Cardiovascular Physiology Lecture 2 Flashcards
What are the four valves in the heart?
- Atrioventricular (AV) valves - between atria and ventricles
- Bicuspid (mitral): between L Atrium and L ventricle
- tricuspid: between R Atrium and R ventricle
- Semilunar (arterial) valves - between the ventricles and there arteries into which the ventricles pump
- aortic valve
- pulmonary valve
What are valves made of?
What are the flaps called?
Made of fibrous tissue (collagen) covered by endothelium
The valve flaps are also called leaflets or cusps
What are valve rings?
What the valves attach to
Made of cartilage
How do the valves open and close?
Passively: due to differences in pressure or pressure gradients (do not require muscle)
What happens to the atrioventricular valves when the pressure in the atria exceeds the pressure in the ventricle?
AV valves open
What is the funciton of the AV valves?
Prevent backflow of blood into the atria as the ventricles contract
What are the chordae tendineae?
Tendinous-type tissue that extend from edges of each leaflet to papillary muscle.
What are papillary muscles?
Do they contract?
Cone-shaped muscles
- contraction of papillary muscles causes the chordae tendineae to become taut
- holds valve in closed postion
What is the Cardiac skeleton?
Fibrous skeleton of the heart
What is the cardiac skeleton made of?
Dense connective tissue
What is included in the cardiac skeleton?
- Heart valve rings
- dense connective tissue between the heart valves
What are three functions of the cardiac skeleton?
- physically separates the atria from the ventricles
- electrically inactive and blocks the direct spread of electrical impulses from the atria to the ventricles
- Provides support for the heart, providing a point of attachment for the valves leaflets and cardiac muscle
What is coronary circulation?
Part of the systemic circulatory system that supplies blood to and provides drainage from the tissues of the heart
Where do the coronary arteries originate?
Coronary arteries originate at aortic sinuses at base of ascending aorta
Supply blood to the heart
What is the aortic sinus?
Dilation or “out-pocketing” of the ascending aorta; site where the left and right coronary arteries originate
Where do the cardiac veins empty?
Coronary sinus
- collection of veins joined together to form a large vessel that collects blood from the myocardium of the heart
What is systole?
Ventricular contraction
What is diastole?
Ventricular relaxation
Blood flow almost ceases when the heart is ______ and peaks while the heart is ______
Blood flow almost ceases when the heart is contracted (systole) and peaks while the heart is relaxed (diastole)
What causes coronary artery disease?
Atherosclerosis of the coronary arteries.
atherosclerosis = condition where arteries become hardened and narrow due to plaque in the walls
What is atherosclerotic plaque made of?
fat, cholesterol, calcium and other substances in the blood
What is angina?
Chest pain or discomfort when blood flow to heart muscle is reduced
What is myocardial infarction?
Heart attack
- atherosclerotic plaques can grow so large that they completely block arterial blood flow causing a heart attack
- heart muscle dies due to loss of blood supply
Cardiac muscle cells _______ are joined by ________ which contain ______
Cardiac muscle cells myocytes are joined by intercalated discs which contain gap junctions and desmosomes
What is a syncytium?
Why is cardiac muscle called a syncytium?
Set of cells that act together.
The cardiac muscle is called a syncytium as the myocytes are mechanically, chemically, and electrically connected and act as a single enormous muscle cell
_______ allow excitation (AP’s) to spread quickly from one myocyte to another by cell-to-cell contact
Gap junctions allow excitation (AP’s) to spread quickly from one myocyte to another by cell-to-cell contact
What are the 2 functional syncytia of the cardiac muscle?
- the left and right atria
- Left and right ventricles
What is autorhythmicity (automaticity)?
The heart contracts or beats rhythmically as a result of action potentials that it generates itself
How are action potentials in the heart generated?
Without nervous or hormonal stimulation:
Rhythmicity of the heart is myogenic in origin - it is muscular in origin
What are the 2 types of specialized cardiac muscle cells (myocytes)?
Contractile cells
Conducting cells
do mechanical work of pumping, propel blood; do not initiate action potentials
Contractile cells
Initiate and conduct AP’s which are responsible for contraction of the contractile cells
-myocytes which initiate and conduct AP’s w/o Nervous or hormonal stimuli
Conducting cells (autorhythmic cells)
The conducting cells have very few _______ and do not contribute to the heart’s contraction and movement of blood
The conducting cells have very few myofibrils (protein filaments needed for contraction) and do not contribute to the heart’s contraction and movement of blood
Most myocytes are:
Conducting or Contractile?
Contractile (~99%)
Conducting cells are in ______ contact with each other and the cardiac contractile cells through the _____
Conducting cells are in electrical contact with each other and the cardiac contractile cells through the gap junctions
The spread of action potentials through the ___ leads to contraction of the heart muscle
The spread of action potentials through the myocardium leads to contraction of the heart muscle
Where are conducting myocytes found?
(6)
- Sinoatrial node (SAN)
- Internodal pathways
- Atrioventricular node (AVN)
- bundle of His (AV bundle)
- left and right bundle branches
- Purkinje fibres
Where is the sinoatrial node located?
Wall of the right atrium
Where is the Atrioventricular node (AVN) located?
Base of the right atrium
The internodal pathways extend from the _____ to the _____ and also cross the ______ to the left atrium
The internodal pathways extend from the sinoatrial node to the atrioventricular node and also cross the interatrial septum to the left atrium
The Bundle of His passes through the _____
The Bundle of His passes through the cardiac skeleton
Left and right bundle branches travel along the _______ septum
Left and right bundle branches travel along the interventricular septum
Left and right bundle branches make contact with Purkinje fibres which extend into the ______ of the _____
Left and right bundle branches make contact with Purkinje fibres which extend into the myocardium of the ventricles
The only electrical connection between the atria and the ventricles in a normal heart is the ______ and the _____.
The _______ is non-conducting
The only electrical connection between the atria and the ventricles in a normal heart is the Atrioventricular Node and the Bundle of His.
The Cardiac skeleton is non-conducting
Conducting myocytes in the _______ generate AP’s at the fastest rate (60-100 AP/min)
Conducting myocytes in the Sinoatrial Node generate AP’s at the fastest rate (60-100 AP/min)
Which component of the conducting system is considered the “cardiac pacemaker”?
SA node - initiates AP that set the heart rate
SA node generates AP > ________ > _______ of both the Left and right atria > _____ and ______ _____ contract at the same time > stimulus also passed by the _____ to the _____ > wave of depolarization must pass through the ______ and the ____ to excite the ______ due to presence of the cardiac skeleton
SA node generates AP > internodal pathways > contractile cells of both the Left and right atria > left and right atria contract at the same time > stimulus also passed by the internodal pathways to the AV node > wave of depolarization must pass through the AV node and the bundle of his to excite the ventricles due to presence of the cardiac skeleton
Stimulus passes to the AV node through the _______ from the _____
Stimulus passes to the AV node through the internodal pathways from the SA node
What is AV nodal delay?
the propagation of AP’s through the AVN is relatively slow: take ~100 milliseconds for the stimulus to pass through the AV Node to the Bundle of His
- delay ensures that the atria depolarize and contract before the ventricles depolarize and contract
What is wolff-parkinson-white syndrome?
In wolff-parkinson-white syndrome there is an extra connection in the heart called an accessory pathway
What is an accessory pathway?
Abnormal piece of muscle that connects directly between the atria and ventricles
- electrical signals bypass the AVN and move to ventricles faster than usual
- Elect. impulses may also be transmitted from he ventricles back to the atria
- disrupts the coordinated mvmt of electrical signals through the heart leading to abnormally face heartbeat called tachycardia and other arrythmias
