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During muscular contraction, which of the following events occur? [NEET 2021]
I. ‘ \(\mathrm{H}\) ‘ zone disappears
II. ‘ \(A\) ‘ band widens
III. ‘I’ band reduces in width
IV. Myosine hydrolyses ATP,
releasing the ADP and \(\mathrm{Pi}\)
V. Z-lines attached to actins are pulled inwards.
Choose the correct answer from the options given below.
(a) Statements I, III, IV, and V are correct and statement II is incorrect and can be corrected as During muscular contraction by utilising energy from ATP hydrolysis the myosin head binds to the exposed active sites on actins to form a cross bridge.
This pulls the attached actin filaments towards the center of \(\)A\(\) band. This movement contricts’A’ band.
Match the List I with List II. [NEET 2021]
\(
\begin{array}{|l|l|l|l|}
\hline & \text { List I } && \text { List II } \\
\hline \text { a } & \text { Scapula } & \text { i } & \text { Cartilaginous joints } \\
\hline \text { b } & \text { Cranium } & \text { ii } & \text { Flat bone } \\
\hline \text { c } & \text { Sternum } & \text { iii } & \text { Fibrous joints } \\
\hline \text { d } & \text { Vertebral column } & \text { iv } & \text { Triangular flat bone } \\
\hline
\end{array}
\)
Choose the correct answer from the options given below.
(d) Scapula It is a flat, triangular-shaped bone. It is located in the upper thoracic region on the dorsal surface of the ribcage.
Cranium is the part of the skull that encloses the brain. They have immovable fibrous joint. Sternum is the flat bone located in the middle of the chest. Also referred to as the breastbone.
Vertebral column It is a series of approximately 33 bones called vertebrae. They have cartilaginous-type joints designed for weight bearing.
Chronic autoimmune disorder affecting neuro muscular junction leading to fatigue, weakening, and paralysis of skeletal muscle is called as [NEET 2021]
(c) Myasthenia gravis is defined as an autoimmune neuromuscular disorder that leads to fluctuating muscle weakness and fatigue. The cause of this disease is circulating antibodies that will block acetylcholine receptors at the post-synaptic neuromuscular junctions. Other options can be explained as :
Muscular dystrophy is a disease
characterised by progressive degeneration of muscle fibres without the involvement of nervous system.
Gout is caused by two conditions that include one which occurs due to excessive formation of uric acid and another by the inability to excrete it. Uric acid deposits in the form of monosodium salts. Arthritis is the swelling and tenderness of one or more joints. It is caused by injury, abnormal metabolism, and genetic makeup.
Select the incorrectly matched pair from the following. [NEET (Oct.) 2020]
(a) The incorrect match pair is option (a). It can be corrected as
Chondrocytes are cartilage cells. The intercellular material of cartilage is solid, pliable, and resists compression. Cells of this tissue are called chondrocytes which are enclosed in small cavities within the matrix secreted by them.
Match the following columns and select the correct option. [NEET (Sep.) 2020]
\(
\begin{array}{|c|c|c|c|}
\hline & \text { Column-I } & & \text { Column-II } \\
\hline \text { A } & \text { Floating Ribs } & \text { (i) } & \text { Located between second and seventh ribs } \\
\hline \text { B } & \text { Acromion } & \text { (ii) } & \text { Head of the Humerus } \\
\hline \text { C } & \text { Scapula } & \text { (iii) } & \text { Clavicle } \\
\hline \text { D } & \text { Glenoid cavity } & \text { (iv) } & \text { Do not connect with the sternum } \\
\hline
\end{array}
\)
(c) The correct option is (c). It can be explained as follows 11th and 12th pairs of ribs are not connected ventrally with sternum and are, therefore, called floating ribs.
Acromion is a flat expanded process of the spine of the scapula. The lateral end of the clavicle articulates with the acromion process. The scapula is a flat triangular bone in the dorsal part of the thorax between the 2nd and the 7th rib.
Glenoid cavity of the scapula articulates with the head of the humerus to form the shoulder joint.
Match the following columns and select the correct option from the codes given below. [NEET (Oct.) 2020]
\(
\begin{array}{|l|l|r|l|}
\hline & {\text { Column – I }} && {\text { Column – II }} \\
\hline \text { (a) } & \text { Gout } & \text { (i) } & \text { Decreased levels of estrogen } \\
\hline \text { (b) } & \text { Osteoporosis } & \text { (ii) } & \text { Low } \text { Ca }^{++} \text {ions in the blood } \\
\hline \text { (c) } & \text { Tetany } & \text { (iii) } & \text { Accumulation of uric acid crystals } \\
\hline \text { (d) } & \text { Muscular dystrophy } & \text { (iv) } & \text { Auto immune disorder } \\
\hline
\end{array}
\)
(b) The option (b) is the correct match which is as follows
Gout is inflammation of joints due to the accumulation of uric acid crystals.
Osteoporosis occurs due to decreased levels of oestrogen in females. It is an age-related disorder characterised by decreased bone mass and increased chances of fractures.
Tetany is rapid spasms (wild contractions) in muscle when there is low \(\mathrm{Ca}^{2+}\) ions in the blood. Muscular dystrophy is the progressive degeneration of skeletal muscle mostly due to genetic disorder.
Select the correct option. [NEET (National) 2019]
(c) The statement that there are seven pairs of vertebrosternal, three pairs of vertebrochondral and two pairs of vertebral ribs is correct.
Rest of the statements are incorrect. Correct information about the statements is as follows Vertebrosternal ribs are the first seven pairs of true ribs that are attached dorsally to thoracic vertebrae and ventrally to the sternum.
Vertebrochondral ribs (8th, 9 th, and 10th pairs) are false ribs which are not attached to the sternum directly. They are attached to the seventh rib with the help of hyaline cartilage. Vertebral ribs are the last two pairs of floating ribs which are attached to vertebrae dorsally and are not attached ventrally.
Match the following joints with the bones involved [NEET (Odisha) 2019]
Column-I Column-II
(a) Gliding joint (i) Between carpal and metacarpal of thumb
(b) Hinge joint (ii) Between Atlas and Axis
(c) Pivot joint (iii) Between the carpals
(d) Saddle joint (iv) Between the Humerus and Ulna
Select the correct option from the following:
(a) The correct matches are
a. Gliding joint-(iii) Between the carpals
b. Hinge joint – (iv) Between humerus and ulna
c. Pivot joint – (ii) Between atlas and axis
d. Saddle joint-(i)Between carpal and metacarpal of thumb
Which of the following muscular disorders is inherited? [NEET (National) 2019]
(a) Muscular dystrophy is an inherited muscular disorder in which the skeletal muscles degenerate progressively. It is caused due to the absence of dystrophin protein which helps to keep muscle cells intact. Myasthenia gravis is an autoimmune neuromuscular disease that causes paralysis of skeletal muscles. Botulism is a type of food poisoning
caused by the bacterium Clostridium botulinum. Tetany is an involuntary muscle
contraction caused due to the level of calcium in the body.
Calcium is important in skeletal muscle contraction because it [NEET 2018]
(c) Calcium plays a key regulatory role in muscle contraction. \(\mathrm{Ca}^{2+}\) ions bind to troponin and changes its shape and position. This, in turn, alter the shape and position of tropomyosin, and hence, the active sites on F-actin are exposed. Due to this, myosin cross-bridges are able to bind to these active sites and muscle contraction occurs.
Which of the following is not an autoimmune disease? [CBSE AIPMT 2018]
(d) Myasthenia gravis is an autoimmune disease of the neuromuscular junction which results from antibodies that block or destroy nicotinic acetylcholine receptors (AChR) at the junction between the nerve and muscle.
Which of the following hormones can play a significant role in osteoporosis? [NEET 2018]
(d) Osteoporosis has 3 causes: excess parathyroid hormone, advanced age, and lack of estrogen in older females. Estrogen promotes the activity of osteoblast and inhibits osteoclast. Parathormone promotes mobilisation of calcium from bone into blood. Excessive activity of parathormone causes demineralisation leading to osteoporosis.
The pivot joint between atlas and axis is a type of [NEET 2017]
(b) Synovial joints are freely movable joint which allow considerable movements. Pivot joint is a type of synovial joint which provide rotational movement as in between atlas and axis vertebrae of the vertebral column.
Out of ‘ \(X\) ‘ pairs of ribs in humans only ‘ \(Y\) ‘ pairs are true ribs. Select the option that correctly represents values of \(X\) and \(Y\) and provides their explanation. [NEET 2017]
(d) In humans, 12 pairs of ribs are present out of which 7 pairs of ribs (1st to 7 th pair) are dorsally attached to vertebral column and ventrally to the sternum.
Name the ion responsible for unmasking of active sites for myosin for cross-bridge activity during muscle contraction. [NEET-II 2016]
(a) Calcium ion plays an important role in muscle contraction. Calcium ions bind to troponin causing a change in its shape and position. Thus, in turn, alters the shape and position of tropomyosin to which troponin binds. This shift exposes the active sites on F-actin molecules. Myosin cross-bridge are then able to bind to these active sites.
Osteoporosis, an age-related disease of skeletal system, may occur due to [NEET-II 2016]
(c) Osteoporosis is the reduction in bone mineral density, resulting in bones that are brittle and liable to fracture. Infection, injury, and synovitis can cause localised osteoporosis of adjacent bone. Generalised osteoporosis is common in the elderly and in women after menopause. After menopause the estrogen levels in blood plasma are much reduced. Estrogen helps to regulate bone cells called osteoclasts which are responsible for building new bone. When estrogen levels drop fewer osteoclasts are produced resulting in osteoporosis.
Lack of relaxation between successive stimuli in sustained muscle contraction is known as [NEET-I 2016]
(a) Tetanus refers to the continued state of contraction of a muscle resulting from the summation of a series of rapid muscular contractions (twitches) that are induced by repeated stimulation of the muscle.
Smooth muscles are [NEET 2016, Phase II]
(a) Smooth muscles are involuntary, fusiform, and non-striated. These muscles are located in the inner walls of hollow visceral organs of the body like alimentary canal, reproductive tract, etc.
They do not exhibit any striation and are smooth in appearance. Their activities are under autonomic and hormonal control and thus they are also known as involuntary muscles. Hence, option (a) is correct.
Which of the following is not a function of the skeletal system? [CBSE AIPMT 2015]
(a) The adult human skeletal system consists of 206 bones, as well as a network of tendons, ligaments, and cartilage that connects them.
The skeleton serves six major functions: support, movement, protection, production of blood cells, storage of minerals, and endocrine regulation. Hence, the Production of body heat is not a function of the skeletal system. So, the correct answer is ‘Production of body heat’.
Which of the following joints would allow no movements? [CBSE AIPMT 2015]
(c) Fibrous or immovable joints are the joints in which no movement occurs between the bones concerned. White fibrous tissue is present between the ends of the bones. Fibrous joint occurs between the bones of the skull called sutures and the joints between the teeth and the maxilla and the teeth and the mandible.
Sliding filament theory can be best explained as [CBSE AIPMT 2015]
(a) During muscle contraction, the laterally projecting heads (cross-bridges) of the thick myosin myofilaments come in contact with the thin actin myofilaments and rotate on them. This pulls the thin myofilaments toward the middle of the sarcomere, past the thick myofilaments. The Z lines come closer together and the sarcomere becomes shorter. Length of the \(A\) band remains constant. Myofilaments (both actin and myosin) stay the same length. Free ends of actin myofilaments move closer to the centre of the sarcomere, bringing \(\mathrm{Z}\) lines closer together. I bands shorten and \(\mathrm{H}\) zone narrows. Similar action in all the sarcomeres results in shortening of the entire myofibril and thereby of the whole fibre and the whole muscle.
Glenoid cavity articulates [CBSE AIPMT 2015]
(b) Upper rounded end of the humerus (bone of arm) is called the head that articulates into the glenoid cavity of the pectoral girdle (shoulder girdle) of scapula or shoulder blade bone.
Select the correct matching of the type of the joint with the example in the human skeletal system. [CBSE AIPMT 2014]
(d) Gliding joint – between carpals
Explanation of the correct option:
Gliding joints are joints made up of two bones where the articular surfaces (surface of connection) of the bones are flat, which allows the bone to slide over one another.
Stimulation of a muscle fiber by a motor neuron occurs at [CBSE AIPMT 2014]
(a) A neuron that transmits a stimulus to muscle tissue is called motor neuron. A motor unit consists of a single motor neuron (nerve cell) and the muscle fibres it innervates. The portion of the muscle plasma membrane (sarcolemma) that lies beneath the nerve endings (axon terminals) is called the motor end plate. The axon terminals and the motor end plate together constitute the neuro-muscular junction or neuromotor junction.
Select the correct statement with respect to locomotion in humans. [NEET 2013]
(d) Thoracic vertebrae are 12 in numbers. Joints between adjacent vertebrae are cartilagenous joints and the opposing surfaces are connected by fibrocartilage which allows very little movement. Osteoporosis is a disease characterised by low bone mass and loss of bone tissue that may lead to weak and fragile bones. Osteoporosis occurs when there is an imbalance between new bone formation and old bone resorption. Generalised osteoporosis is common in elderly people and in women following menopause. In osteoporosis, the osteoblastic (bone forming) activity in the bone usually is less than normal and consequently the rate of bone deposition is depressed. Estrogens inhibit osteoclastic (bone resorption) activity in the bones and therefore stimulate bone growth. After menopause, almost no estrogens are secreted by ovaries. This estrogen deficiency leads to increased osteoclastic activity in the bones, decreased bone matrix, and decreased deposition of bone calcium and phosphate. In some women, this effect result in osteoporosis.
The \(\mathrm{H}-z o n e\) in the skeletal muscle fibre is due to [NEET 2013]
(a) Each muscle fibre has many parallelly arranged myofibrils. Each myofibril contains many serially arranged units called sarcomere which are the functional units. Each sarcomere has a central ‘A’ band made of thick myosin filaments and two half ‘I’ bands made of thin actin filaments on either side of it marked by ‘ \(\mathrm{Z}\) ‘ lines. In a resting state, the edges of thin filaments on either side of the thick filaments partially overlap the free ends of the thick filaments leaving the central part of the thick filaments. This central part of thick filament, not overlapped by thin filaments is called the ‘ H ‘ zone.
The characteristic and an example of a synovial joint in humans is [NEET 2013]
\(
\begin{array}{|l|l|l|}
\hline & \text { Characteristics } & \text { Examples } \\
\hline \text { A } & \text { lymph filled between two bones, limited movement } & \text { gliding joint between carpals } \\
\hline \text { B } & \text { fluid cartilage between two bones, limited movements } & \text { Knee joint } \\
\hline \text { C } & \text { fluid filled between two joints, provides cushion } & \text { skull bones } \\
\hline \text { D } & \text { fluid filled synovial cavity between two bones } & \text { joint between atlas and axis } \\
\hline
\end{array}
\)
(d) Joint between atlas and axis is a pivot joint, a type of synovial joint. Synovial joints are characterised by the presence of fluid-filled cavity between the articulating surface of the two bones.
During muscle contraction in humans, the [NEET Karnatak 2013]
(b) According to sliding-filament theory of muscle contraction, the actin and myosin filaments slide past each other with the help of cross-bridge to reduce the length of the sarcomeres. The smallest unit of muscle contraction is a sarcomere (which is delineated by Z-lines). As a muscle contracts, the \(\mathrm{Z}\) lines come closer together (shortening sarcomere), the width of the I bands decreases, the width of the \(\mathrm{H}\) zones decreases, but there is no change in the width of the \(\mathrm{A}\) band. During relaxation, cross-bridges disappear and actin filaments slide back from A-bands, the width of the I bands and \(\mathrm{H}\) zones increases, but there is still no change in the width of the A band.
Select the correct statement with respect to disorders of muscles in humans. [NEET Karnatak 2013]
(a) Myasthenia gravis is an autoimmune disorder in which autoantibodies bind to cholinergic receptors on muscle cells and impair the ability of the neurotransmitter acetylcholine to induce muscular contraction. This leads to fatigue, weakening, and paralysis of skeletal muscles of mouth and throat which may prevent normal swallowing. Gouty arthritis is caused either due to excessive formation of uric acid or the inability to excrete it. It gets deposited in synovial joints and causes inflammation. Osteoporosis is a disease in which bone loses minerals and fibres from its matrix. Major causative factors of osteoporosis are imbalances of hormones like calcitonin of thyroid, parathormone of parathyroids, sex hormones, and deficiencies of calcium and vitamin D. Muscular dystrophy is an inborn abnormality of muscles associated with dysfunction and ultimately with deterioration.
Select the correct statement regarding the specific disorder of muscular or skeletal system. [CBSE AIPMT 2012]
(b) Muscular dystrophy is characterised by progressive skeletal muscle weakness, defects in muscle proteins, and the death of muscle cells and tissue.
Myasthenia gravis is an autoimmune neuromuscular disease in which muscle becomes weak, which is caused by circulating antibodies that block acetylcholine receptors at the postsynaptic neuromuscular junction inhibiting the excitatory effects of the acetylcholine.
Gout is inflammation of joints which is caused by elevated levels of uric acid in the blood which crystallises and the crystals are deposited in joints, tendons, and surrounding tissues.
Which one of the following pairs of chemical substances, is correctly categorised? [CBSE AIPMT 2012]
(c) Troponin is a protein which is found on actin filament and myosin protein is found in myosin filament. Both actin and myosin are complex proteins in striated muscles.
Thymosin is a hormone secreted by the thymus that stimulates the development of T cells.
Prolactin is a hormone released by the pituitary gland that stimulates breast development and milk production in women. Rhodopsin, also known as visual purple, is not a hormone. It is a biological pigment in photoreceptor cells of the retina that is responsible for the first events in the perception of light.
The type of muscle present in our [CBSE AIPMT 2011]
(c) Cardiac muscles are found in the wall of the heart. It is involuntary and slightly striated. Smooth muscles are found in the gastrointestinal tract. These are non-striated and involuntary. Striated (or skeletal) muscles are found in the limbs and body walls. These muscles are voluntary (under the control of the animal’s will) and show dark and light bands thus are striated.
Three of the following pairs of the human skeletal parts are correctly matched with their respective inclusive skeletal category and one pair is not matched. Identify the non-matching pail. [CBSE AIPMT 2011]
\(
\begin{array}{|l|l|l|}
\hline & \text { Pair of skeletal parts } & \text { Category } \\
\hline \text { (a) } & \text { Sternum and ribs } & \text { Axial skeleton } \\
\hline \text { (b) } & \text { Clavicle and glenoid cavity } & \text { Pelvic girdle } \\
\hline \text { (c) } & \text { Flumerus and ulna } & \text { Appendicular skeleton } \\
\hline \text { (d) } & \text { Malleus and stapes } & \text { Ear ossicles } \\
\hline
\end{array}
\)
(b) Each pectoral girdle consists of two bones, the clavicle, and scapula. The scapula (shoulder blade) consists of a sharp ridge, the spine, and a triangular body. The end of the spine projects as a flattened and expanded process called acromion. This process articulates with the clavicle. At the lateral end of the superior of the scapula is projection of the anterior surface called the coracoid process, to which the tendons of the muscles attach. At the point where the superior and lateral borders of the scapula meet there is the lateral angle which presents a shallow articular surface termed as glenoid cavity into which the head of the humer is articulated.
Which one of the following is the correct description of a certain part of a normal human skeleton? [CBSE AIPMT 2010]
(a) The bones of skulls are joined by white fibrous tissue which sustains no movement between the skull bones. This kind of joint is classified as
fibrous or immovable joints. Thus, parietal and temporal bone of the skull are joined by fibrous joints. First cervical vertebra, atlas, joins the second cervical vertebra axis to form a joint (pivot joint) which allows movement in one plane. The atlas supports the head and allows movement of head over neck.
The last two pairs of ribs are called floating ribs because their anterior ends are not attached to either the sternum or the cartilage of the anterior rib.
Glenoid cavity is a depression to which humerus articulates.
Low \(\mathrm{Ca}^{++}\)in the body fluid may be the cause of: [CBSE AIPMT 2010]
(a) Tetany is caused by reduction in the calcium level due to underactive parathyroid hormone.
Which one of the following is the correct matching of three items and their grouping category? [CBSE AIPMT 2009]
(a) The pelvic girdle is formed by two innominate bones (hip bones). Each innominate bones consists of three separate bones, ilium, ischium, and the pubis.
Elbow joint is an example of [CBSE AIPMT 2009]
(a) Hinge joint is a form of diarthrosis (freely movable joint) that allows angular movement in one plane only, increasing or decreasing the angle between the bones. Examples are – knee joint and elbow joint.
Which one of the following is the correct pairing of a body part and the kind of muscle tissue that moves it?
[CBSE AIPMT 2009]
(d) Smooth muscles are plain, non-striated, involuntary, or unstriped muscles due to the absence of striations. These occur in the walls of hollow internal organs, in capsules of lymph glands, spleen, etc., in iris and ciliary body of eyes, skin dermis, penis, and other accessory genitalia, etc.
Which one of the following items gives its correct total number? [CBSE AIPMT 2008, 2007]
(a) In a human’s total number of ribs are Fourteen (14). These are three types
(1) True ribs-These are 7 in number.
(2) False ribs- These are two (2) in number.
(3) Floating ribs-These are 4 in number.
In the human body, which one of the following is anatomically correct? [CBSE AIPMT 2007]
(d) Floating ribs are 2- pairs (\(11^{\text {th }}\) and \(12^{\text {th }}\) pair) which are not attached to sternum.
The contractile protein of skeletal muscle involving ATPase activity is [CBSE AIPMT 2006, 1998]
(c) Myosin is a contractile protein that interacts with actin to bring about the contraction of muscle or cell movement. The type of myosin molecule found in muscle fibres consists of a tail, by which it aggregates with other myosin molecules to form so-called thick filaments, and a globular head, which has sites for the attachment of actin and ATP molecule. Troponin, tropomyosin, and a-actinin are the actin in the thin filament.
An acromian process is characteristically found in the [CBSE AIPMT 2005]
(b) Each half of the pectoral girdle is made up of two bones scapula and clavicle. At the outer angle of scapula is a shallow socket known as glenoid cavity into which fits the head of humerus bone to form a shoulder joint. Above glenoid cavity project two processes – acromion process and coracoid process. Acromion process extends over the glenoid cavity and articulates with clavicle to form shoulder girdle. Coracoid process is like a hook and is smaller than acromion process.
Which of the following pairs is correctly matched? [CBSE AIPMT 2005]
(b) Gliding joint permits sliding movements of two bones over each other. Hinge joint allows movements in one plane only. Knee joint, elbow joint, and ankle joint are of this type. Cartilaginous joint is a slightly movable joint and is found between the centre of vertebrae, at the pubic symphysis, and between ribs and sternum. Fibrous joint is an immovable joint which occur between the bones of cranium.
What will happen if ligaments are torn? [AIPMT 2002]
(b) Ligaments join a bone with another bone in movable/synovial joints. Torn ligaments make movement at joints very painful and restricted.
ATPase enzyme needed for muscle contraction is located in [CBSE AIPMT 2004]
(c) During muscular contraction myosin cross bridges heads. Myosin is not only an actin binding protein, it is also an ATPase (an enzyme) which is activated by \(\mathrm{Ca}^{2+}\) and \(\mathrm{Mg}^{2+}\) ions. Hence, ATPase enzyme is located in myosin.
Which cartilage is present at the end of long bones? [AIPMT 2002]
(b) Cartilage is an important component of skeleton. It consists of a firm matrix containing collagen and elastin fibres and cells in fluid-filled lacunae. Cartilage has many types. Elastic cartilage occurs in the pinna and external auditory canal of the ear, epiglottis, Eustachian tubes and tip of the nose to make these organs flexible. Fibrous cartilage is very strong yet has a degree of flexibility. It is found in the intervertebral discs where it acts as a cushion and in pubic symphysis where it allows parturition without damage to the girdle. Hyaline cartilage occurs in sternal ribs where it allows expansion of chest during inspiration. It also forms the tracheal and bronchial rings and supports larynx and nasal septum and also at the end of long bones.
Which statement is correct for muscle contraction? [AIPMT 2001]
(a) When Ca+ ions combine with troponin contraction of muscle initiates. During contraction, die Z lines come closer together and the sarcomere becomes shorter. The length of A band remains constant. I bands shortens and \(\mathrm{H}\) zone narrows.
What is sarcomere? [AIPMT 2001]
(d) A striated muscle fibre is bounded by sarcolemma. It shows alternating dark and light cross bands, the striations. Dark band is called \(\mathrm{A}\) band which has at its middle a light zone termed \(\mathrm{H}\) zone. Light band is known as I band which is crossed through its centre by a dark membrane called \(Z\) line. The part of the muscle fibre between two successive \(Z\) lines functions as a contractile unit called sarcomere.
Sternum is connected to ribs by [AIPMT 2000]
(c) Sternum is connected to ribs by hyaline cartilage (= giving a shiny glass like appearance and gives flexibility and support at the joints). Stemum is also called breast bone. It is a narrow, elongated and flattened structure, present just under the skin in the middle of front of the chest. It consists of three parts – manubrium, mesosternum and xiphoid process.Manubrium is the thickest, strongest part and articulates with the clavicle of pectoral girdle and first pair of ribs. Mesosternum provide articulation to second to sixth pairs of ribs and xiphoid process (also called metasternum) articulates with seventh pair of ribs in association with mesosternum.
Bone related with skull is [AIPMT 2000]
(c) Pterygoid is a process that extends from sphenoid bone of skull to form a plate like structure. Above the glenoid cavity of scapula is present two processes – acromion and coracoid. Coracoid process is like a hook and is smaller that acromion process projecting upwards. Atlas is first cervical vertebra. Arytenoid is a cartilage that forms part of larynx.
What is the name of the joint between ribs and sternum? [AIPMT 2000]
(a)Cartilaginous joint is present between ribs and sternum. It allows only limited movement. An angular joint allows movement in two directions side to side and back and forth. Wrist and metacarpophalangeal joints are of this type. Gliding joint permits sliding movements of two bones over each other, e.g. joints between the sternum and clavicles. Fibrous joints do not allow movement and are present between the bones of the cranium.
The joint between atlas and axis is called [NEET 2024]
(c) Pivot joint is present between the atlas and the axis in humans. In this joint articular end of one bone is fixed while the other can rotate over it. In an angular joint, an oval condyle of one bone fits into an elliptical concavity of the other, e.g. wrist and metacarpophalangeal joints. The hinge joint allows movements in one plane only, e.g. knee joint. In a saddle joint, a small projection of one bone fits into a saddlelike depression of another bone.
Ligament is a [CBSE AIPMT 1999]
(b) Ligaments are made up of inelastic white fibrous tissue and connect bones at joints. It is also known as articular ligament, articular larua, or fibrous ligament.
Tendon is made up of [CBSE AIPMT 1999]
(b) The modified white fibres tissue form cords called tendons which connect muscles with the bones.
Parathormone deficiency produces muscle ramps or tetany as a result of [AIPMT 1999]
(a) Parathormone released by the parathyroid gland elevates the level of \(\mathrm{Ca}^{2+}\) in blood. The deficiency of this hormone lowers blood \(\mathrm{Ca}^{2+}\). As a result, the excitability of muscles and nerves increases causing tetany-sustained contraction.
Which of the following is the contractile protein of a muscle? [AIPMT 1998, 2006]
(c) Myosin is a contractile protein of muscle. Primary myofilaments are made up of this protein. Each myosin filament is a polymerised protein made of many monomeric protein called meromyosins. Secondary myofilaments are composed of a protein actin, having with it two regulatory proteins: tropomyosin and troponin. Myosin interacts with actin to bring about the contraction of the muscle or cell movement. Tubulin is a protein of which the microtubules of cells are formed.
The functional unit of contractile system in striated muscle is [NEET 2024]
(a) Sarcomere is the functional unit of myofibril. It contains two types of protein filaments called actin and myosin. These filaments slide upon each other to bring about the contraction of the muscles.
Total number of bones in each limb of a man is [AIPMT 1998]
(b) Each arm and each leg contains 30 bones. Flexors work antagonistically with extensors. E.g. each arm contains humerus in the upper arm, radius, and ulna in the forearm, 8 carpals in the wrist, 5 metacarpals in the palm, and 14 phalanges in the fingers. Each hind limb contains femur in the thigh, patella in the knee, tibia, and fibula in the shank, 7 tarsals in the ankle, 5 metatarsals in the sole, and 14 phalanges in the toes.
The number of floating ribs in the human body is [AIPMT 1995]
(b) There are twelve pairs of ribs that form the bony lateral walls of the thoracic cage. The first seven pairs are called true ribs; eight, ninth and tenth pairs are called false ribs. The last two pairs of ribs are called floating ribs because their anterior ends are not attached either to the sternum or the cartilage of another rib. The floating ribs protect the kidneys.
Which of the following components is a part of the pectoral girdle? [AIPMT 1994]
(c) The pectoral girdle lies on the posterolateral aspect of the upper region of the thorax. It consists of 2 bones: scapula and clavicle. The scapula, also called the shoulder blade, is a large, flat, triangular bone placed at the back of the shoulder. It has at its lateral angle a shallow concavity, the glenoid cavity, for the articulation of the head of the humerus. Acetabulum and ilium are parts of the pelvic girdle. Sternum is a long, narrow, flat vertical bone in the middle of the front wall of the chest.
The type of joint between the human skull bones is called [AIPMT 1994]
(c) Fibrous joint is present between the human skull bones. It does not allow movement because the bones are held firmly together by bundles of strong white collagen fibres. Cartilaginous joints are present between the centra of vertebrae, at the pubic symphysis, and between ribs and sternum. Knee joint, elbow joint, and ankle joint are types of hinge joint. Synovial joint occurs between limb and bones.
Which ion is essential for muscle contraction? [CBSE AIPMT 1994]
(c) Calcium is an essential element required for the contraction of muscles. Release of calcium ions from sarcoplasmic reticulum trigger the muscle contraction process. In fact, calcium ions and ATP. actin and myosin interact forming actomyosin, which causes the muscles to contract.
The cervical vertebrae in human is [AIPMT 1993]
(a) The number of cervical vertebrae are the same in man and whale which is 7 in number.
Long bones function in [AIPMT 1993]
(b) Long bones strengthen the legs and arms, provide support and also synthesise erythrocytes and leucocytes due to the presence of bone marrow in their cavities.
Number of cervical vertebrae in camel is [AIPMT 1993, 1990]
(c) The vast majority of mammals have seven cervical vertebrae (neck bones), including camel, bats, giraffes, whales, and humans. The few exceptions include the manatee and the two-toed sloth, which each have only six cervical vertebrae, and the threetoed sloth with nine cervical vertebrae.
Characteristics of smooth muscle fibres are [AIPMT 1990]
(a) Characteristics of smooth muscle fibres.
cells range from 5 to \(10 \mu \mathrm{m}\) in diameter and 30 to \(200 \mu \mathrm{m}\) in length
– spindle-shaped
– single, centrally located nucleus
– smooth muscle tissue occurring within almost every organ, forming sheets, bundles, or sheaths around other tissues.
Smooth muscle differs from both skeletal and cardiac muscle tissues in structure and function. Sarcomeres or myofibrils are not present – therefore not striated, ie. smooth.
Extremities of long bones possess which of the following cartilages? [AIPMT 1989]
(d) Hyaline cartilage has a clear, homogeneous, translucent, bluish-green matrix. It often contains a good number of very fine collagen fibres, which are difficult to observe. This cartilage is flexible, elastic, and compressible. It is found in the sternal ribs, extremities of leg bones, tracheal and bronchial rings, laryngeal wall, nasal septum, and superscapula. Elastic cartilage is found in the pinna, epiglottis, Eustachian tubes, and tip of the nose. Calcified cartilage is found in the suprascapula of frog. Fibrous cartilage is found in the intervertebral discs and pubic symphysis.
Intercostal muscles occur in [AIPMT 1988]
(c) Intercostal muscles (external intercostal and internal intercostal) are attached to the ribs which help in the movement of the rib cage during breathing.
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