Organisation- the circulatory system

double circulation

double circulation is comprised of 2 systems: one that takes blood to the lungs for gas exchange (the pulmonary system), the other takes blood to the tissues (the systemic system). Blood travels through the heart twice on its journey around the body.

why is the heart referred to as a double pump?

the heart is known as a double pump because the blood travels through the heart twice: once to the lungs, once to the body.

artery function

carries blood away from the heart at high pressure

artery adaptations (4)

1. thick muscle walls makes them strong and able to cope with the high pressure at which blood is being pumped out by the heart

2. muscle can contract and divert blood

3. elastic fibres stretch when the muscle opens/contracts

4. collagen stops it from collapsing

vein function

carries blood back to the heart at low pressure

veins adaptations (3)

1. thinner walls than arteries as blood is at a lower pressure

2. wider lumen: low pressure means slower blood flow, wide lumen counteracts this

3. valves prevent the backflow of blood

capillaries functions (2)

1. waste products move out of cells and into the blood (e.g. CO2)

2. food and oxygen move out of the blood and into cells

capillaries adaptations (exchange surface, 2)

exchange is efficient due to:

1. thin walls (one cell thick)

2. pass very close to cells, short diffusion path

platelets features and functions

• tiny fragments of cells suspended in plasma

• help blood clotting (which helps to stop bleeding) by clumping together

• no nucleus (they aren’t cells)

white blood cells features and functions

• defends against pathogenic microbes that get into the body

• has a nucleus

• can change shape (to engulf pathogens)

• lymphocytes make antibodies

red blood cells features and functions

• no nucleus so there’s more space for haemoglobin which binds to oxygen at the lungs then carries it to the rest of the body

• biconcave shape to maximise surface area

• small and flexible to fit through narrow capillaries

plasma features and functions

• made up of water, proteins and other solutes

• carries waste: CO2 from tissues, urea from liver, hormones from glands

how is the heartbeat coordinated? (5 steps)

1. electrical impulses are initiated from the pacemaker in the wall of the right atrium

2. these cause the atria to contract (systole)

3. there is a short delay for the ventricles to fill

4. the atrioventricular node (AVN) takes the electrical impulse to the base of the heart via bundles of his, and causes the ventricles to contract from the apex upwards (ventricular systole)

5. the cardiac muscle then relaxes (diastole)

main factors which can lead to Coronary Heart Disease

• smoking

• drinking excessive amounts of alcohol regularly

• lack of physical activity

• poor diet

• high cholesterol

• high blood pressure

• diabetes

• genetic factors

atherosclerosis

where your arteries become narrowed, making it difficult for blood to flow through them. this means that less glucose and oxygen reaches the heart for respiration so less energy is available for the heart to contract; if the cells are starved of nutrients, they can die and this leads to a heart attack.

what are statins?

statins are drugs that reduce cholesterol in the body by lowering its production in the liver- less cholesterol means less atherosclerosis in your coronary arteries

what are some pros of using statins?

• they help to lower cholesterol

• they protect against Alzheimer’s and other conditions

• better for people with inherited high cholesterol

what are some cons of using statins?

• they cannot be prescribed to people who: have liver disease, or are pregnant/breast-feeding

• can experience side effects such as headaches and memory loss

• can damage organs

what are stents?

stents can be used when a narrowed/blocked artery can be stretched open- the stent is inserted to restore and maintain blood flow

what are pros of using stents?

• can be used where drugs are less effective

• long term solution

• safe operation (doesn’t involve surgery)

what are cons of using stents?

• risk of bleeding, heart attack or stroke

• risks depending on patient’s age, health, and possible previous heart attacks

how does coronary bypass surgery work?

bypass grafts create an alternate route for blood flow

what are cons of coronary bypass surgery?

• it’s much more difficult to perform

• more risks because it’s a surgery

• more invasive

what happens during a heart attack?

• blood is blocked so cannot reach parts of the heart

• tissue doesn’t receive enough oxygen

• cells die

• heart cannot contract synchronously (can stop contracting completely)

• heart attack

risks of heart transplants

• risk of infection and blood clots as they involve surgery

  → patient would have to take anticoagulants (they stop your blood from clotting), which can leave you vulnerable

reasons why a biological heart transplant might be better than artificial

• artificial hearts have mechanisms which can wear out, biological ones do not

• artificial hearts present a rick of motor failure and therefore may not last very long, biological hearts are long-lasting

reasons why an artificial heart transplant might be better than biological

• biological hearts present a risk of rejection by the immune system so immunosuppressants have to be taken, leaving the patient vulnerable

  → artificial hearts do not present this risk as they are non-living material