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

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

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Question 1

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Distinguish between movement and locomotion with one example each.

Movement refers to any change in position of a body part or organism, such as the beating of cilia in the trachea.
Locomotion is a specific type of voluntary movement that results in a change of place or location, such as walking or swimming.
The key relationship is that all locomotions are movements, but not all movements are locomotions.

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Question 2

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State two functions of ciliary movement in the human body.

Coordinated movement of cilia in the trachea helps remove dust particles and foreign substances inhaled with atmospheric air.
Ciliary movement facilitates the passage of ova (eggs) through the female reproductive tract.
Ciliary movement occurs in most internal tubular organs that are lined by ciliated epithelium.

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Question 3

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What is amoeboid movement? Name two types of cells in the human body that exhibit it.

Amoeboid movement is a type of movement effected by pseudopodia formed by the streaming of protoplasm, similar to the movement seen in Amoeba.
Cytoskeletal elements like microfilaments are also involved in amoeboid movement.
Macrophages and leucocytes (white blood cells) in the blood are specialised cells of the human body that exhibit amoeboid movement.

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Question 4

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List the four special properties of muscle tissue.

Excitability is the ability of a muscle to receive and respond to stimuli.
Contractility is the ability of muscle to shorten in length upon stimulation.
Extensibility and elasticity are the properties allowing muscle to stretch when a force is applied and return to its original length thereafter.

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Question 5

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Cardiac muscles are described as both striated and involuntary. Justify this statement.

Cardiac muscles are striated because their cells assemble in a branching pattern and show striations similar to skeletal muscle when viewed under a microscope.
They are involuntary because the nervous system does not directly control their activities — they contract rhythmically on their own.
This combination of being striated yet involuntary makes cardiac muscle unique compared to either skeletal (striated, voluntary) or smooth (non-striated, involuntary) muscle.

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Question 6

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What is a sarcomere? Identify the bands and lines present within one sarcomere.

A sarcomere is the functional unit of muscle contraction, defined as the portion of a myofibril between two successive Z lines.
It contains a central dark A band (Anisotropic) composed of thick myosin filaments, and two half I bands (Isotropic) of thin actin filaments on either side.
The Z line bisects each I band and anchors thin filaments, while the H zone is the central part of the A band not overlapped by thin filaments in the resting state.

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Question 7

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Describe the role of troponin in the resting state of a muscle fibre.

Troponin is a complex protein that is distributed at regular intervals on the tropomyosin filaments along the actin filament.
In the resting state, a subunit of troponin masks the active binding sites for myosin on the actin filaments, thereby preventing cross bridge formation.
This masking ensures that muscle contraction does not occur in the absence of a neural signal and the consequent release of calcium ions.

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Question 8

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What is the neuromuscular junction? What neurotransmitter is released at this junction?

The neuromuscular junction (or motor-end plate) is the junction formed between a motor neuron and the sarcolemma of a muscle fibre.
When a neural signal reaches this junction, it triggers the release of the neurotransmitter acetylcholine.
Acetylcholine then generates an action potential in the sarcolemma, which spreads through the muscle fibre and initiates the process of contraction.

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Question 9

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What happens to the I band and A band during muscle contraction? Give reason.

During muscle contraction, the I bands get reduced (shorten) because the thin actin filaments slide towards the centre of the A band, reducing the portion of I band visible.
The A bands retain their original length because the thick myosin filaments themselves do not shorten; only the thin filaments slide over them.
This differential change in band size is a key feature of the sliding filament theory and occurs at the level of each sarcomere.

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Question 10

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How does muscle fatigue occur? What metabolic process causes it?

Muscle fatigue occurs when muscles are repeatedly activated and fail to contract efficiently.
It results from the accumulation of lactic acid in the muscle tissue due to anaerobic breakdown of glycogen during intense or prolonged activity.
The accumulation of lactic acid lowers the pH of the muscle environment, interfering with the contractile mechanism and causing a decline in force generation.

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Question 11

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Differentiate between red fibres and white fibres of muscle on the basis of myoglobin and energy metabolism.

Red fibres have a high myoglobin content, giving them a reddish colour, and are rich in mitochondria; they are aerobic and suited for sustained activity.
White fibres have very little myoglobin, appear pale or whitish, have fewer mitochondria but a high amount of sarcoplasmic reticulum.
White fibres depend on anaerobic processes for energy, making them suited for rapid but short-duration contractions.

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Question 12

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State the role of calcium ions (Ca++) in initiating muscle contraction.

When an action potential reaches the muscle fibre via the sarcolemma, it causes the release of Ca++ from the sarcoplasmic reticulum into the sarcoplasm.
The increased Ca++ level leads to binding of calcium with a subunit of troponin on the actin filaments, removing the masking of active sites for myosin.
Once the active sites on actin are exposed, the myosin head binds to them (using ATP energy) to form cross bridges, initiating the process of contraction.

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Question 13

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How many bones make up the human skull? Distinguish between cranial and facial bones.

The human skull is composed of a total of 22 bones.
Cranial bones are 8 in number and form the hard protective outer covering (cranium) for the brain.
Facial bones are 14 in number and form the front part of the skull, constituting the facial region.

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Chapter 17: Locomotion and Movement | Short Questions

Distinguish between movement and locomotion with one example each.

State two functions of ciliary movement in the human body.

What is amoeboid movement? Name two types of cells in the human body that exhibit it.

List the four special properties of muscle tissue.

Cardiac muscles are described as both striated and involuntary. Justify this statement.

What is a sarcomere? Identify the bands and lines present within one sarcomere.

Describe the role of troponin in the resting state of a muscle fibre.

What is the neuromuscular junction? What neurotransmitter is released at this junction?

What happens to the I band and A band during muscle contraction? Give reason.

How does muscle fatigue occur? What metabolic process causes it?

Differentiate between red fibres and white fibres of muscle on the basis of myoglobin and energy metabolism.

State the role of calcium ions (Ca++) in initiating muscle contraction.

How many bones make up the human skull? Distinguish between cranial and facial bones.

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