Lecture 6 Flashcards
Cardiovascular system
What does the circulatory system transport?
Nutrients and oxygen
What are the 3 Components of the circulatory system?
Heart
Blood vessels
Blood
1) What does blood travel through?
2) Where do these originate and terminate?
1) Two separate vascular loops
2) Originate and terminate at the heart
Name the two vascular loops blood travels through, and where they go
1) Pulmonary circulation: between heart and lungs
2) Systemic circulation: between heart and body
1) Where is the heart?
2) What happens when the heart beats forcefully?
3) What is the heart divided into?
1) In thoracic cavity between sternum and vertebrae
2) Apex “thumps” against left chest wall
3) 4 chambers separated by the septum
True or false: The outputs of R and L heart are independent.
False; they’re interdependent
1) What does the right atrium receive? Through what?
2) What valve does this then go through?
3) What does the right ventricle do? Through what?
1) O2 depleted blood via SVC and IVC
2) Tricuspid valve
3) Pumps this blood into pulmonary circulation via the pulmonary artery
1) What occurs in pulmonary circulation?
2) What type of transport is this?
1) Gas exchange
2) Diffusion; passive +
1) What does the left atrium receive? Through what?
2) What valve does this then go through?
3) What does the left ventricle do? Through what?
1) O2 rich blood via pulmonary veins
2) Mitral (bicuspid) Valve
3) Pumps this blood into systemic circulation via the aorta
List the 3 general principles of blood flow
1) Both sides simultaneously pump equal amounts of blood
2) Pulmonary circulation is low-pressure, low-resistance
3) Systemic circulation is high-pressure, high-resistance
Pulmonary circulation is _________pressure, __________resistance
low-pressure, low-resistance
1) What is the purpose of valves?
2) How many cardiac valves are there? What do they do?
1) Ensure correct direction of blood flow
2) 4 cardiac valves that open and close passively due to pressure differences
1) Where are the (atrioventricular) AV valves?
2) When do they open?
1) Between atrium and ventricle; one each side of heart
2) Open when atrial pressure exceeds ventricular pressure
What are the left and right AV valves called?
Right: tricuspid valve
Left: bicuspid/mitral valve
1) When do the SL (semilunar) valves open?
2) What are the names of each?
1) With ventricular contraction
2) Aortic and pulmonary SL valves
1) What are the chordae tendineae?
2) What do they do?
3) Where do they attach? What does this structure do?
1) Thin, tendinous chords
2) Prevent valves from everting
3) Attach to papillary muscles, which contract with ventricles and pull on the chordae tendineae
1) What is the fibrous skeleton made of?
2) What does it do?
3) What does it separate?
1) Dense connective tissue
2) Surrounds and anchors the valves (fibrous rings)
3) Separates atria from ventricles
What are the 3 distinct layers of the heart wall?
1) Endothelium/endocardium
2) Myocardium
3) Epicardium
What is the pericardium?
Double-walled membranous sac [around the heart]
True or false: All cardiac cells are coupled electrically and mechanically
True
1) How would you describe the structure of cardiac muscle?
2) How are adjacent cells joined?
1) A functional syncytium
2) At specialized structures called intercalated discs
What 2 things do the intercalated discs contain? Describe each
1) Desmosomes: adhering junction, tolerates mechanical stress
2) Gap junctions: low electrical resistance, AP’s spread; important for synchronous contraction
What is important for synchronous contraction of the heart?
Gap junctions
Describe what makes the atria and ventricles separate units (2 things)
1) No gap junctions between atrial and ventricular contractile cells
2) Fibrous skeleton is also nonconductive
How do the atria and ventricles coordinate pumping?
Due to specialized conduction system
1) What causes autorhythmicity/automaticity of the heart?
2) What occurs for this to happen?
1) Heart contracts rhythmically due to action potentials it generates by itself
2) Action potentials spread across muscle cell membranes, trigger cardiac muscle contraction
What are the two specialized types of cardiac muscle cells? Describe each
1) Autorhythmic cells: do not contract; initiate and conduct AP’s
2) Contractile: 99% of cardiac muscle cells; do the mechanical work, don’t initiate AP’s
True or false: Cardiac autorhythmic cells do not have “resting potentials. Explain your answer
True; instead, they have pacemaker potentials
Pacemaker activity is due to what 3 things?
1) Increased inward Na+
2) Decreased outward K+
3) Increased inward Ca+
1) What are the Funny channels of pacemaker activity?
2) When do they open?
3) What does this lead to?
1) Unique voltage-gated Na+ channels
2) Opens on hyperpolarization (rather than depolarization)
3) Slow depolarization (pacemaker potential)
1) What happens after the Funny channels open and depolarization starts?
2) What does this cause?
1) K+ channels slowly close
2) Gradually diminishes K+ outflow, causing further depolarization
1) What open before threshold potential, but after K channels slowly close?
2) What does this cause?
1) Ca+ channels open before threshold potential
2) Ca+ influx, further depolarization
1) What happens once threshold potential is reached?
2) What does this cause?
3) How is this different in nerves and skeletal muscle, compared to cardiac muscle?
1) Long-lasting voltage gated Ca+ channels open
2) Large influx of Ca+
3) It’s Na+ instead in nerves and skeletal muscle
1) What happens at the peak of depolarization?
2) What two things allow for things to be reset after?
1) Voltage gated K+ channels open, K+ efflux
2) Ca+ reuptake via SERCA pump, and the Na-K pump
Once an AP is generated in any cardiac muscle cell, what happens?
It propagates via gap junctions and conduction system
Autorhythmic (noncontractile) cells are found in what 4 places? Describe where each is
1) Sinoatrial (SA) node: of the RA near SVC
2) Atrioventricular (AV) node: of RA base near septum
3) Bundle of His (AV bundle): originates in AV node
-Enters septum between ventricles
4) Purkinje fibers: originate from Bundle of His
-Spread through ventricular myocardium
True or false: Autorhythmic cells in different areas have differing rates of slow depolarization
True
What is the pacemaker? Why?
SA node is the pacemaker because it is the fastest
In what two ways are all cardiac cells coupled?
Electrically and mechanically
Where does the bundle of His (AV bundle) originate? Where does it enter?
1) Originates in AV node
2) Enters septum between ventricles
Why can’t other cells resume their slower rates?
They are triggered at the rate of the SA node
If there is SA node damage, what takes over?
AV node
1) If there is blocked conduction between atria and ventricles, what happens?
2) What can be used to help?
1) Then coordination breaks down; Complete heart block
2) Artificial pacemaker can be used in these cases
What does an artificial pacemaker do?
Rhythmically generates impulses typically 70bpm
1) Define ectopic focus
2) What does it lead to?
3) What can cause this?
1) Area of the heart becomes more excitable and depolarizes faster than SA node
2) Premature action potential = premature ventricular contraction
3) Heart disease,anxiety, caffeine, lack of sleep, sometimes genetic
What are the 3 steps of electrical activity?
1) Atrial excitation and contraction completes before onset of ventricular contraction (160ms)
2) Cardiac muscle fibers must be coordinated
3) Atrial and ventricular pairs contract simultaneously
Atrial excitation and contraction completes when?
Before onset of ventricular contraction (160ms)
1) What cannot pump blood?
2) What can?
3) What can help with coordination?
1) Contraction of isolated muscle fibers cannot successfully pump blood
2) Smooth rhythmic contraction
3) Fibrillation