The Heart

The human heart has four chambers and they are the right atrium, left atrium, right ventricle and left ventricle. The septum is a muscular wall that separates the right side of the heart from the left. The right side of the heart pumps deO2 blood to the lungs and the right side of the heart pumps O2 blood to the body systems. The atria are the receiving chambers, the right atrium receives deO2 blood from body systems via the superior and inferior vena cava, the left atrium receives O2 blood from the lungs via the pulmonary veins. The ventricles are sending chambers. The right ventricle sends deO2 blood to the lungs through the pulmonary valve, pulmonary trunk and the pulmonary arteries. The left ventricle sends O2 blood to the body systems through the aortic valve and aortic arch or dorsal aorta.

The heart has other things that make it works, for example, Atrioventricular valves separate the atria from the ventricle. There are two different types of AV valves and they are tricuspid valve which is on the right side and the bicuspid valve which is on the left side. They open when the atria contract and close when the ventricle contracts to prevent backflow. The chordae tendinae are tendon-like pieces of tissue, they keep the AV valves from inverting when the ventricles contract. Papillary muscle holds and supports the chordae tendinae.

The SA node if found along the wall of the upper right atrium chamber, it stimulates the simultaneous contraction of the atria and sends a nerve impulse to the AV node. The SA node initiates the heartbeat, this is why it has a nickname of being the pacemaker. The  AV node is in the lower right atrium close to the AV valve. When the AV node receives the nerve impulse from the SA node it fires to initiate the contraction of the large ventricles by sending the message through the purkinje fibres. All of this is what moves our blood around our body and it is what we feel when we feel the pulse or listen to the heartbeat.

EKG (Electrocardiogram)
This is a machine the measures the systolic and diastolic of the heart. It is measured and is represented by the letter P,Q,R,S and T. The P represents the simultaneous contraction of the atria (caused by the SA node), the QRS is the contraction of the ventricles (caused by the AV node and purkinje fibres) and the T is the recovery of the ventricles.

P= atrial systole (contract)

R= ventricular systole (contract)

S= atrial diastole (rest)

T= ventricular diastole (rest)

 

HOW DOES THE HEART BEAT ON ITS OWN?

The regulation of the heartbeat is under the influence of the autonomic nerve system. The part of the brain that governs the speed of the heart rate is called the medulla oblongata. It will speed up or down the heart rate when needed. Under normal circumstances, the heart controls itself. This is why the heart can still beat 2-5 min after it is removed from the body.

 

BLOOD PRESSURE

High blood pressure (hypertension) puts a constant strain on the tissues and it may cause capillaries to burst. If this happens in the brains it is a stroke, if it happens in the heart then it is a heart attack. The longer a person has high blood pressure, the greater the potential for tissue damage. Sometimes high blood pressure is normal for example when doing physical activities, but the brain should return the blood pressure back to normal (lower level). Low blood pressure (hypotension) is particularly not a good thing to have either. It can result from genetics, anemia, dehydration, blood loss and shock. Proper kidney function can only be maintained if there is a sufficient pressure for filtration. Some factors that can affect blood pressure can include:

1. Vessel Diameter (bigger=lower BP, higher=higher BP)

2. Blood viscosity (thick= higher BP, thin = lower BP)

3. Total Blood Vessel Length (more fat = higher BP, thinner = lower BP)

4. Cardiac output (faster heartbeat = higher BP, slower heartbeat = lower BP)

5. Stress (lots = higher BP, less = lower BP)