Answers, BIO 2320, Heart

Objectives – 2, BIO 2320, HeartAnswers


1.Thoracic cavity, within mediastinum, a bit more on left

2.Pericardial sac protects the heart and prevents over distention of heart.

3.Endocardium, myocardium, epicardium

4.Pericardial cavity

5.Left & Right atria are separated by interatrial septum. Left and right ventricles are separated by interventricular septum. Valves between atria and ventricles are called atrioventricular valves. The pulmonary semilunar valve lies between the right ventricle and the pulmonary trunk; the aortic semilunar valve lies between the left ventricle and the aorta.

6.Sulcus is an external depression for the coronary vessels but is also an external feature dividing atrium from ventricle. Chordae tendineae attach inferiorly to AV valves keeping them from pointing backwards. Papillary muscle attach the chordae tendineae inferiorly in the ventricle; trabeculae carnea are irregular myocardium ridges

7.Aorta to coronary arteries to myocardium and then through cardiac veins to a big collecting vein called the coronary sinus which dumps into the Right atrium

8.Striated cardiac muscle cells linked by intercalated disc that carries excitement for contraction from one heart muscle cell to the next, linking them all together.

9.Sustained contraction without relaxation gives no time for filling the heart chambers with blood!

10.ATP from aerobic metabolism

11.Spontaneous depolarization can occur in all cardiac muscle cells but happens the quickest at the SA node, thus setting the pace for the entire heart since all cells are linked by the intercalated discs.

12.SA node spread to both atria, then to AV node with a brief delay for atria to finish their contractions, then down the AV bundle which travels through the interventricular septum, then to the purkinje = conduction fibers in the outer myocardium of ventricles.

13.Systole is the contraction phase and diastole is the relaxation phase. Highest systolic pressure is the LV since it has to pump blood from head to toes.

14.When LA has higher pressure than LV, the Left AV valve is open. As the LV contracts, its pressure exceed that of the LA and the Bicuspid valve closes causing the first heart sound. As the left ventricle is pushing blood into the aorta with high pressure, the aortic semilunar valve is open, but when the ventricle enters into diastole, quickly, its pressure drops below that of the elastic aorta resulting in semilunar valve closure causing the second heart sound.

15.Cardiac output is the volume pumped out of the ventricle in a minute CO = HR x SV. Cardiac reserve is the difference between the maximum CO and resting CO.

Normal CO is 5-6 liters/minute

16.Sympathetic NS increases heart rate, thus increasing CO. Parasympathetic NS decreases heart rate thus decreasing CO. Normal resting heart rate is 70 bpm

17.Volume ejected per beat. Normal resting SV is 80 mls/beat. As SV increases, so does CO

18.The volume in the ventricle after filling during diastole. SV = EDV – ESV. If EDV increases due to a longer diastole or more venous return, then Stroke Volume will also increase.

19.This is the volume left in the ventricle after contraction during systole. SV = EDV – ESV. The smaller the ESV, the greater the stroke volume – i.e. less blood is left in the ventricle and more is ejected. Sympathetic stimulation causes a more forceful contraction and therefore decreases ESV. Parasympathetic causes a weaker contraction and therefore increases ESV.

20.As the wall of the ventricle stretches due to an abundance of blood, the force of the ventricular contraction is greater, thus decreasing ESV, and preventing pooling of blood in the ventricle.

21.The cardiac center in the brainstem regulates heart function, as does exercise, temperature, sex, age, and certain ions, such as potassium and calcium.

22.Lub is closure of the AV valves

Dup is closure of the semilunar valves

23.Detecting and recording the electrical depolarization of the heart muscle. Lead describe where the electrodes are placed on the skin.

24.P wave represents atrial depolarization. QRS complex represents ventricular depolarization; T wave represents ventricular repolarization.