhibiting interact. Big hemispheres cortex definite locuses excitement causes inhibiting in other cortex parts and, on the contrary, inhibiting in one cortical points causes excitement in others. This phenomenon is performed by law of mutual excitement and inhibiting. One differentiates 2 induction types.

a) Positive – inhibiting in separate cortical point causes excitement in other locuses. Organism activity is realized by direction of this excitement, attention to the current activity is enforced.

b) Negative – excitement in one cortical focus causes inhibiting in its those parts which have been active before. Negative induction acts at inclination from main (dominant) activity and it is concentrated on occasional stimuli, which inhibit excitement from main stimulus. Result: coming out of the activity performed.

 


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