Topic 6.2

Question 1

Who discovered the circulation of the blood with the heart acting as the pump?

Answer 1

William Harvey

Question 2

Arteries

Answer 2

• Vessels that carry blood from the heart to the tissues of the body
• Thick walls and elastic fibres

Question 3

Ventricles

Answer 3

• Main pumpting chambers of the heart
• Left ventricle pumps to the entire body
• Right ventricle pumps to the lungs

Question 4

What do ventricles have to pump blood

Answer 4

• Thick strong muscles (with elastic tissues)
• Small space in the middle to allow for passive recoil

Question 5

Why do arteries have thick walls?

Answer 5

• Withstand the constanty changing and intermittently high blood presure without bulging outwards (aneurysm) or bursting

Question 6

Annotate the diagram of artery

Answer 6

Refer to picture

Question 7

Systolic pressure

Answer 7

• Peak pressure reached in an artery (when blood is pumped from the ventricle)
• Pushes the wall of the artery outwards, widening the lumen and stretching elastic fibres in the wall

Question 8

Diastolic pressure

Answer 8

• Minimum pressure in the artery

Question 9

What mechanism does the body use to prevent diastolic pressure from becoming too low?

Answer 9

• The stretched artery walls recoil and squeeze blood in the lumen
• Saves energy while maintaining relatively high pressure
• Ensure the steady and continuous blood flow

Question 10

Vasoconstriction

Answer 10

• Wall of the artery contract
• Circumference is reduced and the lumen is narrowed
• Increases blood pressure
• Restricts bloodflow to part of the body

Question 11

Capillaries

Answer 11

• Narrowest blood vessels
• Thin wall
• Small diameter
• Branch and rejoin repeatedly to form a capillary network
• Transport blood to almost all tissues in the body

Question 12

Why is the capillary wall one layer thin

Answer 12

• Permeable
• Allows nutrient and waste exchange

Question 13

Outline the process of nutrient and waste exchange at the capillary

Answer 13

• Permeable capillary walls allow part of the plasma to leak out and form tissue fluid (contins oxygen, glucose, monomer nutrients)
• The fluid flows between the cells in the tissue, allowing the cells to absorb useful substances
• Cells excrete waste products into the tissue fluid
• Tissue fluid reenters the capillary network with the waste products

Question 14

Why does the permeability of capillary wall differ between tissues?

Answer 14

• Particular proteins and other large particles can reach certain tissues but not others
• Permeability also changes overtime in response to the needs of the tissues

Question 15

Veins

Answer 15

• Collect blood at low pressure from the tissues of the body
• Carry blood back to the atria of the heart
• Veins do not require thick walls and contain fewer muscle and elastic fibres
• Have valves

Question 16

Atrium

Answer 16

• Receives blood from veins
• Right atrium receives blood from the entire body
• Left atrium receives blood form the lung

Question 17

Outline the function of the valves in veins

Answer 17

• Prevent backflow due to low pressure
• if blood starts to flow backwards, it gets caught in the flaps of the pocket valve, which blocks the lumen when filled with blood
• When blood flows towards the heart, it pushes the flaps to the sides of the vein, opening the valve
• One direction only

Question 18

Label the diagram of the heart

Answer 18

Refer to picture

Question 19

Outline the double circulation in the human body

Answer 19

• One circulation to and from all other organs (systemic ciruclation)
• One circulation to and from the lung (pulmonary circulation)
• Blood is oxygenated by the pulmonary circulation

Question 20

Atherosclerosis

Answer 20

Development of fatty tissues called atheroma in the artery wall adjacent to the endothelium

Question 21

Describe how atheroma is formed

Answer 21

• Low density lipoproteins (LDL) containing fats and cholesterol accumulate
• Phagocytes engulf the fats and cholesterol by endocytosis and grow very large
• Smooth muscle cells migrate to form a touch cap over the atheroma
• Artery wall bulges into the lumen, narrowing it and impeding blood flow

Question 22

Coronary occlusion

Answer 22

• Narrowing of hte arteries that supply blood containing oxygen and nutrients to the heart muscle
• Lack of oxygen causes pain, known as angina, and impairs the muscle’s ability to contract
• The heart beats faster to maintain blood circulation

Question 23

Describe what happens when the atheromas ruptures

Answer 23

• The fibrous capcovering atheromas sometimes ruptures
• Stimulates the formation of blood clots that can block arteris supplying blood to the heart and cause acute heart probems

Question 24

Outline causes (increased risk) of atheroma

Answer 24

• High blood concentrations of LDL (low density lipoprotein)
• Chronic high blood glucose concentrations, due to overeating, obesity or diabetes
• Chronic high blood pressure due to smoking, stress, or any other cause
• Consumption of trans fats, which damage the endothelium of the artery
• Infection of the artery wall

Question 25

Sinoatrial node

Answer 25

- Specialized muscle cells in the right atrium - Initiate heartbeat - Pacemaker of the heart

Question 26

Describe the initiation of heartbeat

Answer 26

- Membrane of a heart muscle cell depolarizes when the cell contracts - Activates adjacent cells to contract - Sinoatrial nodes are the first to depolarize in each cardiac cycle

Question 27

Outline treatment for defective sinoatrial node

Answer 27

- An artificial pacemaker can regulate the heartbeat - An electronic device that is placed under the skin with electrodes implanted in the wlal of the heart - Initiate each heartbeat in place of the sinoatrial node

Question 28

Describe the propagation of electrical signal in each heartbeat

Answer 28

- SA node initiates the heartbeat while sending an electrical signal that spreads throughout the walls of the atria - Electrical signals propagate across interconnections adjacent fibres - The fibres are branched so the signal can be passed on to several places - This propagation of the electrical signal causes the whole of both left and right atria to contract - After a time delay, the electrical signal is conveyed to the ventricles (the atria pump blood to ventricles during the time delay) - Ventricles contract and pump blood out into the arteries

Question 29

With the help of a graph, describe how pressure changes in the atria and ventricles during the cardiac cycle

Answer 29

Question 30

State the structure in the brain that regulate the heartbeat

Answer 30

Medulla

Question 31

Describe how the cardiovascular centre regulate heartbeat

Answer 31

- Recieves inputs from receptors that monitor blood pressure, pH and oxygen concentration - Low blood pressure/low oxygen concentration/low pH cause the medulla to send a message to increase the flow rate of blood to the tissues

Question 32

Outline the effect of epinephrine on heart rate

Answer 32

Increases heart rate to prepare for vigorous physical activity

Question 33

Fill in the following chart of the cardiac cycle events

Answer 33