Locomotion and Movement NEET Notes 2027: Key Points and PDF

Locomotion and Movement is Chapter 17 of NCERT Class 11 Biology and part of Unit 5, Human Physiology, of the NEET UG syllabus. These notes cover types of movement, skeletal muscle structure, contractile proteins, the sliding filament theory, red and white fibres, the human skeleton, joints and disorders of the muscular and skeletal system, with a free notes PDF.

Locomotion and Movement NEET Notes

Section-wise key points from NCERT Chapter 17, comparison tables, high-yield facts and common mistakes for NEET 2027 revision.

Locomotion and Movement at a Glance

The topic list follows the NEET UG 2026 syllabus released by the National Medical Commission (NMC) on 22 December 2025, which stays the reference until the 2027 syllabus is out. The full list is on the NEET syllabus page.

What is the difference between movement and locomotion?

Locomotion is voluntary movement that changes an animal’s place; all locomotions are movements, but not all movements are locomotions.

• Examples of locomotion: walking, running, climbing, flying and swimming.
• The same structure can serve both: Paramoecium cilia move food through the cytopharynx and also help in locomotion; Hydra uses its tentacles to catch prey and to move.
• Animals move in search of food, shelter, a mate, breeding grounds or a better climate, or to escape enemies and predators.
• Locomotion needs coordinated activity of the muscular, skeletal and neural systems.

NCERT lists amoeboid, ciliary and muscular as the three main movements of human body cells; the NEET syllabus lists ciliary, flagellar and muscular.

Types of Muscle

Muscle is a specialised tissue of mesodermal origin and makes up about 40 to 50 per cent of the body weight of an adult human.

• Muscles show excitability, contractility, extensibility and elasticity.

Structure of Skeletal Muscle and the Sarcomere

A skeletal muscle is made of muscle bundles (fascicles) held together by a collagenous connective tissue layer, the fascia; each bundle contains many muscle fibres.

• Each muscle fibre is lined by the sarcolemma (plasma membrane) enclosing the sarcoplasm. It is a syncytium because the sarcoplasm has many nuclei.
• The sarcoplasmic reticulum (the endoplasmic reticulum of the fibre) stores calcium ions.
• Many parallel myofilaments or myofibrils show alternate light and dark bands, caused by actin and myosin.
• I band (isotropic, light) contains actin; A band (anisotropic, dark) contains myosin. Actin forms thin filaments and myosin thick filaments.
• The elastic Z line bisects each I band and the thin filaments are firmly attached to it. The thin fibrous M line holds the thick filaments together in the middle of the A band.
• The sarcomere, the part of a myofibril between two successive Z lines, is the functional unit of contraction.
• The H zone is the central part of the thick filaments not overlapped by thin filaments in a resting muscle.

Contractile Proteins: Actin and Myosin

Actin and myosin are polymerised proteins arranged parallel to each other and to the long axis of the myofibril.

How Does a Muscle Contract? the Sliding Filament Theory

Muscle contraction takes place by the sliding of thin filaments over thick filaments.

• The CNS sends a signal through a motor neuron. A motor neuron and the muscle fibres connected to it form a motor unit.
• At the neuromuscular junction (motor-end plate), the neurotransmitter acetylcholine generates an action potential in the sarcolemma.
• The action potential spreads through the fibre and releases calcium ions into the sarcoplasm.
• Ca++ binds a subunit of troponin on the actin filaments and unmasks the active sites for myosin.
• Using energy from ATP hydrolysis, the myosin head binds the exposed sites on actin to form a cross bridge.
• The cross bridge pulls the actin filaments towards the centre of the A band; the attached Z lines are pulled inwards and the sarcomere shortens.
• Myosin releases ADP and Pi and returns to its relaxed state; a new ATP binds and the cross bridge breaks. ATP is hydrolysed again and the cycle repeats.
• When Ca++ is pumped back into the sarcoplasmic cisternae, actin is masked again and the Z lines return to their original position: relaxation.
• Repeated activation builds up lactic acid from the anaerobic breakdown of glycogen, causing fatigue.

Human Skeletal System

The human skeleton has 206 bones and a few cartilages, divided into the axial skeleton (80 bones) and the appendicular skeleton.

• Bone and cartilage are specialised connective tissues. Bone has a very hard matrix due to calcium salts; cartilage has a slightly pliable matrix due to chondroitin salts.

Axial Skeleton

• Each vertebra has a central neural canal for the spinal cord. The first vertebra, the atlas, articulates with the occipital condyles.
• Almost all mammals, including humans, have seven cervical vertebrae.
• The vertebral column protects the spinal cord, supports the head and gives attachment to the ribs and back muscles.
• Each rib has two articulation surfaces at its dorsal end, so it is bicephalic.
• True ribs join the sternum through hyaline cartilage; false ribs join the seventh rib through hyaline cartilage; floating ribs are not connected ventrally.
• Thoracic vertebrae, ribs and sternum together form the rib cage.

Appendicular Skeleton: Limbs and Girdles

• Pectoral girdle: each half has a clavicle and a scapula. The scapula is a large triangular flat bone on the dorsal thorax between the second and seventh ribs.
• The spine of the scapula ends in the acromion, with which the clavicle articulates. Below it, the glenoid cavity articulates with the head of the humerus to form the shoulder joint.
• The clavicle (collar bone) is a long slender bone with two curvatures.
• Pelvic girdle: two coxal bones, each formed by fusion of the ilium, ischium and pubis. The thigh bone articulates at the acetabulum.
• The two halves of the pelvic girdle meet ventrally at the pubic symphysis, which has fibrous cartilage.

Joints: Types and Examples

Joints are points of contact between bones, or between bones and cartilages; the joint acts as a fulcrum for the force generated by muscles.

Disorders of the Muscular and Skeletal System

NCERT lists six disorders, the same six named in the NEET UG syllabus.

Most-asked Facts for NEET: Locomotion and Movement

Revise these one-line facts from the NCERT chapter just before the exam.

• Macrophages and leucocytes show amoeboid movement; ciliary movement clears dust in the trachea.
• Muscle is mesodermal and forms about 40 to 50% of adult body weight.
• A muscle fibre is a syncytium; the sarcoplasmic reticulum stores Ca++.
• Sarcomere: between two successive Z lines; functional unit of contraction.
• I band = actin (isotropic); A band = myosin (anisotropic).
• During contraction the I band shortens and the A band keeps its length.
• Thin filament: two F actins, two tropomyosin filaments and troponin.
• Myosin head (HMM) is an ATPase with ATP-binding sites and actin-binding sites.
• Acetylcholine is released at the neuromuscular junction; Ca++ binds troponin.
• Red fibres: myoglobin-rich, many mitochondria, aerobic; white fibres: little myoglobin, high sarcoplasmic reticulum, anaerobic.
• 206 bones; axial skeleton 80; skull 22 (8 cranial, 14 facial).
• 26 vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 1 sacral, 1 coccygeal.
• Ribs: 7 true, 3 false (vertebrochondral), 2 floating; ribs are bicephalic.
• Each limb has 30 bones; femur is the longest bone; 8 carpals and 7 tarsals.
• Coxal bone = ilium + ischium + pubis; acetabulum receives the femur.
• Pivot joint: atlas and axis; saddle joint: carpal and metacarpal of the thumb.
• Tetany: low Ca++; gout: uric acid crystals; myasthenia gravis: autoimmune.

Common Mistakes to Avoid

Watch for these mix-ups when you answer questions on this chapter.

• Saying the A band shortens during contraction. The A band keeps its length; the I band shortens.
• Defining the sarcomere between two M lines. It lies between two successive Z lines.
• Saying Ca++ binds tropomyosin or myosin. It binds a subunit of troponin.
• Saying troponin masks sites on myosin. At rest it masks the myosin-binding sites on actin.
• Linking tetany to high calcium. Tetany is caused by low Ca++ in body fluid.
• Calling myasthenia gravis a genetic disease. It is autoimmune; muscular dystrophy is mostly genetic.
• Mixing up gout and arthritis: gout is joint inflammation due to uric acid crystals.
• Calling ribs 8 to 10 floating ribs. Ribs 8 to 10 are false (vertebrochondral); 11 and 12 are floating.
• Calling cardiac muscle voluntary or non-striated. It is striated and involuntary.
• Calling white fibres aerobic. Red fibres are aerobic; white fibres depend on anaerobic processes.
• Counting 33 vertebrae for the adult. NCERT counts 26, with one fused sacrum and one fused coccyx.

Locomotion and Movement Notes PDF and Related Pages

Download the AglaSem notes for Locomotion and Movement (key notes and important questions with answers) free: View PDF

• All chapters: NEET Biology notes
• Full topic list: NEET syllabus
• Practice: NEET question papers
• Source text: NCERT Chapter 17 (NCERT, Class 11 Biology)

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