Chapter 16- Cardiovascular system 1 Part 1 (2) Flashcards
What do the atrioventricular valves do?
Prevents backflow from ventricle to atrium when the ventricle contracts.
How many flaps does the right AV and left AV have?
The right AV has three flaps (tricuspid valves)
The left AV has two flaps (bicuspid valves)
When the heart is relaxed, what do the flaps do?
The flaps hang down into the ventricle below.
When the ventricle contracts in the AV, what happens to the intra ventricular pressure?
It rises, forcing the blood against the valve flaps which closes the valve and prevents blood flow.
What does the chordae tendineae do?
Prevents flaps getting blown upwards into the atria by the force of the ventricular contraction.
What do the semi lunar valves do?
This prevents backflow from the two large arteries back into the ventricles.
When the ventricles contract in the semi lunar valves, what happens?
Intraventricular pressure rises above the pressure in the aorta.
As a result, the valves are forced open and blood flows out.
When the ventricles are relaxed in the semi lunar valves, what happens?
Blood flows backwards towards the heart.
The cusps fill forcing them to close. As a result, no blood re-enters the heart.
No valves guard what?
The venae cavae or the pulmonary veins.
Vein defects include:
1- Stenosis- narrowing of the valve
2- Regurgitation- when the valves fail to close tightly
Defective valves are replaced with what?
Artificial valves
The cardiac cycle is composed of what phases?
Phases of diastole (relaxation) and systole (contraction)
CARDIAC CYCLE PROCESS ON DOC
CARDIAC CYCLE PROCESS ON DOC
How is cardiac muscle similar to skeletal muscle?
Cardiac muscle is similar to skeletal muscle in that it is striated and is capable of generating great force.
Cardiac muscle does differ from skeletal muscle in that:
1- Cardiac fibres branch
2- Cardiac muscle has more mitochondria and myoglobin
3- Cardiac muscle contains special calcium (Ca2+) channels
How are cardiac fibres joined?
By intercalated discs
Adjacent myocytes are joined by what?
Intercalated discs
What are intercalated discs?
These are bands of proteins and gap junctions that ensure there is a tight coupling between adjacent cells and sharing of the cytoplasm
What is syncytium?
A collection of cells that operate as one
Why is syncytium functionally important?
Because a partial contraction would be insufficient to pump blood all the way around the body.
Cardiac muscle forms two, largely independent syncytia:
1- One around both atria
2- Another around both ventricles
Why is there a high number of mitochondria and myoglobin in cardiac muscle?
Because cardiac muscle relies almost exclusively on aerobic respiration
Name fuel molecules for cardiac muscle
1- Glucose
2- Lactic acid
