Figure : Details arteries and veins connecting the heart to the lungs Red blood
has been oxygenated, blue blood is deoxygenated. . (Wikipedia -http://en.wikipedia.org/wiki/File:Illu_pulmonary_circuit.jpg)
Figure : Very detailed image of the lungs, it is not necessary or required to know all this detail but this is a fantastic image of the lungs –wikipedia (http://en.wikipedia.org/wiki/File:Respiratory_system_complete_en.svg).
Major organs and systemic system: associated major blood vessels the brain,
small intestines, liver, kidney.
Figure : Detailed illustration of the systemic circulation. http://en.wikipedia.org/wiki/File:Circulatory_System_en.svg
- All the organs of the body are supplied by blood.
- Each has an artery supplying the organ with blood from the heart, and veins returning blood to the heart.
- Arteries and veins have been named according to the organ which they supply blood to.
The circulatory system forms a closed system.
- Nutrients enter the circulatory system from the digestive system.
- These nutrients first move to the liver via the hepatic portal vein, the liver then controls the nutrient composition of the blood.
- Blood passes from the liver to the heart through the hepatic vein.
- Nutrients are then circulated throughout the body.
- Cells consume the nutrients in the blood and produce metabolic waste. T
- his metabolic waste is circulated in the blood, if it remains in the blood the blood would eventually become toxic.
- The kidneys are supplied with blood via the renal arteries and they remove metabolic waste from the blood, passing it to urine.
- The Brain is supplied with blood via the carotid arteries and the vertebral arteries. The blood is drained via the jugular veins. The brain is suppliedwith 15% of the total amount of blood pumped by the heart.
Mechanisms for controlling cardiac cycle and heart rate (pulse)
- The cardiac cycle is controlled by nerve fibers extending from nodes of nerve bundles through the heart muscle.
- An electrical signal is triggered in the node.
- The electrical signal then spreads through the fibers and causes the heart muscle to contract.
There are two nodes:
- The sinoatrial node (SA), which initiates the heart cycle. Electrical signals spread from the SA across the atria causing it to contact.
- The electrical signal also reaches the Atrioventricular node (AV) . Here the signal pauses, before spreading through the ventricles causing them to contract.
- The SA is able to initiate the electrical signal without any stimulation for the nervous system, but it can be controlled by the nervous system.
- The brain does not need to tell the heart to beat; it is able to beat on its own.
- The brain can make the heart rate increase, when for instance you are scared or are running.
- Hormones are also able to increase the heart rate.
Simple simulation of how electrical activity spreads over the heart.
Link : http://en.wikipedia.org/wiki/File:ECG_Principle_fast.gif
Measuring pulse rate: http://www.nlm.nih.gov/medlineplus/ency/article/003399.htm
How the nodes cause contraction
- Human heartbeats originate from the sinoatrial node (SA node) near the right atrium.
- Modified muscle cells contract, sending a signal to other muscle cells in the heart to contract.
- The signal spreads to the atrioventricular node (AV node).
- Signals carried from the AV node, slightly delayed, through bundle of His fibers and Purkinjie fibers cause the ventricles to contract simultaneously. Figure 13illustrates several aspects of this.