heart Flashcards
(29 cards)
Where do you find semilunar valves?
The aortic and pulmonaryvalves arelocated at the base of the aorta and the pulmonary trunk respectively. Thesearealso called the “semilunar valves”.
What is the mediastinum?
Themediastinum(from Medieval Latin mediastinus, “midway”) is the central compartment of the thoracic cavity surrounded by loose connective tissue, as an undelineated region that contains a group of structures within the thorax.
Label and describe the apex, base and borders of a heart
• Located in the mediastinum – anatomical region extending from the sternum to the vertebral column, the first rib and between the lungs
• Apex at tip of left ventricle (near left nipple)
• Base is posterior surface
• Anterior surface deep to sternum and ribs
• Inferior surface between apex and right border
• Right border faces right lung
Left border (pulmonary border) faces left lung
- What is the thickest heart chamber?
left ventricle.
Theleft ventricleis responsible for pumping the blood around the heart and so it needs to have a strong muscle wall.
- Describe the specific pathway of conduction in the conduction system of the heart
Conducting cells transmit contractile stimuli to the myocardium. The cardiac conduction pathway consists of theSA node, theAV node, and the conduction fibers of thebundle of HisandPurkinje fibers. TheSA nodesets the rate of the heart and causes the atrium to contract
What do P, QRS wave and T wave correspond with?
The P wave represents the normal atrium (upper heart chambers) depolarization;
the QRS complex (one single heart beat) corresponds to the depolarization of the right and left ventricles (lower heart chambers);
the T wave represents the re-polarization (or recovery) of the ventricles
What is going on during the plateau phase of action potential in a cardiac contraction fiber? (hint: think about closure/opening of sodium, calcium, potassium channels)
Plateau: period of maintained depolarization
• Due in part to opening of voltage-gated slow Ca2+ channels - Ca2+ moves from interstitial fluid into cytosol
• Ultimately triggers contraction
• Depolarization sustained due to voltage-gated K+ channels balancing Ca2+ inflow with K+ outflow
Babies resting heart rate is higher/lower than adult heart rate?
Babies andchildrenyoungerthan2 years old havehigher heart ratesbecause their body metabolism is faster.Heart ratesdecrease aschildrengrow, and usually by the teen years theheart rateis in the same range as an adult’s.
- Define preload, and . What is the consequence of a greater preload on the cardiac muscle fibers just before they contract?
preload– Degree of stretch on the heart before it contracts
– Greater preload increases the force of contraction – Frank-Starling law of the heart – the more the heart fills with blood during diastole, the greater the force of contraction during systole • Preload proportional to end-diastolic volume (EDV)
– 2 factors determine EDV
1. Duration of ventricular diastole
2. Venous return – volume of blood returning to right ventricle
define contractility
Contractility – Strength of contraction at any given preload – Positive inotropic agents increase contractility
• Often promote Ca2+ inflow during cardiac action potential
• Increases stroke volume
• Epinephrine, norepinephrine, digitalis – Negative inotropic agents decrease contractility
• Anoxia, acidosis, some anesthetics, and increased K+ in interstitial fluid
define afterload
Afterload – Pressure that must be overcome before a semilunar valve can open – Increase in afterload causes stroke volume to decrease
• Blood remains in ventricle at the end of systole – Hypertension and atherosclerosis increase afterload
What is difference between systole and diastole?
systole-contraction
diastole-relaxation
Which hormones mimic the actions of the sympathetic nervous system?
– Hormones • Epinephrine and norepinephrine increase heart rate and contractility
• Thyroid hormones also increase heart rate and contractility
How much blood is left in each ventricle at the end of ventricular systole?
Sinceventricular systolebegan with an EDV of approximately 130 mL ofblood, this means that there isstill50–60 mL ofblood remainingin theventriclefollowing contraction. This volume ofbloodis known as theend systolicvolume (ESV).
What is end systolic volume?
End-systolic volume(ESV) is the volume of blood in aventricleat the end of contraction, orsystole, and the beginning of filling, ordiastole.
ESV is the lowest volume of blood in the ventricle at any point in thecardiac cycle. The main factors that affect the end-systolic volume areafterloadand the contractility of the hear
What is the formula for cardiac output?
Therefore, we can use theequationCO = HR x SV. Thisequationtells us that thecardiac outputequals theheartrate (HR), which is the number of heartbeats per minute, times thestroke volume(SV), which is thevolumeof blood pumped by the ventricles with each heartbeat.
How can you decrease cardiac output?
Conditions like myocardial infarction, hypertension, valvularheartdisease, congenitalheartdisease, cardiomyopathy,heartfailure, pulmonary disease, arrhythmias, drug effects, fluid overload,decreasefluid volume, and electrolyte imbalance are considered the common causes ofDecreased Cardiac Output
Define stroke volume
definitionofstroke volumeis thevolumeof blood pumped out of the left ventricle of the heart during eachsystoliccardiac contraction. Thisvolumemay be calculated as the difference between the left ventricularend-diastolic volumeand the left ventricular end-systolic volume
List examples of factor that lower the heart rate?
Parasympathetic nervesrelease acetylcholine which decreasesheart rate byslowing rate ofspontaneousdepolarization
What is the role of the fibrous skeleton of the heart?
Electrical insulator: createsa delay in contraction of atria and ventricles
What happens with the semilunar valves (closed or open) right before the ventricles contract?
Asventriclesrelax,some backflow permitted but blood fillsvalve cuspsclosing them tightly
As theventricles contract,ventricularpressure exceeds arterial pressure, thesemilunar valves openand blood is pumped into the major arteries. … This is due to the elevated pressures in the aorta and the pulmonary artery pushing the blood back toward theventriclesto close thesemilunar valves.
During isovolumetric relaxation the AV valves and the semilunar valves are open/closed?
all valves are closed! When the intraventricular pressures fall sufficiently at the end of phase 4, the aortic and pulmonicvalvesabruptlyclose(aortic precedes pulmonic) causing the second heart sound (S2) and the beginning ofisovolumetric relaxation.
The atrioventricularvalvesalso remain closedduringtheisovolumetriccontraction period.
The semilunarvalves openwhen the ventricular muscle contracts and generates blood pressure within the ventricle higher than within the arterial tree. When the heart muscle relaxes the diastole phase begins again.
What is the role of the coronary sulcus?
right coronary sulcus separates the right atrium and its auricle from the right ventricle inferiorly. The right coronary sulcus then passes inferiorly onto the diaphragmatic surface of the heart and traverses to the left.
Which veins drain the venous blood of the R and Lventricles to the coronary sinus?
The coronary sinus receives blood mainly from the small, middle, great and oblique cardiac veins. It also receives blood from theleft marginal veinand theleft posterior ventricular vein. It drains into theright atrium.
