Anatomy of the Human Heart: Difference between revisions

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== Introduction  ==
== Introduction  ==
The heart is a muscular pump that serves two functions; to collect oxygen-poor blood from the tissues of the body and pump this blood to the lungs to pick up oxygen and release carbon dioxide and to collect oxygen-rich blood from the lungs and pump this blood to all of the tissues of the body.
[[File:The Heart surface view.jpg|right|frameless|499x499px]]
The heart is a muscular organ that serves to collect deoxygenated [[Blood Physiology|blood]] from all parts of the body, carries it to the [[Lung Anatomy|lung]]<nowiki/>s to be oxygenated and release carbon dioxide. Then, it transports the oxygenated [[blood]] from the lungs and distributes it to all the body parts<ref name=":2">Kenny, WL,Wilmore, JH, Costill, DL. Cardiovascular System and its Control.  In Physiology of Sport and Exercise, 5rdedn. Human Kinetics, 2011. 140-150.</ref>
* The heart pumps around 7,200 litres of blood in a day throughout the body<ref>[https://www.inovaheart.org/upload/docs/Healthcare%20Services/Heart%20and%20Vascular/fast-facts-about-the-heart.pdf Inovqheart Heart Available from: https://www.inovaheart.org/upload/docs/Healthcare%20Services/Heart%20and%20Vascular/fast-facts-about-the-heart.pdf]</ref>.
* The heart is situated at the centre of the chest and points slightly towards the left.
* On average, the heart beats about 100,000 times a day, i.e., around 3 billion beats in a lifetime.
* An adult heart beats about 60 to 80 times per minute, and newborn babies heart beats faster than an adult which is about 70 to 190 beats per minute.


It is important to note that, the blood pumped by the heart also circulates many other important substances such as:


1.     Nutrients from digestion are collected from the small intestine and pumped through the circulatory system to be delivered to all cells of the body.
== Anatomy  ==
 
[[File:Heart location.jpg|right|frameless]]
2.      Hormones are produced from one type of tissues and distributed to all cells of the body. The circulatory system carries waste materials (salts, nitrogenous wastes, and excess water) from cells to the kidneys, where they are extracted and passed to the bladder.  
The heart is a conical hollow muscular organ situated in the middle mediastinum and is enclosed within the pericardium. It is positioned posteriorly to the body of the sternum with one-third situated on the right and two-thirds on the left of the midline. The heart measures 12 x 8.5 x 6 cm and weighs ~310 g (males) and ~255 g (females). It pumps blood to various parts of the body to meet their nutritive requirements. The Greek name for the heart is cardia from which we have the adjective cardia. <ref>Chaurasia BD. [https://www.pdfdrive.com/bd-chaurasia-books.html Human Anatomy Regional and Applied Dissection and Clinical. Vol 1]. CBS Publishers and Distributors Pvt Ltd, 2010
 
3.     The pumping of interstitial fluid from the blood into the extracellular space is an important function of the heart. Excess interstitial fluid is then returned to the circulatory system via the lymphatic system.


== Anatomy  ==
</ref>
The general shape and orientation of the heart are that of a pyramid that has fallen over and is resting on one of its sides. Placed in the thoracic cavity, the apex of this pyramid projects forward, downward, and to the left, whereas the base is opposite the apex and faces in a posterior direction.


The average adult’s heart is about 5.5 inches (14 centimeters) long and 3.5 inches (9 centimeters) wide, or approximately the size of one’s fist and also varies with body size. In an infant, the heart is about a thirtieth of total body weight. In an average adult, the heart is about one three-hundredth of total body weight; this equals about 11 ounces (310 grams) in males and 8 ounces (225 grams) in females.
Relations


=== Location of the Heart  ===
* Anteriorly: the body of the sternum, and adjoining costal cartilages; left lung, and pleura (apex)
The heart is roughly in a plane that runs from the right shoulder to the left nipple. It lies in the protective thorax, posterior to the sternum and costal cartilages, and rests on the superior surface of the diaphragm.  The heart is located between the two lungs in the space referred to as the ''mediastinum''("that which stands in the middle"). The human heart assumes an oblique position in the thorax, one-third of the heart is located on the right side, while two thirds is located on the left side of midline. The base is located below the third rib as it approaches the sternum (note that the sternal angle occurs at the level of the second rib). The base is directed superiorly to the right of midline and posterior. The pointed apex projects to the left of midline and anterior. Thus, the heartbeat can be most easily palpated at the left fifth intercostal space, 8-9 cm from the midsternal line (just inferior to the left nipple).
* Posteriorly: oesophagus, descending thoracic aorta, azygos, hemiazygos veins,  and thoracic duct
* Superficially : bifurcation of the main pulmonary trunk
* Inferiorly: diaphragm
* Laterally: lungs, pleura<ref name=":6">Radiopedia Heart Available: https://radiopaedia.org/articles/heart?lang=gb (accessed 17.6.2021)</ref>


===  Layers of the Heart Walls  ===
===  Layers of the Heart Walls  ===
[[File:Heart layers.jpg|right|frameless|399x399px]]
The heart wall consists of three layers enclosed in the pericardium<ref name=":2" /><ref name=":3">Malouf, JF, Edwards, WD, Tajil, AJ, Seward, JB. Functional anatomy of the heart. In: Fuster, F, Alexander, RW, O’Rourke, RA editors. Hurst’s: The Heart. 10th edn. McGraw-Hill Inc., 2001. p19–62. </ref><ref name=":5">Drake, RL, Vogl, W, Mitchell, AW, Gray, H. Gray's anatomy for Students 2nd ed. 
Philadelphia : Churchill Livingstone/Elsevier, 2010.
</ref>:
# Epicardium - the outer layer of the wall of the heart and is formed by the visceral layer of the serous pericardium.
# Myocardium - the muscular middle layer of the wall of the heart and has excitable tissue and the conducting system.
# Endocardium .<ref name=":6" />
* A middle concentric layer
* A subendocardial layer.
The rest of the heart is composed mainly of the subepicardial and subendocardial layers. 


=== Chambers of the Heart ===
=== Structure and Function ===
[[File:Human-heart-chambers.jpg|right|frameless|399x399px]]
The heart is subdivided by septa into right and left halves, and a constriction subdivides each half of the organ into two cavities, the upper cavity being called the atrium, the lower the ventricle. The heart, therefore, consists of four chambers:


=== Heart Valves  ===
* right atrium
* left atrium
* right ventricle
* left ventricle<ref name=":6" />.


=== Blood Supply  ===


=== Nerve Supply  ===
It is best to remember the four chambers and four valves in order of the series that blood travels through the heart:
The sympathetic and parasympathetic autonomic nervous supplies to the heart form the cardiac plexus which is located close to the arch of the aorta. The fibres from the cardiac plexus accompany the coronary arteries and reach the heart, with most of them terminating at the SA node, AV node and a much less dense supply to the atrial and ventricular myocardium [11].


In general,the parasympathetic vagal fibres are inhibitory and reduce the heart rate and stroke volume. The sympatheticnerves act as accelatory nerves increasing both the heart rate and stroke volume [11]. The afferent nerves run
* Venous blood returning from the body drains into the right atrium via the [[Vena Cava|SVC, IVC]] and coronary sinus
* The right atrium pumps blood through the tricuspid valve into the right ventricle
* The right ventricle pumps blood through the pulmonary semilunar valve into the pulmonary trunk to be oxygenated in the lungs
* Blood returning from the lungs drains into the left atrium via the four pulmonary veins
* The left atrium pumps blood through the bicuspid (mitral) valve into the left ventricle
* The left ventricle pumps blood through the aortic semilunar valve into the ascending [[aorta]] to supply the body.<ref name=":6" />


along sympathetic pathways via both cardiac accelerator nerves and thoracic splanchnic nerves to reach the intermediolateral horn of T1–T4 of the spinal cord [11].
=== Heart Valves  ===
 
[[File:Heart Valves.jpg|right|frameless|399x399px]]
The noradrenergic or the sympathetic nervous system is mainly involved with increasing the heart rate (chronotropy),
The valves of the heart maintain unidirectional flow of the blood and prevent its regurgitation in the opposite direction. There are two pairs of valves in the heart, a pair of atrioventricular valves and a pair of semilunar valves. Apart, it has four valves. All four valves of the heart have a singular purpose: allowing forward flow of blood but preventing backward flow.<ref name=":0">Rehman I, Rehman A. Anatomy, Thorax, Heart. [Updated 2020 Dec 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan Available:https://www.ncbi.nlm.nih.gov/books/NBK470256/ (accessed 17.6.2021)</ref> The outflow of each chamber is guarded by a heart valve:
 
contractility (ionotropy) and the speed of conduction (dromotropy) in the cardiac muscle fibres and the conduction tissue; and the transmitter involved is mainly nor-epinephrine [6]. The SA node receives most
 
of it nerve fibres from the right-sided thoracic sympathetic
 
ganglia and the right vagus [8]. The AV nodes
 
and ventricles receive their nerve supply form the leftsided
 
thoracic sympathetic ganglia and the left vagus,
 
which is mainly because SA node develops from the
 
structures on the right side of the embryo and the AV
 
node develops from the structures on the left side of the
 
embryo [8].


The sympathetic effects are mediated mainly by the
Atrioventricular valves between the atria and ventricles


adrenergic receptors, which includes β-1 and β-2 adrenergic
# tricuspid valve (R side of the heart)
# mitral valve/bicuspid valve (left side of the heart)


receptors [2, 11]. β-1 receptors are found mainly
Semilunar valves which are located in the outflow tracts of the ventricles


in the SA node and AV node, and the ventricular myocardium
# aortic valve (L side heart)
# pulmonary valve (R side heart)<ref name=":6" />
See also [[Cardiac Valve Defects]]


acts via activation of adenylate cyclase and an
== Blood Supply ==
[[File:Overview of the coronary arteries and cardiac veins - Kenhub.png|alt=Overview of the coronary arteries and cardiac veins - anterior and posterior views|right|frameless|600x600px|Overview of the coronary arteries and cardiac veins - anterior and posterior views]]
The heart is supplied by two coronary arteries:


increase in cAMP (cyclic adenosine monophosphate)
# Left main coronary artery carries 80% of the flow to the heart muscle. It is a short artery that divides into two branches


concentration in the cell to mediate the above mentioned
* Left  anterior descending artery that supplies anterior two-thirds of the inter-ventricular septum and adjoining part of the left ventricular anterior wall
* Circumflex coronary artery that supplies blood to the lateral and posterior portions of the left ventricle.


sympathetic effects [2, 11]. β-2 receptors are
2. Right coronary artery: branches supply the right ventricle, right atrium, and left ventricle's inferior wall.


mainly found in the vascular smooth muscles in addition
Coronary arteries and veins course over the surface of the heart. Most coronary veins coalesce into the coronary sinus that runs in the left posterior atrioventricular groove and opens into the right atrium. Other small veins, called thebesian veins, open directly into all four chambers of the heart.<ref name=":0" />


to the bronchial smooth muscle and wall of the GI
Image: Overview of the coronary arteries and cardiac veins - anterior and posterior views<ref >Overview of the coronary arteries and cardiac veins - anterior and posterior views image - © Kenhub https://www.kenhub.com/en/library/anatomy/heart</ref>


tract and the bladder. The mechanism of action is same
See also [[Coronary Artery Disease (CAD)|Coronary Artery Disease]]


as that of β-1 receptors, i.e., increase in cAMP levels but
== Venous drainage and Lymphatics ==
Venous drainage is via the variable coronary veins and the coronary sinus<ref name=":6" />.  


they cause relaxation of the vascular smooth muscle and
The [[Lymphatic System|lymphatic vessels]] drain mainly into:
# Brachiocephalic nodes, in front of brachiocephalic veins
# Tracheobronchial nodes''',''' located at the distal end of the trachea<ref name=":4">Moore, KL, Dalley, AF. Clinically oriented anatomy. 6<sup>th</sup> ed. Philadelphia: Lippincott Williams & Wilkins. 2009</ref>.<ref name=":5" /> 


are involved in regulation of blood flow and systemic
== Nerve Supply ==
[[File:Course and distribution of the glossopharyngeal, vagus, and accessory nerves..gif|right|frameless|600x600px]]
The main control of the heart resides with the [[Brainstem|medulla oblongata.]]  There is an area called the cardioacceleratory centre, or pressor centre, in the upper part of the medulla oblongata, and an area called the cardioinhibitory centre, or depressor centre, in the lower part.  Together they are called the cardioregulatory centre, since they interact to control heart rate, etc.


blood pressure [2, 11].
The nervous supply to the heart is autonomic, consisting of both [[Sympathetic Nervous System|sympathetic]] and [[Parasympathetic System|parasympathetic]] parts.  The sympathetic fibres arise from the pressor centre, while the parasympathetic fibres arise in the depressor centre. See also [[Vagus Nerve|Vagal Tone]]


The cholinergic or the parasympathetic nervous system
* The sympathetic nervous system acts on the sinoatrial node, speeding up the depolarisation rate, and therefore increasing the [[Pulse rate|heart rate]]. 
* The parasympathetic system works in reverse in order to slow the heart rate down. 
* The heart itself has a natural pacemaker, the sinoatrial node, which does not need a nervous supply to function.  If you sever all the nerves to the heart, then it will continue to beat.   In fact, it will beat faster than normal, since there is normally a parasympathetic supply slowing the heart down.<ref>Basic heart Anatomy Nervous Supply Heart Available:  https://www.liverpool.ac.uk/~trh/local_html/heartdisease/nerve_supply_to_the_heart.htm (accessed18.7.2021)</ref>


effects in the heart are opposite to the ones mentioned
== Heart Conduction System ==
[[File:Heart conduction system .jpeg|right|frameless|708x708px]]
An electrical conduction system regulates the pumping of the heart and timing of contraction of various chambers.  Heart muscle contracts in response to the electrical stimulus received  system generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood. Among the major elements in the cardiac conduction system are the sinus node, atrioventricular node, and the autonomic nervous system.
# The sinus node is the heart's natural pacemaker. The sinus node is a cluster of cells situated in the upper part of the wall of the right atrium. The electrical impulses are generated there. (The sinus node is also called the sinoatrial node.)
# The electrical signal generated by the sinus node moves from cell to cell down through the heart until it reaches the atrioventricular node (the AV node), a cluster of cells situated in the center of the heart between the atria and ventricles.
# The AV node serves as a gate that slows the electrical current before the signal is permitted to pass down through to the ventricles. This delay ensures that the atria have a chance to fully contract before the ventricles are stimulated. After passing the AV node, the electrical current travels to the ventricles along special fibers embedded in the walls of the lower part of the heart.
# The autonomic nervous system (the same part of the nervous system as controls the blood pressure) controls the firing of the sinus node to trigger the start of the cardiac cycle. The autonomic nervous system can transmit a message quickly to the sinus node so it in turn can increase the heart rate to twice normal within only 3 to 5 seconds. This quick response is important during exercise when the heart has to increase its beating speed to keep up with the body's increased demand for oxygen.<ref>Medicine net Conduction system heart Available:https://www.medicinenet.com/heart_conduction_system/definition.htm (accessed 18.7.2021)</ref>


above and the transmitter involved is mainly
== Relevance to Physiotherapy ==


acetylcholine [8, 12, 13]. The vagi supply the parasympathetic
# [[File:Gym ladies.jpeg|right|frameless]]Education- Educating your clients re heart health, both for those with a heart condition and those without.  Inform them of the hearts health importance, because it pumps blood and oxygen to all of your organs. When the heart doesn’t get the care it needs, serious problems can develop in the lining of the arteries, which then lead to plaque formation which leads to Heart Disease. General advice includes


fibres to the heart via the cardiac plexuses. The
* A heart healthy [[Nutrition|diet]] is a pattern of food you eat over days, weeks and months.
* Regular [[Physical Activity|physical activity]] reduces your risk of having a [[Acute Coronary Syndrome|heart attack]] or developing [[Cardiovascular Disease|heart disease]].
* Quitting [[Smoking Cessation and Brief Intervention|smoking]] decreases your risk of heart attack and [[stroke]] almost straight away.
* Understanding and controlling [[Atherosclerosis|cholesterol]] and [[Blood Pressure|blood pressure]] is key to your heart health. <ref>Hear Foundation Heart Health Education Available:https://www.heartfoundation.org.au/heart-health-education/keeping-your-heart-healthy (accessed 18.7.2021)</ref>


parasympathetic effects are mediated via the muscaranic
2. See our many  pages on heart related health issues eg  [[Cardiac Rehabilitation]]; [[Myocardial Infarction]]; [[Atrial Fibrillation]]; [[Acute Coronary Syndrome]]; [[Physical Activity and Cardiovascular Disease]].


receptors, which act by inhibition of adenylate cyclase
== Videos ==
This 10 minute video is a good summary of the heart.<ref>Anatomy of the heart video -  © Kenhub https://www.kenhub.com/en/library/anatomy/heart</ref>{{#ev:youtube|0zM6VSlKWmw}}


and hence decrease the intracellular cAMP levels
*
{| width="100%" cellspacing="1" cellpadding="1"
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|{{#ev:youtube|HYr2NiOvjZE|400}}
|{{#ev:youtube|ecXJ7to6Lb4|400}}
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|{{#ev:youtube|hpQFToprlH8|400}}
|{{#ev:youtube|PEPjuiql72M|400}}
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and result in a decrease in heart rate, contraction and
conduction velocity [8, 12, 13].
The autonomic centres in the CNS, mainly the vasomotor
centre of medulla and the hypothalamus regulate
the balance between the level of sympathetic and the
parasympathetic output to the cardiovascular system,
depending on the afferent inputs from the periphery
and the CNS [7, 8, 12, 13]. There is normally a tonic
vagal discharge in humans, which overrides the moderate
tonic discharge in the cardiac sympathetic nerves
[7, 8, 12, 13]. Both the sympathetic and the parasympathetic
fibres in the splanchnic thoracic nerves and the
vagi carry afferent input mediated via baroreceptors and
chemoreceptors to the autonomic centres in the CNS,
in addition to the efferent output from the CNS. These
afferents and efferents are involved in mediation of cardiovascular
reflexes as baroreceptor and chemoreceptor
reflexes [7, 8, 12, 13].
The receptors of the autonomic nervous system to
the heart are the target of numerous drugs used in the
treatment of various cardiovascular disorders in both
acute and chronic settings [8, 12, 13].
=== Clinical Relevance  ===
=== Embroyology  ===
=== Histoology ===
=== Arthrokinematics ===
== Pathology/Injury  ==
== Techniques  ==
=== Palpation ===
=== Examination ===
=== Treatment ===
== Resources  ==
== Recent Related Research (from [http://www.ncbi.nlm.nih.gov/pubmed/ Pubmed])  ==
<div class="researchbox">
<rss>Feed goes here!!|charset=UTF-8|short|max=10</rss>
</div>


== References  ==
== References  ==
<references />


References will automatically be added here, see [[Adding References|adding references tutorial]].
[[Category:Anatomy]]  
 
[[Category:Heart - Anatomy]] 
<references />
[[Category:Cardiopulmonary]]
[[Category:Cardiopulmonary - Anatomy]]

Latest revision as of 12:55, 14 March 2023

Original Editor - Uchechukwu Chukwuemeka

Top Contributors - Uchechukwu Chukwuemeka, Lucinda hampton, Kim Jackson, Joao Costa, George Prudden, Sai Kripa, Admin and Adam Vallely Farrell

Introduction[edit | edit source]

The Heart surface view.jpg

The heart is a muscular organ that serves to collect deoxygenated blood from all parts of the body, carries it to the lungs to be oxygenated and release carbon dioxide. Then, it transports the oxygenated blood from the lungs and distributes it to all the body parts[1]

  • The heart pumps around 7,200 litres of blood in a day throughout the body[2].
  • The heart is situated at the centre of the chest and points slightly towards the left.
  • On average, the heart beats about 100,000 times a day, i.e., around 3 billion beats in a lifetime.
  • An adult heart beats about 60 to 80 times per minute, and newborn babies heart beats faster than an adult which is about 70 to 190 beats per minute.


Anatomy[edit | edit source]

Heart location.jpg

The heart is a conical hollow muscular organ situated in the middle mediastinum and is enclosed within the pericardium. It is positioned posteriorly to the body of the sternum with one-third situated on the right and two-thirds on the left of the midline. The heart measures 12 x 8.5 x 6 cm and weighs ~310 g (males) and ~255 g (females). It pumps blood to various parts of the body to meet their nutritive requirements. The Greek name for the heart is cardia from which we have the adjective cardia. [3]

Relations

  • Anteriorly: the body of the sternum, and adjoining costal cartilages; left lung, and pleura (apex)
  • Posteriorly: oesophagus, descending thoracic aorta, azygos, hemiazygos veins,  and thoracic duct
  • Superficially : bifurcation of the main pulmonary trunk
  • Inferiorly: diaphragm
  • Laterally: lungs, pleura[4]

Layers of the Heart Walls[edit | edit source]

Heart layers.jpg

The heart wall consists of three layers enclosed in the pericardium[1][5][6]:

  1. Epicardium - the outer layer of the wall of the heart and is formed by the visceral layer of the serous pericardium.
  2. Myocardium - the muscular middle layer of the wall of the heart and has excitable tissue and the conducting system.
  3. Endocardium .[4]
  • A middle concentric layer
  • A subendocardial layer.

The rest of the heart is composed mainly of the subepicardial and subendocardial layers.

Structure and Function[edit | edit source]

Human-heart-chambers.jpg

The heart is subdivided by septa into right and left halves, and a constriction subdivides each half of the organ into two cavities, the upper cavity being called the atrium, the lower the ventricle. The heart, therefore, consists of four chambers:

  • right atrium
  • left atrium
  • right ventricle
  • left ventricle[4].


It is best to remember the four chambers and four valves in order of the series that blood travels through the heart:

  • Venous blood returning from the body drains into the right atrium via the SVC, IVC and coronary sinus
  • The right atrium pumps blood through the tricuspid valve into the right ventricle
  • The right ventricle pumps blood through the pulmonary semilunar valve into the pulmonary trunk to be oxygenated in the lungs
  • Blood returning from the lungs drains into the left atrium via the four pulmonary veins
  • The left atrium pumps blood through the bicuspid (mitral) valve into the left ventricle
  • The left ventricle pumps blood through the aortic semilunar valve into the ascending aorta to supply the body.[4]

Heart Valves[edit | edit source]

Heart Valves.jpg

The valves of the heart maintain unidirectional flow of the blood and prevent its regurgitation in the opposite direction. There are two pairs of valves in the heart, a pair of atrioventricular valves and a pair of semilunar valves. Apart, it has four valves. All four valves of the heart have a singular purpose: allowing forward flow of blood but preventing backward flow.[7] The outflow of each chamber is guarded by a heart valve:

Atrioventricular valves between the atria and ventricles

  1. tricuspid valve (R side of the heart)
  2. mitral valve/bicuspid valve (left side of the heart)

Semilunar valves which are located in the outflow tracts of the ventricles

  1. aortic valve (L side heart)
  2. pulmonary valve (R side heart)[4]

See also Cardiac Valve Defects

Blood Supply[edit | edit source]

Overview of the coronary arteries and cardiac veins - anterior and posterior views

The heart is supplied by two coronary arteries:

  1. Left main coronary artery carries 80% of the flow to the heart muscle. It is a short artery that divides into two branches
  • Left anterior descending artery that supplies anterior two-thirds of the inter-ventricular septum and adjoining part of the left ventricular anterior wall
  • Circumflex coronary artery that supplies blood to the lateral and posterior portions of the left ventricle.

2. Right coronary artery: branches supply the right ventricle, right atrium, and left ventricle's inferior wall.

Coronary arteries and veins course over the surface of the heart. Most coronary veins coalesce into the coronary sinus that runs in the left posterior atrioventricular groove and opens into the right atrium. Other small veins, called thebesian veins, open directly into all four chambers of the heart.[7]

Image: Overview of the coronary arteries and cardiac veins - anterior and posterior views[8]

See also Coronary Artery Disease

Venous drainage and Lymphatics[edit | edit source]

Venous drainage is via the variable coronary veins and the coronary sinus[4].

The lymphatic vessels drain mainly into:

  1. Brachiocephalic nodes, in front of brachiocephalic veins
  2. Tracheobronchial nodes, located at the distal end of the trachea[9].[6] 

Nerve Supply[edit | edit source]

Course and distribution of the glossopharyngeal, vagus, and accessory nerves..gif

The main control of the heart resides with the medulla oblongata.  There is an area called the cardioacceleratory centre, or pressor centre, in the upper part of the medulla oblongata, and an area called the cardioinhibitory centre, or depressor centre, in the lower part.  Together they are called the cardioregulatory centre, since they interact to control heart rate, etc.

The nervous supply to the heart is autonomic, consisting of both sympathetic and parasympathetic parts.  The sympathetic fibres arise from the pressor centre, while the parasympathetic fibres arise in the depressor centre. See also Vagal Tone

  • The sympathetic nervous system acts on the sinoatrial node, speeding up the depolarisation rate, and therefore increasing the heart rate. 
  • The parasympathetic system works in reverse in order to slow the heart rate down. 
  • The heart itself has a natural pacemaker, the sinoatrial node, which does not need a nervous supply to function.  If you sever all the nerves to the heart, then it will continue to beat.   In fact, it will beat faster than normal, since there is normally a parasympathetic supply slowing the heart down.[10]

Heart Conduction System[edit | edit source]

Heart conduction system .jpeg

An electrical conduction system regulates the pumping of the heart and timing of contraction of various chambers.  Heart muscle contracts in response to the electrical stimulus received system generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood. Among the major elements in the cardiac conduction system are the sinus node, atrioventricular node, and the autonomic nervous system.

  1. The sinus node is the heart's natural pacemaker. The sinus node is a cluster of cells situated in the upper part of the wall of the right atrium. The electrical impulses are generated there. (The sinus node is also called the sinoatrial node.)
  2. The electrical signal generated by the sinus node moves from cell to cell down through the heart until it reaches the atrioventricular node (the AV node), a cluster of cells situated in the center of the heart between the atria and ventricles.
  3. The AV node serves as a gate that slows the electrical current before the signal is permitted to pass down through to the ventricles. This delay ensures that the atria have a chance to fully contract before the ventricles are stimulated. After passing the AV node, the electrical current travels to the ventricles along special fibers embedded in the walls of the lower part of the heart.
  4. The autonomic nervous system (the same part of the nervous system as controls the blood pressure) controls the firing of the sinus node to trigger the start of the cardiac cycle. The autonomic nervous system can transmit a message quickly to the sinus node so it in turn can increase the heart rate to twice normal within only 3 to 5 seconds. This quick response is important during exercise when the heart has to increase its beating speed to keep up with the body's increased demand for oxygen.[11]

Relevance to Physiotherapy[edit | edit source]

  1. Gym ladies.jpeg
    Education- Educating your clients re heart health, both for those with a heart condition and those without. Inform them of the hearts health importance, because it pumps blood and oxygen to all of your organs. When the heart doesn’t get the care it needs, serious problems can develop in the lining of the arteries, which then lead to plaque formation which leads to Heart Disease. General advice includes

2. See our many pages on heart related health issues eg Cardiac Rehabilitation; Myocardial Infarction; Atrial Fibrillation; Acute Coronary Syndrome; Physical Activity and Cardiovascular Disease.

Videos[edit | edit source]

This 10 minute video is a good summary of the heart.[13]


References[edit | edit source]

  1. ↑ 1.0 1.1 Kenny, WL,Wilmore, JH, Costill, DL. Cardiovascular System and its Control.  In Physiology of Sport and Exercise, 5rdedn. Human Kinetics, 2011. 140-150.
  2. ↑ Inovqheart Heart Available from: https://www.inovaheart.org/upload/docs/Healthcare%20Services/Heart%20and%20Vascular/fast-facts-about-the-heart.pdf
  3. ↑ Chaurasia BD. Human Anatomy Regional and Applied Dissection and Clinical. Vol 1. CBS Publishers and Distributors Pvt Ltd, 2010
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Radiopedia Heart Available: https://radiopaedia.org/articles/heart?lang=gb (accessed 17.6.2021)
  5. ↑ Malouf, JF, Edwards, WD, Tajil, AJ, Seward, JB. Functional anatomy of the heart. In: Fuster, F, Alexander, RW, O’Rourke, RA editors. Hurst’s: The Heart. 10th edn. McGraw-Hill Inc., 2001. p19–62.
  6. ↑ 6.0 6.1 Drake, RL, Vogl, W, Mitchell, AW, Gray, H. Gray's anatomy for Students 2nd ed.  Philadelphia : Churchill Livingstone/Elsevier, 2010.
  7. ↑ 7.0 7.1 Rehman I, Rehman A. Anatomy, Thorax, Heart. [Updated 2020 Dec 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan Available:https://www.ncbi.nlm.nih.gov/books/NBK470256/ (accessed 17.6.2021)
  8. ↑ Overview of the coronary arteries and cardiac veins - anterior and posterior views image - © Kenhub https://www.kenhub.com/en/library/anatomy/heart
  9. ↑ Moore, KL, Dalley, AF. Clinically oriented anatomy. 6th ed. Philadelphia: Lippincott Williams & Wilkins. 2009
  10. ↑ Basic heart Anatomy Nervous Supply Heart Available: https://www.liverpool.ac.uk/~trh/local_html/heartdisease/nerve_supply_to_the_heart.htm (accessed18.7.2021)
  11. ↑ Medicine net Conduction system heart Available:https://www.medicinenet.com/heart_conduction_system/definition.htm (accessed 18.7.2021)
  12. ↑ Hear Foundation Heart Health Education Available:https://www.heartfoundation.org.au/heart-health-education/keeping-your-heart-healthy (accessed 18.7.2021)
  13. ↑ Anatomy of the heart video - © Kenhub https://www.kenhub.com/en/library/anatomy/heart
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