Locomotion And Movement Class 11 Biology Chapter 17 Notes

Locomotion and Movement Class 11 Biology Chapter 17 Notes

Movement and Locomotion in Living Beings

Movement is a fundamental feature of living beings.
Both animals and plants exhibit various forms of movement.
Different organisms display different types of movements.
Movement can range from the streaming of protoplasm in unicellular organisms like Amoeba to complex forms in multicellular organisms.

Types of Movements:

Unicellular organisms like Amoeba exhibit the streaming of protoplasm as a basic form of movement.
Many organisms, including single-celled and multicellular ones, employ structures such as cilia, flagella, and tentacles for movement.
In humans, movement includes the motion of limbs, jaws, eyelids, tongue, and other body parts.
Some movements result in a change of place or location and are termed as locomotion.

Locomotion:

Locomotion is a type of voluntary movement that involves changing one’s place or location.
Examples of locomotory movements include walking, running, climbing, flying, and swimming.
Interestingly, locomotory structures can overlap with those used for other types of movements. For instance, in Paramecium, cilia aid in both food movement through the cytopharynx and locomotion.
Similarly, Hydra employs its tentacles both for capturing prey and for locomotion.
In humans, limbs are used for changing body postures as well as for locomotion.
This implies that movements and locomotion are interrelated. All locomotions are movements, but not all movements are locomotions.

Purpose of Locomotion:

The methods of locomotion performed by animals vary depending on their habitats and the demands of specific situations.
Typically, animals engage in locomotion for various purposes, including:
1. Searching for food
2. Seeking shelter
3. Finding a mate
4. Locating suitable breeding grounds
5. Adapting to favorable climatic conditions
6. Escaping from enemies or predators

Types of Movement in the Human Body

Cells in the human body display various types of movement.
Three primary types of movements in human cells are amoeboid, ciliary, and muscular.
Specialized cells, such as macrophages and leukocytes, exhibit amoeboid movement, which is essential for immune responses.
Ciliary movement is observed in various internal organs lined by ciliated epithelium, facilitating functions like dust particle clearance and ova passage.
Muscular movement is crucial for activities such as limb movement, jaw action, and tongue motion. This type of movement relies on the contractile properties of muscles and is vital for locomotion and other essential bodily functions.

Amoeboid Movement:

Amoeboid movement is seen in specific cells like macrophages and leukocytes.
It is characterized by the formation of pseudopodia, extensions of the cell membrane, propelled by the streaming of protoplasm (similar to Amoeba’s movement).
Cytoskeletal elements, including microfilaments, play a role in amoeboid movement.

Ciliary Movement:

Ciliary movement occurs in organs lined with ciliated epithelium, such as the trachea.
Cilia are tiny hair-like structures that exhibit coordinated movements.
In the trachea, ciliary movement helps in clearing dust particles and foreign substances present in inhaled air.
Ciliary action also aids in the passage of ova through the female reproductive tract.

Muscular Movement:

Muscular movement involves the action of muscles, which are contractile tissues.
Muscles are responsible for various movements in the body, including locomotion and other essential bodily functions.
Locomotion, in particular, requires the coordinated activity of the muscular, skeletal, and neural systems.

Coordination of Systems:

Locomotion necessitates a perfect coordination of muscular, skeletal, and neural systems.
The types of muscles, their structure, mechanisms of contraction, and the skeletal system’s crucial aspects all play a role in enabling coordinated movement.

Muscle: Structure and Mechanism of Contraction

Introduction:

Cilia and flagella are cell membrane outgrowths involved in various movements.
Muscle is a specialized tissue of mesodermal origin, constituting a significant portion of the human body’s weight.
Muscles possess unique properties such as excitability, contractility, extensibility, and elasticity.
Muscle classification is based on location, appearance, and nature of regulation, resulting in three main types: skeletal, visceral, and cardiac muscles.

Types of Muscles

Skeletal Muscles:
- Skeletal muscles are associated with the body’s skeletal components and have a striped appearance (striated) under the microscope.
- They are also called voluntary muscles because they are under the control of the nervous system.
- Skeletal muscles are primarily involved in locomotion and changes in body postures.
Visceral Muscles:
- Visceral muscles are located in the inner walls of hollow visceral organs like the digestive and reproductive tracts.
- They lack striations and have a smooth appearance, earning them the name smooth muscles (nonstriated).
- The nervous system does not directly control their activities, making them involuntary muscles.
- Visceral muscles assist in functions like food transportation and gamete passage.
Cardiac Muscles:
- Cardiac muscles are the muscles of the heart.
- They appear striated and are involuntary, as their activities are not directly controlled by the nervous system.
- Cardiac muscle cells form a branching pattern to create the cardiac muscle.

Structure and Mechanism of Skeletal Muscle:

Skeletal muscles consist of muscle bundles or fascicles held together by a collagenous connective tissue layer called fascia.
Each muscle bundle contains multiple muscle fibers, each enclosed by a plasma membrane called the sarcolemma.
Muscle fibers contain multiple nuclei, making them syncytia.
The sarcoplasmic reticulum in muscle fibers stores calcium ions.
Myofibrils, which are parallelly arranged filaments, create the striated appearance of skeletal muscle.
The striations are due to the distribution of two proteins: Actin (in light bands or I-bands) and Myosin (in dark bands or A-bands).
Actin and Myosin are rod-like structures that run parallel to each other and the myofibril’s longitudinal axis.
The ‘I’ band contains Actin, while the ‘A’ band contains Myosin. A ‘Z’ line bisects the ‘I’ band and holds the thin filaments.
The ‘A’ band is secured in the middle by the ‘M’ line.
Sarcomeres, the functional units of contraction, are the portions of myofibrils between two successive ‘Z’ lines.
In a resting state, the edges of thin filaments overlap the free ends of thick filaments, leaving the central part of thick filaments, known as the ‘H’ zone.

Structure of Contractile Proteins in Muscle Contraction

Actin Filament:

Each actin (thin) filament is composed of two ‘F’ (filamentous) actins wound helically around each other.
‘F’ actin is a polymer formed from monomeric ‘G’ (Globular) actins.
Two protein filaments called tropomyosin run closely alongside ‘F’ actin throughout its length.
A complex protein called troponin is distributed at regular intervals along the tropomyosin.
In the resting state, a subunit of troponin masks the active binding sites for myosin on the actin filaments.

Myosin Filament:

Each myosin (thick) filament is a polymerized protein, consisting of many monomeric proteins known as Meromyosins.
Meromyosins are the building blocks of a thick filament and have two significant parts: the globular head with a short arm and the tail.
The globular head is called heavy meromyosin (HMM), and the tail is referred to as light meromyosin (LMM).
The HMM component, including the head and short arm, extends outward at regular intervals and angles from the surface of the polymerized myosin filament, forming a cross arm.
The globular head of HMM is an active ATPase enzyme and contains binding sites for ATP and active sites for actin.

Mechanism of Muscle Contraction

Muscle contraction is a complex process that is best explained by the sliding filament theory.
This theory states that muscle fibers contract by the sliding of thin filaments over thick filaments.

Initiation of Muscle Contraction:

Muscle contraction begins with a signal sent by the central nervous system (CNS) through a motor neuron.
A motor neuron, along with the muscle fibers it connects to, forms a motor unit.
The point where a motor neuron connects with the sarcolemma of the muscle fiber is called the neuromuscular junction or motor-end plate.
When a neural signal reaches this junction, it triggers the release of the neurotransmitter acetylcholine, which generates an action potential in the sarcolemma.
The action potential spreads through the muscle fiber and leads to the release of calcium ions into the sarcoplasm.

Contraction Process:

Increased levels of calcium ions lead to the binding of calcium with a subunit of troponin on actin filaments, removing the masking of active sites for myosin.
The myosin head, utilizing energy from ATP hydrolysis, binds to the exposed active sites on actin, forming a cross-bridge.
This cross-bridge formation causes the attached actin filaments to move towards the center of the ‘A’ band.
The ‘Z’ line, connected to these actins, is also pulled inwards, resulting in the shortening of the sarcomere, i.e., muscle contraction.
During muscle shortening, the ‘I’ bands decrease in length, while the ‘A’ bands maintain their size.
After the myosin releases ADP and inorganic phosphate (P1), it returns to its relaxed state.
A new ATP molecule binds to myosin, breaking the cross-bridge.
ATP is then hydrolyzed by the myosin head, and the cycle of cross-bridge formation and breakage is repeated, leading to further sliding of the filaments.
This process continues until calcium ions are pumped back into the sarcoplasmic cisternae, masking the actin filaments.
As a result, the ‘Z’ lines return to their original position, leading to muscle relaxation.

Variations in Muscle Fibers:

Different muscles have varying reaction times, with repeated activation potentially causing the accumulation of lactic acid due to anaerobic glycogen breakdown, leading to fatigue.
Muscle fibers contain myoglobin, a red-colored oxygen-storing pigment, which is high in red fibers.
Red fibers also have many mitochondria that use stored oxygen for ATP production, making them aerobic muscles.
In contrast, white fibers contain less myoglobin and appear pale, relying on anaerobic processes for energy, even though they have a high amount of sarcoplasmic reticulum.

The Human Skeletal System: Structure and Function

The skeletal system is a framework composed of bones and cartilage.
It plays a crucial role in enabling movement in the human body.
This system consists of approximately 206 bones and a few cartilages.
Bones are specialized connective tissues with a hard matrix due to calcium salts, while cartilages have a slightly pliable matrix due to chondroitin salts.

Divisions of the Skeletal System:

The skeletal system is divided into two principal divisions: the axial and appendicular skeleton.

Axial Skeleton:

The axial skeleton consists of 80 bones aligned along the main body axis.
It includes the skull, vertebral column, sternum, and ribs.

Skull:

The skull is composed of cranial and facial bones, totaling 22 bones.
Cranial bones (8 in number) form the protective outer covering, the cranium, for the brain.
The facial region consists of 14 skeletal elements that make up the front part of the skull.
A U-shaped bone called the hyoid is found at the base of the oral cavity and is also part of the skull.
Each middle ear contains three tiny bones, known as ear ossicles: Malleus, Incus, and Stapes.

Vertebral Column:

The vertebral column is made up of 26 serially arranged vertebrae.
It is dorsally placed and extends from the base of the skull, forming the main framework of the trunk.
Each vertebra has a central neural canal through which the spinal cord passes.
The vertebral column is divided into cervical (7), thoracic (12), lumbar (5), sacral (1-fused), and coccygeal (1-fused) regions.
The vertebral column protects the spinal cord, supports the head, and serves as an attachment point for ribs and back musculature.

Rib Cage:

There are 12 pairs of ribs.
Each rib is a thin, flat bone connected dorsally to the vertebral column and ventrally to the sternum.
The first seven pairs of ribs are called true ribs, attaching to thoracic vertebrae and the sternum via hyaline cartilage.
The 8th, 9th, and 10th pairs (vertebrochondral or false ribs) do not directly articulate with the sternum but join the seventh rib through hyaline cartilage.
The last two pairs (11th and 12th) of ribs are called floating ribs as they are not connected ventrally.

Appendicular Skeleton:

The appendicular skeleton consists of the bones of the limbs and their girdles.
Each limb is made up of 30 bones.

Bones of the Hand (Fore Limb):

Humerus, radius, ulna, carpals (wrist bones – 8), metacarpals (palm bones – 5), and phalanges (digits – 14).

Bones of the Leg (Hind Limb):

Femur (thigh bone), tibia, fibula, tarsals (ankle bones – 7), metatarsals (5), and phalanges (digits – 14).
A cup-shaped bone, the patella, covers the knee ventrally.

Pectoral and Pelvic Girdles:

The pectoral girdle facilitates the articulation of the upper limbs with the axial skeleton and is composed of the clavicle and scapula.
The pelvic girdle includes two coxal bones, each formed by the fusion of the ilium, ischium, and pubis.
A cavity called acetabulum in the coxal bone articulates with the thigh bone.
The two halves of the pelvic girdle meet ventrally to form the pubic symphysis, containing fibrous cartilage.

Joints in the Human Body

Introduction:

Joints play a fundamental role in facilitating various movements involving the bones of the body.
Locomotory movements rely on joints, which act as pivot points for the force generated by muscles.
Joints are points of contact between bones or between bones and cartilages.
Their mobility varies based on structural characteristics and other factors.
Joints are classified into three main structural forms: fibrous, cartilaginous, and synovial joints.

Types of Joints

Fibrous Joints:
- Fibrous joints are immovable and do not allow any movement.
- An example of fibrous joints is found in the flat skull bones that fuse end-to-end using dense fibrous connective tissues, forming sutures to create the cranium.
Cartilaginous Joints:
- In cartilaginous joints, bones are connected with the help of cartilages.
- An example is the joint between adjacent vertebrae in the vertebral column.
- Cartilaginous joints permit limited movements.
Synovial Joints:
- Synovial joints are characterized by a fluid-filled synovial cavity located between the articulating surfaces of two bones.
- This structural arrangement allows considerable movement, making them essential for locomotion and various other movements.
- Examples of synovial joints include:
  - Ball and socket joint: Found between the humerus and pectoral girdle, allowing for a wide range of motion.
  - Hinge joint: Seen in the knee joint, enabling flexion and extension movements.
  - Pivot joint: Located between the atlas and axis in the neck, allowing for rotational movements.
  - Gliding joint: Found between the carpals in the wrist, permitting sliding and gliding motions.
  - Saddle joint: Present between the carpal and metacarpal bones of the thumb, facilitating versatile movements.

Disorders of the Muscular and Skeletal System

The muscular and skeletal systems are essential for maintaining the body’s structure and enabling movement. Various disorders can affect these systems, leading to a range of health issues. Here are some common disorders related to the muscular and skeletal systems:

1. Myasthenia Gravis:

Description: Myasthenia gravis is an autoimmune disorder that impacts the neuromuscular junction.
Symptoms: It leads to muscle fatigue, weakness, and, in severe cases, paralysis of skeletal muscles.
Cause: The immune system mistakenly attacks and damages the receptors at the neuromuscular junction.
Treatment: Treatment may include medications that improve neuromuscular transmission and, in some cases, surgical interventions.

2. Muscular Dystrophy:

Description: Muscular dystrophy is a group of genetic disorders characterized by the progressive degeneration of skeletal muscles.
Symptoms: It results in muscle weakness, loss of muscle mass, and mobility impairment.
Cause: Genetic mutations lead to the absence or dysfunction of proteins necessary for muscle structure and function.
Treatment: There is no cure for muscular dystrophy, but therapies and interventions can help manage symptoms and improve quality of life.

3. Tetany:

Description: Tetany is a condition characterized by rapid muscle spasms, which can involve wild and uncontrollable contractions.
Cause: It is often associated with low levels of calcium (Ca++) in the body’s fluids.
Treatment: Treating tetany involves addressing the underlying cause, such as correcting calcium imbalances.

4. Arthritis:

Description: Arthritis is a broad term referring to inflammation of the joints.
Symptoms: Common symptoms include joint pain, swelling, and reduced mobility.
Types: There are many types of arthritis, including osteoarthritis, rheumatoid arthritis, and gout.
Treatment: Treatment depends on the type of arthritis but may include medication, physical therapy, and lifestyle modifications.

5. Osteoporosis:

Description: Osteoporosis is an age-related disorder characterized by decreased bone mass and increased susceptibility to fractures.
Cause: Reduced bone density is often linked to aging, hormonal changes, and a decrease in estrogen levels in postmenopausal women.
Prevention and Treatment: Maintaining a healthy diet, exercise, and sometimes medications can help prevent and manage osteoporosis.

6. Gout:

Description: Gout is a form of arthritis caused by the accumulation of uric acid crystals in the joints.
Symptoms: It results in sudden and severe joint pain, most commonly in the big toe.
Cause: Elevated levels of uric acid in the blood can lead to the formation of crystals in the joints.
Treatment: Treatment includes medications to manage pain and inflammation, lifestyle changes, and dietary modifications to reduce uric acid levels.