Chapter 17: Locomotion and Movement Application Questions | biology Class 11 CBSE

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Chapter 17: Locomotion and Movement Application Questions | biology Class 11 CBSE | ByteNotes.in

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 1

Applied Concept

A student observes that when she exercises intensely for a prolonged period, her muscles begin to ache and she feels fatigued. With reference to the chapter, explain the biochemical basis of this observation.

Repeated and prolonged activation of muscles leads to muscle fatigue due to anaerobic breakdown of glycogen stored in muscle fibres.
This anaerobic process results in the accumulation of lactic acid in the muscle tissue.
The lactic acid lowers the pH within the muscle, interfering with the contractile mechanism and causing the muscles to ache and lose their ability to contract efficiently.
If the exercise involved aerobic muscles (red fibres with mitochondria and myoglobin), fatigue would be slower; white fibres, which rely on anaerobic processes, would fatigue faster.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 2

Applied Concept

A patient is diagnosed with myasthenia gravis. The doctor explains that the problem is not with the muscles themselves but with the connection between nerves and muscles. With reference to the chapter, explain how this leads to muscle weakness and paralysis.

Myasthenia gravis is an auto-immune disorder that specifically affects the neuromuscular junction (motor-end plate) — the site where a motor neuron communicates with the muscle fibre's sarcolemma.
Since the junction is damaged, the neurotransmitter acetylcholine cannot effectively generate an action potential in the sarcolemma.
Without a proper action potential, Ca++ is not released from the sarcoplasmic reticulum, the actin active sites remain masked by troponin, and cross bridge formation does not occur — so the muscle cannot contract.
The result is progressive weakening and eventual paralysis of skeletal muscles, even though the muscles and bones are structurally intact.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 3

Applied Concept

An elderly woman suffers a fracture of her femur after a minor fall. Her doctor diagnoses osteoporosis. With reference to the chapter, explain the condition and identify the hormonal change commonly associated with it.

Osteoporosis is an age-related skeletal disorder characterised by a decrease in bone mass, making bones more fragile and susceptible to fractures.
A decreased level of estrogen is identified as a common cause of osteoporosis, which is why it is particularly common in post-menopausal women.
The femur is the longest bone in the human body (part of the lower limb) and bears significant body weight; reduced bone density makes it highly vulnerable to fractures even from minor trauma.
Since the skeletal system's primary functions include supporting the body and protecting internal organs, osteoporosis severely impairs these roles and overall locomotion.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 4

Applied Concept

A biologist is examining a stained cross-section of skeletal muscle under a microscope. She observes alternating dark and light bands. Explain the molecular basis of this banding pattern.

The alternating dark and light bands observed in skeletal muscle are due to the organised distribution of two contractile proteins — actin and myosin — within each myofibril.
The dark bands are called A bands (Anisotropic); they contain thick myosin filaments and the overlapping portions of thin actin filaments. The presence of both thick and thin filaments makes this band denser, hence darker.
The light bands are called I bands (Isotropic); they contain only thin actin filaments (no myosin) and appear lighter because they are less optically dense.
Within the I band, a Z line bisects it; within the A band, an M line and an H zone (containing only thick filaments, no overlap) are also visible. This entire repeating unit between two Z lines is a sarcomere.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 5

Applied Concept

A doctor prescribes calcium supplements to a patient experiencing uncontrolled muscle spasms. With reference to the chapter, explain why calcium supplementation would help this patient.

The condition described — uncontrolled, rapid muscle spasms — matches the description of tetany, which is caused by low Ca++ levels in body fluids.
Calcium ions play a regulatory role in muscle contraction: they bind to troponin subunits on actin filaments to unmask the active myosin-binding sites, allowing controlled cross bridge formation.
When Ca++ levels are abnormally low, this regulatory mechanism is disrupted, leading to uncontrolled, wild contractions (spasms) rather than coordinated, controlled muscle activity.
By restoring normal Ca++ levels through supplementation, the troponin-tropomyosin blocking mechanism resumes normal function, and controlled muscle contraction returns.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 6

Applied Concept

A sprinter and a long-distance marathon runner both use their leg muscles heavily, but in different ways. With reference to the chapter, explain which type of muscle fibres each athlete would predominantly use and why.

A sprinter requires rapid, high-intensity but short-duration bursts of power, which are characteristic of white muscle fibres.
White fibres have a high amount of sarcoplasmic reticulum, depend on anaerobic processes for energy, and have faster reaction times — ideal for explosive sprinting.
A marathon runner requires sustained, low-intensity muscular effort over a long period, which is characteristic of red muscle fibres.
Red fibres are rich in myoglobin and mitochondria, use aerobic respiration to generate ATP efficiently, and are resistant to fatigue — making them ideal for endurance events like marathon running.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 7

Applied Concept

An X-ray reveals that a patient has a fracture at the joint where the humerus meets the pectoral girdle. Identify the specific bones and the type of joint involved, and explain why this joint allows such a wide range of movement.

The joint in question is the shoulder joint, formed between the head of the humerus and the glenoid cavity of the scapula (part of the pectoral girdle).
This is a ball and socket joint — a type of synovial joint where the rounded head of one bone fits into the cup-like depression of another, allowing movement in multiple planes.
Synovial joints are characterised by a fluid-filled synovial cavity between the articulating surfaces, which minimises friction and enables considerable freedom of movement.
The ball-and-socket configuration of the shoulder joint allows the arm to move forward, backward, sideways, and in circular motions — the widest range of movement among all joint types.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 8

Applied Concept

With reference to the mechanism of muscle contraction, explain why muscle relaxation requires energy (ATP) just as much as contraction does.

After the power stroke of muscle contraction, ADP and Pi are released from the myosin head. For the cross bridge to break, a fresh ATP molecule must bind to the myosin head.
This ATP binding causes the myosin head to detach from actin; the ATP is then hydrolysed, allowing the myosin head to return to its high-energy position for the next cycle.
For complete relaxation, Ca++ must be actively pumped back into the sarcoplasmic reticulum against a concentration gradient — an active transport process that requires ATP.
Without ATP, myosin heads remain permanently attached to actin (locked cross bridges), causing irreversible muscle stiffness, as seen in rigor mortis. Thus, ATP is indispensable for both contraction and relaxation.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 9

Applied Concept

A student is asked to explain why the skull bones cannot move relative to each other, while the vertebrae can. Relate your answer to the types of joints involved.

Skull bones are joined by fibrous joints — specifically sutures formed by dense fibrous connective tissue. These joints do not permit any movement between the bones.
The immobility of skull bones is essential for protecting the brain inside the rigid cranium from mechanical damage.
The joints between adjacent vertebrae are cartilaginous joints, where the bones are joined by cartilage (intervertebral discs). These allow limited but important movement, enabling the vertebral column to flex, extend, and rotate.
The limited but essential movement of the vertebral column allows us to bend forward, backward, and sideways, which is impossible with fibrous joints — illustrating how joint type directly determines function.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 10

Applied Concept

A genetics student discovers that a patient's skeletal muscles are progressively degenerating. The patient has no history of auto-immune disease. With reference to the chapter, identify the most likely disorder and explain its basis.

Given that the degeneration is progressive, involves skeletal muscles specifically, and is not auto-immune in origin, the most likely disorder is muscular dystrophy.
Muscular dystrophy is characterised by progressive degeneration of skeletal muscle, and it is mostly caused by a genetic disorder (not an auto-immune condition like myasthenia gravis).
The genetic defect disrupts the normal production of proteins essential for maintaining the structural integrity of muscle fibres, leading to their progressive weakening and degeneration over time.
Unlike myasthenia gravis (which targets the neuromuscular junction) or tetany (low Ca++), muscular dystrophy is intrinsic to the muscle fibre itself, making it progressive and currently very difficult to reverse.

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Chapter 17: Locomotion and Movement | Application Questions

A student observes that when she exercises intensely for a prolonged period, her muscles begin to ache and she feels fatigued. With reference to the chapter, explain the biochemical basis of this observation.

A patient is diagnosed with myasthenia gravis. The doctor explains that the problem is not with the muscles themselves but with the connection between nerves and muscles. With reference to the chapter, explain how this leads to muscle weakness and paralysis.

An elderly woman suffers a fracture of her femur after a minor fall. Her doctor diagnoses osteoporosis. With reference to the chapter, explain the condition and identify the hormonal change commonly associated with it.

A biologist is examining a stained cross-section of skeletal muscle under a microscope. She observes alternating dark and light bands. Explain the molecular basis of this banding pattern.

A doctor prescribes calcium supplements to a patient experiencing uncontrolled muscle spasms. With reference to the chapter, explain why calcium supplementation would help this patient.

A sprinter and a long-distance marathon runner both use their leg muscles heavily, but in different ways. With reference to the chapter, explain which type of muscle fibres each athlete would predominantly use and why.

An X-ray reveals that a patient has a fracture at the joint where the humerus meets the pectoral girdle. Identify the specific bones and the type of joint involved, and explain why this joint allows such a wide range of movement.

With reference to the mechanism of muscle contraction, explain why muscle relaxation requires energy (ATP) just as much as contraction does.

A student is asked to explain why the skull bones cannot move relative to each other, while the vertebrae can. Relate your answer to the types of joints involved.

A genetics student discovers that a patient's skeletal muscles are progressively degenerating. The patient has no history of auto-immune disease. With reference to the chapter, identify the most likely disorder and explain its basis.

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