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Cardiovascular (Conducting system of the heart & Electrical events …
Cardiovascular
Conducting system of the heart
& Electrical events
of muscle cardiac cell
-Sinoatrial node and atrial myocardium
The action potential is generated at the SA node
It spreads via gap junctions between cardiac muscle cells throughout the atria to the atrioventricular AV node
RMP= -60 mV; -40 mV is the threshold value
The flow of NA+ from the slow voltage gated Na+ channels
Atrioventricular AV node
The action potential is delayed at the AV node
" bottle neck effect "
this allows the atria to completely finish contracting and force blood into the ventricles to complete ventricular filling
Bundle branches and perkinje fibers
the action potential spreads from the AV node to the bundle of his and the perkinje fibers
the impulse come down the apex of the heart and then come up through the left and right side of the hearts wall
Ventricular myocardium
the action potential is then spread to ventricular muscle cells
This occurs by gap junctions that allow almost simultaneous stimulation of the muscle cells in the ventricular wall
Depolarization
An action potential transmitted through the conducting system via gap junctions
Triggers the opening of the voltage gated NA+ channels in the sarcolemma
Sodium ions enter the cardiac cell causing depolarization
The resting membrane potential changes from -90 mV to -30 mV; then the channels close
Plateau
Depolarization triggers the opening of voltage gated K+ channels that leave the cardiac muscle cell
Almost immediately slow voltage CA2+ enters from the interstinal fluid into the cardiac muscle cells
This results in no electrical charge and remains in the depolarize state
Re polarization
Voltage gated CA2+ channels then close and K+ channels remain open to complete repolarization as K+ exits the cardiac cell
The membrane potential reverses,and the resting potential of -90mV is reestablished
Cardiac Cycle
Atrial Contraction and ventricular filling
Atrial depolarization (p wave in ECG) triggers --->
Atrial contraction ; ventricles are relaxed to receive the blood ;AV valves are opened and the semilunar valves are closed.
ventricular pressure is less than the atrial pressure and the arterial trunk pressure
ventricular blood volume increases slightly
Isovolumetric Contraction
Ventricular depolarization ( QRS )wave in ECG
Ventricular contraction ; atria is relaxed and both the AV valves and SLV are closed
Ventricular pressure is greater than the atrial pressure and its less than the arterial truck pressure or aorta pressure
ventricular volume remains the same ( isovolumetric)
Ventricular Ejection
Ventricular plateau and repolarization
ventricles contracting ;atria are relaxed; AV valves remain closed and SLV open
Ventricular blood pressure increase than the atrial and pressure in the aorta
Ventricular blood decreases as the blood is being ejected
Isovolumetric Relaxation
Ventricles complete repolarixation and then no electrical activity
Ventricles are relaxed and atria also relaxes; both the AV valves and the SLV stay closed.
ventricular pressure is greater than the atrial pressure and its less than the aorta pressure.
ventricular volume remains the same.
Atrial Relaxation and Ventricular Filling
no electrical activity
Ventricles relaxing and atria is relaxed; AV valves open and the SLV close.
ventricular pressure is less than the atrial pressure and less than the aorta pressure
Ventricular volume increases as it exits the atrium
ECG and Terms
Systole
to contract or depolarization
ESV
=end systolic volume
the amount of blood left in the ventricle after it has contracted
the ventricular greater pressure is greater than the aorta/ pulmonary trunk
Diastole
to die= relax
(EDV)=End diastole
when the ventricle receives its maximum blood from the atria.
The AV valve is open and the SLV is closed
Stroke Volume (SV)
The amount of blood pumped out during ventricular contraction
ventricular ejection
ECG
P
the depolarization or contacting of the atria
The SA node or the pace maker
Atrial contraction and ventricular filling step 1
P-Q
segment
is associated with the atrial plateau
when muscles of the atria are contracting
part of the first part of the cardiac cycle
QRS
usually last 0.06- 0.1 second
ventricular depolarization
simultaneously atria re-polarization occurs
The ventricular ejection
S-T segment
The ventricular Plateau when the cardiac muscle cells within the ventricles are contracting
Part of the ventricular ejection; when at T i will relax
T
The polarization of the ventricle; relaxing
The Isovolumetric relaxation in the cardiac cycle
Heart Anatomy
Characteristics of the Pericardium
Fibrous pericardium
composed of dense irregular connective tissue; encloses the heart- protects
Parietal layer of pericardium
composed of simple squamous epithelium;adheres to the inner surface of the fibrous pericardium
Visceral layer of pericardium
also called epicardium and also composed of simple squamous epithelium;adheres directly to the heart.
The two serosal layers are separated by the pericardial cavity which provides lubrication to decrease friction when the heart beats
Layers of the Heart wall
Epicardium
outermost layer also called visceral layer
as we age it thickens as it becomes more invested with adipose connective tissue
Myocardium
The middle layer; the thickest as well.
Th muscle generates the force necessary to pump blood
Endocardium
internal surface of the heart ; which lines the blood vessels
Heart
Right
receives deoxygenated blood from the bodyand pumps it to the lungs
pulmonary trunk ---> into pulmonary arteries
Lung capillary for gas exchange * now with oxygen
Pulmonary circulation
Left
Receives oxygenated blood from the lungs and pumps it to the body
Pulmonary veins bring blood into the left atria
The blood awaits for the atria relaxation and starts to open the left AV valve to start filling the ventricle.
The ventricle is full and then ejects the blood to the aorta to deliver blood to the systemic cells
systemic circulation
Valves
right side of heart
right Aventricular valve (AV) or tricuspid
prevents back flow from the ventricle to the atria
The pulmonary semilunar valve
prevents back flow from the pulmonary trunk to the right ventricle
Left side of the heart
Left AV VALVE = BICUSPID= Mitral valve
prevents back flow from the ventricle back to the atria
Aortic semilunar valve
prevents back flow from the aorta back into the left ventricle.
Arteries
Carry blood away from the heart in major circulation
in the coronary artery they bring oxygenated blood to the heart
Veins
Carry blood towards the heart in major circulation
In coronary veins they carry deoxygenated blood to the right side of the heart
