B5b: Circulatory systems and the cardiac cycle Flashcards
Why do many animals need a blood circulatory system
to ensure all their cells receive enough food and oxygen and to remove waste products(e.g. co2)
Describe single circulatory systems and where are they found(3+2)
One circuit from the heart
Links to a two-chambered heart
-one to receive and one to distribute blood
Found in fishes
-single blood circuit of the heart, gills and body
Describe double circulatory systems and where are they found(3+2)
two circuits from the heart
links to a four-chambered heart
-2 atria to receive blood(1 from lung, 1 from body) and 2 ventricles to distribute blood(1 to lung, 1 to body)
found in mamals
-heart and lung form 1 circuit, heart and rest of body form the other
What is the advantage of having a double circulatory system
bloody is under higher pressure compared with a single circulatory system
-allows materials to be transported more quickly around the body
What did Galen(2nd century) contribute to our knowledge about the heart(2)
knew about the chambers in the heart and that the heart acted as a pump as well as the importance of the pulse(he cut up animals)
thought arterial blood was made by the heart, while blood in veins were made by the liver
What did William Harvey(17th century) contribute to our knowledge about the heart
found out that blood circulated around the body over and over again and the existence of valves and capillaries
Describe pressure changes during blood flow(3)
As blood flows through arteries, veins and capillaries the pressure decreases
- veins have valves to stop backflow of blood
- high pressure would damage the fragile walls of the capillaries
What is the cardiac cycle
sequence of events as blood enters and leaves the heart
Describe the cardiac cycle(4)
blood flows into the two atria
atria contracts and atrio-ventricular valves open, pushing the blood into the ventricles
ventricles contract, atrio-ventricular valves close to prevent backflow into the atria, and semilunar vavles open, pushing the blood into the aorta and the pulmonary artery
semilunar valves close to prevent backflow into the ventricles
How does activity affect heart rate
More activity causes greater demand for oxygen and food, heart rate therefore increases to pump more oxygenated blood to your muscles
How else can heart rate be increased(3)
By the hormone adrenaline
- released when you get a shock or in danger
- increases heart rate to make sure the muscles have plenty of oxygen
How is heart muscle contraction controlled(4)
by a group of cells called the pacemakers
-produce a small electric current that stimulates muscle contraction
impulses from the SAN cause the atria to contract then stimulate the AVN
impulses from the AVN then cause the ventricles to
contract (makes sure that the atria contracts before the ventricles)
How can pacemaker cells be replaced
By an artificial pacemaker which controls the heart beat
What can be used to investigate heart action(3+3)
ECG(electrocardiogram)
-shows the electrical activity of the heart
-can show heart attacks or irregular heartbeats and general health of the heart
(-practice interpreting graphs)
Echocardiograms
- an ultrasound scan of the heart
- can show enlarged hearts, decreased pumping ability and faulty valves
