chap 19- cardiovascular system

Three main types of blood vessels

Arteries, capillaries, and veins

Arteries

Transport blood away from the heart; most arteries carry oxygenated blood, except for the pulmonary arteries

Veins

Transport blood toward the heart; most veins carry deoxygenated blood except for the pulmonary veins

Capillaries

Sites of exchange between blood and air in lungs and between blood and body cells

Atriums

Left and right superior chambers; receive blood and push blood into the ventricles

Ventricles

Left and right inferior chambers; receive blood from the atria and pump blood out of the heart

Pulmonary circulation

Deoxygenated blood is pumped from right side of heart to the lungs

At lungs, blood picks up oxygen and releases carbon dioxide

Oxygenated blood returns to the left side of the heart

Systemic circulation

Oxygenated blood is pumped from the left side of the heart to the body

At systemic cells, blood exchanges gases, nutrients, and waste

Deoxygenated blood returns to the right side of the heart

Mediastinum

A central region of thoracic cavity that contains the heart (and esophagus and trachea)

Base (of heart)

The superior, widest portion

Apex (of heart)

Inferior tip

Pericardium

Fibrous pericardium: outermost covering, protects heart and maintains its position

Parietal pericardium (serous membrane)

Visceral pericardium: (serous membrane) parietal and visceral pericardium separated by the pericardial cavity which contains serous fluid

Auricles

Cover each atrium, expand to fill with blood

Coronary sulcus

Fat filled groove between the atria and ventricles that house the coronary arteries

Interventricular sulcus

Anterior and posterior fat filled grooves that mark the boundary between the right and left ventricles

Three layers of the heart

(Superficial to deep)

Epicardium

Myocardium

Endocardium

Epicardium

Serous membrane, same as the visceral pericardium

Myocardium

Muscle layer, cardiac muscle

Ventricular muscle differences: left and right pump same volume of blood, LEFT must generate more pressure

Endocardium

Inside lining of simple squamous epithelium

Heart septa (wall)

Interatrial septum

Interventricular septum

Right atrium and right ventricle

Receives deoxygenated blood from systemic circulation

Tricuspid valve is located between RA and RV

Right ventricle receives blood from right atrium and pumps blood to pulmonary trunk

Left atrium and left ventricle

Receives oxygenated blood from pulmonary circulation

Left ventricle: thick myocardium

Receives blood from left atrium and pumps blood to systemic circulation

Right AV valve (tricuspid)

Between right atrium and right ventricle

3

Left AV valve (bicuspid)

Between left atrium and left ventricle

2

Pulmonary semilunar valve

Between right ventricle and pulmonary trunk

Aortic semilunar valve

Between left ventricle and aorta

What kind of flow do valves allow?

Valves allow only an UNIdirectional flow of blood through the heart

Blood flow through the heart (pulmonary circulation)

Superior and inferior vena cava → right atrium → tricuspid valve → right ventricle → pulmonary semilunar valve → lung tissues (pick up oxygen)

Blood flow through the heart (systemic circulation)

Pulmonary veins (left and right) → left atrium → bicuspid valve → left ventricle → aortic semilunar valve → aorta → body tissues

Trabeculae carnage

Muscular ridges inside ventricle wall

Papillary muscles

Cone-shaped projections extending form ventricle wall

Chordae tendineae

Heart strings

Thin strands of collagen fibers attaching papillary muscles to AV valves

Foramen ovale

Foramen (hole) that allows blood flow from right atrium to left atrium in a fetal heart

Fossa ovalis

Remnant if the opening, appears as a shallow depression in the interatrial septum of an adult heart

Ductus arteriosus

Vessel that connects the pulmonary trunk to the aorta in the fetal heart

Ligamentum arteriosus

Remnant of ductus arteriosus, appears as a white ligamentous structure in the adult heart

Autorhythmicity

Myocardial cells can initiate electrical potentials (different from skeletal and smooth muscles)

Two types of myocardial cells

Contractile cells and conducting cells

Intercalated discs

Gap junctions between cardiac muscle cells that join adjacent muscle cells. They synchronize contractions so that so that muscle cells contract together

Cardiac muscle structure

• similar to skeletal muscle, has stations and sarcoplasmic reticulum

• Sarcoplasmic reticulum stores less calcium than skeletal muscle cells

• The source of calcium is outside the cell, which causes a longer refractory period

• Intercalated discs

Conduction system

Consists of autorhythmic cells that conduct action potentials, controlled by ANS

Sinoatrial node (AKA pacemaker)

A clump of myocardial conducting cells in the wall of the upper right atrium

Initiates action potential

Action potentials are conducted to the AV node

Atrioventricular node

A clump of myocardial conducting cells in the wall of the lower right atrium

Action potentials is delayed at the AV node

Delays allows atrial contraction

Atrioventricular bundle

His bundle

Located in the intraventricular septum

Divides into bundle branches

Left and right Bundle branches

Right and left

Continue through septum to apex

Purkinje fibers

Spreads impulse to myocardial contractile cells in the outer walls of the ventricles

Spreads of action potential

• After starting at SA node, the action potential spreads through the aorta

• Action potential reaches AV node

• Action potential is delayed at the AV node while the atria contract

• Action potential travels through AV bundle and bundle branches to purkinje fibers

• Action potential spreads through ventricles; then ventricles contract

P wave

Depolarization of atria

Action potential travels from SA node to AV node

QRS complex

Depolarizing of ventricles

Action potential travels AV node → AV bundle → bundle branch → purkinje fibers

Repolarization of atria occurs st the same time, but is hidden on ECG

T wave

Repolarization of ventricles

Relaxation

Cardiac cycle

All events that occur from the beginning of one heart rhythm to the beginning of the next heart rhythm

Valves ensure that flow is forward (closure prevent backflow)

Phases of cardiac cycle

Atrial systole, atrial diastole, ventricular systole, ventricular diastole

Systole

When a chamber of the heart contracts

Diastole

When a chamber of the heart relaxes

Atrial systole

Represented by the P wave

Pressure in atria rises

Blood is pumped into ventricles when the atria contract

AV valves are open, semilunar valves are closed

Atrial diastole

Relaxation of atria

Remain relaxed for the rest of the cycle

Ventricular systole

Represented by QRS complex

Two phases : isovolumetric contraction and ventricular ejection phase

Isovolumetric contraction

Ventricles begin to contract, pressure rises

No blood ejected

All 4 valves are closed

Ventricular ejection phase

Pressure in ventricles forces the semilunar valves to open

Blood is ejected from the heart

Ventricular diastole

Represented by the T wave

Two phases: isovolumetric relaxation and late ventricular diastole

Isovolumetric relaxation

Ventricular muscles relax

Pressure drops

Semilunar valves close, so all 4 valves are closed

Late ventricular diastole

Pressure continues to drop

Blood flows from atria to ventricles

AV valves open

All four chambers are relaxed (cardiac diastole)

Heart sounds: Two sounds (S1 and S2)

S1: closing of AV valves; “lub”

S2: closing of semilunar valves; “dub”

Heart sounds: murmur

Represents turbulent blood flow (backflow of blood)

Stroke volume

Volume of blood ejected in one beat

End-diastolic volume (EDV)

Amount of blood in ventricle at the end of diastole when its completely full

Appx 120-130 mL

End-systolic volume

Amount of blood remaining in ventricle after contraction finishes when it is almost empty

Appx 50-60 mL

SV= EDV-ESV

70mL=130mL-60mL

Cardiac output

Volume of blood ejected in one minute

Cardioacceleratory center

Sends sympathetic nerve signals (fight or flight)

Ventricles are richly innervated by sympathetic nerves

Sympathetic stimulation causes release of norepinephrine

Increase in heart rate and force of contraction

Cardioinhibitory center

Sends parasympathetic nerve signals (rest and digest)

Parasympathetic signals sent via Vagus nerve to SA and AV nodes

Acetylcholine (Ach) is released and slows HR

Decrease in heart rate. No change in force of contraction

Increased contractility

Caused by: sympathetic stimulation (epinephrine and norepinephrine)

More blood is ejected from the heart

Decreased ESV causes increased stroke volume

Decreased contractility

Caused by: Parasympathetic stimulation (acetylcholine)

Less blood is ejected from the heart

Increased ESV causes decreased stroke volume

Afterload

Resistance in arteries to ejection of blood

Anything that resists blood being ejected from the heart increases afterload, such as atherosclerosis

Increased afterload decreases stroke volume

Decreased afterload increases stroke volume

Atherosclerosis

Build of plaque in artery walls

Can be caused by scar tissue, fatty deposits

Increases afterload

Myocardial infarction

Heart attack

Due to lack of blood flow and oxygen

Results in death of cardiac muscle cells

Cardiac arrhythmia

Deviation from normal pattern of contraction

Atrial fibrillation

Heart beats in an uncontrolled manner

Ventricles still pump blood, atria beats erratically

Ventricular fibrillation

Quickly leads to brain death

Bradycardia

Resting heart rate below 60 bpm

Tachycardia

Resting heart rate above 100 bpm