By John Murphy
Menlo School senior Gabriel Morgan will be awarded U.S. Squash Scholar-Athleteon Sunday at Drexel University in Philadelphia. A two-time award winner, Morgan is recognized for academic excellence and maintaining a GPA above 3.5 during the 2014-15 squash season.Â Morgan and fellow award-winners will take part in special glass-court award ceremony and presentation during the U.S. Open Squash Championships.
Here are a couple of fund-raisers for South San Francisco schools:
A 5-kilometer run/walk — the Run for Schools — is Saturday, May 4. The race starts at South San Francisco High at 9 a.m. and there will be a celebration at Orange Park with awards, T-shirts and healthy snacks. School bands and dance troops will also be performing. Participants my register here.
South San Francisco Day at AT&T Park for a San Francisco Giants’ game is Tuesday, May 7. Tickets are $20 and are being sold through SSF High clubs/teams as a fundraiser.
John Murphy may be reached at jmurphy@Prep2Prep.com and followed on Twitter @PrepCatÂ
While a person is exercising, the body must adjust to send extra blood to working muscles. When this adjustment takes place, blood must be redirected from somewhere else in the body. During rest only 15-20% of the cardiac output of the heart goes to the skeletal muscles, but during exercise, that number reverses with the other areas of the body, feeding the muscles nearly 85% of the total output of the heart. Muscles like the kidney, brain, and liver eat up nearly 65% of the total blood flow at rest!
When exercise is light, blood flow to the skin increases to compensate for a change in body temperature. This percentage decreases when exercise gets heavier to send more blood to the muscles.
The heart generally receives around 4% regardless of the body being in exercise. Blood flow to the brain increases slightly, as the brain cannot have a decrease in blood flow over several seconds without fainting.
Because our body has a parallel circulatory system, blood flow can be redistributed where needed. Because of vasodialation, a decrease in radius, and vasoconstriction, an increase in radius, the vessels leading to a particular organ or tissue area change diameter depending on where blood is needed in the body. Blood flow into a capillary bed depends on the vasodialation or vasoconstriction of the arteriole supply. Inside the capillary bed are muscular rings called precapillary sphincters have increase or decrease the diameter of the vessel and control the flow of blood into the bed.
The body has an amazing way of Â keeping itself running, literally!
Did you know the body has its very own natural pacemaker? The sinoatrial node, also called the SA Node, is part of the cardiac system that controls the heart rate. Â It is located in the upper wall of the right atrium and is known as the heart’s natural pacemaker. It is also sometimes called the sinus node.
The SA Node’s job is to send rhythymic electrical impulses through the heart, stimulating the heart to contract and in turn, pump blood. As this impulse passes through the heart muscles, the atria contract.
As the electrical signal is generated, it eventually reaches the atrioventricular node, or the AV Node. The AV Node is a group of cells between the atria and the ventricles. As the electrical signal hits the AV node, the signal is slowed, to delay the ventricle stimulation. This allows the atria to contract fully.
TheÂ autonomic nervous system controls the trigger for the SA node.,Â The autonomic nervous system is the same part of the nervous system that controls blood pressure. The autonomic nervous system can transmit a message quickly to the SA node so it in turn can increase the heart rate to twice normal within only 3 to 5 seconds. This immediate response is extremely important during exercise, because the heart has to increase its speed to keep up with the body’s increased demand for oxygen.
What controls respiration within your body? It’s an interesting question, because respiration involves many parts of the body. The brain must realize that physical activity is taking place and tell the lungs to work harder to bring more oxygen in. The muscles need oxygen to sustain activity, so the blood must pump oxygenated blood throughout the muscles and organs. The brain also has to recognize an increase in body temperature due to activity and keep the body from overheating. Lots to worry about!
Fortunately for us, this process is involuntary, so we don’t have to worry about it at all! Our body will automatically adjust to changes in oxygen demand as we exercise. Here is how.
The medulla oblongata and an area called pons are in charge of our respiratory control center. This center creates a rhythmic breathing pattern sent down our spinal cord to the muscles involved in respiration. Â Chemoreceptors within the medulla respond to changes in the pH concentration of the spinal fluid.Â During exercise, hydrogen ions in the blood increase due to a higher concentration of carbon dioxide, caused by lactic acid production and anaerobic metabolism. This increase in H+ concentration occurs in the cerebral spinal fluid, which increases ventilation and the elimination of carbon dioxide. Chemoreceptors located within the arteries of the heart (aortic and carotid) respond to changes in H+ concentration and carbon dioxide in the blood. The blood concentration is measured in two different places. The carotid artery measures concentration to the brain and head, while the aortic measures concentrations returning to the heart from the body.
The lungs contain Â certain stretch receptors to limit their oxygen intake volume. Other respiratory muscles like the abdomen andÂ diaphragmÂ also contain these receptors. Joints and skeletal muscles contain receptors sensitive to pressure and changes in body positioning.
The body is a well oiled machine that must work together to accomplish Â common goals: Respiration and Ventilation!
Respiration is a very necessary and important function for humans. Breathing and the exchange of gases between the air and blood are vital for survival. To accomplish the task of breathing, one must be able to bring oxygen into the body and exchange oxygen for carbon dioxide at the cellular level to keep red blood cells working efficiently. Let’s discuss the steps of how this happens.
Air must first be brought into the body. This is done through the nostrils. As air passes from the exterior of the body to the lungs it passes through the nasal cavity, the pharnyx, the larynx and into the trachea. At the bottom of the trachea are the bronchi, which branch into the two lungs. As the air goes through the bronchi to the bronchioles, it reaches its final destination, the terminal bronchioles. In the bronchioles, air is warmed, humidified and filtered. In dry and cold climates, air entering the bronchioles is humidified and warmed to prevent any damage to the tender alveoli of the lungs. This also takes place to help maintain normal body temperature where gas exchange takes place.
Once oxygen reaches the terminal bronchioles, air is conducted into the alveoli. The alveoli are the structures where gas exchange takes place, as none has happened to this point. With approximately 300 million alveoli, the surface area for gas exchange spans approximately the size of a tennis court! The respiratory membrane also helps aid in exchange, as it makes up the wall of the capillary.
The lungs are surrounded by a sac called the pleura. This sac has a pressure that is less than the atmospheric pressure outside of the human. For air to be moved in and out of the lungs, muscles outside the lungs must cause thoracic cavity volume to change. When air pressure within the lungs is greater than the pressure outside, air moves out of the lungs. Â When the pressure within the lungs is less than the atmospheric pressure, air moves into the lungs. BetweenÂ inhalationÂ and expiration, the pressure within the lungs and in the atmosphere are the same causing no movement of air.
More on the lungs later this week…
Did you know that the position of your body during exercise can increase or decrease your stroke volume?
For those of you who are wondering what Stroke Volume is, it is the amount of blood pumped from the left ventricle of the heart with each beat, or contraction. Stroke Volume is calculated usingÂ measurements of ventricle volumes. After this is done, one can subtract the volume of the blood in the ventricle at the end of a beat from the volume of blood prior to the beat. (Stroke Volume= End Diastolic Volume-EndÂ SystolicÂ Volume) SV is generally measured from the left ventricle.
The effect of gravity has a great effect on stroke volume. When doing an upright exercise (running, biking with pedals down), blood tends to pool in the legs. This decreases the venous return to the heart, decreasing stroke volume. Stroke Volume can increase by up to 300% in upright exercise positions. Supine positions held in exercise like swimming only increase Stroke Volume by 20-40%.
Why is increased stroke volume important? Gradually over time, aerobic exercise that increases stroke volume tends to decrease your resting heart rate.
Thanks to I2MC for the image.
The field of calorimetry involves calculating the heat involved in physical changes and chemical reactions. The Latin word â€˜calor’ means heat, and the word was created when scientist Joseph Black noted the difference between heat and temperature. Black also classified the two forms of calorimetry, direct and indirect. Letâ€™s explore the difference between the two.
Direct Calorimetry is the process of measuring heat production to determine metabolic rate in living organisms. The kilocalorie is the unit used to measure metabolic rate. 1 Kilocalorie is equivalent to 1,000 calories. To calculate heat, mass is multiplied by temperature change. For example, if 2,000 grams of water increase in temperature by 2o C, 4,000 calories or 4kcal of heat was the amount of heat needed to do so. (2,000 x 2o= 4kcal)
Direct Calorimetry is a very cumbersome process and requires very expensive equipment to measure. A calorimeter is a chamber surrounded by a water jacket. The chamber is air tight, and the heat expelled by a person exercising in the chamber increases the temperature of the water jacket. The amount of heat can be calculated by taking the amount of water multiplied by the increase in temperature in the jacket. Because of the expense involved in getting the appropriate equipment, most laboratories use indirect calorimetry to measure metabolic rate.
Indirect calorimetry involves the measuring of heat that living objects create from producing carbon dioxide and nitrogenous wastes. It also deals with calculating the heat from oxygen consumption. From calculating these figures, we can determine the percentage of carbohydrates and fatty acids being metabolized and the amount of energy being produced.
Many say that indirect calorimetry is the more accurate measurement tool. It gives a precise calculation of heat, because it involves actual oxygen uptake to give the caloric burn rate. Conversely, indirect calorimetry method also has its own flaws. For one, it is does not gauge metabolic rate that is commonly present in anaerobic processes. Its result may also vary bases on the intensity of exercise, its duration, and other essential considerations. A respiratory gas does not give detail on the kind of fuels that are used during testing. And finally, that cellular process is not at all reproduced within the expired air.