Pool Questions 4 Flashcards
Maximum power and maximum efficiency occurs at what percentage of maximum velocity?
⅓ max velocity
What is the definition of a motor unit?
A motor neuron and all the fibers it innervates
What is the difference between the epimysium, perimysium and endomysium?
Epimysium is the connective tissue around the muscle, perimysium is the connective tissue around bundles of muscle fibers (fascicle), endomysium is the connective tissue around individual muscle fibers.
What is a triad? Each sarcomere has how many triads?
A triad is a triple layer structure with two sacs of sarcoplasmic reticulum called cisternae with a T Tubule in the middle. 2 triads per sarcomere
What determines the speed of contraction?
The amount of fibers dedicated to the movement as well as the composition of the fibers (aka more fast twitch fibers vs slow twitch). Amount of ATPase is another key-factor. fast twitch have more ATPase.
T/F-During contraction, the length of myosin does not change.
True
What is the mechanism of Excitation Contraction Coupling?
Action potential on an alpha-motor neuron. Acetylcholine is released and binds to the sarcolemma. Action potential down the sarcolemma which then goes to the T-tubules. Calcium is released from the SR. Calcium then binds to troponin. Myosin binding sites appears when calcium attaches to TPN and lets go of actin. Myosin head automatically binds to actin. Hydrolysis of ATP enables power-stroke. Shortening of the Z lines. Another hydrolysis of ATP enables a release of the myosin head from actin.
What % of cardiac cells generate action potentials spontaneously?
1%
T/F- The heart requires action potentials from neurons or other signaling mechanisms in order for the SA Node to initiate contraction electrically.
False-internally spontaneous, is its own pace maker
Write out the route of cardiac AP flow starting with the SA node.
SA Node, bundle of bachmann, internodal tracts, AV node, bundle of his, purkinje fibers
Explain why the SA Node is the “pacemaker” of the heart. Why does the AP initiate there?
Depolarization occurs quickest in the SA node
Which layer of the heart wall forms the bulk of the heart?
Myocardium
Cardiac output is defined as
the amount of blood pumped through the heart in one minute.
- Brachiocephalic Trunk
- Superior Vena Cava
- Aortic Valve
- Pulmonary Semilunar valve
- Right Atrium
- Papillary muscles
- Left common carotid artery
- Left subclavian artery
- Aorta
- Pulmonary Artery
- Pulmonary Vein
- Left Atrium
- Chordae Tendinae
Given a stroke volume of 80ml and a cardiac output of 5500ml, determine the corresponding heart rate.
CO (Q)=SV*HR
5500=80*HR
HR=68.75 beats/minute
Blood Volume in the body is approximately
5-6 L
This part of the heart anchors the heart to the surrounding structures and prevents overfilling.
Pericardium
Which portion of the ECG represents atrial depolarization?
P wave
Which muscle fiber type has the largest cross sectional area of fiber?
Type IIx fast twitch; greater the cross sectional area of the fiber the greater the force and speed it can generate
Compare the differences in stroke volume and heart rate of a sedentary individual at rest to an endurance trained individual at rest.
Sedentary SV: 70-80mL, Trained SV: 120-130mL
Trained SV is much larger because they have the same cardiac output but the heart is more efficient at pumping blood with less work (aka lower HR)
HR: Sedentary: 70 bpm, Trained: 40-50 bpm
On the length tension curve, what is the length where no more cross bridges are formed
3.7 micrometers
On the length tension curve, what is the length of actin?
1.05 micrometers
On the length tension curve, what is the length of myosin?
1.6 micrometers (um)
How many liters of blood does the body hold? How many can it hold?
5-6 L on average but can hold 12-15L
The ___ is consists of pacemaker cells, which contain the fastest conduction velocity In the heart. The ___ has the slowest conduction velocity.
SA Node
AV Node
Why is there a delay between the depolarization of the AV node and the Bundle of His
So the valve can close and prevent backflow of blood
How does the cardiac muscle receive its blood flow?
Coronary vessels take some of the blood entering the heart from the lungs to also supply the heart itself
What governs the opening and closing of valves in the heart?
Pressure gradient
What is the purpose of the connections within intercalated discs?
They help to hold adjacent cells together and transmit the force of contraction from cell to cell. Intercellular junctions between the fused membranes of the intercalated disks allow diffusion of ions between the cells. This makes it possible for muscle impulses to travel rapidly from cell to cell.
What is the only way to increase the amount of oxygen going to the heart?
The main way to increase the oxygen supply to the heart is to increase the blood flow through the coronary arteries. Your heart increases the blood flow by widening (dilating) your coronary arteries.
What is an average persons HR, Q, and SV at rest?
HR: 70
SV: 70-80ml
Q: 5000-6000 ml/min
What is cardiac output?
Amount of blood that is pumped out of the heart with each heartbeat
Endurance athletes have a lower HR than the average person at rest; however, what allows them to pump the same amount of blood despite this difference?
Larger stroke volumes to supply their bodies with the same amount of blood with less work
What causes the “lub-dub” sound
Lub - The closing of the AV valves
Dub - The closing of the semilunar valve
What is the optimal length muscles operate on in the length tension curve?
1.8-2.5 micrometers
What is the function of papillary muscles?
Papillary muscles are located in the ventricles of the heart. They attach to the cusps of the atrioventricular valves (mitral and tricuspid valves) via the chordae tendineae and contract to prevent inversion or prolapse of these valves on systole/ventricular contraction.
How does blood move through the heart?
IVC/SVC-RA-Tricuspid valve-RV-Pulmonary semilunar valve-pulmonary arteries-Lungs-pulmonary veins-LA-Mitral/bicuspid valve-LV-Aortic semilunar valve-aorta-body
What are the phases of the heart cycle
Filling phase
Isovolumetric contraction phase
Ejection phase
Isovolumetric relaxation phase
Describe the relationship between left atrial, left ventricular, and aortic pressure going through the phases of the heart cycle.
Filling phase-
Isovolumetric contraction phase-
Ejection phase-
Isovolumetric relaxation phase-
What happens when a muscle starts to contract if it’s fibers are in the descending limb of the length tension curve?
Muscle Tearing
