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Function of theCardiovascular system

Departemen Fisiologi

Fakultas Kedokteran

Universitas Sumatera Utara

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Functions of the Cardio-Vascular System

Delivery of O2, Glucose and other nutrients

to active tissues.

Transport of metabolites and other

substances to and from storage sites.

Transport of hormones, antibodies and other

substances to site of action.

Dr Peter K. McFawn Department of Physiology Queens University Botterell Hall 4thfloor

pkm@post.queensu.ca http://meds.queensu.ca/physiol/underg.html

mailto:pkm@post.queensu.camailto:pkm@post.queensu.ca

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The Circulatory System

2 main divisions

Pulmonary circulation (heart lungs)

Pulmonary artery: deoxygenated blood from the heart tothe lungs

Pulmonary vein: oxygenated blood from the lungs to the

heart

Systemic circulation: (Heart rest of the body) Aorta: feeds oxygenated (arterial)blood to the body

Venae cavae: returns deoxygenated (venou s)blood

from the body

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Histology of cardiac muscle

Two classes of cardiac muscle cells

1) Specialized muscle cells of conducting

system

2) Contractile cells

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Conducting System of the Heart

AV Node

Posterior Inferior Fascicle

Anterior Superior Fascicle

Septal Depolarization Fibers

Purkinjie Fibers

Inter- nodal Tracts

Bundle of HIS

Left Bundle

Branch

Right Bundle

Branch

SA Node

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Autorhytmic cells begin depolarizing due to a slow continuous

influx of sodium and reduced efflux of potassium

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When threshold is reached, the fast calcium channel

open, and calcium rushes in

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Reversal of membrane potential triggers opening of potassiumchannels, resulting in rapid efflux of potassium

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Diagram of the membrane potential of

pacemaker tissue.

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ELECTRICAL

PROPERTIESThe resting membrane

potential -90 mV

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Depolarization lasts about 2 ms, but plateau phase

and repolarization last 200 ms or more.

Repolarization is therefore not complete until the

contraction is half over.

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Excitation (Depolarization of plasma membrane)

Opening of voltage-sensitive plasma membrane Ca2+ channels in T tubules

Flow of Ca2+into cytosol

Ca2+binds to Ca2+receptor on the

external surface of the sarcoplasmic

reticulum

Opening Ca2+channels intrinsic

to these receptors

Flow of Ca2+

into cytosol

Cytosol Ca2+concentration

Contraction

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Relation of Tension to Length in Cardiac

Muscle

Star l ing's law of the heartor Frank-Star l ing law = "energy of contraction is

proportional to the initial length of cardiacmuscle fiber."

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Kesanggupan intrinsik jantung untuk penyesuaian

diri terhadap beban yang berbeda

Dalam batas fisiologisjantung akan

memompakan semua darah yang masuk kedalam

jantung tanpa menimbulkan penumpukan darah

berlebihan. Ini disebabkan oleh peregangan yang

ditimbulkan volume darah yang masuk menyebabkan kekuatan kontraksi bertambah.

Frank StarlingS LAW

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Kurva Frank Starling

Stro

kevo

lume

End Diastoli c Volume

STRETCHING OF MYOCARD

Total blood

volume

Body

position

Intrathoracic

pressure

Atrial

contribution to

ventr.filling

Pumping action of

skletal muscleVenous tone

Intrapericardial

pressure

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= Length of muscle fiber = preload

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Kurva Frank Starling

Stro

kevo

lume

End Diastoli c Volume

Normal

Stimulasi

Adrenergik

Fungsi jantung

Syok

Kardiogenik

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Myocardial Contractility

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Let it beat