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
