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step 1 MSK FC-RX

MSK -Anatomy&physio- didn't know

What is the source of osteoblasts? Mesenchymal stem cells in the periosteum
Which rotator cuff muscle(s) are responsible for external rotation of the humerus/arm? Infraspinatus muscle and teres minor muscle
If a patient presents with a torn PCL, what structures would be directly affected by this injury? Medial femoral condyle and posterior tibia in PCL injury (LAMP)
A patient is unable to oppose his thumb and cannot flex his wrist and the lateral fingers. Which nerve is affected? Median nerve (C5-T1)
A drug is synthesized to prevent calcium binding to NO synthase. What effect would this have on smooth muscle function? It would prevent relaxation of smooth muscle (calcium required for relaxation as well as contraction on smooth muscle)
A man has a tumor invading his brachial plexus. C8 and T1 are compromised. Which nerve distribution is most affected? The ulnar nerve distribution (C8-T1)
Which structures would be directly affected if the ACL were torn? Lateral femoral condyle and anterior tibia with ACL injury (LAMP)
A patient with a proximal ulnar nerve lesion attempts to make a fist. What type of hand gesture do you expect the patient to make? An "OK" gesture with digits 1–3 flexed (similar to the claw hand of distal median nerve lesions)
What is the function of the Golgi tendon organ, a muscle proprioceptor? It senses tension via the dorsal root ganglion and facilitates inhibition of muscle activation, which reduces tension in the muscle and tendon
A woman has a proximal nerve lesion of the right hand. What maneuver during a physical exam can help differentiate median from ulnar nerve injury? Flexing the fingers; ulnar claw gets prominent, while the median claw disappears
What is the role of troponin C in muscle contraction? It binds intracellular Ca2+, which leads to the conformational change that moves tropomyosin out of the myosin-binding groove on actin
What factors activate muscle proprioceptors? Muscle spindle gets activated by ↑ muscle stretch; Golgi tendon gets activated by ↑ muscle force
How does a Pope's blessing distortion arise? Proximal median nerve lesion causes loss of lateral finger flexion and thumb opposition; distortion arises during attempt to make a fist
What happens when ATP binds to a myosin head that is attached to the actin filament? Release of the myosin head; hydrolysis of ATP to ADP puts myosin in a cocked position for the next contraction cycle; Ca2+ is resequestered
A boy fractures the medial epicondyle of the humerus (funny bone), and a nerve is compressed. What deficits in his wrist will likely result? Radial deviation of the wrist on flexion (seen with proximal lesions such as this; he has injured the ulnar nerve)
Which 4 muscles are primarily involved in external rotation of the hips? Obturator, piriformis, iliopsoas, and gluteus maximus
The cells that dissolve bone are derived from what precursor cells? Osteoclasts are derived from fusion of monocyte and macrophage lineage precursors
To diagnose an ulnar claw distortion, what should you ask the patient with a distal ulnar nerve lesion to do? Extend the fingers (note that attempting finger flexion with proximal median nerve lesions → a similar appearance [Pope's blessing])
During skeletal muscle contraction, what is the result of Ca2+ binding to troponin C? Shifts tropomyosin to expose the myosin-binding site
A patient fractures the medial epicondyle of the humerus. What sensory and motor deficits do you expect on physical exam? Paresthesia of medial 1½ fingers, inability to flex medial fingers/wrist, inability to abduct and adduct the fingers (this is an ulnar nerve injury)
A man who receives an injection to the upper medial gluteal region later demonstrates a Trendelenburg gait. It has what characteristics? Contralateral hip drops when standing on leg ipsilateral to site of injury (the superior gluteal nerve [L4–S1] was likely injured)
What protein can decrease osteoclast activity by binding RANKL, and what is the protein's mechanism of action? Osteoprotegerin, a RANKL decoy receptor, prevents RANK-RANKL interaction by binding RANKL
A man loses sensation over the medial 1½ fingers and hypothenar eminence after a wrist injury. Expected findings on hand motor exam? Weakness in interossei and medial 2 lumbrical muscles, ulnar claw on digit extension (this is an ulnar nerve injury)
In membranous ossification, what is the role of cartilage in the formation of woven bone? Woven bone is formed directly without cartilage (ie, there is no role for cartilage); woven bone is later remodeled to lamellar bone
A patient presents with a herniated disc and posterior hip dislocation. You worry about sciatic nerve impingement. What does physical exam show? Motor deficits in the semitendinosus, semimembranosus, biceps femoris, and adductor magnus muscles
What motor deficits would you expect to find in a patient with damage to the lower trunk of the brachial plexus? Decreased function of the intrinsic muscles of the hand with a claw-hand deformity
How are osteoclasts activated? RANKL (RANK ligand expressed on osteoblasts) stimulates RANK receptors on osteoclasts
What role do osteoclasts and osteoblasts play in endochondral ossification? They replace the cartilaginous model with woven bone and later remodel it into lamellar bone
What presentation is associated with an injury to the genitofemoral nerve (L1–L2)? Decreased sensation in upper medial and anterior thigh beneath the inguinal ligament (the lateral portion of the femoral triangle) and absence of cremasteric reflex
A patient sustained a midshaft humerus fracture damaging the extensor compartment. He has a wrist drop. What sensory deficit is expected? Deficit over the posterior arm/forearm and dorsal hand (diagnosis: radial nerve [C5-T1] dysfunction)
A man with a fibular neck fracture cannot evert or dorsiflex his foot. He has a "steppage gait." What spinal nerve roots are impaired? L4–S2 (common peroneal nerve), causing foot drop (PED = Peroneal Everts and Dorsiflexes; if injured, foot dropPED)
After falling from a tree, a woman has no sensation over her shoulder and cannot abduct her arm. What could her injury be? She likely has a fractured surgical neck of the humerus or an anterior humeral head dislocation, damaging the axillary nerve (C5-C6)
Ryanodine receptors couple with which receptors on the cell membrane? Dihydropyridine receptors
Inability to invert the foot is due to damage to what nerve? Tibial nerve (L4–S3) (TIP = Tibial Inverts and Plantarflexes; if injured, can’t stand on TIPtoes)
A patient sustains a fracture of the medial malleolus. What nerve and artery may be damaged as a result? The tibial nerve and the posterior tibial artery
A man is struck from behind by a thrown javelin; it lands in his popliteal fossa. What major nerve and artery are at risk for damage? The tibial nerve and the popliteal artery
What nerves supply the rotator cuff muscles? Suprascapular nerve supplies supraspinatus and infraspinatus; axillary nerve supplies teres minor; upper and lower subscapular nerves supply subscapularis
What unusual movement typically causes anterior talofibular strains? Overinversion/supination of the foot
During the power stroke, what happens to myosin? Myosin releases ADP and Pi and becomes displaced on the actin filament
What are the actions of the gluteus medius and gluteus minimus muscles? Abduction and internal rotation of the hip
A patient with lung cancer develops atrophy, pain, and edema in his right hand. Where is his tumor most likely invading? The lower trunk of the brachial plexus and the subclavian vessels (usually within the scalene triangle); the patient likely has a right-sided Pancoast tumor
How does estrogen deficiency (eg, due to surgery or menopause) lead to osteoporosis? Excess remodeling cycles and bone resorption occur without the protective effects of estrogen
In patients unable to stand on their tiptoes, which nerve is damaged? Tibial nerve (L4–S3) (TIP = Tibial Inverts and Plantarflexes; if injured, can’t stand on TIPtoes)
A patient has a supracondylar humerus fracture and sensory loss on the dorsal and palmar aspects of the lateral fingers. The damaged nerve arises from which roots? C5-T1 (the median nerve is damaged)
A man's hip dislocates posteriorly. He cannot rise from a seat or climb stairs. What are the spinal roots of the injured nerve? L5–S2 (inferior gluteal nerve), with impairment of the gluteus maximus muscle
What is the function of the muscle spindle, a type of muscle proprioceptor? It senses speed and length of stretch via the dorsal root ganglion and facilitates muscle agonist contraction and antagonist relaxation, which prevents overstretching
What opens the presynaptic voltage-gated Ca2+ channels, inducing the release of acetylcholine into the synaptic space? Action potential
Name the major nerves that innervate the arm Axillary, radial, musculocutaneous, median, ulnar
During skeletal muscle contraction (power stroke), which bands of the sarcomere decrease in length? H band and I band between the Z lines (HIZ shrinkage); ADP is released at end of power stroke
What type of injury to the wrist could lead to acute carpal tunnel syndrome? A dislocation of the lunate bone (median nerve injury)
A man has a palmar laceration. A hand surgeon notes a transected recurrent branch of the median nerve. What exam findings do you expect? Ape hand with preserved sensation (loss of opposition, abduction, and flexion of thumb)
What 3 markers can you use to measure the activity of osteoblasts? Osteocalcin, bone ALP, and type 1 procollagen propeptides
Name the muscles that are innervated by the femoral nerve (L2–L4). Quadriceps, iliacus, pectineus, and sartorius (extensor)
Explain how type I slow-twitch muscle fibers utilize oxidative phosphorylation. They have a relative increase in oxidative phosphorylation, which leads to sustained muscle contractions (think "1 slow red ox")
A woman giving birth receives a pudendal nerve block. What landmark does the anesthesiologist use to locate the site of the block? The ischial spine
How does a genitofemoral nerve injury affect female patients? Sensation is lost in the labia majora and medial thigh (L1-L2)
How does a genitofemoral nerve injury affect male patients? Sensation is lost in the scrotum and medial thigh, and the cremasteric reflex is absent
An experimental drug prevents the human body from breaking down old bone cells. Which enzyme does this drug most likely inhibit? Collagenase, as osteoclasts release H+ and collagenases to dissolve old bone
A man falls down the stairs and lands on the medial heel of his hand while it is outstretched. What nerve might he have injured? Ulnar nerve (C8-T1) from fractured hook of hamate
Which bones are formed by membranous ossification? Bones of the calvarium (skull roof), face, and clavicle vs base of skull=endochondral ossification
A man can no longer adduct his thigh and has a sensory deficit in his medial thigh. What type of intervention may be responsible for this? Pelvic surgery, associated with lesions of the obturator nerve (L2–L4)
What type of bone is formed by healed fractures? Woven bone (as opposed to lamellar bone)
How do molecules such as acetylcholine and bradykinin induce smooth muscle cell relaxation? They bind to endothelial cell receptors, increasing Ca2+; the Ca2+ activates NO synthase, and the NO diffuses in smooth muscle, triggering relaxation
A poison affects the release of certain molecules (breakdown products), such that myosin cannot be detached from the actin filament. What molecules are these? ADP and inorganic phosphate
After presynaptic neuron neurotransmitter release, postsynaptic acetylcholine binding leads to the depolarization of which membrane? The motor end plate of the muscle cell (postsynaptic membrane)
What are muscle proprioceptors? Specialized sensory receptors that transmit information regarding muscle dynamics
Are type I red muscle fibers found in slow- or fast-twitch muscles? They are found in slow-twitch muscles ("1 slow red ox")
A patient presents with a knee injury. You notice that the tibia moves forward relative to the femur at 30°. What is the most likely diagnosis? n ACL injury; the Lachman test was used, which is more sensitive than the anterior drawer sign test
Name the muscles innervated by the deep peroneal nerve that are affected by a period of lateral leg compression Tibialis anterior (sensory deficit occurs in webspace between hallux and 2nd digit)
A weight trainer benches on a daily basis. He is inducing hypertrophy of which type of muscle fiber? Type II muscle fibers, which are white fast-twitch fibers
Why are type I muscle fibers red? They have high concentrations of mitochondria and myoglobin for sustained contraction
During muscle contraction, which of the muscle bands remains the same length? The A band (A band is Always the same length)
A diagnosis of carpal tunnel syndrome is made. Which lumbricals are affected by the nerve that is affected by this syndrome? The lumbricals of the index and middle fingers are affected by the median nerve
What are T-tubules, and what is their relation to the muscle? Extensions of muscle plasma membrane in contact with sarcoplasmic reticulum; this enables coordinated contraction of striated muscles
A patient reports decreased sensation to the anterior and lateral thigh. What are risk factors for this condition Tight clothing, obesity, pelvic procedures, and pregnancy can affect the lateral femoral cutaneous nerve (L2–L3)
A man with back pain has weak left knee extension and left patellar hyporeflexia. Herniation at which level is to blame? Left posterolateral herniation of the L3–L4 intervertebral disc, impinging on the left L4 nerve root
What deficits do you expect on exam in a patient with damage to the musculocutaneous nerve? Difficulty flexing the arm at elbow (by bicep brachii) , variable sensory loss over the lateral aspect of the forearm.
How is parathyroid hormone involved in normal bone physiology? At low, intermittent levels, it exerts anabolic (bone-building) effects by activating osteoblasts directly and osteoclasts indirectly
Generally speaking, for distortions of the hand caused by nerve injuries, which subtype has deficits that are less pronounced? Proximal lesions
What is the function of the most commonly injured rotator cuff muscle? Supraspinatus, the most commonly injured rotator cuff muscle, serves to abduct the arm initially (before the action of the deltoid)
Why are disc herniations more likely to occur posterolaterally as opposed to anteriorly? Because the posterior longitudinal ligament is thin and the anterior longitudinal ligament is thick along the midline of vertebral bodies
What nerve innervates the supraspinatus muscle, and what are the degrees of motion? Suprascapular nerve; 0°–15° of abduction
A patient presents with avascular necrosis and nonunion in a wrist bone. The fracture has retrograde blood supply. What part of the wrist is fractured? The proximal portion of the scaphoid
Created by: ema1437
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