Chapter 20 - Cardiovascular System: The Heart
Terms
undefined, object
copy deck
- Pulmonary circulation
- circuit that carries blood through the right side of the heart and out to the lungs, returning blood to the left side of the heart
- Systemic circulation
- circuit that carries blood through the left side of the heart and out to the entire body, returning blood to the right side of the heart
- Cardiology
- a medical specialty concerned with the diagnosis and treatment of heart disease
- Name the four functions of the heart.
-
1) generating blood pressure
2) routing blood
3) ensuring one-way blood flow
4) regulating blood supply - Apex of the heart
-
blunt, rounded point of the heart;
located at the posterior and left margin of the heart - Base of the heart
- anterior portion of the heart, opposite the apex
- Mediastinum
- a midline partition formed in the thoracic cavity by the heart, trachea, esophagus, and associated structures
- Electrocardiogram (ECG, EKG)
-
a graphical recording of the electrical stimulation of the atria and ventricles;
the summated record of the cardiac action potentials - Pericardium (pericardial sac)
- a double-layered closed sac that surrounds the heart
- Fibrous pericardium
- a tough, fibrous connective tissue outer layer of the pericardial sac
- Serous pericardium
- a thin, transparent layer of simple squamous epithelium that forms the inner layer of the pericardial sac
- Parietal pericardium
- the part of the serous pericardium lining the fibrous pericardium
- Visceral pericardium (epicardium)
- the part of the serous pericardium that covers the heart surface
- Pericardial cavity
-
located between the visceral and parietal pericardia;
filled with a thin layer of serous pericardial fluid;
helps reduce friction as the heart moves within the pericardial sac - Epicardium
-
a thin serous membrane that constitutes the smooth outer surface of the heart;
synonymous with the visceral pericardium - Myocardium
-
thick, middle layer of the heart, composed of caridac muscle cells;
responsible for the ability of the heart to contract - Endocardium
-
the smooth inner surface of the heart chambers;
consists of simple squamous epithelium over a layer of connective tissue;
smooth surface allows blood to move easily through the heart; heart valves result from these - Musculi pectinati
- muscular ridges found on the the interior of both auricles and a part of the right atrial wall
- Crista terminalis
- a ridge on the right atrial wall that separates the musculi pectinati from the larger, smooth portions of the atrium
- Trabeculae carneae
- large muscular ridges and columns found on the interior walls of the ventricles
- Atria
- the two superior and posterior chambers of the heart
- Ventricles
- thick walled chambers that form the anterior and inferior part of the heart
- Coronary sulcus
- a large sulcus that runs obliquely around the heart, separating the atria from the ventricles
- Anterior interventricular sulcus
- a sulcus located on the anterior surface of the heart that separates the left and the right ventricles
- Posterior interventricular sulcus
- a sulcus located on the posterior surface of the heart that separates the left and the right ventricles
- Right atrium
- has three major openings, the superior and inferior vena cava recieve blood from the body and the coronary sinus recieves blood from the heart
- Left atrium
- has four openings that recieve blood from the lungs
- Interatrial septum
- portion of tissue that separates the two atria
- Fossa ovalis
- a slight oval depression found in the interatrial septum, marks the former location of the foramen ovale
- Foramen ovale
-
an opening between the right and left atria in the embryo and fetus;
allows blood to flow from the right to the left atrium in the fetus to bypass the pulmonary circulation - Atrioventricular canals
- canals that lead from each atrium to its adjacent ventricle
- Right ventricle
- pumps blood into the pulmonary trunk
- Left ventricle
- pumps blood into the aorta
- Interventricular septum
- a portion of tissue that separates the two ventricles
- Atrialventricular valve
- a valve located in each atrioventricular canal that is composed of flaps; allow blood to flow from the atria into the ventricles, but not form ventricles to atria
- Tricuspid valve
-
the AV valve located between the right atrium and the right ventricle;
consists of 3 flaps (tri-cusp) - Bicuspid valve
-
the AV valve located between the left atrium and the left ventricle;
consists of two flaps (bi-cusp);
also known as the mitral valve - Papillary muscles
-
cone shaped muscular pillars contained in each ventricle;
contract when the ventricles contract and prevent the valves from opening into the atria by pulling on the chordae tendineae attached to the valve cusps - Chordae tendineae
- thin, strong connective tissue strings that attach the papillary muscles to the cusps of the AV valves
- Aortic semilunar valve
-
a valve located betwen the left ventricle and the aorta;
prevents the backflow of blood from the aorta into the left ventricle - Pulmonary semilunar valve
-
a valve located between the right ventricle and the pulmonary trnk;
prevents the backflow of blood from the pulmonary trunk into the right ventricle - Heart skeleton
- consists of a plate of fibrous connective tissue between the atria and ventricles; fibrous plate forms rings around AV and semilunar valves and provides a solid support for them
- Cardiac muscle cells
-
elongated, branching cells that contain one or occasionally two centrally located nuclei;
contains actin and myosin myofilaments that give a striated appearance;
contractions pushes blood through the heart - Intercalated discs
- specialized cell-cell contacts that bind adjacent cardiac muscle cells together, end-to-end; membranes have folds in which adjacent cells fit together
- Desmosomes
- specialized plasma membrane structures in the intercalated discs that hold adjacent cells together
- Gap junctions
-
found in the intercalated discs of cardiac muscle cells; function of areas of low electric resistance between the cells, allowing action potentials to pass from one cell to adjacent cells;
allows cardiac muscle cells to behave as one unit - Sinoatrial (SA) node
-
the pacemaker of the heart;
made up of specialized, small-diameter cardiac muscle cells that merge with other cardiac muscles cells of the right atrium;
action potentials spread from the SA node to adjacent fibers and spread across the atria - Atrioventtricular (AV) node
-
similar to the SA node in composition, lies in the inferior portion of the right atrium;
conduction signals require about 0.04s to travel from the SA to the AV node;
sends conuction signal down AV bundle - Atrioventricular (AV) bundle
-
a conducting bundle of the heart that is begins at the AV node;
passes through a small opening in the fibrous skeleton to reach the interventricular seputm, where it divides to form right and left bundle branches, which extend beneath the endocardium on either side of the interventricular septum to the apices of the right and left ventricles - Purkinje fibers
-
inferior terminal branches of the bundle branches;
large-diameter cardiac muscle fibers with fiwer myofilaments and more intercalated discs than other cardiac muscle;
action fibers travel more rapidly along these fibers - Resting membrane potential
- electric charge gradient inside a plasma membrane, measured relative to just outside the plasma membrane
- Depolarization phase
- a phase of cardiac muscle cell action potential propogation in which voltage-gated Na+ channels open, voltage-gated K+ close, and voltage-gated Ca++ channels begin to open
- Early repolarization phase
- a phase of cardiac muscle cell action potential propogation in which voltage-gated Na+ channels close and some voltage-gated K+ channels open, causing early repolarization
- Plateau phase
- a phase of cardiac muscle cell action potential propogation in which voltage-gated Ca++ channels are open, produceing the plateau by slowing further repolarization
- Final repolarization phase
- a phase of cardiac muscle cell action potential propogation in which voltage-gated Ca++ channels close and many voltage-gated K+ open.
- Calcium-induced calcium release (CICR)
- a process by which the movement of Ca++ through the plasma membrane into cardiac muscle cells stimulates the release of Ca++ from the sarcoplamic retiulum
- Autorhythmic
-
a trait of cardiac muscle fibers;
the heart stimulates itself to contract at regular intervals - Prepotential
-
a spontaneous developing local potential in cells of the SA node;
leads to the spontaneous action potential seen in the cardiac muscle - Ectopic focus
- any part of the heart other than the SA node that generates a heartbeat
- Absolute refractory period
- a period during the action potential in cardiac muscle in which the cardiac muscle is completely insensitive to further stimulation
- Relative refractory period
- a period during the cardiac muscle action potential during which the cells exhibit reduced sensitivity to additional stimulation
- P wave
-
the first peak on an EKG;
the result of action potentials that cause depolarization of the atrial myocardium - QRS complex
-
the second peak on an EKG readout;
composed of three individial waves, results from ventricular depolarization and signlas the onset of ventricular contraction - T wave
- represents repolarization of the ventricles and precedes ventricular relaxation
- Cardiac cycle
- refers to the repetitive pumping process that begins with the onset of cardiac muscle contraction and ends with the beginning of the next contraction
- Systole
-
contraction of heart muscles;
when used without reference to a particlar chamber, ventricular systole is assume - Diastole
-
dilation or relaxation of heart muscles;
when used without reference to a particlar chamber, ventricular diastole is assume - Atrial systole
- contraction of the atrial myocardium
- Atrial diastole
- relaxation of the atrial myocardium
- Ventricular systole
- contraction of the ventricular myocardium
- Ventricular diastole
- relaxation of the ventricular myocardium
- Period of isovolumic contraction
-
a period at the beginning of systole in which contraction of the ventricles causes the closer of the AV valves and the intraventricular pressure has not increased enough to open the semilunar valves;
a period in which the volume of the blood inside the ventricles does not change, even though they are contracting - Period of ejection
- a period of the cardiac cycle in which the ventricular pressure exceeds the pressure in the aorta or pulmonary trunk, causing the semilunar valves to be forced open and blood to flow from the venticles into their respective vessels
- Period of isovolumic relaxation
- period of the cardiac cycle in which, at the very beginning of diastole, in which the pressure in the ventricles begins to decrease, causing the semilunar valves to close, during this time, the pressure in the ventricles is still greater than the pressure in the atria, therefore, the AV valves remain clsoed, there is no cahnge in the volume of blood even though the heart is relaxing
- End-diastolic volume
-
the volume of blood in the ventricles following ventricular diastole;
normally 120-130mL of blood - End-systolic volume
-
the volume of blood in the venticles following ventricular systole;
normally 50-60mL of blood - First heart sound
-
"lubb";
a low pitched sound caused by vibration of the AV valves and surrounding fluid as the valves close at the beginning of ventricular systole - Second heart sound
-
"dup";
a higher-pitched sound that results from the closure of the aortic and pulmonary semilunar valves at the beginning of ventricular diastole - Dicrotic notch (incisura)
-
a graphical representation of the elastic stretch and recoil o f the arota following the period of ejection;
describes aortic pressure - Mean arterial pressure (MAP)
-
slightly less than the average of the systolic and diastolic pressure in the aorta;
proportional to CO x PR - Cardiac output (CO)
-
the amount of blood pumped by the heart per minute;
CO = HR x SV - Peripheral resistance (PR)
- the total resistance against which blood must be pumped
- Heart rate (HR)
- the number of times the heart beats (contracts) per minute
- Stoke volume (SV)
-
the volume of blood pumped during each heartbeat (cardiac cycle);
SV = EDV - ESV;
about 70mL of blood in a normal, resting adult - Venous return
-
the amount of blood returning to the heart from the peripheral circulation;
promotes an increase in EDV during exercise - Cardiac reserve
-
the difference betwen cardiac output when person is at rest and maximum cardiac output;
the greater a persons' cardiac reserve, the greater their capacity for doing exercise - Intrinsic regulation
-
heart regulation that results from the normal functional characteristics of the heart and does not depend o neither neural or hormonal regulation;
involves Starling's law of the heart, venous return, etc. - Extrinsic regulation
-
heart ragulation that results form neural and hormonal control;
parasympathetic and sympathetic nerve fibers - Preload
- the extent to which the ventricular walls are stretched; increased preload causes an increase in CO, decreased preload causes decrease in CO
- Starling's law of the heart
-
a law describing the relationshpi between preload and stroke volume;
describes the relationship between changes in the pumping effectiveness of the heart and changes in perload;
increased preload causes cardiac muscel fibers to contract with greater force and produce a greater stroke volume - Afterload
- the pressure the contracting ventricles must produce to overcome the pressure in the aorta nad move blood into the aorta
- Acetylcholine
-
the neurotransmitter produced by postganglionic parasympathetic neurons, binds to ligand-gated ion channels that cause cardiac plasma membranes to become more permeable to K+;
consequently, the membrane hyperpolarizes, heart rate decreases - Baroreceptor reflex
-
reflexes that detect changes in blood pressure and result in changes in heart rate and in the force of contraction;
sensory receptors are stretch receptors;
found in the walls of certain large arteries, such as the internal carotids and the aorta, function to measure blood pressure - Cardioregulatory center
- an area in the medulla oblongata where sensory action potentials are integreated to control heart rate
- Cardioaccelatory center
- the part of the cardioregulatory center that functions to increase heart rate
- Cardioinhibitory center
- the part of the cardioregulatory center that functions to decrease heart rate
- Chemoreceptor reflexes
- reflexes that help regulate the activity of the heart; chemoreceptors in medulla oblongata are sensitive to changes in pH and carbon dioxide levels
- Heart block
-
loss of functional conduction of action potentials through the conducting system of the heart;
caused by extra K+ in the extracellular fluid