Cardiovascular physiology is the study of the circulatory system

Circulatory system

The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...

. More specifically, it addresses the physiology

Physiology

Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...

 of the heart

Heart

The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

 ("cardio") and blood vessel

Blood vessel

The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...

s ("vascular").

These subjects are sometimes addressed separately, under the names cardiac physiology and circulatory physiology.

Although the different aspects of cardiovascular physiology are closely interrelated, the subject is still usually divided into several subtopics.

Heart

See Heart#Physiology for more details

• Cardiac output
  Cardiac output
  Cardiac output is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. CO may be measured in many ways, for example dm3/min...
  
   (= heart rate
  Heart rate
  Heart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
  
   * stroke volume
  Stroke volume
  In cardiovascular physiology, stroke volume is the volume of blood pumped from one ventricle of the heart with each beat. SV is calculated using measurements of ventricle volumes from an echocardiogram and subtracting the volume of the blood in the ventricle at the end of a beat from the volume...
  
  . Can also be calculated with Fick principle
  Fick principle
  Developed by Adolf Eugen Fick , the Fick principle was first devised as a technique for measuring cardiac output. However, its underlying principles may be applied in a variety of clinical situations....
  
  .)
  • Stroke volume
    Stroke volume
    In cardiovascular physiology, stroke volume is the volume of blood pumped from one ventricle of the heart with each beat. SV is calculated using measurements of ventricle volumes from an echocardiogram and subtracting the volume of the blood in the ventricle at the end of a beat from the volume...
    
     (= end-diastolic volume
    End-diastolic volume
    In cardiovascular physiology, end-diastolic volume is the volume of blood in the right and/or left ventricle at end Load or filling in . Because greater EDVs cause greater distention of the ventricle, EDV is often used synonymously with preload, which refers to the length of the sarcomeres in...
    
     - end-systolic volume
    End-systolic volume
    End-systolic volume is the volume of blood in a ventricle at the end of contraction, or systole, and the beginning of filling, or diastole.ESV is the lowest volume of blood in the ventricle at any point in the cardiac cycle....
    
    )
  • Ejection fraction
    Ejection fraction
    In cardiovascular physiology, ejection fraction is the fraction of Blood pumped out of the Right Ventricle of the heart to the Pulmonary Circulation and Left Ventricle of the heart to the Systemic Circulation with each Heart beat or Cardiac cycle...
    
     (= stroke volume / end-diastolic volume)
  • ((Cardiac Output)) is mathematically ` to ((Systole))

• • Inotropic, chronotropic
    Chronotropic
    Chronotropic effects are those that change the heart rate.Chronotropic drugs may change the heart rate by affecting the nerves controlling the heart, or by changing the rhythm produced by the sinoatrial node...
    
    , and dromotropic
    Dromotropic
    Derives from the Greek word "Dromos", meaning running, a course, a race. A dromotropic agent is one which affects the conduction speed in the AV node, and subsequently the rate of electrical impulses in the heart....
    
     states

• • Cardiac input
    Cardiac input
    Cardiac input is the inverse operation of cardiac output .Cardiac output implies ejection fraction.Ejection fraction is an easily understood and inexpensively imaged mathematical model of systole....
    
     (= heart rate
    Heart rate
    Heart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
    
     * suction volume Can be calculated by inverting terms in Fick principle
    Fick principle
    Developed by Adolf Eugen Fick , the Fick principle was first devised as a technique for measuring cardiac output. However, its underlying principles may be applied in a variety of clinical situations....
    
    )
  • Suction volume (= end-systolic volume
    End-systolic volume
    End-systolic volume is the volume of blood in a ventricle at the end of contraction, or systole, and the beginning of filling, or diastole.ESV is the lowest volume of blood in the ventricle at any point in the cardiac cycle....
    
     + end-diastolic volume
    End-diastolic volume
    In cardiovascular physiology, end-diastolic volume is the volume of blood in the right and/or left ventricle at end Load or filling in . Because greater EDVs cause greater distention of the ventricle, EDV is often used synonymously with preload, which refers to the length of the sarcomeres in...
    
    )
  • Injection fraction
    Injection fraction
    Injection fraction, or end diastolic volume divided by end systolic volume of the ventricles or IF=EDV/ESV, is the inverse mathematical operation of the Myocardium derived Ejection Fraction. "Ejection Fraction" is historically and mathematically derived from Cardiac Output first posited by Adolph...
    
     (=suction volume / end-systolic volume)
  • Cardiac input
    Cardiac input
    Cardiac input is the inverse operation of cardiac output .Cardiac output implies ejection fraction.Ejection fraction is an easily understood and inexpensively imaged mathematical model of systole....
    
     is mathematically ` to (Diastole))

• Electrical conduction system of the heart
  Electrical conduction system of the heart
  The normal intrinsic electrical conduction of the heart allows electrical propagation to be transmitted from the Sinoatrial Node through both atria and forward to the Atrioventricular Node. Normal/baseline physiology allows further propagation from the AV node to the ventricle or Purkinje Fibers...
  
  
  • Electrocardiogram
    Electrocardiogram
    Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
    
    
  • Cardiac marker
  • Cardiac action potential
    Cardiac action potential
    In electrocardiography, the cardiac action potential is a specialized action potential in the heart, necessary for the electrical conduction system of the heart....
    
    

• Frank–Starling law of the heart
• Wiggers diagram
  Wiggers diagram
  A Wiggers diagram is a standard diagram used in cardiac physiology.The X axis is used to plot time, while the Y axis contains all of the following on a single grid:* Blood pressure** Aortic pressure** Ventricular pressure** Atrial pressure...
  
  
• Pressure volume diagram
  Pressure volume diagram
  A pressure volume diagram is used to describe corresponding changes in volume and pressure in a system...
  
  

Blood vessels

See Blood vessel#Physiology for more details

• Compliance
• Microcirculation
  Microcirculation
  The microcirculation is a term used to describe the small vessels in the vasculature which are embedded within organs and are responsible for the distribution of blood within tissues; as opposed to larger vessels in the macrocirculation which transport blood to and from the organs...
  
  
• Starling equation
  Starling equation
  The Starling equation is an equation that illustrates the role of hydrostatic and oncotic forces in the movement of fluid across capillary membranes.Capillary fluid movement may occur as a result of three processes:...
  
  
• Fick's law of diffusion
  Fick's law of diffusion
  Fick's laws of diffusion describe diffusion and can be used to solve for the diffusion coefficient, D. They were derived by Adolf Fick in the year 1855.- Fick's first law :...
  
  
• Poiseuille's law
• Skeletal-muscle pump
  Skeletal-muscle pump
  The skeletal-muscle pump is a collection of skeletal muscles that aid the heart in the circulation of blood. It is especially important in increasing venous return to the heart, but may also play a role in arterial blood flow.-Arterial blood pumping:...
  
  

Regulation of blood pressure

• Baroreceptor
  Baroreceptor
  Baroreceptors are sensors located in the blood vessels of several mammals. They are a type of mechanoreceptor that detects the pressure of blood flowing through them, and can send messages to the central nervous system to increase or decrease total peripheral resistance and cardiac output...
  
  
• Baroreflex
  Baroreflex
  The baroreflex or baroreceptor reflex is one of the body's homeostatic mechanisms for maintaining blood pressure. It provides a negative feedback loop in which an elevated blood pressure reflexively causes heart rate to decrease therefore causing blood pressure to decrease; likewise, decreased...
  
  
• Renin-angiotensin system
  Renin-angiotensin system
  The renin-angiotensin system or the renin-angiotensin-aldosterone system is a hormone system that regulates blood pressure and water balance....
  
  
  • Renin
    Renin
    Renin , also known as an angiotensinogenase, is an enzyme that participates in the body's renin-angiotensin system -- also known as the Renin-Angiotensin-Aldosterone Axis -- that mediates extracellular volume , and arterial vasoconstriction...
    
    
  • Angiotensin
    Angiotensin
    Angiotensin, a peptide hormone, causes blood vessels to constrict, and drives blood pressure up. It is part of the renin-angiotensin system, which is a major target for drugs that lower blood pressure. Angiotensin also stimulates the release of aldosterone, another hormone, from the adrenal cortex...
    
    
• Juxtaglomerular apparatus
  Juxtaglomerular apparatus
  The juxtaglomerular apparatus is a microscopic structure in the kidney, which regulates the function of each nephron. The juxtaglomerular apparatus is named for its proximity to the glomerulus: it is found between the vascular pole of the renal corpuscle and the returning distal convoluted tubule...
  
  
• Aortic body
  Aortic body
  In the human heart, the aortic body is one of several small clusters of chemoreceptors, baroreceptors, and supporting cells located along the aortic arch.-Function:...
  
   and carotid body
  Carotid body
  The carotid body is a small cluster of chemoreceptors and supporting cells located near the fork of the carotid artery ....
  
  
• Autoregulation
  Autoregulation
  Autoregulation is a process within many biological systems, resulting from some internal adaptive mechanism that works to adjust the systems response to stimuli. While most systems of the body show some degree of autoregulation, it is most clearly observed in the kidney, the heart, and the brain...
  
  

Hemodynamics

Under most circumstances, the body attempts to maintain a steady mean arterial pressure

Mean arterial pressure

The mean arterial pressure is a term used in medicine to describe an average blood pressure in an individual. It is defined as the average arterial pressure during a single cardiac cycle.-Calculation:...

.

When there is a major and immediate decrease (such as that due to hemorrhage or standing up

Orthostatic hypotension

Orthostatic hypotension, also known as postural hypotension, orthostasis, and colloquially as head rush or dizzy spell, is a form of hypotension in which a person's blood pressure suddenly falls when the person stands up or stretches. The decrease is typically greater than 20/10 mm Hg, and may be...

), the body can increase the following:

• Heart rate
  Heart rate
  Heart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
  
  
• Total peripheral resistance
  Total peripheral resistance
  Vasculature throughout the entire body can be thought of as two separate circuits - one is the systemic circulation, while the other is the pulmonary circulation. Total peripheral resistance is the sum of the resistance of all peripheral vasculature in the systemic circulation...
  
   (primarily due to vasoconstriction of arteries)
• Inotropic state
  Inotrope
  An inotrope is an agent that alters the force or energy of muscular contractions. Negatively inotropic agents weaken the force of muscular contractions...
  
  

In turn, this can have a significant impact upon several other variables:

• Stroke volume
  Stroke volume
  In cardiovascular physiology, stroke volume is the volume of blood pumped from one ventricle of the heart with each beat. SV is calculated using measurements of ventricle volumes from an echocardiogram and subtracting the volume of the blood in the ventricle at the end of a beat from the volume...
  
  
• Cardiac output
  Cardiac output
  Cardiac output is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. CO may be measured in many ways, for example dm3/min...
  
  
• Pressure
  • Pulse pressure
    Pulse pressure
    Pulse Pressure is most easily defined as being the amount of pressure required to create the feeling of a pulse. Measured in millimeters of mercury , the pressure difference between the systolic and diastolic pressures give you the amount of pressure change to create the pulse, which is the pulse...
    
     (systolic pressure
    Systole (medicine)
    Systole is the contraction of the heart. Used alone, it usually means the contraction of the left ventricle.In all mammals, the heart has 4 chambers. The left and right ventricles pump together. The atria and ventricles pump in sequence...
    
     - diastolic pressure
    Diastole
    Diastole is the period of time when the heart fills with blood after systole . Ventricular diastole is the period during which the ventricles are relaxing, while atrial diastole is the period during which the atria are relaxing...
    
    )
  • Mean arterial pressure
    Mean arterial pressure
    The mean arterial pressure is a term used in medicine to describe an average blood pressure in an individual. It is defined as the average arterial pressure during a single cardiac cycle.-Calculation:...
    
     (usually approximated with diastolic pressure + 1/3 pulse pressure)
  • Central venous pressure
    Central venous pressure
    Central venous pressure describes the pressure of blood in the thoracic vena cava, near the right atrium of the heart...
    
    

Regional circulation

Name of circulation

% of cardiac output Cardiac output Cardiac output is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. CO may be measured in many ways, for example dm3/min...

Autoregulation Autoregulation Autoregulation is a process within many biological systems, resulting from some internal adaptive mechanism that works to adjust the systems response to stimuli. While most systems of the body show some degree of autoregulation, it is most clearly observed in the kidney, the heart, and the brain...

Perfusion Perfusion In physiology, perfusion is the process of nutritive delivery of arterial blood to a capillary bed in the biological tissue. The word is derived from the French verb "perfuser" meaning to "pour over or through."...

Comments >- | pulmonary circulation Pulmonary circulation Pulmonary circulation is the half portion of the cardiovascular system which carries Oxygen-depleted Blood away from the heart, to the Lungs, and returns oxygenated blood back to the heart. Encyclopedic description and discovery of the pulmonary circulation is widely attributed to Doctor Ibn...

100% (deoxygenated)

Vasoconstriction Vasoconstriction Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...  in response to hypoxia Hypoxia (medical) Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise... >- | cerebral circulation Cerebral circulation Cerebral circulation refers to the movement of blood through the network of blood vessels supplying the brain. The arteries deliver oxygenated blood, glucose and other nutrients to the brain and the veins carry deoxygenated blood back to the heart, removing carbon dioxide, lactic acid, and other...

15%

high

under-perfused

anaerobic respiration Anaerobic respiration Anaerobic respiration is a form of respiration using electron acceptors other than oxygen. Although oxygen is not used as the final electron acceptor, the process still uses a respiratory electron transport chain; it is respiration without oxygen... >- | coronary circulation Coronary circulation Coronary circulation is the circulation of blood in the blood vessels of the heart muscle . The vessels that deliver oxygen-rich blood to the myocardium are known as coronary arteries...

5%

high

under-perfused

anaerobic respiration Anaerobic respiration Anaerobic respiration is a form of respiration using electron acceptors other than oxygen. Although oxygen is not used as the final electron acceptor, the process still uses a respiratory electron transport chain; it is respiration without oxygen... . Blood flow through the left coronary artery Left coronary artery The left coronary artery, abbreviated LCA and also known as the left main coronary artery , arises from the aorta above the left cusp of the aortic valve.-Branching:...  is at a maximum during diastole Diastole Diastole is the period of time when the heart fills with blood after systole . Ventricular diastole is the period during which the ventricles are relaxing, while atrial diastole is the period during which the atria are relaxing...  (in contrast to the rest of systemic circulation Systemic circulation Systemic circulation is the part of the cardiovascular system which carries oxygenated blood away from the heart to the body, and returns deoxygenated blood back to the heart. This physiologic theory of circulation was first described by William Harvey... , which has a maximum blood flow during systole Systole (medicine) Systole is the contraction of the heart. Used alone, it usually means the contraction of the left ventricle.In all mammals, the heart has 4 chambers. The left and right ventricles pump together. The atria and ventricles pump in sequence... .) >- | splanchnic Splanchnic Splanchnic, from a Greek word spēn, meaning organ, usually used to describe visceral organs.More specifically, it can also refer to:* An adjective describing the intestines* Splanchnic nerves* Splanchnic mesoderm...  circulation

15%

low

digestion Digestion Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones.... . >- | hepatic circulation

15%

portal venous system Portal venous system In human anatomy, the hepatic portal system is the system of veins comprising the hepatic portal vein and its tributaries. It is also called the portal venous system, although it is not the only example of a portal venous system, and splanchnic veins, which is not synonymous with hepatic portal... , so oncotic pressure Oncotic pressure Oncotic pressure, or colloid osmotic pressure, is a form of osmotic pressure exerted by proteins in blood plasma that usually tends to pull water into the circulatory system.Throughout the body, dissolved compounds have an osmotic pressure...  is very low >- | renal circulation Renal circulation The renal circulation receives around 20% of the cardiac output. It branches from the abdominal aorta and returns blood to the ascending vena cava. It is the blood supply to the kidney, and contains many specialized blood vessels.-Circulation:...

25%

high

over-perfused

>- | skeletal muscular circulation

17%

>- | cutaneous circulation

2%

over-perfused

Crucial in thermoregulation Thermoregulation Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different... . Significant ability to use anaerobic respiration Anaerobic respiration Anaerobic respiration is a form of respiration using electron acceptors other than oxygen. Although oxygen is not used as the final electron acceptor, the process still uses a respiratory electron transport chain; it is respiration without oxygen...

External links

• Cardiovascular Physiology Concepts - Comprehensive explanation of basic cardiovascular concepts, based on a textbook of the same name.