Name: circulatory system: blood flow and pressure
Uploaded: 2019-01-31T09:26:31.000Z
Duration: 5 min 33 s
Channel: JoVE

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Biology

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From Molecules to Organisms: Structures and Processes

BIO1.LS1.8

Physiology of the Circulatory System

Physiology is a branch of biology that describes how organisms function and adapt to different environments. One of the most important organ systems that define an organism&#39;s physiology is the circulatory system, which transports blood, nutrients, oxygen, and hormones throughout the body. In humans, a measure of the circulatory system&#39;s function can be obtained by taking the blood pressure. The term blood pressure describes the lateral pressure produced by blood upon vessel walls. 
One of the most important applications of blood pressure measurement is checking for increased blood pressure, a condition termed hypertension. One in every three adults in the United States suffers from hypertension, and it is one of the leading causes of cardiovascular disease. The equipment needed for a traditional indirect measurement of blood pressure includes a stethoscope and a sphygmomanometer. The sphygmomanometer consists of a blood pressure cuff containing a distensible bladder, and a rubber bulb with an adjustable valve which, when closed, helps in cuff inflation, and when open releases the built-up pressure. It also consists of tubing connecting the cuff to the bulb and to the manometer which displays the cuff&#39;s pressure in millimeters of mercury. In order to record the blood pressure reading the examiner wraps the cuff around the brachial artery, places a stethoscope over this artery, inflates the cuff above the expected systolic pressure, and then deflate it while auscultating and observing the manometer simultaneously. Initially, when the cuff is fully inflated, the artery is squeezed, and the blood flow is halted. Thus, there is no sound upon auscultation. Upon deflation, the first appearance of the Korotkoff sounds signifies the systolic pressure, which is audible due to the turbulent flow in the partially squeezed artery. Further deflation causes a continual decreasing cuff pressure, and the Korotkoff sounds remain audible throughout, up until the point where the cuff pressure is below the minimal arterial pressure. This reading denotes the diastolic pressure. The fraction of systolic over diastolic is recorded as the final blood pressure reading. 
Another important indicator of human physiology is the respiration rate, the number of breaths per minute. The air we breathe in travels through our trachea, into our lungs through the bronchi. Inside the lungs it passes through the bronchioles to ultimately enter the specialized air sacs called alveoli. The alveoli are surrounded by blood capillaries which allow diffusion of inhaled oxygen into our bloodstream, and facilitate excretion of carbon dioxide, thus maintaining our system&#39;s homeostasis. For mammals like humans maintaining homeostasis includes preserving a relatively constant body temperature independent of the surrounding environmental temperature. This property makes us endotherms. Therefore, our metabolic rate and respiration rate stay relatively constant. On the contrary, nearly all fish, including goldfish, have an internal body temperature that almost matches the temperature of the environment surrounding them. Such organisms are called ectotherms. Since they don&#39;t actively maintain a constant internal temperature their metabolic and respiration rate changes to compensate for variation in surrounding environmental temperature. The respiration rate in fishes can be measured by counting the gill beats, the rise and fall of the operculum, or gill cover, per minute. There is one more factor that affects the respiration rate of aquatic organisms. Note, that a fish breathes in the dissolved oxygen present in its environment. And the amount of available dissolved oxygen in the water is dependent on the water&#39;s temperature. It decreases with increased temperature which also, in turn, affects the respiration rate. 
In this lab you will examine the human circulatory system by measuring blood pressure under different conditions, and then study the effects of temperature on respiration using fish.

physiology of the circulatory system

<h4>Homeostasis</h4>
Conditions in the external environment of an organism can change rapidly and drastically. To survive, organisms must maintain a fairly constant internal environment, which involves continuous regulation of temperature, pH, and other factors. This balanced state is known as homeostasis, which describes the processes by which organisms maintain their optimal internal conditions. To maintain homeostasis, organisms have developed structures with distinct functions. Physiology is the study of the normal functions and mechanisms of the different systems in the body. For example, if the external environment becomes warmer than the ideal internal temperature, the organism will activate physiological processes that will keep the body from heating to the external temperature. Humans and many other animals attain homeostasis through distinct physiological processes in specialized cells.
<h4>Organ Systems in Humans</h4>
One or more cell types with supporting functions form tissues, which in turn make up organs with specialized bodily functions. Organ systems consist of two or more organs that work together to provide a common function. The vertebrate physiological system comprises 11 major organ systems. While all of the organ systems are interconnected, they do function somewhat independently of one another.
The body is covered by the integumentary system, which consists of skin, hair, nails, sensory receptors, and various glands. Besides protecting the internal structures, integumentary organs sense many features of the external environment and helps regulate body temperature. Internally, organs are protected and supported by the skeletal system, which comprises bones, cartilage, tendons, and ligaments. The skeletal system also provides attachment for the muscles that make up the muscular system. Muscles can move the body by moving the skeleton or contract to move substances through hollow organs. The nervous system consists of the brain, spinal cord and peripheral nerves. It interprets sensory stimuli and directs behavior of the organism to control physiological processes together with other systems. The endocrine system is made up of hormone-secreting glands and organs including the pituitary, thyroid, pancreas, ovaries and testes. It regulates growth, metabolism and reproduction together with other systems. The respiratory system controls gas exchange to supply the body with oxygen as it removes carbon dioxide in the lungs after air passage through the nasal cavity, pharynx, larynx, trachea and bronchus. The digestive system processes and breaks down food which is taken in through the oral cavity and esophagus, and then moved through the stomach, small and large intestines before excretion through the rectum and anus. Nutrients are absorbed in the small and large intestines and then processed by the liver. The urinary system concentrates and eliminates nitrogenous waste via the kidney, bladder, and urethra. It also rids the body of excess water. The cardiovascular or circulatory system consists of the heart, blood vessels and blood, and delivers oxygen and nutrients to the tissues, while removing carbon dioxide and waste products throughout the body. The lymphatic system maintains the body&#8217;s immune response via white blood cells or lymphocytes (housed in red bone marrow), thymus, lymphatic vessels, thoracic duct, spleen, and lymph nodes. Finally, the reproductive system primes reproductive cells of organisms. In males, testes and the penis comprise the reproductive system while in females the uterus, ovaries, and vagina comprise the reproductive system.
<h4>Physiology of the Circulatory System</h4>
The physiology of single-celled organisms and basal multicellular animals, such as sponges, is often simple. For example, the small size and large surface to volume ratio of microorganisms allows them to attain regulation by diffusion across the cell membrane. Similarly, seawater circulates through the pores of sponges, carrying nutrients and waste products to and from its cells. More complex animals have developed circulatory systems to move blood throughout the body to transport nutrients, waste products, hormones and other molecules, while the respiratory systems allow gas exchange between the circulatory system and the external environment. 
The circulatory system in animals can be open or closed. Open circulatory systems are typically present in many invertebrates and consist of one or more simple hearts, a vessel network and interconnected spaces that directly bathe internal organs in a fluid that allows exchange of materials. Vertebrates have closed circulatory systems, in which blood is confined inside a closed vessel system which branching extensively into the tissues to ensure material exchange. This closed vessel system is connected to a heart with veins carrying blood from tissues towards the heart and arteries carrying blood from the heart to the rest of the body. Four-chambered hearts, such as in humans, are associated with two loops of vessels. In humans, oxygen-depleted blood from organs enter the heart through the right atrium, which contracts to push blood to the right ventricle, which in turn sends blood to the lungs. Following gas exchange in the lungs, oxygen-rich blood returns to the left atrium and is later pushed into the left ventricle. This final chamber is more muscular than the others and with a strong contraction, is able to pump the blood to the rest of the body.
Closed circulatory systems allow rapid circulation of blood, which in turn enables fast and efficient transport of substances throughout the body as well as higher blood pressure than in open systems. The blood pressure is generated by the contraction of the heart ventricles as blood is forced into the arteries. As the ventricles of the heart relax, the blood pressure decreases.
<h4>Blood Pressure</h4>
In humans, the functioning of the circulatory system can be assessed by measuring the blood pressure and the corresponding heart rate in an individual. Blood pressure is measured in millimeters of mercury (mmHg), which is the height in millimeters that mercury in a column is raised to due to the pressure exerted on it. Heart rate is measured as beats per minute. Because of the heart&#8217;s contraction and relaxation movements, blood pressure readings consist of two numbers&#8212;systolic and diastolic. Systolic pressure is measured during contractions of the ventricles and diastolic pressure is the minimum pressure in the arteries during rest between contractions. Generally, systolic pressures of 90-120 mmHg and diastolic pressures of 60-80 mmHg are considered healthy. When it comes to heart rate, 60-100 beats per minute is considered healthy for adults. Athletes generally have lower heart rates as cardiovascular exercises elevate the heart rate and condition the heart to pump more efficiently, which eventually reduces the resting heart rate1.
Elevated blood pressure levels for extended periods or hypertension can damage blood vessels and has been linked to heart attack and stroke2. Researchers discovered that the cardiovascular effects of systolic and diastolic pressure are different, such that the rates of cardiovascular events are strongly associated with systolic pressure. Therefore, the number of patients with systolic hypertension who suffer from cardiovascular events is higher than the number of patients with diastolic hypertension3. Genetic factors, as well as lifestyle and environmental factors can cause hypertension and cardiovascular disease. For instance, consumption of high amounts salt causes retention of excess water in the body, elevating blood pressure and straining blood vessels. Any insults of blood vessels make them prone to injuries, which provides surfaces for plaque buildup, eventually stiffening blood vessels and reducing the efficiency of blood flow.
Blood pressure measurements
Sphygmomanometers are used to measure blood pressure. They are composed of an inflatable cuff which is connected to a pump (manual or automatic) and a pressure gauge. The most efficient way to use a sphygmomanometer is on the brachial artery on the upper arm, which is in level with the heart. Sphygmomanometers are used in conjunction with a stethoscope, which is an acoustic medical device used to listen to internal sounds via a metal disc, or resonator. The stethoscope is held just underneath the sphygmomanometer, just above the inside of the individual&#39;s elbow to measure the sounds of the systolic and diastolic blood pressure. The cuff is inflated to 200 mmHg stopping blood flow by pinching the blood vessels and is a safe amount of pressure to be applied to the arm. As the cuff deflates, the blood vessels begin to open, and blood is allowed to flow through again. The systolic blood pressure is signified by the first noise heard and the diastolic pressure is determined by the last noise heard. These noises are called Korotkoff sounds, that are the sound of blood being forcibly pushed through vessels by the heart4.
<h4>Respiratory System</h4>
The circulatory system works closely with the respiratory system to provide oxygen to tissues while removing carbon dioxide. Different organisms have developed distinct respiratory structures for gas exchange. For instance, many aquatic animals exchange gases through gills. Gill movements are easily observed and can be used to calculate the respiration rate of aquatic organisms by counting the number of times the organism moves its gill cover or operculum. Respiration rate may change with temperature because oxygen molecules are transported at different rates depending on how warm or cool an environment is. In an aquatic environment, the amount of available dissolved oxygen in the water decreases with increased temperature. The decreased oxygen has effects on the respiration rate of aquatic organisms, given their ability to diffuse oxygen throughout their bodies. On the other hand, terrestrial animals have internal respiratory structures, such as lungs. In humans, breathing involves inhalation by contracting the diaphragm to pull in air. When the diaphragm relaxes, the air is passively released from the lungs.
Smoking is the leading cause of lung cancer, responsible for 80-90% of lung cancer deaths. Every year, more than 120,000 Americans die of smoking-associated lung cancer and represent a large portion of preventable deaths5. Taken together, lifestyle contributes to health of both circulatory and respiratory systems and a significant amount of deaths can be prevented by lifestyle changes.
<h4>References</h4>
<ol class="references">
	<li>Wilson, MG, Ellison, GM and Cable, NT. Basic science behind the cardiovascular benefits of exercise. Br J Sports Med . 2016, 50(93-99).</li>
	<li>Psaty, BM, et al. Association between blood pressure level and the risk of myocardial infarction, stroke, and total mortality: the cardiovascular health study. Arch Intern Med. 2001 , Vol. 161, 9 (1183-92).</li>
	<li>Kannel, WB. Elevated systolic blood pressure as a cardiovascular risk factor. Am. J. Cardiol. 2000, Vol. 85, 2 (251-5).</li>
	<li>Perloff, D, et al. Human blood pressure determination by sphygmomanometry. Circulation. 1993, Vol. 88, 5 (2460-70).</li>
	<li>U.S. Department of Health and Human Services. . The Health Consequences of Smoking: A Report of the Surgeon General. 2004.</li>
</ol>

Homeostasis
Conditions in the external environment of an organism can change rapidly and drastically. To survive, organisms must maintain a fairly ...

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circulatory system: blood flow and pressure

The circulatory system moves blood, oxygen, nutrients, and wastes through the body to support homeostasis. Homeostasis is the stable internal balance that organisms must maintain even when the outside environment changes. Physiology is the study of how body systems work, and the circulatory system is one of the key systems that helps keep internal conditions steady.

Body systems are built from cells, tissues, organs, and organ systems. Humans have 11 major organ systems, and they work together even though each system has its own main job. The integumentary system protects the body and helps control temperature. The skeletal system supports organs and gives muscles a place to attach. The muscular system moves the body and can also move substances through hollow organs. The nervous system controls responses to stimuli. The endocrine system uses hormones to regulate growth, metabolism, and reproduction. The respiratory system exchanges gases in the lungs. The digestive system breaks down food and absorbs nutrients. The urinary system removes nitrogenous wastes and extra water. The lymphatic system helps immune defense. The reproductive system produces reproductive cells.

In simple organisms, transport can happen by diffusion because of their small size and large surface area to volume ratio. Sponges also rely on water flow through their pores to carry nutrients and wastes. More complex animals need circulatory systems to move materials farther and faster. These systems transport nutrients, waste products, hormones, and other molecules, while the respiratory system supports gas exchange with the outside environment.

Animal circulatory systems can be open or closed. Open circulatory systems are common in many invertebrates. They use one or more simple hearts, a vessel network, and open spaces that bathe organs in fluid for exchange. Vertebrates have closed circulatory systems, where blood stays inside vessels that branch through tissues. In this system, veins carry blood toward the heart, and arteries carry blood away from the heart.

Humans have a four-chambered heart with two circulation loops. Oxygen-poor blood from the body enters the right atrium, moves to the right ventricle, and is sent to the lungs. After gas exchange, oxygen-rich blood returns to the left atrium and then moves to the left ventricle. The left ventricle has a thicker muscle wall because it must pump blood to the rest of the body. Closed circulatory systems move blood quickly and efficiently and produce higher blood pressure than open systems.

Blood pressure and heart rate are used to measure how well the circulatory system is working. Blood pressure is measured in millimeters of mercury, or mmHg. Heart rate is measured in beats per minute. Blood pressure has two numbers. Systolic pressure is the pressure during ventricular contraction. Diastolic pressure is the lowest arterial pressure between contractions. Healthy adult values are usually about 90-120 mmHg for systolic pressure and 60-80 mmHg for diastolic pressure. A healthy adult heart rate is usually 60-100 beats per minute, and athletes often have lower resting heart rates because exercise makes the heart pump more efficiently.

High blood pressure, or hypertension, can damage blood vessels and is linked to heart attack and stroke. The transcript notes that systolic pressure is strongly associated with cardiovascular events, and systolic hypertension is more closely linked to those events than diastolic hypertension. Hypertension can result from genetic, lifestyle, and environmental factors. For example, eating a lot of salt can cause the body to retain extra water. That raises blood pressure and strains blood vessels. Injured vessel walls can also encourage plaque buildup, which can stiffen vessels and reduce blood flow.

Blood pressure is often measured with a sphygmomanometer and a stethoscope. A sphygmomanometer uses an inflatable cuff, a pump, and a pressure gauge. It is usually placed on the brachial artery in the upper arm, level with the heart. The cuff is inflated to 200 mmHg, which briefly stops blood flow and is safe for the arm. As the cuff deflates, blood starts flowing again. The first sound heard is the systolic pressure, and the last sound heard is the diastolic pressure. These sounds are called Korotkoff sounds, and they come from blood being forced through the vessels.

The circulatory system also works closely with the respiratory system to supply oxygen and remove carbon dioxide. Many aquatic animals use gills for gas exchange, and their respiration rate can be estimated by counting operculum movements. Respiration rate can change with temperature because oxygen moves differently in warm or cool environments. In water, dissolved oxygen decreases as temperature rises, which affects aquatic organisms that rely on diffusion. Terrestrial animals use internal structures such as lungs. In humans, inhalation happens when the diaphragm contracts and pulls air in, and exhalation happens when the diaphragm relaxes. Smoking is the leading cause of lung cancer and accounts for 80-90% of lung cancer deaths. The transcript also notes that more than 120,000 Americans die each year from smoking-associated lung cancer, showing how lifestyle choices can affect both circulatory and respiratory health.

Circulatory System: Blood Flow and Pressure

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scientific method

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The circulatory system moves blood, oxygen, nutrients, and wastes through the body to support homeostasis. Homeostasis is the stable internal balance that organisms must maintain even when the outside environment changes. Physiology is the study of how body systems work, and the circulatory system is one of the key systems that helps keep internal conditions steady. Body systems are built from cells, tissues, organs, and organ systems. Humans have 11 major organ systems, and they work together...

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Explore how the circulatory system moves blood, how blood pressure is measured, and how it works with the respiratory system to support homeostasis.

Circulatory System: Blood Flow and Pressure | JoVE K12

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BIO1.LS1.6

Circulatory System: Blood Flow and Pressure

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