Human Heart

Question 1

How does the wall off the atria compare to the ventricles

Answer 1

Ventricles have much thicker walls

Question 2

What is the purpose of valves?

Answer 2

To prevent back flow

Question 3

What type of valves are the bicuspid and tricuspid and what side are they found?

Answer 3

• atrioventricular valves

- left valve is bicuspid and the right is tricuspid (t-right-cuspid)

Question 4

How are the valves held in place??

Answer 4

Valve Tendons are attached to papillary muscles, which contract with the ventricles holding the valves shut

Question 5

Where are the semilunar valves found?

Answer 5

Between the ventricles and aorta or pulmonary artery

Question 6

What tissue divides the left and right side of the heart?

Answer 6

• inter-ventricular septum

Question 7

Why are the walls of the right ventricle so much thinner than the left side?

Answer 7

• to produce less force and pressure in the blood
• the blood has a shorter distance to travel
• a lower pressure in the capillaries of the alveoli leads to less leakage of tissue fluid into the alveoli

Question 8

How is blood taken to the respiring tissues of the heart and returned?

Answer 8

• capillaries branch off from the coronary artery which are branches of the aorta
• the blood returns via the coronary sinus which takes blood directly into the right atrium

Question 9

What does myogenic mean?

Answer 9

• it can contract on its own without needing a nerve impulse

Question 10

What initiates the contraction of the heart muscles? And where is it located?

Answer 10

The SAN (sing-atrial node)
- top of the right atrium

Question 11

What are the 3 stages of the cardia cycle?

Answer 11

• Diastole
• Atrial systole
• Ventricular systole

Question 12

What occurs in diastole? And which valves are closed?

Answer 12

• atria and ventricle relax, the atria fully fills with blood and a a little trickles into the ventricles
• the semi lunar valves are closed

Question 13

What occurs in atrial systole

Answer 13

• SAN contracts transmitting an electrical impulse
• impulse causes both atria to contract pumping blood into the ventricles
• ventricles are electrically insulated from atria
• valves in the veins stop back flow of blood

Question 14

What occurs in ventricular systole? Including the valves

Answer 14

• electrical impulse from SAN reaches AVN and is sent on the the purkinje fibres with a short delay
• the purkinje fibres pass down the interventricular septum (electrically insulated) as the bundle of Hiss
• at the base of the ventricles the purkinje fibres spread out and initiate ventricular systole from the bottom upwards
• the AV valves are forced shut so blood pumps into the artery once pressure in ventricle is greater

Question 15

Looking at the heart pressure graph when do the valves open and close?

Answer 15

When the lines cross

Question 16

What does an electrocardiograph measure?? And how can this be useful?

Answer 16

The electrical activity of the heart

- can be used to detect irregular patterns of heart rate or heart attacks

Question 17

Equation for cardiac output?

Answer 17

Cardiac output = heart rate x stroke volume

Question 18

What is cardiac output?

Answer 18

The amount of blood flowing through the heart each minute

Question 19

How can heart rate be calculated?

Answer 19

Heart rate = 60/(cycle time(s))

Question 20

What is stroke volume?

Answer 20

The volume of blood pumped each beat

Question 21

Why does the heart increase the cardiac output when doing exercise?

Answer 21

• oxygen and glucose can get to the muscles faster
• carbon dioxide and lactic acid can be carried away from the muscles faster
• heat can be carried away from the muscles faster