Physiology Flashcards
The apex of the heart lies just above the _______ left of the __________.
The base of the hear lies at approx the level of the _______ rib
diaphragm, midline
second rib
What are the 3 layers of the heart? Describe each layer.
Endocardium- Innermost, lines hearts chambers
Myocardium - Thick middle layer, cells conduct electricity of the heart
Pericarium - Protective sac surrounding heart, has 2 layers (visceral pericardium - in contact with heart muscle and the parietal pericardium - outer fibrous later)
Name the 2 superior chambers of the heart and their function
Atria - receive incoming blood
They are separated by the interatrial septum
Name the 2 inferior chambers of the heart and their function
Ventricles - pump blood to the body
Separated by the interventricular septum
Atrioventricular valves
tricuspid - right heart
mitral (bicuspid) - left heart
Semilunar valves
left semilunar valve - also known as the aortic valve, connects the L ventricle to the aorta
right semilunar valve - also known as the pulmonic valve, connects the R ventricle to the pulmonary artery
What is the only artery in the body that carries deoxygenated blood?
Pulmonary
What are the only veins to carry oxygenated blood in the body?
Pulmonary
The heart receives its blood supply from which arteries?
Coronary
The left coronary artery supplies what?
Two major branches?
Left ventricle, interventricular septum, part of the right ventricle, and the hearts conducting system.
Two branches: anterior descending artery and circumflex artery
The right coronary artery supplies what?
Two major branches?
A portion of the right atrium and right ventricle, and part of the conduction system.
Two branches: posterior descending artery and the marginal artery
Blood drains from the left coronary system via what veins
Anterior great cardiac vein and the lateral marginal sinus. These empty into the coronary sinus.
Blood drains from the right coronary vein directly into the ____________ via smaller cardiac veins
right atrium
Diastole: what phase is it, what happens during
1st phase, relaxation phase
Ventricular filling happens
Blood enters ventricles through the mitral and tricuspid valves. Pulmonic and aortic valves are closed.
Systole: what phase is it, what happens during
2nd phase, heart contracts.
Atria (quickly) first to finish emptying into ventricles. Atrial kick boots cardiac output.
Ventricles second, pour blood into the pulmonic and aortic arteries
What is the ejection fraction?
Fraction of blood ejected from the ventricle at the end of systole. Normal EJ is about 2/3 of the blood in the ventricle.
What is stroke volume?
Amount of blood ejected.
Varies between 60-100 mL (70 average)
Starling’s law
The more the myocardial muscle is stretched, the greater its force of contraction (Like a rubber band)
More blood = more force
More venous return = more force
What is afterload? What affects it?
Resistance against which the ventricles must contract.
As increase in peripheral vascular resistance will decrease stroke volume and conversely
Cardiac output formula
Stroke volume (mL) X heart rate (bpm) = cardiac output (mL/min)
70 mL X 70bpm = 4900 mL/min
approx 5L/min
The sympathetic nervous system innervates the heart through the ____ ____, a network of nerves at the base of the heart.
Cardiac plexus
The chemical neurotransmitter for the sympathetic nervous system is ________? What does it do?
Norepinephrine - Increases heart rate and cardiac contractile force, primarily through its actions on beta receptors
The sympathetic nervous system has two principle types of receptors
beta and alpha
Alpha receptors are located in the ___________ and are responsible for __________
peripheral blood vessels
vasoconstriction
Beta 1 receptors are located in the __________ and are responsible for _________.
Heart
Increasing the heart rate and contractility
Beta 2 receptors are located in the ________ and are responsible for _________.
Lungs and peripheral blood vessels
Bronchodilation and peripheral vasodilation
What do beta blockers do?
slow the heart rate and lower blood pressure by blocking the beta 1 receptors
Parasympathetic control of the heart occurs through the ________
vagus nerve
The neurotransmitter for the parasympathetic nervous system is ________ and what does it do?
acetylcholine - it slows the heart and atrioventricular contraction
What does chronotropy refer to?
Positive versus negative?
Heart rate
Positive chronotropic agent will increase HR
Negative chronotropic agent will decrease HR
What does inotropy refer to?
Positive versus negative?
Strength of cardiac muscle contraction
Positive inotropic agent will strengthen
Negative inotropic agent will weaken
What does dromotropy refer to?
Positive versus negative
Rate of nervous impulse condition
Positive dromotropic agent speeds conduction
Negative dropmotropic agent slows conduction
The heart is also an endocrine organ. It secretes 2 hormones (natriuretic peptides).
ANP - atrial natriuretic peptide -
it is manufactured, released and stored by atrial muscle cells in response to atrial distention and sympathetic stimulation. Primarily counters the RAAS and causes a reduction in blood volume, resulting in lower CVP, CO, and BP
BNP - brain natriuretic peptide -
secreted by ventricles in response to excessive stretching. it also counters the RAAS in the same way as ANP. (*Half life of BNP is twice as long as ANP)
BNP *** CHF
Increased levels of ANP are a marker for what?
A-Fib
Increased levels of BNP are a marker for what?
CHF
RAAS does what?
Regulates BP
Intercalated disks located in cardiac muscle fibers do what?
conduct electrical activity quickly throughout heart
Impulses are conducted from the atria to the ventricles through the ____ _____.
atrioventricular (AV) bundle
Depolarization is the contraction or relaxation of the heart?
Contraction
What connects the SA node to the AV node
internodal atrial pathways
these pathways conduct the depolarization impulse to the atrial muscle mass and through the atria to the AV junction
The bundle of His divides into what?
Right and Left bundle branches
AV junction is the “gatekeeper”. How does it affect electrical activity?
it slows the impulse and allows the ventricles to fill
Average SA node bpm
60-100 bpm
Average AV node bpm
40-60 bpm
Average Purkinje System bpm
15-40 bpm
1 small box on the ECG paper is equal to how long?
0.04 seconds
1 large box on the ECG paper is equal to how long?
0.20 seconds
The P wave shows what
atrial depolarization
the QRS complex shows what
ventricular depolarization
the T wave shows what
repolarization of ventricles
the U wave shows what
possible electrolyte imbalance
or could be normal for that person
