The Heart and Cardiac Cycle Flashcards
What are the four chambers of the human heart?
- right atrium
- right ventricle
- left atrium
- left ventricle
What is a cardiac cycle?
The complete cycle of events in the heart that corresponds to one heartbeat
What is a heartbeat?
A heartbeat follows one volume of deoxygenated blood as it enters the heart until it exits as oxygenated blood
Diastole definition
period of ventricular relaxation and filling the heart with blood
Systole definition
period of contricular contraction and emptying the heart of blood into the arteries
How is the heart regulated?
Internally with the heart without the need of the nervous system
What is a myogenic muscle?
muscles that can contract and relax without input from an external source
What is a pacemaker:
an electrical device that initiates a heartbeat and sets a normal rhythm
What is the sinoatrial node? Where is it? What does it do?
It is in the upper wall of the right atrium near the opening to the superior vena cava. It causes the atria to contract
Where is the atrioventricular node? Where is it?
It is in the lower part of the right atrium, near the AV valves. It acuses the ventricles to contract
What is the first step in a heartbeat?
*SA node initiates an impulse
*Impulse flows over the two upper chambers of the
heart (atria)
* Causes contraction of both atria simultaneously
(systole)
* Blood rushes into the lower chambers (ventricles)
* Tricuspid and bicuspid (AV) valves are open during this
step
What is step 3 in a heartbeat?
A bit of delay between contractions as the electrical
impulse travels to the atrioventricular (AV) node
What is step 3 in a heartbeat?
- AV nodes sends impulse:
- Down the septum
- Into the left and right bundle branches surrounding the
ventricles - Into Purkinje fibres
- Causes synchronized contractions of both ventricles
starting at the bottom, moving upward - Pressure opens both pulmonary and aortic semilunar
valves - Blood forced out of the ventricles to arteries (pulmonary
and aorta)
What is step 4 in a heartbeat?
- All chambers relaxed
- Blood passively flows into both atria
What is step 5 in a heartbeat?
- All chambers still relaxed
- AV valves open
- Blood can now passively flow into atria and ventricles
What is an electrocardiograph? (ECG)
a device that measure the electrical signals of the heart
What does an ECG record data on?
An electrocardiogram
What are the three parts of an ECG summary?
P, Q, R, S, T
What happens on the P wave of an ECG?
the SA node sends depolarization signal to atria
- atria depolarize
- the atria contracts (ventricles relax)
- signal travels to AV nodes
What happens on the QRA complex of an ECG?
- AV node sends depolarization signal down septum around ventricles
- ventricles depolarize
- the ventricles contract - atria repolarize (atria relaxes)
What happens on the T of an ECG summary?
- recovery period
- membranes repolarizes
- ventricles relax
- atria remains relaxed
QRS is both depolarization and repolarization but unable to differentiate signlas because the atria repolarizing is a smaller signal
What sound does the heart make?
a lub-dub osunds as blood flows through the heart and valves close behind it
What happens on the lub souds that the heart makes?
- SA node (pacemaker) impulse
- Right and left atria contract
- Right and left ventricles relax
- Blood is pumped to the ventricles
- Tricuspid and bicuspid AV valves close
What happens on the dub sound of the heart
- AV node impulse
- Left and right ventricles contract
- Left and right atria relax
- Blood is pumped to pulmonary artery and aorta
- Pulmonary and aortic semilunar valves close
What are the health measurements of the heart?
- blood pressure
- heart rate (maximum and resting)
- stroke volume
- cardiac output
What is blood pressure (BP)
a measure of force of blood in arterial wall
What are the two types of blood pressure?
- systolic pressure
- diastolic pressure
What is systolic pressure?
- force of blood against arterial walls during contraction of the left ventricle
- highest pressure
What is diastolic pressure?
force of blood against arterial walls immediately before the next ventricular contraction
How is blood pressure given?
sysolic/diastolic pressure
What is a normal blood pressure considered?
below 120/80
pressure is inversely proportional to area
What is the relationship between blood pressure and distance from the heart?
Blood pressure declines with distance from heart
Why do arteries have higher bp than veins?
they are closer to the heart
Which artery has the highest BP?
the aorta
Capillaries have low BP. Why?
many have small circumference but the number of capillaries significantly increase the total area
Veins have the lowest BP. Why?
- large circumference
- further from the heart
Which vein has the lowest blood pressure?
the vena cavae
What are the effects of low blood pressure?
- reduces the capacity to transport blood
- they are felt when not enough blood is transported the the brain
- light-headedness
What are the effects of high blood pressure?
can weaken and rupture the arterial walls
What is heart rate?
- frequency of the cardiac cycle
- contraction of the heart within a given amount of time
What is resting heartrate?
- lowest heart rate when a rest
what is a normal level for a resting heart rate?
60-100 beats/min
What is maximum heart rate?
hgihest heart rate attainable when exerting maximum physical effort (diminiches with age)
What is stroke volume?
volume of blood pumped from the heart with each ventricular contraction
What is a normal level for stroke colume?
70 mL/beat
What factors can affect stroke volume?
*Distensibility of ventricular wall
* The stretchiness of the heart muscles
* Affects how easily the heart fills with blood
* Strength of ventricular wall
* Affects the strength of each contraction
* Size of ventricles
* Affects the maximum amount of blood that can be held
and thus pumped
What is cardiac output (Q)?
- a measure of the volume of blood pumped from each ventricle per unit of time.
- heart rate and stroke volume affect cardiac output
What is a normal cardiac output?
5 mL/min
What is the cardiac output formula?
Q = SV * HR
SV = stroke volume
HR = heart rate
