2.3.1 blood circulatory system

Figure 4. The relationship of the heart and circulatory system to major visceral organs.

The circulatory song http://www.youtube.com/watch?v=q0s-1MC1hcE&NR=1

The cardiac cycle

• The human heart will undergo over 3 billion contraction cycles, as shown in Figure 5, during a normal lifetime.
• The heart beats in a rhythmic cycle. A complete cardiac cycle is one round of the heart pumping blood.
• The top half of the heart works as one unit.
• The bottom half of the heart works as one unit.
• The sino-atrial node (pacemaker) starts and regulates the process.
• The cardiac cycle consists of two parts: systole (contraction of the heart muscle) and diastole (relaxation of the heart muscle).

Atrial systole (0.1s)

• Atria contract simultaneously, pushing blood into the ventricles
• Ventricles are relaxed
• Atrio ventricular valves open
• Semi lunar valves close

Ventricular systole (0.3s)

• Atria relax
• Ventricles contract simultaneously
• Blood enters aorta and pulmonary artery
• Semi lunar valves open
• Atrio ventricular valves close

Diastole (0.4s)

• Atria and ventricles relax
• Atrio ventricular valves open
• Blood enters atria and ventricles
• Semi lunar valves close
• Back flow in arteries prevented

The heart beat can be heard as a sound that the valves make when they close. The ‘lub’ sound is made when the atrio ventricular valves close and the‘dub’ sound is made when the semi lunar valves close.

Figure 5

from mindset – (please check permission from this, found it in Biology 6th edition Campbell and Reece)

Cardiac Cycle: flow of blood through the heart

Excellent simple video illustrating the heart cycle.

http://www.youtube.com/watch?v=D3ZDJgFDdk0

Blood pressure

• The blood pressure is produced by the left ventricle contractions.
• The rhythm of ventricle diastole, often just referred to as diastole, causes the pulse, which can be felt by holding two finders to the side of the throat.
• Blood pressure oscillates with the contraction of the left ventricle.

Ideal blood pressure for an adult is:

Systolic pressure: 120 mm HG

Diastolic blood pressure: 80 mm HG

A usual rule is that systolic pressure should be 100 plus your age but nevermore than 140 and diastolic pressure should not be over 90.

Figure 6 The cardiac cycle. Image from Purves et al., Life: The Science of Biology , 4th Edition, by Sinauer Associates ( www.sinauer.com ) and WH Freeman ( www.whfreeman.com ),(please get permission)

Normal Heart Sounds

http://upload.wikimedia.org/wikipedia/commons/7/72/HROgg.ogg

Lung and pulmonary system

Khan Academy video on the pulmonary system. Overview on breathing.

http://www.khanacademy.org/video/the-lungs-and-pulmonary-system?playlist=Biology

• The lungs serve as the air-blood interface.
• Blood from the lungs is pumped into the pulmonary arteries.
• From the pulmonary arteries the vascular system branches into smaller and smaller vessels until the blood is flowing through thin pulmonary capillaries.
• These capillaries surround the alveoli in the lungs.
• At this point there are only two layers of cells separating the blood from the air.
• Carbon dioxide in deoxygenated blood diffused out of the blood.
• Oxygen in the lungs diffuse in to the blood oxygenating it Oxygen is absorbed.
• Oxygenated blood then returns to the heart vial the pulmonary veins.