M6 physics

The heart:

• sustains blood circulations and can be modelled as a twin compression/suction pump;

• sustains blood circulations but cannot be modelled as a twin compression/suction pump;

• is not a pump.

The cardiac cycle has:

• three main phases: diastole, systole, pause;

• two main phases: diastole and systole;

• two main phases: systole and pause.

The walls of all blood vessels:

• are elastic and blood enters into the aorta by portions;

• are not elastic but blood enters into the aorta by portions;

• are elastic but blood does not enter into the aorta by portions.

The flow of blood in the aorta is:

• turbulent;

• laminar;

• turbulent and laminar.

If the flow of blood is laminar, the stretching walls of the vessels:

• smooth down the pulsations;

• do not affect the pulsations;

• increase the pulsations.

If the flow of blood is laminar:

• the larger total cross-section results in lower velocity;

• the smaller total cross-section results in lower velocity;

• the larger total cross-section results in higher velocity.

In all capillaries and veins the flow of blood is:

• laminar

• turbulent

• laminar and turbulent.

At systole:

• the walls of the aorta and arteries are stretched and a mechanical stress wave propagates along the vessels; that is a pulse wave;

• the walls of the aorta and arteries do not change their shape and size because the pulse wave is generated during diastole;

• the walls of the aorta and arteries are compressed and a mechanical stress wave propagates along the vessels; that is a pulse wave.

The heart rate is:

• the number of pulse waves per unit of time;

• the number of pulse waves per hour;

• the number of pulse waves per 24 hours.

Blood pressure is:

• the difference between the pressure of blood in the cardiovascular system and the atmospheric pressure;

• the pressure of blood in the cardiovascular system;

• the subtraction of the pressure of blood in the cardiovascular system from the atmospheric pressure.