6a. Heart and blood vessels Flashcards
What is the jounrney of blood through the heart
Vena Cava - Right atrium - AV Valve - Right ventricle - SL Valve - Pulmonary artery - Pulmonary vein - Left atrium - AV Valve - Left ventricle - SL Valve - Aorta
What are the different types of circulation in a mammal
-Pulmonary circulation - deoxygenated blood from body to the lungs
-Systematic circulation - oxygenated blood to rest of the body
Why is it an advanatge to have two seperate pumps
RHS generates pressure to send blood through the lungs where pressure drops
LHS generates more pressure so the blood can travel around body at a fast enough rate
what is the function of the atrioventricular and semilunar valves
Prevent backflow of blood
AV Valves prevent backflow from V to A
SL Valves prevent backflow from arteries to ventricles
What is a cardiac cycle
One complete sequence of contraction and relaxation
What is atrial systole
The contraction of the atria
What is ventricular systole
Contraction of the ventricular muscles
What is diastole
Relaxation of the heart muscle
How does blood flow
From regions of high to regions of low pressure
What happens during diastole
Heart relaxes
Artia fill with blood from the vena cava and pulmonary veins
SL Valves are closed
AV valves close until pressure in atria is too high and forces the valves open
What happens during atrial systole
Blood fills atria from vena cava and pulmonary veins
Artial muscle contracts, increases pressure in atria over the ventricals
AV Valves forced open and blood flows into the ventricles
What happens during ventricular systole
Ventricular muscles contract
Volume of ventricles increases, decreases pressure
AV Valves close
Blood pushed upwards, towards arteries
SL Valves open, blood flows into aorta and pulmonary artery
How does the heart muscle contract
Cardiac muscle is myogenic
Contractions arise from within the cardiac muscle
Sinoatrial node (SAN) is a group of cell within the wall of the right atrium
SAN originates the initial stimulus for contraction
What is the sequence of events that controls the cardiac cycle
SA Node sends an impulse spreading across both atria causing them to contract
Impluses then reach the AV Node where it is delayed
Delay allows the atria to fully empty and the ventricles to fill with blood
Impulses then sent down to the ventricles by the bundle of His - contains specialised conducting tissue - Purkyne fibres
Impulse spread up the ventricle wall from the base via Purkyne fibres causing ventricles to contract from the base up
Blood forced up into the arteries
What is the stroke volume
The volume of blood pumped out from one ventricle during each contraction.