Class 9 Muscular System Mock Test (ICSE)

Topics in Muscular System

• Types of muscles
• Major muscles and their location
• Muscle contraction in movement
• Benefits of exercise on the muscular system

Muscular System practice questions with answers

1. Q1Multiple choice·1 mark
   Which type of muscle tissue is striated, involuntary, and found exclusively in the walls of the heart?

   1. (a)Skeletal muscle
   2. (b)Voluntary muscle
   3. (c)Smooth muscle
   4. (d)Cardiac muscle
   Show answer and step marks

   1. Correct option: (d) Cardiac muscle+1

   Answer: (d)
2. Q2Multiple choice·1 mark
   Which of the following substances accumulates in skeletal muscles during prolonged or strenuous physical activity, leading to muscle fatigue?

   1. (a)Glycogen
   2. (b)Carbon dioxide
   3. (c)Lactic acid
   4. (d)Ethanol
   Show answer and step marks

   1. Correct option: (c) Lactic acid+1

   Answer: (c)
3. Q3Short answer·2 marks
   Name the major muscle that forms the rounded contour of the human shoulder and state its main action.
   Show answer and step marks

   1. Name of the muscle: Deltoid.+1
   2. Action: it abducts the arm, raising it sideways away from the body (its front fibres also flex and its rear fibres extend the arm).+1

   Answer: Deltoid; it raises the arm sideways away from the body (abduction).
4. Q4Short answer·2 marks
   State the location and primary action of the Latissimus dorsi muscle.
   Show answer and step marks

   1. Location: It is a broad, flat muscle located in the middle and lower back region.+1
   2. Primary action, any one of: extension of the arm at the shoulder (pulling the arm down and back); adduction of the arm (bringing it towards the body); medial (internal) rotation of the arm; or any other valid action of the muscle, such as pulling the body up in a pull-up.+1

   Answer: Location: the middle and lower back; action: any one of extension, adduction or medial rotation of the arm at the shoulder, or any other valid action of the muscle.
5. Q5Long answer·4 marks
   (a) Differentiate between isotonic and isometric muscle contractions, giving one sporting example for each. [2] (b) Explain briefly how actin and myosin filaments interact during skeletal muscle contraction. [2]
   Show answer and step marks

   1. Isotonic contraction: muscle length changes (shortens or lengthens) while it moves a load.+0.5
   2. Isotonic example, any one of: a biceps curl; push-ups; squats; running; cycling; or any other valid sporting example with joint movement.+0.5
   3. Isometric contraction: muscle develops tension but its length stays the same and no joint movement takes place.+0.5
   4. Isometric example, any one of: holding a plank; a wall sit; holding a handstand; holding the iron-cross position on gymnastic rings; or any other valid sporting example of a static hold.+0.5
   5. Actin and myosin interaction: Myosin heads attach to binding sites on the actin filaments, forming temporary cross-bridges.+1
   6. Sliding mechanism: Myosin pulls the actin filaments toward the center of the sarcomere using energy from ATP, causing the muscle fiber to shorten.+1

   Answer: (a) Isotonic: muscle length changes as it moves a load (e.g. a biceps curl); isometric: tension develops with no change in length and no movement (e.g. holding a plank). (b) Myosin heads attach to actin to form cross-bridges and, using energy from ATP, pull the actin filaments towards the centre of the sarcomere, so the fibre shortens.
6. Q6Long answer·4 marks
   Explain the mechanism of muscle contraction during physical movement by answering the following: (a) Define antagonistic muscles and describe the roles of the biceps and triceps as an antagonistic pair when bending the arm at the elbow joint. [2] (b) Differentiate between isotonic and isometric muscle contractions, giving one sporting example for each type. [2]
   Show answer and step marks

   1. Defined antagonistic muscles as pairs of muscles that work in opposition, where one contracts while the other relaxes.+1
   2. Explained that during elbow flexion, the biceps contracts (agonist) to pull the forearm up, while the triceps relaxes (antagonist).+1
   3. Distinguished isotonic contraction (muscle changes length and causes joint movement) from isometric contraction (muscle tension increases without changing length or causing movement).+1
   4. Isotonic example, any one of: lifting a weight; push-ups; running; cycling; or any other valid sporting example with joint movement.+0.5
   5. Isometric example, any one of: holding a plank; a wall sit; holding a handstand; or any other valid sporting example of a static hold.+0.5

   Answer: (a) Antagonistic muscles are pairs that act in opposition, one contracting while the other relaxes; when the elbow bends, the biceps contracts (agonist) and the triceps relaxes (antagonist). (b) Isotonic: muscle length changes and the joint moves (e.g. lifting a weight); isometric: tension rises without a change in length or movement (e.g. holding a plank).

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