Sec 30.3: The Heart & Circulation

Question 1

What are atria?

Answer 1

They are the two smallest chambers of the heart

Question 2

What are the ventricles?

Answer 2

They are the two larger chambers of the heart

Question 3

What is the septum?

Answer 3

It is a thick wall of tissue that separates the ventricles containing oxygenated and deoxygenated blood

Question 4

What are heart valves?

Answer 4

They are flaps of tissue that prevent blood from flowing backward
They open when atria or ventricles contract and close when they relax

Question 5

Why is the heart a powerful pump?

Answer 5

It is small in size, which allows the strong cardiac muscles to exert a great deal of force on the chamber
It can also respond to signals from the nervous system to change the speed and force of its pumping action

Question 6

How many contractions does the heartbeat consist of and where?

Answer 6

2 contractions, one in the atria and the other in ventricles

Question 7

Where do contractions begin and how?

Answer 7

They begin in the right atrium at a signal from the sinoatrial node

Question 8

What does the sinoatrial node (SA node) do?

Answer 8

Its cells generate an electrical signal that starts the wave of contractions, aka “pacemaker”

Question 9

What happens after the signal from the SA node?

Answer 9

The atria contract, and trigger a signal from the atrioventricular node (AV node)

Question 10

Where is the AV node located and what does it do?

Answer 10

It is located in the wall of the right ventricle and stimulates both ventricles to contract at the same time.

Question 11

Can the SA node be replaced?

Answer 11

Yes, it can be artificially replaced by an “artificial pacemaker”

Question 12

How does blood flow in the heart occur?

Answer 12

Oxygen-poor blood enters the heart through the vena cava into the right atrium. The SA node signals contraction, and blood is pumped into the right ventricle. The AV node signals contraction, and the ventricles contract, pushing the blood through the pulmonary artery (the only artery carrying oxygen-poor blood) to the lungs for gas exchange. Then, oxygen-rich blood is pumped back to the heart through the pulmonary vein (the only vein carrying oxygen-rich blood) into the left atrium. The atria contract, and the blood moves to the left ventricle, and when the ventricles contract, the blood is pushed through the aorta and to the body cells.

Question 13

What is the pulmonary circulation?

Answer 13

It occurs only between the heart and the lungs

Question 14

What is the function of the pulmonary circulation?

Answer 14

To carry oxygen-poor blood to the lungs, where it picks up O2, expels excess CO2 and water, and carries oxygen-rich blood back to the heart

Question 15

How many pulmonary arteries and veins are there?

Answer 15

Each lung is supplied by its own pulmonary artery and pulmonary vein.

Question 16

Where does the pulmonary circulation begin and end?

Answer 16

It begins in the right ventricle, where the oxygen-poor blood moves through the pulmonary artery to the lungs for gas exchange, then the oxygen-rich blood goes back through the pulmonary veins to the left atrium.

Question 17

What is the systemic circulation?

Answer 17

It occurs between the heart and the rest of the body except lungs

Question 18

What is the function of the systemic circulation?

Answer 18

To carry oxygen-rich blood to all cells and transport oxygen-poor blood back to the heart.

Question 19

Where does the systemic circulation begin and end?

Answer 19

It begins in the left atrium, then the atria contract and blood moves to the left ventricle, then the ventricles contract and the oxygen-rich blood is expelled through the aorta to the body cells, where gas exchange occurs. The now oxygen-poor blood moves to the vena cava to enter the right atrium. When the atria contract, the blood moves to the right ventricle and the pulmonary circulation resumes.

Question 20

How are the body’s oxygen needs regulated?

Answer 20

Sensors in the walls of major arteries in the pulmonary and systemic pathways send info to the medulla in the brain stem.
The medulla coordinates this info with signals from the respiratory system

Question 21

How is homeostasis maintained?

Answer 21

By matching heart rate and respiration rate with the body’s oxygen needs

Question 22

What happens to the circulations in extreme conditions?

Answer 22

Both circulations make sure the body’s brain, heart, and other major organs remain at a constant temperature.

Question 23

What happens during cold temperature?

Answer 23

Blood vessels to arms and legs constrict to keep torso and head warm.