Anatomy and Physiology II Chapter 2: Cardiovascular System: Heart

heart sounds

"lub": closing of the atrioventricular valves "dub": closing of the semilunar valves

Cardiac cycle

(i) Isovolumetric relaxation: all heart valves are closed (ii) Isovolumetric contraction:

heart valves

-4 vales -composed of elastin and collagen-contains strong connective tissue -close to prevent back flow of blood

mitral valve

-AV valve -between left atrium and ventricle -prevents back flow into left atrium -also called bicuspid valve

tricuspid valve

-AV valve -between right atrium and ventricle -prevents back flow to right atrium

electrocardiogram

-As the heart muscle is stimulated and contracts, the electrical activity can be detected and recorded by an electrocardiograph. -A typical wave consists of three sections: the P wave, the QRS complex, and the T wave.

conducting system of heart

-Sinoatrial node (SA node), made up autorhythmic cells, functions as the primary pacemaker and is responsible for the sinus rhythm (70 beats per minute -atrioventricular node (AV node), made up of authrhythmic cells, reserve pacemaker responsible for the nodal rhythm (40-60 beats per minute) -internodal pathways or tracts made up of cells which transmit the electrical stimulus (action potential) initiated by the SA node -bundle of His which originates from the AV node, divides into right and left bundle branches -purkinje fibers, made up of auto rhythmic cells (capable beating 20-40 times per minute), are extensions of the bundle branches in the myocardium and in contact with the cardiomyocytes, which contract in response to the electrical stimulus (action potential) traveling via the conduction system

pulmonary curcuit

right side of the heart receives deoxygenated blood and pumps it to the lungs for oxygenation -1/5 time

cardiac arrest

stoppage of all heart functions

the t wave in the EKG represents

ventricular repolarization

pacemaker

an electrical device implanted in the chest with electrodes to the heart; primary used to treat bradycardia

defibrillation

applying electrical shock to the external chest in order to restore normal heart rhythm; also called cardioversion

cardiac muscle cells

-about 1% are excitable and auto rhythmic but not contractile and are specialized to set the pace at which the heart beats -99% cardiomyocytes are excitable, auto rhythmic and contractile cells, which are capable of generating force

epicardium

-also called the visceral pericardium -thin serous membrane -attached to the surface of heart and part of the heart wall

heart wall and cardiac muscles

-cardiac muscles are aerobic, non-fatiguable cells, and must be supplied with oxygen and nutrients to be able to produce ATP for muscle contraction to generate force to pump the blood out the heart

coronary circulation

-circulation of blood through the coronary blood vessels to deliver oxygen and nutrients to the heart muscle tissue -1/20th of the cardiac out or about 250ml/min -coronary arteries originate from the base of aorta

great vessels

-enter or exit from the base of heart -inclue inferior vena cava, superior vena cava, pulmonary trunk (pulmonary arteries), pulmonary veins, aorta -5

factors affecting heart rate

-increases in response to sympathetic stimuli

endocardium

-inner lining -very thin and delicate -simple squamous epithelium

heart location in the body

-mediastinum of the thoracic cavity between the two lungs superior to the diaphragm -lying between 2nd rib to the 5th intercostal space

myocardium

-middle layer -cardiac muscle tissue -contracts to pump blood

generation of action potential in pacemaker cells and cardiomyocytes

-pacemaker cells are excitable cells, capable of generating an action potential in an auto rhythmic manner

left ventricle

-pushes blood a greater distance and higher pressure -thickest, most muscular wall

right ventricle

-relatively thin walled and partly wraps around left ventricle

atria

-right and left atrium -upper chambers -smaller superior chambers -thin muscular wall -function is to collect blood returning to the heart and then contract to deliver it to the ventricles

ventricles

-right and left ventricle -lower chambers of the heart -larger inferior chambers -larger chambers and thick muscular walls -primary pumping chambers -pump same volume of blood 70ml/beat but different blood pressure

aortic valve

-semilunar valve -between left ventricle and aorta -prevents back flow into left ventricle

pulmonary valve

-semilunar valve -between right ventricle and pulmonary trunk -prevents back flow into right ventricle

cardiac output (CO)

-the volume of blood pumped out of the left ventricle per minute -determined by multiplying stroke volume (SV), the volume of blood leaving the left ventricle with each beat, times the heart rate (HR) -CO = SV x HR

humans have

Double circulatory system

arrhythmia

a change in the normal heart rhythm: ex include fibrillation, bradycardia, and tachycardia; also called dysrhythmia

double circulation

a circulatory system consisting of separate pulmonary and systemic circuits, in which blood passes through the heart after completing each circuit - entire blood (5 liters) passes through the lungs 5 times every minute

coronary artery disease (CAD)

a hardening and narrowing (atherosclerosis) of the coronary arteries supplying blood to the heart muscle; may result in angina pectoris, myocardial infarction, or sudden death

cardiac muscle cells in vertebrates

are excitable and auto rhythmic cells, generate an action potential without any external stimulus

deposition of fat in the coronary arteries causes

atherosclerosis

the heart pacemaker cells are

autorhythmic cells

diastole

blood is able to flow into the chamber because it is relaxed

the pulmonary trunk

carries deoxygenated blood from the right ventricle to the pulmonary arteries

systole

chamber contracts, developing the force to squeeze and eject blood from the chambers

murmur

change from the normal heart sounds; often indicates a problem with a hart valve

valvular prolapse

cusps of a heart valve are too loose; results in inability of the valve to close tightly

valvular ste

cusps of heart valves become too stiff; results in inability of the heart valve to either open or close fully

cardiac muscle cells in invertebrates

depend on nervous stimulus to beat and will stop beating if the nerve supply to the heart is cut

stroke volume

difference of the end diastolic volume (EDV) and end systolic volume (ESV)

pericardium

double-layered, protective sac surrounding the heart

angina pectoris

episodes of severe pain in the chest caused by insufficient oxygen supplied to the heart muscle

congenital defects

heart defects from birth

congestive heart failure (CHF)

inability of the heart to effectively pump blood through the circulatory system; symptoms include shortness of breath and swelling in the feet and ankles

endocarditis

inflammation of the inner lining of the heart chambers; often caused by a bacterial infection

pericarditis

inflammation of the pericardium

systemic circuit

left side of heart receives oxygenated blood from the lungs and pumps it to the head and body -about 1min

thrombolytic

medication that dissolves an existing blood clot; used to treat myocardial infarction

cardiac cycle

one complete round of diastole and systole (also one heartbeat)

external anatomy

oxygenated blood passes through the left side of the heart and deoxygenated blood through the right

electrocardiography

process of recording the electrical activity of the heart; produces an electrocardiogram (record of the hearts electrical activity)

coronary arteries originate from

the base of aorta

myocardial infarction

the occlusion of one or more coronary arteries caused by plaque buildup (heart attack)

fibrous pericardium is made up of

tough fibrous connective tissue

heart block

type of arrhythmia from disruption of the movement of stimulus wave through the conduction system; may be caused by scar tissue or heart tissue damage

tachycardia

type of arrhythmia with abnormally fast heart rate; usually applies to rates greater than 100 beats per minute

bradycardia

type of arrhythmia with abnormally slow heart rate; usually below 60 beats per minute

Premature Atrial Contraction (PAC)

type of arrhythmia with contraction of the atria too early in the cardiac cycle

premature ventricular contraction (PVC)

type of arrhythmia with contraction of ventricles too early in the cardiac cycle

fibrillation

type of arrhythmia with rapid, random, quivering of the heart muscle; fails to produce the coordinated contraction necessary to put blood; may be life threatening

flutter

type of arrhythmia with very rapid (up to 300 beats/minute) but coordinated heart contractions

patent ductus arteriosus (PDA)

type of congenital defect with failure of a fetal blood vessel between pulmonary artery and aorta to close at birth

atrial septal defect

type of congenital defect with failure of the foreman oval to close over at birth, leaving a hole in the intertribal septum