Heart & Circulatory System

Question 1

Why is a mammals double circulation more efficient than a fish’s?

Answer 1

Because the double system allows for different pressures in different areas so that both lungs and body can have blood pass through them optimally.

Question 2

Thickness of muscle wall in atria

Answer 2

Thin as it contracts to only exert a small / low pressure to push the blood a small distance into the ventricles.

Question 3

Thickness of muscle wall in right ventricle

Answer 3

It has a medium thickness as it must be enough pressure to push the blood to the pulmonary artery and the lungs and back.

Question 4

Left ventricle muscle wall thickness

Answer 4

This muscle is the thickest because it must contract to exert a high pressure to push the blood into the aorta and then a long distance to the whole body.

Question 5

What happens in an open circulatory system?

Answer 5

The heart pumps blood into spaces, haemocoel, in the body cavity. Tissues bathe in blood directly and exchange materials - no vessels. The blood flows slowly back to the heart. It moves to the Head region with assistance from the movement of muscles and valves. No respiratory pigment as no need to transport O2 in insects (and maybe all open circulatory systems….?)

Question 6

What are the two types of circulatory system?

Answer 6

Open and closed. Within the category of closed circulatory systems, they’re also single and double systems.

Question 7

Give examples of open and closed circulatory systems

Answer 7

Insects and humans

Question 8

Describe a closed circulatory system

Answer 8

Blood is in blood vessels and is pumped by muscular heart at high pressure resulting in rapid flow. Tissues are not in Direct contact with the blood but bathe in tissue fluid which can exit out the walls of capillaries. Blood contains haemoglobin pigment.

Question 9

Describe the single circulatory system

Answer 9

Blood from anywhere in the body may pass once through the heart before returning since gas exchange capillaries and those of other body systems are in the same circulation. E.g. fish

Question 10

Describe a double circulatory system

Answer 10

Blood must pass at least twice to the heart before returning to the same location, since it must complete a separate pulmonary circulation to the systematic circulation. This is the system of mammals.

Question 11

What is the systematic circulation?

Answer 11

Heart - body – heart

Question 12

What is the pulmonary circulation?

Answer 12

Heart-lungs-heart

Question 13

Advantages of double circulation?

Answer 13

the heart can increase the pressure post lungs so blood flows quicker at a higher pressure to body tissues. Therefore it is more efficient in the delivery of oxygen and nutrients. SYSTEMATIC CIRCULATION CAN CARRY BLOOD AT A HIGHER PRESSURE THAN PULMONARY

Question 14

What is the function of the heart?

Answer 14

To contract and relax, pumping blood as result. It is a muscles (cardiac). It is myogenic, meaning it beats from within the muscle itself.

Question 15

Ventricular systole basic happenings

Answer 15

Ventricles contract, volume decreases, and pressure increases. Atrioventricular valves are closed, semilunar open. Atria relax

Question 16

What are the stages of the cardiac cycle?

Answer 16

Diastole, atrial systole, ventricular systole -> diastole

Question 17

What happens at ventricular systole ?

Answer 17

Blood is forced through the semilunar valves (pulmonary and aortic valves) into the aorta and pulmonary artery.

Question 18

What happens at diastole?

Answer 18

Blood enters from the vena cava and pulmonary vein into the atria by venous return. The atrioventricular valves are open and semilunar are closed. Atria and ventricles are relaxed

Question 19

What are the basic happenings of atrial systole?

Answer 19

Atria contract, volume decreases, pressure increases, blood enters the ventricles down a pressure gradient. Atrioventricular valves are open and semilunar are closed. Ventricles relax

Question 20

When do the atrioventricular valves open?

Answer 20

when the pressure in the atria is greater than the pressure in the ventricles. The valves cusps are pushed open to allow blood to flow down a pressure gradient from the atria to the ventricles.

Question 21

When are the atrioventricular valves closed?

Answer 21

when the pressure in the ventricles is greater than the pressure in the atria. The valves cusps are pushed closed to prevent backflow of blood from the ventricles to the atria. When the atrioventricular valves closed they make a lub sound

Question 22

When are the semilunar valves open?

Answer 22

When the pressure is greater in the ventricle than in the pulmonary artery aorta. the valve cusps are pushed open to allow blood to flow down a pressure gradient from the ventricles to the body / lungs / heart/ head arteries

Question 23

When are the semilunar valves closed?

Answer 23

when the pressure is greater in the aorta / pulmonary artery than in the ventricles. The valve cusps are pushed closed to prevent backflow of blood from the aorta / pulmonary artery to the ventricles. When the semilunar valves close they make a dub sound.

Question 24

Tachycardia

Answer 24

An increased heart rate

Question 25

Heart block

Answer 25

Decreased heart rate

Question 26

Atrial fibrillation

Answer 26

Problem with atrial contraction

Question 27

Ventricular fibrillation (heart attack)

Answer 27

Problem with ventricular fibrillation

Question 28

Repolarisation

Answer 28

Restored to having no electricity across it

Question 29

Depolarisation

Answer 29

When something has electricity travel across it

Question 30

Non conductive connective tissue

Answer 30

Terminates the impulse, causes diastole , blood enters the ventricles from the veins.

Question 31

Purkyne fibres

Answer 31

cause ventricular systole, transmit the impulse up through the ventricles from the base upwards. Blood flows from the ventricles to the arteries through the semilunar valves.

Question 32

Sinoatrial node - SAN - pacemaker

Answer 32

Causes atrial systole, blood flows from the atria to the ventricles through the atrioventricular valves.

Question 33

Atrioventricular node - AVN

Answer 33

Delays impulse before sending it down the bundle of his, allows atria to fully contract before ventricle contracts.

Question 34

Bundle of His

Answer 34

Transmits impulse down the septum to the apex of the heart. it then starts to travel up the Purkyne fibres. For a split second there is enough pressure from the contraction of the base of the ventricles to shut the atrioventricular valve but not enough to open the semilunar. At this point there is no blood flow through the heart.