Copyright © Philip M. Parker, INSEAD. Terms of Use.
Definition: Pacemaker |
PacemakerNoun1. A specialized bit of heart tissue that controls the heartbeat. 2. An implanted electronic device that takes over the function of the natural cardiac pacemaker. 3. A horse used to set the pace in racing. Source: WordNet 1.7.1 Copyright © 2001 by Princeton University. All rights reserved. |
Date "pacemaker" was first used in popular English literature: sometime before 1912. (references) |
| Domain | Definition |
Health | An object or substance that influences the rate at which a certain phenomenon occurs; often used alone to indicate the natural cardiac pacemaker or an artificial cardiac pacemaker. In biochemistry, a substance whose rate of reaction sets the pace for a series of interrelated reactions. (references) |
Medicine | Body part that serves to establish and maintain a rhythmic activity ; a small mass of tissue made up of fibers, ganglion cells embedded in the musculature of the right auricle of higher vertegrates serving as a pacemaker to the heart. Source: European Union. (references) |
| A center or a substance that controls the rhythm of a body process; the term usually refers to the cardiac pacemaker. Source: European Union. (references) | |
Source: compiled by the editor from various references; see credits. | |
(From Wikipedia, the free Encyclopedia)
A pacemaker (or "artificial pacemaker", so as not to be confused with the heart's natural pacemaker) is a medical device designed to regulate the beating of the heart. External pacemakers can be used for initial stabilization of a patient, but implantation of a permanent pacemaker is usually required for most conditions.
Pacing can be instituted for many reasons: in the case of slow ventricular rate (bradycardia, heartblock) or rapid ventricular rate (atrial fibrillation or atrial flutter) or when dangerous arrhythmias are noted when the EKG is monitored.
The first pacemaker was designed and built by the Canadian electrical engineer John Hopps in 1950, a substantial external device it was somewhat crude and also painful to the patient in use. A number of inventors, including Paul Zoll, made smaller but still bulky devices in the following years. The first true implantable pacemaker was completed in 1958 by the American Wilson Greatbatch, who made the first transistorized device. He had patented the idea some five years earlier.
The first implantation into a human was made in 1958 by a Swedish team using a pacemaker invented by Rune Elmqvist and Åke Senning. The device failed after three hours.
Devices constructed by Greatbatch began being implanted in humans from April 1960 following extensive animal testing. The first patient lived for a further 18 months. The early devices suffered from battery problems - every patient required an additional operation every 24 months to replace the batteries.
The first American-made nuclear powered pacemaker was developed and implanted at Newark Beth Israel Medical Center in Newark, New Jersey.
When first invented, pacemakers controlled only the rate of speed at which the heart's two largest chambers, the ventricless, beat.
More recently, pacemakers which control not only the ventricles but the atria as well have become common. Timing the contractions of the atria to precede that of the ventricles improves the pumping efficiency of the heart and can be useful in congestive heart failure.
Sometimes devices resembling pacemakers, called ICDs (implantable cardioverter/defibrillators] are implanted. These devices have the ability of sensing dangerous rhythm disturbances and then shocking the heart back into a normal rhythm.
See also
- cardiology
Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Artificial pacemaker."
(From Wikipedia, the free Encyclopedia)
The contractions of the heart are controlled by electrical impulses, these fire at a rate which controls the beat of the heart.The cellss that create these rhythmical impulses are called pacemaker cells, and they directly control the heart rate. Artificial devices also called pacemakerss can be used after heart failure to produce these impulses synthetically.
Control via the SA node
Although all of the hearts cells possess the ability to generate these electrical impulses, (or action potentials), a specialised portion of the heart, called the sinoatrial node (SA node), is responsible for the whole heart's beat.The sinoatrial node is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava. These cells are modified cardiac myocytes. They possess some contractile filaments, though they do not contract.
These cells will naturally discharge action potentials at about 70-80 times/minute. Because the sinoatrial node is responsible for the rest of the heart's contractions, it is sometimes called the primary pacemaker.
If, for some reason, the sinoatrial node doesn't function, a group of cells further down the heart will become the heart's pacemaker. These cells form the AV node, which is an area between the atria and ventricles, within the atrial septum.
These cells normally discharge at about 40-60 beats per minute, and are called the secondary pacemaker.
Further down the electrical conducting system of the heart, the Bundle of His, the left and right branches of this bundle, and the Purkinje fibres, will also produce a spontaneous action potential. These tertiary pacemakers fire at a rate between 30-40 per minute.
Even individual cardiac muscle cells will contract rhythmically on their own.
The reason the SA node controls the whole heart, is that its action potentials are released first, this triggers other cells to generate their own action potentials. In the muscle cells, this will produce contraction. The action potential generated by the SA node, passes down the cardiac conduction system, and arrives before the other cells have had a chance to generate their own spontaneous action potential.
Generation of action potentials
There are three main stages in the generation of an action potential in a pacemaker cell. Since the stages are analogous to contraction of cardiac muscle cells, they have the same naming system. This can lead to some confusion. There is no phase one or two, just phases zero, three and four.
Phase 4 - Pacemaker potential
The key to the rhythmical firing of pacemaker cells is that, unlike muscle and neurons, these cells will slowly depolarise by themselves.As in all other cells, the resting potential of a pacemaker cell (-60mV to -70mV) is caused by a continuous outflow or "leak" of potassium ions through ion channel proteins in the membrane that surrounds the cells. The difference is that this potassium permeability decreases as time goes on, partly causing the slow depolarisation. As well as this, there is an slow inward flow of sodium, called the 'funny' current. This all serves to make the cell more positive.
This relatively slow depolarisation continues until the threshold potential is reached. Threshold is between -40mV and -50mV. When threshold is reached, the cells enter phase 0.
Phase 0 - Upstroke
Though much faster than the depolarisation caused by the funny current and decrease in potassium permeability above, the upstroke in a pacemaker cell is relatively slow compared to that in an axon.The SA and AV node do not have fast sodium channels like neurons, and the depolarisation is mainly caused by a slow influx of calcium ions. (The funny current also increases). The calcium is let into the cell by voltage-sensitive calcium channels, that opened when the threshold was reached.
Phase 3 - Repolarisation
The calcium channels are rapidly inactivated, soon after they opened. Sodium permeability is also decreased.Potassium permeability is increased, and the efflux of potassium (loss of positive ions) slowly repolarises the cell.
Control of heart rate
The heart gets its parasympathetic innervation from the vagus nerve. Signals from this nerve cause the heart rate to decrease.Sympathetic stimulation comes from the cardiac nerves from the sympathetic chain. Activity in these nerves acts to increase heart rate.
Sympathetic stimulation
When the SA node receives sympathetic stimulation, noradrenaline released from the nerve endings binds to β1-adrenergic receptors on the pacemaker cell membrane.This binding causes cyclic AMP production within the cell. This directly increases the funny current, meaning sodium is continually entering the cell more quickly. Cyclic AMP also activates a protein kinase, that phosphorylates the calcium channels, increasing calcium conductance into the cell.
Because both sodium, and calcium can enter the cell more quickly, the continuously natural depolarisation (phase 4) reaches threshold more quickly. So action potentials are generated more frequently.
It takes a while for the heart rate to increase after noradrenaline is released.
Parasympathetic stimulation
Acetylcholine (ACh) is released from the vagus nerve endings, and binds to muscarinic receptors on the pacemaker cells.In the pacemaker cells, there are ACh sensitive potassium channels. These open in response to ACh binding, potassium ions leak out, and the cell gets hyperpolarised (more negative). The funny current is also reduced by ACh. This means sodium ions enter more slowly, and it takes longer for the cell to reach threshold. Thus the heart rate slows.
Unlike in the sympathetic mechanism, the heart will slow quite soon after vagal stimulation.
Hormonal effects
Noradrenaline and adrenaline are both released into the bloodstream by the adrenal medulla.They have the same action on heart rate as direct sympathetic stimulation.
Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Cardiac pacemaker."
(From Wikipedia, the free Encyclopedia)
A pacemaker is a competitor who enters an athletics race with little or no intention of winning, but purely to set a fast pace for other competitors to follow.The heart pacemaker is a group of cells within the heart that together initiate contractions and set the pace of beating. For most people, this is a group of cells in the right atrium of the heart, otherwise known as the sinoatrial node.
Also related to the heart, "pacemaker" is the common term for an implantable artificial pacemaker device, which was developed by Wilfred Bigelow, John A. Hopps, and J. C. Callahan.
Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Pacemaker."
Synonyms: PacemakerSynonyms: artificial pacemaker (n), cardiac pacemaker (n), pacer (n), pacesetter (n), sinoatrial node (n). (additional references) |
Crosswords: Pacemaker |
| English words defined with "pacemaker": artificial pacemaker. (references) |
| Specialty definitions using "pacemaker": atrial inhibited, atrial triggered, automaticity ♦ Cardiac Pacing, Artificial ♦ demand inhibited ♦ endless loop tachycardia ♦ fixed-rate ♦ lead connector ♦ modulating pacemaker ♦ pacemaker artifact, pacemaker dependency, pacemaker system, pacemaker unit, pacemaker-mediated tachycardia, pacer dependency, pacing system, Parasystole, physiologic pacing ♦ rate-adaptive, rate-modulated, rate-modulating, rate-responsive, responsive pacemaker ♦ self-inhibition, sensor-driven, sinus node, stimulus artifact ♦ Twiddler's syndrome ♦ ventricular demand. (references) |
| Non-English Usage: "Pacemaker" is also a word in the following languages with English translations in parentheses. Danish (pacemaker), Dutch (pacemaker), German (pacemaker), Hungarian (pacemaker), Italian (pacemaker), Portuguese (pacemaker), Swedish (pace-maker). |
| Domain | Usage | |
Screenplays | I've got to go have my pacemaker checked, it has been so exciting talking to you. (Absolute Power; writing credit: William Goldman) | |
Source: compiled by the editor from various references; see credits. | ||
| Domain | Title | ||
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Source: compiled by the editor from various references; see credits. | |||
| Thumbnail | Description & Credit |  | A pacemaker to prevent heart block is being passed into the patient's right ventricle ... / WHO p. Credit: National Library of Medicine; photo by T. Farkas.. |
Source: pictures compiled by the editor from various references; see picture credits. | |||
| Subject | Topic | Quote |
Health | Then, other treatment, such as a pacemaker or surgery, may be needed. (references) | |
The pacemaker can reduce the degree of obstruction and so relieve symptoms. (references) | ||
Cardiac abnormalities may be treated with various cardiac drugs or a pacemaker. (references) | ||
Economic History | Canada | Class I represents devices that pose the least risk, such as a bandage, while Class IV devices pose the highest risk (for example, a pacemaker). (references) |
Source: compiled by the editor from ICON Group International, Inc.; see credits. | ||
| "Pacemaker" is generally used as a noun (singular) -- approximately 100.00% of the time. "Pacemaker" is used about 44 times out of a sample of 100 million words spoken or written in English. Its rank is based on over 700,000 words used in the English language. Some parts-of-speech are not covered due to the samples used by the British National Corpus. (note: percents less than one-hundredth of one percent have been omitted) |
| Parts of Speech | Percent | Usage per 100 Million Words | Rank in English |
| Noun (singular) | 100% | 44 | 51,500 |
Source: compiled by the editor from several corpora; see credits.
Expressions using "pacemaker": artificial pacemaker ♦ cardiac pacemaker ♦ heart pacemaker ♦ pacemaker artifact ♦ pacemaker dependency ♦ pacemaker patient ♦ pacemaker system ♦ pacemaker unit. Additional references. | |
| Hyphenated Usage | |
Beginning with "pacemaker": pacemaker-mediated. | |
| Source: compiled by the editor from various references; see credits. | |
| The following statistics estimate the number of searches per day across the major English-language search engines as identified by various trade publications. Hyperlinks lead to commercial use of the expression at Amazon.com. |
| Language | Translations for "pacemaker"; alternative meanings/domain in parentheses. | |
Albanian | stimulues kardiak (pacer), mbajtës i ritmit (pacer). (various references) | |
Arabic | منبه قلبي, محدد الخطوة, قائد (chief, commandant, commander, head, leader, pacesetter, professor, skipper, soul), زعيم (bell wether, boss, captain, chief, cob, elder, head, leader, primate, ruler), القدوة (example). (various references) | |
Bulgarian | изкуствен водач на сърцето (pacer). (various references) | |
Chinese | 心脏起搏器. (various references) | |
Czech | vodiè závodníka (pace-maker), kardiostimulátor. (various references) | |
Danish | pacemaker (pace-maker, sinoatrial node, sinus node). (various references) | |
Dutch | pacemaker (pace-maker). (various references) | |
Farsi | پیشقدم (Pioneer, Protagonist, Trail, Trailblazer, Van), سرمشق (Example, Lead, Model), راهنما (Adviser, Clue, Conductor, Guidance, Guide, Guideline, Key, Keyword, Landmark, Leader, Lodestar, Polestar, Signal, Usher), دستگاه تنظیم کننده ضربان قلب . (various references) | |
French | stimulateur cardiaque (pace-maker). (various references) | |
German | schrittmacher (pace maker, pacer, pacesetter). (various references) | |
Greek | βηματοδότης (pace-maker). (various references) | |
Hebrew | מצעי", קוצב לב, קוצב (determinant, pacesetter). (various references) | |
Hungarian | pacemaker, szívritmusszabályzó, szívütem-szabályozó, edzõ (coach, trainer). (various references) | |
Italian | pacemaker (pace-maker, pacemaker system, pacemaker unit, pacer, pacing system, pulse generator). (various references) | |
Japanese Kanji | ページ組み (concentration of hydrogen ions, pace, paging, paper, paper chromatography, paper company, paper holder, paper plan, paperback, papercraft, paste, pathos, person with driving licence but no practice, pest, pH, written test). (various references) | |
Japanese Katakana | ペースメーカー . (various references) | |
Manx | fer bieauid. (various references) | |
Pig Latin | acemakerpay.(various references) | |
Portuguese | precursor (forerunner, harbinger, herald, pacesetter, pioneer, precursory, trail-blazer), pacemaker, marca-passos, marcapasso cardíaco, estimulador cardíaco (pace-maker), aparelho do tipo "pacemaker" (pace-maker). (various references) | |
Russian | синусовый узел сердца, водитель ритма, задающий темп (pacer). (various references) | |
Serbo-Croatian | pejsmejker (pace-maker), vođa (guide, head, leader), sinusni čvor srca, davalac tempa (pace-maker). (various references) | |
Spanish | marcapasos. (various references) | |
Turkish | yarışta hızı ayarlayan kimse (pacer), kâlp temposunu ayarlayan alet, kâlp pili. (various references) | |
Ukrainian | синусний вузол серця, лідер (center, centre, chief, coryphaeus, leader, pacer, pace-setter). (various references) | |
| Source: compiled by the editor from various translation references. | ||
| Language | Period | Translations |
| Latin | 500 BCE-Modern | No Translation. (various references) |
| Source: compiled by the editor from various references. | ||
Derivations | |
Words beginning with "pacemaker": pacemakers. (additional references) | |
| |
"Pacemaker" is suggested in spellcheckers for the following: pagemaker. (additional references) | |
| Source: compiled by the editor, based on several corpora (additional references). | |
| # of Phoneme Matches | Pronunciation | Word(s) rhyming with "pacemaker" (pronounced pā"smā'ker) |
| 5 | -s m ā' k er | dressmaker, glassmaker, peacemaker. |
| 4 | -m ā' k er | drugmaker, automaker, boilermaker, carmaker, filmmaker, hatmaker, haymaker, homemaker, Kingmaker, lawmaker, matchmaker, moneymaker, moviemaker, newsmaker, oddsmaker, printmaker, rainmaker, shoemaker, steelmaker, toolmaker, troublemaker. |
| 3 | -ā' k er | caretaker, icebreaker, lawbreaker, Muckraker, strikebreaker, undertaker. |
Source: compiled by the editor (additional references); see credits. | ||
Scrabble® Enable2K-Verified Anagrams | |
| Words within the letters "a-a-c-e-e-k-m-p-r" | |
-1 letter: capmaker. | |
-2 letters: camerae. | |
-3 letters: amerce, ampere, camera, camper, packer, pecker, raceme, remake, repack. | |
-4 letters: ackee, ameer, apace, apeak, apeek, areae, areca, caper, crake, cramp, crape, creak, cream, creek, creep, creme, crepe, karma, kreep, macer, makar, maker, pacer, parae, parka, peace, perea, praam, rakee, ramee, recap, remap. | |
-5 letters: acme, acre, akee, aper, arak, area, cake, came. | |
| Words containing the letters "a-a-c-e-e-k-m-p-r" | |
+1 letter: pacemakers, peacemaker. | |
+2 letters: marketplace, peacemakers. | |
+3 letters: marketplaces. | |
| Source: compiled by the editor from various references; see credits. SCRABBLE® is a registered trademark. All intellectual property rights in and to the game are owned in the U.S.A and Canada by Hasbro Inc., and throughout the rest of the world by J.W. Spear & Sons Limited of Maidenhead, Berkshire, England, a subsidiary of Mattel Inc. Mattel and Spear are not affiliated with Hasbro. | |
| 1. Definition 2. Synonyms 3. Crosswords 4. Usage: Modern | 5. Usage: Commercial 6. Images: Photo Album 7. Quotations: Non-fiction 8. Usage Frequency | 9. Expressions 10. Expressions: Internet 11. Translations: Modern 12. Translations: Ancient | 13. Derivations 14. Rhymes 15. Anagrams 16. Bibliography |
Copyright © Philip M. Parker, INSEAD. Terms of Use.
