Lesson 9 - Circulatory Systen II

Question 1

Anatomy of the Heart

Answer 1

Septum: wall of muscle separating the chambers
of the heart

Atrium: a chamber of the heart that receives blood from the body

Ventricle: a chamber of the heart that pumps blood to the body

The left side of the heart receives blood from the lungs and pumps it out through the systemic circuit

Valve: a set of flaps that allows blood to flow in only one direction

Aorta: the largest artery in the body

Vena cava: the largest vein in the body

Pulmonary veins: receive oxygenated blood from the lungs

Pulmonary artery: moves deoxygenated blood to the lungs

Semilunar valve: prevents the backflow of blood when the ventricles relax

Atrioventricular valve: prevents the backflow of blood from the ventricles to the atria

Chordae tendineae: tendons that support the atrioventricular valves

Question 2

The Cardiac Cycle

Answer 2

Cardiac Cycle: one complete heartbeat (contraction and relaxation of each chamber of the heart)

Under normal circumstances, a cardiac cycle
takes 0.8 seconds

Diastole: The ventricles are relaxed and fill with blood

Systole: ventricles contract and blood is pumped out

Question 3

Heart Sounds

Answer 3

The sound of the heartbeat is caused by the
closing of the heart valves!

lubb: caused by the closing of the atrioventricular valves (phase 3). This is a double sound because the left valve closes slightly before the right valve.

DUBB: occurs when the ventricles relax, and the semilunar valves snap shut (phase 5/1)

Question 4

Regulating Heart Rhythm

Answer 4

Myogenic muscle (heart muscle) has the unusual ability to contract and relax on its own!

The heartbeat is initiated in the sinoatrial (SA) node, which generates a regular pattern of electric signals which set the rhythm for the heartbeat

Atrioventricular (AV) node transmits the SA signal to the ventricular muscles via the Purkinje fibres which carry the signal

Heart rate can be adjusted by the nervous systems.

The sympathetic nervous system prepares the
body for stress (“fight or flight” system). Signals
from this system cause the heart rate to increase.

When the stress is no longer present, the brain
sends signals through the parasympathetic nervous system (“rest and digest” system) and the heart rate returns to normal.