Mid-Unit Summary: The Heart

The human heart is about the size of a first and weighs less than a pound. It is located in a cavity of the thorax called the mediastinum and is covered by the pericardium, a double sac of membranes that releases fluids to lubricate the heart and reduce friction. The three layers of the heart (as shown in the image below) are the epicardium which is the visceral pericardium, the myocardium which is the contractile part of the heart, and the endocardium which lines the chambers of the heart. 

The heart has four chambers that help regulate the blood: the right and left atria, which receive blood, and the right and left ventricles, which discharge blood. The valves of the heart - labelled in the image below - keep blood moving in one direction and prevent the back flow of blood. When listening to a heart beat, the "lub" sound happens when the tricuspid valve (between the right atrium and right ventricle) and the bicuspid valve (between the left atrium and left ventricle) contract. The "dub" sound is heard when the aortic and pulmonary valves close as the heart relaxes. The nodal system of the heart is composed of the SA (sinoatrial) node which is found in the right atrium and the AV (artrioventricular) node which is found where the atria and ventricles meet. This nodal system is made up of special tissue that causes the heart to beat uniformly at about 75 beats per minute. The cardiac cycle is the heat's rotation between systole (contraction) and diastole (relaxation) of both the atria and both the ventricles that work together to push blood through the body. For more information on how blood is circulated through the chambers of the heart, see my previous blog post from our heart chalk walk activity here

The circulatory system is a fluid-filled network of vessels through which materials move between the environment and cells of a multicellular animal. It's major components are the heart which continuously circulates blood, the arteries which take blood away from the heart, the veins which bring blood back to the heart, and blood which is the fluid being circulated. The image below depicts the structural differences between arteries and veins. The specific parts of the circulatory system are pulmonary veins and arteries, the aortic arch and trunk, the common carotid artery, the renal vein and artery, and the mesenteric arteries. Some accessory organs that aid in the circulation of blood are the lungs, kidneys, small intestine, large intestine, liver, spleen, and bone marrow. Blood pressure is measured by the systolic pressure, which results from the contraction of the ventricles, and diastolic pressure from the relaxation of the heart. To learn more about blood pressure, see my last blog post from our blood pressure lab here

Many blood vessels work together to aid in the circulation of blood through the circulatory system as shown in the diagram above. Veins are thin vessels that carry blood from the tissues to the heart. Arteries are elastic and contractile vessels that carry blood away from the heart and to the tissues. Capillaries are tiny vessels that connect arterioles (small arteries) to venules (small veins). Blood - the main material pumped through the circulatory system - has three components (depicted below): red blood cells, a buffy coat made up of white blood cells and platelets, and plasma. Blood's main functions are transportation, regulation, and protection. Different types of white blood cells in peripheral blood include neutrophils, basophils, eosinophils, lymphocytes, and monocytes, each of which has different responsibilities in the body. 

One of the main cardiovascular diseases is a heart attack, which is caused when blood supply to the myocardium is severely reduced or blocked and is usually due to atherosclerosis. Atherosclerosis is a disease that occurs when fatty material deposits on the inside of blood vessels, making it harder for blood to flow - the chronic inflammation is generally caused by excess polyunsaturated fats, omega-6, and damaged blood vessels that cause LDL (bad cholesterol) to stick to damaged cells causing plaque to develop, as shown in the image below. Another cardiovascular injury, an aneurysm occurs when a thin weakened portion of the blood vessel wall droops, and they are life threatening, especially if they burst. Cholesterol, a cause of atherosclerosis, comes in two types: LDL which sticks to arteries and HDL which cleans up the build up of LDL in arteries. A major effect of a heart attack which is often confused with a heart attack is cardiac arrest, which occurs when the heart stops beating entirely. Signs of a heart attack include chest pain/pressure, arm pain, nausea, shortness of breath, and pale/sweaty skin. Methods to diagnose a cardiovascular disease include an angiogram, an echocardiogram, an electrocardiogram (EKG/ECG), a stress test, or nuclear scanning. Factors that increase the risk of a heart attack are a lack of exercise, obesity, smoking, diabetes, high blood pressure, and high cholesterol. Thus, it's important to maintain good health to prevent a heart attack from occurring.

Blood Pressure Lab

When taking someone's blood pressure, the first number is the systolic blood pressure the second is the diastolic blood pressure. The systolic blood pressure measures the pressure of a person's blood when the ventricles of the heart contract and blood moves out of the heart. The diastolic pressure measures the pressure in the heart when the heart relaxes. Doctors use a stethoscope to measure a patient's heart rate and a sphygmomanometer to measure a patient's blood pressure. Sphygmomanometers measure a person's blood pressure by squeezing a person's arm and listening to the heart beat when the pressure is released. You can also use your thumb to read your pulse from your carotid or radial artery; however, it is not a reliable reading because your thumb has a pulse of it's own. When using a sphygmomanometer to take blood pressure, be sure that it is free of air and double check that the valve is tightly shut. Put the band around the person's upper arm and place a stethoscope underneath. Using the pump, add pressure to the sphygmomanometer to add pressure until the meter reads 150 mmHg. Once you've reached this pressure on the valve, open the valve to slowly release air. The recorder should listen for the heartbeat and mark the pressure at which they hear the first heartbeat. Likewise, they should record the pressure when they can no longer hear a heartbeat. The number recorded when the heartbeat is first heard is the systolic blood pressure and the number recorded when the heartbeat is no longer heard is the diastolic blood pressure. For this lab, I partnered with Michelle Koo and we measured each other's blood pressure and heart rate using the method described above. The results we got are recorded in the table below.

Heart Chalk Walk Reflection

When blood is traveling through the circulatory system, deoxygenated blood from the body enters the heart through the superior or inferior vena cava and empties into the right atrium. The deoxygenated blood then flows through the tricuspid valve and into the right ventricle. Once the right ventricle is filled, the blood is pumped through the pulmonary valve and into the pulmonary artery, which takes the blood to the lungs to be oxygenated. Once the blood has been oxygenated by the lungs, it returns to the heart through the pulmonary veins. This now oxygenated blood flows through the pulmonary veins and enters the left atrium, after which the blood is pushed through the bicuspid valve and into the left ventricle. Once the left ventricle is filled, the blood is pumped through the aortic valve and into the aorta, which takes the oxygenated blood to different parts of the body.

Unit 2 Reflection: Health

Health is a measure of our body's efficiency and overall well-being. The 5 aspects of life that contribute to a healthy lifestyle are stress, exercise, nutrition, sleep, and social interaction. A good analogy to explain health is that the 5 aspects listed are like 5 pillars of health. I learned in this unit how anytime one pillar is lacking, the others make up for it to ensure that the health of the body "stays standing." Ideally, if a person takes care of all 5 pillars, their overall well-being will be in optimal condition, which is why people should be sure to pay attention to all of the pillars. One very important aspect of being healthy is having healthy hormones - the "big 4" are insulin, leptin, glucagon, and cortisol. These hormones work together to maintain optimal glucose levels inside the body and control our biological cycles. The four keys to maintaining a healthy life style, even when you follow all of the suggestions from doctors and scientists, are adequacy, variety, moderation, and balance in everything you do. Don't stress, exercise, eat, sleep, or socialize too much or too little - do them all in moderation. The first pillar of health, stress, has three main stages: alarm, resistance, and exhaustion. The alarm phase refers to when a person's body pumps adrenaline to trigger the "fight or flight" response in reaction to some immediate stimulus. The second phase, resistance, refers to the body's reaction to long term stress, which may result in damage to the body. The last phase of stress, exhaustion, is the most extreme phase and can eventually even lead to death. Another pillar of health - exercise - deals with the intensity of workouts involving muscle-strengthening, bone-strengthening, aerobic, and flexibility-improving exercises. To uphold the third pillar, nutrition, it is important to maintain a balanced diet filled with vitamins and minerals. It's also important to get a sufficient amount of sleep during the night, especially REM sleep, because that is actually when your brain is most active and it is the time when your body repairs itself. Lastly, to maintain the fifth and final pillar, one must be socially active. As demonstrated by the Social Readings we discussed, being socially active can prevent many future diseases and contribute to a person's overall good health.

From the activities in this unit, I learned that I am overall pretty healthy. I need to, however, start eating healthier, sleep longer, and learn to manage my stress better. In order to do this, I will start paying attention to the nutrition facts and ingredients in the foods I eat, I will try to eat a more balanced diet, I will try to start sleeping earlier and nap when I'm tired, and I will work on my time management to reduce my stress. A healthy life is important to me because maintaining all the pillars of life will help me live longer and better and stay away from diseases like diabetes and heart problems. To promote health and wellness on campus, teachers should find a way to coordinate when big tests like Midterms and Projects in other classes are and do their best to make sure their tests and projects do not overlap with those in other classes. In addition, students should learn to procrastinate less. By managing their time better, they will not only be able to sleep earlier, but also reduce their stress. My biggest problem, by far, is definitely sleep. Here is a Tedtalk that I came across by Arianna Huffington entitled, "How to succeed? Get more sleep" that discusses just this - why we should sleep longer rather than brag about our sleep deficit: https://www.ted.com/talks/arianna_huffington_how_to_succeed_get_more_sleep. 

Throughout this unit, I understood most of the "big picture" concepts thoroughly, but missed a couple days of class due to tennis matches. This put me behind in some of the labs and lectures, making it harder for me to see the bigger picture during the following class when we moved on to a new lecture. I still don't fully understand how the hormones like leptin and cortisol function in our bodies as they have many factors influencing them and have complex cycles. Next unit, I will try to miss less classes, stay organized with the lecture notes and paste them into my notebook as soon as I get home, and get more sleep at night so I will be more attentive in class.

Sleep Diary

This assignment to keep a sleep diary made me extremely aware of my poor sleeping habits. According to my sleep diary, I get an average of 6.36 hours of sleep per night as opposed to the 9-10 hours of sleep that is recommended for teenagers. This explains why I often get extremely tired by the early afternoon, generally take a nap in the evening, and then can stay up late at night. I noticed during this exercise that I often couldn't concentrate as well during class in the morning as I could when I was doing my homework late at night. In addition, my parents complained a couple times this weekend that I was easily irritable which, as we learned in class, happens to be one of the effects of sleep deprivation. It would also explain why I've gotten sick a couple times this year already, as another effect of sleep deprivation is reduced immunity. From this exercise, I learned that I really need to start sleeping earlier and making sure I get at least 8-9 hours of sleep to ensure I don't throw off the secretion cycles of cortisol and melatonin in my body and to ensure I can be more awake and concentrated in class. This is especially important because I drive to school every morning and we learned from the reading, "The Promise of Sleep," how incredibly fast you can fall asleep when you're tired, without even knowing it.