heart

Question 1

Where do you find semilunar valves?

Answer 1

The aortic and pulmonaryvalves arelocated at the base of the aorta and the pulmonary trunk respectively. Thesearealso called the “semilunar valves”.

Question 2

What is the mediastinum?

Answer 2

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.

Question 3

Label and describe the apex, base and borders of a heart

Answer 3

• 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

Question 4

4. What is the thickest heart chamber?

Answer 4

left ventricle.

Theleft ventricleis responsible for pumping the blood around the heart and so it needs to have a strong muscle wall.

Question 5

5. Describe the specific pathway of conduction in the conduction system of the heart

Answer 5

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

Question 6

What do P, QRS wave and T wave correspond with?

Answer 6

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

Question 7

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)

Answer 7

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

Question 8

Babies resting heart rate is higher/lower than adult heart rate?

Answer 8

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.

Question 9

9. Define preload, and . What is the consequence of a greater preload on the cardiac muscle fibers just before they contract?

Answer 9

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

Question 10

define contractility

Answer 10

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

Question 11

define afterload

Answer 11

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

Question 12

What is difference between systole and diastole?

Answer 12

systole-contraction

diastole-relaxation

Question 13

Which hormones mimic the actions of the sympathetic nervous system?

Answer 13

– Hormones • Epinephrine and norepinephrine increase heart rate and contractility
• Thyroid hormones also increase heart rate and contractility

Question 14

How much blood is left in each ventricle at the end of ventricular systole?

Answer 14

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).

Question 15

What is end systolic volume?

Answer 15

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

Question 16

What is the formula for cardiac output?

Answer 16

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.

Question 17

How can you decrease cardiac output?

Answer 17

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

Question 18

Define stroke volume

Answer 18

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

Question 19

List examples of factor that lower the heart rate?

Answer 19

Parasympathetic nervesrelease acetylcholine which decreasesheart rate byslowing rate ofspontaneousdepolarization

Question 20

What is the role of the fibrous skeleton of the heart?

Answer 20

Electrical insulator: createsa delay in contraction of atria and ventricles

Question 21

What happens with the semilunar valves (closed or open) right before the ventricles contract?

Answer 21

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.

Question 22

During isovolumetric relaxation the AV valves and the semilunar valves are open/closed?

Answer 22

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.

Question 23

What is the role of the coronary sulcus?

Answer 23

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.

Question 24

Which veins drain the venous blood of the R and Lventricles to the coronary sinus?

Answer 24

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.

Question 25

Which blood vessels distribute oxygenated blood to the walls of the L atrium?

Answer 25

Thepulmonary veinsconduct blood into the left atrium, which pumps the blood into the left ventricle, which in turn pumps oxygenated blood into the aorta and on to the many branches of the systemic circuit.

Question 26

How do sympathetic neurons reach the heart?

Answer 26

thesympatheticnerves exit the medulla and travel down the spinal cord where they synapse with relatively short preganglionic fibers that travelto, and synapse within,sympatheticganglia. Postganglionic efferent fibers from the ganglia traveltotheheartand vasculature where they synapse at their target sites.

Question 27

Why can not cardiac muscle fibers not have tetanus?

Answer 27

The refractory period ofcardiac muscleis dramatically longer than that of skeletalmuscle. Thisprevents tetanusfrom occurring and ensures that each contraction is followed by enough time to allow the heart chamber to refill with blood before the next contraction.

Question 28

29.What are chemoreceptors, baroreceptors and proprioreceptos?

Answer 28

Achemoreceptor, also known as chemosensor, is a specialized sensory receptor cell which transduces a chemical substance (endogenous or induced) to generate a biological signal.
Baroreceptorsare mechanoreceptors located in the carotid sinus and in the aortic arch. Their function is to sense pressure changes by responding to change in the tension of the arterial wall. Thebaroreflexmechanism is a fast response to changes in blood pressure.
proprioceptors, roughly meaning “receptors for self.” The purpose ofproprioceptorsis primarily to give detailed and continuous information about the position of the limbs and other body parts in space (specialized mechanoreceptors also exist in theheartand major vessels to provide information about

Question 29

Where do you find each of these receptors?

Answer 29

Sensory receptorslocatedin the inner ear, muscles, tendons, and joints that use internal stimuli to detect changes in position or movement of the body or its limbs are calledproprioceptors.
Arterialbaroreceptorsare found most notably in arterial walls of the aorta of theheartand the carotid arteries. Low-pressurebaroreceptorsare most notably located in the large veins, pulmonary vessels of the lungs, and in the walls of theheartitself
PeripheralChemoreceptors
Locatedin both the carotid body and the aortic body, these receptors detect large changes in pO2as the arterial blood supply leaves theheart