Heart

The cardio-vascular

system

The cardio-

vascular system

Heart Vessels

blood lymphatic

Heart location

• The heart is located in the chest between the lungs

behind the sternum and above the diaphragm. It is

surrounded by the pericardium. Its size is about

that of a fist, and its weight is about 250-300 g. Its

center is located about 1.5 cm to the left of the

midsagittal plane. The great vessels: the superior

and inferior vena cava, the pulmonary artery and

vein, as well as the aorta are located above the

heart. The aortic arch lies behind the heart. The

esophagus and the spine lie further behind the

heart.

Heart structure

Heart - hollow 4-chamber organ,

the center of blood system.

THE HUMAN HEART

THE HUMAN HEART

Pericardium (the bag around heart)

Structure of a heart wall

•Protects from a friction.

Epicardium (an external layer)

•Friable connecting fabric.

Myocardium (midium layer)

Cardiac muscle.•3 types cardiomyocytes:

• Typical - contractive;• Atypical - conductive (form the conducting

system).• Secretory – secret sodiumurethic hormone

•Atrium - 2 layers:• 1st layer - external circular;• 2nd layer - internal longitudinal.

•Ventricles - 3 layers:• 1st layer - external a oblique;• 2nd layer - average circular;• 3rd layer - internal longitudinal• (papillary muscles).

Endocardium (inside layer)

•Connecting fiber + elastic fibers.•Endotelium.•Forms heart valves.

Structure of a heart wall

Structure of a myocardium

Cardiac muscle.•3 types cardiomyocytes:

• Typical – contractive;• Atypical - conductive (form the conducting

system).• Secretory – secret sodiumurethic hormone

•Atrium - 2 layers:• 1st layer - external circular;• 2nd layer - internal longitudinal.

•Ventricles - 3 layers:• 1st layer - external a oblique;• 2nd layer - average circular;• 3rd layer - internal longitudinal• (papillary muscles).

• The cardiac muscle fibers are oriented spirally and

are divided into four groups: Two groups of fibers

wind around the outside of both ventricles. Beneath

these fibers a third group winds around both

ventricles. Beneath these fibers a fourth group

winds only around the left ventricle. The fact that

cardiac muscle cells are oriented more tangentially

than radially, and that the resistivity of the muscle

is lower in the direction of the fiber has importance

in electrocardiography and magnetocardiography.

Heart valves

Heart valves

• Each chamber has a sort of one-way valve at its exit

that prevents blood from flowing backwards. When

each chamber contracts, the valve at its exit opens.

When it is finished contracting, the valve closes so

that blood does not flow backwards.

• The tricuspid valve is at the exit of the right

atrium.

• The pulmonary valve is at the exit of the right

ventricle.

• The mitral valve is at the exit of the left atrium.

• The aortic valve is at the exit of the left ventricle.

1. Cardiac output-is the volume of blood

pumped per minute by each ventricle.

2. Cardiac rate-the average resting rate in an

adult is 70 beats per minute.

3. Average stroke volume-volume of blood

pumped per beat by each ventricle.

Function of heart

The delivery

Provides blood movement

on vascular system.

Endocrine

Atriums` myocytes secret

sodiumurethic hormone

which regulates:

•Excretion Na + and Cl- by kidneys;

•Arterial pressure;

•Renin secretion.

Cardiac conducting system

Accumulation atypical fibers and

terminals of sympathetic and

parasympathetic nerves.

Function of Cardiac

conduction system

1. Place of origin of impulses

(Action potentials) in heart.

2. Coordinative and consecutive contractions

of atria and ventricles.

3. Synchronous involving in process of

contraction of all myocardium cells of

ventricles for systole productivity improvement.

4. Determines frequency of heartbeats.

The physiological

properties of a myocardium

1. Excitability.

2. Conductivity.

3. Contractability.

4. Automation.

5. Refractorability.

1. Excitability – the ability to answer by

excitation to stimulation.

2. Conductivity – the ability to conduct

excitation.

3. Contractability - capability

cardiomyocytes to contract and a relax.

The physiological

properties of a myocardium

4. Automation – the ability of a myocardium

to be initiated, and then to be reduced under

the influence of the impulses arising in

conducting system.

The gradient of

automation – degree

of automation that

above, than is more

close located to

Sinus node.

The physiological

properties of a myocardium

Absolute Refractorability (0,27 s) –

total absence of excitability.

Relative Refractorability (0,03 s) - ability

of a cardiac muscle to answer with

excitation on very higher supraliminal

irritation.

Extrasystole - extraordinary contraction

of heart.

5. Refractorability - process at which

the cardiac muscle loses ability to

answer with new excitation additional

irritation.

The physiological

properties of a myocardium

MUSCLE

CONTRACTION

• Depolarization of cardiac muscle cells differs from that

of other muscle cells.

• Repolarization takes much longer to occur and thus cells

cannot be stimulated at high frequency. The advantage is

that cardiac muscle are prevented from going into

tetanus.

REFRACTORY

PERIOD OF

CARDIAC MUSCLES

Very long compared to skeletal

muscles (300 vs10 ms)

Cardiac muscle AP is different

• AP has a plateau due to Ca2+

influx

• AP has 3 phases

Importance:

• Prevents tetanization (cannot

stimulate at close intervals)

• Maintains pumping efficiency

(heart has time to fill and pump)

Tachycardia and

Bradycardia

Tachycardia is a fast heart rate and

Bradycardia is slow heart rate.

For example: A cardiac rate slower

than 60 beats per minute indicates

Bradycardia. A rate faster than 100

beats per minute is described as

Tachycardia.

Both of these can occur normally.

Endurance trained athletes often

have heart rates ranging from 40 to

60 beats per min. This is a beneficial

adaptation.

The cardiac cycle

Systole – contractions of ventricles

and atriums.

Diastole – relaxations (dilatation) of

atriums and ventricles.

Cardiac cycle - rhythmically

repeating contractions and

relaxations of atriums and

ventricles.

Phases of the cardiac cycle

•Pressure in auricles raises to 5-8 mm hg•Ventricles are relaxed.•The blood from atriums arrives in ventricles.

Systole of atriums 0,1 s

The tension period

Systole of ventricles 0,33 s

The expulsion (ejection) period

Phaseasynchronous

tensions0,05 s

Phaseisometrictensions0,03 s

Phasefast

expulsion0,12 s

Phaseslow

expulsion0,13 s

•Excitation diffusion on a myocardium.•Atrioventricular valves are opened.

•The length myocytesdoesn't change.•Pressure grows.•All valves are closed.

•Cardiomyocytes are shortened.•Pressure grows.

•Atrioventri-cular valvesare closed.

•Semilunar valves are opened.

The blood arrives in an artery.

The period of a relaxation 0,12 s

Diastole (the general pause) of ventricles 0,47 s

The loaded period 0,25 s

The postdiastolic period0,04 s

The period of an isometric relaxation

0,08 s

Phase offast are loaded

0,1 s

Phase ofslow are loaded

0,15 s

•The beginningof closing of semilunar valves.

•All valves areclosed.

•Opening of atrioventricular and semilunar valves.

Ventricles are filled with a blood. The new cardiac cycle begins.

THE CARDIAC

CYCLE

External manifestations

of heart work

The mechanicalCardiac stroke - blow of an apex of heart about a thorax

wall at form and volume change in a systole phase.

Sounds

Heart tones

I tone - systolic, long, low, deaf (closing of cuspsof atrioventricular valves).

II tone - diastolic, short, high, sonorous (closing ofsemilunar valves in the diastole beginning).

III tone - vibration of walls of ventricles during

filling their with blood.

IV tone - at a systole of auricles and homing of apart of a blood in auricles at a systole of ventricles.

Electric

Record electrocardiogram (ECG) - registration

of biological potentials of a cardiac muscle.

Heart tones

1

2

1 - areas of listening of I tone;

2 - areas of listening of II tone.

"LUB-DUB"

• The first heart tone, or S1, "Lub" is caused by

the closure of the atrioventricular valves, mitral

and tricuspid, at the beginning of ventricular

contraction, or systole. When the pressure in the

ventricles rises above the pressure in the atria,

these valves close to prevent regurgitation of

blood from the ventricles into the atria.

• The second heart tone, or S2 (A2 and P2),

"Dub" is caused by the closure of the aortic

valve and pulmonic valve at the end of

ventricular systole. As the left ventricle empties,

its pressure falls below the pressure in the aorta,

and the aortic valve closes. Similarly, as the

pressure in the right ventricle falls below the

pressure in the pulmonary artery, the pulmonic

valve closes.

Triangle of Einthoven

in three standard leads (I, II, III)

Electrocardiogram (ECG)

Standard leads (I, II, III)

Chest Leads

Electrocardiogram (ECG)

Electrocardiogram (ECG)

Waves P - excitation of auricles.Waves Q - a depolarization of an septum.Waves R - excitation diffusion on the bases of ventricles.Waves S - full coverage by excitation of ventricles.Waves Т - repolarization of a myocardium.Complex QRST - excitation occurrence in a myocardium of

ventricles.Interval P-Q - characterizes rate of diffusion

exaltations from sinus node to ventricles.Interval Т-Р - absence of difference of a potential in heart

(The general pause).Interval Q-T - corresponds to duration of all

the periods of excitation of ventricles (the electricheart systole).

Electrocardiogram (ECG)

Control of heart work

•The intracellular.

•Intercellular contacts.

•Intracellular peripheral reflexes.

Provides maintenance

adequate to loads with a blood.

The endocardiac

(intracardiac or intrinsic)

•The nervous.

•The humoral.

•The reflex.

The exocardiac

(extracardiac or extrinsic)

Endocardiac control of heart

work

Intracellular control

Control of intercellular interactions

Synthesis augmentation contractive proteins.The law of heart of Frank-Starling –the more cardiomyocytes are stretched duringa diastole, the stronger they are contractedduring a systole.

Intercalary disks (nexus) - the places of contacts providing fast carrying out of exaltation and atrophicity in cardiomyocytes.

Endocardiac peripheric reflexes

Intracellular reflex arches:

1. Stretching receptors.

2. Afferent passway

3 Intramural ganglions.

4. Efferent passway .

5. Cardiomyocyte.

Value:

Compound activity of different parts of heart.

Support at necessary level blood supply of arterial system.

1 - nucleuss of cardiomyocytes;

2 - intercalary disks - borders of cardiomyocytes

Control of intercellular

interactions

Nervous control of heart

work

Increase of frequency of the heartbeat (Positive chronotropic effect)

Sympathetic influences

(Spinal cord segments)

Increase of amplitude of the heartbeat (Positive inotropic effect)

Improvement of carrying out of excitation ona myocardium (Positive dromotropic effect)

Increase excitability(Positive bathmotropic effect)

Decrease of frequency of the heartbeat (Negative chronotropic effect)

Parasympathetic influences

(An oblong brain, a vagus nerve)

Decrease of amplitude of the heartbeat (Negative inotropic effect)

Retardations of carrying out of excitation ona myocardium (Negative dromotropic effect)

Decrease excitability(Negative bathmotropic effect)

Humoral control of heart

work

Noradrenaline

Adrenaline

Angiotensin

Serotonin

Glucagon

Hormones

Increase of force

of reductions of

a myocardium

К+

Electrolytes

Oppression of

cardiac activity

Са2+ Stimulation

cardiac activity

Thyroxine Increase

heartbeat

Reflex control of heart work

Cortex

Cortex-subcortical influence

Limbic system

Hypothalamus – the integrative center

Baroreceptors of an aortic arch,

Areas of a bifurcation of a carotid

Reflexogenic zones

Painful receptors

Reflex of the Golz

Eye-cardiac Aschner's reflex

Regulation of Heart

Beat