pack 6a heart and blood vessels Flashcards
(23 cards)
why is it an advantage for the human heart to have two separate pumps
- right side generates pressure to send blood through the lungs where pressure drops
- when it returns to left it generates more pressure so the blood can travel around the body at a fast enough rate to generate high metabolic rate
coronary arteries and why they are needed
- they deliver oxygenated blood to the cardiac muscle that makes up the walls of the heart
- cardiac muscle needs a good supply of oxygen and glucose for high rates of aerobic respiration to produce a lot of atp for heart muscle contractions
heart structure
read in booklet page 4
tendinous cords
- inelastic connective tissue attached to the atrio valve prevents the valves from inverting
why is the left ventricle thicker
needs to contract with more force and generates a higher pressure
pressure principle
blood flows from a region of high pressure to a region of low pressure
diastole
what happens
valves
- the heart muscles relaxes during this time the atria again fill with blood from the vena cava and pulmonary veins
- atrioventricular valve - slightly open
- semi lunar - closed
atrial systole
- blood fills the atria from the vena cava and pulmonary vein. the atrial muscle contracts, increasing the pressure above that of the ventricle
- this forces the av valves open and blood flows into the ventricle
ventricular systole
- the ventricle muscles contract
- the volume of the ventricle decrease, increasing the pressure
- this causes the av valve to close
- the blood is pushed upwards, towards the arteries at the top of the heart
- the semi lunar valves open and blood flows into the aorta and pulmonary artery
soso graph
in booklet page 9
myogenic
contractions arise from within the cardiac muscle itself
sequence of events that controls the cardiac cycle
1) a wave of electrical impulse is sent out from the sa node
2) this spreads across both atria, causing them to contract
3) the electrical impulse reaches the av node where it is delayed
4) this delay allows the atria to fully empty blood into the ventricle before they contract
5) av node sends out electrical impulse
6) after the delay, the impluse spread down the ventricle in the bundle of his
7) the impulse is transmitted to the base of the ventricle where it passes up the purkinje fibres
8) the ventricle contracts from the base upwards, blood is forced up into the arteries
cardiac output
CARDIAC OUTPUT= STROKE VOLUME * HEART RATE
- stroke volume is the vol of blood pumped out from one ventricle during each contraction
what are the livers and kidneys blood vessels called
liver = hepatic
kidney = renal
capillaries
1) walls consist only of the lining layer or endothelial layer - very thin distance allows rapid diffusion of material
2) they are numerous and branched - provides a large surface area for diffusion
3) low blood pressure - allows excahnge of o2 and co2 and glucose. blood flow much slower allows more time for exchange of material
artery
- heart to tissues
- thick muscular walls allows smaller arteries to be constricted and dilated in order to control vol
- elastic layer larger compared to veins
+ during systole stretched
+ during diastole recoils
maintains high blood pressure and smoothes pressure created by surges created by beating of heart - thick walls - withstand higher pressure
- no valves except in aorta and pulmonary artery
arteriole
- relatively larger muscle layer and lumen - contraction of muscle layer allows constriction of the lumen
+ controls blood flow between arteries and capillaries - elastic layer is thinner because blood pressure is lower
- thickness of vessel wall is smaller
- no valves
veins
- muscle layer is thinner carry blood away from tissues so constriction and dilation does not control the flow of blood to tissues
- elastic layer is thinner as no surges of blood
- thickness of vessel wall is smaller as little risk of bursting
what is coronary heart disease
- fatty material build up inside the walls of the coronary arteries that supply the heart muscle with blood
- this narrows them and reduces the flow of blood through them, resulting in a lack of oxygen for the heart muscles
- fatty material bulids up over time, further restricting blood flow and it can lead to thrombosis - blood clot
- blocks the coronary artery completely causing a myocardial infraction
- some of the heart tissue is damaged and may die
risks that are unavoidable
inheritance/ gender/ increasing age
smoking risk with CHD
1) smoking
- nicotine: increases the heart rate and also causes narrowing of the artery lumen and so increases blood pressure
diet risk with CHD
2) diet
- high blood cholesterol eating a diet high in saturated fat can lead to elevated levels of LDL cholesterol in the blood, which in turn can lead to atheroma
- eating fewer saturated fats and more unsaturated fats decreases LDL and increases HDL
- high levels of salt raise blood pressure
high blood pressure risk with CHD
3) high blood pressure
- prolonged stress, certain diets and lack of exercise, increases the risk of high blood pressure
- higher the blood pressure the greater the risk of damage to the artery endothelium, thus starting atheroma formation
