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Biophysics Quiz on Chapter 1, created by Y Y on 22/06/2019.

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Chapter 1

Chapter 1

Question 1 of 59

1

What is the necessary condition for generation of spike potentials in smooth muscle cells?

Select one of the following:

  • a) sufficient intra-cellular calcium deposits;

  • b) reaching membrane depolarization threshold;

  • c) sufficient density of voltage-gated Na+ channels.

Explanation

Question 2 of 59

1

Spike potentials in smooth muscles are defined as:

Select one of the following:

  • a) action potentials;

  • b) slow waves;

  • c) Ca2+ equilibrium potentials.

Explanation

Question 3 of 59

1

Smooth muscle tissue is build of this type of cells:

Select one of the following:

  • a) cylindrical cells;

  • b) spindle-shaped cells;

  • c) relatively small hexagonally-shaped cells.

Explanation

Question 4 of 59

1

“Slow waves” are present in:

Select one of the following:

  • a) gastrointestinal smooth muscle tissue;

  • b) bronchial smooth muscle tissue;

  • c) arterial smooth muscle tissue.

Explanation

Question 5 of 59

1

Slow waves are changes in the membrane potential in certain smooth muscles:

Select one of the following:

  • a) due to input from the nervous system;

  • b) not due to stimuli from the nervous system or endogenous substances;

  • c) due to endogenous substances.

Explanation

Question 6 of 59

1

Is there a functional relationship between slow waves and spike potentials in smooth muscle cells?

Select one of the following:

  • a) yes, slow waves can trigger spike potentials;

  • b) there is no known functional dependence;

  • c) yes, spike potentials can trigger slow waves

Explanation

Question 7 of 59

1

The dynamics of ion flow during spike potentials is:

Select one of the following:

  • a) Na+ influx → depolarization, K + efflux → repolarization;

  • b) Ca2+ influx → depolarization, K + efflux → repolarization;

  • c) Ca2+ efflux → depolarization, Na+ influx → repolarization.

Explanation

Question 8 of 59

1

In the cytosol Ca2+ ions bond to, and activate a protein which plays a critical role in the contraction
of the smooth muscle. This protein is:

Select one of the following:

  • a) calmodulin;

  • b) tropomyosin;

  • c) troponin C

Explanation

Question 9 of 59

1

Which of the following muscles do not have an ordered sarcomere structures?

Select one of the following:

  • a) skeletal muscles;

  • b) cardiac muscle;

  • c) smooth muscles.

Explanation

Question 10 of 59

1

Which ion channels permit the Ca2+ ion influx, necessary for the spontaneous phasic contractions
of smooth muscles?

Select one of the following:

  • a) receptor-regulated channels (triggered by ligands);

  • b) voltage-gated (membrane potential dependent);

  • c) stretch-regulated (mechanical forces on the membrane).

Explanation

Question 11 of 59

1

What type of contraction results in smooth and striated muscles when the intervals between
consecutive action potentials are shorter than the duration of muscle fiber contractions?

Select one of the following:

  • a) single contraction;

  • b) phasic contractions;

  • c) complete or incomplete tetanus

Explanation

Question 12 of 59

1

Which is the best description of the membrane potential of striated muscles when there are no
muscle contractions?

Select one of the following:

  • a) rhythmic low frequency fluctuations below threshold excitation- formation for slow waves;

  • b) steady resting potential;

  • c) slow depolarization initiated from pacemaker cells

Explanation

Question 13 of 59

1

What is the source of Ca2+ needed for the contraction of striated skeletal muscles?

Select one of the following:

  • a) from intracellular Ca2+ depots;

  • b) influx of Ca2+ from the extracellular fluid into the sarcoplasm, which leads to additional Ca2+ release form intracellular depots;

  • c) through suppression of the activity of the calcium pumps (which remove intracellular Ca2+

Explanation

Question 14 of 59

1

What type of membrane channels are activated during action potential propagation along the
sarcolemma of striated muscle cells?

Select one of the following:

  • a) voltage-gated sodium channels;

  • b) calcium channels, regulated by ryanodine receptors;

  • c) voltage-dependent calmodulin receptors

Explanation

Question 15 of 59

1

The sarcoplasmic reticulum of smooth muscle cells can be characterized as:

Select one of the following:

  • a) very elaborate;

  • b) moderately developed;

  • c) not elaborate

Explanation

Question 16 of 59

1

Are there motor endplates in smooth muscle tissues?

Select one of the following:

  • a) yes;

  • b) no;

  • c) sometimes

Explanation

Question 17 of 59

1

Phasic contraction in smooth muscle cells are responsible for:

Select one of the following:

  • a) peristaltic movement;

  • b) the heartbeat;

  • c) release of neurotransmitter molecules

Explanation

Question 18 of 59

1

The existence of “slow waves” in the membrane potential is characteristic for:

Select one of the following:

  • a) phasic smooth muscle cells;

  • b) tonic smooth muscle cells;

  • c) neurons

Explanation

Question 19 of 59

1

19. Blood vessels are predominately build of:

Select one of the following:

  • a) tonic smooth muscle tissue;

  • b) phasic smooth muscle tissue;

  • c) satiated muscle tissue

Explanation

Question 20 of 59

1

Activation of the enzyme myosin light chain kinase (MLCK) leads to:

Select one of the following:

  • a) contraction in smooth muscle cells;

  • b) relaxation in smooth muscle cells;

  • c) initiation of slow waves

Explanation

Question 21 of 59

1

The basic contraction unit in muscle tissues is:

Select one of the following:

  • a) the smooth muscle cell;

  • b) the smooth muscle fiber (myofibril);

  • c) the fiber bundle, wrapped in connective tissue (fascicle).

Explanation

Question 22 of 59

1

Choose the correct statement:

Select one of the following:

  • a) in visceral smooth muscle tissue, found in hollow organs, fiber bundles are innervated together (as a single unit), and individual cells communicate via nexuses (gap junctions);

  • b) in visceral smooth muscles, found in hollow organs, each muscle cell is innervated individually (as a multi-unit), and individual cells communicate via gap junctions;

  • c) in visceral smooth muscles, found in hollow organs, each muscle cell is innervated individually, and
    individual cells do not communicate.

Explanation

Question 23 of 59

1

Choose the set of characteristics that describes best smooth muscle contractions:

Select one of the following:

  • a) voluntary, slow, large energy expenditure;

  • b) involuntary, fast, low energy expenditure;

  • c) involuntary, slow, low energy expenditure.

Explanation

Question 24 of 59

1

The thin myofilaments in smooth muscle cells are build of:

Select one of the following:

  • a) 4 types of contractile proteins;

  • b) 2 types of contractile proteins;

  • c) 3 types of contractile proteins.

Explanation

Question 25 of 59

1

The basis of the thin myofilaments in smooth muscle tissue is the protein:

Select one of the following:

  • a) myosin;

  • b) actin;

  • c) troponin

Explanation

Question 26 of 59

1

The basis of the thick myofilaments in smooth muscles is the protein:

Select one of the following:

  • a) myosin;

  • b) actin;

  • c) tropomyosin

Explanation

Question 27 of 59

1

Choose the correct statement regarding discrete (multi-unit) smooth muscles:

Select one of the following:

  • a) in discrete smooth muscle tissue, found in hollow organs, each cell is innervated separately, and individual cells communicate via nexuses (gap junctions);

  • b) in discrete smooth muscles each cell is innervated individually, thus cells do not communicate directly;

  • c) in discrete smooth muscles, found in hollow organs, fibers are innervated together in bundles, and individual cells communicate via nexuses (gap junctions)

Explanation

Question 28 of 59

1

In smooth muscles fibers the ratio between actin and myosin (thin/tick) fibers is:

Select one of the following:

  • a) random;

  • b) 5:1 to 13:1;

  • c) always 6:1.

Explanation

Question 29 of 59

1

Thin myofilaments in smooth muscle tissues are build of the following proteins:

Select one of the following:

  • a) myosin, actin, titin, and troponin;

  • b) actin and tropomyosin;

  • c) actin, titin, and calmodulin

Explanation

Question 30 of 59

1

What is the spacial orientation of the smooth muscle contractile apparatus?

Select one of the following:

  • a) random orientation;

  • b) aligned in one direction, along the length of the fiber;

  • c) aligned in two perpendicular directions.

Explanation

Question 31 of 59

1

What is the source of Ca2+ needed for the contraction of the smooth muscles?

Select one of the following:

  • a) from the extracellular medium, where calcium concentration is much greater than in the intracellular space;

  • b) from in the intracellular depots, found in the sarcoplasmic reticulum;

  • c) both a. and b.

Explanation

Question 32 of 59

1

What is the role of Ca2+ in the smooth muscle contraction?

Select one of the following:

  • a) bonds to regulatory protein calmodulin;

  • b) bonds to the myosin molecule;

  • c) Ca2+ does not affect smooth muscle contraction.

Explanation

Question 33 of 59

1

Which intracellular factors lead to a smooth muscle relaxation?

Select one of the following:

  • a) factors that activate the enzyme myosin light chain phosphatase;

  • b) factors that inhibit the enzyme myosin light chain phosphatase;

  • c) factors that activate the enzyme myosin light chain kinase.

Explanation

Question 34 of 59

1

Which intracellular factors lead to a smooth muscle contraction?

Select one of the following:

  • a) factors that activate the enzyme myosin light chain phosphatase;

  • b) factors that inhibit the enzyme myosin light chain phosphatase;

  • c) factors that activate the enzyme myosin light chain kinase.

Explanation

Question 35 of 59

1

What is the role of the enzyme myosin light chain kinase (MLCK) in the smooth muscle
contraction?

Select one of the following:

  • a) it shortens the thin myofilaments and, after phosphorylation, it bends actin into a spiral;

  • b) it phosphorylates the 20-kDa myosin light chain (MLC 20) of the myosin molecule, allowing for cross-bridge formation between thin and thick myofilaments;

  • c) it interacts with ATP and the thin myofilaments, delivering energy for the contraction

Explanation

Question 36 of 59

1

What is the role of the enzyme myosin light chain phosphatase (MLCP) in the smooth muscle
relaxation?

Select one of the following:

  • a) after contraction, it lengthens the thick myofilaments;

  • b) it de-phosphorylates the 20-kDa myosin light chain (MLC 20) of the myosin molecule, disrupting the bonding of myosin with the dense bodies of the membrane;

  • c) it de-phosphorylates the 20-kDa myosin light chain (MLC 20) of the myosin molecule, disrupting the cross-bridge formation between thin and thick fibres.

Explanation

Question 37 of 59

1

What is the function of protein calmodulin for the smooth muscle contraction?

Select one of the following:

  • a) it forms a complex with four calcium ions, which activates the enzyme myosin light chain kinase (MLCK);

  • b) does not affect smooth muscle contraction;

  • c) it transports Ca2+ from the cellular membrane to the protein troponin C.

Explanation

Question 38 of 59

1

The electro-mechanical coupling of smooth muscles is:

Select one of the following:

  • a) muscle contraction stimulated with electric current;

  • b) the relation between action potential and subsequent increase of intracellular Ca2+
    leading to contraction;

  • the directed movement of Ca2+ (electric current) in the cytosol towards the contractile apparatus (mechanical).

Explanation

Question 39 of 59

1

What is a spike potential?

Select one of the following:

  • a) a rapid change in the membrane potential due to a slow wave;

  • b) action potential in certain smooth muscle cells;

  • c) electric phenomenon due to re-orientation of the myofilaments in the smooth muscle cell.

Explanation

Question 40 of 59

1

0. Is there a relationship (and if there is then what type) between spike potentials and the Ca2+
concentration in the cytosol?

Select one of the following:

  • a) yes there is. Spike potentials are caused in part by Ca2+ influx and that leads to increase in the intracellular calcium;

  • b) no;

  • c) yes, there is. Spike potentials cause Ca2+ efflux which leads to decrease of the calcium concentration in the cytosol.

Explanation

Question 41 of 59

1

Is there a relationship (and what type) between spike potentials and the strength of contraction of
smooth muscles?

Select one of the following:

  • a) no;

  • b) yes, it is proportional. The greater the number of spike potentials the stronger the contraction;

  • c) Yes. An increased number of spike potentials will decrease the strength of muscle contraction

Explanation

Question 42 of 59

1

Is there a difference in the properties of phasic and tonic smooth muscle contractions?

Select one of the following:

  • a) no, they are two names for the same basic process;

  • b) yes. Phasic contractions occur with certain repetition of few times per minute, and tonic contractions rise slowly and can last many minutes;

  • c) yes. Tonic contractions occur with regular frequency and amplitude, and phasic contractions are slow and can last many minutes.

Explanation

Question 43 of 59

1

Spike potentials are found in:

Select one of the following:

  • a) hepatocytes;

  • b) cardiac contractions;

  • c) phasic smooth muscle contractions

Explanation

Question 44 of 59

1

Tonic smooth muscle contractions are characterized by:

Select one of the following:

  • a) generation of autonomous action potential;

  • b) the lack autonomous action potential;

  • c) positive membrane potential.

Explanation

Question 45 of 59

1

Phasic smooth muscles are characterized by:

Select one of the following:

  • a) their steady membrane potential;

  • b) their function to maintain the tonus in blood vessels;

  • c) sinusoidal variation in the membrane potential.

Explanation

Question 46 of 59

1

During smooth muscle contraction, the concentration Ca2+
in the cytosol increases to:

Select one of the following:

  • a) 10-5 mol/l;

  • b) 10-7 mol/l;

  • c) 107 mol/l.

Explanation

Question 47 of 59

1

Spike potentials in smooth muscles provide:

Select one of the following:

  • a) Ca2+ influx from the extracellular space into the cytosol;

  • b) Ca2+ efflux from the cytosol into the extracellular space;

  • c) bidirectional transfer of Ca2+ across the membrane, leading to equilibrium.

Explanation

Question 48 of 59

1

In smooth muscle cells, the complex 4Ca∙Calmodulin activates:

Select one of the following:

  • a) the light chain of myosin phosphatase;

  • b) myosin light chain kinase (MLCK);

  • c) the Ca2+ regulated K + channels.

Explanation

Question 49 of 59

1

Ca2+ pumps work to:

Select one of the following:

  • a) increase Ca2+ concentrations in the cytosol;

  • b) decrease Ca2+ concentrations in the cytosol;

  • c) do not affect cytosol concentrations of Ca2+

Explanation

Question 50 of 59

1

The two known Ca2+ depots in the sarcoplasmic reticulum (IP3-regulated and Ryanodineregulated) are:

Select one of the following:

  • a) independent of each other;

  • b) one depot with two different channels;

  • c) dependent on the membrane potential.

Explanation

Question 51 of 59

1

What are the elastic properties of muscles?

Select one of the following:

  • a) the ability to stretch;

  • b) the ability to return to initial size after a stretch;

  • c) the ability to contract.

Explanation

Question 52 of 59

1

In the living body all muscles maintain certain level of tension called tonus. During contraction this
tonus will:

Select one of the following:

  • a) increase;

  • b) decrease;

  • c) stay the same

Explanation

Question 53 of 59

1

Why are smooth muscles (SM) called autonomous?

Select one of the following:

  • a) because SM react to external stimuli;

  • b) because excitations can be generated within the SM tissue;

  • c) because SM can remain de-excited for long periods.

Explanation

Question 54 of 59

1

. Smooth muscle contraction is triggered by increased intra-cellular concentration of this type of
ions:

.

Select one of the following:

  • a) K+

  • b) Ca2+;

  • c) Na+

Explanation

Question 55 of 59

1

In the human body, smooth muscles are found in:

Select one of the following:

  • a) most of the internal organs;

  • b) the skeletal muscles;

  • c) the pacemaking tissue of the heart muscle.

Explanation

Question 56 of 59

1

The structural muscle tissue found in arterial walls is of this type:

Select one of the following:

  • a) phasic smooth muscle;

  • b) tonic smooth muscle;

  • c) striated muscle cells working in tandem with tonic smooth muscle cells

Explanation

Question 57 of 59

1

57. Is there a relationship between slow wave membrane potentials and the contractions in smooth
muscle cells?

Select one of the following:

  • a) yes, slow waves are related with tonic contractions;

  • b) yes, slow waves are related with phasic contractions;

  • c) there is no relation between slow waves and contractions.

Explanation

Question 58 of 59

1

What is characteristic about the membrane potential of the stomach?

Select one of the following:

  • a) rhythmic fluctuations with low frequency and below threshold;

  • b) constant potential at rest;

  • c) depolarization reaching threshold once every second.

Explanation

Question 59 of 59

1

In smooth muscle cells, all intra-cellular factors that activate myosin light chain kinase (MLCK)
will cause:

Select one of the following:

  • a) relaxation;

  • b) contraction;

  • c) neither

Explanation

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