Nerve impulse

“ The waste of the nerve-centers having become such that the stimuli received from the external world no longer suffice to call forth from them adequate discharges, there results a diminished impulse to those internal organs which subserve nervous activity, including more especially the heart. ”

“ When a weak electrical stimulus is applied to isolated nerve-fibre, and the impulse which in consequence travels along the nerve is measured, it is found that if the stimulus is weak there is no impulse at all, or more correctly, the electrical behaviour of the nerve gives no evidence of any impulse. If strength of the electrical stimulus is gradually increased, a point is reached when the nerve gives the response normally associated with an impulse passing along its length. ”

“ Owing to the existence of a chain of neurons, that is, a succession of nervous elements, instead of one continuous nerve fiber from center to periphery, it is possible for one of the neurons of the chain to be so disturbed that the conducting apparatus is interrupted and impulses do not flow. Hence, if a strong impression is produced on the mind with regard to a particular part of the body the neurons leading to it may be so disturbed that trophic nerve impulses do not flow down, the blood supply of the part may be disturbed through the vaso-motor system and consequent changes may take place. ”

“ All that such oscillations do, if continued, is to produce a temporary paralysis or fatigue of the nerve, so that it is unable to transmit the nerve impulses evoked by other stimuli, from which paralysis it recovers readily enough in course of time. ”

“ The conservation of energy therefore forbids us to suppose that any physical energy is lost when sensory nerve-impulses give rise to a sensation, or that any energy comes into existence when a volition is followed by a nervous discharge into the muscles. We must rather suppose that the sensory nerve-impulses produce commotions in the cortical nerve-cells, and that these manifest themselves in consciousness in the form of a sensation ”

“ How, then, do we explain those morbid phenomena which have their origin in misplaced affection, in disappointed ambition, in hatred, or in anger, and which culminate either in serious chronic maladies, or in death or suicide? They all seem to start from an impairment of the cerebro-spinal centres. The continual excitation of these by everpresent emotions determines a paralysis of the central nerve-substance, and thus affects its connections with the nerves extending out to the various organs. These nerves next degenerate by degrees, and soon the great functions are compromised. ”

“ For it is to be observed that, while the sensations conveyed by the healthy nerve are correct in the indications which they afford to the percipient brain, the indications given by pain are vague and untrustworthy, and often seriously misleading. Not to speak of the nerves of special sense, or of the fibres which convey the sensations of muscular movement, even the nerves of common sensation do carry to the internal perception, in health, a distinct impression of the well-being of the organs to which they are distributed. ”

“ In this state and the consequent excitement of the nerves, she had almost wholly lost organic force, and received it only by transmission from those of stronger condition, principally from their eyes and the ends of the fingers. The atmosphere and nerve communications of others, said she, bring me the life which I need; they do not feel it; these effusions on which I live, would flow from them and be lost, if my nerves did not attract them; only in this way can I live. ”

“ Experience seems to teach that in those patients whose brains have been so weakened by long-continued peripheral excitement, causing frequent and increasing losses of nerve force, there is not sufficient mental power to enable them to control any less powerful irritation of smaller branches of the pudic nerve, than that removed by operation. ”

“ We also find that the disease is often the result of some nervous strain, or over excitement The over indulgence of the passions is particularly a fruitful source of injury to the brain and spinal centres. An angry man or woman uses up more nerve energy in a few minutes than would be sufficient to serve the muscles with stimulus through hours of toil. ”

“ When a stimulus of any kind, whether mechanical, chemical, electrical, or vital, acts upon the living nervous substance, it produces an impression on that nerve substance and excites within it some particular change, and the property by which this takes place in the nerve substance has been called its excitability or neurility. ”

“ At the surface of the body and limbs, the external termini of the nerves are exposed to disturbance by contact with an external object. Along the highly sensitive and minute conductor, the nerve which has by contact with an external object at its outer extremity received a slight shock, there passes through the fluid or semi-fluid substance of the nerve a wave of disturbance, or a succession of such waves. This disturbance reaches the brain, the great nerve-center, where it becomes a feeling. ”

“ They seem, at times, to be duly supplied, but the forces may as quickly depart and leave the system languid and depressed, without power to coordinate the muscles. This more especially applies to a certain class of cases which assimilate organic trouble in the nervous structure. No change observable takes place in the circulation, yet it must stand to reason that the replenishing power of the nerve-matter is deficient. ”

“ This brings me to the consideration of another point, namely, that violent stimulation of a centre exhausts the nerve-force, not of that centre only, but of the whole nervous system. A terrible shock may so use up the nerve-force that the individual falls senseless, or, short of this, he may yet be so paralyzed with fear or grief that he loses all muscular power, or he may be so violently moved that the great exertions which he makes only last for a short time. ”

“ It imagines that powerful peripheral excitements exhaust the irritability of the nerve, and through that of the centres, and induce a state of unimpressibility—analogous to that which exists in a nerve or nerve-centre, which is included in the circuit of a constant current. The nervous force is wasted, and, until an opportunity of repose is afforded to the centre, the faculty of impressibility cannot again revive. ”

“ During stimulation, therefore, a nerve exhibits a negative variation. We may express this in a different way by saying that a ‘current of action’ was produced in response to stimulus, and acted in an opposite direction to the current of injury (fig. 2, b) . The action current in the nerve is from the relatively more excited to the relatively less excited. ”

“ The technical term for nervousness is psycho-neurosis—disease of the psyche. There are certain "real neuroses" such as paralysis and spinal-cord disease, which involve an organic impairment of nerve-tissue. However, as this book deals only with psychic disturbance, we shall, throughout, use the term neuroses and psycho-neuroses indiscriminately, to denote nervous or functional disorders.
To still other people nervous trouble means fear,—just terrible fear without object or meaning or reason (anxiety neuroses) ; or a definite fear of some harmless object (phobia) ”

“ We have also observed that disturbance and imperfection of nerve-function may be produced in all persons by the action of causes operating from without upon the nervous system, and that the results may be similar in character, whether there has been too great or too little exercise of function. ”

“ We have now presented some evidence that nervous energy is discharged by the adequate stimulation of one or more of the various receptors that have been developed in the course of evolution. In response to an adequate stimulus, the nervous system is integrated for a specific purpose by the stimulated receptor, and but one stimulus at a time has possession of the final common path— the nerve mechanisms for action. The most numerous receptors are those for harmful contact; these are the nociceptors. ”

“ The body, with all its beautiful and wondrous adaptations, only supplies the means of perception and of acting. Nerve-matter is the evident medium and instrument of the being that perceives and acts through it. Physiologists appear to have demonstrated that an imponderable principle, akin to electricity, is evolved in the nervous system, and that currents of this [155] kind are constantly traversing the different sets of nerves, according to their office and function, either as the medium of sensation, volition, or of vegetative life. ”

“ Nervous Attacks.—What we call, for want of a better name, "nerve force," or "nerve action," is at any one time a definite quantity. In health it is distributed to all the sets of nerves equally, so that all work in harmony. ”

“ The shock to the nerve-centers which these momentary frights give, and the nervous strain which the city dweller endures from keeping a lookout for such dangers, can not fail to impair the strength of the nervous system. Through the nerves an injurious influence is exerted upon the heart also. ”

“ How often we hear that and how little does the person with steady nerves appreciate the tortures of "nerves."
A cut, a bruise, a headache, or any of the physical ailments can be quickly cured. Nature will mend the break, but tired, worn, stretched, abused nerves take time to restore. These nerve ailments call for most vigorous mental treatment.
Neurasthenia means debilitated or prostrated nerves and it shows itself first of all by worry. Worry means the inability to relax the attention from a definite fear or fancied hard luck. Worry leads to many physical and mental disorders. ”

“ Nevertheless, it is probable that many or most of the above symptoms of terror, such as the beating of the heart, the trembling of the muscles, cold perspiration, &c., are in large part directly due to the disturbed or interrupted transmission of nerve-force from the cerebro-spinal system to various parts of the body, owing to the mind being so powerfully affected. ”

“ For none do I know a land more delightful, than for him who, by long and severe mental activity, has exhausted the vital battery of nerve-force and disturbed the harmonious balance between the varied complex nerve-circuits. ”

“ How does fear operate upon the body [Pg 18] to produce sickness? By paralysing the nerve centres, especially those of the vasomotor nerves, thus producing not only muscular relaxation, but capillary congestions of all kinds. ”

“ If perturbation of nerve-function—a disturbance quite different from mere exaltation of the normal development of nerve-force—be the essence of pain, how comes it that pains of the severest type may be produced by changes in structures which are usually described, for practical purposes, as lying outside the nervous system? We must, in the first place, remark that the externality of any bodily tissue to the nervous system is more apparent than real. ”

“ The most complex habits, as we shall presently see more fully, are, from the same point of view, nothing but concatenated discharges in the nerve-centres, due to the presence there of systems of reflex paths, so organized as to wake each other up successively—the impression produced by one muscular contraction serving as a stimulus to provoke the next, until a final impression inhibits the process and closes the chain. The only difficult mechanical problem is to explain the formation de novo of a simple reflex or path in a pre-existing nervous system. ”

“ This excitation of the nerve can, however, be induced by very different kinds of processes, namely, by all processes which possess in common the condition that they suddenly increase certain disintegration processes in the living nerve substance. ”

“ Volition or thought may be too weak, per se, to influence nervous processes; but, when exceptionally active or potent, they may set into activity specific nerve energies which manifest in the manner known to us as motor and physical phenomena. ”

“ Striking and manifold are the disturbances of the nervous system which may be caused by amenorrhœa, ranging from increased irritability, hyperæsthesia of various nerve tracts, neuralgia, and the like, to severe psychoses. ”

“ Whatever facts may be cited in its favor are due to the properties of nerve-tissue, which may be exhausted by too prolonged an excitement. Patients with neuralgias that last unremittingly for days can, however, assure us that the limits of this nerve-law are pretty widely drawn. ”

“ There is nothing so plentifully, and nothing more curiously interwoven with every other substance, as the nerves; and so amazingly quick is their sensation, that the very instant a single nerve, even the smallest and remotest in the system, is affected, the soul, or the common sensorium, is sensible of the identical part so affected. ”

“ Helen: And what sends the messages to and from the brain over the nerves, mother?
Mother: The power which sends them is called “nerve force,” though what it is even the wisest men do not know. We can stop it by pressing on the nerves, just as you can stop the current of the telegraph. We sometimes say that our leg or arm is “asleep.” If we try to move, it gives us pain, or it may be we can not move at all. One nerve runs along the back side of the arm over the elbow. If we hit the elbow, it makes the arm and hand feel numb. ”

“ Ask nine persons out of ten, who are of susceptible organization, at what period in life their sufferings were most intense and unremitting, and if they be gifted with good memories, their reply will be, 'before adolescence.' [3] For susceptibility of nerve implies also high mental capability, acute intelligence, vivid imagination, all of which go to intensify sensation, and thus to aggravate the mischief. ”