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13 Dec 2019

Cytosolic Ca2+ causes muscle contraction by______

a. Binding to troponin

b. Binding to tropomyosin

c. Binding to myosin

d. Binding to actin

Muscle contraction is caused by_______

a. The shortening of actin filaments, caused by theATP-dependent action of myosin

b. The shortening of myosin filaments, caused by theATP-dependent action of actin

c. The sliding of myosin and actin filaments, caused by theATP-dependent action of myosin

d. The sliding of myosin and actin filaments, caused by theATP-dependent action of actin

When an action potential reaches a neuromuscular junction theresult is____

a. Acetylcholine binds to receptors on the sarcoplasmicreticulum, causing Ca2+ to flood the cytosol

b. Acetylcholine binds to receptors on the sarcolemma (muscleplasma membrane), causing depolarization of the sarcolemma

c. Ca2+ binds to receptors on the sarcolemma, causingdepolarization of the sarcolemma

d. Acetylcholine binds to troponin, allowing myosin to bind toactin

The step in the contraction cycle at which ATP binds to myosinis___

a. When myosin binds to actin

b. The “power stroke” when myosin slides the actin filamentalong

c. Just after the “power stroke”, in order to release myosinfrom actin

d. Immediately after Ca2+ enters the cytosol

Which of the following statements about the cytoskeleton istrue?

a. The cytoskeleton is made up of four types of proteinfilaments.

b. The bacterial cytoskeleton is important for cell division andDNA segregation.

c. Protein monomers that are held together with covalent bondsform cytoskeletal filaments.

d. The cytoskeleton of a cell can change in response to theenvironment.

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Jean Keeling
Jean KeelingLv2
17 Dec 2019
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Related questions

1.If the supply of ATP to a shortening muscle is completelydepleted, what will happen to the cross-bridge cycle? What is thename if the phenomenon that results from complet ATP depletion?

2.Order the following 10 events that summarize musclecontraction. Remember that a muscle contraction begins with thetransmission of a nerve impulse to a muscle fiber

a. the power stroke

b. Opening of ryanodine Ca2+ channels in the sarcoplasmicreticulum

c. Binding of mysosin cross-bridges to actin

d. release of acetylcholine into the neuromuscular junction

e. confromational change in tropomyosin troponin complex

f. binding of ca2+ to troponin

g. binding of atp to myosin cross-brisges

h. depolarization of the muscle fiber

i. hydrolysis of atp bound to myosin cross-bridges

j. action potential propagation along the transverse tubules

Describe the process of skeletal muscle contraction by assembling the following 10 events in the proper order. Your answer must be written in complete sentences- do not just list the letters or the events- write it out. Begin your description with an action potential traveling down a motor neuron and end with the muscle in it's relaxed state.

A) T and T system undergoes a conformational change, exposing the myosin binding sites on actin

B) myosin heads/cross bridges bind to actin and flex, shortening the sacromere

C) the motor neuron triggers an action potential at the neuromuscular junction

D) calcium ions bind to the T and T system

E) actin filaments are pulled toward the center of the sacromere, shortening the muscle fiber

F) muscle fiber is stimulated at the neuromuscular junction

G) myosin head/cross-bridges bind to actin

H) APs travel down the T-tubules to the sarcoplasmic reticulum

I) in response to an AP, calcium ions are released into the cytosol/space around the myofibrils

J) calcium ions actively transported into the sarcoplasmic reticulum

K) myosin head continues to attach, flex, release, extend, and reattach as long as calcium ions are present

Question 1. Increased peripheral edema could be caused by:

a. blocked lymph vessels

b. decreased capillary blood pressure

c. increased concentration of albumin in the blood

d. slowed heart rate

Question 2. The pulse pressure of a healthy student is most likely to be:

a. 5 mm Hg

b. 30 mm Hg

c. 95 mm Hg

d. 120 mm Hg

Question 3. beta-blockers inhibit the activity of beta-adrenergic receptors and change the function of the heart by:

a. increasing heart rate and increasing contractility

b. increasing heart rate and decreasing contractility

c. decreasing heart rate and increasing contractility

d. decreasing heart rate and decreasing contractility

Question 4. In cardiac pacemaker cells, the L-type calcium channels:

a. open during diastole

b. close when the membrane potential rises above threshold

c. are located in the cell membrane

d. pump Ca2+ ions into the sarcoplasmic reticulum

Question 5. Dr. Campbell used an elliptical trainer for 40 minutes at the gym. Although the workload remained constant, Dr. Campbell’s heart-rate rose to 150 beats per minute during the first 5 minutes, stayed at that level for the next 25 minutes and then started to rise. It was 180 beats per minute at the end of the exercise period.

What was the time interval between QRS complexes when Dr. Campbell’s heart rate was 180 beats per minute?

a. 3.3 ms

b. 33 ms

c. 333 ms

d. 3333 ms

Question 6. In the question 5 above, Dr. Campbell’s heart rate is most likely to have risen during the last 10 minutes of exercise because his:

a. lungs were becoming congested

b. atrial cells were fatigued

c. extracellular Ca2+ concentration had increased

d. hematocrit increased due to sweating

Question 7. A Physiology student is sitting still in a cold igloo. After 30 minutes, she stands up, walks slowly around the igloo, and suddenly starts to shiver.

The student preserved their core temperature while they were sitting by:

a. depressing their Frank-Starling mechanism

b. decreasing the extracellular Ca2+ concentration

c. relaxing smooth muscles in their peripheral circulation

d. increasing the resistance of arterioles in their arms and legs

Question 8. In the question 7 above, the student started to shiver soon after walking because:

a. their atria started to fibrillate

b. their ventricles started to fibrillate

c. blood moved to the periphery, became cold, and chilled the core when it returned to the chest

d. the ATP concentration in their skeletal muscles had dropped to zero

Please use the following scenario for answering the questions 9 and 10.

A newly discovered drug binds to myosin molecules in cardiac muscle (and nowhere else) and increases the probability that myosin molecules in ventricular cells will bind to actin filaments when the intracellular Ca2+ concentration rises. The drug is being tested as a potential therapy for patients with heart failure.

Question 9. This drug might help people who have low cardiac output by:

a. increasing peripheral resistance

b. increasing the force developed by ventricular cells

c. increasing the isovolumic contraction time

d. increasing heart rate

Question 10. The increased binding of cardiac myosin molecules to actin might prevent the drug from being a useful treatment by:

a. slowing ventricular relaxation

b. decreasing the duration of systole

c. decreasing resistance of capillaries

d. slowing heart rate

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