Additional Questions - Chapter 9 Locomotion and Movement 11th Biology Zoology Guide Samacheer Kalvi Solutions - SaraNextGen [2024-2025]

Updated By SaraNextGen

On April 24, 2024, 11:35 AM

Additional Questions & Answers
I. Choose The Correct Answer
Question 1.
Which of the following is not related to skeletal muscle?
(a) It is attached to the bone
(b) It is striated
(c) It is an involuntary muscle
(d) It brings about movement of the organ
Answer:
(c) It is an involuntary muscle
Question 2.
The skeletal system is derived from
(a) Ectoderm

(b) Endoderm
(c) Mesoderm
(d) Mesoglea
Answer:
(c) Mesoderm
Question 3.
The cytoplasm of the muscle fibre is .................
(a) Sarcolemma
(b) Sarcoplasm
(c) Ectoplasm
(d) Endoplasm
Answer:
(b) Sarcoplasm
Question 4.
The thick filament of muscle fibre is made up of ....................
(a) Actin
(b) Myosin
(c) Tropomyosin
(d) Troponin
Answer:
(b) Myosin
Question 5.
The cranial bones are .....................
(a) 22
(b) 14
(c) 8
(d) 3
Answer:
(c) 8
Question 6.
Where is the hyoid bone present?
(a) Cranium

(b) Appendicular skeleton
(c) Pectoral girdle
(d) Base of the buccal cavity
Answer:
(d) Base of the buccal cavity
Question 7.
The number of vertebrates is
(a) 8
(b) 12
(c) 5
(d) 33
Answer:
(d) 33
Question 8.
How many thoracic vertebrates are there?
(a) 7
(b) 12
(c) 5
(d) 4
Answer:
(b) 12
Question 9.
Rib cage protects
(a) Brain
(b) Kidney
(c) Lungs, heart, liver
(d) Heart
Answer:
(c) Lungs, heart, liver
Question 10.
The fore arm bones are the
(a) Tibia and fibula

(b) Radius and ulna
(c) Carpals and metacarpals
(d) Tarsal and metatarsals
Answer:
(b) Radius and ulna
Question 11.
The joint between carpal and metacarpals is
(a) Pivot joint
(b) Ball and socket joint
(c) Saddle joint
(d) Hinge joint
Answer:
(c) Saddle joint
Question 12.
Which of the following allows movement in only one direction?
(a) Pivot joint
(b) Ball and socket joint
(c) Saddle joint
(d) Hinge joint
Answer:
(d) Hinge joint
Question 13.
Which of the following disorders is related to endocrine gland?
(a) Myasthenia gravis
(b) Tetany
(c) Atrophy
(d) Muscular dystrophy
Answer:
(b) Tetany
Question 14.
Which of the following arthritis is related to protein metabolism?
(a) Osteoarthritis

(b) Rheumatoid arthritis
(c) Gouty arthritis
(d) Osteoporosis
Answer:
(c) Gouty arthritis
Question 15.
Which of the following is deficiency disorder?
(a) Osteoarthritis
(b) Rheumatoid arthritis
(c) Gouty arthritis
(d) Osteoporosis
Answer:
(d) Osteoporosis
II. Fill in the blanks
Question 1.
The sperm cells show ................. movement.
Answer:
Flagellar
Question 2.
Skeletal muscle is attached to the bone by a bundle of collagen fibres known as .............
Answer:
Tendon
Question 3.
The cytoplasm of the muscle fibre is called the ................
Answer:
Sarcoplasm
Question 4.

................... is a red coloured respiratory pigment of the muscle fibre.
Answer:
Myoglobin

Question 5.

..................... are the granules of stored glycogen.
Answer:
Glycosomes
Question 6.

................... is the functional unit of the skeletal muscle.
Answer:
Sarcomere
Question 7.
The thick filaments are composed of the protein ........................
Answer:
Myosin
Question 8.
The monomer of the myosin molecule is .................
Answer:
Meromyosin
Question 9.
The study of muscle is called .................
Answer:
Myology
Question 10.
The junction between the motor neuron and the sarcolemma of the muscle fibre is called the .................
Answer: 
Neuromuscular junction or motor end plate
Question 11.
When nerve impulse reaches a neuromuscular junction, ................ is released.
Answer:
Acetylcholine

Question 12.
In .................... contraction of the length of the muscle changes but the tension remains constant.
Answer:
Isotonic
Question 13.
In .................... contraction of the length of the muscle does not change but the tension of the muscle changes.
Answer:
Isometric
Question 14.
The oxidative fibres are called as ............................ fibres.
Answer:
Red muscle
Question 15.
Glycolytic fibres or white muscle fibres lack .......................
Answer:
Myoglobin
Question 16.
The skeletal system is derived from the....................
Answer:
Mesoderm
Question 17.
The RBCs and WBCs are produced in the ................ 
Answer:
Bone marrow
Question 18.
The large hole in the temporal bone is the ..................
Answer:
External auditory meatus

Question 19.
The lower jaw bone is called ....................
Answer:
Mandible
Question 20

.............. . is the only bone without any joint.
Answer:
Hyoid bone
Question 21.
The upper jaw is formed of the ...............
Answer:
Maxilla
Question 22.

......................... is the large opening found at the posterior base of the skull.
Answer:
Foramen magnum
Question 23.
Through foramen magnum the medulla oblongata continues as the .................
Answer:
Spinal cord
Question 24.
The first vertebra is called as the ..................
Answer:
Atlas
Question 25.
The second vertebra is called as the ...............
Answer:
Axis

Question 26.
The cranium protects the ..................
Answer:
Brain
Question 27.

.............. is the flat bone on the mid ventral line of the thorax.
Answer:
Sternum
Question 28.
The first seven pairs of ribs are called .................
Answer:
True ribs/vertebro-sternal
Question 29.
The 11th and 12th pairs of ribs are called as ................. ribs.
Answer:
Floating /vertebral
Question 30.
The 8th, 9th and 10th pairs of ribs are called .................. ribs.
Answer:
Flase /vertebro-chondral
Question 31.
Rib cage plays a role in .................
Answer:
Breathing
Question 32.

........................ is a depression in the pectoral girdle on which the head of the humerus form the shoulder joint.
Answer:
Glenoid cavity

Question 33.
..................... is situated at the upper end of the ulna which forms the pointed portion of the elbow.
Answer:
Olecranon process
Question 34.

...................... is the largest, longest and strongest bone in the body.
Answer:
Femur
Question 35.
The head of femur articulates with the  ....................... of the pelvis to form the hip joint.
Answer:
Acetabulum
Question 36.
The bone forming cells are called .............
Answer:
Osteoblasts
Question 37.
The bone destroying cells are called the ...................
Answer:
Osteoclasts
Question 38.
.................... cells give rise to the osteoblasts.
Answer:
Osteogenic
Question 39.
The internal bone surfaces are covered with a delicate connective tissue membrane called the ....................
Answer:
Endosteum
Question 40.
Between the epiphysis and diaphysis ................... is present.
Answer:
Epiphyseal plate/growth plate
Question 41.
The .................. are points of contact between the bones.
Answer:
Joints
Question 42.
Sutures of the flat skull bones are ............... joints.
Answer:
Fibrous
Question 43.

....................  are the freely movable joints.
Answer:
Synovial joints/Diarthroses joints
Question 44.
Between atlas and axis ................. joint is present.
Answer:
Pivot
Question 45.
Between the carpals ....................... joint is present.
Answer:
Plane/gliding
Question 46.
Between the carpal and metacarpal....................... joint is present.
Answer:
Addle
Question 47.
Between humerus and pectoral girdle ..................... joint is seen.

Answer:
Ball and socket
Question 48.

..................... is an autoimmune disorder affecting the action of acetylcholine.
Answer:
Myasthenia gravis
Question 49.
The removal of parathyroid gland results in ...................
Answer:
Tetany
Question 50
A traumatic pulling of the fibres produces a tear known as ...................
Answer:
Sprain
Question 51.

................  is an inflammatory or degenerative disease that damages the joints.
Answer:
Arthritis
Question 52.
The wearing away of the bone ends of the knees and other movable joints is called ...................
Answer:
Osteoarthritis
Question 53.
The inflammation of the synovial membranes is known as ...............
Answer:
Rheumatoid arthritis
Question 54.
Inflammation of joints due to accumulation of uric acid crystals is known as. .....................

Answer:
Gout
Question 55.
The deficiency of vitamin D and hormonal imbalance cause
Answer:
Osteoporosis
Question 56.
The deficiency of vitamin D causes ................ in children.
Answer:
Rickets
Question 57.
The deficiency of vitamin D causes ................... in adults.
Answer:
Osteomalacia
Question 58.

................... increase the breathing and heart rate.
Answer:
Endurance or aerobic activities
Question 59.

........................ protects us from heart attack.
Answer:
Exercise
III. Short Answer Questions
Question 1.
What is amoeboid movement?
Answer:
The movement of cells by streaming movements of the cytoplasm forming pseudo-podia is known as amoeboid movement, e.g., macrophages.

Question 2.
What is ciliary movement?
Answer:
The movement caused by the cilia is ciliary movement, e.g., ciliated epithelial cells of respiratory passage and genital tracts.
Question 3.
What is flagellar movement?
Answer:
The movement due to the lashing of flagella is known as flagellar movement, e.g., sperm cells.
Question 4.
What is muscular movement?
Answer:
The movement of hands, legs, jaws, tongue are caused by the contraction and relaxation of the muscle which is known as muscular movement.
Question 5.
What is fascicle?
Answer:
Each muscle is made up of bundles of muscle fibres called fascicle.
Question 6.
What are myofibrils?
Answer:
Each muscle fibre contains hundreds to thousands of rod-like structures called myofibrils that run parallel to its length.
Question 7.
What is epimysium?
Answer:
The connective tissue covering the whole muscle is the epimysium,
Question 8.
What is perimysium?

Answer:
The connective tissue covering around each fascicle is the perimysium.
Question 9.
What is endomysium?
Answer:
The connective tissue surrounding the muscle fibre is called the endomysium.
Question 10.
Distinguish between voluntary muscle and involuntary muscle.
Answer:

Question 11.
What is tendon?
Answer:
Skeletal muscle is attached to the bone by a bundle of collagen fibres known as tendon.
Question 12.
What is myoglobin?
Answer:
Myoglobin is a red-coloured respiratory pigment of the muscle fibre.
Question 13.
What is sarcoplasm?
Answer:
The cytoplasm of the muscle fibre is called the sarcoplasm.
Question 14.
What are Glycosomes?
Answer:
Glycosomes are the granules of stored glycogen that provide glucose during the period of muscle fibre activity.
Question 15.
What is sarcomere?
Answer:
The functional unit of the skeletal muscle is known as sarcomere.

Question 16.
Distinguish between thick filaments and thin filaments?
Answer:

Question 17.
What is meromyosin?
Answer:
The monomer of myosin molecule is called meromyosin.
Question 18.
Name the proteins which regulates the contraction of muscles?
Answer:
Actin, myosin, tropomyosin and troponin.
Question 19.
What is myology?
Answer:
The study of muscle is called myology.
Question 20.
What are oxidative fibres?
Answer:
The muscle fibres that contain numerous mitochondria and have a high capacity for oxidative phosphorylation are classified as oxidative fibres. They are also called red muscle fibres.
Question 21.
What are glycolytic fibres?
Answer:
The muscle fibres which contain a few mitochondria but possess a high concentration of glycolytic enzymes and large stores of glycogen are called glycolytic fibres. These lack myoglobin and hence these are pale. These muscle fibres are termed as white muscle fibres.
Question 22.
What is hydrostatic skeleton?
Answer:
The skeleton found in soft-bodied invertebrates is called hydrostatic skeleton. It is a fluid filled cavity encircled by muscles, e.g., earthworm.
Question 23.
Distinguish between exoskeleton and endoskeleton.
Answer:

Question 24.
What is a metaphysis?
Answer:
The bone region where the diaphysis and epiphyses meet is called the metaphysis.
Question 25.
What is periosteum?
Answer:
The external surface of the bone is covered by a double layered membrane called periosteum. What is endosteum?
Question 26.
What is endosteum?
Answer:
Internal bone surfaces are covered with a delicate connective tissue membrane called the endosteum.
Question 27.
What is sternum?
Answer:
Sternum is a flat bone on the mid ventral line of the thorax. It provides space for the attachment of the thoracic ribs and abdominal muscles.
IV. Give Long Answers
Question 1.
Explain the structure of a skeletal muscle fibre?

1. Each muscle fibre is thin and elongated.
2. It has multiple oval nuclei beneath sarcolemma.
3. The cytoplasm of the muscle fibre is called as sarcoplasm.
4. It contains glycosomes, the stored glycogen granules, myoglobin, respiratory pigment and sarcoplasmic reticulum.
5. Actin and myosin are muscle proteins present in the muscle fibre.
6. Each myofibril has a repeated series of dark and light bands called Abands and I-bands.
7. Each dark band has a lighter region in its middle called the $\mathrm{H}$-zone.
8. Each $\mathrm{H}$-zone is bisected vertically by a dark line called the M-line.
9. Each light I-band has a darker mid line area called the Z-disc.
10.Sarcomere is the functional unit of the skeletal muscle. It is a region of a myofibril between two successive Z-discs.
11. 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.
12.The invagination of the sarcolemma forms transverse tubules (T-tubules) and they penetrate into the junction between the $\mathrm{A}$ and I-bands.
Question 2.
Write the schematic presentation of muscle contraction?
Answer:

Question 3.
Explain the structure of contractile proteins?
Answer:
The thick filaments of the muscle has the protein mysoin. Each myosin molecule is made up of a monomer called meromyosin. It has a globular head, a short arm and a tail. The short arm constitutes the heavy meromyosin (HMM). The tail portion forms the light meromyosin (LMM). The head bears an actin-binding site and an ATP- binding site. It also contains ATPase enzyme that split ATP to generate energy for the contraction of muscle.

The thin filaments are composed of two intertwined actin molecules. It has polypeptide subunits called globular actin or G-actin and filamentous form or 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. Tropomyosin and troponin are other proteins which help in regulating the contraction of muscles along with actin and myosin.
Question 4.
Explain the types of skeletal muscle fibres?
Answer:
Skeletal muscle fibres are classified into three types. They are:
1. Slow - oxidative fibres
2. Fast - oxidative fibres
3. Fast-glycolytic fibres
1. Slow - oxidative fibres have low rates of myosin ATP hydrolysis but have the ability to make large amounts of ATP. These fibres are used for prolonged, regular activity such as long distance swimming. Long - distance runners have a high proportion of these fibres in their leg muscles.
2. Fast - oxidative fibres have high myosin ATPase activity and can make large amounts of ATP. They are particularly suited for rapid actions.

3. Fast - glycolytic fibres have myosin ATPase activity but cannot make as much ATP as oxidative fibres, because their source of ATP is glycolysis. These fibres are best suited for rapid, intense actions, such as short sprint at maximum speed.
Question 5.
Write the functions of skeletal system?
Answer:
Functions of skeletal system
1. Support -It forms a rigid framework and supports the weight of the body against gravity.
2. Shape - It provides and maintains the shape of the body.
3. Protection - It protects the delicate internal organs of the body.
4. 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.
5. Locomotion - It acts as lever along with the muscles attached to it.
6. Strength - It can withstand heavy weight and absorbs mechanical shock.
7. Asa haemopoietic tissue - Red and white blood cells are produced in the bone marrow of the ribs, spongy bones of vertebrae and extremities of long bones.
Question 6.
Explain the bones that form the skull?
Answer:
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 $1500 \mathrm{~cm} 3$.

These bones are joined by sutures which are immovable. They are a 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 one 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. 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.
Question 7.
Write a short note on the vertebral column?
Answer:
Vertebral column is also called the back bone. It consists of 33 serially arranged vertebrae which are interconnected by cartilage known as intervertebral disc. The vertebral column extends from the base of the skull to the pelvis and forms the main frame work 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 as the atlas and the second vertebra is called as 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.
Question 8.
Write a short note on Rib cage?
Answer:
There are 12 pairs of ribs. Each rib is a thin flat bone connected dorsally to the 

vertebral column and ventrally to the sternum. It has two articulation surfaces on its dorsal end, hence called bicephalic.
The first seven pairs of ribs are called 'true ribs or vertebro-stemal 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 (hyaline cartilage) 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. Therefore, they are called as 'floating ribs' or vertebral ribs. Thoracic vertebrae, ribs and sternum together form the ribcage. Rib cage protects the lungs, heart, liver and also plays a role in breathing.
Question 9.
Write a note on Pectoral girdle?
Answer:
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 half of the pectoral girdle consists of a clavicle or collar bone and a scapula.

The scapula is a large, thin, triangular bone situated in the dorsal surface of the ribcage between the second and seventh ribs. It has a slightly elevated ridge called the spine which projects as a flat, expanded process called the acromion. The clavicle articulates with 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 lies horizontally and connects axial skeleton with appendicular skeleton.
Question 10.
Write a note on the bones of the upper limb?
Answer:

The upper limb consists of 30 separate bones and is specialized for 1 mobility. The skeleton of the arm, 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 distal end of humerus articulates with the two forearm bones the radius and ulna. The forearm is the region between the elbow and the wrist.

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.
The anterior surface of the wrist has tunnel-like appearance, due to the arrangement of carpals with the ligaments. This tunnel is termed as carpal tunnel. Metacarpals, the pajm bones are 5 in number and phalanges the digits bones are 14 in number.
Question 11.
Explain the structure of Pelvic Girdle?
Answer:
The pelvic girdle is a heavy structure specialized for weight bearing. It is composed of two hip bones called coxal bones that secure the lower limbs to the axial skeleton. Together, with the sacrum and coccyx, the hip 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 ilium, ischium, and pubis a deep hemispherical socket called the acetabulum is present on the lateral surface of the pelvis.
It receives the head of the femur or thigh bone at the 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.
Question 12.
Write a note on the bones of lower limb?
Answer:
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.

The three segments of each.lower limb are the thigh, the leg or the shank and the foot. The femur is the single bone of the thigh. It is the largest, longest and strongest bone in the body.

The head of femur articulates with the acetabulum of the pelvis to form the hip joint. Two parallel bones, the tibia and fibula, form the skeleton of the shank.

A thick, triangular patella forms the knee cap, which protects the knee joint anteriorly and improves the leverage of thigh muscles acting across the knee. The foot includes the bones of ankle, the tarsus, the metatarsus and the phalanges or toe bones.

The foot supports our body weight and acts as a lever to propel the body forward, while walking and running. The tarsus is made up of seven bones called tarsals. The metatarsus consists of five bones called metatarsals. The arrangement of the metatarsals is parallel to each other. There are 14 phalanges in the toes which are smaller than those of the fingers.
Question 13.
Explain the structure of a typical long bone?
Answer:
A typical long bone has a diaphysis, epiphyses and membranes. A tubular diaphysis or shaft, forms the long axis of the bone. It is constructed of a thick 

collar of compact bone that surrounds a central medullary cavity or marrow 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 epiphyses meet is called the metaphysis. 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 (bone- forming cells) which secrete bone matrix elements and osteoclasts (bone-destroying cells). In addition, 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. The endosteum covers the trabeculae of spongy bone and lines the canals that pass through the compact bone. It also contains both osteoblasts and osteoclasts. Between the epiphysis and diaphysis epiphyseal plate or growth plate is present.
Question 14.
What are joints?
Answer:
The joints are points of contact between bones.
Question 15.
Explain the types of joints?
Answer:
(I) Fibrous joints or Synarthroses: They are immovable fixed joints in which no movement between the bones is possible. Sutures of the flat skull bones are fibrous joints.
(II) Cartilaginous joints or Amphiarthroses: They are slightly movable joints in which the joint surfaces are separated by a cartilage and slight movement is only possible, e.g., Joints of adjacent vertebrae of the vertebral column.

 (III) Synovial joints or Diarthroses joints: They are freely movable joints, the articulating bones are separated by a cavity which is filled with synovial fluid e.g., Pivot joint - between atlas and axis plane/gliding joint - between the carpals
- Saddle j oint - between the carpal and metacarpal
- Ball and socket joint - between humerus and pectoral girdle
- Hinge joint - knee joint
- Condyloid or angular or ellipsoid-joint between radius and carpal.
Question 16.
Write a short note on myasthenia gravis?
Answer:
Myasthenia gravis: An autoimmune disorder affecting the action of acetylcholine at neuromuscular junction leadihg 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.
Question 17.
Explain muscle fatigue?
Answer:
Muscle fatigue is the inability of a muscle to contract after repeated muscle contractions. This is due to lack of ATP and accumulation of lactic acid by anaerobic breakdown of glucose.
Question 18.
Explain muscle atrophy?
Answer:
A decline or cessation of muscular activity results in the condition called atrophy which results in the reduction in the size of the muscle and makes the muscle to become weak, which occurs with lack of usage as in chronic bedridden patients.
Question 19.
Write a short note on muscle pull?

Answer:
Muscle pull is actually a muscle tear. A traumatic pulling of the fibres produces a tear known as sprain. This can occur due to 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.
Question 20.
Write a short note on muscular dystrophy?
Answer:
The group of diseases collectively called the muscular dystrophy are associated with the progressive degeneration of skeletal muscle fibres, weakening the muscles and leading to death from lung or heart failure. The most common form of muscular dystrophy is called ' Duchene Muscular Dystrophy (DMD).
Question 21.
Explain the disorders of skeletal system?
Answer:
Arthritis and osteoporosis are the major disorders of 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 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.
Question 22.
Explain the basic categories of exercise and physical activity?
Answer:
Exercise and physical activity fall into four basic categories. Endurance, strength, balance and flexibility. Endurance or aerobic activities increase the breathing and heart rate. They keep the circulatory system healthy and improve overall fitness.
Strength exercises make the muscles stronger. They help to stay independent and cany out everyday activities such as climbing stairs and carrying bags.
Balance exercises help to prevent falls which is a common problem in older adults. Many strengthening exercises also improves balance.

Flexibility exercises help to stretch body muscles for more freedom of joint movements.