A & P Chapter 12 (Scanlon And Sanders)

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A & P Chapter 12 (Scanlon And Sanders)

The Heart

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What is the tip of the heart called?
The apex
Where is the apex of the heart?
Just above the diaphragm and left of the midline.
What is the heart enclosed in?
pericardial membranes
How many layers make up the pericardial membranes?
3 layers
Name the three layers of the pericardial membranes.
Fibrous pericardium.
Parietal pericardium.
Visceral pericardium.
Which is the outermost layer of the pericardial membranes?
The fibrous pericardium.
What does the parietal pericardium do?
It lines the fibrous pericardium.
Where is the visceral pericardium found?
On the surface of the heart.
What's another name for the visceral pericardium?
The epicardium
How many chambers make up the heart?
4 chambers
What are the upper chambers called?
The left and right atrium.
What are the lower chambers called?
The left and right ventricles.
What separates the lower chambers?
The ventricles are separated by the interventricular septum.
Describe the walls of the 4 chambers.
The walls are made of muscle called myocardium and lined with endocardium.
What does the right atrium do?
Receives blood from body or lungs.
What brings blood to the right atrium?
2 large veins return blood to the right atrium.
What are the two veins called that return blood to the right atrium?
Superior vena cava = carries blood from upper body.
Inferior vena cava = carries blood from lower body.
Where does blood go when it leaves the right atrium?
It goes through the tricuspid valve and into the right ventricle.
What's another name for the tricuspid valve?
Right atrioventricular (AV) valve.
What does the tricuspid valve do?
It prevents backflow of blood from right ventricle to right atrium when ventricle contracts.
What does the left atrium do?
Receives blood from the lungs.
How does blood get from the lungs to the left atrium?
Via 4 pulmonary veins.
Where does blood go when it leaves the left atrium?
It goes through the bicuspid valve and into the left ventricle.
What are two other names for the bicuspid valve?
Mitral valve.
Left atrioventricular (AV) valve.
What does the bicuspid valve do?
It prevents backflow of blood from left ventricle to left atrium when ventricle contracts.
When walls of the atria are stretched (by increased blood pressure), what happens?
Cells produce atrial natriuretic hormone.
What do the atria produce?
A hormone involved in blood pressure maintenance.
What happens when the right ventricle contracts?
The tricuspid valve closes and blood is pumped to the lungs through the pulmonary artery.
Describe the walls of the left ventricle.
They are thicker than those of the right, allowing the left ventricle to contract more forcefully.
Why does the left ventricle need to contract more forcefully?
So that it can pump blood to the body through the aorta.
What is the aorta?
The largest artery of the body.
What is the heart?
A double, two-sided pump
What does the right side of the heart do?
It receives deoxygenated blood from the body and pumps it to the lungs to get oxygen and release CO2.
What does the left side of the heart do?
It receives oxygenated blood from the lungs and pumps it to the body.
How do the pumps work?
Both pumps work simultaneously.
What contracts together?
Both atria contract together, followed by the contraction of both ventricles.
What are the right and left coronary arteries?
The first branches of the ascending aorta.
What do the coronary vessels do?
They supply blood to the myocardium.
What is the myocardium?
The muscle tissue that forms the walls of the chambers of the heart.
What happens if a coronary artery is obstructed?
The myocardium becomes ischemic.
What does ischemic mean?
Deprived of blood supply.
What does prolonged ischemia create?
An infarct - an area of dead tissue.
What is a myocardial infarction?
heart attack
Define cardiac cycle
Sequence of events in one heartbeat.
Describe the cardiac cycle
Simultaneous contraction of the two atria, followed fraction of a second later by simultaneous contraction of the two ventricles.
What are the two sounds of a heartbeat?
First = ventricular systole closing the AV valves.

Second = closure of the aortic and pulmonary semilunar valves.
What happens if any valve does not close properly?
An extra sound called a heart murmur may be heard.
The cardiac cycle is regulated by what?
By the electrical activity of the myocardium.
What special ability do cardiac muscles have?
The ability to contract spontaneously - nerve impulses not needed.
What is the sinoatrial (SA) node?
The natural pacemaker of the heart
What does the sinoatrial (SA) node do?
It depolarizes = allows entry of Na+ ions into the SA node's cell membranes.
Name the route for impulses of contraction
SA node > AV node > bundle of His > right and left bundle branches > Purkinje fibers > rest of the ventricular myocardium.
What is another name for the bundle of His?
The atrioventricular (AV) bundle.
What happens if the SA node does not function properly?
The AV node will initiate the heartbeat, but at a slower rate.
Mnemonic for the conduction pathway
SA-AV bundles His right and left bundles of Purkinje fibers to the rest of the ventricles.
What is a heartbeat recording?
An electrocardiogram (ECG)
What does a typical ECG consist of?
3 distinguishable waves
Name the three waves of an ECG
P wave.
QRS complex.
T wave.
What does the P wave represent?
Depolarization of the atria
What does the QRS complex represent?
Depolarization of the ventricles
What does the T wave represent?
Repolarization of the ventricles.
Define arrythmia
Irregular heartbeat
Define fibrillation
Rapid and uncoordinated ventricular beat.
Define pulse
Resting heart rate.
What is normal resting heart rate?
60-80 bpm
Define bradycardia
Less than 60 bpm
Define tachycardia
More than 100 bpm
Define cardiac output
The amount of blood pumped by a ventricle in 1 minute
Define stroke volume
The amount of blood pumped by a ventricle in 1 beat
Define ejection fraction
The percent of blood in a ventricle that is pumped during systole.
How does the nervous system affect the heart?
It can bring about necessary changes in:
heart rate
force of contraction
What does the medulla contain?
Two cardiac centers
Name the medulla's two cardiac centers
Accelerator center
Inhibitory center
What do the accelerator and inhibitory centers do?
They send impulses to the heart along autonomic nerves.
How does high blood pressure affect the heart?
It causes the left ventricle to work harder, which can make it weaker.
How does aging affect the heart?
It makes it less efficient.