L17: Cardiovascular System II Flashcards
different types of heart cells
express unique combination of ion channels and thus have different action potential shapes
first depolarization
rapid depolarization due Na+ inflow when voltage-gated fast Na+ channels open
then cells maintain depolarization
due
slow Ca2+ inflow when voltage-gated slow Ca2+ channels open and K+ inflow when some K+ channels open
repolarization due to
closure of Ca2+ channels and K+ outflow when additional voltage-gated K+ channels open
SA node cells are responsible for
autorhythmicity of the heart
SA node cells do not have
steady resting potentials
SA node cells are able to
spontaneously generate their own action potentials
SA node cells have unique channels
open when the membrane potential is at negative values
SA node unique channels are called
funny type channels
funny type channels
non-selective cation channels and conduct an inward, depolarizing Na+ current
ECG represents
the summed electrical activity of all cells recorded from the surface of the body
ECG is used
to evaluate the electrical events within the heart because salt solutions are good conductors
ECG gets
summed electrical activity generated by all cells of the heart
ECG device measures
potential differences between selected electrodes
each electrode pair constitutes
one positive and one negative electrode
ECG has __ leads and is recorded using various combinations of the __ electrodes and another __ electrodes on the chest and trunk
12, 3 limb, 6
lead 1
negative –attached to the right arm;
positive – attached to the left arm
three major waves on a normal ECG
the P wave, QRS complex, and the T wave
the first wave __ corresponds to ___
P wave, depolarization on the atria
the next trio of waves ____ represents ____
QRS complex, the progressive wave of ventricular depolarization
the final wave __ represents ____
T wave, repolarization of the ventricles
4 major questions when interpreting ECG
- what is the heart rate?
- is the rhythm of the heartbeat regular?
- are all the waves present in recognizable form?
- is there one QRS complex for each P wave? If yes, is the P-R segment constant in length?
heart rate is timed
from the beginning of one P-wave to the beginning of the next P-wave
normal resting heart-rate
60-100 beats per minute (bpm)
trained athletes typically have ___ heart rates
lower
tachycardia
faster-than-normal heart rate
bradycardia
slower-than-normal heart rate
arrhythmia results from
a benign extra beat or atrial fibrillation
ventricular tachycardia
rapid heart-beat that starts in the ventricles that can occur as a result of heart-attack
if there are P waves without initiating a QRS complex
heart block, action potentials from the SA node can fail to be transmitted through the AV node to the ventricles
systole
ventricular contraction phase involving blood ejection from the heart
diastole
ventricular relaxation involving blood injection into the heart
systole is subdivided into 2 periods
isovolumetric ventricular contraction and ventricular ejection
isovolumetric ventricular contraction
ventricles contracting but all valves are closed, no blood ejected, ventricular volume is constant, raising ventricular blood pressure
ventricular ejection
semilunar valves are open, blood is forced into aorta and pulmonary artery, the blood volume ejected = the stroke volume (SV)
diastole periods
isovolumetric ventricular relaxation, ventricular filling
isovolumetric ventricular relaxation
valves are closed, volume is not changing
ventricular filling
the AV valves are open and blood flows in from the atria, atrial contraction occurs at the end of diastole, 80% of filling occurs before atrial contraction
left ventricular pressure changes
in mid-diastole, ventricular pressure remains low until atrial contraction;
in systole, a large increase in ventricular pressure;
in early diastole, ventricular pressure falls to near zero (relaxation), and then slowly creeps back by passively filling with blood
aortic pressure changes in diastole
no blood enters the aorta, semilunar valve is closed, blood leaves the aorta downstream, causing a slow decline in aortic pressure
diastolic pressure
minimal aortic pressure at the end of the diastole and decline
aortic pressure in systole
the semilunar valve opens and the aortic pressure rises quickly, blood flows more quickly into the aorta then it moves out
maximal aortic pressure
systolic pressure
aortic pressure at the end of systole
the semilunar valve closes, which causes a transient increase in aortic pressure called the dicrotic notch
stroke volume
volume of blood ejected by the ventricle each beat
end-diastolic volume (EDV)
volume of blood in ventricle reached just before the start of ejection (at the end of diastole)
end systolic volume (ESV)
volume of blood in ventricle following ejection (at the end of systole)
left ventricular volume relationship formula
Stroke volume = End Diastolic Volume - End Systolic Volume
heart sounds result from
turbulent blood flow generated by valve closing
first heart sound
AV valves close simulataneously
second heart sound
semilunar valves close simultaneously
abnormal heart sounds
heart murmurs
most causes of heart murmurs in adults
valve problems
stenotic valve
stiff, narrowed valve that does not open completely (aortic stenosis)
incompetent valve
blood flows backward through the insufficient valve and collides with blood moving forward creating a “swishing” murmur (aortic regurgitation)
