Grass Tetany by André Voisin

PART IV

THE NEURO-HORMONAL BALANCE OF
THE ANIMAL AND GRASS TETANY

The chapters in this Part are only for specialist reading. Readers who wish may restrict themselves to the summaries that precede each chapter.

CHAPTER 18

Adaptation mechanisms in the neurohormonal system to imbalances in grass

SUMMARY
When herbage exhibits a tendency to diminish the magnesium content of the blood serum, certain neuro-hormonal mechanisms come into action in an attempt to check this diminution.

Adaptation of the organism to the hypomagnesaemia-producing effects of the herbage

The content of magnesium (or other mineral elements) in the blood serum is kept constant by different neuro-hormonal mechanisms.1 When different imbalances in the composition of the herbage and/or under-feeding tend to lower the magnesium content of the blood certain modifications take place in these mechanisms: this being the organism's attempt to keep the magnesium in its fluids at a constant level.2
All these mechanisms together make up the "syndrome of adaptation" 3 to the situation created in the organism by a diet of herbage that promotes hypomagnesaemia.4
If this adaptation cannot be effected, or only incompletely, then there take place simultaneously, and by reciprocal action:
- a drop in the magnesium content of the blood serum (as well as other changes in the blood serum);
- functional upsets in the neuro-hormonal system.
Finally, nervous fits are present.5

Simplified examination of scientific problems about which little is known

Still very little is known about:
- the effects of feeding on the neuro-hormonal system;
- the mechanisms by which the neuro-hormonal system keeps the content of magnesium (or other mineral elements) in the blood serum at a constant level;6
- how a reduction in the magnesium content of the blood serum triggers off convulsions, that is to say, disturbs transmission in the nerves and muscles.
An attempt will be made, however, in the present Part to examine, briefly and simply, the scant theoretical knowledge at present available, allowing us not to understand but to get an inkling of the mechanisms that bind:
feeding;
mineral composition of the blood serum;
normal neuro-muscular transmission;
hormonal secretion of the endocrine glands.

These four elements, in fact, are but four aspects of a single question. It must always be borne in mind that the sole aim of this concise study is to improve our understanding of all the phenomena associated with the etiology and therapeutics of grass tetany and, still more, to help us to determine and explain practical methods of protection against "grass tetany". To this end, therefore, only individual theoretical views throwing light on these practical aspects will be considered.

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Notes



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  1. 
Or neuro-endocrine, the hormones being produced by the internal secretory
       endocrine glands. * 
    


    

    
 

  2.  
This is what is known as homeostasis and represents the effort of the 
organism to maintain different physiological constants (composition of the 
blood, temperature, etc.) at a normal value despite alterations in the 
external environment, diet, etc. This, then, is "physiological stability".
 * 
           



    

    
 

  3.  
SELYE's expression, the originator of the idea of stress. * 
    


    

    
 

  4.        
It appears to be particularly in the case of spring grass tetany (or under 
similar conditions) that the adaptation possibilities of the neuro-hormonal 
system are rapidly exceeded. A dietary influence is at work here upsetting 
the neurohormonal system. * 
    



    

    
 

  5.        
As CHARTON so aptly states: "The nervous manifestations are 
the result of complex functional upsets in the neuro-hormonal system as a 
whole. A sequence of disturbances of the neuro-hormonal mechanisms 
controlling the metabolism of the mineral elements leads to considerable 
modifications in the steadiness of neuro-muscular excitability. . . . 
Everything takes place as if the neuro-hormonal regulatory mechanisms had 
lost the capacity to mobilize the calcium and 
magnesium reserves of the organism." * 
    



    

    
 

  6.        
And, conversely, how an alteration in this content of magnesium (or other mineral
       elements) affects the neuro-hormonal system. *