Target DPP Test

1.

The combination of a neuron and the muscle fiber it associates with is called a/an.
1. fascicle
2. motor end plate
3. motor unit
4. myoneural junction

2.

Sliding filament theory can be best explained as
1. when myofilaments slide pass each other actin filaments shorten while myosin filament do not shorten
2. actin and myosin filaments shorten and slide pass each other
3. actin and myosin filaments do not shorten but rather slide pass each other
4. when myofilament slide pass each other myosin filament shorten while actin filaments do not shorten

3.

ATP provides energy for muscle contraction by allowing for:
1. An action potential formation in the muscle cell
2. Cross-bridge attachment of myosin to actin
3. Cross-bridge detachment of myosin from actin
4. Release of Ca⁺² from sarcoplasmic reticulum

4.

A motor unit is best described as:
(1) All the nerve fibres and muscle fibres in a single muscle bundle
(2) One muscle fibre and its single nerve fibre
(3) A single motor neuron and all the muscle fibres that it innervates
(4) It is the neuron which carries the message from muscle to CNS

5.

The energy for muscle contraction is most directly obtained from:
(1) Phosphocreatine
(2) ATP
(3) Anaerobic respiration
(4) Aerobic respiration

6.

Go through the following diagram describing muscle contraction:

Now identify A to E:
(1) A - Cross bridge, B - Cross bridge formation, C - Breaking of cross bridge, D - Sliding (rotation), E - ATP
(2) A - Cross bridge, B - Cross bridge formation, C - Sliding / rotation, D - Breaking of cross bridge, E - ATP
(3) A - Cross bridge, B - Breaking of Cross bridge, C - sliding / rotation, D - Cross bridge formation, E - AMP
(4) A - Cross bridge, B - Cross bridge formation, C - Sliding / rotation, D - ADP, E - Breaking of cross bridge

7.

The cross-bridge formation actually involves
1. ATP hydrolysis
2. Binding of Myosin head to the exposed active sites for myosin
3. Both A and B
4. None of these

8.

What masks the active sites for myosin head present on the actin myofilaments?
1. Light meromyosin
2. Heavy meromyosin
3. G – actin
4. Troponin

9.

The central part of the thick myofilaments, not overlapped by thin filaments, is called the:
1. Z line
2. M line
3. I band
4. H zone

10.

Sliding filament theory can be best explained as
1. when myofilaments slide pass each other actin filaments shorten while myosin filament do not shorten
2. actin and myosin filaments shorten and slide pass each other
3. actin and myosin filaments do not shorten but rather slide pass each other
4. when myofilament slide pass each other myosin filament shorten while actin filaments do not shorten

11.

The binding of calcium to troponin actually indicates
1. Unmasking of Myosin binding site over meromyosin
2. Unmasking of Myosin binding site over actin
3. Unmasking of actin binding site over myosin
4. Unmasking of actin binding site over tropolosin

12.

Calcium is important in skeletal muscle contraction because it
(1) Binds to troponin to remove the masking of active sites on actin for myosin.
(2) Activates the myosin ATPase by binding to it.
(3) Prevents the formation of bonds between the myosin cross bridges and the actin filament.
(4) Detaches the myosin head from the actin filament.

13.

During muscle contraction, which of the following does not occur?
(1) No change in length of anisotrophic band
(2) Decrease in length of isotropic band
(3) No change in length of A band
(4) Decrease in length of actin myofilaments

14.

Contraction of muscle fibre takes place by the
sliding of :-
1. Thin filaments over the actin filaments.
2. Thick filaments over the thin filaments.
3. Thin filaments over the thick filaments.
4. Thick filaments over the myosin filaments.

15.

Read the following statements (A-D):-
(A) A neural signal reaching the neural muscular junction releases adrenalin.
(B) Many monomeric proteins called meromyosin constitute one thin filament.
(C) A complex protein troponin is distributed at irregular intervals on the tropomyosin.
(D) During shortening of muscle, the I-bands get reduced.
How many of the above statements are true?
1. Four
2. One
3. Three
4. Two

16.

The source of energy that can be directly used by muscle for contraction is:
1. GTP
2. ATP
3. Creatine phosphate
4. Glucose

17.

During muscle contraction, the event shown in the following diagram describes:

1. cross bridge detachment
2. the power stroke or working stroke
3. cross bridge formation
4. cocking of myosin head

18.

The following events occur during a reflex response to a person placing a hand on a hot object.
1 Myosin binding sites on actin filaments uncovered.
2 ADP and phosphate ion released from myosin head.
3 Sodium voltagegated channels open.
4 Myosin head detaches from the binding sites on actin.
5 Calcium ions released by sarcoplasmic reticulum.
Which of the following options places four of these events in the correct order (from left to right)?
1. 3, 5, 4, 2
2. 5, 2, 1, 4
3. 1, 2, 4, 3
4. 5, 1, 2, 4

19.

Active transport of ${Ca}^{2 +}$ ions into the sarcoplasmic
reticulum will not be associated with
(1) Return of Z-lines to their original position
(2) lncrease in the l-band of sarcomere
(3) Decreases in width of O-bands of a sarcomere
(4) Decreases in the width of H-zone of a
sarcomere

20.

Which of the following properties in not applicable
to the myosin filaments?
(1) Slide into H-zone during muscle contraction
(2) Cross bridges present, hence have rough
surface
(3) Fewer than actin filaments
(4) Found only in the A-band of sarcomere

21.

Motor neuron along with muscle fibers are connected & constitute:-
1. Motor end plate
2. Motor unit
3. Neuromuscular junction
4. Motor reticular junction

22.

Consider the following events in the excitation –
contraction coupling leading to muscle contraction:
1. Calcium is released from the sarcoplasmic reticulum into the cytoplasm.
2. Myosin forms a cross-bridge onto the actin filaments active site, and pull the actin toward the center of the sarcomere An action potential is generated across the membrane of the myocyte in response to the binding of acetylcholine to nicotinic receptors.
3. Acetylcholine is released by the motor neuron into the neuromuscular junction.
4. Calcium ions released from the sarcoplasmic reticulum bind to Troponin C on actin filaments, which subsequently leads to tropomyosin being physically moved aside to uncover cross-bridge binding sites on the actin filament.
5. An action potential is generated across the membrane of the myocyte in response to the binding of acetylcholine to nicotinic receptors.
The correct sequence of events would be:
(1) 3, 5, 1, 4, 2
(2) 1, 2, 3, 4, 5
(3) 3, 1, 5, 2 , 4
(4) 5, 3, 1, 4, 2

23.

What happens to the Calcium ion ( ${Ca}^{2 +}$ ) when they are removed from troponin after the muscle contraction?
(1) It diffuses through the cell membrane and into the extracellular fluid.
(2) It is reabsorbed by active transport into the sarcoplasmic reticulum.
(3) It is taken up into the neuromuscular cleft.
(4) It is bound by tropomyosin until it is needed again.

24.

What is the sarcoplasmic reticulum?
(1) The functional unit of contraction of a muscle cell.
(2) The contractile protein fibrils that make up a muscle cell.
(3) A network of mitochondria that are linked together in muscle cells.
(4) A membrane network that regulates ${Ca}^{+ +}$ uptake and release in muscle cells.

25.

The immediate source of energy for muscle contraction is:
(1) ATP
(2) Creatine phosphate
(3) Glycogen
(4) Lactic acid

26.

During muscular contraction, which of the following events occur?

(a)	'H' zone disappears
(b)	'A' band widens
(c)	'I' band reduces in width
(d)	Myosin hydrolyzes ATP, releasing the ADP and Pi
(e)	Z-lines attached to actins are pulled inwards

Choose the correct answer from the options given below:
1. (b), (c), (d), (e) only
2. (b), (d), (e), (a) only
3. (a), (c), (d), (e) only
4. (a), (b), (c), (d) only

27. During the mechanism of muscle contraction, following events occur
(I) Myosin head activated by ATP hydrolysis binds to exposed active sites to form cross bridge
(II) Pulling of actin filaments towards A-band leads to contraction
(III) Acetylcholine is released at neuromuscular junction which generate action potential
(IV) Release of Ca⁺² ions from SR , binds to subunit troponin of actin filaments
Which of the following sequence of above events is correct ?
1. (I) , (II) ,(III) , (IV )
2. (III) , (IV) , (II) , (I)
3. (III) , (IV) , (I) , (II)
4. (III) , (II) , (IV) , (I)

28.

The calcium ions released in sarcoplasm will bind to:

1.	Tropomyosin	2.	Troponin
3.	Actin	4.	Meromyosin

29. The relaxation of muscle after contraction is related to:
1. Hydrolysis of ATP by the myosin head
2. binding of calcium ions to Troponin C
3. Pumping of calcium ions back to the sarcoplasmic cisternae
4. Release of acetylcholine at the neuro-muscular junction

30. Consider the following statements with respect to mechanism of muscle contraction

(a)	Binding of calcium with the subunit of tropomyosin removes the masking of active sites for myosin
(b)	Z-lines move towards the centre of ‘H’ zone
(c)	Cross bridge is formed by utilising the energy from hydrolysis of ATP
(d)	H-zone disappears when a muscle fibre is maximally contracted

Select the option with the correct statement
1. a and c only
2. b and d only
3. a, c and d
4. b, c and d

31. Muscle fatigue is due to
1. Low glucagon in muscle fibres
2. High lactic acid in muscle fibres
3. Slow ATPase activity
4. Adequate supply of ATP

32. Contraction of a skeletal muscle fibre takes place by:

1.	shortening of both actin and myosin myofilaments
2.	shortening of actin and lengthening of myosin myofilaments
3.	the sliding of the thin filaments over the thick filaments
4.	the sliding of the thick filaments over the thin filaments

33. A skeletal muscle motor unit is best described as:
1. a section of myofibrils from Z lines to Z lines
2. one nerve fiber and all the muscle fibers innervated by that nerve fiber
3. all of the nerves that unite to make a whole muscle contract
4. all of the fascicles innervated by several neurons

34. Calcium released into the sarcoplasm during muscle contraction:

1.	binds to the actin and myosin and makes them work together.
2.	breaks apart ATP to ADP and P.
3.	removes the tropomyosin block.
4.	causes the release of acetylcholine.

35. Select the true statement
1. A band is present in the middle of sarcomere
2. H zone is present in the middle of A-band
3. M line is present in the middle of H-zone
4. All of these

36. Arrange the given events in the correct chronological sequence of their occurrence [earliest to last] in which they occur during a single stimulation of a skeletal muscle.
A. active sites on actin myofilament are exposed
B. actin myofilament slides over myosin myofilament
C. Ca²⁺ ion binds to troponin
D. myosin heads move
E. cross bridges form
1. E – A – C – D - B
2. A – C – E – D - B
3. C – A – E – D - B
4. C – E – A – D - B

37. During the contraction of a skeletal muscle, calcium ions released from the sarcoplasmic reticulum bind with:

1.	F actin	2.	G actin
3.	troponin	4.	tropomyosin

38. A motor unit is composed of:

1.	a motor neuron and all of the skeletal muscle fibers innervated by the neuron's axon terminals.
2.	all motor neurons and all of the skeletal muscle fibers innervated by them in a muscle.
3.	a motor neuron and one skeletal muscle fiber innervated by the neuron.
4.	a motor neuron and a sensory neuron.

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