The Cardiovascular System Flashcards
Location of the heart
> largest organ of the mediastinum
- located between the lungs
Where is the apex located
Apex lies to the left of the midline
Where is the base located
Base is the broad posterior surface
What are the functions of the heart
> Generating blood pressure
Routing blood
- hearts separates pulmonary and systemic circulation
- ensuring one -way blood flow
changes in contraction rate and force match blood delivery to changing metabolic needs
Layers of the heart wall
Pericardium, epicardium, myocardium, endocardium
Pericardium has two primary layers
Fibrous pericardium ( strong & dense CT) & Serous pericardium ( parietal pericardium & visceral pericardium)
Epicardium
> most superficial layer
> visceral layer of the serous pericardium
Myocardium
> middle layer
consists of cardiac muscle
arranged in circular and spiral pattern
Endocardium
> deepest layer
endothelium resting on layer of CT
lines the internal walls of heart
aka the visceral pericardium
Cardiac muscle tissues
> forms a thick layer of myocardium
- started, like skeletal muscle
- contractions pump blood through the heart and into blood vessels
- contract sliding filament mechanism
Cardiac muscle fibers
> short, branching, with one or two nuclei
cells join at intercalated discs
- connect one cell to the next
- support synchronized contraction of cardiac tissue
cells are separated by delicate endomysium
- binds adjacent cardiac fibers
- contains blood vessels and nerves
Atria
> Thin, upper chambers that receive blood
- capped by auricles that serve as blood reservoirs
Ventricles
Thick , lower chambers that pump blood
Interventricular septum
Wall separating left and right sides of heart
Right atrium
> receives oxygen poor blood from superior and inferior vena cava
pumps blood to right ventricle through tricuspid valve
fossa ovalis - a depression in interatrial septum; a remnant of foramen ovals (fetal heart)
Right ventricle
> pumps blood into pulmonary circuit via pulmonary trunk
> pulmonary semilunar valve - located at opening of right ventricle and pulmonary trunk
Left atrium
> makes up hearts posterior surface
receives oxygen-rich blood from lungs through pulmonary veins
opens into the left ventricle through mitral valve (bicuspid valve)
Left ventricle
> forms apex of the heart
three times thicker than right ventricle
pumps blood into systemic circuit via aortic semilunar valve (aortic valve )
Draw the blood flow through the heart
Superior & inferior vena cava - > right atrium -> right Av valve -> right ventricle -> pulmonary semilunar valve-> pulmonary trunk -> pulmonary arteries-> Lungs -> pulmonary veins - > left atrium-> left av valve -> left ventricle-> aortic semilunar valve -> body tissues
Internal walls of ventricles
> papillary muscles-
- attach to mitral and tricuspid valves’ chordae tendineae
- contract to prevent inversion of valves beyond point of closure
> Chordae tendineae - cord -like tendons that connect the papillary muscles to the mitral and tricuspid valves
Heart valves
- valves within the heart
- regulate blood flow based on blood pressure
- composed of endocardium with CT core
Atrioventricular (av) valves
- between atria and ventricles
- mitral ( bicuspid) and tricuspid
Aortic and pulmonary valves
- cusps (flaps) are semilunar in shape
- at junction of ventricles and great arteries ( pulmonary and arteries )
Coronary arteries
- left and right coronary arteries
- two main arteries that branch into smaller coronary arteries
- originate from left side of heart, at Root of the aorta
- Delivery oxygen rich blood to cardiac muscle
Cardiac veins
> cardiac veins - drain blood into the coronary sinus
> coronary sinus - delivers deoxygenated blood to the right atrium
Cardiac histology
> intercalated discs allow Branching of the myocardium
gap junctions ( instead of synapses) fast cell to cell signals
many mitochondria
large T-tubes
Electrical activity of Heart
> Heart beats rhythmically as result of action potentials it generates by itself (autorhythmicity)
> two specialized types of cardiac muscles cells
- contractile cells
- 99% of cardiac muscle cells
- do mechanical work of pumping
- normally do not initiate own action potentials
- autorhythmic cells
- do not contract
- specialized for initiating & conducting AP’s responsible for contraction of working cells
Which cardiac cells creates its own action potentials ?
Autorhythmic cells / HR
Which cardiac muscle cells does the contraction and the relaxation ?
Contractile cells / Stroke volume
The intercalated disks contain desmosomes that transfer what ?
Force
The intercalated disks also contains gap junction that transfer what ?
Electrical signals
Draw a flow chart of the conduction pathway
Conduction pathway
Atria contracts as SINGLE unit, followed by (after a brief delay) a synchronized ventricular contraction
Intrinsic conduction system
> SA node ( 70-80 bpm)
- sets the pace of the heart beat
> AV node (40-60 bpm)
- delays the transmission of AP’s
> Purkinje fibers (20-30bpm)
- can act as pacemakers under some conditions
Pacemaker potential
> Autorhythmic cells have “ drifting” resting potentials called pacemaker
- membrane slowly depolarizes “drifts” to threshold, initiates AP, membrane repolarizes to -60 mv.
- use calcium influx (rather than sodium ) for rising phase of the action potential
Draw the autorhythmic cells graph with all the channels.
Write a flowchart of the Autorhythmic AP
0- resting membrane potential
1- funny channels open ( Na + influx)
2- funny channels close, t-type ca^2+ channels open ( ca^2+ influx) ( slowly depolarizing)
3-T-type ca^2+ channels close, Hits threshold, L-type ca^2+ channel opens (ca^2+ influx (rapid) )
4- L-type ca^2+ channels close, VG K+ channels open (K+ efflux)
Action potential of contractile cell
> contractile cells
- rapid depolarization due to Na+ influx
- Rapid, parietal early repolarization, prolonged period of slow repolarization which is plateau phase
- Rapid final repolarization phase
> AP’s of cardiac contractile cells exhibit prolonged positive phase (plateau) accompanied by prolonged period of contraction
- ensures adequate ejection time
- plateau primarily due to activation of slow L-type ca^2+ channels
Draw the Action potential in contractile cells graph
Draw the flowchart of the AP of contractile cells
0- RMP
1- AP from autorhythmic
2- @ threshold, Activate VG-Na+ channel ( Na+ influx)
3- VG-Na+ channel closes, Activate VG-K+ channels (t-type) ( K+ efflux)
4- VG K+ channels (t-type) close, L-type ca^2+ channel opens ( Ca^2+ influx)
5- L-type close & VG- K+ channel open ( K+ efflux)
Action potentials : Autorhythmic vs. Contractile cell
Write down the Comparison of : autorhythmic myocardium & Contractile myocardium
Write down the flowchart of the Excitation-contraction coupling in cardiac contraction cells
Electrocardiography (ECG) ECG= EKG
> record of overall spread of electrical activity through heart
- Not direct recording of actual electrical activity
- Not a according of a single action potential in a single cell at a singe point in time
- Comparisons in voltage detected by electrodes at two different points on body surface, not the actual potential
- Does not record potential at all when ventricular muscle is ether completely depolarized or completely repolarized
***** basically EKG is a representation of the sum of all of the heart activity !!!!!!
Cardiac cycle
- Autorhythmic cells —-> AP
- p wave : Atrial depolarization
- PR segment : Av nodal delay / Atriole systole
- QRS complex : ventricular depolarization / atria repolarization
- ST segment : ventricular systole
- T wave : ventricular repolarization
- TP segment : Diastole , fills with blood
What are some of the abnormalities that interpreted from ECGs
Extrasystole,Ventricular fibrillation, Complete heart block, Myocardial infraction
Extrasystole
Extra beats that occur when autorhythmic cell other than SA node fires out of sequence
Ventricular fibrillation
Electrical activity becomes disordered and ventricles contract in an unsynchronized way. No blood is pumped, cardiac arrest follows.
Complete heart block
No conduction through AV node, atria and ventricles contract out of sync
Myocardial infarction
Death to myocardial tissue due to blockage of coronary artery.
In other words “ Heart Attack “
What’s ectopic focus ?
.
Cardiac cycle -filling of heart chambers
> heart is two pumps that work together, right and left half
Repetitive contraction ( systole) & relaxation (diastole) of heart chambers
blood moves through circulatory system from areas of higher to lower pressure
- contraction of ventricle produces the pressure
Write a flow chart of the “Cardiac cycle -mechanical events “
1– late diastole : both sets of chambers are relaxed and ventricle fill passively
2- atrial systole : atrial contraction forces a small amount of additional blood into ventricles
3- isovolumic ventricular contraction: first phase of ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves
4- ventricular ejection: as ventricular pressure rises and exceeds pressure in the arteries, the semilunar valves open and blood is ejected
5- isovolumic ventricular relaxation: as ventricle relax, pressure in ventricles falls, blood flows back into cups of semilunar valves and snaps them closed
2 phase of ventricular systole:
> isovolumic ( isovolumetric ) contraction phase :
- first phase of ventricular contraction
- Ventricles begin to contract , pushing AV valves close, SL valves still closed, pressure in ventricles rises
- pressure in ventricles is not enough to open semilunar valves
- therefore, all four valves are closed !!!!!!
> ventricular ejection phases :
- second phase of ventricular contraction
- ventricular pressure rises and exceeds pressure in the Arteries, the semilunar valves open and blood is ejected
Label the wiggers Diagram
Heart sounds
> first heart sound or “lubb”
- av valves close and surrounding fluid vibration at systole
- Av valves snap shut at start of ventricular systole “lubb”
> second heart sound or “dupp”
- results from closure of aortic and pulmonary semilunar valves at diastole, lasts longer
- semilunar valves snap shut at start of ventricular diastole “dupp”
What does systole mean ?
The heart contract, blood pressure rises and blood moves out along the vessels
What does diastole means ?
The heart relaxes
Left ventricular volume
> EDV = ~ 135 ml
End Diastolic volume- the amount of blood in a ventricle just before ventricular ejection
* the ventricles are fully relaxed and at their most full
> ESV = ~65ml
End systolic volume - the amount of blood remaining in a ventricle after full ventricular ejection
* the ventricles are fully contracted and at their most empty
Stroke volume
The volume of blood pumped from one ventricle of the heart with each beat ~70ml
- ml/ beat
Heart Rate
- beats / min
SV = _____ - _______
EDV & ESV
Ejection fraction formula
Stroke volume / EDV = %
Cardiac output
> Cardiac output (CO) is the amount of blood pumped by each ventricle in one minute
> CO is the product of the HR and SV
> CO= HR X SV
Cardiac reserve
Is the difference between resting and maximal CO
Calculating cardiac reserve
> (Maximal cardiac output) can be 4-5 times greater than resting cardiac output (in non athletes)
* if an average resting CO is 5 L/m, then the expected ranged for max CO is 20-25 L/min during intense exercise
> cardiac reserve is the difference between resting and maximum CO:
- 20-25L/min - 5L/min= 15-20 L/ min
- The individuals heart can pump 15-20 L/min more than is required for normal circumstances, that’s 300-400%
> A trained athletes heart has a greater stroke volume, therefore needs to pump less frequently both at rest and during exercise. Their max heart rate would be substantially lower than the average person
Factors affecting Cardio output
> HR
- Autonomic innervation
- Hormones- Epi, NE, and thyroid hormone (T3)
- cardiac reflexes
> SV
- starling law
- venous return
- cardiac reflexes
