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LO Dadarp

1. Proses penghantaran impuls fisio anat: simpatis parasimpatis

potensial aksi SSO

(dari berbagai sumber dan web digabung2in *plak , ada yang bilang

dari ganong sama sherwood menurut dafpus webnya ya udah sebut

itu aja, kalo di ganong aku gak tau persis apa gak tapi di sherwood

hampir persis kok *plak)

Didalam otot jantung terdapat jaringan khusus yang menghantarkan aliran listrik, jaringantersebut mempunyai sifat-sifat yang khusus, yaitu sebagai berikut :

1) Otomatisasi : kemampuan menghasilkan impuls secara spontan

2) Ritmisasi : pembangkitan impuls yang teratur3) Konduktifitas : kemampuan untuk menyalurkan impuls4) Daya rangsang : kemampuan untuk menanggapi stimulasi

Komponen-komponen eksitasi dari jantung secara urut terdiri dari:1.Nodus sinoatrium (SA), daerah kecil khusus di dinding atrium kanan dekat lubang venakava superior.2.Nodus atrioventrikel (AV), sebuah berkas kecil sel-sel otot jantung khusus di dasar atriumkanan dekat septum, tepat di atas pertautan atrium dan ventrikel.3.Berkas HIS (berkas atrioventrikel), suatu jaras sel-sel khusus yang berasal dari nodus AVdan masuk ke septum antar ventrikel, tempat berkas tersebut bercabang membentuk berkaskanan dan kiri yang berjalan ke bawah melalui seputum, melingkari ujung bilik ventrikel dankembali ke atrium di sepanjang dinding luar.

4.Serat Purkinje, serat-serta terminal halus yang berjalan dari berkas HIS dan menyebar keseluruh miokardium ventrikel seperti ranting-ranting pohon.

Potensial AksiTerdiri dari 5 fase elektrofisiologi:

1. Fase istirahat- fase 4: pada keadaan istirahat bagian dalam sel relative negative sedangkanbagian luar relative positif. Membrane sel akan lebih permeable terhadap kaliumdibandingkan natrium, karena itu sejumlah kecil ion K akan merembes keluar(dari kadaryang tinggi ke kadar yang rendah K). dengan hilangnya ion K dari intrasel maka bagiandalam sel menjadi relative negative.

2. Depolarisasi cepat- fase 0(upstroke): depolarisasi sel adalah akibat permebilitas membraneterhadap natrium sangat meningkat. Na diluar sel akan mengalir cepat masuk ke dalam sel

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melalui saluran cepat sehingga mengubah muatan negative di sepanjang membrane sel,bagian luar menjadi negative dan bagian dalam menjadi positif.

3. Repolarisasi parsial-fase 1 (spike): segera sesudah depolarisasi maka terjadi sedikitperubahan mendadak dari kadar ion dan timbul suatu muatan listrik relative. Tambahanmuatan negative di dalam sel menyebabkan muatan positif nya agak berkurang. Sebagaiefeknya sebagian sel itu mengalami repolarisasi. Terjadi inaktifasi dari saluran cepat Na.

4. Plateu-fase 2: suatu plateu yang sesuai dengan periode refarkter absolute miokardium. Padafase ini tidak terjadi perubahn muatan listrik melalui membaran sel. Jumlah ion yg keluarmasuk dalam posisi keseimbangan. Plateu terutama disebabkan oleh aliran ion kalsiumkedalam sel secara perlahan dibantu juga oleh gerakan ion Na sedikit demi sedikit melaluisaluran lambat. Gerakan muatan positif ke dalam ini diimbangi oleh gerakan ion K ke luar.

5. Repolarisasi cepat-fase 3(downstroke): selama repolarisasi cepat maka aliran muatankalsium dan natrium ke dalam sel di inaktifkan dan permeabilitas membrane terhadap kaliumsangat meningkat, kalium keluar sel dengan demikian mengurangi muatan positif didalamsel. Bagian dalam sel akhirnya kembali ke keadaan negative dan bagian luar relative positif.Distribusi ion pada keadaan istirahat dipulihkan kembali melalui kegitan kontinyu pompa Na-K yang dengan aktif memindahkan kalium ke dalam sel dan Natrium ke luar sel.

Sistem Saraf Otonom : Simpatik dan ParasimpatikKecepatan denyut jantung dan volume darah dipengaruhi oleh sistem saraf simpatis

dan parasimpatis. Saraf aferen dari saraf glosofaringeal dan saraf vagus membawa pesandari reseptor sensori sinus karotikus dan arkus aorta menuju medula oblongata sebagaipusat regulasi jantung, saraf simpatis dan saraf parasimpatis keluar dari batang otakkemudian memberikan stimulus pada jantung dan melakukan fungsi regulasi saraf simpatis

yang lain. Pusat kardiovaskular di otak berada di formasio retikularis dan terletak di medulaoblongata bagian bawah dan pons. Impuls yang berkaitan dengan tekanan darahdiintegrasikan di sini. Apabila terjadi perubahan tekanan darah, maka pusat kardiovaskularmengaktifkan sistem saraf otonom, sehingga terjadi perubahan stimulasi simpatis danparasimpatis ke jantung dan selanjutnya akan terjadi perubahan stimulasi simpatis keseluruh sistem pembuluh darah. Saraf simpatik dan parasimpatik mengendalikan detakjantung dan kepekaan reseptor cardiopulmonary setelah denervasi karotis dan aorta secaraselektif. 3

Saraf simpatis berjalan di dalam traktus saraf spinalis torakalis menuju korteksadrenal dengan melepaskan neurotransmiter norepinefrin ke sirkulasi untuk membantu aksiregulasi jantung ke nodus SA. Norepinefrin berikatan dengan reseptor spesifik yang disebutreseptor adrenergik B1 yang terdapat di sel-sel nodus SA. Setelah berikatan, terjadipengaktifan sistem perantara kedua menyebabkan peningkatan kecepatan lepas muatannodus dan peningkatan denyut jantung. Kecepatan denyut jantung akan menurun apabila

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pengaktifan saraf simpatis dan pelepasan norepinefrin berkurang. Peningkatan ataupenurunan kecepatan denyut jantung disebut efek kronotropik positif atau negatif. sarafsimpatik, yang memiliki peran yang dominan dalam kontrol kardiovaskular karena pengaruhmereka untuk meningkatkan laju jantung dan kontraktilitas, menyebabkan penyempitanarteri dan vena, penyebab dari pelepasan katekolamin adrenal, dan mengaktifkan sistemrenin-angiotensin-aldosteron. 4

Saraf simpatis juga mempersarafi sel-sel di seluruh miokardium menyebabkanpeningkatan gaya dari setiap kontraksi pada setiap panjang serat otot tertentu. Hal inimenyebabkan peningkatan pada SV dan disebut efek inotropik positif. Saraf parasimpatisberjalan ke nodus SA dan ke seluruh jantung melalui saraf vagus. Saraf parasimpatismelepaskan neurotransmitter asetilkolin yang memperlambat kecepatan depolarisasi nodusSA sehingga terjadi penurunan kecepatan denyut jantung yang disebut efek kronotropiknegatif. Perangsangan parasimpatis ke bagian-bagian miokardium lainnya tampaknyamenurunkan kontraktilitas dan volume darah, menghasilkan suatu efek inotropik negatif.4

Impuls di saraf simpatis noradrenik yang menuju jantung meningkatkan frekuensidenyut jantung (efek kronotropik) dan kekuatan kontraksi jantung (efek inotropik). Impuls-impuls ini juga menghambat efek stimuli vagus, mungkin melalui pelepasan neuropeptida Y,

yakni suatu kotransmiter di ujung simpatis. Impuls dalam serabut kolinergik vagus jantungmengurangi frekuensi denyut jantung. Pada keadaan istirahat, terdapat pelepasan impulstonik di saraf simpatis jantung dalam jumlah sedang, tetapi pada manusia dan hewan besarlainnya terdapat pelepasan impuls tonik dari vagus (tonus vagus) yang cukup besar. Bilavagus hewan percobaan dipotong, frekuensi denyut jantung akan meningkat, dan setelahobat parasimpatolitik seperti atropin diberikan, frekuensi denyut jantung manusia meningkatdari 70, yaitu nilai istirahat normal, menjadi 150-180 denyut/menit karena tidak ada yangmelawan tonus simpatis. Pada manusia dengan hambatan di sistem noradrenergik dankolinergik, frekuensi denyut jantungnya menjadi 100. 7

Sistem saraf simpatis mengontrol tekanan darah melalui mekanisme peningkatancurah jantung dan mempengaruhi tahanan embuluh perifer. Tujuan utama pengontrolan ini

adalah :7

1. Mempengaruhi distribusi darah sebagai respons terhadap peningkatan kebutuhanbagian tubuh yang lebih spesifik akan darah. Misalnya saat melakukan olahraga makadistribusi darah ke sistem pencernaan dialihkan ke bagian tubuh yang terlibat dalamaktivitas tersebut seperti otot rangka dan kemudian panas tubuh dikeluarkan melaluidilatasi pembuluh darah kulit.

2. mempertahankan tekanan arteri rata-rata yang adekuat dengan mempengaruhidiameter pembuluh darah. Sedikit perubahan pada diameter pembuluh dara dapatmenyebabkan perubahan yang bermakna pada tekanan darah. Penurunan volumedarah dapat menyebabkan konstriksi pembuluh darah di seluruh tubuh kecualipembuluh darah yang memperdarahi jantung dan otak. Tujuannya adalah untukmengalirkan darah ke organ-organ vital sebanyak mungkin.

2. Faktor yg mempengaruhi denyut jantung

1)Sex. Women have a slightly faster pulse rate than men.(2) Age. The pulse rate gradually decreases from birth to adulthood thenincreases with advancing old age.(3) Body temperature. The pulse rate generally increases 7-10 beats foreach degree of temperature elevation.(4) Digestion. The increased metabolic rate during digestion will increasethe pulse rate slightly.

(5)Pain. Pain increases pulse rate.

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(6)Emotion. Fear, anger, anxiety, and excitement increase the pulse rate.(7) Exercise. The heart must beat faster during exercise to meet theincreased demand for oxygen.(8) Blood pressure. In general, heart rate and blood pressure have aninverse relationship. When the blood pressure is low, there is an increase in pulse rateas the heart attempts to increase the output of blood from the heart (cardiac output).Sumber:http://armymedical.tpub.com/md0917/md09170024.htm

What Causes High Pulse Rate

There are several causes of this condition. Although, most reasons for high pulse rate aretemporary in nature, a few other factors may elevate the pulse rate for a longer time.

Heart DiseasesMost people who complain of high or rapid pulse rate, often suffer from some or the otherheart disease. Heart ailments such as coronary heart diseases, high blood pressure,

pericarditis etc., are likely to give rise to high pulse rate. The hardening of arteries or thefaulty heart valves lead to difficulty in pumping, thereby increasing the pulse rate.

Thyroid MalfunctionOveractive thyroid gland is known to have some relation with the elevation of pulse rate.Thyroid gland is responsible for controlling the metabolism, in the body. Hence, its overperformance often interferes with the normal metabolism of the body. This, in some waycauses the heart to increase its pumping rate, which eventually leads to a higher pulse rate.Other metabolism related disorders are also likely to cause higher pulse rate.

Faulty Upper Heart ChamberMicroscopic irregularities or any kind of damage in the upper chamber of the heart, results in

higher pulse rate. These irregularities weaken the muscles of the upper heart chambers,thereby putting a lot of strain on the heart. Prolonged consumption of alcohol also causesthe upper chamber of heart to beat at an abnormally higher rate.

EmphysemaEmphysema or chronic obstructive pulmonary disease (COPD) is yet another cause of highpulse rate. In emphysema, the tissues of lungs become non - elastic, which affects thenormal pumping capacity of the heart. This eventually results in rapid heart beating. Smokingis a prime cause of emphysema and other respiratory diseases.Read more at Buzzle: http://www.buzzle.com/articles/high-pulse-rate-causes-of-high-pulse-rate.html

What Affects the Heart Rate?There are a number of different factors that affect the control and response of heart rate.But, what controls the beat of the heart?Neural and Hormonal AffectsThere are two different factors involved in heart rate management: intrinsic and extrinsiccontrols. Intrinsic regulation of heart rate is the result of the unique nature of cardiac tissue -it is self-regulating and maintains it's own rhythm without direction. Extrinsic controls arethose that come from both hormonal responses as well as the commands from the nervoussystem: the central nervous system and the autonomic nervous system. Extrinsic regulationcan cause the heart rate to change rapidly because of chemicals that circular in the blood orby direct action of nerves that go to the heart.A good example of this is to measure heart rate changes when certain words or emotionsare said or felt without a muscle contracting. Say the words, "we are going to have a surprisetest today" and watch heart rate extrinsically increase. Put on a heart rate monitor and sitting

http://armymedical.tpub.com/md0917/md09170024.htmhttp://www.buzzle.com/articles/high-pulse-rate-causes-of-high-pulse-rate.htmlhttp://www.buzzle.com/articles/high-pulse-rate-causes-of-high-pulse-rate.htmlhttp://www.buzzle.com/articles/high-pulse-rate-causes-of-high-pulse-rate.htmlhttp://www.buzzle.com/articles/high-pulse-rate-causes-of-high-pulse-rate.htmlhttp://armymedical.tpub.com/md0917/md09170024.htm

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completely still watch a movie and watch heart rate jump during a car chase or action thriller.There is no cardiovascular or cardio respiratory change as a result of this change in heartrate; it's simply the affect on the heart of chemicals and nerves responding to an externalexperience.The cardiovascular control center for the body is located in the ventro-lateral medulla. Hereheart rate slows if activated by the cardio inhibitory center in the medulla or speeds up ifactivated by the cardio accelerator.From this site, the two channels of the autonomic nervous system originate the sympatheticand parasympathetic components. The sympathetic components increase heart rate byreleasing the neural hormone catecholamines - epinephrine and norepinephrine. Thesehormones are cardio accelerators. Acceleration of the heart rate is called tachycardia.The parasympathetic nervous system located in the brain stem and upper or sacral portionof the spinal cord slows heart rate. The parasympathetic components decrease heart rate.These neurons release the neurohormone acetylcholine, which inhibits heart rate. Theslowing of heart rate is called bradycardia.The combination of the neural and chemical components regulates heart rate and otherheart functions. When you begin to exercise in heart zones 1-3, heart rate increases

because parasympathetic (cardioinhibitory) stimulation stops. During more strenuousexercise, heart zones 3-5, the heart rate increase occurs by direct activation of thesympathetic cardioaccelerator nerves.Exercise excites the relationship between the sympathetic accelerators and theparasympathetic depressor neurons. This change in the balance in their activity called tonicactivity leads to more involvement of the vagus nerves. The vagus nerves carry about 80%of the parasympathetic fibers, those responsible for slowing heart rate. With increased vagaldominance, heart rate values change and slow. One of the training effects is the slowing ofresting and ambient heart rates. This is the result of the effect of fitness on the tonic activityand the favoring of greater activity by the vagus nerves to slow heart rate. These adaptationsfollowing zone 1-3 or aerobic training occur to those who are sedentary and begin andexercise program as well as those who maintain one. This is one of the benefits of training, a

significant resting bradycardia.The central nervous system plays the greatest role in control over heart rate during exercise.When you start a movement pattern, the central nervous system sends impulses through thecardiovascular center in the medulla. There is a coordinated and quick response of both theheart and the blood vessels to change blood pressure, tissue perfusion to respond to therequirements.A good example of the central command involvement is with anticipatory heart rate. Beforean event begins, if the individual anticipates with excitement and enthusiasm the event, heartrate increases dramatically without any muscular involvement. Anticipatory heart rate or yourheart rate immediately before exercising in one experiment averaged 148 bpm when theannouncer started giving starting commands to a group of sprinters. In this experiment, heartrates increased 140% in anticipation of the starting of this 60-yard dash. In fact, the body

that the body increases heart rate in anticipation is good because it provides for the rapidmobilization of it's bodily reserves by revving the body's engine. Research shows that thelonger the event, the lower the anticipatory heart rate changes.Internal Body ChangesAlmost any substance taken into the body affects the equilibrium of the comanism. Heartrate is one of the quickest changes that occur as a direct reflection of this change that resultsin disequilibrium. For example, beta blockers (Inderal, Propranolol, Lopressor, etc.) causebradycardia or the heart rate to drop. Similarly, the antiarrhythmic agents (Cardioquin,Procaine, Quinidine, etc.) given to patients to improve cardiac function also causes adecrease in heart rate. Pulmonary bronchodilator drugs such as the sympathomimetics(Isoproterenol, Ephedrine, Bronkosol, etc.) cause tachycardia or increase in heart ratevalues. Drugs that act as stimulants such as caffeine, nicotine, methamphetamines, cocaine,PCP cause tachycardia and drugs that are depressants, barbiturates, tranquilizers, alcohol

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and quaaludes cause bradycardia. Some drugs like inhalants can cause either a quickeningor depressing of heart rate and respiration.Other changes can cause changes in heart rate. Lack of sleep, irritability, rapid changes inblood chemistry such as blood sugar levels, reactions to different types of ingested foodscan both lower and raise resting and exercising heart rates. Emotions play a large role inheart rate response. Anger, fear, and anxiety cause tachycardia while depression usuallyresults in lowering of heart rate. Feelings of love, compassion, happiness usually result inbraycardia. Emotional stress causes heart rate to stay elevated.Environment StressesHeart rate is affected by external stresses on the body such as heat, humidity, cold, wind,and altitude and air quality. With each stress, the human heart is affected and differentcompensatory changes occur, one of those being adjustment in the beat of the heart.Triathletes racing at the Hawaiian Ironman face most of these conditions simultaneouslywhile racing in one of the most strenuous events in the world. As a result, a heart ratemonitor can help provide them with key information on how their body is responding to theconditions and the duration of this high intensity racing throughout the event.The following chart shows the affects on heart rate of certain environmental stresses:

Type ofStress

SpecificStress

Heart RateChanges

Explanation

ThermalStress

Heatgain*

Elevated

Changes in heart rate are the result of changes in the corebody temperature. Dressing appropriately is the mostimportant consideration to maintain the bodies core

temperature. Dehydration causes heart rate to increase.

Heat loss Lowered

Thermoregulation adjustments result in improved exercisecapacity to heat exposure but minimally to cold stress. Thisgenerally takes about 10 days. Shivering can increase the

heart rate significantly to increase core temperature.Considerable water can be lost from the respiratory tractduring cold exposure when exercising which results in

elevated heart rates (dehydration effect on heart rate).

Humidity Dry Air Elevated

The water content in the ambient air affects the amount ofwater lost through sweating. In dry air, sweating can beprofuse and decrease in blood volume from dehydration

substantial. Each 1 pound of body weight loss corresponds to15 ounces (450 mL) of dehydration. Hot dry climates are

easier than humid ones because evaporation of sweat, whichcools the skin, can be achieved.

Highly

moist air

Elevated

Exercising in high humidity challenges the thermoregulatorysystem because the large sweat loss contributes little to

evaporative cooling. Sweat does not cool the skin; evaporation

of sweat cools the skin. Heart rate response is to increaseblood flow to the skin for sweating therefore increasing heart

rate.

WindWindChill

Lowered andElevated

Wind caused by physical movement or air movementmagnifies heat loss as the warmer insulating air on the skin iscontinually replaced by cooler, ambient air. Wind causes heat

to decrease and hence heart rate to stay lower. Wind chillfactor is an index that shows the effect of wind velocities on

bare skin for different temperatures.

Altitude High

Loweredmaximum and

training heartrates

There is a progressive reduction in the amount of oxygen andits partial pressure as altitude increases. As a result, the heart

beats faster to compensate for less oxygen per breath.

Maximum heart rate drops with increases in altitudeapproximately one beat per 1,000 feet of gain. There is some

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relief from the acclimatization process, which result inimproved tolerance to altitude hypoxia.

* Same response to thermic effect of foodGeneticsThe genes that you inherited are responsible for much in our lives. They too affect heart

rates. It appears that the effect of your genetic makeup accounts for about 50% of the valueof your maximum heart rate. This means that if your parents both have a low maximum heartrate, the odds are favorable that you will as well.Protection from the degenerative process of heart diseaseThe state of fatigue or rest of the individual also affects heart rate. If a student is physicallytired from over-exercising there is a decline in physiological performance. Overtraining is acomplex series of conditions which can include nutrient-fatigue, muscle-fatigue, andneuromuscular-fatigue. Heart rate is affected differently by different kinds of fatigue.Heart rate is not affected by body composition. It's not affected by body type. It is affected byheart size with smaller hearts typically having higher resting and ambient heart rates.Fitness LevelThe fitter you are the less often your heart contracts thus saving heartbeats. Getting fitter is

like putting money into your saving account, it's putting heartbeats into your physiologicalsaving account. Through the phenomenon of the training effect, ambient and resting heartrates drop, by as much as 20-30 bpm. When extended over a lifetime, this can equate tohundreds of millions of heartbeats.The athlete's heart as the fit cardiac muscle is sometimes referred to is different than thesedentary individuals cardiac pump. There are structural and dimensional changes to thehearts of athletes, which reflect the specific training demands. The effects of getting a fitheart leads to cardiac hypertrophy, a muscle adaptation as a result of increased workcapacity. That is, there is a moderate increase in heart size and anatomies regardless of ageas the result of an aerobic and anaerobic training program. Here's a list of changes thathappen to the fit, athletic heart muscles: Improved cardiac output Lower resting and ambient heart rates Increased stroke volume Enlarged ventricular chamber Thickening of the heart walls Improved coronary blood flow Improved mitochondria mass Increase number of respiratory enzymes in the

myocardiumMode of ExerciseMany factors affect maximum and training heart rates. The type of exercise is singularly oneof the most significant. Maximum heart rate is mode specific. Anaerobic threshold heart ratesare also mode specific. The greater the quantity of muscle mass that is used for theexercise, the higher the training heart rates attained. The highest heart rate numbers arethose from sports which use both lower and upper muscle groups simultaneously such ascross country skiing. The lowest are those in which the body is in a horizontal position or incool temperatures such as swimming.Heart rate and changes in heart rate are affected by many factors. Each can result in heartrate variability depending multiple factors that might be simultaneously interacting. Forexample, a student might be on medication, fatigued, doing a different form of exercise, afternot sleeping, just eating a big complex carbohydrate meal, suffering from stress, de-conditioned, living at altitude, in high relative humidity, and it's the day before their birthdayand they just returned from a long trip. In combination, these factors can make a big day-to-day variation in heart rate.That's even more of a reason to use a heart rate monitor. It's a management tool. The heartmuscle takes all of these situations and conditions into account when it sets the frequency of

the beat. Both the heart muscle and the heart monitor are powerful - use them both,together.http://www.heartmonitors.com/exercisetips/changing_heartrate.htm

http://www.heartmonitors.com/exercisetips/changing_heartrate.htmhttp://www.heartmonitors.com/exercisetips/changing_heartrate.htm

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3. Fungsi denyut jantung lebih cepat