4.4 Circulation Flashcards
(i)What kind of muscle is the heart made out of and what are its features?
-Myogenic muscle
-Can contract without nervous or hormonal stimulation
-Doesn’t fatigue, as long as it has sufficient oxygen and glucose.
Name the four chambers of the heart
2 Atrium - Right atrium and left atrium
2 Ventricles - Right ventricle and left ventricle
What is the function of valves
-To prevent the backflow of blood.
What are some adaptations of the atria?
Made from thin tissue as because they only flow blood to short distances (to ventricles)
What are some adaptations of the ventricle
Made from thick tissue as they must supply blood to longer distances (lungs or rest of body)
How can the AV resist so much pressure?
Strong tendious cords allow them to withstand huge amounts of pressure
Describe the structure of an artery and how its related to its function.
-Narrow lumen to maintain high blood pressure
-Elastic fibres which recoil to maintain pressure
-Smooth muscle lining to reduce resistance to blood flow
-Collagen to prevent rupture f artery
Describe the structure of a vein and how its adapted to its function
-Large lumen
-Relatively thin layer of muscle and elastic fibres as pressure is low
-Valves to prevent backflow
Describe the structure of a capillary to its function
-Cell wall made of one layer of flattened endothelium cells.
-One cell thick
-Allows for short diffusion pathway
-Easy exchange
(ii)Describe the circulation of blood in a fish
-Single circulation
-Blood flows from heart to gills
-Blood flows from gills to rest of body
-Blood then flows from body back to heart
What are the advantages that the human circulatory system has over the over the fish
1-Blood flows faster and at a higher pressure to the rest of the body
2- Blood flows slower at a lower pressure to the lungs which reduces risk of damage to the lungs
(iii)What are the main three stages in the cardiac cycle?
1-Diastole (Relaxation of the heart)
2-Atrial systole(Contraction of the atria)
3-Ventricular systole(Contraction of the ventricle)
Why is the mammalian heart divided into a right and left hand side
-To keep oxygenated and deoxygenated blood separated
-Which results in as much oxygen being carried to cells as possible
Describe the events which occur in atrial systole
- Atria contract and ventricles are relaxed
- AV valves open to allow blood from a high to low pressure
Describe the events which occur in ventricular systole
- Ventricles contract and AV valves close to prevent backflow to the atria. Semi-lunar valves are forced open which allows blood to be pumped out of the heart via aorta and pulmonary artery.
iv) What is meant by the term myogenic
-Can contract and relax without nervous or hormonal stimulation(external)
- Brings about depolarisation `
What are the three nerves which control the heart ?
-SAN
-AVN
-Bundle of His
Explain the process of the cardiac cycle
1-SAN sends a wave of electrical impulse across the myocardial tissue of both atria to the AVN which causes atrial systole
2-AVN sends wave of electrical activity between the ventricles to bundle of His
3-Bundle of His branches into two smaller fibres called the Purkinje fibres.
4-Wave of electrical activity is released by purkinje fibres and causes ventricles to contract at the same time
5- AV close to prevent flow to atria
6- SL opened by pressure and blood is forced into arteries
How do you calculate bpm?
1-Duration of one heartbeat then divided by 60.
Eg. 60/0.7 = 85.7 BPM
(ix)What is atherosclerosis?
-Hardening of the artery by damage of the delicate endothelium of an artery.
What leads to damage of the endothelium layer ?
-High blood pressure, high levels of cholesterol, diabetes ,smoking, obesity and old age.
What are the steps involved of atherosclerosis
1-Damage to endothelium wall (eg, via high blood pressure)
2-Inflammatory response occurs and macrophages accumulate in the damaged area
3-Lipids and cholesterol clump together with the macrophages and form fatty streaks or plaque
What is an atheroma
-The collection of macrophages, lipids cholesterol and platelets which have formed under the endothelium layer. (plaque)
What are the main two types of cholesterol?
High density lipoproteins and low density lipoproteins
How are HDL’s formed
-Formed from protein, cholesterol and unsaturated fats
-They transport cholesterol from body tissues to the liver to be broken down
-They may even help remove cholesterol from fatty plaques in the arteries
How are LDL’s formed
-Formed from saturated fats, cholesterol and protein
-They bind to cell membranes before being taken up by cells.
-If levels of LDL are high, cell membranes will become saturated so more remain in the blood
-This means blood cholesterol levels are high. This cholesterol can get deposited in artery walls causing an atheroma to form.
What is aneurism and how is it an effect of atherosclerosis ?
-If an area of an artery is blocked, pressure builds up behind the blockage
-The artery bulges and weakens the artery wall
-This weakened points can swell up like a balloon
-If it bursts, it leads to a haemorrhage and therefore a loss of blood to a region of the body.
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