Lab Exam-Lab 4

Question 1

Define pericardium

Answer 1

fluid-filled sac providing protection against friction

Question 2

Define epicardium

Answer 2

outer layer of heart wall (visceral layer)

Question 3

Define myocardium

Answer 3

muscle tissue of heart

Question 4

Define endocardium

Answer 4

inner layer of heart wall

Question 5

Describe the movement of blood through the heart

Answer 5

superior/inferior vena cava -> right atrium -> tricuspid valve -> right ventricle -> pulmonary semilunar valve -> pulmonary artery -> lungs -> pulmonary vein -> left atrium -> bicuspid valve -> left ventricle -> aortic semilunar valve -> aorta

Question 6

Which are the only blood vessels that are filled during diastole?

Answer 6

right and left coronary arteries

Question 7

Where does the right coronary artery originate from and where does it supply blood?

Answer 7

leaves right aortic sinus and supplies blood to right atrium and right ventricle

Question 8

Where does the left coronary artery originate from and where does it supply blood?

Answer 8

leaves the left aortic sinus, splits into the circumflex artery and paraconal artery

Question 9

What is then great cardiac vein?

Answer 9

begins at the apex of the heart, then ascends up to the ventricles, then curves left and opens into the left extremity of the coronary sinus (blood is returned to the right atrium)

Question 10

Define sinoatrial node

Answer 10

SA node/pacemaker. hundreds of autorythmic cells located in right atrial wall near superior vena cava

Question 11

Define atrioventricular node

Answer 11

AV node. special cardiac tissue located in right atrium along the lower part of interatrial septum

Question 12

Define atrioventricular bundle (bundle of His) and purkinje fibers

Answer 12

special cardiac fibers originating in AV node, extend down septum, become purkinje fibers at lateral walls of ventricles and papillary muscles

Question 13

Which part of the spinal cord control the sympathetic fibers of the heart?

Answer 13

sections T2-T4 in the spinal cord

Question 14

What other nerve signals to the SA node?

Answer 14

the VAGUS is the cranial nerve that has parasympathetic control over the heart. vagus decreases heart rate while the sympathetic nerves increase heart rate

Question 15

Define electrocardiogram

Answer 15

ECG. graphic record of the heart’s electrical activity (conduction impulse)

Question 16

Describe an ECG and what the graph means

Answer 16

1. the heart wall is completely relaxed, no electrical activity, constant ECG
2. P wave occurs when the AV node and atrial walls depolarize
3. atrial walls are completely depolarized, no change in ECG
4. the QRS complex occurs as the atria repolarize ? the ventricular walls depolarize
5. atrial walls are completely repolarized, ventricular walls completely depolarized, thus no change in ECG
6. the T wave appears on the ECG when the ventricular walls repolarize
7. When ventricular walls are completely repolarized, we are back at the baseline ECG (back to step 1)

Question 17

What are the steps to a myocardial infarction?

Answer 17

blood supply to part of heart is interrupted

• > occlusion (blockage) of a coronary artery
• > caused by an atherosclerotic plaque detachment
• > results in ischemia (restriction in blood supply)
• > oxygen shortage to heart tissue (death of myocites)
• > if left untreated, over time, infarction (heart attack)

Question 18

How can arterial plaques form?

Answer 18

hypertension -> arteriosclerosis (hardening of arteries) -> collection of lipids & macrophages in the wall of arteries -> calcification -> plaque

Question 19

Which direction does ischemia progress?

Answer 19

first occurs in the area of myocardium most distal to the arterial blood supply (endocardium). As time goes on, death progresses from the endocardium to the myocardium and finally to the epicardium

Question 20

What differences in the tissue occur during a myocardial infarction?

Answer 20

cardiac muscle: necrosis of myocites, infiltration of neutrophils, loss of nuclei, loss of branching pattern, contraction band necrosis, degradation of Na/K membrane gated channels (edema), loss of striations