The Heart Flashcards
What is the heart made out of?
Cardiac muscle
What is a double circulatory system?
RS of the heart pumps deoxygenated blood from the body along the pulmonary artery to the lungs
LS of the heart sends oxygenated blood from the lungs along the aorta to the rest of the body
Why is it an advantage for the human heart to have two separate pumps?
Pressure of the blood drops when it enters the lungs
LHS of the heart generates more pressure so that the blood can travel through the body at a fast enough rate to generate metabolic rate.
Why does the cardiac muscle need a rich supply of blood?
More O2 and glucose
High rates of aerobic respiration (releases energy in the form of ATP)
More ATP is produced for heart muscle contraction
Why are the walls of the left ventricle thick?
Because it needs to contract more to generate a higher pressure to pump the blood around the body than just to the lungs
What is the function of the valves?
Prevent the backflow of blood
Define diastole
Relaxation of the heart muscles
How does blood flow in terms of pressure?
From a region of higher pressure to a region of lower pressure
What happens during diastole? (WB)
Heart muscles are relaxed
Atria fills with blood from vena cava and pulmonary vein
Blood travels from a region of higher pressure (outside) to lower pressure (atria)
What happens during atrial systole? (WB)
The atrial muscles contract = decrease volume = increases pressure = atrioventricular valves open = blood flows from atria at a higher pressure to the ventricles at a lower pressure
What happens during ventricular systole? (WB)
The ventricular muscles contract = decreases volume = increases pressure = atrioventricular valves close and semilunar valves open = blood flows from ventricles at a higher pressure to the arteries at a lower pressure
Why do the atrioventricular valves close during ventricular systole?
Pressure is greater in ventricles than atria
Blood flows from higher pressure to lower pressure- blood would flow back into atria
Cardiac output formula (with units)
Cardiac Output = Stroke Volume x Heart Rate
dm3min-1 = cm3 x bpm
Define stroke volume
Volume of blood pumped out from one ventricle during each contraction
Define cardiac output
Total volume of blood pumped out from one ventricle per minute
How is the heart affected during exercise
HR + SV +CO all increase
Trained athletes hearts get bigger= >SV = >CO
How is the cardiac cycle controlled? (WB)
A wave of electrical activity is sent out from SA node (cells in right atrium)
Impulses reach the AV node where it is delayed= allows atria to empty blood + ventricles fill with blood
Electrical impulses transmitted down to ventricles by Bundle of His = contain Purkyne fibres
Impulses spread up ventricle wall from base via Purkyne fibres = causing ventricles to contract from base upwards
Blood is forced into arteries
Role of arteries
Carry blood away from the heart at high pressures
Role of artierioles
Control blood flow to capillaries
Vasoconstriction- small lumen, reduces
Vasodilation- large lumen, increases
Role of veins
Carry blood to the heart at low pressures
Role of capillaries
Exchange of materials between blood and body cells via diffusion
How are the arteries adapted to their function?
Thick walls to withstand high pressure
Single layer of endothelium cells = reduces friction between blood and blood vessel walls
Lots of elastic tissue = stops the fluctuation in pressure of blood
How are the arterioles adapted to their function?
Lots of muscle tissue
Single layer of endothelium
What do veins contain?
Valves
