The cardiovascular system

Structure of the heart

The cardiac cycle

Structure and organization of blood vessels

Pandangan Umum Sistem KardiovaskulerSistem kardiovaskular mempunyai perananan yg sangat penting dalam proses homeostasis agar tubuh dapat beradaptasi terhadap berbagai perubahan yang terjadi dilingkungan sekitar kita. Fungsi sistem kardiovaskulerPenyediaan berbagai bahan nutrisi dan oksigen ke sel dan jaringan dan membuang hasil metabolisme.

Transport berbagai bahan dari suatu organ keorgan lainnya, misal hormon, enzim dan berbagai antibodi dan sitokin yang diperlukan untuk pertahanan tubuh terhadap mikroorganisme

Mengatur keseimbangan caitan tubuh melalui pengaturan konsentrasi air dan ion pada sel dan jaringan

Fungsi lain dari jantung :> Sebagai organ endokrin dengan menghasilkan berbagai hormonHormon ANP, adrenomedullin, dan oksitosin

Struktur anatomik jantungJantung terletak di dalam rongga mediastinum dari rongga dada (toraks), diantara kedua paru.Bagian atas ICS 2, garis sternum, ICS 4 dan garis axila anterior

Dinding jantung 3 lapisan :Lapisan luar disebut epikardium (perikardium viseralisLapisan tengah miokardiumLapisan dalam endokardium

Ruang-ruang jantung Atrium kananAtrium kiri Ventrikel kanan Ventrikel kiri

Katup-katup jantung Katup atrioventrikulerKatup Trikuspidalis Katup Mitralis Katup semilunar Katup aorta Katup pulmonal

Sistem Konduksi Kontraksi otot-2 jantung secara spontan & ritmik.Sifat-sifat :1. Otomatisasi: impuls secara spontan2. Ritmisasi: impuls secara teratur3. Konduktivitas: menyalurkan impuls4. Daya rangsang: menanggapi stimulasi

Karena sifat-sifat ini menghasilkan secara spontan & ritmis impuls yg disalurkan melalui sistem penghantar utk merangsang miokardium & menstimulir kontraksi otot.

Sirkulasi Koroner Efisiensi jantung sbg pompa ~ nutrisi & oksigenasi.Sirkulasi koroner membawa O2 & nutrisi ke miokardiumMorbiditas & mortalitas infark miokard ~ derajat gangguan fungsi mekanik ataupun elektrik.

Nodus SA (sinoatrial)- Pemicu alami jantung- Letak: dinding post. A.Ka dekat muara VCS- Jalur antaratrium (berkas Bachmann) mempermudah penyebaran impuls dari A.Ka ke A.KiJalur internodal menghub. nodus SA dgn nodus AV.

Nodus AV (atrioventrikular)- Letak: septum interventrikularis dlm A.Ka dekat muara sinus koronaria- Memiliki 2 fungsi:a. Menunda impuls jantung selama 0,08 0,12 detik guna memungkinkan pengisian ventrikel selama kontraksi atrium.b. Mengatur jumlah impuls atrium yg mencapai ventrikel; biasanya tidak lebih dari 180 impuls/mnt.

Berkas His Suatu berkas serabut yg tebal yg menjulur ke bawah di sebelah kanan septum interventrikularis. Berkas ini membelah menjadi cabang kiri dan kanan.

Serabut purkinje Cabang-cabang tsb di atas berakhir sbg jalinan serabut kompleks yg disebut sistem purkinje, yg menyebar ke seluruh permukaan kedua ventrikel jantung.Terdapat susunan sel-sel miokard (di luar sistem konduksi) ikut berperan dalam kecepatan penyebaran impuls. Sel-sel ini dipisahkan oleh duktus interkalaris. Dalam diskus ini terdapat tempat-tempat membran sel saling berdekatan neksus. Neksus ini mempercepat transmisi rangsangan listrik.

FAKTOR PENENTU CURAH JANTUNGCurah jantung tergantung pada :1. Frekuensi Jantung (heart rate)Parasimpatis bradikardi (resting)Simpatis takikardi (heart disease)

2. Curah sekuncup (stroke volume)a. Beban awal (preload)b. Kontraktilitasc. Beban akhir (afterload)Hukum Starling: peregangan serabut miokard selama diastol melalui peningkatan volume akhir diastol meningkatkan kontraktilitas pada saat sistolik. SIRKULASI SISTEMIK (peredaran darah besar)Ventrikel kiri aorta arteri besar arteri kecil arteriola kapiler arteri kapiler vena venula vena kecil vena besar vena cava inferior dan vena cava superior atrium kanan (jantung menuju seluruh tubuh)

SIRKULASI PULMONAL (peredaran darah kecil)Ventrikel Kanan arteri pulmonal paru (alveoli) vena pulmonal atrium kiri

SIRKULASI SISTEMIKMerupakan peredaran darah dari jantung menuju seluruh jaringan tubuh dan kembali lagi ke jantung.Darah dipompakan dari ventrikel kiri keluar jantung melalui aorta menuju ke 2 cabang aorta yang berukuran pendek, satu cabang mengalirkan darah yang kaya akan oksigen ke bagian kepala dan lengan dan cabang lainnya mengalirkan darah ke berbagai bagian tubuh lainnya.Peredaran darah sistemik bertanggung jawab terhadap berlangsungnya pertukaran gas , nutrien, limbah pada semua bagian tubuh kecuali paru-paru.Kemudian darah yang miskin oksigen dari bagian kepala dan lengan akan kembali masuk jantung melalui vena cava superior dan darah yang berasal dari bagian tubuh lainnya masuk jantung melalui vena cava inferior.

SISTEM PEREDARAN DARAH PULMONALPeredaran darah pulmonary merupakan peredaran darah dari jantung ke kapiler paru-paru kemudian kembali ke jantung.Darah dari paru-paru mengalir melalui arteri pulmonari dan kembali ke jantung melalui vena pulmonari

What is the cardiovascular system?

The heart is a double pump

heartarteries arterioles veinsvenules capillaries

The double pump

Serous membraneContinuous withblood vessels

Chambers of the heart; valves

Valves control flow of blood from onechamber to another

Prevent backflow

Blood supply to the heart

Coronary artery and vein system

Right and left coronary arteries branch off ofaortaBranch into smaller vessels

Cardiac veins deliver blood to coronary sinus,and back to the right atrium

Coronary artery disease results when coronaryarteries cannot deliver blood adequately

Usual cause: plaques in arterial walls

Angina pectoris (pain) when body is notreceiving adequate oxygen

Myocardial infarction (heart attack) whenblood supply to heart is completelyblocked; muscle dies

Coordination of chamber contraction, relaxation

Conduction system of the heart

Heart contracts as a unit

Atrial and ventricular syncytia help conductelectrical signals through the heart

Sinoatrial (S-A) node is continuous with atrialsyncytium

S-A node cells can initiate impulses on theirown; activity is rhythmic

Electrocardiogram (ECG) can trace conductionof electrical signals through the heart

Aberrant ECG patterns indicate damage

Regulation of heart rate

Blood pressure and its control

What is hypertension and how is it treated?

The heart rate and exercise

Characteristics of arteries and veins

Organization of the vascular system andresponses to physiological needs

Regulation of the cardiac cycle

Sympathetic and parasympathetic nervoussystems

Parasympathetic: from medulla oblongata(vagus nerve)Nerve branches to S-A and A-V nodes, andsecretes acetylcholine (slows rate)

Parasympathetic activity can increase (slowheart rate) or decrease (increase heartrate)

Sympathetic nervous systemthrough celiac plexus to heartsecretes norepinephrineincreases force of contractions

Cardiac control center in medulla oblongatamaintains balance between the two

Normally both sympathetic and parasympatheticfunction at a steady background level

Baroreceptors detect changes in blood pressure

Rising pressure stretches receptorsvagus nerveparasympathetic system

Increased temperature increases heart rate

Ions and heart rate:excess potassium decreases it

excess calcium increases it

Blood pressure

Blood flow is generally equal to cardiac output

Blood flow affected by pressure and resistance

Blood pressure: the force that is exerted by bloodagainst blood vessel walls

Resistance depends on size of blood vessel andthickness (viscosity) of blood

Blood pressure is highest in large arterieswill rise and fall as heart pumps

highest with ventricular systolelowest with ventricular diastolepulse pressure is the difference betweenthe two

Resistance is highest in capillaries

More cellsconstriction of bloodvessel walls

Control of blood pressure

Regulation of cardiac outputcontraction strengthheart ratevenous returnskeletal musclesbreathing rate

Long term regulation of blood flow (hormones)

If blood pressure is too low:

ADH (antidiuretic hormone) promotes waterretention

Angiotensin II- in response to reninsignal (renin) produced by kidney- why?drop in blood pressurestimulation by sympathetic nervoussystemsodium levels too low

What happens?vasoconstriction (by angiotensin II)what will that do to blood pressure?ADH is secretedaldosterone is secreted

EPO (erythropoietin) secreted by kidneysif blood volume is too low

ANP secreted if blood pressure is tooHIGH

What is hypertension?

Arterial pressure is too high

Sometimes cause is unknown, or is secondaryto diseaseVariety of causes/ risk factors are knownsedentary lifestylesmokingobesitydiet (excess sodium; cholesterol; caloriesin general)stressarteriosclerosisgenetic factors

Consequences?heart has to work harder; left ventricleenlargesatherosclerosis may affect coronaryarteries as well (which have to work harderanyway) heart disease

deficient blood supply to other parts ofbody

damage to blood vessels accumulates

heart failure

Treatment of high blood pressure

Quit smoking; adjust diet; exercise

Drug therapies- strategies differ

Reduce heart ratecalcium channel blockersreduce calcium flow into heartmuscle and therefore heart raterelax smooth muscle liningcoronary arteriesbeta blockers (reduce stimulation bysympathetic nervous system)

Diuretics reduce blood volumeACE inhibitors interfere with renin-angiotensin pathway

Vasodilators (such as nitroglycerin) open upblood vessels (reduce resistance)

If heart is actually failing, digitalis increasesefficiency of heat muscle

Anti-hypertensive drugs may be taken incombination

Why is exercise good for the heart?

A trained heart is biggerpumps blood more efficiently (at a lowerrate)stroke volume increases (due to strongercontractions, allowing for lower rate)

other benefits: higher aerobic capacity(contributing to efficiency)

Note that this takes training!

Characteristics of blood vessels

Arteries and arterioles carry blood away fromheart

Capillaries- site of exchange

Venules, veins- return blood to heart

Endothelium- prevents platelet aggregationsecretes substances that control diameterof blood vessel

Tunica media- smooth muscle and connectivetissue. Innervated by sympathetic nerves(vasoconstriction)Missing in smallest arteries

Tunica externa- connective tissue; isvascularized

Capillaries most permeable (and more permeablein some parts than others)

Especially so in liver, spleen and red marrow(so cells can enter and leave circulation)

Blood flow can vary to different parts of the body, too

What does this mean?

Blood is forced through arteries and arteriolesvessel walls are too thick for blood com-ponents to pass through

In capillaries, oxygen and nutrients move outby diffusion; CO2 in (via lipid membrane,channels, etc.)

Blood pressure moves molecules out by filtration

Plasma proteins maintain osmotic pressureof blood

Returning blood to the heart

Venules are continuous with capillaries; takein some returned fluid (rest is retained bytissues or returned to blood via lymphaticsystem)

Veins have thinner walls;less muscle; but can hold much more blood

Many veins in limbs have valves to preventbackflow(Varicose veins arise when pressure on valvesis prolonged)

See pp. 351-359 for allcircuits

Summary

The heart is a double pump, delivering bloodto the lungs for oxygenation, and thento the body

Blood leaves the heart through arteries, andreturns to the heart through veins

The heart rate is regulated by a conducting system (the heart beats about 100,000times per day!)

The cardiac cycle is regulated by the cardiaccenter in the medulla oblongata whichregulates sympathetic and parasympa-thetic input

Exercise (i.e., needs), temperature and ionbalance also affect heart rate

Cardiac rate is also controlled by long-termresponders such as ADH, angiotensin,EPO and ANP

Blood (arterial) pressure is affected by heartaction, blood volume, peripheralresistance, and blood viscosity

Inability to regulate blood pressure can contribute to disease

Arteries and veins have structural characteristicsappropriate to bringing blood to the cellsand then back to the heart

Circulatory system allows for adjustments to exercise, digestion and other necessaryfunctions