External manifestations of cardiac activity. Regulation

of heart work

Lecturer MD, Ph.D. Angelika V. Ivasenko

ATRIAL SYSTOLE 0,1sec

Ventricle systole 0,33sec

VENTRICLE SYSTOLE 0,33sec

VENTRICLE SYSTOLE 0,33sec

COMMON PAUSE 0,37sec

COMMON PAUSE 0,37sec

COMMON PAUSE 0,37sec

External manifestations of cardiac activity

• Mechanical (apex beat, pulse)

• Sound (heart tones)

• Electrical (ECG)

Sphygmogram

1.Anacrote2. Catacrote3. Incisure4. Dicrotic rise

FREQUENCY

MAGNITUDE

VELOCITY

rarus

altus

frequens

tardus

сеler

parvus

PULSUS CHARACTERISTICS

SYSTOLIC TONE

components:1. VALVULAR (A-V valves closure)2. MUSCULAR asynchronous contraction3. VASCULAR (aorta vibration )4. TENDON (chordae tendineae tension)

SYSTOLIC TONE. PLACES OF BEST HEARING

• heart apex projection (IV-V intercostal space on the left, 1,5-2 cm medial from the medioclavicular line)•the place of junction of sternum body and xyfoid processus

DIASTOLIC TONE

components:1. VALVULAR (semi-lunar

valves closure)

2. VASCULAR (blood rebound )

DIASTOLIC TONE. PLACES OF BEST HEARING

• II right intercostal space along the parasternal line (over aorta).

• II left intercostal space along the parasternal line (over pulmonary artery).

Right atrium excitation- ascending part of P-wave

Spreading of excitation from SA to AV node – interval PQ

Excitation of left part of intraventricular septum – Q wave

Excitation of ventricles’ apexes – R wave

Spreading of excitation from endocardium to epicardium

- QRS complex

Depoloarization in ventricles completed – ST segment

Quick final repolarization of the ventricles – T wave

MECHANISMS OF HEART REGULATION

•INTRACARDIAC REGULATION

•EXTRACARDIAC REGULATION

INTRACARDIAC REGULATION

1.Myogenic a)Geterometric (Franc-

Starling law) b)Gomeometric (Boudichi

“staircase”)2.Peripherial heart reflexes

Franc-Starling law• The more heart chambers are filled with

blood during diastole, the greater force of contraction they develop during systole

• This prevents ventricles from dilation allowing them to eject all the blood

Boudichi “staircase”• At high frequency of stimulation force of

contraction increases regardless of the cardiomyocytes length

Peripheral heart reflexes• Are performed by methasympathetic

system in the heart• They restrict Frank-Starling law so that to

readjust cardiac output to the systemic BP• The most prominent reflex is from right

atrium to left ventricle

Peripheral heart reflexes• In case of high systemic BP high threshold

receptors are activated in right atrium and via cholinergic fibers decrease heart rate & stroke volume in the left ventricle

• In case of low systemic BP low threshold receptors are activated in right atrium and via adrenergic fibers increase heart rate & stroke volume in the left ventricle

EXTRACARDIAC REGULATION

•Nervous regulation (SNS, vagus)

•Humoral regulation (Ad, Thyroxin)

HEART INNERVATION

Mechanism of sympathetic stimulation

• Adrenalin opens Na+ channels• Na+ influx depolarises myocardiocyte’s

membrane• Threshold decreases (“+” batmotrophic effect)• Time of SDD decreases (“+” chronotrophic

effect)• Conductivity increases (“+” dromotrophic effect)• Contractility increases (“+” inotrophic effect)

Influence of sympathetic nerve stimulation on AP of the pacemaker ( A – before, B – after stimulation)

ΔV1, Δ V2 – thresholds of depolarization, α1, α2 – angler, showing the steepness of depolarization, t1, t2 – time of slow diastolic

depolarization

Influence of vagus stimulation on AP of the pacemaker ( A – before, B – after stimulation)ΔV1, Δ V2 – thresholds of depolarization, α1, α2 – angler, showing the steepness of depolarization, t1, t2 – time of slow diastolic depolarization

Mechanism of parasympathetic stimulation

• Acetylcholine opens K+ channels• K+ efflux repolarises myocardiocyte’s membrane• Threshold increases (“-” batmotrophic effect)• Time of SDD increases (“-” chronotrophic effect)• Conductivity decreases (“-” dromotrophic effect)• Contractility decreases (“-” inotrophic effect)