Samacheer Class 11 Bio Zoology - Locomotion and Movement

Oxidative fibres and glycolytic fibres differ in several important characteristics. Oxidative fibres, also called red muscle fibres, contain numerous mitochondria that enable them to generate energy through aerobic respiration. They depend heavily on blood flow to deliver oxygen and nutrients, and they contain high levels of myoglobin, which gives them their characteristic red colour and allows them to store oxygen. These fibres are suited for sustained, endurance activities. In contrast, glycolytic fibres, also called white muscle fibres, contain relatively few mitochondria and rely primarily on anaerobic glycolysis for energy production. They do not depend significantly on blood flow and lack myoglobin, giving them a pale appearance. Glycolytic fibres are adapted for rapid, powerful contractions over short periods but fatigue more quickly than oxidative fibres. The distribution of these fibre types varies among different muscles depending on their functional requirements.

• It is a large opening found at the posterior base of the skull.
• Through this opening, the medulla oblongata of the brain descends down as the spinal cord.

• There are 8 bones in the wrist arranged in two rows of four each.
• The anterior surface of the wrist has a tunnel-like appearance. This tunnel is termed a carpal tunnel.

The calcium released from the sarcoplasm binds with the thin fibre of the muscle.
* The released calcium binds to troponin thin filaments.
III. Fill Up The Blanks With Suitable Options
1. Scapula – Acromian process
……………. – Bones of the upper arm
2. First 7 pair of rib bones – True ribs
11 and 12th pair of ribs – …………….
3. Cervical vertebrae – 7
……………. – Lumbar bones
4. Skull bones – 22
……………. – Skull bones
5. Thick fibres – Myosin
……………. – Thin fibres
6. Amoeboid movement – Macrophage cells
……………. – Sperm cells
* Olecranon process
* Floating ribs
* 5
* 8
* Actin
* Flagellated movement
3 marks
IV. Short answers

• Each muscle is made up of bundles of muscle fibres called fascicles. Each muscle fibre contains rod-like structures called myofibrils.
• The connective tissue covering the muscle is the epimysium.
• The covering around each fascicle is the perimysium.
• The muscle fibre is surrounded by endomysium.

• Each muscle fibre is thin and elongated.
• Most of the taper at one or both ends.
• Muscle fibres are surrounded by sarcolemma the cytoplasm of the muscle fibre is called the sarcoplasm.
• It contains glycosomes myoglobin and sarcoplasmic reticulum.
• Myoglobin is a red-coloured respiratory pigment and glycosomes are reserved glycogen.
• Muscle fibres contain muscle protein actin and myosin.

• These fibers have low rates of myosin ATP hydrolysis but have the ability to make large amounts of ATP.
• This type of fiber seen in long-distance swimmers and long-distance runners.

• These fibres have myosin ATP ase activity but cannot make as much ATP as oxidative fibres because their source of ATP in glycolysis.
• These fibres are best suited for rapid intense actions such as short sprints at maximum speed.

The human skull is composed of 22 bones, which can be broadly divided into cranial and facial bones. The facial skeleton consists of 14 bones. These include a pair of maxillae (upper jaw bones), a pair of zygomatic bones (cheekbones), a pair of palatine bones (forming the hard palate), a pair of lacrimal bones (in the inner wall of the orbit), a pair of nasal bones (forming the bridge of the nose), a single vomer (forming the lower part of the nasal septum), and a pair of inferior nasal conchae. Additionally, the mandible, or lower jaw bone, is also a facial bone and is the only movable bone in the skull.

• It is an autoimmune disorder affecting the action of acetylcholine at the neuromuscular junction leading to fatigue.
• Weakening and paralysis of skeletal muscles.
• Acetylcholine receptors on the sarcolemma are blocked by antibodies leading to weakness of muscles.
• When the disease progresses it can make chewing swallowing talking and even breathing difficult.

• It is the inability of a muscle to contract after repeated muscle contraction.
• This is due to lack of ATP and accumulation of lactic acid by anaerobic break down of glucose.

• A decrease in the activity of muscles results in the atrophy of muscles.
• There is a reduction in the size of the muscle and makes the muscle become weak which occurs with lack of usage as in chronic bedridden patients.

Muscle pull is actually a muscle tear.
Atraumatic pulling of the fibres produces a tear known as a sprain.
* This can occur due to the sudden stretching of muscle beyond the point of elasticity.
* Back pain is a common problem caused by muscle pull due to improper posture with static sitting for long hours.

• The group of diseases collectively called muscular dystrophy is associated with the progressive degeneration of skeletel muscle fibers weakening the muscles and leading to death from lung or heart failure.
• (eg) Duchene muscular dystrophy.

• This is used to measure an athlete’s muscle glycogen.
• Muscle glycogen provides the main source of energy during anaerobic exercise.
• A single glycogen molecule may contain 5000 glucose molecules.

• It occurs due to deficiency of vitamin D and hormonal imbalance.
• It causes rickets in children and osteomalacia in adult females.
• The bones become soft and fragile.
• It can be minimized with adequate calcium intake vitamin D intake and regular physical activities.

Carpal tunnel syndrome is a condition characterized by the compression of the median nerve as it passes through the carpal tunnel in the wrist. The carpal tunnel is a narrow passageway formed by the carpal bones on the bottom and sides and the transverse carpal ligament on top. When this passage becomes narrowed due to inflammation, swelling, or other factors, it can put pressure on the median nerve, leading to symptoms such as numbness, tingling, pain, and weakness in the hand and fingers, particularly the thumb, index, middle, and part of the ring finger. This condition is frequently observed in individuals whose occupations involve repetitive hand and wrist motions, such as clerks, software professionals, and those who engage in extensive mobile phone use for texting or gaming.

An isometric contraction is a type of muscle contraction where the muscle generates tension, but its overall length does not change. In this process, the muscle fibers attempt to shorten, but they are opposed by an external force, such as an immovable object or the weight of an object being held steady. Consequently, the force exerted by the muscle increases, but since the muscle does not shorten or lengthen, no movement occurs at the joint. Examples include pushing against a wall, where the muscle fibers are activated and generate force but the wall does not move, or holding a heavy bag stationary, where the muscles maintain tension to counteract gravity without changing their length.

Rigor mortis is the postmortem stiffening of muscles that occurs after death. After an individual dies, the cell membrane of muscle cells becomes more permeable to calcium ions due to the breakdown of cellular processes and loss of ATP production. The influx of calcium ions triggers partial contraction of the skeletal muscles throughout the body. Once contracted, the muscles are unable to relax because ATP is required for muscle relaxation and is no longer being produced in dead cells. This results in the characteristic rigid, stiff appearance of the body. Rigor mortis typically begins a few hours after death and gradually disappears as the muscle proteins begin to decompose. The timing and progression of rigor mortis can provide forensic evidence in determining the approximate time of death.

Sliding filament theory is an active process. It is proposed by Andrw F. Huxley in 1954 and Rolf Niedergerke.
* Muscle contraction is initiated by a nerve impulse sents by the central nervous system through a motor neuron
* When the nerve impulse reaches neuromuscular junction acetylcholine is released and created action potential.
* This action potential triggers the release of calcium from the sarcoplasmic reticulum
* The released calcium ions bind to troponin on thin filaments.
* The active sites are exposed to the heads of myosin to form a cross bridge. Hence actin and myosin form a protein complex called actomyosin.
* Utilizing the energy released from the hydrolysis of ATP the myosin head rotates until it forms a 90° angle with a long axis of the filament.
* The power stroke begins after the myosin head and hinges region tilt from a 90° angle to a 45° angle.
* The cross-bridge transforms into a strong high force bond which allows the myosin head to swells it.
* When the myosin head swells it pulls the attached actin filament towards the centre of the A – band.
* The myosin returns back to its relaxed state and releases ADP and phosphate ions. A Newer ATP molecule binds to the head of the myosin and the cross-bridge is broken.
* At the end of each power stroke each myosin head detaches from actin then swivels back and binds to a new actin molecule to start another contraction cycle.
* The power stroke repeats many times and the thin filaments move toward the centre of the sarcomere.
* In this process, there is no change in the lengths of thick or thin filaments.
* The Z – discs attached to the actin filaments are also pulled inwards from both sides causing the shortening of the sarcomere. This process continues.
* When motor impulse stops the calcium ions are purnbed back into the sarcoplasmic reticulum results in the masking of the active sites of the actin filament and the myosin head fails to bind with the actin and causes Z – discs back to their original relaxed position.

The benefits of regular exercise are:
* The muscles used in exercise grow larger and stronger.
* The resting heart rate goes down.
* More enzymes are synthesized in the muscle fiber.
* Ligaments and tendons become stronger.
* Joints become more flexible.
* Protection from a heart attack.
* Influences hormonal activity.
* Improves cognitive functions.
* Prevents obesity.
* Promotes confidence, esteem.
* Aesthetically better with a good physique.
* Overall well-being with good quality of life.
* Prevents depression, stress, and anxiety.
Part II
11th Bio Zoology Guide Locomotion and Movement Additional Important Questions and Answers
I. Choose The Best Options

• Each muscle fibre is thin and elongated.
• It has multiple oval nuclei beneath sarcolemma.
• The cytoplasm of the muscle fibre is called sarcoplasm.
• It contains glycosomes, the stored glycogen granules, myoglobin, respiratory pigment, and sarcoplasmic reticulum.
• Actin and myosin are muscle proteins present in the muscle fibre.
• Each myofibril has a repeated series of dark and light bands called A-bands and I-bands.
• Each dark band has a lighter region in its middle called the H-zone.
• Each H-zone is bisected vertically by a dark line called the M-line.
• Each light I-band has a darker mid-line area called the Z-disc.
• The sarcomere is the functional unit of the skeletal muscle. It is a region of a myofibril between two successive Z-discs.
• Sarcomere has thick and thin filaments. The thick filaments extend the entire length of the A-band, the thin filaments extend across the I-band and partly into the A-band.
• The invagination of the sarcolemma forms transverse tubules (T-tubules) and they penetrate into the junction between the A and I-bands.

• The unit of the skeletal muscle is the sarcomere A sarcomere is the region of a myofibril between two successive z – discs.
• It contains an ‘A’ band with a half I band which are perfectly aligned with one another.
• This type of arrangement gives the cell a striated appearance.
• Each dark band has a lighter region in its middle called the M – zone.
• Each H – zone is bisected vertically by a dark line called the M – line.
• The I bands have a darker mid-line area called the z – disc.
• Inside the sarcomere, two types of filaments are present namely the thick filaments and thin filaments.
• The thick filaments extend the entire length of the A band, the thin filaments extend across the I band and partly into the A – band.
• The invagination of the sarcolemma forms transverse (T- tubules) tubules and they penetrate into the junction between the A and I bands.

Contraction of the muscle depends on the presence of contractile proteins such as actin and myosin.
Myosin fibre:
* The thick filaments are composed of the protein myosin.
* Each myosin molecule is made up of a monomer called meromyosin.
* The meromyosin have a globular head with a j short arm and a tail.
* The short arm have heavy meromyosin and the tail portion have light meromyosin.
* The head bears actin-binding site and an ATP binding site
* It also contains ATP ase enzyme that split ATP to generate energy for the contraction of muscle.
Actin filament:
* Actin has polypeptide subunits called globular actin or G – actin and filamentous form F – actin.
* Each thin filament is made of two F – actins helically wound to each other.
* Each F – actin is a polymer of monomeric G – actins, It also contains a binding site for myosin.
* The thin filament contain several regulatory protein like tropomyosin, troponin, which help in regulating the contraction of muscles along with actin and myosin.
Thick filament:
Each thick filament consists of many myosin molecules whose heads produce at opposite ends of the filament Portion of a thick filament
Thin filament:
A thin filament consists of two strands of actin subunits twisted into a helix plus two types of regulatory proteins (troponin and tropomyosin) Portion of a thin filament.

Functions of skeletal system
* Support -It forms a rigid framework and supports the weight of the body against gravity.
* Shape – It provides and maintains the shape of the body.
* Protection – It protects the delicate internal organs of the body.
* Acts as reservoir – It stores minerals such as calcium and phosphate. Fat (triglyceride) is stored in yellow bone marrow and represents a source of stored energy for the body.
* Locomotion – It acts as lever along with the muscles attached to it.
* Strength – It can withstand heavyweight and absorbs mechanical shock.
* Asa hemopoietic tissue – Red and white blood cells are produced in the bone marrow of the ribs, spongy bones of vertebrae and extremities of long bones.

The skull is composed of two sets of bones – cranial and facial bones. It consists of 22 bones of which 8 are cranial bones and 14 are facial, bones. The cranial bones form the hard protective outer covering of the brain and called the brain box. The capacity of the cranium is 1500 cm3.
These bones are joined by sutures which are immovable. They are paired parietal, paired temporal and individual bones such as the frontal, sphenoid, occipital and ethmoid. The large hole in the temporal bone is the external auditory meatus. In the facial bones maxilla, zygomatic, palatine, lacrimal, nasal are paired bones whereas mandible or lower jaw and vomer are unpaired bones. They form the front part of the skull.
A single U-shaped hyoid bone is present at the base of the buccal cavity. It is the only bone without any joint. Each middle ear contains three tiny bones- malleus, incus, and stapes collectively are called ear ossicles. The upper jaw is formed of the maxilla and the lower jaw is formed of the mandible.
The upper jaw is fused with the cranium and is immovable. The lower jaw is connected to the cranium by muscles and is movable. The most prominent openings in the skull are the orbits and the nasal cavity. The foramen magnum is a large opening found at the posterior base of the skull. Through this opening, the medulla oblongata of the brain descends down as the spinal cord.

The vertebral column is also called the backbone. It consists of 33 serially arranged vertebrae which are interconnected by cartilage known as an intervertebral disc. The vertebral column extends from the base of the skull to the pelvis and forms the main framework of the trunk. The vertebral column has five major regions.
They are the cervical, thoracic, lumbar, sacrum (5 sacral vertebrae found in the infant which are fused to form one bone in the adult), and coccyx (4 coccygeal vertebrae found in the infant which are fused to form one bone in the adult).
Each vertebra has a central hollow portion, the neural canal, through which the spinal cord passes. The first vertebra is called the atlas and the second vertebra is called the axis. Atlas is articulated with the occipital condyles. The vertebral column protects the spinal cord, supports the head, and serves as the point of attachment for the ribs and musculature of the back.

• There are 12 pairs of ribs.
• Each rib bone is connected dorsally to the vertebral column and ventrally to the sternum.
• It has two articulation surfaces on its dorsal end called bicephalic.
• The first 7 pairs of ribs are called true ribsorvertebro – sternal ribs.
• Dorsally they are attached to the thoracic vertebrae and ventrally connected to the sternum with the help of hyaline cartilages.
• The 8th, 9th, and 10th pairs of ribs do not articulate directly with the sternum but joined with the cartilaginous part of the seventh rib.
• These are called false ribs or vertebro – chondral ribs.
• The last 11th and 12th pairs of ribs are not connected ventrally.
• They are called floating ribs or vertebral ribs.
• Thoracic vertebrae ribs and sternum from the rib cage.

• The upper limbs are attached to the pectoral girdles.
• These are very light and allow the upper limbs a degree of mobility not seen anywhere else in the body.
• The girdle is formed of two halves.
• Each pectoral girdle consists of a clavicle or collar bone and a scapula.
• The scapula is a large triangular bone situated in the dorsal surface of the ribcage between the second and seventh ribs.
• It has an elevated expanded process called the acromion.
• The clavicle articulates this process.
• Below the acromion is a depression called the glenoid cavity which articulates with the head of the humerus to form the shoulder joint.
• Each clavicle is a long slender bone with two curvatures which lie horizontally and connect the axial skeleton with the appendicular skeleton.

• The upper limb consists of 30 separate bones and is specialized for mobility.
• The region between the shoulder and elbow is the humerus.
• The head of humerus articulates with the glenoid cavity of the scapula and forms the shoulder joint.
• The distel end of humerus articulates with the two forearm bones the radius and ulna
• Olecranon process is situated at the upper end of the ulna which forms the pointed portion of the elbow.
• The hand consists of carpals metacarpals and phalanges.
• Carpals the wrist bones 8 in number are arranged in two rows of four each and form a tunnel termed as carpal tunnel.
• Meta carpals the palm bones are 5 in number and phalanges the digit bones are 14 in number.

• The pelvic girdle is a heavy structure specialised for weight-bearing.
• It is composed of two hib bones called coxal bones that secure the lower limbs to the axial skeleton.
• Together with the sacrum and coccyx the hib bones form the basin-like bony pelvis.
• Each coxal bone consists of three fused bones ilium, ischium, and pubis.
• At the point of fusion of these three bones forms a deep hemispherical socket called the acetabulum present on the lateral surface of the pelvis.
• It receives the head of the femur at hip joint and helps in the articulation of the femur.
• Ventrally the two halves of the pelvic girdle meet and form the pubic symphysis containing fibrous cartilage.
• The ilium is the superior flaring portion of the hip bone. Each ilium forms a secure joint with the sacrum posteriorly.
• The ischium is a curved bar of bone. The ‘V’ shaped pubic bones articulate anteriorly at the pubic symphysis.
• The pelvis of male is deep and narrow with larger heavier bones and the female is shallow wide and flexible in nature and this helps during pregnancy which is influenced by female hormones.

• The lower limb consists of 30 bones which carries the entire weight of the erect body and is subjected to exceptional forces when we jump or run.
• The bones of the lower limbs are thicker and stronger than the upper limbs.
• Each lower limb consists of the thigh, the leg or the shank and the foot.
• The femur is the strongest and longest bone of the body.
• The head of femur articulates with the acetabulum of the pelvis to form the hip joint.
• The tibia and fibula form the skeleton of the shank.
• A thick triangular patella forms the knee cap which protects the knee joint arteriorly and improves the leverages of thigh muscles acting across the knee.
• The foot includes the bones of ankle the tarsus (7) the metatarsus (5) and the phalanges or toe ebones. (14)
• The foot supports our body weight and acts as a lever to propel the body forward while walking and running.
• The phalanges of the foot are smaller than those of the fingers.

• The typical long bone has a diaphysis, epiphysis, and membranes.
• A tubular diaphysis or shaft forms the long axis of the bone and has a central medullary cavity.
• The epiphyses are the bone ends.
• Compact bone forms the exterior of epiphyses and their interior contains spongy bone with red marrow.
• The region where the diaphysis and epiphysis meet is called metaphysics.
• The external surface of the entire bone except the joint surface is covered by a double-layered membrane called the periosteum.
• The outer fibrous layer is dense irregular connective tissue.
• The inner osteogenic layer consists of osteoblasts cell. ( bone-forming cells) and osteoclasts cells (E bone – destroying cells)
• There are primitive stem cells osteogenic cells that give rise to the osteoblasts.
• The periosteum is richly supplied with nerve fibres lymphatic vessels and blood vessels.
• Internal bone surfaces are covered with a delicate connective tissue membrane called the endosteum It also contains osteoblasts and osteoclasts cells.
• Between the epiphysis and diaphysis growth plate or epiphyseal plate is present.

Arthritis and osteoporosis are the major disorders of the skeletal system.
1. Arthritis: Arthritis is an inflammatory or degenerative disease that damages the joints. There are several types of arthritis.
(I) Osteoarthritis: The bone ends of the knees and other freely movable joints wear away as a person ages. The joints of the knees, hip, fingers, and vertebral column are affected.
(II) Rheumatoid arthritis: The synovial membranes become inflamed and there is an accumulation of fluid in the joints. The joints swell and become extremely painful. It can begin at any age but symptoms usually emerge before the age of fifty.
(III) Gouty arthritis or gout: Inflammation of joints due to accumulation of uric acid crystals or inability to excrete it. It gets deposited in synovial joints.
2. Osteoporosis: It occurs due to deficiency of vitamin D and hormonal imbalance. The bone becomes soft and fragile. It causes rickets in children and osteomalacia in adult females. It can be minimized with adequate calcium intake, vitamin D intake, and regular physical. activities.

Joints in the human body can be classified based on their structure and the type of movement they allow. A pivot joint, such as the one between the atlas and axis vertebrae, allows rotational movement. A gliding joint, found between the carpal bones, permits sliding movements in multiple directions. A saddle joint, located between the carpal and metacarpal bones, allows movement in two planes. A ball and socket joint, present between the humerus and the pectoral girdle, permits movement in all directions including rotation. A hinge joint, exemplified by the knee joint, allows movement primarily in one plane, similar to the opening and closing of a door. A condyloid or angular or ellipsoid joint, found between the radius and carpal bones, allows movement in two planes but not rotation. Each joint type is specialized for specific functions and ranges of motion required by different parts of the body.

Notes:
* The strongest muscle in the human: Massetter in cheeks
* The smallest muscle in the human: Middle ear in stapedius
* Well moving muscle: Tongue
* The largest muscle in the human: Buttock in Glutens Maximus
* The longest muscle in the human: Hip to knee (sartorius)
* Total number of bones is adults = 206

Exercise and physical activity fall into four basic categories: endurance, strength, balance, and flexibility. Endurance or aerobic activities increase the breathing and heart rate, keeping the circulatory system healthy and improving overall fitness by enhancing oxygen delivery to tissues. Strength exercises make the muscles stronger and help individuals stay independent and carry out everyday activities such as climbing stairs and carrying bags, which become increasingly important with age. Balance exercises help to prevent falls, which is a common problem in older adults, and many strengthening exercises also improve balance as a secondary benefit. Flexibility exercises help to stretch body muscles for more freedom of joint movements, reducing stiffness and improving the range of motion. Together, these four categories of physical activity contribute to overall health, functional capacity, and quality of life by addressing different aspects of physical fitness and well-being.