Cardiovascular Flashcards
Liters of blood the heart pumps
5-6 per minute
List the two functions of the cardiovascular system.
- Muscular pump for blood circulation
2. Endocrine functions
What are the two natriuretic peptides?
- Atrial Natriuretic Peptide
2. B-Type Natriuretic Peptide
What does B-Type natriuretic peptide respond to?
Overstretched ventricles
What does atrial natriuretic peptide respond to?
Increased atrial pressure
Cardiac muscle is involuntary with ________ striations.
cross
What are the individual cardiac cells connected by?
intercalated discs
What is the purpose of intercalated discs?
cell adhesion and allow the heart to contract in synchrony as one unit (syncytium)
Where are gap junctions located?
In the intercalated discs
What is the purpose of gap junctions?
Allow passage of ions between the myocytes which ultimately all the action potentials to spread between cardiac myocytes
In a resting state, there is more ____ and ____ outside the cell and more _____ inside the cell.
Na +, Ca ++ outside the cell and more K+ inside the cell
Explain Phase 0 of the cardiac muscle contraction.
Na + influxes into the cardiac myocyte causing rapid DEPOLARIZATION
Explain Phase 1 of the cardiac muscle contraction.
Inactivation of the Na+ influx with K+ efflux= INITIAL REPOLARIZATION
Explain Phase 2 of the cardiac muscle contraction.
Ca ++ influx through L-type Ca++ channels= PLATEAU PHASE
Explain Phase 3 of the cardiac muscle contraction.
Inactivation of Ca++ influx with continuation of K+ efflux= REST OF REPOLARIZATION
Explain Phase 4 of the cardiac muscle contraction.
Removal of excess Na+ and Ca+ with restoration of the membrane potential using the Na+/K+ ATPase pump to push back Na+ out and bring K+ back into the cell
What determines the force of contraction of the myocardial cell?
The amount of intracellular calcium
What is the Absolute Refractory Period?
No action potential can be initiated regardless of the stimulus strength because the Na channels are closed in Phase 1 though mid Phase 3
What is the Relative Refractory Period?
An action potential can be elicited, however a greater stimulus is needed- extends between mid Phase 3 to the start of Phase 4
What is the Effective Refractory Period?
From Phase 1 to just beyond mid Phase 3
Why is cardiac muscle incapable of sustained contraction aka tetany in comparison to skeletal muscle?
Because of the relatively long refractory period
This law states: cardiac output is directly proportional to the venous return.
Frank-Starling Law
What is stroke volume?
force of contraction of a myocardial fiber
What is end diastolic volume?
length of the myocardial fiber
What is venous return?
amount of blood entering the heart during diastole
What is cardiac output?
volume of ejected blood from the heart per minute
Explain the premise of Frank-Starling Law.
The force of the contraction of a myocardial fiber (SV) is proportional to the length of the myocardial fiber (equivalent to EDV)
The greater the amount of blood entering the heart during diastole (venous return), the greater the stretching of the cardiac myocytes
A greater stretch results in a greater force of contraction causing an increase in the cardiac output (volume of ejected blood from the heart per minute)
What makes up the 1st heart sound?
The closure of the tricuspid and mitral valves
What sound does the 1st heart sound make?
LUB
What makes up the 2nd heart sound?
The closure of the pulmonary and the aortic valves
What sound does the 2nd heart sound make?
DUB
What sound does the 3rd heart sound make?
DUBup
When do you hear the 3rd heart sound?
after the 2nd heart sound and is seen in congestive heart failure
What sound does the 4th heart sound make?
beLUB
When do you hear the 4th heart sound?
before the 1st heart sound and is seen in hypertrophic ventricles
When does systole occur?
Between heart sounds 1 and 2
When does diastole occur?
Between heart sounds 2 and 1
Is systole contraction or relaxation?
Contraction
Is diastole contraction or relaxation?
Relaxation
What does the electrocardiogram do?
It is a reflection of the electrical activity in the heart as the impulse generated in the SA node is propagated to the rest of the heart