Pathophysiology Exam #1 Flashcards
What are the 6 functions of the cardiovascular system?
- Deliver sufficient oxygen to tissues to meet metabolic demand
- Transport metabolic waste products (carbon dioxide) from tissues and delivery to lungs for elimination
- Transport of metabolic waste products to the kidneys for elimination
- Supply of nutrients absorbed from GI tract to the tissues
- Regulation of body temperature
- Transport of hormones and other substances that regulate cellular function
How dose the CV system regulate temperature?
o vasoconstriction and dilation
In what way does the heart act as an endocrine organ?
• Heart is also an endocrine organ; which secretes:
o atrial natriuretic peptide (ANP)
o brain natriuretic peptide (BNP)
The heart is located within the _____;
the mediastinum is located between the _____;
posterior to the _____ and anterior to the _____ _____
- mediastinum
- lungs
- sternum
- vertebral column
From an anterior prospective, you can visual the _____ side of the heart more than the _____ side
- R side
- L side
When the aorta pierces the diaphragm, it changes
from the _____ aorta to the _____ aorta
- thoracic aorta
- abdominal aorta
The heart is enclosed within the _____ cavity.
pericardial
The lungs are enclosed with the _____ cavity.
pleural
The only thing separating the parietal pericardium with the parietal pleural (these are both the out layer
membranes of the heart and lungs) is this little fibrous band called the?
FIBROUS PERICARDIUM; The heart and lungs sit very close together, so you can see why when we make changes to our ventilators (positive pressure ventilation) how that can have CV implications
Where is the right auricle located and what is its function?
- connected to(muscle flap) the right atrium
- It collects deoxygenated blood from the bloodstream and moves it into the heart’s right ventricle
R coronary artery that immediately branches off the _____ and runs thru what is called the _____ _____; which lies between?
- aorta
- coronary sulcus
- right and left ventricle
Then that R coronary artery continues on to the posterior aspect of the heart
Which coronary arteries perfuses the majority of the myocardium?
Left anterior descending artery(LAD)
Does the superior/inferior vena cava bring oxygenated blood back to the heart or deoxygenated?
Superior vena cava bringing deoxygenated blood from the upper part of the body and inferior from the lower
Which brings oxygenated blood from the lungs to the heart, the pulmonary veins or the pulmonary arteries?
-Pulmonary arteries bringing deoxygenated blood to the lungs
-Pulmonary veins bringing oxygenated blood
from the lungs
-Away (from the heart) = artery; back to the heart = veins
pulmonary circulation opposite of systemic circulation
In most people, that coronary artery descends down in the sulcus between the L and R ventricles posteriorly;
that is called the _______ _____ _____.
- POSTERIOR DESCENDING ARTERY(PDA)
- R coronary artery: it descends thru the coronary sulcus and then continues around the posterior aspect of the heart
The coronary veins eventually join back together to form the _____ _____ _____. This structure then empties into the _____ _____, which carries _____ blood.
-all the veins eventually join back together to form the
GREAT CARDIAC VEIN
-That great cardiac vein will empty into the CORONARY SINUS; the coronary sinus empties all it’s deoxygenated blood
What are two factors that are responsible for a decrease in PaO2 on the left side of the heart as compared tot he pulmonary capillaries?
So you have two factors that decrease PaO2: THEBESIAN VEINS and the BRONCHIAL CIRCULATION
How are the Thebesian veins responsible for a decrease of PaO2 on the left heart?
-If the thebesian veins are permeating thru the myocardium and emptying deoxygenated blood into the 4 chambers of the heart; that decreases PaO2 on the L side
o That’s one of the reasons why the PaO2 in the L side of the heart is less than the PaO2 at the actual pulmonary capillaries
What are the Thebesian veins?
Tiny veins that permeate the walls of the myocardium and
empty their deoxygenated blood to all four chambers of the heart
What are the 2 types of pulmonary circulation?
There are two types of pulm circulation:
§ There is the pulm circulation that is picking up freshly
oxygenated from the alveoli
§ There is also the bronchial circulation; we want to think
about the blood being delivered to the conductive airways
v
How is bronchial circulation responsible for a decrease of PaO2 on the left heart?
There is also the bronchial circulation; we want to think
about the blood being delivered to the conductive airways
v like the tracheal-bronchial tree
v where gas exchange doesn’t actually occur but those tissues still need to be perfused
v the deoxygenated blood from those tissues is returned back to the L side of the heart; which further decreases the PaO2
What are the three layers of the heart in order from outside to inside?
- epicardium
- myocardium
- endocardium
EPI -> MYO ->ENDO; EPI -> MYO ->ENDO;
What are the characteristics of the epicardium?
• Outer layer you have the epicardium or the visceral
pericardium (same thing)
o inseparable from the heart
o composed of squamous epithelial cells and
connective tissues and fat
What are the characteristics of the myocardium?
• Then you have the myocardium; the muscle cells
o The myocardium or muscle thickness is based
upon which chamber of the heart you look at:
§ L ventricle -> R ventricle -> L atrium -> R atrium (thickest to thinnest)
o When people get cardiomyopathies, this is the
layer that hypertrophies
These finger-like projections are found in all 4 chambers of the heart but especially the left ventricle. They are responsible for creating turbulence of blood flow within the chambers; keeps the blood from clotting. Another theory is they also if the chamber of the heart
was smooth, when it contracted, that smooth
wall would actually collapse in on itself; gives the walls a structure/ function that does not allow them to collapse onto itself during contraction
TRABECULAE CARNEAE
The pericardial cavity or the pericardium is made up of two structures what are they?
- fibrous pericardium
- serious pericardium
What is the function of the fibrous pericardium, and what is it attached to?
Fibrous pericardium is on the outer portion of the parietal pericardium and that is connective tissues that anchors the heart to adjacent structures
What are the two parts of the serious pericardium?
The parietal pericardium and the visceral pericardium
What is the function of the parietal pericardium?
It is the outside layer of the serious pericardium that the fibrous pericardium attaches to.
o Both the visceral and parietal pericardium are SEROUS pericardium
§ meaning they secrete a serous fluid into the pericardial cavity
§ normally there is only 15-20 mL of serous fluid in the pericardial cavity
What is the function of the visceral pericardium?
that is the pericardial membrane that is directly attached to the heart; inseparable to the heart
o When that visceral pericardium gets up to the great vessels it turns outward on itself and becomes the
parietal pericardium
o Both the visceral and parietal pericardium are SEROUS pericardium
§ meaning they secrete a serous fluid into the pericardial cavity
§ normally there is only 15-20 mL of serous fluid in the pericardial cavity
In between the visceral and parietal pericardium is the?
PERICARDIAL CAVTIY or PERICARDIAL SPACE
What is the function of the serous fluid which lies within the pericardial cavity/space?
v that very thin layer of serous fluid allows for the pericardial membranes to glide over each other
during systole and diastole
o Both the visceral and parietal pericardium are SEROUS pericardium
§ meaning they secrete a serous fluid into the pericardial cavity
How much serous fluid is located in the pericardial cavity normally?
15-20 mls;so if you think about the heart being about the size of a human fist, that is a very thin layer of fluid surrounding the heart
Inflammation of the pericardial membranes, what is the diagnosis?
pericarditis
What are the two types of pericarditis?
o Infectious: such as microorganisms, bacterial, viral, and fungi
o Non-infectious: idiopathic/ I don’t know why they have it, pericarditis
What is heard via auscultation with pericarditis, and where is the best place to hear it?
- pericardial friction rub(grating sound (two pieces of sand paper rubbing together)
- Best heard over the 5th intercostal space, L sternal border
How does pericarditis pain differ from MI pain?
o MI = constant pain, radiating to the shoulder or arm, pressure pain or elephant on chest
o Pericarditis = very sharp pain, varies with inspiration/ expiration, with no radiating pain to arm
What is a pericardial effusion, and what causes it?
- excessive amount of fluid within the pericardial cavity/ space
- When you have pericarditis, that increases the capillary permeability in the pericardial membranes, with increase permeability, excess fluid gets within the pericardial cavity/ space; which causes a pericardial effusion
What is a cardiac tamponade?
o At some point when the heart cannot compensate anymore and there are CV manifestations, from the pericardial effusions; this is when it becomes a cardiac tamponade
o So if someone has a pericardial effusion that has accumulated over a long period of time; they are able to compensate
o If that fluid accumulates very rapidly, they cannot compensate and develop cardiac tamponade
What is the best anesthesia management of cardiac tamponade(5)?
- “Full, Fast, Forward”
- Fixed Stroke Volume
- Avoid bradycardia
- Avoid vasodilators
- Optimize volume status to maximize LV filling
- Maintain sympathetic tone
- Spontaneous ventilation
Why should vasodilators be avoided for the anesthesia management of cardiac tamponade?
- Run the risk of venodilation that will decrease preload
- Preload is everything in these cases
Why should spontaneous ventilation be preferred in the anesthesia management of cardiac tamponade?
-Preload is already compromised
-Positive pressure ventilation increases intrathoracic pressure that decreases preload even more and
have profound cardiovascular collapse
Are there any valves between the superior and inferior vena cava and the right atrium?
no
Is CVP = R atrial pressure?
CVP and R atrial pressure are not equal; there has to be a pressure gradient to move from the vena cava to the R atrium
What is the heart valve located between the right atrium and the right ventricle.
The tricuspid valve
What is the sequence of events that causes the tricuspid valve to open?
• The coronary sinus empties deoxygenated
blood from the myocardium to the R atrium
• As volume increases in the R atrium, pressure
increase s/t the volume increase; at this point
tricuspid valve is closed
• At a certain point, R atrial pressure is higher
than the R ventricle pressure; at this point the
tricuspid valve leaflets open d/t the pressure
gradient
What causes the closure of the tricuspid valve?
- Blood moves with the pressure gradient from the R atrium to the R ventricle
- As volume increases, pressure increases, causing the closure of the tricuspid valves
- THE PRESSURE GRADIENT CLOSES THE TRICUSPID VALVE LEAFLETS
What causes the pulmonic valve to open?
• At some point, the R ventricle goes into systole, increasing the pressure even more
• When the R ventricle pressure becomes greater than the pulmonary artery pressure, this opens the pulmonic
valve leaflets and blood is ejected into the pulmonary artery.
What causes the closure of the pulmonic valve?
When the pulmonary artery pressure becomes greater than R ventricle pressure, this closes the pulmonic
valve
Oxygenated blood is delivered to the left side of the heart via?
Blood is then oxygenated and delivered back to the L side of the heart via the pulmonic veins
Are there valves located between pulmonary views and the left atrium?
NOTICE that there are NOT any valves between the pulm veins and the L atrium; blood is continually flowing into the L atrium
What causes the mitral valve to open?
-As volume increases in the L atrium, the pressure increases; this opens the mitral valve s/t the pressure
gradient in the L atrium/ L ventricle
-Blood flows into the L ventricle s/t the pressure gradient; as the volume increases in the L ventricle, so does the pressure
What causes the mitral valve to close?
- Pressure in the L ventricle closes the mitral valve, creating even more pressure in the L ventricle
- The L ventricle eventually goes into systole (which increases the pressure even more)
What causes the aortic valve to open?
- The L ventricle eventually goes into systole (which increases the pressure even more)
- When L ventricle pressure is greater than aortic pressure, this opens the aortic valve
- When the pressure in the aorta is greater than the L ventricle, this closes the aortic valve leaflets
So what is responsible for the opening and closing of all the heart valves?
pressure gradient
The movement of blood from the R
atrium to the R ventricle (with its pressure gradient) thru the tricuspid valve accounts for _____ of the ventricular preload
~75% of preload
At some point, that RA goes into systole which is called _____ _____; that (systole) contributes the final ~25% of ventricular filling
atrial kick; 75% WITH THE PRESSURE GRADIENT; THEN THE LAST 25% FROM ATRIAL SYSTOLE
The strings that are attached to the tricuspid valve are called?
CHORDAE TENDINEAE
What are the function of the CHORDAE TENDINEAE?
-PREVENTS RETROGRADE BLOOD FLOW FROM RV
INTO RA
-The chordae tendineae are attached to papillary muscles; those papillary muscles are continuous with the myocardium of the RV
• Since the papillary muscles are continuous with the
myocardium of the RV; those papillary muscles contract along with the RV
• When they contract, those papillary muscles shorten; and when they shorten that pulls the chordae tendineae downward and tight, which holds the tricuspid valve leaflets closed
• And that prevents retrograde blood flow from RV
into RA
Are there chord tendineae associated with the pulmonic/aortic valves?
No chordae tendineae or papillary muscles
associated with pulmonic or aortic valve leaflets
The left side of the heart is like the right in that pressure gradient is responsible for ____ blood flow while atrial kick is responsible for _____?
L side same as R side: PRESSURE GRADIENT = 75% and ATRIAL SYSTOLE = 25%
What would be the consequences of having an atrial arrhythmia that caused the atria to contract against a
closed valve?
-You would lose that 25% contribution
§ Most people could compensate with a lose of 25% decrease in preload; but if that person were to
exercise, that is when you would see CV manifestations/ complications
What would happen if someone had a MI (transmural infarction) all the way across the myocardium that affected those papillary muscles?
REGURGITATION
§ That’s why people that have had a MI have regurgitation; because those papillary muscles do not function properly
When the LV contracts, that causes the mitral valve leaflets to balloon up and into the LA; that causes a transient increase in ___ ____ ____.
LA pressure
What causes heart sounds?
• Heart sounds are caused when the valve leaflets close
and the blood bounces off the valve leaflets causing
turbulence of the blood flow
• That turbulence of blood flow causes vibrations
which is transmitted to the chest wall
Starting at the left upper as looking at the chest…what is the order of location of heart sounds?
Aortic—>Pulmonic
Tricuspid—->Mitral(bicuspid)
All Puppies Take Mild
What is the anatomic location of the auscultation of the aortic valve?
2nd intercostal space (ICS), R sternal border
How do you find your 2nd intercostal space?
§ Start at the sternal notch til you find the manubrium;
where the manubrium attaches to the sternum is the angle of Louis
§ From the angle of Louis, move your finger over and if your on a rib then move down one;
if you are in an ICS, then that is the 2nd ICS
What is the anatomic location of the auscultation of the pulmonic valve?
2nd ICS, L sternal border
What is the anatomic location of the auscultation of the tricuspid valve?
5th ICS, L sternal border
What is the anatomic location of the auscultation of the bicuspid(mitral) valve?
5th ICS, L midclavicular line
What is the gold standard of diagnosing cardiac valvular disease?
Echocardiography
Diastolic murmurs correlate with what type of valvular disease?
MS ARD:
- Mitral valve stenosis
- Aortic valve regurge
o Tricuspid valve stenosis o Mitral valve stenosis o Aortic valve regurgitation (murmur often not heard during auscultation; loudest point may be aortic area or along lower left sternal border) o Pulmonic valve regurgitation
Systolic murmurs correlate with what type of valvular disease?
MR ASS:
- Mitral valve regurge
- Aortic valve stenosis
o Aortic valve stenosis
o Pulmonic valve stenosis
o Tricuspid valve regurgitation
o Mitral valve regurgitation
What is happening if a murmur is heard during diastole?
o During ventricular diastole, mitral and tricuspid valves should be open
§ SO if the tricuspid valve should be open and we hear a diastolic murmur at the tricuspid valve auscultatory area during ventricular diastole; that would be indicative of a tricuspid valve stenosis.
§ Cause that valve should be open and blood flow should be easy from the atria to the ventricle
§ Same thing with mitral valve stenosis; if we hear a murmur (over the 5th ICS, midclavicular line)
during vent diastole, that would be indicative of a mitral valve stenosis
§ During ventricular diastole, aortic and pulmonic valves should be closed; so if you hear a murmur at the aortic or pulmonic auscultatory area during diastole, that is indicative of an aortic/ pulmonic valve regurgitation or aortic/ pulmonic valve incompetence (you will hear it both ways)
§ Aortic valve regurg is often not heard during auscultation and the loudest point may actually be at
the aortic area or along the lower L sternal border
What is happening if a murmur is heard during systole?
o During systole, the aortic and pulmonic valves should be open.
o If you hear a murmur at the aortic/ pulmonic valve auscultatory area during systole; that would be indicative of aortic/ pulmonic valve stenosis
o Mitral and tricuspid valves should be closed = mitral/ tricuspid regurg
Left main and right coronary arteries branch from the ___ immediately after it exits from the ___ ____.
- aorta
- left ventricle
About ___ of CO circulates through coronary arteries during rest
3%
Most perfusion occurs during ventricular ____.
-diastole
§ When the ventricle goes into systole, that places pressure and compresses against those arteries,
arterioles and capillaries; which prevent perfusion
§ So most perfusion occurs during ventricular diastole; when those muscles are not contracting
What are the sympathetic effects upon coronary blood flow?
- Epi/Norepi
- Alpha
- Beta
Of the sympathetic effects upon coronary blood flow, is alpha or beta usually more dominant and why?
BETA;
§ Many more beta-2 receptors than alpha-1 receptors
§ However, in states of advanced shock, when you have an excessive amount of catecholamines (or an
outpouring of catecholamines) that can cause activation and predomination of the alpha-1 receptors; which would cause coronary artery constriction that would eventually lead to coronary ischemia and myocardial infarction
What are the parasympathetic/vagal effects on coronary blood flow?
Parasympathetic/vagal stimulation ??
o The coronary arteries may or may not, possibly, maybe, but not necessarily, have parasymp stimulation or innervation
o If they do, it would be thru acetylcholine and muscarinic receptors; which would have a mild dilation of the coronary arteries
o Acetylcholine and muscarinic receptors
o Usually minimal effect; mild dilation
CORONARY ARTERY BLOOD FLOW AND MYOCARDIAL PERFUSION CONTROLLED PRIMARILY BY…………?
- CORONARY ARTERY BLOOD FLOW AND MYOCARDIAL PERFUSION CONTROLLED PRIMARILY BY RATE OF MYOCARDIAL O2 CONSUMPTION !!!
- Any condition that increases myocardial O2 consumption causes reflex dilation of coronary arteries.
- Resting state: ~ 75% of O2 extracted from coronary blood flow; A lot greater than other tissue; usually only extract about 25 – 30% of the O2 that passes by those tissues
IF WORK LOAD ON HEART INCREASES, O2 CONSUMPTION ____.
increases
FOR O2 SUPPLY TO MEET O2 DEMAND, CORONARY ARTERIES MUST ___ TO INCREASE BLOOD FLOW AND O2 TO THE CARDIAC TISSUES
dilate; E.G., Increased strength of contraction, increased afterload, increased preload (more blood coming back to
the heart, more stretch on the cardiac fibers, leading to greater strength of contraction/ EF/ CO), and INCREASED HEART RATE
So if you wanted to do one thing for your patients, that would decrease the workload on the heart; what
would you do?
Give them a beta-blocker
What are 4 metabolic processes that cause coronary artery vasodilation?
- increased CO2
- increased H+/decreased pH
- lactate
- adenosine
Why does increased CO2 cause coronary artery vasodilation?
o CO2 is a by-product of metabolism; the more metabolism, more CO2; the more those coronary vessels
need to dilate to deliver O2 to those tissues
o To remove excess CO2 from the tissue spaces
Why does increased H+ ions/decreased pH cause coronary artery vasodilation?
o Maybe an outcome of anaerobic metabolism, so we hope more blood, more O2 will convert it to aerobic
metabolism
o as veins dilate, this removes H+ ions and other acid by-products from the tissue spaces
Why does increased lactate cause coronary artery vasodilation?
o Lactate accumulation: lactate drops the pH down towards the acid side
o Lactate is a by-product of anaerobic metabolism; with a desired effect of more blood, more O2 to convert back to aerobic metabolism
Why does adenosine cause coronary artery vasodilation?
o ATP breaks down to ADP, then to AMP, all the way back down to adenosine
o VERY potent vasodilator of coronary arteries
The right coronary artery (RCA) descends anteriorly in the _____ _____ in between the RA and RV; It continues on around to the posterior side of the heart; toward the middle of the heart and then it descends in the sulcus between the _____ _____ _____.
- coronary sulcus
- L and R ventricle posteriorly
As mentioned earlier, IN MOST PEOPLE, the posterior descending artery (PDA) is a branch of the _____
(~ 85% of people); And about 15% of people, the PDA is a
branch of the _______?
- RCA
- L circumflex
When the PDA is a branch of the RCA, we call that ____ DOMINANT
RCA
When the PDA is a branch of the L circumflex, we call that _____?
L CORONARY ARTERY DOMINANT
The ___ ___ ___ artery perfuses the largest percentage of the myocardium,regardless of R or L coronary artery dominance
Left main coronary (LMC)
The LMC artery branches off the?
aorta
The LMC artery branches into the?
- Left anterior descending (LAD) artery
- Left circumflex artery
What is the location of the LAD?
toward the apex of the heart; that LAD artery is actually sitting right on top of the interventricular septum, between the RV and LV
What is the location of the left circumflex?
Left circumflex artery which goes around the L lateral part of the heart and continues on to the posterior surface of
the heart
Does RCA/LCA dominance have anything to do with amount of blood flow that is delivered to they myocardium?
So when I say that someone is RCA dominant, all that means is the PDA is a branch of the RCA; it has nothing to do with the amount of blood flow that the RCA delivers to the myocardium
LEFT MAIN CORONARY ARTERY PERFUSES LARGEST PERCENTAGE OF MYOCARDIUM REGARDLESS OF RIGHT OR LEFT CORONARY ARTERY DOMINANCE*
What coronary artery perfuses the anterior left ventricle?
LAD along with the left circumflex
What coronary artery perfuses the anterior inter ventricular septum?
LAD
What coronary artery perfuses the right atrium?
RCA
What coronary artery perfuses the left atrium?
Left circumflex
What coronary artery perfuses the anterior right ventricle?
RCA
What coronary artery perfuses the posterior right ventricle?
RCA(PDA)
What coronary artery perfuses the Diaphragmatic(inferior) left ventricle?
Left circumflex and RCA(PDA)
What coronary artery perfuses the anterior left ventricle?
Left anterior descending and left circumflex
What coronary artery perfuses the lateral left ventricle?
left circumflex
What coronary artery perfuses the apex of the left ventricle?
LAD
What coronary artery perfuses the anterior inter ventricular septum?
LAD
What coronary artery perfuses the posterior inter ventricular septum?
RCA(PDA)
What coronary artery perfuses the anterior left ventricular papillary muscles?
LAD and the Left circumflex
What coronary artery perfuses the posterior left ventricular papillary muscles?
Left circumflex and RCA(PDA)
What coronary artery perfuses the SA node?
RCA
What coronary artery perfuses the atrial internal pathways?
RCA
What coronary artery perfuses the AV node?
RCA
What coronary artery perfuses the bundle of His?
RCA
What coronary artery perfuses the right bundle branch?
LAD
What coronary artery perfuses the anterior left bundle branch?
LAD
What coronary artery perfuses the posterior left bundle branch?
LAD
Atrial and ventricular muscle fibers are ___ ___ fibers?
mechanical contractile
fibers
What are the characteristics of the electrical fibers of the heart?
o Form electrical conduction system through heart
o Initiate and conduct action potentials through heart and to mechanical contractile fibers
o Action potentials transferred to contractile fibers and coupled with mechanical contraction
o Electrical impulses (action potential) MUST precede mechanical contraction
§ e.g., PEA
Are the contractile fibers of the heart smooth or striated?
striated
What is the ratio of actin to myosin in the contractile fibers of the heart?
2:1
What cardiac fibers contain tropomyosin and troponin?
Cardiac contractile fibers
In contractile cardiac fibers, what does troponin I attach to?
attached to actin myofilaments
In contractile cardiac fibers, what does troponin T attach to?
attached to the tropomyosin
In contractile cardiac fibers, what does troponin C attach to?
strongly attached to calcium ions
In what way is Intercalated disks and gap junctions in cardiac muscle fibers different that in skeletal muscles?
Different from skeletal muscle fibers, cardiac contractile fibers have these intercalated disks between adjacent cardiac contractile fibers that form gap junctions
§ These gap junctions allow for free flow of ions from muscle fiber to adjacent muscle fiber or from sarcolemma to adjacent sarcolemma; which allows for the spread of AP directly from muscle fiber to muscle fiber
v remember with skeletal muscle, each muscle fiber had to be innervated by a collateral of a somatic motor neuron
v cardiac muscle fiber does not because of the intercalated disk and gap junctions that allow for free flow of ions; which allow AP to spread from muscle fiber to muscle fiber, so all those muscle fibers from within a unit will depolarize and contract at about the same time
What are the units within the the heart called that are composed of intercalated disk and gap junctions that allow for the free flow of ions which allow AP to spread from muscle fiber to muscle fiber?
v Those units within the heart are called functional syncytium; there are two functional syncytia
What is the name of the two functional syncytia?
atrial syncytium (R & L) and ventricular syncytium (R & L)
What are the characteristics of the two functional syncytial?
§ Right and left atria
§ Right and left ventricles
§ Separation of atria and ventricles by fibrous tissue with openings for valves and pathway for electrical fibers so impulse can be conducted from atria to ventricles
§ So if they are syncytium, that means that they are a unit and that all of the muscle fibers within that unit become excited and contract at about the exact same time; that allows for more efficient ejection of blood
§ If those muscle fibers were all contracting at different times, that would not be synchronous and would not be conducive to an effective EF, SV, CO.
List the 7 steps of cardiac muscle fiber contraction pathway
- AP conducted along the muscle fiber
- AP goes down the T-Tubule
- Sitting adjacent to the T-tubule is the terminal cisterna of the sarcoplasmic reticulum; when that AP gets there, that excites the sarcoplasmic reticulum allowing for opening of voltage-gated Ca++ channels
- Then release of Ca++ from the sarcoplasmic reticulum into the sarcoplasm
- Ca++ from the EC fluid increases the sarcoplasmic
Ca++ concentrations - that interacts with troponin C which pulls troponin T and tropomyosin away from the actin binding sites
- Myosin heads can then power-stroke, crossbridge,
and shorten the sarcomere; which shortens the muscle fiber
In the heart, the sarcoplasmic reticulum is not as developed as in the skeletal muscle fibers; so we
have to have an extra source of ____?
Where does this extra source come from?
- Ca++
- extracellular fluid
What are the two sources of Ca++ that is needed for the cardiac contraction cycle?
- sarcoplasm reticulum
- EC
Changes in the EC fluid would have major implications on cardiac contractility