AHSEC (ASSEB) Class 11 Biology Chapter 17 Solutions – Locomotion and Movement | Assam Eduverse
Chapter Overview:
Assam Eduverse provides comprehensive, accurate, and student-friendly solutions for Class 11 Biology (AHSEC / ASSEB) – Unit V: Human Physiology, Chapter 17 – Locomotion and Movement. These well-structured solutions cover all intext questions, exercise questions, and multiple-choice questions (MCQs) with clear explanations, helping students build a strong conceptual understanding and excel in exam preparation.
Chapter 17 – Locomotion and Movement explains the structure and functioning of the human musculoskeletal system, which enables movement and locomotion. Students learn about bones, joints, muscles, and their types, structure, and functions, along with the mechanism of muscle contraction. The chapter also discusses types of movements, locomotor adaptations, and the coordinated role of bones and muscles in movement, helping students understand how the body achieves mobility and physical activity.
Assam Eduverse’s Class 11 Biology Solutions are written in simple, exam-oriented, and easy-to-understand language, ensuring better clarity, quick learning, and strong academic performance. These reliable solutions help students master locomotion and movement, understand musculoskeletal functions, and excel in AHSEC / ASSEB Biology exams with confidence and conceptual clarity.
AHSEC (ASSEB) Class 11 Biology Chapter 17 : Locomotion and Movement Solutions & Question Answers
EXERCISES
Q1. Draw the diagram of a sarcomere of skeletal muscle showing different regions.
Answer: The sarcomere is the functional unit of a myofibril, present between two successive Z lines. In a relaxed state, it includes:
- Z line: A thin elastic line that bisects the I-band. Thin filaments are attached here.
- I band (Isotropic band): The light band containing only thin actin filaments.
- A band (Anisotropic band): The dark band containing thick myosin filaments and overlapping actin filaments. It is bisected by the M line.
- H zone: The central lighter region of the A band containing only myosin filaments.
Thus, a sarcomere extends from one Z line to the next and represents the contractile unit of the muscle fibre.
Q2. Define sliding filament theory of muscle contraction.
Answer: The sliding filament theory explains how muscles contract. According to this theory, during contraction, the thin actin filaments slide over the thick myosin filaments. This sliding shortens the sarcomere length, resulting in the overall shortening of the muscle fibre without changing the length of the filaments themselves.
Q3. Describe the important steps in muscle contraction.
Answer: The process of muscle contraction starts with a neural signal and follows these steps:
- Signal and Calcium Release: A motor neuron sends a signal to the neuromuscular junction, releasing acetylcholine. This generates an action potential in the sarcolemma, causing the sarcoplasmic reticulum to release calcium ions into the sarcoplasm.
- Activation of Actin: The calcium ions bind to troponin on the actin filaments, exposing the binding sites for myosin.
- Cross Bridge Formation: The myosin heads, using energy from ATP hydrolysis, attach to the exposed sites on actin, forming cross bridges.
- Sliding (Power Stroke): The myosin heads pull the actin filaments toward the centre of the A band, shortening the sarcomere.
- Cross Bridge Breaking and Relaxation: A new ATP molecule binds to the myosin head, causing it to detach from actin. When calcium ions are pumped back into the sarcoplasmic reticulum, the actin sites are masked again, and the muscle relaxes.
Q4. Write true or false. If false, change the statement so that it is true.
(a) Actin is present in thin filament
(b) H-zone of striated muscle fibre represents both thick and thin filaments.
(c) Human skeleton has 206 bones.
(d) There are 11 pairs of ribs in man.
(e) Sternum is present on the ventral side of the body
Answer:
(a) Actin is present in thin filament → True
(b) H-zone of striated muscle fibre represents both thick and thin filaments → False. Correct statement: H-zone represents the central region of the thick myosin filaments not overlapped by thin filaments.
(c) Human skeleton has 206 bones → True
(d) There are 11 pairs of ribs in man → False. Correct statement: There are 12 pairs of ribs in man.
(e) Sternum is present on the ventral side of the body → True
Q5. Write the difference between:
(a) Actin and Myosin
(b) Red and White muscles
(c) Pectoral and Pelvic girdle
Answer:
(a) Actin and Myosin
| Feature | Actin (Thin Filament) | Myosin (Thick Filament) |
|---|---|---|
| Structure | Made of two F-actins, tropomyosin, and troponin. | Made of many monomeric proteins called meromyosins. |
| Bands | Forms the I band and overlaps partly into the A band. | Forms the core of the A band. |
| Function | Has active sites that myosin heads attach to during contraction. | Myosin heads act as ATPase enzymes and pull actin filaments during contraction. |
(b) Red and White Muscles
| Feature | Red Muscle Fibres | White Muscle Fibres |
|---|---|---|
| Myoglobin | High, giving reddish colour. | Low, giving whitish appearance. |
| Mitochondria | Abundant. | Fewer. |
| Energy Production | Aerobic (uses oxygen). | Anaerobic (depends on glycogen breakdown). |
| Sarcoplasmic Reticulum | Normal amount. | Large amount. |
(c) Pectoral and Pelvic Girdle
| Feature | Pectoral Girdle (Shoulder) | Pelvic Girdle (Hip) |
|---|---|---|
| Bones | Each half has a clavicle and scapula. | Each half consists of a coxal bone. |
| Composition | Scapula is flat and triangular; clavicle is slender. | Each coxal bone is formed by fusion of ilium, ischium, and pubis. |
| Articulation | Attaches upper limb (humerus) to axial skeleton via glenoid cavity. | Attaches lower limb (femur) to axial skeleton via acetabulum. |
| Ventral Junction | The halves are separated by the sternum. | The halves meet ventrally at the pubic symphysis. |
Q6. Match Column I with Column II:
(a) Smooth muscle → Involuntary
(b) Tropomyosin → Thin filament
(c) Red muscle → Myoglobin
(d) Skull → Sutures
Q7. What are the different types of movements exhibited by the cells of the human body?
Answer: The cells of the human body show three main types of movements:
- Amoeboid Movement: Found in leucocytes and macrophages, using pseudopodia formed by streaming of cytoplasm.
- Ciliary Movement: Seen in ciliated epithelia of the trachea (to remove dust) and in the female reproductive tract (to move ova).
- Muscular Movement: Caused by the contraction of muscle tissues for moving limbs, jaws, and other body parts.
Q8. How do you distinguish between a skeletal muscle and a cardiac muscle?
| Feature | Skeletal Muscle | Cardiac Muscle |
|---|---|---|
| Location | Attached to the skeleton. | Found in the heart wall. |
| Appearance | Striated (striped). | Striated (striped). |
| Regulation | Voluntary control. | Involuntary control. |
| Structure | Long, cylindrical fibres arranged parallelly. | Short, branching fibres interconnected by intercalated discs. |
| Function | Helps in body movement and posture. | Enables rhythmic contraction and pumping of blood. |
Q9. Name the type of joint between the following:(a) atlas/axis
(b) carpal/metacarpal of thumb
(c) between phalanges
(d) femur/acetabulum
(e) between cranial bones
(f) between pubic bones in the pelvic girdle
Answer:
(a) Atlas/axis → Pivot joint
(b) Carpal/metacarpal of thumb → Saddle joint
(c) Between phalanges → Hinge joint
(d) Femur/acetabulum → Ball and socket joint
(e) Between cranial bones → Fibrous joint (sutures)
(f) Between pubic bones in the pelvic girdle → Cartilaginous joint (pubic symphysis)
Q10. Fill in the blank spaces:
(a) All mammals (except a few) have __________ cervical vertebra.
(b) The number of phalanges in each limb of human is __________
(c) Thin filament of myofibril contains 2 ‘F’ actins and two other proteins namely
__________ and __________.
(d) In a muscle fibre Ca++ is stored in __________
(e) __________ and __________ pairs of ribs are called floating ribs.
(f) The human cranium is made of __________ bones.
Answer:
(a) All mammals (except a few) have seven cervical vertebrae.
(b) The number of phalanges in each limb of humans is 14.
(c) The thin filament of a myofibril contains two F-actins, tropomyosin, and troponin.
(d) In a muscle fibre, Ca²⁺ is stored in the sarcoplasmic reticulum.
(e) The 11th and 12th pairs of ribs are called floating ribs.
(f) The human cranium is made up of 8 bones.
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