Locomotion and Movement - Comprehensive NEET Biology Notes

1. Introduction to Locomotion and Movement

Movement is a fundamental characteristic of all living organisms. In humans and animals, movements are of various types—ranging from the streaming of protoplasm in unicellular organisms, such as Amoeba, to complex movements like walking, running, and swimming. Locomotion is a specific form of movement that results in a change of location. Structures involved in locomotion, such as cilia, flagella, and limbs, may also perform other functions like food capture and sensory responses.

Did You Know?

Human beings can move various body parts such as limbs, jaws, eyelids, and tongue, each of which serves multiple purposes beyond just locomotion.

2. Types of Movement

2.1 Amoeboid Movement

Certain specialized cells in the human body, such as macrophages and leukocytes (WBCs), exhibit amoeboid movement. This movement is facilitated by pseudopodia, which are temporary, finger-like projections formed by the streaming of protoplasm, aided by cytoskeletal elements like microfilaments.

2.2 Ciliary Movement

Ciliary movement occurs in the internal tubular organs of the human body lined with ciliated epithelium. For example, cilia in the trachea help clear foreign particles from the respiratory tract, while cilia in the female reproductive system assist in the movement of ova.

2.3 Muscular Movement

Muscular movement is the most prominent type of movement in multicellular organisms, especially humans. It involves the contraction of muscles, enabling locomotion, movement of limbs, and other activities. Muscular contraction is coordinated by the muscular, skeletal, and neural systems, which work together to facilitate movement.

NEET Tip:

Focus on understanding the role of muscles in various types of movement and how they coordinate with the skeletal system, as questions on muscular movement frequently appear in NEET.

Quick Recap

• Amoeboid movement occurs in cells like macrophages and leukocytes.
• Ciliary movement occurs in the respiratory and reproductive systems.
• Muscular movement is the most common type, allowing locomotion and other activities.

3. Muscles and Types of Muscles

3.1 Structure and Function of Muscle Tissue

Muscles are specialized tissues that contribute 40-50% of the total body weight in an adult human. Muscles have unique properties such as excitability, contractility, extensibility, and elasticity, enabling them to perform various movements.

3.2 Types of Muscles

Muscles are classified based on their structure, location, and function:

• Skeletal Muscles: Striated, voluntary muscles attached to bones, responsible for locomotion and posture changes.
• Visceral Muscles: Smooth, non-striated, involuntary muscles found in the walls of internal organs such as the alimentary canal and reproductive tract.
• Cardiac Muscles: Striated, branched, and involuntary muscles found only in the heart, responsible for pumping blood throughout the body.

Visual Aid Suggestion:

A detailed diagram comparing skeletal, visceral, and cardiac muscles, highlighting differences in structure and function, can help students visualize these muscle types.

Quick Recap

• Skeletal muscles are striated, voluntary, and responsible for locomotion.
• Visceral muscles are smooth and involuntary, controlling internal organ movements.
• Cardiac muscles are striated, involuntary, and control heart function.

4. Mechanism of Muscle Contraction

4.1 Sliding Filament Theory

The sliding filament theory explains the mechanism of muscle contraction. According to this theory, muscle contraction occurs when actin filaments slide over myosin filaments, reducing the length of the sarcomere and shortening the muscle. The key proteins involved in contraction are actin (thin filament) and myosin (thick filament), which form cross-bridges during contraction.

Key Steps in Muscle Contraction:

1. A neural signal reaches the neuromuscular junction, releasing acetylcholine.
2. This generates an action potential that spreads across the sarcolemma, causing the release of calcium ions from the sarcoplasmic reticulum.
3. Calcium ions bind to troponin, unmasking the active sites on actin for myosin binding.
4. Myosin heads, powered by ATP hydrolysis, bind to actin, forming cross-bridges and pulling the actin filaments toward the center of the sarcomere.
5. This process continues until calcium ions are pumped back into the sarcoplasmic reticulum, resulting in muscle relaxation.

NEET Problem-Solving Strategy:

Be prepared to answer questions about the role of calcium ions, ATP, and the sliding filament mechanism in muscle contraction, as these are commonly tested concepts.

Quick Recap

• Muscle contraction occurs via the sliding filament mechanism, where actin filaments slide over myosin filaments.
• ATP and calcium ions are essential for cross-bridge formation and muscle contraction.

5. Skeletal System

5.1 Overview of the Human Skeleton

The human skeletal system consists of 206 bones and a few cartilages, providing structural support, protection, and facilitating movement. It is divided into two main parts:

• Axial Skeleton: Comprising 80 bones, including the skull, vertebral column, sternum, and ribs.
• Appendicular Skeleton: Consisting of 126 bones that make up the limbs and their girdles (pectoral and pelvic).

Visual Aid Suggestion:

A labeled diagram of the human skeleton, showing the axial and appendicular skeleton, can help students visualize the structure and functions of the skeletal system.

Quick Recap

• The axial skeleton includes the skull, vertebral column, ribs, and sternum.
• The appendicular skeleton consists of the limb bones and girdles, facilitating movement.

6. Joints and Their Types

6.1 Classification of Joints

Joints are points where two or more bones meet and allow for movement. They are classified into three major types:

• Fibrous Joints: Immovable joints, such as those between skull bones.
• Cartilaginous Joints: Slightly movable joints, like those between vertebrae.
• Synovial Joints: Freely movable joints characterized by a synovial cavity filled with fluid. Examples include ball and socket joints (shoulder and hip), hinge joints (elbow and knee), and pivot joints (neck).

NEET Tip:

Focus on understanding the structure and types of synovial joints, as NEET often tests these concepts, especially the movement capabilities of different joints.

Quick Recap

• Fibrous joints are immovable, cartilaginous joints are slightly movable, and synovial joints allow free movement.
• Synovial joints play a significant role in locomotion and body movement.

7. Disorders of the Muscular and Skeletal System

7.1 Common Disorders

• Myasthenia Gravis: An autoimmune disorder affecting neuromuscular junctions, leading to muscle weakness and fatigue.
• Muscular Dystrophy: A genetic disorder that causes progressive degeneration of skeletal muscles.
• Arthritis: Inflammation of joints, resulting in pain and stiffness.
• Osteoporosis: An age-related condition characterized by decreased bone density and increased risk of fractures.
• Gout: Inflammation of joints caused by the accumulation of uric acid crystals.

Real-life Application:

Understanding these disorders is essential for diagnosing and treating musculoskeletal conditions, especially in aging populations where diseases like osteoporosis and arthritis are common.

Quick Recap

• Disorders like myasthenia gravis, muscular dystrophy, and arthritis affect muscles and joints, leading to impaired movement and discomfort.
• Osteoporosis and gout are common in aging individuals and can cause significant health issues.

NEET Exam Strategy

• Focus on the types of muscles, mechanisms of muscle contraction, and the role of the skeletal system in movement.
• Be prepared for diagram-based questions on the human skeleton, muscle structure, and synovial joints.
• Familiarize yourself with common musculoskeletal disorders, as these often appear in NEET questions.

Practice Questions

1. Which of the following is an involuntary muscle?
   Solution: d) Both b and c
2. • a) Skeletal muscle
   • b) Cardiac muscle
   • c) Smooth muscle
   • d) Both b and c
2. Which type of joint allows the greatest range of movement?
   Solution: b) Ball and socket joint
3. • a) Hinge joint
   • b) Ball and socket joint
   • c) Pivot joint
   • d) Fibrous joint
3. What is the role of calcium ions in muscle contraction?
   Solution: c) To unmask the active sites on actin for myosin binding
4. • a) To bind to actin filaments
   • b) To release ATP for energy
   • c) To unmask the active sites on actin for myosin binding
   • d) To initiate the breakdown of myosin
4. Which of the following is not a function of the skeletal system?
   Solution: d) Protein synthesis
5. • a) Protection of internal organs
   • b) Movement facilitation
   • c) Blood cell production
   • d) Protein synthesis
5. Which disorder is characterized by the accumulation of uric acid crystals in joints?
   Solution: d) Gout
6. • a) Osteoporosis
   • b) Arthritis
   • c) Myasthenia gravis
   • d) Gout

Glossary

• Sarcomere: The functional unit of muscle contraction.
• Synovial Joint: A freely movable joint with a fluid-filled cavity.
• Osteoporosis: A condition causing weakened bones due to decreased bone density.
• Myasthenia Gravis: An autoimmune disorder affecting muscle contraction.