Physiology Exam 3&4

The cycle of blood through the heart would follow this order:

Right atrium, tricuspid valve, right ventricle, pulmonary semilunar valve, pulmonary arteries, lungs, pulmonary veins, left atrium, mitral valve, left ventricle, aorta semilunar valve.

The order of electric signal through the heart flows as follows:

SA node, AV node, Bundle of HIS, Right and Left Bundle Branches, Purkinje Fibers.

For the hierarchy of skeletal muscle organization, which accurately lists the order of structures form "small" to "big"?

Sarcomere; myofibril; muscle fiber; motor unit.

The primary reservoir for calcium that is released during excitation-contraction coupling in a skeletal muscle fiber is the:

Sarcoplasmic reticulum.

Which structure prevents blood flowing back into the heart from the aorta between the heartbeats?

Semilunar Valve.

Elizabeth had a heart surgery to repair the pacemaker of her heart. Into which structure did the surgeon need access?

Sinoatrial Node

A key role of the atrioventricular node is to:

Slow down the conduction of electrical impulses as it passes from the atria to the ventricles.

According to the Frank-Starling mechanism of the heart:

Stroke volume increases with increased venous return.

Ventricular repolarization occurs at the:

T wave.

The chord tendinae and the papillary muscles work to prevent prolapse of the AV valves. T/F

TRUE

Imagine that secretion of heart muscle no longer has gap junctions. What do you think would be the result?

The ability of the heart muscle cells to coordinate their contractions would be severely compromised.

Venous blood returning to the mammalian heart will drain first into the:

Right Atrium

The electrical stimulus for each human heartbeat begins in the?

Right atrium at the sinoatrial node.

When experimentally applying alpha-bungarotoxin to a muscle, you can find that it does not contract when the motor neuron leading to it is electrically stimulated. Knowing what toxin blocks acetylcholine receptors, what can you conclude about the failure to contract?

A contraction fails to occur because neurotransmitter released by the motor neuron is blocked at the neuromuscular junction due to receptors being occupied already.

What causes the opening and closing of the heart valves?

A pressure difference on the two sides of the valve.

What is the definition of motor unit?

A single motor neuron plus all the muscle fibers it innervates.

Which of the following would occur if you touched a hot object with your right hand?

A withdraw reflex would be triggered by nociceptors that would stimulate contraction flexor muscles in the right arm.

Release of cross-brides depends most directly on?

ATP.

Which of the following statements concerning the differences between action potentials in a skeletal muscles cells and in ventricular cardiac muscle cells is TRUE?

After sodium influx through voltage-gated channels occurs in ventricular cells, prolonged influx of calcium from the extracellular fluid occurs. No such calcium influx occurs in skeletal muscle cells.

Tetanus toxin inhibits acetylcholinesterase activity. What will a person suffering from tetanus toxin poisoning look like?

All muscles in the body might present a tense, fully contracted state.

Sinoatrial Node Cells:

All of the below: -Are automatic in which they are depolarized upon negative potential (-60mV) -Are the heart's pacemaker -Exhibit spontaneous depolarization that is speeded by activation of their cholinergic receptors -Depolarize and show a 'p' wave on an ECG

Identify what is NOT common between neurons interacting skeletal muscle and contractile cardiac cells.

Both have

The plateau of the action potential in the cardiac ventricular cells results from the opening of voltage-gated long lasting__________ channels in the plasma membrane of the cell.

Ca2+

In the muscle function at the sarcomere level, the formation cross-bridges is regulated by the binding of ______ ions to ______.

Calcium; troponin.

Which of the following statements about the cardiac cycle is TRUE?

Closure of the atrioventricular valves ideally occurs before ejection of the blood from ventricles.

Which of the following statements regarding contraction of a skeletal muscle fiber is TRUE?

Contracting muscle fibers require acetylcholine, Ca+ and ATP.

The acetylcholine receptor is a ligand-gated channel that produces:

Depolarization by allowing Na+ ions to enter the muscle fiber.

Action potentials in the heart spread from cell to cell through:

Desmosomes

Following an increase in venous return, which is the only variable that decreases according to Frank Starling Mechanism?

End-Systolic Volume.

The "QRS" complex visible in a normal electrocardiogram is associated with the:

Excitation from the AV node and depolarization of the ventricles.

The after load on the left ventricle of the heart will decrease with rising blood pressure. T/F

False

During the shortening contraction of a skeletal muscle fiber, which of these occurs?

I Bands shortens.

What is TRUE about the tricuspid valve?

It is open during P wave.

You and your colleague are medical technicians in a cardiac function lab. You are reading the ECG of a patient and your friend is trying to capture an image of the semilunar valves opening using an ultrasound. At what point should you tell your friend to start recording images?

Just before the QRS complex.

Muscle cells are stimulated by acetylcholine released from the terminals of:

Motor neuron axons.

What is the correct sequence of events in cross-bridge cycling?

Myosin cross-bridge binds to actin, the power-stroke moves the thin filament relative to the thick filament, ATP binds to myosin and cross-bridge detachment occurs, ATP is hydrolyzed and the myosin head is "cocked".

The thick filament is composed almost entirely of _____ molecules.

Myosin.

Which protein contains a binding site for ATP?

Myosin.

Which occurs during isovolumetric ventricular contraction?

No blood enters or leaves the ventricles .

Predict what would happen if the pulmonary view returned blood to the right atrium.

Oxygenated blood would be kept in a circular path between the heart and lungs.

You have designed a drug that is supposed to bind to the myosin binding sites on actin. You inject it into a relaxed muscle, but find that none of the drug is bound. Which of the following explains why?

The binding sites on actin are covered by tropomyosin.

What is TRUE about the Frank Starling Mechanism?

The increase in venous return allows muscle stretch and therefore actin and myosin are optimally aligned.

When an organism dies, its muscles remain in a contracted state termed rigor mortis for a brief period of time. Contributing most directly to this phenomenon is:

The lack of ATP to break cross-bridges between thick and thin filaments.

Which best defines cardiac output?

The product of the heart rate and the volume ejected from the ventricle during a cardiac cycle.

Which is correct about the contraction sequence of the heart?

The two atria contract at the same time, and as they are relaxing, the two ventricles contract together.

What is the primary function of transverse tubules?

They conduct action potentials from the surface of the muscle fiber to internal regions near myofibrils.

In a laboratory experiment you have treated a muscle cell with a calcium cannel blocker. The membrane is still depolarizes, but the concentration of calcium never increases in the cytosol. Which of following describes what would happen next?

Tropomyosin will continue to cover the binding sites on actin and no cross-bridges will form.

In skeletal muscle cells, calcium initiates contraction by binding to:

Troponin.

Drugs such as atropine and dopamine can increase the heart's rate and contractility. T/F

True

During their systole, the heart chambers are contracting. T/F

True

When a person steps on a piece of glass with their right foot, flexor muscles on the right leg and extensor muscles on the left leg will be stimulated to contract. T/F

True

Most of the blood (80%) moves from the atria to the ventricles in a 'passive' fashion (before contraction). T/F

True.

You and your lab partner are doing an experiment in physiology lab. Each of you has an isolated muscle cell and you are supposed to stimulate it with an electrode as soon as its absolute refractory period ends. You're watching an electromyograph tracing to know when to use the electrode. Your partner has a cardiac muscle cell and you have a skeletal muscle cell. Which one of you will use your electrode more times?

You will use the electrode on the skeletal muscle cell more times in a minute than your partner will.