Class 11 : Biology (In English) – Lesson 17: Locomotion and Movement
EXPLANATION & SUMMARY
🌱✨ Introduction
🧠 Movement is one of the fundamental characteristics of living organisms. It refers to a change in body position or a part of the body.
⚙️ Locomotion is a special type of movement that results in a change of location of the organism — like walking, running, flying, or swimming.
🌿 In plants, movement is usually growth-oriented, while in animals, locomotion helps in finding food, shelter, mates, and escaping predators.
💡 Concept:
Movement = any displacement (can be internal or external)
Locomotion = displacement of the entire body
All locomotions are movements, but not all movements are locomotions
🧬 Types of Movement
Organisms exhibit three major types of movements:
1️⃣ Amoeboid Movement
Seen in amoeba, WBCs
Achieved by pseudopodia (cytoplasmic extensions)
Involves cytoplasmic streaming and actin filament rearrangement
✏️ Example: Movement of macrophages during phagocytosis.
2️⃣ Ciliary Movement
Uses tiny hair-like cilia
Found in paramecium, tracheal epithelium, fallopian tubes
Coordinated beating moves fluids or the entire organism
💡 In humans:
➡️ Respiratory tract – clears mucus
➡️ Oviduct – moves ovum toward uterus
3️⃣ Muscular Movement
Involves contraction and relaxation of muscle fibers
Responsible for locomotion in higher animals
Works under neural control
✏️ Seen in limbs, heart, alimentary canal.
🦴 Human Muscular System
🧠 Muscles are specialized contractile tissues derived from mesoderm.
📘 Classified into three main types:
🟢 1️⃣ Skeletal (Striated / Voluntary) Muscles
Attached to bones via tendons
Multinucleated, striated (light and dark bands)
Voluntary control
Function: locomotion, posture, body movement
💪 Examples: Biceps, triceps, quadriceps
🔵 2️⃣ Smooth (Unstriated / Involuntary) Muscles
Found in walls of visceral organs (stomach, intestine, blood vessels)
Uninucleated, non-striated
Involuntary control
Function: movement of food, vessel constriction
🔴 3️⃣ Cardiac Muscles
Found only in heart ❤️
Striated, branched, uninucleated
Involuntary, rhythmic contraction
Function: pumps blood continuously
💡 Concept: All muscle contractions are powered by ATP and regulated by calcium ions (Ca²⁺).
⚙️ Structure of Skeletal Muscle
🧬 Muscle → bundles of muscle fascicles → muscle fibers (cells) → myofibrils
Each myofibril shows alternating dark (A band) and light (I band), giving striated appearance.
📘 Sarcomere = structural & functional unit of contraction
Bound by Z-lines
🔹 Components of a Sarcomere
Band Description
A band Dark band (myosin + overlap with actin)
I band Light band (only actin)
H zone Center of A band (only myosin)
M line Midline of sarcomere
Z line Boundary between sarcomeres
💡 During contraction:
Sarcomere length decreases
I band & H zone shorten, A band constant
🧠 Sliding Filament Theory
🧪 Proposed by Huxley and Niedergerke
⚙️ Explains muscle contraction as sliding of actin filaments over myosin filaments.
🌀 Steps:
1️⃣ Impulse from motor neuron → release of Ca²⁺ from sarcoplasmic reticulum
2️⃣ Ca²⁺ binds troponin, exposes binding sites on actin
3️⃣ Myosin head attaches to actin → forms cross bridge
4️⃣ ATP hydrolysis → myosin pulls actin inward (power stroke)
5️⃣ New ATP breaks cross bridge → cycle repeats
💡 Energy: ATP
💡 Ions: Ca²⁺, Mg²⁺
✏️ Result: Shortening of sarcomere = contraction.
🧬 Neuromuscular Junction
📘 Synapse between motor neuron and muscle fiber
🧠 Impulse → releases acetylcholine (ACh) into synaptic cleft
➡️ Triggers depolarization → contraction
⚙️ AChE (acetylcholinesterase) breaks down ACh to stop contraction.
💪 Types of Muscle Contractions
1️⃣ Isotonic – muscle shortens, movement occurs
2️⃣ Isometric – tension changes, length constant
3️⃣ Tetanic – sustained contraction from rapid stimuli
✏️ Example: Holding weight → isometric; lifting → isotonic.
🦴 Skeletal System
🦴 Framework of bones and cartilage that supports body and aids movement.
📘 Human skeleton:
Axial skeleton – skull, vertebral column, ribs, sternum
Appendicular skeleton – limbs and girdles
🧠 Total bones: 206 in adult
🌿 Axial Skeleton (80 bones)
Skull: 22 bones (8 cranial + 14 facial)
Vertebral column: 26 vertebrae
Ribs: 12 pairs
Sternum: 1
💡 Protects brain, spinal cord, heart, lungs.
💪 Appendicular Skeleton (126 bones)
Pectoral girdle: 4
Pelvic girdle: 2
Limbs: 60 (upper) + 60 (lower)
⚙️ Enables movement and locomotion.
🦵 Limb Bones
🖐️ Upper Limb
Humerus → Radius + Ulna → Carpals → Metacarpals → Phalanges
🦶 Lower Limb
Femur → Tibia + Fibula → Tarsals → Metatarsals → Phalanges
✏️ Longest bone: Femur
💡 Strongest joint: Knee joint
🔩 Joints
📘 Articulation = point of contact between bones
Types (Structural basis):
1️⃣ Fibrous (Immovable) – skull sutures
2️⃣ Cartilaginous (Partially movable) – vertebral joints
3️⃣ Synovial (Freely movable) – limbs (shoulder, knee)
🧪 Synovial joint features:
Synovial fluid (lubrication)
Capsule, ligaments
Articular cartilage
💡 Examples:
Ball & socket: shoulder
Hinge: elbow, knee
Pivot: neck (atlas-axis)
Gliding: wrist
Saddle: thumb
Condyloid: fingers
⚙️ Disorders of Muscles and Bones
1️⃣ Myasthenia gravis – autoimmune; blocks ACh receptors → weakness
2️⃣ Muscular dystrophy – genetic; degeneration of muscles
3️⃣ Tetanus – sustained contraction due to toxin
4️⃣ Osteoporosis – bone thinning (↓ calcium, estrogen)
5️⃣ Arthritis – inflammation of joints
6️⃣ Gout – uric acid accumulation in joints
7️⃣ Fracture – bone breakage
💡 Proper nutrition, exercise, and posture maintain skeletal health.
🌍 Importance of Locomotion
🧠 Enables interaction with environment
⚡ Supports feeding, reproduction, protection
🧬 Maintains organism survival
🌿 In humans, essential for daily activities, sports, and circulation (muscle pump effect)
🌍 Why This Lesson Matters
💪 Explains how the body moves and mechanics of muscles
🧠 Connects anatomy and physiology
⚙️ Foundation for sports medicine, orthopedics, neurobiology
🌍 Highlights importance of calcium, exercise, and posture
📝 Quick Recap
🧠 Movement = body part displacement
🏃 Locomotion = movement + location change
💪 Muscles: skeletal, smooth, cardiac
⚙️ Sarcomere = unit of contraction
🧬 Sliding filament theory: actin slides over myosin
🧠 Ca²⁺ + ATP essential for contraction
🦴 Skeleton: 206 bones; axial + appendicular
🔩 Joints: fibrous, cartilaginous, synovial
⚠️ Disorders: Myasthenia, osteoporosis, arthritis
🌍 Movement vital for life and activity
📘 Summary
Locomotion and movement form the basis of animal activity. Movements can be amoeboid, ciliary, or muscular. In humans, skeletal muscles enable locomotion through contraction based on the sliding filament theory. The skeletal system, with bones and joints, provides structure, support, and leverage. The nervous system and ions like calcium coordinate contraction. Joints permit various movements, while disorders such as arthritis and osteoporosis impair mobility. This system ensures organisms interact with their environment, sustain posture, and perform essential functions.
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QUESTIONS FROM TEXTBOOK
🔵 Question 1. Draw the diagram of a sarcomere of skeletal muscle showing different regions.
🟢 Answer:
🧠 A sarcomere is the functional unit of a myofibril, extending between two Z-lines.
🧬 Regions:
A-band: Dark band with both actin and myosin.
I-band: Light band with actin only.
H-zone: Central part of A-band with myosin only.
M-line: Middle line of H-zone.
Z-line: Boundary of sarcomere.
💡 During contraction: I-band and H-zone shorten; A-band remains constant.
✏️ (Diagram to be drawn showing Z-line, A-band, I-band, H-zone, M-line)
🔵 Question 2. Define sliding filament theory of muscle contraction.
🟢 Answer:
⚙️ Sliding Filament Theory:
Explains muscle contraction due to sliding of thin (actin) filaments over thick (myosin) filaments.
Filaments do not change length, sarcomere shortens.
💡 Powered by ATP hydrolysis and Ca²⁺ ions, forming cross-bridges between actin and myosin.
✔️ Result: Shortening of muscle fibre → contraction.
🔵 Question 3. Describe the important steps in muscle contraction.
🟢 Answer:
🧬 Steps:
Impulse from motor neuron → releases acetylcholine → depolarises sarcolemma.
Ca²⁺ ions released from sarcoplasmic reticulum.
Ca²⁺ binds troponin, shifting tropomyosin, exposing binding sites on actin.
Myosin head binds actin → cross-bridge forms.
ATP hydrolysis → power stroke → filaments slide.
ATP binding detaches myosin head → next cycle begins.
Ca²⁺ reabsorbed → relaxation.
✔️ Requires ATP and Ca²⁺.
🔵 Question 4. Write true or false. If false, change the statement so that it is true.
🟢 Answer:
(a) Actin is present in thin filament — ✔️ True
(b) H-zone of striated muscle fibre represents both thick and thin filaments — ❌ False
➡️ Correct: H-zone has only thick (myosin) filaments.
(c) Human skeleton has 206 bones — ✔️ True
(d) There are 11 pairs of ribs in man — ❌ False
➡️ Correct: There are 12 pairs of ribs.
(e) Sternum is present on the ventral side of the body — ✔️ True
🔵 Question 5. Write the difference between:
🟢 Answer:
(a) 🌿 Actin and Myosin
Feature Actin Myosin
Type Thin filament Thick filament
Composition Actin, tropomyosin, troponin Myosin protein
Function Slides over myosin Cross-bridge formation
(b) 🌸 Red and White muscles
Feature Red Muscle White Muscle
Myoglobin High Low
Mitochondria Many Few
Endurance High Low
Fatigue Resistant Quickly fatigued
(c) 🦴 Pectoral and Pelvic girdle
Feature Pectoral Pelvic
Function Supports forelimbs Supports hindlimbs
Bones Clavicle, scapula Ilium, ischium, pubis
Location Upper trunk Lower trunk
🔵 Question 6. Match Column I with Column II:
Column I Column II
(a) Smooth muscle (iv) Involuntary
(b) Tropomyosin (ii) Thin filament
(c) Red muscle (i) Myoglobin
(d) Skull (iii) Sutures
✔️ Correct matches: (a)-(iv), (b)-(ii), (c)-(i), (d)-(iii)
🔵 Question 7. What are the different types of movements exhibited by the cells of human body?
🟢 Answer:
🌿 Types:
Amoeboid movement – leucocytes, macrophages.
Ciliary movement – lining of trachea, fallopian tubes.
Muscular movement – skeletal muscles, limbs.
✔️ All help in locomotion and internal transport.
🔵 Question 8. How do you distinguish between a skeletal muscle and a cardiac muscle?
🟢 Answer:
Feature Skeletal Muscle Cardiac Muscle
Control Voluntary Involuntary
Nucleus Multinucleated Single nucleus
Intercalated discs Absent Present
Fatigue Rapid Never fatigues
Function Body movement Pumping of blood
🔵 Question 9. Name the type of joint between the following:
🟢 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 → Sutures (fibrous joint)
(f) Between pubic bones in pelvic girdle → Cartilaginous joint
🔵 Question 10. Fill in the blank spaces:
🟢 Answer:
(a) All mammals (except a few) have 7 cervical vertebrae.
(b) The number of phalanges in each limb of human is 14.
(c) Thin filament of myofibril contains 2 ‘F’ actins and two other proteins namely tropomyosin and troponin.
(d) In a muscle fibre, Ca²⁺ is stored in sarcoplasmic reticulum.
(e) 11th and 12th pairs of ribs are called floating ribs.
(f) The human cranium is made of 8 bones.
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OTHER IMPORTANT QUESTIONS FOR EXAMS
(CBSE MODEL QUESTIONS PAPER)
ESPECIALLY MADE FROM THIS LESSON ONLY
🔴 Question 1:
Which protein is responsible for muscle contraction?
🔴1️⃣ Keratin
🟢2️⃣ Actin and Myosin
🟡3️⃣ Collagen
🔵4️⃣ Elastin
🟢 Answer: 2️⃣ Actin and Myosin
🔴 Question 2:
Functional unit of muscle contraction is —
🔴1️⃣ Myofibril
🟢2️⃣ Sarcomere
🟡3️⃣ Muscle fibre
🔵4️⃣ Fascicle
🟢 Answer: 2️⃣ Sarcomere
🔴 Question 3:
Which of the following shows amoeboid movement in humans?
🔴1️⃣ Muscle cells
🟢2️⃣ Leucocytes
🟡3️⃣ RBCs
🔵4️⃣ Neurons
🟢 Answer: 2️⃣ Leucocytes
🔴 Question 4:
Which joint allows movement in all directions?
🔴1️⃣ Hinge joint
🟢2️⃣ Ball and socket joint
🟡3️⃣ Pivot joint
🔵4️⃣ Saddle joint
🟢 Answer: 2️⃣ Ball and socket joint
🔴 Question 5:
Which part of the myofibril disappears during contraction?
🔴1️⃣ A band
🟢2️⃣ H zone
🟡3️⃣ I band
🔵4️⃣ Z line
🟢 Answer: 2️⃣ H zone
🔴 Question 6:
Which ion triggers muscle contraction?
🔴1️⃣ Na⁺
🟢2️⃣ Ca²⁺
🟡3️⃣ K⁺
🔵4️⃣ Mg²⁺
🟢 Answer: 2️⃣ Ca²⁺
🔴 Question 7:
The longest bone in human body is —
🔴1️⃣ Humerus
🟢2️⃣ Femur
🟡3️⃣ Tibia
🔵4️⃣ Radius
🟢 Answer: 2️⃣ Femur
🔴 Question 8:
Which connective tissue joins muscle to bone?
🔴1️⃣ Ligament
🟢2️⃣ Tendon
🟡3️⃣ Cartilage
🔵4️⃣ Fascia
🟢 Answer: 2️⃣ Tendon
🔴 Question 9:
The number of bones in adult human skeleton is —
🔴1️⃣ 200
🟢2️⃣ 206
🟡3️⃣ 210
🔵4️⃣ 208
🟢 Answer: 2️⃣ 206
🔴 Question 10:
Which enzyme hydrolyses ATP during muscle contraction?
🔴1️⃣ ATP synthase
🟢2️⃣ Myosin ATPase
🟡3️⃣ Actinase
🔵4️⃣ Kinase
🟢 Answer: 2️⃣ Myosin ATPase
🔴 Question 11:
Define locomotion.
🟢 Answer:
The voluntary movement of an organism from one place to another is called locomotion (e.g., walking, running).
🔴 Question 12:
Name the three types of muscles in the human body.
🟢 Answer:
1️⃣ Skeletal (Striated) — Voluntary, multinucleated
2️⃣ Smooth (Unstriated) — Involuntary, single nucleus
3️⃣ Cardiac — Involuntary, striated, branched
🔴 Question 13:
Define movement and locomotion. Differentiate between them.
🟢 Answer:
Movement: Change in position of a body part (can be voluntary or involuntary).
Locomotion: Voluntary movement of the entire organism from one place to another.
Feature Movement Locomotion
Scope May be of a part Whole body
Voluntary Can be voluntary/involuntary Always voluntary
Example Beating of heart Walking, running
💡 All locomotions are movements, but all movements are not locomotions.
🔴 Question 14:
What are the different types of movements in animals?
🟢 Answer:
1️⃣ Amoeboid movement:
– In leucocytes; uses pseudopodia.
2️⃣ Ciliary movement:
– In respiratory tract & fallopian tubes; uses cilia.
3️⃣ Muscular movement:
– Due to muscle contraction; e.g., walking, running.
💡 Human body shows all three types of movement.
🔴 Question 15:
Explain the structure of a sarcomere.
🟢 Answer:
Definition: Structural & functional unit of myofibril (between two Z-lines).
Components:
1️⃣ A band (dark): Contains thick filament (myosin).
2️⃣ I band (light): Contains thin filament (actin).
3️⃣ H zone: Central part with only myosin.
4️⃣ Z line: Boundary of sarcomere.
💡 During contraction, H zone shortens, A band remains same.
🔴 Question 16:
Describe the chemical events of muscle contraction.
🟢 Answer:
1️⃣ Nerve impulse → releases Ca²⁺ from sarcoplasmic reticulum.
2️⃣ Ca²⁺ binds to troponin, exposing binding sites on actin.
3️⃣ Myosin head binds to actin → forms cross bridge.
4️⃣ ATP hydrolysis by myosin ATPase → energy for sliding.
5️⃣ Actin filaments slide → sarcomere shortens.
✅ Relaxation when Ca²⁺ returns to SR.
🔴 Question 17:
List the functions of skeleton.
🟢 Answer:
1️⃣ Support: Framework maintaining body shape.
2️⃣ Protection: Vital organs (skull–brain, ribs–heart).
3️⃣ Movement: Bones act as levers with muscles.
4️⃣ Haemopoiesis: Bone marrow forms blood cells.
5️⃣ Mineral storage: Ca, P.
💡 Total 206 bones in adult human.
🔴 Question 18:
Differentiate between axial and appendicular skeleton.
🟢 Answer:
Feature Axial Appendicular
Components Skull, vertebral column, ribs, sternum Limbs & girdles
Bones 80 126
Function Protection & support Movement
Example Ribs Humerus
💡 Together form complete skeleton.
🔴 Question 19:
What are synovial joints? Name their types.
🟢 Answer:
Definition: Freely movable joints with synovial fluid.
Types:
1️⃣ Ball & Socket – Shoulder, hip.
2️⃣ Hinge – Elbow, knee.
3️⃣ Pivot – Atlas-axis joint.
4️⃣ Gliding – Carpals.
5️⃣ Saddle – Thumb joint.
💡 Enable various types of movements.
🔴 Question 20:
Write the differences between red and white muscles.
🟢 Answer:
Feature Red Muscles White Muscles
Myoglobin High Low
Mitochondria Many Few
Endurance High Low
Colour Dark red Pale
Function Sustained activity Quick action
💡 Red = aerobic; White = anaerobic.
🔴 Question 21:
Describe the structure of a typical vertebra.
🟢 Answer:
Components:
1️⃣ Centrum: Main body.
2️⃣ Neural canal: For spinal cord.
3️⃣ Processes: Transverse and spinous for muscle attachment.
Types: Cervical (7), Thoracic (12), Lumbar (5).
💡 Vertebral column provides support & protection.
🔴 Question 22:
List the three types of muscles with their properties.
🟢 Answer:
Type Control Striation Nucleus Function
Skeletal Voluntary Striated Multi Locomotion
Smooth Involuntary Unstriated Single Internal organs
Cardiac Involuntary Striated Single Heartbeat
💡 Cardiac muscles are myogenic & fatigue-resistant.
🔴 Question 23:
Explain the sliding filament theory of muscle contraction.
🟢 Answer:
Concept: Muscle contraction occurs due to sliding of thin (actin) filaments over thick (myosin) filaments.
Steps:
1️⃣ Impulse: Nerve impulse releases Ca²⁺ from sarcoplasmic reticulum.
2️⃣ Exposure: Ca²⁺ binds to troponin, shifts tropomyosin, exposes binding sites on actin.
3️⃣ Cross-bridge: Myosin heads attach to actin → form cross-bridges.
4️⃣ Power stroke: Myosin heads use ATP to pull actin inward → sarcomere shortens.
5️⃣ Detachment: ATP binds again → myosin detaches; cycle repeats.
💡 A band constant, I band & H zone shorten → muscle contracts.
🔴 Question 24:
Describe the structure of human skeleton.
🟢 Answer:
Divisions:
1️⃣ Axial skeleton (80 bones): Skull (22), vertebral column (26), ribs (24), sternum (1), hyoid (1), ear ossicles (6).
2️⃣ Appendicular skeleton (126 bones): Limbs & girdles (pectoral and pelvic).
Functions:
✔️ Support and protection of organs.
✔️ Locomotion with muscles.
✔️ Haemopoiesis in bone marrow.
✔️ Mineral storage (Ca, P).
💡 Total = 206 bones in adult human.
🔴 Question 25:
Explain the structure of a typical myofibril.
🟢 Answer:
Myofibril: Cylindrical structure inside muscle fibre.
Bands:
1️⃣ A band (dark): Thick myosin filaments.
2️⃣ I band (light): Thin actin filaments.
3️⃣ H zone: Central part with only myosin.
4️⃣ Z line: Border between sarcomeres.
Sarcomere: Segment between two Z-lines = functional unit.
💡 Contraction: actin slides over myosin → sarcomere shortens.
🔴 Question 26:
Describe the events of muscle contraction and relaxation.
🟢 Answer:
Contraction:
1️⃣ Impulse from motor neuron → Ca²⁺ released.
2️⃣ Ca²⁺ binds troponin → exposes actin sites.
3️⃣ Myosin binds actin → cross-bridge forms.
4️⃣ ATP hydrolysis → power stroke → filaments slide.
Relaxation:
1️⃣ Ca²⁺ pumped back to sarcoplasmic reticulum.
2️⃣ Tropomyosin covers actin sites.
3️⃣ Cross-bridges detach → muscle returns to rest.
💡 Energy: Provided by ATP; lack of ATP → rigor mortis.
🔴 Question 27:
Explain the structure and functions of synovial joint.
🟢 Answer:
Structure:
– Ends of bones covered with cartilage.
– Enclosed by joint capsule lined with synovial membrane.
– Synovial fluid lubricates and reduces friction.
Functions:
✔️ Free movement in various directions.
✔️ Shock absorption.
✔️ Stability and flexibility.
Examples: Shoulder (ball & socket), elbow (hinge).
🔴 Question 28:
Describe the disorders of the muscular and skeletal system.
🟢 Answer:
1️⃣ Myasthenia gravis: Autoimmune; weak neuromuscular transmission.
2️⃣ Tetany: Low Ca²⁺ → spasms.
3️⃣ Muscular dystrophy: Degeneration of muscles.
4️⃣ Arthritis: Inflammation of joints.
5️⃣ Osteoporosis: Bone weakening due to low calcium.
💡 Balanced diet & exercise prevent many disorders.
🔴 Question 29:
Explain the types and functions of joints in the human body.
🟢 Answer:
1️⃣ Fibrous joints: Immovable (e.g., skull sutures).
2️⃣ Cartilaginous joints: Slightly movable (e.g., vertebrae).
3️⃣ Synovial joints: Freely movable; types:
– Ball & socket (hip)
– Hinge (elbow)
– Pivot (neck)
– Gliding (carpals)
– Saddle (thumb)
💡 Functions: Movement, flexibility, shock absorption.
🔴 Question 30:
Describe the appendicular skeleton and its role.
🟢 Answer:
Components (126 bones):
1️⃣ Pectoral girdle (4): Clavicle & scapula.
2️⃣ Pelvic girdle (2): Hip bones.
3️⃣ Limbs (120):
– Upper limb: Humerus, radius, ulna, carpals, metacarpals, phalanges.
– Lower limb: Femur, tibia, fibula, tarsals, metatarsals, phalanges.
Functions:
✔️ Locomotion and manipulation.
✔️ Attachment of muscles.
✔️ Protection (pelvis → reproductive organs).
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