301. Use the arrangement described below. The first cervical vertebra moves around an articulation with the second cervical vertebra, permitting rotation of the head. This articulation is a:
ⓐ. hinge joint between atlas and axis
ⓑ. saddle joint between atlas and skull
ⓒ. gliding joint between axis and sternum
ⓓ. pivot joint between atlas and axis
Correct Answer: pivot joint between atlas and axis
Explanation: The first cervical vertebra is the atlas, and the second is the axis. Their articulation permits rotational movement of the head, which is the defining movement of a pivot joint. A hinge joint mainly permits movement in one plane, while a saddle joint occurs at the carpal-metacarpal articulation of the thumb. Gliding joints are represented by intercarpal articulations. The skull also articulates with the atlas through the occipital condyles, but the rotational relation described here specifically involves atlas and axis. Position, vertebral identity and movement pattern jointly establish the pivot-joint classification.
302. Assertion: The articulation between atlas and axis is a pivot joint.
Reason: It permits rotational movement around the upper vertebral axis.
ⓐ. Both Assertion and Reason are true, and Reason correctly explains Assertion
ⓑ. Both Assertion and Reason are true, but Reason does not correctly explain Assertion
ⓒ. Assertion is true, but Reason is false
ⓓ. Assertion is false, but Reason is true
Correct Answer: Both Assertion and Reason are true, and Reason correctly explains Assertion
Explanation: The atlas-axis articulation is a standard example of a pivot joint. Its characteristic action is rotation, allowing the head and atlas to turn relative to the axis. The reason states the movement pattern that accounts for the subtype named in the assertion. This differs from the one-plane movement of a hinge joint, the sliding of a gliding joint and the multidirectional range of a ball-and-socket articulation. Both statements are biologically valid, and the reason directly explains the classification. Merely knowing that atlas and axis are cervical vertebrae would not be enough; the rotational relation is the decisive functional evidence. The prediction follows from recognising that the atlas-axis articulation is a pivot joint, while intercarpal articulations are gliding joints.
303. The atlas-axis articulation is experimentally fixed, while the skull-atlas contact and all limb joints remain functional. Which movement is most directly impaired?
ⓐ. sliding movement between adjacent carpal bones
ⓑ. one-plane flexion and extension at the knee
ⓒ. rotation of the head around the atlas-axis pivot joint
ⓓ. multidirectional movement at the shoulder ball-and-socket joint
Correct Answer: rotation of the head around the atlas-axis pivot joint
Explanation: Fixing the atlas-axis joint selectively removes movement at the normal pivot articulation between atlas and axis. The principal consequence is impaired rotation of the head relative to the upper vertebral column. The skull-atlas contact remains intact under the stated condition, and the limb joints are explicitly preserved. Sliding at the carpals, one-plane movement at the knee and multidirectional shoulder movement belong to separate synovial articulations. The experiment localises the functional loss by altering one joint while maintaining the others. Its result links the atlas-axis connection specifically with rotational movement rather than with all movements of the head or limbs. The preserved intercarpal joints would still permit sliding, so the experimentally lost movement is localised to atlas-axis rotation. Fixing the atlas-axis articulation selectively removes its rotational contribution while the preserved skull-atlas and limb joints retain their own movements.
304. Match each synovial-joint subtype with its characteristic example and movement. A Column II entry is used once.
| Column I | Column II |
|---|
| P. Ball-and-socket | 1. Atlas-axis; rotation |
| Q. Hinge | 2. Intercarpal; sliding |
| R. Pivot | 3. Shoulder; multiple directions |
| S. Gliding | 4. Knee; primarily one plane |
ⓐ. P-3, Q-4, R-1, S-2
ⓑ. P-4, Q-3, R-2, S-1
ⓒ. P-1, Q-2, R-4, S-3
ⓓ. P-2, Q-1, R-3, S-4
Correct Answer: P-3, Q-4, R-1, S-2
Explanation: A ball-and-socket joint permits movement in multiple directions, as at the shoulder. A hinge joint mainly permits movement in one plane, represented by the knee. The atlas-axis articulation is a pivot joint specialised for rotation. Intercarpal articulations are gliding joints in which neighbouring surfaces slide relative to one another. The mapping combines subtype, anatomical example and characteristic movement. Each example is synovial, so the presence of a cavity does not distinguish the four rows. Subtype identification requires the more specific mechanical relation permitted by the articulating surfaces. The observed pattern is explained by recognising that ball-and-socket, hinge, pivot, gliding and saddle are subtypes within the broader synovial class. Each mapping is fixed by the combination of articular form, characteristic range and example site rather than by the site name alone.
305. Several small bones of the wrist remain connected by synovial joints. During hand movement, adjacent carpal surfaces slide over one another without behaving like a ball in a socket or rotating around the atlas-axis type of pivot. These are:
ⓐ. hinge joints
ⓑ. gliding joints
ⓒ. saddle joints
ⓓ. cartilaginous joints
Correct Answer: gliding joints
Explanation: Articulations between the carpals are gliding joints. Their characteristic movement is sliding between adjacent articular surfaces. The description excludes the rounded head-and-cavity relation of a ball-and-socket joint and the rotation characteristic of a pivot joint. A hinge joint would primarily permit one-plane movement, while a saddle joint is represented by the carpal-metacarpal articulation of the thumb. The joints are stated to be synovial, so classifying them as cartilaginous would contradict the presence of the synovial organisation. The site and movement pattern together identify the gliding subtype rather than merely indicating that the wrist contains movable joints.
306. Examine the following movement records.
| Site | Observed relation |
|---|
| P. Intercarpal articulation | Adjacent surfaces slide |
| Q. Atlas-axis articulation | Rotation occurs |
| R. Knee articulation | Movement occurs primarily in one plane |
| S. Shoulder articulation | Movement occurs in multiple directions |
Which sequence of subtypes corresponds to P, Q, R and S?
ⓐ. Pivot, gliding, ball-and-socket, hinge
ⓑ. Hinge, saddle, pivot, gliding
ⓒ. Saddle, hinge, gliding, pivot
ⓓ. Gliding, pivot, hinge, ball-and-socket
Correct Answer: Gliding, pivot, hinge, ball-and-socket
Explanation: Sliding between neighbouring carpals identifies P as a gliding joint. Rotation between atlas and axis identifies Q as a pivot joint. Movement mainly in one plane makes the knee a hinge joint, while multidirectional movement at the shoulder identifies a ball-and-socket articulation. The sequence integrates four different movement patterns across four anatomical sites. Since all are synovial, the broad structural class is shared and cannot resolve the classification by itself. The decisive evidence comes from the characteristic motion permitted at each articulation. Correct classification preserves both the movement pattern and the appropriate anatomical example for every site. The key structural point is that ball-and-socket, hinge, pivot, gliding and saddle are subtypes within the broader synovial class. The four records correspond respectively to gliding, pivot, hinge and saddle joints, with the observed motion providing the decisive evidence.
307. Use the arrangement described below. At the base of the thumb, a carpal bone meets the first metacarpal through opposing saddle-shaped surfaces. The joint is classified as:
ⓐ. a saddle joint between the carpal and first metacarpal
ⓑ. a pivot joint between the first metacarpal and proximal phalanx
ⓒ. a hinge joint between two neighbouring carpal bones
ⓓ. a ball-and-socket joint between the carpal and radius
Correct Answer: a saddle joint between the carpal and first metacarpal
Explanation: The carpal-metacarpal articulation of the thumb is the representative saddle joint. Its opposing surfaces are described as saddle-shaped, providing the structural clue required for classification. The joint lies at the base of the thumb where a carpal meets the first metacarpal. A pivot joint is represented by atlas-axis rotation, while hinge joints include the knee and interphalangeal articulations. Ball-and-socket joints occur at the shoulder and hip. The description supplies both the surface relation and anatomical location, preventing confusion with other synovial joints found elsewhere in the hand or wrist. A complete interpretation recognises that the thumb carpal-metacarpal articulation is a saddle joint with reciprocally shaped surfaces.
308. A thumb joint normally has opposing saddle-shaped surfaces. After injury, those surfaces become flattened so that only simple sliding remains possible. Which interpretation is most appropriate?
ⓐ. The joint acquires the rotational pattern of an atlas-axis pivot
ⓑ. The joint becomes a ball-and-socket articulation with multidirectional movement
ⓒ. Its saddle specialisation is lost, and movement becomes mainly gliding
ⓓ. The joint becomes a fibrous articulation permitting no normal movement
Correct Answer: Its saddle specialisation is lost, and movement becomes mainly gliding
Explanation: A saddle joint is identified by opposing saddle-shaped surfaces, with the thumb carpal-metacarpal articulation providing a standard anatomical example. Flattening those surfaces removes the structural feature on which the saddle classification depends. If the only remaining movement is simple sliding, the functional behaviour resembles that of a gliding articulation between carpals. The injury does not create the central rotation of a pivot joint or the head-and-socket relation of a ball-and-socket joint. The bones also remain in contact, so a fibrous suture is not formed. The case links articular-surface form with the characteristic movement and subtype it supports.
309. A patient’s skeletal muscles fatigue rapidly during repeated activity. Clinical findings show an autoimmune defect at the neuromuscular junction, while bone mass and joint structure remain normal. The disorder is:
ⓐ. muscular dystrophy
ⓑ. gout
ⓒ. osteoporosis
ⓓ. myasthenia gravis
Correct Answer: myasthenia gravis
Explanation: Myasthenia gravis is an autoimmune disorder that affects the neuromuscular junction, the communication site between a motor-neuron ending and a skeletal muscle fibre. Impaired transmission at this junction produces abnormal fatigue and weakness of skeletal muscles and may progress to paralysis. The intact bones and joints help localise the problem away from osteoporosis, arthritis or gout. Muscular dystrophy also causes muscle weakness, but its defining biological basis is progressive degeneration of skeletal muscles, usually resulting from a genetic disorder rather than an autoimmune junctional defect. The combination of affected site, immune mechanism and activity-related muscular weakness identifies myasthenia gravis.
310. Consider the following statements about myasthenia gravis.
I. It is an autoimmune disorder.
II. It affects the neuromuscular junction.
III. It may cause fatigue, weakness and paralysis of skeletal muscles.
IV. It is primarily caused by age-related loss of bone mass.
ⓐ. I and IV only
ⓑ. I, II and III only
ⓒ. I, III and IV only
ⓓ. II, III and IV only
Correct Answer: I, II and III only
Explanation: Myasthenia gravis is characterised by an autoimmune disturbance at the neuromuscular junction. Since this junction transmits the motor-neuron signal to skeletal muscle fibres, defective communication produces fatigability and muscular weakness; severe impairment may lead to paralysis. Statement IV describes osteoporosis rather than myasthenia gravis. Osteoporosis is an age-related skeletal disorder involving reduced bone mass and increased fracture risk. The valid statements combine the cause, affected site and major consequence of one neuromuscular disorder. Keeping these three levels together prevents myasthenia gravis from being confused with primary degeneration of muscle tissue or with disorders affecting bones and joints. A focused biological inference recognises that myasthenia gravis is an autoimmune disorder of the neuromuscular junction that produces skeletal-muscle weakness.
311. Normal muscle fibres and their motor neurons are tested in two preparations. Direct electrical stimulation of the muscle produces contraction in both, but stimulation through the motor neuron repeatedly fails in Preparation Q because an autoimmune process disrupts junctional transmission. Which inference is best supported?
ⓐ. Preparation Q models myasthenia gravis
ⓑ. Preparation Q models osteoporosis
ⓒ. Preparation Q models gout
ⓓ. Preparation Q models muscular dystrophy
Correct Answer: Preparation Q models myasthenia gravis
Explanation: Direct stimulation shows that the muscle fibre can still generate an action potential and contract, so its internal contractile machinery remains functional under the test conditions. Failure appears when the signal must pass from the motor neuron across the neuromuscular junction. The additional evidence of an autoimmune process localises the disorder even more specifically. This pattern models myasthenia gravis, in which immune-mediated impairment of junctional transmission leads to fatigue and weakness of skeletal muscles. The experiment does not support a bone-mass disorder, uric-acid crystal deposition or primary progressive degeneration of muscle tissue. Its conclusion should remain limited to the tested pathway: neural-to-muscle communication is defective despite preserved direct muscle responsiveness. Direct stimulation bypasses the junction, so preservation of that response localises the failure to communication between motor neuron and fibre rather than to the contractile machinery.
312. Assertion: Myasthenia gravis can weaken skeletal muscles even when the bones and joints are structurally normal.
Reason: It primarily disrupts signal transmission at the neuromuscular junction.
ⓐ. Both Assertion and Reason are true, and Reason correctly explains Assertion
ⓑ. Both Assertion and Reason are true, but Reason does not correctly explain Assertion
ⓒ. Assertion is true, but Reason is false
ⓓ. Assertion is false, but Reason is true
Correct Answer: Both Assertion and Reason are true, and Reason correctly explains Assertion
Explanation: The assertion is true because skeletal-muscle performance depends on successful communication from motor neurons, not merely on intact bones and joints. Myasthenia gravis affects the neuromuscular junction, reducing the effectiveness with which neural signals activate skeletal muscle fibres. This impaired activation produces fatigue and weakness and can progress to paralysis even when the skeletal framework remains structurally normal. The reason identifies the affected site and directly accounts for the functional deficit described in the assertion. The disorder is classified as neuromuscular rather than as a primary inflammatory joint disease or age-related loss of bone mass. A direct mechanistic reading shows that myasthenia gravis is an autoimmune disorder of the neuromuscular junction that produces skeletal-muscle weakness.
313. A child develops steadily worsening weakness because skeletal muscle tissue undergoes progressive degeneration. Family history suggests an inherited defect, while neuromuscular-junction transmission is not identified as the primary problem. The most appropriate diagnosis is:
ⓐ. hypocalcaemic tetany with repeated muscle spasms
ⓑ. myasthenia gravis with impaired neuromuscular transmission
ⓒ. muscular dystrophy with progressive skeletal-muscle degeneration
ⓓ. chronic arthritis with progressive inflammation of synovial joints
Correct Answer: muscular dystrophy with progressive skeletal-muscle degeneration
Explanation: Muscular dystrophy is a disorder in which skeletal muscles undergo progressive degeneration, and the condition is mainly associated with genetic defects. The gradual worsening and family-history clue support this diagnosis. Myasthenia gravis can also produce weakness, but its defining problem lies at the neuromuscular junction and is autoimmune rather than primarily degenerative and genetic. Tetany produces rapid involuntary spasms due to reduced calcium concentration in body fluids, while arthritis involves inflammation of joints. The decisive evidence is not weakness alone; it is the combination of progressive skeletal-muscle degeneration and a likely inherited basis that identifies muscular dystrophy.
314. Which relation correctly distinguishes muscular dystrophy from myasthenia gravis?
ⓐ. Muscular dystrophy degenerates muscle; myasthenia gravis disrupts neuromuscular transmission
ⓑ. Muscular dystrophy impairs neuromuscular transmission; myasthenia gravis degenerates muscle
ⓒ. Both disorders primarily reduce bone mass, but only myasthenia gravis raises fracture risk
ⓓ. Both disorders primarily inflame joints, but only muscular dystrophy deposits urate crystals
Correct Answer: Muscular dystrophy degenerates muscle; myasthenia gravis disrupts neuromuscular transmission
Explanation: Both disorders can produce weakness, but their primary biological sites and causes differ. Muscular dystrophy is mainly a genetic disorder that produces progressive degeneration of skeletal muscle tissue. Myasthenia gravis is an autoimmune disorder affecting transmission at the neuromuscular junction. The distinction lies between deterioration of the muscle itself and defective neural activation of otherwise responsive muscle fibres. Joint inflammation, reduced bone mass, uric-acid deposition and low body-fluid calcium describe arthritis, osteoporosis, gout and tetany, respectively. Accurate diagnosis requires more than recognising a shared symptom; the affected structure and underlying defect determine the correct classification. A structure-function reading shows that myasthenia gravis is an autoimmune disorder of the neuromuscular junction that produces skeletal-muscle weakness. A condition-dependent reading shows that muscular dystrophy involves progressive degeneration of skeletal muscle and commonly has a genetic basis.
315. Skeletal-muscle samples from an affected person are examined over several years.
| Time | Muscle-tissue condition | Joint inflammation | Bone mass |
|---|
| P | Mild degeneration | Absent | Normal |
| Q | Moderate degeneration | Absent | Normal |
| R | Severe degeneration | Absent | Normal |
Which disorder is most consistent with the trend?
ⓐ. gout involving urate-crystal deposition in joints
ⓑ. osteoporosis involving progressive reduction of bone mass
ⓒ. arthritis involving chronic inflammation of joints
ⓓ. muscular dystrophy with progressive muscle degeneration
Correct Answer: muscular dystrophy with progressive muscle degeneration
Explanation: The decisive trend is progressive worsening of skeletal-muscle degeneration from P through R. Joint inflammation remains absent, and bone mass stays normal, so the observations do not support arthritis, gout or osteoporosis. Muscular dystrophy is defined at this level by progressive degeneration of skeletal muscles and is usually associated with a genetic disorder. The table supplies a time-dependent pattern rather than a single episode of weakness. That progression distinguishes degeneration of muscle tissue from myasthenia gravis, where the primary defect lies in neuromuscular transmission. The evidence supports the tissue-level diagnosis but does not by itself identify a particular genetic subtype, which would exceed the supplied information. A comparison of the linked features shows that muscular dystrophy involves progressive degeneration of skeletal muscle and commonly has a genetic basis. Progressive structural loss within muscle fibres distinguishes dystrophy from a transmission disorder at an otherwise preserved neuromuscular junction.
316. A person develops rapid involuntary spasms of skeletal muscles after the concentration of \(\mathrm{Ca^{2+}}\) in body fluids falls markedly. This condition is:
ⓐ. osteoporosis
ⓑ. tetany
ⓒ. muscular dystrophy
ⓓ. gout
Correct Answer: tetany
Explanation: Tetany is characterised by rapid involuntary muscle spasms associated with reduced \(\mathrm{Ca^{2+}}\) concentration in body fluids. The calcium change in this disorder concerns the extracellular or body-fluid condition described for tetany and should not be confused with the normal release of calcium from the sarcoplasmic reticulum during contraction. Osteoporosis involves reduced bone mass and increased fracture risk, while muscular dystrophy produces progressive muscle degeneration. Gout causes joint inflammation through deposition of uric-acid crystals. The simultaneous presence of low body-fluid calcium and rapid muscular spasms identifies tetany through both its trigger and principal muscular consequence.
317. A blood-calcium manipulation is performed in two otherwise comparable preparations.
| Preparation | Body-fluid \(\mathrm{Ca^{2+}}\) | Observed muscle response |
|---|
| P | Normal | No rapid involuntary spasms |
| Q | Markedly reduced | Rapid involuntary spasms |
The result most strongly supports which conclusion?
ⓐ. Reduced body-fluid \(\mathrm{Ca^{2+}}\) is associated with tetanic spasms
ⓑ. Normal calcium with increased bone mass is the principal cause of tetany
ⓒ. Urate-crystal deposition in joints is the principal cause of tetanic spasms
ⓓ. Low calcium produces progressive muscle degeneration rather than spasms
Correct Answer: Reduced body-fluid \(\mathrm{Ca^{2+}}\) is associated with tetanic spasms
Explanation: The preparations differ in body-fluid calcium concentration, and rapid involuntary spasms occur only when that concentration is markedly reduced. This comparison supports the physiological relation between low body-fluid \(\mathrm{Ca^{2+}}\) and tetany. The experiment does not test bone mass, uric-acid deposition or joint inflammation, so conclusions involving osteoporosis, gout or arthritis would exceed the evidence. The result also should not be interpreted as showing that all muscular contractions require low extracellular calcium. Normal contraction follows regulated excitation and intracellular calcium release, whereas tetany describes an abnormal spasm-producing condition associated with reduced calcium in body fluids. The stated outcome is biologically consistent when tetany involves rapid involuntary muscle spasms associated with low \(\mathrm{Ca^{2+}}\) concentration in body fluids. The relation can be followed by noting that weakness alone does not establish tetany because the defining finding is involuntary spasm linked to reduced body-fluid calcium.
318. Assertion: Tetany should not be diagnosed merely from the presence of weak skeletal muscles.
Reason: Its defining biological pattern is rapid muscle spasms associated with low \(\mathrm{Ca^{2+}}\) in body fluids.
ⓐ. Both Assertion and Reason are true, and Reason correctly explains Assertion
ⓑ. Both Assertion and Reason are true, but Reason does not correctly explain Assertion
ⓒ. Assertion is true, but Reason is false
ⓓ. Assertion is false, but Reason is true
Correct Answer: Both Assertion and Reason are true, and Reason correctly explains Assertion
Explanation: General muscle weakness can occur in several disorders, including myasthenia gravis and muscular dystrophy, so weakness alone is not specific for tetany. Tetany is distinguished by rapid involuntary muscular spasms together with reduced \(\mathrm{Ca^{2+}}\) concentration in body fluids. The reason supplies the combination of trigger and consequence needed to separate tetany from other muscular conditions. Both statements are true, and the reason directly explains why a vague symptom cannot establish the diagnosis. The classification depends on the characteristic pattern rather than on any single muscular complaint shared across multiple disorders. The effect can be localised by noting that tetany involves rapid involuntary muscle spasms associated with low \(\mathrm{Ca^{2+}}\) concentration in body fluids.
319. A patient has painful, swollen joints. Clinical findings identify inflammation of the joint tissues, but no finding about uric-acid crystals or reduced bone mass is supplied. The broad disorder indicated by the available evidence is:
ⓐ. muscular dystrophy
ⓑ. tetany
ⓒ. osteoporosis
ⓓ. arthritis
Correct Answer: arthritis
Explanation: Arthritis is the broad term for inflammation of joints. The findings identify joint inflammation directly, while pain and swelling are consistent with that condition. Gout is a more specific inflammatory joint disorder associated with uric-acid crystal deposition, but the stem supplies no crystal finding that would justify narrowing the diagnosis to gout. A finding that is not reported must not be treated as proof that it is absent. Likewise, the lack of a bone-mass measurement does not establish that bone mass is normal; it simply provides no evidence for a bone-mass diagnosis. The conclusion should therefore follow the positive finding actually supplied: inflamed joint tissue. Arthritis is supported, while a specific cause of that inflammation would require further evidence.
320. Consider the following statements.
I. Arthritis involves inflammation of joints.
II. It is primarily a disorder of the neuromuscular junction.
III. Joint pain and swelling may follow the inflammatory process.
IV. Reduced body-fluid \(\mathrm{Ca^{2+}}\) is its defining cause.
ⓐ. I and II only
ⓑ. I and III only
ⓒ. II, III and IV only
ⓓ. I, II, III and IV
Correct Answer: I and III only
Explanation: Arthritis is a skeletal-system disorder involving inflammation of joints. Inflammation can account for joint pain, swelling and impaired movement, making Statements I and III valid. A neuromuscular-junction defect characterises myasthenia gravis rather than arthritis. Reduced body-fluid calcium is associated with tetany and rapid muscular spasms, not with the general definition of arthritis. The valid set identifies both the affected structure and a plausible functional consequence. It does not assign a single universal cause to every case of joint inflammation, which would be unsupported by the defining concept of arthritis. The biological evidence indicates that arthritis refers to inflammation of joints and may produce pain, swelling and restricted movement. The supplied observations indicate that joint inflammation should be distinguished from a primary neuromuscular transmission defect or progressive muscle degeneration.
