Locomotion and Movement

Statements A, B, D and E are correct while statement C is incorrect.

A neural signal reaching neuromuscular junction releases a neurotransmitter (Acetylcholine) which generates an action potential in the sarcolemma. This spreads through muscle fibre and causes the release of $\mathrm{Ca}^{++}$into the sarcoplasm. This $\mathrm{Ca}^{++}$binds to the subunit of troponin on actin filaments and thereby remove the masking of active site for myosin on actin and hence facilitates the formation of cross bridge.

(A) Incorrect : Human skull is dicondylic. The skull region articulates with the superior region of the vertebral column (Atlas) with the help of two occipital condyles.

(B) Correct : The joint present between the adjacent vertebrae of vertebral column is cartilaginous joints.

(C) Correct : There are 7 cervical vertebrae in human beings.

(D) Incorrect : All ribs of humans are bicephalic, i.e., they have two articulation surfaces on their dorsal end.

(E) Correct : The occipital bone of the skull articultes with the atlas vertebra via occipital condyles, forming the atlanto-occiptal joint.

• Arthritis is an inflammation of joints.

• Tetany is rapid spasms (wild contractions) in muscle due to low $\mathrm{Ca}^{++}$in body fluids.

• Muscular dystrophy is progressive degeneration of skeletal muscle mostly due to genetic disorder

• Myasthenia gravis is an autoimmune disorder affecting neuromuscular junction leading to fatigue, weakening and paralysis of skeletal muscle.

Hence, A-III, B-I, C-II, D-IV is the correct match.

To match the items in List-I (Location of Joint) with items in List-II (Type of Joint), consider the following relationships:

(A) Joint between humerus and pectoral girdle: This is a ball and socket joint because the humerus fits into the glenoid cavity of the pectoral girdle allowing a wide range of movement in all directions.

(B) Knee joint: This is a hinge joint, allowing movement primarily in one direction (flexion and extension).

(C) Joint between atlas and axis: This is a pivot joint because the atlas (C1 vertebra) rotates around the axis (C2 vertebra), allowing for the rotation of the head.

(D) Joint between carpals: This is a gliding joint because the bones in the wrist (carpals) slide over each other, allowing limited movement in various directions.

With this understanding, let's match List-I with List-II:

From the matching, the correct answer is:

Option A: A-II, B-III, C-IV, D-I.

Let's analyze each statement to determine its correctness regarding the mechanism of muscle contraction:

Statement A: It is initiated by a signal sent by CNS via sensory neuron.

This statement is incorrect because the signal for muscle contraction is sent by the central nervous system (CNS) via a motor neuron, not a sensory neuron. Sensory neurons carry information from sensory receptors to the CNS, whereas motor neurons carry signals from the CNS to muscles.

Statement B: Neurotransmitter generates action potential in the sarcolemma.

This statement is correct. When a motor neuron releases the neurotransmitter (typically acetylcholine) at the neuromuscular junction, it binds to receptors on the muscle cell membrane (sarcolemma) and generates an action potential.

Statement C: Increased Ca$^{++}$ level leads to the binding of calcium with troponin on actin filaments.

This statement is correct. When the action potential travels along the sarcolemma and into the muscle via T-tubules, it triggers the release of Ca$^{++}$ from the sarcoplasmic reticulum. The increase in Ca$^{++}$ levels leads to calcium binding with troponin on actin filaments.

Statement D: Masking of active site for actin is activated.

This statement is incorrect. The active sites on actin are initially masked by the protein tropomyosin. When Ca$^{++}$ binds to troponin, it causes a conformational change that moves tropomyosin away from the active sites on actin, thus exposing them for myosin binding. Therefore, masking is deactivated rather than activated.

Statement E: Utilising the energy from ATP hydrolysis to form cross bridge.

This statement is correct. The hydrolysis of ATP provides the energy necessary for the myosin heads to attach to actin, forming cross-bridges, and to perform the power stroke which leads to muscle contraction.

Based on this analysis, the correct statements are B, C, and E.

The most appropriate answer is Option A (B, C and E only).

The correct answer is option (2) as

Figure (a) represents skeletal muscle fibres which are closely attached to skeletal bones. In a typical muscle such as triceps and biceps, striated muscle fibres are bundled together in a parallel fashion.

Figure (b) represents smooth muscle fibres which are present in the wall of internal organs such as the blood vessels, stomach and intestine.

Figure (c) represents cardiac muscle fibres which are exclusively present in the heart.

To match List I (Types of Joints) with List II (Descriptions/Functions), let us consider each type:

Fibrous Joints (A): These joints are found where bones are closely fitted together, allowing very little or no movement, such as in the sutures of the skull. So, Fibrous joints correspond to: III. Skull, don't allow any movement

Cartilaginous Joints (B): These joints occur where the connection between the articulating bones is made up of cartilage, such as between vertebrae in the spine. These allow for limited movement. So, Cartilaginous joints correspond to: I. Adjacent vertebrae, limited movement

Hinge Joints (C): These include joints like the elbow and knee, where movement is primarily in one axis (like opening and closing a door). So, Hinge joints correspond to: IV. Knee, help in locomotion

Ball and Socket Joints (D): These joints, such as the hip and shoulder joints, allow for a wide range of movement including rotational. So, Ball and socket joints correspond to: II. Humerus and Pectoral girdle, rotational movement

The correct matching based on the descriptions and joint types is:

A-III, B-I, C-IV, D-II

Therefore, the correct answer is:

Option D: A-III, B-I, C-IV, D-II

A) Cartilaginous Joint : These joints are connected by cartilage and allow limited movement. They are found between adjacent vertebrae in the vertebral column.

B) Ball and Socket Joint : These joints consist of a ball-like structure fitting into a socket, allowing for a wide range of movement. They are found between the humerus and the pectoral girdle.

C) Fibrous Joint : These joints are connected by fibrous connective tissue and allow little or no movement. They are found between flat skull bones.

D) Saddle Joint : These joints have two bones with concave and convex surfaces that fit together, allowing movement in two planes. They are found between the carpal and metacarpal of the thumb.

So, the correct matching is :

A-II, B-IV, C-I, D-III

Option (A) is the correct answer because statements B and C are only correct statements while A and D are incorrect statements.

Muscle bundles are held together by collagenous connective tissue layer called fascia. Muscle bundles are called fascicles. The portion of the myofibril between two successive ‘Z’ lines is considered as functional unit of contraction called sarcomere.

The correct matchings are :

A - Palm bones are associated with the Metacarpals (II)

B - Wrist bones are also known as Carpals (III)

C - Ankle bones are referred to as Tarsals (IV)

D - Digit bones, i.e., the bones in the fingers and toes, are the Phalanges (I)

So, the correct answer is :

Option D : (A)-(II), (B)-(III), (C)-(IV), (D)-(I)

Option (3) is the correct answer as cardiac muscle fibres possess communication junctions (intercalated discs) at some fusion points that allow the cells to contract as unit, i.e., when one cell receives a signal to contract, its neighbours are also stimulated to contract.

Option (1) is incorrect as smooth muscle fibres are uninucleated.

Option (2) is incorrect as skeletal muscle fibres are multinucleated.

Option (4) is incorrect as the wall of blood vessels are made up of simple squamous epithelium.

Option (c) is the correct answer because length of A band remains unchanged during muscle contraction.

Option (a) is incorrect because actin filaments slide towards A-band.

Option (b) is incorrect because length of sarcomere decreases during muscle contraction.

Option (d) is incorrect because length of I-band decreases during muscle contraction.

Option (b) is the correct answer as inflammation of joints due to accumulation of uric acid crystals is known as gout.

Options (a) and (c) are incorrect because weakening of bones due to decreased bones mass, calcium deficiency, decreased levels of estrogen, etc., is termed as osteoporosis.

Option (d) is incorrect because inflammation of joints due to cartilage degeneration is known as osteoarthritis.

Option (c) is the correct answer as osteoporosis is due to decreased levels of oestrogen. Osteoporosis is an age-related disorder characterised by decreased bone mass hence, the chances of fractures increase.

Option (a) is the correct answer because Arthritis is inflammation of joints.

Option (c) is incorrect because myasthenia gravis is an immune disorder affecting neuro-muscular junction leading to fatigue, weakening and paralysis of skeletal muscle.

Option (d) is incorrect because muscular dystrophy is progressive degeneration of skeletal muscle mostly due to genetic disorder.

Option (b) is incorrect because tetany is rapid spasms in muscle due to low Ca⁺⁺ in body fluid.

The cervical vertebrae differ from the other vertebrae in having transverse formen. In vertebrates, cervical vertebrae are the vertebrae of the neck, immediately below the skull. In humans, they are the smallest of the true vertebrae.

Assertion is true, but reason is false. Calcium ions are required for skeletal muscle contraction. Sarcoplasmic reticulum releases Ca$^+$ on receiving stimulus on motor end plate. These ions bind with troponin units of action filament and expose the active sites to myosin for cross bridge formation at the expense of ATP. This is sliding filament theory of muscle contraction.