Circulatory System

THE HUMAN HEART

FEATURES OF THE HUMAN HEART

• The heart is a muscular organ about the size of a fist, located just behind and slightly left of the breastbone.

• The heart pumps blood through the network of arteries and veins called the cardiovascular system.

• The human heart has 4 chambers. The upper two chambers are called the atria, whereas the lower two chambers are known as the ventricles. The right atrium and right ventricle are referred to as the right heart, whereas the left atrium and left ventricle are referred to as the left heart.

• The right atrium receives blood from the veins and pumps it to the right ventricle.

• The right ventricle receives blood from the right atrium and pumps it to the lungs, where it is loaded with oxygen.

• The left atrium receives oxygenated blood from the lungs and pumps it to the left ventricle.

• The left ventricle (the strongest chamber) pumps oxygen-rich blood to the rest of the body. The left ventricle’s vigorous contractions create our blood pressure.

• The Septum plays an important role, it separates the atria and the ventricle in such a way that it kind of forms a barrier between the chambers of the heart which prevents the mixing of oxygenated (oxygen-rich) and deoxygenated blood (oxygen-poor).

• The valves prevent the backflow of blood.

FUN FACTS ABOUT THE HEART

FACTORS WHICH AFFECT THE HEART RATE

These factors play a role in directly affecting heart rate while running or walking:

• Emotions and anxiety can raise your heart rate! Unlike an automobile that is purely mechanical, we are not solely governed by working parts. Some days you can “feel” your way to a higher HR.

• Body Temperature: If you become too hot or too cold your body senses a thermal stress load. Blood is sent to your skin to enhance heat dissipation to cool you or increases blood flow to warm you. Apparent temperatures (which account for humidity or wind chill) above 70 degress (F) and below 35 degrees (F) will increase your heart rate at least 2-4 beats per minute. Over 90% humidity can equal as much as a 10 beat increase in heart rate.

• The terrain. Walk or run uphill and your HR increases. Walk or run downhill and your HR decreases.

• Wind. Walking or running with the wind at your back is easy, therefore HR decreases. Walking or running into the wind is more difficult: HR increases.

• Dehydration. As you become increasingly dehydrated during a long walk, hike, or run, your blood becomes thicker and waste products build up in bloodstream. Your heart will work harder to maintain constant cardiac output. A fluid loss of 3% of body weight increases pulse rate because of decrease in circulating blood volume.

• Diminishing glycogen stores — your muscles primary fuel source. As the fuel depletes, in order to maintain the same walking or running pace, your HR rises.

• Insufficient nutrition. HR increases.

• Insufficient sleep. HR increases.

• Insufficient recovery after a long hike, run, or other hard workouts. HR increases.

• Recent illness — or — a signal of impending illness. You guessed it!

• Medication – depending upon the medication, heart rate can either decrease or increase. Be certain to ask your physician about any medication you are taking and its effects on your exercise heart rate.

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