Heart Flashcards
1
Q
Where does the aorta arise from
A
the aortic orifice at the base of the left ventricle, with inflow via the aortic valve. Its first segment is known as the ascending aorta, which lies within the pericardium (covered by the visceral layer).
2
Q
Is the first segment of the aorta covered but the pericardium
A
Its first segment is known as the ascending aorta, which lies within the pericardium (covered by the visceral layer).
3
Q
The second continuous segment is the arch of the aorta, from which branch the major arteries to the head, neck and upper limbs. These are:
A
Brachiocephalic trunk
Left common carotid artery
Left subclavian artery
4
Q
Where does the descending` aorta travel
A
After the arch of the aorta, the aorta then becomes the descending aorta which continues down through the diaphragm into the abdomen.
5
Q
What do The pulmonary arteries do
A
The pulmonary arteries
6
Q
From where do the pulmonary arteries arise? and where are they located
A
The arteries begin as the pulmonary trunk, a thick and short vessel, which is separated from the right ventricle by the pulmonary valve. The trunk is located anteriorly and medially to the right atrium, sharing a common layer of pericardium with the ascending aorta. It continues upwards, overlapping the root of the aorta and passing posteriorly.
7
Q
Around which level does the pulmonary trunk split into right and left arteries
A
T5-T6
8
Q
What does the left pulmonary artery supply
A
supplies blood to the left lung, bifurcating into two branches to supply each lobe of the lung.
9
Q
What does the right pulmonary artery supply
A
The right pulmonary artery is the thicker and longer artery of the two, supplying blood to the right lung. It also further divides into two branches.
10
Q
What do the pulmonary veins do
A
The pulmonary veins receive oxygenated blood from the lungs, delivering it to the left side of the heart to be pumped back around the body.
11
Q
How many Pulmonary veins?
A
There are four pulmonary veins, with one superior and one inferior for each of the lungs.
12
Q
Why do the pulmonary veins run into the pericardium
A
They enter the pericardium to drain into the superior left atrium, on the posterior surface. The oblique pericardial sinus can be found within the pericardium, between the left and right veins.
13
Q
what do The superior pulmonary veins and inferior do
A
The superior pulmonary veins return blood from the upper lobes of the lung, with the inferior veins returning blood from the lower lobes.
14
Q
Where is the left inferior pulmonary vein found?
A
The inferior left pulmonary vein is found at the hilum of the lung
15
Q
Where is the right inferior pulmonary vein found
A
the right inferior pulmonary vein runs posteriorly to the superior vena cava and the right atrium.
16
Q
The function of Superior vena cava
A
The superior vena cava receives deoxygenated blood from the upper body (superior to the diaphragm, excluding the lungs and heart), delivering it to the right atrium.
17
Q
How is superior Vena cava formed
A
It is formed by merging of the brachiocephalic veins, travelling inferiorly through the thoracic region until draining into the superior portion of the right atrium at the level of the 3rd rib.
As the superior vena cava makes its descent it is located in the right side of the superior mediastinum, before entering the middle mediastinum to lie beside the ascending aorta.
18
Q
The function of Inferior Vena Cava
A
The inferior vena cava receives deoxygenated blood from the lower body (all structures inferior to the diaphragm), delivering it back to the heart.
19
Q
Formation of the inferior vena cava
A
It is initially formed in the pelvis by the common iliac veins joining together. It travels through the abdomen, collecting blood from the hepatic, lumbar, gonadal, renal and phrenic veins. The inferior vena cava then passes through the diaphragm, entering the pericardium at the level of T8. It drains into the inferior portion of the right atrium
20
Q
Where does the heart lie
A
Middle Mediastinum
21
Q
Where does apex point
A
anterior-inferior direction.
22
Q
Anterior (or sternocostal)
A
Right ventricle.
23
Q
Posterior (or base)
A
Left atrium
24
Q
Inferior (or diaphragmatic)
A
Left and right ventricles.
25
Right pulmonary
Right atrium.
26
Left pulmonary
Left ventricle
27
Right border
Right atrium
28
Inferior border
Left ventricle and right ventricle
29
Left border
Left ventricle (and some of the left atrium)
30
Superior border
Right and left atrium and the great vessels
31
What are the Sulci
On the interior, it is divided into four chambers. These divisions create grooves on the surface of the heart – these are known as sulci.
32
Where does the coronary sulcus (or atrioventricular groove) run
runs transversely around the heart
33
What does runs transversely around the heart represent
it represents the wall dividing the atria from the ventricles. The sinus contains important vasculature, such as the right coronary artery.
34
Where do the anterior and posterior interventricular sulci run and what do they represent
can be found running vertically on their respective sides of the heart. They represent the wall separating the ventricles.
35
What are the pericardial sinuses
The pericardial sinuses are not the same as ‘anatomical sinuses’ (such as the paranasal sinuses). They are passageways formed the unique way in which the pericardium folds around the great vessels.
36
What is The oblique pericardial sinus
is a blind ending passageway (‘cul de sac’) located on the posterior surface of the heart.
37
What is The transverse pericardial sinus
is found superiorly on the heart. It can be used in coronary artery bypass grafting
38
Location of the Transverse pericardial sinus
1 Posterior to the ascending aorta and pulmonary trunk.
2 Anterior to the superior vena cava.
3 Superior to the left atrium.
39
Importance of location of transverse pericardial sinus
In this position, the transverse pericardial sinus separates the arterial vessels (aorta, pulmonary trunk) and the venous vessels (superior vena cava, pulmonary veins) of the heart.
This can be used to identify and subsequently ligate (to tie off) the arteries of the heart during coronary artery bypass grafting.
40
Function of right atrium
The right atrium receives deoxygenated blood from the superior and inferior vena cavae, and from the coronary veins. It pumps this blood through the right atrioventricular orifice (guarded by the tricuspid valve) into the right ventricle.
41
In the anatomical position, the right atrium forms the right border of the heart what extends from this
Extending from the antero-medial portion of the chamber is the right auricle (right atrial appendage) – a muscular pouch that acts to increase the capacity of the atrium.
42
The interior surface of the right atrium can be divided into two parts, each with a distinct embryological origin. These two parts are separated by a muscular ridge Called?
crista terminalis
43
Two parts of interior surface of right atrium
Sinus venarum
Atrium proper
44
Atrium proper
located anterior to the crista terminalis, and includes the right auricle. It is derived from the primitive atrium, and has rough, muscular walls formed by pectinate muscles.
45
Sinus Venarum
located posterior to the crista terminalis. This part receives blood from the superior and inferior vena cavae. It has smooth walls and is derived from the embryonic sinus venosus.
46
The coronary sinus
receives blood from the coronary veins. It opens into the right atrium between the inferior vena cava orifice and the right atrioventricular orifice.
47
interatrial septum
is a solid muscular wall that separates the right and left atria.
48
the septal wall in the right atrium is marked by a small oval-shaped depression called
fossa ovalis
49
The fossa ovalis
the foramen ovale in the foetal heart, which allows right to left shunting of blood to bypass the lungs. It closes once the newborn takes its first breath
50
Atrial Septal Defect
An atrial septal defect is an abnormal opening in the interatrial septum, persistent after birth. The most common site is the foramen ovale, and this is known as a patent foramen ovale.
In the adult, left atrial pressure is usually greater than that of the right atrium, so blood is shunted through the opening from left to right. In large septal defects, this can cause right ventricular overload, leading to pulmonary hypertension, right ventricular hypertrophy and ultimately right heart failure.
Definitive treatment is closure of the defect by surgical or transcatheter closure.
51
The function fo the left atrium
The left atrium receives oxygenated blood from the four pulmonary veins, and pumps it through the left atrioventricular orifice (guarded by the mitral valve) into the left ventricle.
52
In the anatomical position where is the left atrium
In the anatomical position, the left atrium forms the posterior border (base) of the heart. The left auricle extends from the superior aspect of the chamber, overlapping the root of the pulmonary trunk.
53
The interior surface of the left atrium can be divided into two parts, each with a distinct embryological origin:
1 Inflow portion
| 2 Outflow portion
54
Inflow portion
receives blood from the pulmonary veins. Its internal surface is smooth and it is derived from the pulmonary veins themselves.
55
Outflow Portion
located anteriorly, and includes the left auricle. It is lined by pectinate muscles, and is derived from the embryonic atrium.
56
Purpose of the Ventricles
The left and right ventricles of the heart receive blood from the atria and pump it into the outflow vessels; the aorta and the pulmonary artery respectively.
57
The right ventricle
The right ventricle receives deoxygenated blood from the right atrium, and pumps it through the pulmonary orifice (guarded by the pulmonary valve), into the pulmonary artery.
58
It is triangular in shape, and forms the majority of the anterior border of the heart. The right ventricle can be divided into an inflow and outflow portion, which are separated by a muscular ridge known as the
supraventricular crest.
59
The interior of the inflow part of the right ventricle is covered by a series of irregular muscular elevations, called
trabeculae carnae
60
What part of the right ventricle is covered by trabeculae carnae
The interior of the inflow part of the right ventricle
61
Three types of trabeculae carnae
Ridges
Bridges
Pillars
62
Trabeculae Carnae - Ridges
attached along their entire length on one side to form ridges along the interior surface of the ventricle.
63
Trabeculae Carnae - Bridges
attached to the ventricle at both ends, but free in the middle. The most important example of this type is the moderator band, which spans between the interventricular septum and the anterior wall of the right ventricle. It has an important conductive function, containing the right bundle branches.
64
Trabeculae Carnae - Pillars
(papillary muscles) – anchored by their base to the ventricles. Their apices are attached to fibrous cords (chordae tendineae), which are in turn attached to the three tricuspid valve cusps. By contracting, the papillary muscles ‘pull’ on the chordae tendineae to prevent prolapse of the valve leaflets during ventricular systole.
65
Outflow Portion (Conus arteriosus) of right ventricle
The outflow portion (leading to the pulmonary artery) is located in the superior aspect of the ventricle. It is derived from the embryonic bulbus cordis. It is visibly different from the rest of the right ventricle, with smooth walls and no trabeculae carneae.
66
The interventricular septum
separates the two ventricles, and is composed of a superior membranous part and an inferior muscular part.
67
Difference between the two types of the interventricular septum
The muscular part forms the majority of the septum and is the same thickness as the left ventricular wall. The membranous part is thinner, and part of the fibrous skeleton of the heart.
68
Inflow Portion of Left Ventricle
The walls of the inflow portion of the left ventricle are lined by trabeculae carneae, as described with the right ventricle. There are two papillary muscles present which attach to the cusps of the mitral valve.
69
The outflow part of the left ventricle is known as the
aortic vestibule
70
Structure of outflow portion of the left ventricle
It is smooth-walled with no trabeculae carneae, and is a derivative of the embryonic bulbus cordis.
71
The sequence of electrical events during one full contraction of the heart muscle: 5 steps
1 An excitation signal (an action potential) is created by the sinoatrial (SA) node.
2 The wave of excitation spreads across the atria, causing them to contract.
3 Upon reaching the atrioventricular (AV) node, the signal is delayed.
4 It is then conducted into the bundle of His, down the interventricular septum.
5 The bundle of His and the Purkinje fibres spread the wave impulses along the ventricles, causing them to contract.
72
The sequence of electrical events during one full contraction of the heart muscle: 5 steps
1 An excitation signal (an action potential) is created by the sinoatrial (SA) node.
2 The wave of excitation spreads across the atria, causing them to contract.
3 Upon reaching the atrioventricular (AV) node, the signal is delayed.
4 It is then conducted into the bundle of His, down the interventricular septum.
5 The bundle of His and the Purkinje fibres spread the wave impulses along the ventricles, causing them to contract.
73
What is the SAN and where is it located
The sinoatrial (SA) node is a collection of specialised cells (pacemaker cells), and is located in the upper wall of the right atrium, at the junction where the superior vena cava enters.
74
What does the SAN do
These pacemaker cells can spontaneously generate electrical impulses. The wave of excitation created by the SA node spreads via gap junctions across both atria, resulting in atrial contraction (atrial systole) – with blood moving from the atria into the ventricles.
75
What does the Sympathetic nervous system do the rate of SAN impulses
increases firing rate of the SA node, and thus increases heart rate.
76
What is the AVN and where is it located
After the electrical impulses spread across the atria, they converge at the atrioventricular node – located within the atrioventricular septum, near the opening of the coronary sinus.
77
What does the AVN do
The AV node acts to delay the impulses by approximately 120ms, to ensure the atria have enough time to fully eject blood into the ventricles before ventricular systole.
The wave of excitation then passes from the atrioventricular node into the atrioventricular bundle.
78
What is the atrioventricular bundle
The atrioventricular bundle (bundle of His) is a continuation of the specialised tissue of the AV node, and serves to transmit the electrical impulse from the AV node to the Purkinje fibres of the ventricles.
79
Where is the atrioventricular bundle
It descends down the membranous part of the interventricular septum, before dividing into two main bundles
80
Two main bundles of the bundle of His
Right bundle branch – conducts the impulse to the Purkinje fibres of the right ventricle
Left bundle branch – conducts the impulse to the Purkinje fibres of the left ventricle.
81
What are the purkinje fibres
The Purkinje fibres (sub-endocardial plexus of conduction cells) are a network of specialised cells. They are abundant with glycogen and have extensive gap junctions.
82
Where are the purkinje fibres located
These cells are located in the subendocardial surface of the ventricular walls, and are able to rapidly transmit cardiac action potentials from the atrioventricular bundle to the myocardium of the ventricles.
83
What do the purkinje fibres allow
This rapid conduction allows coordinated ventricular contraction (ventricular systole) and blood is moved from the right and left ventricles to the pulmonary artery and aorta respectively.
84
The heart wall itself can be divided into three distinct layers:
the endocardium, myocardium, and epicardium.
85
he innermost layer of the cardiac wall is known
Endocardium
86
What does the endocardium line
It lines the cavities and valves of the heart.
87
What is the endocardium composed of
Structurally, the endocardium is comprised of loose connective tissue and simple squamous epithelial tissue – it is similar in its composition to the endothelium which lines the inside of blood vessels.
88
In addition to lining the inside of the heart, the endocardium also does what
also regulates contractions and aids cardiac embryological development.
89
The subendocardial layer lies between, and joins
the endocardium and the myocardium.
90
subendocardial layer consists of
consists of a layer of loose fibrous tissue, containing the vessels and nerves of the conducting system of the heart. The purkinje fibres are located in this layer.
91
As the subendocardial layer houses the conducting system of the heart, damage to this layer can result in various
arrhythmias.
92
What is the myocardium and what does it do
The myocardium is composed of cardiac muscle and is an involuntary striated muscle. The myocardium is responsible for contractions of the heart.
93
The subepidcardial layer
lies between, and joins, the myocardium and the epicardium
94
What is the epicardium and what is it composed of
The epicardium is the outermost layer of the heart, formed by the visceral layer of the pericardium.
95
What is the epicardium composed of
It is composed of connective tissue and fat. The connective tissue secretes a small amount of lubricating fluid into the pericardial cavity.
In addition to the connective tissue and fat, the epicardium is lined by on its outer surface by simple squamous epithelial cells.
96
What is the epicardium composed of
It is composed of connective tissue and fat. The connective tissue secretes a small amount of lubricating fluid into the pericardial cavity.
In addition to the connective tissue and fat, the epicardium is lined by on its outer surface by simple squamous epithelial cells.
97
What is the pericardium
is a fibroserous, fluid-filled sack that surrounds the muscular body of the heart and the roots of the great vessels (the aorta, pulmonary artery, pulmonary veins, and the superior and inferior vena cavae).
98
2 Layers of pericardium
a tough external layer known as the fibrous pericardium,
thin internal layer known as the serous pericardium
(to overextend the orange metaphor, the outer peel could be thought of as the fibrous layer, with the inner white stuff being the serous layer).
99
Fibrous Pericardium
Continuous with the central tendon of the diaphragm, the fibrous pericardium is made of tough connective tissue and is relatively non-distensible. Its rigid structure prevents rapid overfilling of the heart, but can contribute to serious clinical consequences (see cardiac tamponade).
100
Serous Pericardium
Enclosed within the fibrous pericardium, the serous pericardium is itself divided into two layers:
the outer parietal layer that lines the internal surface of the fibrous pericardium
the internal visceral layer that forms the outer layer of the heart (also known as the epicardium). Each layer is made up of a single sheet of epithelial cells, known as mesothelium.
101
What is Found between the outer and inner serous layers
pericardial cavity
102
What is the pericardial cavity
contains a small amount of lubricating serous fluid. The serous fluid serves to minimize the friction generated by the heart as it contracts.
103
Fart Police Smell Villains:
F – Fibrous layer of the pericardium
P – Parietal layer of the serous pericardium
S – Serous fluid
V – Visceral layer of the serous pericardium
104
4 Functions of Pericardium. 1
Fixes the heart
in the mediastinum and limits its motion. Fixation of the heart is possible because the pericardium is attached to the diaphragm, the sternum, and the tunica adventitia (outer layer) of the great vessels
105
4 Functions of Pericardium. 2
Prevents overfilling of the heart. The relatively inextensible fibrous layer of the pericardium prevents the heart from increasing in size too rapidly, thus placing a physical limit on the potential size of the organ
106
4 Functions of Pericardium. 3
Lubrication. A thin film of fluid between the two layers of the serous pericardium reduces the friction generated by the heart as it moves within the thoracic cavity
107
4 Functions of Pericardium. 4
Protection from infection. The fibrous pericardium serves as a physical barrier between the muscular body of the heart and adjacent organs prone to infection, such as the lungs.
108
somatic innervation of the pericardium is caused by
The phrenic nerve (C3-C5)
109
What does phrenic nerve do
The phrenic nerve (C3-C5) is responsible for the somatic innervation of the pericardium, as well as providing motor and sensory innervation to the diaphragm.
110
Where does the phrenic nerve originate
Originating in the neck and travelling down through the thoracic cavity, the phrenic nerve is a common source of referred pain, with a key example being shoulder pain experienced as a result of pericarditis.
111
Atrioventricular valves:
The tricuspid valve and mitral (bicuspid) valve. They are located between the atria and corresponding ventricle.
112
Semilunar valves:
The pulmonary valve and aortic valve. They are located between the ventricles and their corresponding artery, and regulate the flow of blood leaving the heart.
113
The atrioventricular valves are located between
the atria and the ventricles. They close during the start of ventricular contraction (systole), producing the first heart sound
114
Tricuspid valve
located between the right atrium and the right ventricle (right atrioventricular orifice). It consists of three cusps (anterior, septal and posterior), with the base of each cusp anchored to a fibrous ring that surrounds the orifice.
115
Three cusps of tricuspid valve
anterior, septal and posterior
116
Mitral valve
located between the left atrium and the left ventricle (left atrioventricular orifice). It is also known as the bicuspid valve because it has two cusps (anterior and posterior). Like the tricuspid valve, the base of each cusp is secured to fibrous ring that surrounds the orifice.
117
The mitral and tricuspid valves are supported by the attachment of fibrous cords to the free edges of the valve cusps. These are called ?
chordae tendineae
118
The chordae tendineae are attached to ... Located Where?
papillary muscles, located on the interior surface of the ventricles – these muscles contract during ventricular systole to prevent prolapse of the valve leaflets into the atria.
119
How many papillary muscles?
5
120
The semilunar valves are located where ?
The semilunar valves are located between the ventricles and outflow vessels. They close at the beginning of ventricular relaxation (diastole), producing the second heart sounds
121
Pulmonary valve
located between the right ventricle and the pulmonary trunk (pulmonary orifice). The valve consists of three cusps – left, right and anterior (named by their position in the foetus before the heart undergoes rotation).
122
Aortic valve
located between the left ventricle and the ascending aorta (aortic orifice). The aortic valve consists of three cusps – right, left and posterior.
The left and right aortic sinuses mark the origin of the left and right coronary arteries. As blood recoils during ventricular diastole, it fills the aortic sinuses and enters the coronary arteries to supply the myocardium.
123
t he pulmonary and aortic valves have a similar structure
| How?
The sides of each valve leaflet are attached to the walls of the outflow vessel, which is slightly dilated to form a sinus. The free superior edge of each leaflet is thickened (the lunule), and is widest in the midline (the nodule).
124
There are two main coronary arteries which branch to supply the entire heart. They are named the left and right coronary arteries, and arise from
the left and right aortic sinuses within the aorta.
125
The aortic sinuses
are small openings found within the aorta behind the left and right flaps of the aortic valve. When the heart is relaxed, the back-flow of blood fills these valve pockets, therefore allowing blood to enter the coronary arteries.
126
The left coronary artery (LCA) Branches where
initially branches to yield the left anterior descending (LAD), also called the anterior interventricular artery. The LCA also gives off the left marginal artery (LMA) and the left circumflex artery (Cx). In ~20-25% of individuals, the left circumflex artery contributes to the posterior interventricular artery (PIv).
127
The right coronary artery (RCA) branches where
branches to form the right marginal artery (RMA) anteriorly. In 80-85% of individuals, it also branches into the posterior interventricular artery (PIv) posteriorly.
128
Blood travels from the subendocardium into the thebesian veins what are these?
which are small tributaries running throughout the myocardium. These in turn drain into larger veins that empty into the coronary sinus.
129
The coronary sinus is?
is the main vein of the heart, located on the posterior surface in the coronary sulcus, which runs between the left atrium and left ventricle.
130
Where does the coronary sinus drain
The sinus drains into the right atrium. Within the right atrium, the opening of the coronary sinus is located between the right atrioventricular orifice and the inferior vena cava orifice.
131
There are five tributaries which drain into the coronary sinus:
1. The great cardiac vein
2. The small cardiac vein
3. middle cardiac vein
4. left marginal vein.
5. left posterior ventricular vein
132
The great cardiac vein
is the main tributary. It originates at the apex of the heart and follows the anterior interventricular groove into the coronary sulcus and around the left side of the heart to join the coronary sinus.
133
The small cardiac vein
is also located on the anterior surface of the heart. This passes around the right side of the heart to join the coronary sinus.
134
Middle cardiac Vein
Another vein which drains the right side of the heart is the middle cardiac vein. It is located on the posterior surface of the heart.
135
The marginal Vein
On the left posterior side
136
Left posterior ventricular vein
In the centre is the left posterior ventricular vein which runs along the posterior interventricular sulcus to join the coronary sinus.
137
Route of the right coronary artery
The RCA passes to the right of the pulmonary trunk and runs along the coronary sulcus before branching. The right marginal artery arises from the RCA and moves along the right and inferior border of the heart towards the apex. The RCA continues to the posterior surface of the heart, still running along the coronary sulcus. The posterior interventricular artery then arises from the RCA and follows the posterior interventricular groove towards the apex of the heart.
138
Route of the left coronary artery
The LCA passes between the left side of the pulmonary trunk and the left auricle. The LCA divides into the anterior interventricular branch and the circumflex branch. The anterior interventricular branch (LAD) follows the anterior interventricular groove towards the apex of the heart where it continues on the posterior surface to anastomose with the posterior interventricular branch. The circumflex branch follows the coronary sulcus to the left border and onto the posterior surface of the heart. This gives rise to the left marginal branch which follows the left border of the heart.
139
Right coronary supplies
Right atrium
SA and AV nodes
Posterior part of interventricular septum (IVS)
140
RCA vein draining region
Small cardiac vein
| Middle cardiac vein
141
Right marginal supplies
Right ventricle
| Apex
142
Right marginal vein draining region
Small cardiac vein
| Middle cardiac vein
143
Posterior interventricular artery supplies
Right ventricle
Left ventricle
Posterior 1/3 of IVS
144
Posterior interventricular artery vein draining region
Left posterior ventricular vein
145
LCA supplies
Left atrium
Left ventricle
IVS
AV bundles
146
LCA vein draining region
Great cardiac vein
147
Left anterior descending artery supplies
Right ventricle
Left ventricle
Anterior 2/3 IVS
148
Left anterior descending artery vein draining region
Great cardiac vein
149
Left marginal artery supplies
Left ventricle
150
Left marginal artery vein draining region
Left marginal vein
| Great cardiac vein
151
Circumflex artery supplies
Left atrium
| Left ventricle
152
Circumflex artery vein draining region
Great cardiac vein
153
Myosin Thick or thin? Function?
Thick filament
| Hydrolyses ATP, interacts with Actin
154
Actin Thick or thin? Function?
Thin filament
| Activates myosin ATP, interacts with myosin
155
Tropomyosin Thick or thin? Function?
Thin filament
| Modulates actin-myosin interaction
156
Troponin C Thick or thin? Function?
Thin filament
| Binds Ca2+
157
Troponin I Thick or thin? Function?
Thin filament
| Inhibits actin-myosin interaction
158
Troponin T Thick or thin? Function?
Thin filament
| Binds troponin complex to thin filament
159
The basic three events of contraction are:
- LV contraction,
- LV relaxation,
- LV filling.
160
What do the basic event of contraction include in compliance with the Wiggers diagram
```
LV contraction:
- Isovolumic contraction ( b )
- Maximal ejection ( c )
LV relaxation:
- Start of relaxation and reduced ejection ( d )
- Isovolumic relaxation ( e )
- Rapid LV filling and LV suction ( f )
- Slow LV filling (diastasis) ( g )
- Atrial booster ( a ).
```
161
Describe Ventricular contraction: Systole
Wave of depolarisation arrives,
Opens the L-calcium tubule, {ECG: Peak of R},
Ca2+ arrive at the contractile proteins,
LVp rises > LAp:
MV closes: M1 of the 1st HS,
LVp rises (isovolumic contraction) > Aop,
AoV opens and Ejection starts.
162
Describe Ventricular relaxation: Diastole
LVp peaks then decreases.
Influence of phosphorylated phospholambdan, cytosolic calcium is taken up into the SR.
“phase of reduced ejection”.
Ao flow is maintained by aortic distensibility.
LVp < Ao p, Ao. valve closes, A2 of the 2nd HS.
“isovolumic relaxation”, then “MV opens”.
163
Describe Ventricular filling
```
LVp < LAp, MV opens, Rapid (E) filling starts.
Ventricular suction (active diastolic relaxation), may also contribute to E filling (esp. ex. ?S3).
Diastasis (separation): LVp=LAp, filling temporarily stops.
Filling is renewed when A contraction (booster), raises LAp creating a pressure gradient.(path, S4)
```
164
Preload:
is the load present before LV contraction has started.
165
Afterload:
is the load after the ventricle starts to contract.
166
Starling’s Law of the heart:
Starling 1918: Within physiologic limits, the larger the volume of the heart, the greater the energy of its contraction and the amount of chemical change at each contraction.
LV filling pressure: is the difference between LAp and LV diastolic pressure.
The relationship reaches a plateau.
167
The Force-Length Interaction & Starling’s law
The force produced by the skeletal muscle declines when the sarcomere is less than the optimal length (Actin’s projection from Z disc “1μm” X 2).
In the cardiac sarcomere, at 80% of the optimal length, only 10% of the maximal force is produced!
168
“All or none”
The cardiac sarcomere must function near the upper limit of their maximal length (LMAX) = 2.2 μm.
The physiologic LV volume changes are affected when the sarcomere lengthens from 85% of LMAX to LMAX!
Steep relationship: length-dependent activation.
169
Frank & isovolumic contraction
The heart can, during the cycle, increase and decrease the pressure even if the volume is fixed.
Increasing diastolic heart volume, leads to increased velocity and force of contraction (Frank 1895).
This is the positive inotropic effect.
Ino: Fibre (Greek); tropus: move (Greek).
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Contractility (inotropic state):
the state of the heart which enables it to increase its contraction velocity, to achieve higher pressure, when contractility is increased (independent of load)
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Elasticity,
is the myocardial ability to recover its normal shape after removal of systolic stress.
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Compliance
is the relationship between the change in stress and the resultant strain.(dP/dV).
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Diastolic distensibility
is the pressure required to fill the ventricle to the same diastolic volume.
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The pressure-volume loop reflects
contractility in the end-systolic pressure volume relationship,
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while compliance is reflected at
the end diastolic pressure volume relationship.
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Isometric vs. Isotonic contraction
Iso = the same (Greek),
Metric = length (Greek),
Tonic = contractile force (Greek),
-The force-velocity curve may be a combination of initial isometric conditions followed by isotonic contraction.
-The isometric conditions can be found during isovolumic contraction, isotonic contraction is totally impossible in the heart, given the constantly changing load.
