Chr. 20 - The Heart Flashcards
[20.1] Describe the heart.
An organ comprised mostly of cardiac muscle found in the mediastinum. The heart rests on the diaphragm in the thoracic cavity.
[20.1] What is the mediastunim?
An anatomical region from the sternum to the vertebral column, and from the first two ribs to the diaphragm.
[20.1] What is the apex of the heart?
The tip of the left ventricle, found at the inferior aspect of the heart.
[20.1] What is the base of the heart?
The posterosuperior aspect of the heart.
[20.1] What is the pericardium?
The membrane surrounding and protecting the heart. Allows for freedom of movement and vigorous beating contraction of the heart while minimizing friction.
[20.1] What is the fibrous pericardium?
The superficial layer of the pericardium composed of dense irregular connective tissue.
[20.1] What is the serous pericardium?
Deep layer of the pericardium, composed of two layers: parietal and visceral.
[20.1] What is the pericardial cavity?
The space between the parietal serous pericardium and the visceral serous pericardium.
[20.1] What is pericardial fluid?
Fluid inhabiting the pericardial cavity reducing friction.
[20.1] What are the layers of the heart wall?
- Epicardium
- Myocardium
- Endocardium
[20.1] Describe the epicardium.
Composed of two layers: the visceral serous pericardium composed of mesothelium; and a layer of fibroelastic tissue and adipose tissue. Contains coronary blood vessels.
[20.1] Describe the myocardium.
95% of the heart wall, this layer is composed of cardiac musscle wrapped in sheaths of endocardium and pericardium.
[20.1] Describe the endocardium.
A thin layer of endothelium laying over a connective tissue layer. Provides lining for the lumens of the heart. Continuous with lining of large blood vessels stemming from the heart.
[20.1] What are the chambers of the heart?
- Right atrium
- Left atrium
- Right ventricle
- Left ventricle.
[20.1] What are the atria?
Superior receiving chambers of the heart, receives blood from the body/lungs.
[20.1] What are the ventricles?
Inferior pumping chambers responsible for ejecting blood into the body/lungs.
[20.1] What is the auricle of the heart?
A pouchlike structure in each atrium increasing capacity of the atrium.
[20.1] Describe the sulci of the heart.
Series of grooves on the surface of the heart accommodating coronary blood vessels.
[20.1] What’s the coronary sulcus?
A deep sulcus encircling the heart and marking external boundaries between superior and inferior heart.
[20.1] What is the anterior interventricular sulcus?
A shallow groove on the anterior of the heart marking the boundary between right and left ventricles.
[20.1] What is the posterior interventricular sulcus?
A sulcus on the posterior aspect of the marking the boundary between ventricles.
[20.1] Describe the right atrium.
Forming the right superior surface of the heart receiving blood from three veins. Separated from the left atrium by the interatrial septum and from the right ventricle by the tricuspid valve.
[20.1] What are the pectinate muscles?
Muscular ridges in the right atrium extending into the right auricle.
[20.1] What is the fossa ovalis?
An oval depression in the interatrial septum, remnant of the foramen ovale, present only in a fetus before birth.
[20.1] What is the tricuspid valve?
A valve with three flaps separating the right atrium and ventricle. Prevents backflow into the atrium when the ventricle contracts.
[20.1] Describe the right ventricle.
Forms the inferior anteromedial aspect of the heart. Separated from the right atrium by the tricuspid valve and contains the pulmonary semilunar valve which prevents backflow from arteries leading to the lungs.
[20.1] What are the trabeculae carneae?
Muscular ridges within the right ventricle.
[20.1] What are the chordae tendinaea?
Cordlike tendons attaching the leaves of the tricuspid valve to the inside of the right ventricle at the trabeculae carneae. These attachment points are called papillary muscles.
[20.1] Describe the left atrium.
Receives blood from the lungs through pulmonary veins. Separated from the left ventricle by the bicuspid valve.
[20.1] Describe the left ventricle.
Receives blood from the left atrium. Separated from the left atrium by the bicuspid, and from the arch of aorta by the aortic semilunar valve.
[20.1] What is the ductus arteriosus?
A temporary blood vessel only found in a fetus, rerouting blood from the pulmonary arteries to the aorta.
[20.1] What is the ligamentum arteriosum?
A ligament connecting the arch of aorta to the pulmonary arteries; remnant of the ductus arteriosus.
[20.1] Why does the thickness of the myocardium vary between chambers?
Due to difference in function and pressure.
[20.1] What is the fibrous skeleton of the heart?
Four dense connective tissue rings surrounding valves of the heart, fusing with one another and merging in the interventricular septum. Also acts as insertion for cardiac muscle and provides insulation between atria and ventricles.
[20.2] What are the atrioventricular valves?
The bicuspid and tricuspid valve preventing backflow from ventricles into atria.
[20.2] What are the semilunar valves?
Crescent moon-shaped valves preventing backflow from arteries into ventricles.
[20.2] What are the two systems of circulation?
Systemic circulation and pulmonary circulation.
[20.1] Describe systemic circulation.
Blood flows from the left ventricle into the body and returns via the inferior vena cava, superior vena cava, and the coronary sinus.
[20.2] Describe pulmonary circulation
Blood flows from the right ventricle to the lungs, and back into the left atrium.
[20.2] Describe coronary circulation.
A subdivision of systemic circulation where blood flows to the heart. Coronary arteries branch off from the ascending aorta and supply the heart.
[20.2] List the main coronary arteries.
Left and right coronary arteries.
[20.2] Where does the left coronary artery travel?
Passes inferior of the left auricle and divides into two branches: anterior interventricular branch and the circumflex branch.
[20.2] Where does the right coronary artery travel?
To the right auricle and divides into posterior interventricular branch and the marginal branch.
[20.2] What are anastomoses?
Connections between two arteries supplying the same region.
[20.2] What is collateral circulation?
Alternate routes for blood delivery to regions or organs provided by anastomoses.
[20.2] What is the coronary sinus?
The main vein collecting deoxygenated blood from the coronary arteries.
[20.3] What are intercalated discs?
Irregular transverse thickenings of sarcolemma in cardiac muscle at cell junctions.
[20.3] What type of cell junctions is present in cardiac muscle?
Desmosomes and gap junctions.
[20.3] Why are gap junctions important in cardiac muscle?
Allow muscle action potentials to conduct through fibers quickly, resulting in uniform contraction of cardiac muscle.
[20.3] What are autorhythmic fibers?
Specialized cardiac muscle fibers exhibiting self-excitability.
[20.3] What are the functions of autorhythmic fibers?
- Act as a pacemaker, setting rhythm for contractions of the heart.
- Form the cardiac conductive system, a network the provides a path for each excitation produced.
[20.3] List the conduction pathway of the heart.
- Sinoatrial node
- Atrioventricular node
- Atrioventricular bundle
- Left and right bundle branches
- Purkinje fibers
[20.3] Describe the sinoatrial node.
Located in the right atrial wall inferolateral to the opening of superior vena cava. Produces pacemaker potentialat a rate of 60-100
[20.3] Describe the atrioventricular node.
Located in interatrial septum. Slows action potential due to cell structure and insulation, giving time for atria to fully contract.
[20.3] Describe the atrioventricular bundle.
Site where action potential travels from atria to ventricle.
[20.3] Describe the right and left bundle branches.
Pathway of conduction extending down interventricular septum to the apex.
[20.3] Describe Purkinje fibers.
Large-diameter fibers conducting action potential rapidly from apex of heart up the walls of the ventricle.
[20.3] What are contractile fibers?
Atrial and ventricular muscle fibers that participate in contractions of the heart.
[20.3] List the steps of action potential occurring in a contractile fiber.
- Depolarization
- Plateau
- Repolarization.
[20.3] How does the heart produce ATP?
Aerobic cellular respiration.
[20.3] What is an electrocardiogram?
A recording of the electrical signals of the heart.
[20.3] What are the main segments of an ECG?
- P Wave
- QRS Complex
- T Wave.
[20.3] What does the P wave represent?
Atrial depolarization
[20.3] What does the QRS complex represent?
Rapid ventricular depolarization.
[20.3] What does the T wave represent?
Ventricular repolarization.
[20.3] What are the main intervals of an ECG?
- P-Q interval
- S-T interval
- Q-T interval
[20.3] Where is the P-Q interval defined?
From the beginning of the P wave to the beginning of the QRS complex.
[20.3] What does the P-Q interval represent?
The time of conduction from beginning of atrial excitation to beginning of ventricular excitation.
[20.3] Where is the S-T interval defined?
From the end of the S wave to the beginning of the T wave.
[20.3] What does the S-T interval represent?
The time from completion of ventricular depolarization to the plateau phase of contraction.
[20.3] Where is the Q-T interval defined?
The start of the QRS complex to the end of the T wave
[20.3] What does the Q-T interval represent?
Time from the beginning of ventricular contraction to the end of ventricular repolarization.
[20.3] What is systole?
The phase of contraction of the heart.
[20.3] What is diastole?
The phase of relaxation of the heart.
[20.4] What is the cardiac cyle?
All of the events associated with one heartbeat.
[20.4] Describe atrial systole.
Contraction of atria lasting 0.1sec, contributing 25mL of blood to ventricles, for a final volume of 130mL.
[20.4] What is end-diastolic volume?
The volume of blood in the ventricle at the end of the relaxation period.
[20.4] Describe ventricular systole.
Ventricular contraction occuring simultaneously with atrial diastole and lasting 0.3s
[20.4] What is isovolumetric contraction?
A period of ~0.05s where valves of each ventricle are closed as it contracts, exerting force but not changing in shape.
[20.4] What is ventricular ejection?
The period when ventricular semilunar valves are open, lasting about 0.25s.
[20.4] What is end-systolic volume?
The volume remaining in each ventricle after contraction has occured.
[20.4] What is stroke volume?
Volume ejected per heartbeat per ventricle.
[20.4] Describe the relaxation period.
A period of 0.4s when atria and ventricles are relaxed - atrial and ventricular diastole.
[20.4] What is the dicrotic wave?
A wave on the aortic pressure curve due to rebounding of blood on closed cusps of the aortic valve.
[20.4] What is isovolumetric relaxation?
A period when all valves are closed and ventricular blood volume does not change.
[20.4] What is passive ventricular filling?
Passive filling of blood into the ventricular as pressure in ventricles drops below atria.
[20.4] List the heart sounds.
S1, S2, S3, S4
[20.4] Describe S1 heart sound.
“Lubb” sound produced by turbulence associated with closure of AV vales after ventricular systole.
[20.4] Describe S2 heart sound.
“Dupp” sound produced to turbulence associated with closure of semilunar valves.
[20.4] What is cardiac output?
The volume of blood ejected from left ventricle into the aorta, or by right ventricle into the lungsover a period of time, usually 1 minute.
[20.4] What is the equation for cardiac output?
Stroke Volume x Heart Rate = Cardiac Output
[20.4] What is the cardiac reserve?
The difference between an individual’s maximum cardiac output and resting cardiac output.
[20.4] List the factors affecting cardiac output.
- Preload
- Contractility
- Afterload
[20.4] What is preload?
Stretching of cardiac muscle fibers increasing force of contraction.
[20.4] What is the Frank-Starling law of the heart?
The relationship between increase in the stretching of muscle fibers and the greater force of contraction during systole.
[20.4] What is contractility?
The strength of a contraction at any preload.
[20.4] What are positive inotropic agents?
Substances increasing contractility.
[20.4] What are negative inotropic agents?
Substances decreasing contractility.
[20.4] What is afterload?
The pressure needed to be overcome in order for a semilunar valve to open
[20.4] What nervous system center regulates the heart?
The cardiovascular center of the medulla oblongata.
[20.4] Which receptors stimulate the cardiovascular center?
Proprioceptors
Chemoreceptors
Baroreceptors
[20.4] What are cardiac accelerator nerves?
Sympathetic nerves extending into SA, AV, and myocardium that trigger release of norepinephrine when stimulated. This results in an increase of heartrate, and an increasing contractility by promoting calcium entry.
[20.4] Which cranial nerve innervates the heart, and what effect does it have?
The vagus nerve, innervating with parasympathetic axons. Release acetylcholine, decreasing heart rate but not contractility.
[20.4] Which types of substances have an impact on regulation of heart rate?
Hormones, cations
[20.4] Which hormones affect heart rate, and how?
Epinephrine, norepinephrine, and thyroid hormones increase heart rate and contractility.
[20.4] How do cations affect heart rate?
Depends on the ion. Sodium and potassium levels have an inverse relationship, while calcium levels have a proportional relationship.
