Mnemonics Locomotion & Movement - Biology Class 11 - NEET PDF Download
Locomotion and Movement is a high-yield chapter for competitive exams, involving detailed study of skeletal system, muscular system, muscle contraction mechanism, and movement disorders. This chapter requires memorization of bone names, muscle types, protein structures, and physiological processes. Mnemonics simplify recall of complex terminology, sequences, and classifications essential for quick revision and exam performance.
1. Skeletal System Components
The human axial and appendicular skeleton contains 206 bones. Specific bone counts and locations are frequently tested.
Bone Count Details : Axial Skeleton (Summary)
| Part | Number of Bones |
|---|---|
| Skull (Cranial 8 + Facial 14) | 22 |
| Ear ossicles (3 × 2) | 6 |
| Hyoid | 1 |
| Vertebral column | 26 |
| Ribs (12 pairs) | 24 |
| Sternum | 1 |
| Total Axial Skeleton | 80 |
Bone Count Details : Appendicular Skeleton (Summary)
Pectoral Girdle
- Clavicle × 2
- Scapula × 2
Total = 4
Upper Limbs (each limb = 30 bones)
- Humerus - 1
- Radius - 1
- Ulna - 1
- Carpals - 8
- Metacarpals - 5
- Phalanges - 14
Both upper limbs = 60
Pectoral Girdle (4)
┌──────┴──────┐
Upper Limb (30) Upper Limb (30)
Pelvic Girdle
Hip bones × 2
Total = 2
Lower Limbs (each limb = 30 bones)
- Femur - 1
- Patella - 1
- Tibia - 1
- Fibula - 1
- Tarsals - 7
- Metatarsals - 5
- Phalanges - 14
Both lower limbs = 60
Total Appendicular Skeleton : 4 + 60 + 2 + 60 = 126 bones
Pelvic Girdle (2)
┌──────┴──────┐
Lower Limb (30) Lower Limb (30)
1.1 Axial Skeleton Components
Mnemonic: "SCVRSS" (Skull, Cranium, Vertebrae, Ribs, Sternum, Sacrum)
- S = Skull (22 bones: 8 cranial + 14 facial)
- C = Cranium (8 bones)
- V = Vertebral column (26 bones)
- R = Ribs (24 bones: 12 pairs)
- S = Sternum (1 bone)
- S = Sacrum (part of vertebral column)
1.2 Number of Vertebrae
Mnemonic: "Breakfast at 7, Lunch at 12, Dinner at 5, Sleep at 5, 4 get fused"
- 7 = Cervical vertebrae (C1-C7)
- 12 = Thoracic vertebrae (T1-T12)
- 5 = Lumbar vertebrae (L1-L5)
- 5 = Sacral vertebrae (fused into sacrum)
- 4 = Coccygeal vertebrae (fused into coccyx)
Total vertebrae: 7 + 12 + 5 + 5 + 4 = 33 (but counted as 26 due to fusion)
1.3 Ribs Classification
Mnemonic: "True 7, False 5 (3 + 2)"
- True ribs: First 7 pairs (attach directly to sternum via costal cartilages)
- False ribs: Next 3 pairs (8-10, attach indirectly to sternum)
- Floating ribs: Last 2 pairs (11-12, do not attach to sternum)
1.4 Appendicular Skeleton Components
Mnemonic: "Each Limb Has 30, Girdles Add 4"
- Pectoral girdle: 2 bones per side (clavicle + scapula) = 4 total
- Upper limbs: 30 bones per arm × 2 = 60 bones
- Pelvic girdle: 2 coxal bones (each formed by fusion of ilium, ischium, pubis)
- Lower limbs: 30 bones per leg × 2 = 60 bones
- Total appendicular skeleton: 126 bones
1.5 Bones in Hand and Foot
Mnemonic: "Some Criminals Make Police Tired" (for hand bones)
- S = Scaphoid (carpal)
- C = Capitate (carpal)
- M = Metacarpals (5 bones)
- P = Phalanges (14 bones: 2 in thumb, 3 in each finger)
- T = Total carpals (8 bones)
Total hand bones per side: 8 carpals + 5 metacarpals + 14 phalanges = 27 bones
Mnemonic: "Tall Teachers Must Plan" (for foot bones)
- T = Tarsals (7 bones)
- T = Talus (largest tarsal)
- M = Metatarsals (5 bones)
- P = Phalanges (14 bones: 2 in big toe, 3 in each toe)
Total foot bones per side: 7 tarsals + 5 metatarsals + 14 phalanges = 26 bones
2. Types of Joints
Joints are classified based on structure and degree of movement. This classification appears frequently in structural questions.
2.1 Structural Classification of Joints
Mnemonic: "FCS" (Fibrous, Cartilaginous, Synovial)
- F = Fibrous joints (immovable, e.g., sutures in skull)
- C = Cartilaginous joints (slightly movable, e.g., vertebrae, pubic symphysis)
- S = Synovial joints (freely movable, e.g., knee, elbow, shoulder)
2.2 Types of Synovial Joints
Mnemonic: "Beautiful People Have Perfectly Smooth Bodies"
- B = Ball and socket joint (shoulder, hip - multiaxial movement)
- P = Pivot joint (atlas-axis vertebrae - rotational movement)
- H = Hinge joint (elbow, knee - uniaxial movement)
- P = Plain/Gliding joint (carpal bones - limited gliding)
- S = Saddle joint (carpometacarpal joint of thumb - biaxial movement)
- B = (Ellipsoid/Condyloid joint - wrist joint - biaxial movement)
3. Types of Muscles
Three types of muscles exist based on structure and function. Muscle type identification is a frequent exam question.
3.1 Muscle Types Classification
Mnemonic: "SSC" (Skeletal, Smooth, Cardiac)
- S = Skeletal muscle (striated, voluntary, multinucleated)
- S = Smooth muscle (non-striated, involuntary, uninucleated, spindle-shaped)
- C = Cardiac muscle (striated, involuntary, uninucleated, branched with intercalated discs)
3.2 Skeletal Muscle Structure Components
Mnemonic: "My Friend Makes Sandwiches" (Hierarchy from large to small)
- M = Muscle (whole organ)
- F = Fascicle (bundle of muscle fibers)
- M = Muscle fiber/Myofiber (single muscle cell)
- M = Myofibril (contractile unit inside fiber)
- S = Sarcomere (functional unit of myofibril)
4. Sarcomere Structure and Bands
The sarcomere is the functional unit of muscle contraction. Understanding its bands and zones is critical for contraction mechanism questions.
4.1 Parts of Sarcomere
Mnemonic: "A IZzy HMan"
- A = A band (dark band, contains entire length of thick filament)
- I = I band (light band, contains only thin filament)
- Z = Z line (boundary of sarcomere, bisects I band)
- H = H zone (central part of A band with only thick filament)
- M = M line (middle of H zone, holds thick filaments)
4.2 Changes During Muscle Contraction
Mnemonic: "I & H Shrink, A Stays"
- I band: Decreases in length (thin filaments slide inward)
- H zone: Decreases in length (thick and thin filaments overlap more)
- A band: Remains constant (length of thick filament unchanged)
- Sarcomere: Shortens overall (distance between Z lines reduces)
Trap Alert: A band does NOT shorten during contraction-only I band and H zone shorten.
5. Contractile Proteins in Muscle
Muscle contraction involves interaction between thick and thin filaments composed of specific proteins.
5.1 Thick Filament Protein
Mnemonic: "Thick = Myosin"
- Myosin: Motor protein with head and tail region
- Myosin head has ATPase activity and actin-binding site
- Approximately 300 myosin molecules form one thick filament
5.2 Thin Filament Proteins
Mnemonic: "ATT" (Actin, Tropomyosin, Troponin)
- A = Actin (main structural protein, globular G-actin polymerizes into F-actin)
- T = Tropomyosin (rod-shaped protein, covers myosin-binding sites on actin in resting state)
- T = Troponin (complex of 3 subunits: TnT, TnI, TnC; regulates contraction)
5.3 Troponin Subunits
Mnemonic: "TIC" (TnT, TnI, TnC)
- TnT: Binds to Tropomyosin
- TnI: Inhibits binding of myosin to actin (inhibitory subunit)
- TnC: Binds to Calcium ions (Ca²⁺)
Trap Alert: TnC binds calcium, not TnI. Calcium binding to TnC removes TnI inhibition.
6. Muscle Contraction Mechanism (Sliding Filament Theory)
The sliding filament theory explains how sarcomeres shorten during contraction. This process is frequently tested step-by-step.
6.1 Steps of Muscle Contraction
Mnemonic: "NICE CAMP" (for sequence of events)
- N = Nerve impulse reaches neuromuscular junction
- I = Ion (Acetylcholine/ACh) released from motor neuron
- C = Calcium (Ca²⁺) released from sarcoplasmic reticulum
- E = Exposure of myosin-binding sites on actin (tropomyosin moves)
- C = Cross-bridge formation (myosin head binds to actin)
- A = ATP hydrolysis provides energy for power stroke
- M = Movement of thin filament over thick filament (sliding)
- P = Power stroke (myosin head tilts, pulling actin inward)
6.2 Role of ATP in Contraction
Mnemonic: "ATP Does 2 Jobs: Detach & Drive"
- Detachment: ATP binds to myosin head, causing detachment from actin
- Energy release: ATP → ADP + Pi releases energy for myosin head cocking (preparing for next stroke)
- Power stroke: Energy stored in myosin head is used to pull actin filament
Trap Alert: ATP is required for BOTH contraction AND relaxation. Rigor mortis occurs due to ATP depletion after death.
6.3 Relaxation Process
Mnemonic: "Stop Signal Removes Calcium"
- Neural signal stops → ACh degraded by enzyme acetylcholinesterase
- Ca²⁺ pumped back into sarcoplasmic reticulum (requires ATP)
- Tropomyosin covers myosin-binding sites on actin again
- Myosin heads detach from actin (requires ATP)
- Muscle relaxes and sarcomere returns to resting length
7. Muscle Disorders
Several muscle disorders are important for exam questions. Knowing the key feature of each disorder helps in differentiation.
Mnemonic: "My Tetany Muscle Aches Often Gout"
M - Myasthenia gravis
Autoimmune disorder affecting the neuromuscular junction, leading to fatigue, weakness, and paralysis of skeletal muscles.
T - Tetany
Rapid, wild muscle spasms caused by low Ca²⁺ levels in body fluids (hypocalcemia).
M - Muscular dystrophy
Genetic disorder characterized by progressive degeneration of skeletal muscles.
A - Arthritis
Inflammation of joints.
O - Osteoporosis
Age-related disorder marked by decreased bone mass and increased fracture risk; commonly due to reduced estrogen levels.
G - Gout
Inflammation of joints caused by accumulation of uric acid crystals.
Trap Alert: Tetany is due to LOW calcium, whereas muscle contraction requires HIGH calcium inside sarcoplasm.
8. Red and White Muscle Fibers
Skeletal muscles contain two types of fibers with different metabolic and functional properties.
Mnemonic: "Red = Rich, White = Rapid"
9. Locomotion in Different Organisms
Different organisms use varied structures and mechanisms for movement.
9.1 Types of Locomotion
Mnemonic: "CAFÉ" (Cilia, Amoeboid, Flagella, muscular)
- C = Ciliary movement (Paramecium uses cilia for movement)
- A = Amoeboid movement (Amoeba uses pseudopodia; also seen in WBCs, macrophages)
- F = Flagellar movement (bacteria, sperm cells use flagella)
- E (Muscular) = Muscular movement (humans, vertebrates use skeletal muscles)
9.2 Locomotory Structures in Invertebrates
- Hydra: Tentacles with epitheliomuscular cells
- Earthworm: Setae (chitinous bristles) + circular and longitudinal muscles
- Cockroach: Three pairs of jointed legs (walking legs) + two pairs of wings (forewings = tegmina)
- Frog: Forelimbs for support, hindlimbs for leaping, webbed feet for swimming
FAQs on Mnemonics: Locomotion & Movement
| 1. What are the best mnemonics to remember the types of locomotion and movement in animals? |  |
| 2. How do I quickly memorize the differences between striated and smooth muscle fibres for NEET? | |
| 3. What's the easiest way to remember all the bones in the human skeleton using acronyms? | |
| 4. How do muscles and bones work together to create movement - what's the mechanical principle? | |
| 5. What mnemonics help me remember the sliding filament theory and muscle contraction steps? | |
