CRL Quiz 3 2010

1

With respect to motor unit remodelling during aging, which one of the following statements is NOT CORRECT?


  There is a loss of motorneurons and a decrease in the diameter of motor axons in the ventral roots.

  Some motorneurons cease functioning while others send out axonal sprouts.

  The most susceptible motor units are those for the type IIB/X muscle fibres.

  Fast muscle fibres can be reinnervated by slow nerves.

  The loss of muscle fibres and motor remodelling contribute to the overall hypertrophy with sarcopenia.


The key word here is “hypertrophy” – with sarcopenia we’re referring to muscle “atrophy” not hypertrophy. All other answers (A-D) are true.

2

Regarding the effects of aging on skeletal muscle, which one of the following statements is NOT CORRECT?


  Fast-to-slow motor unit remodelling contributes to the age-related changes in muscle function.

  The slower isometric twitch can be attributed to impairments in the release and reuptake of Ca2+ caused by age-related decreases in sarcolemmal density.

  Sarcopenia describes the age-related loss of muscle mass and associated muscle weakness.

  Muscles are more easily injured and repair less successfully in old compared with young animals.

  Sarcopenia results from a shift in the balance between protein synthesis and protein degradation.


The key word here is “sarcolemmal” – it should actually refer to sarcoplasmic reticulum density not sarcolemmal density. All other answers (A, C-E) are true.

3

In relation to the effects of aging on skeletal muscle, which one of the following statements is NOT CORRECT?


  Sarcopenia can be attenuated by resistance exercise (strength) training.

  Slower and less precise movements contribute to the increased rate of falls and fractures in the elderly.

  Motor unit sprouting can lead to successful reinnervation of denervated muscle fibres.

  Type II muscle fibres are less susceptible to age-related deficits in function.

  Muscle fibre type grouping can occur during aging due to the selective loss of motor units.


In fact type II muscle fibres are the most susceptible to age-related deficits in function, so D is incorrect. All other answers A, B, C and E are true.

4

A 36 year old woman presents to her general practitioner with a 3 week history of painful and stiff hands and wrists. The pain and stiffness are worse in the morning. Which one of the following features on examination would most favour a diagnosis of rheumatoid arthritis?


  Tenderness of the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints.

  Tenderness and swelling of the MCP and PIP joints.

  Reduced range of movement of the wrist joints.

  Tenderness of the wrist joint.

  Tenderness and swelling of the distal interphalangeal (DIP) joints.


The presence of tenderness alone is less predictive of an inflammatory arthritis than the presence of swelling which suggests synovitis. DIP joints are not generally involved in rheumatoid arthritis.

5

Which one of the following statements concerning skeletal muscle damage is NOT CORRECT?


  Lengthening (pliometric or eccentric) contractions are the most likely type of contraction to cause damage.

  Intramuscular calcium elevation following muscle damage may increase the extent of muscle damage.

  Muscle damage does not always decrease the maximum force output of the damaged muscle.

  For a muscle fibre to be fully repaired following damage the sarcolemma must be intact.

  Elevated levels of muscle specific enzymes do not appear in the plasma following every incident of muscle damage.


A is correct: Lengthening - Higher force more likely to damage (big focus of lectures). B is correct: Membrane lesions, Ca influx, activation of proteases and lipases  more damage (again major focus in damage discussion in lectures). C is correct: Muscle rarely (if ever) totally activated voluntarily, hence it may not notice the loss of SOME of its structure. Force output is just not a conclusive measure of muscle damage (again said in lectures). D is NOT CORRECT: (and this point was the subject of a question we dealt with in lectures). Should stand out as incorrect to all. E is correct: Muscle structure can remodel, and after repeated bouts of the same type of exercise, the enzyme loss diminishes and disappears as the structure is able to reduce damage it caused initially. (Again a point stressed in lectures).

6

Which one of the following statements regarding the shoulder joint is correct?


  It is reinforced on all sides by the rotator cuff muscles.

  Movements at the shoulder joint are associated with movements of scapula on the chest wall in the ratio 2:1.

  Dislocation is common and generally occurs in a posterior direction.

  The subacromial bursa communicates directly with the joint cavity.

  The joint is supported in front by the coracoacromial ligament.


The rotator cuff muscles reinforce the shoulder joint anteriorly (subscapularis), superiorly (supraspinatus), and posteriorly (infraspinatus and teres minor) so that dislocation most commonly occurs in an anteroinferior direction. The coracoacromial ligament overlies the humeral head and prevents its superior displacement from the glenoid cavity. The subacromial bursa which lies deep to the coracoacromial arch does not communicate with the shoulder joint cavity.

7

Which one of the following statements regarding the radioulnar joints is correct?


  The distal radioulnar joint is fixed in position at a fibrous joint.

  The interosseous membrane transmits forces from the radius to the ulna.

  The annular ligament receives fibres of the medial collateral ligament of the elbow.

  Biceps pronates at the proximal radioulnar joint.

  The proximal radioulnar joint is located in its own joint cavity.


The proximal and distal RUJ are pivot type of synovial joints that allow movement of radius on or around the ulna. The joint capsule of the proximal RUJ is continuous with that of the elbow joint. It is the radial or lateral collateral ligament that blends with the annular ligament surrounding the head of the radius. And biceps supinates rather than pronates the forearm.

8

Which one of the following statements regarding the knee joint is correct?


  The capsule of the knee joint migrates distally from the joint line.

  The medial meniscus is more mobile than the lateral meniscus.

  The cruciate ligaments are intracapsular and intrasynovial.

  Menisci do not bear weight.

  The deep fibres of the medial collateral ligament blend with the medial meniscus.


The capsule of the knee joint attaches to the margins of the superior articular surface of the tibia. Because of its attachment to the tibial intercondylar area and medial collateral ligament, the medial meniscus is LESS mobile than the lateral meniscus. The menisci are weight-bearing and the cruciate ligaments are intracapsular but EXTRAsynovial.

9

Which one of the following statements regarding the hip joint is correct?


  The iliofemoral ligament reinforces the capsule of the hip joint posteriorly.

  The ligament of the head of the femur is an important stabiliser at the hip.

  In upright stance the line of gravity of the body passes in front of the hip.

  In upright stance the capsule of the hip joint twists to lock the joint in extension.

  The rotator cuff muscles stabilise the hip joint anteriorly.


The iliofemoral ligament reinforces and strengthens anteriorly and superiorly. The ligament of the head of femur is weak and of little importance in strengthening the hip joint. Whilst ligamentous support is strongest anteriorly the rotator cuff muscles are abundant, stronger and mechanically advantaged posteriorly.

10

Which one of the following is NOT part of the mechanism of osteoclastic bone resorption?


  Osteoid production.

  Attachment to the bone surface.

  Ruffled border formation.

  Lysosomal secretion.

  Carbonic anhydrase activity.


osteoid is produced by osteoblasts. All of the other answers are part of the process of osteoclast activity.

11

Which one of the following conditions will increase serum calcium?


  Surgical removal of parathyroid glands.

  Chronic renal failure.

  Mammary tumour metastasis.

  Vitamin D deficiency.

  Calcium malabsorption.


Mammary tumours release PTHrP, which acts in a similar manner to PTH, to increase serum calcium. All of the other answers would be associated with low serum calcium.

12

Which one of the following movements at the shoulder is NOT caused by contraction of Deltoid fibres?


  Flexion.

  Extension.

  Abduction.

  Adduction.


Contracting as a whole, deltoid abducts at the shoulder but the anterior fibres contribute to flexion and the posterior fibres to extension. Adduction at the shoulder joint is produced by pectoralis major and lat dorsi.

13

Which one of the following joints is not flexed by Flexor Digitorum Superficialis?


  Wrist.

  Metacarpophalangeal.

  Proximal interphalangeal.

  Distal interphalangeal.


FDS tendons split and insert either side of the base of the middle phalanges so have no action on the DIP joints.

14

Which one of the following movements would you expect to be weakened or absent in anterior compartment syndrome?


  Dorsiflexion and inversion.

  Dorsiflexion and eversion.

  Plantar flexion and inversion.

  Plantar flexion and eversion.


The anterior compartment contains tibialis anterior (inversion), and extensor hallucis longus and extensor digitorum longus (dorsiflexion and extension of the toes).

15

Which one of the following statements regarding non-steroidal anti-inflammatory drugs (NSAIDs) is correct?


  Aspirin has analgesic but no antipyretic activity.

  NSAIDs can elicit gastrointestinal irritation as they impair the regulation of stomach acid and mucus secretion.

  NSAIDs are unable to inhibit cyclooxygenase 2 (COX-2).

  The COX-2 selective drug rofecoxib has an excellent safety profile.

  Most of the adverse effects of NSAIDs are due to inhibition of COX-2.


A is incorrect: aspirin will reduce fever by reducing prostaglandin production. B is correct: prostaglandins play an important role in regulating stomach acid and mucus production. If this is interfered with (through use of an NSAID) GI irritation and possibly stomach ulceration can occur (especially if NSAIDs taken over prolonged period). C is incorrect: Inhibition of COX-2 by NSAIDs is a major reason for their therapeutic benefit. D is incorrect: Rofecoxib was withdrawn due to adverse cardiovascular activity). E is incorrect: Many of the unwanted actions of NSAIDs relate to inhibition of basal/homeostatic production of prostaglandins, which is largely driven by COX-1.