MSK

Question 1

Axillary nerve

Posterior cord

Answer 1

C5 + C6

Deltoid muscle

Injury: proximal humerus fracture dislocated shoulder

Question 2

Radial nerve

Posterior cord

Answer 2

C5-T1

Extensor to arm, wrist, and fingers
Triceps (extension at elbow)
Sensory to back of hand/forearm

Injury: humeral midshaft fracture, crutches, Saturday night palsy

Question 3

Musculocutaneous nerve

Lateral cord

Answer 3

C5-7

Biceps
Sensation to the lateral forearm

Question 4

Upper trunk lesion (Erbs Palsy)

C5-C6

Answer 4

Caused by excessive angle at neck/shoulder (birth trauma)

Injures axillary nerve, musculocutaneous nerve, suprascapular nerve (arm straight at side and internally rotated)

Waiter’s tip

Question 5

Lower trunk lesion (Klumpke Palsy)

C8-T1

Answer 5

Excessive abduction of arm (Catching tree while falling)

Injures ulnar and median nerves (intrinsic hand muscles)

Clawed hand

Question 6

What supplies sensory to the hypogastric region?

Answer 6

Iliohypogastric nerve (T12-L1)

Commonly injured in abdominal/pelvic surgery

Question 7

What nerve supplies the cremasteric muscle?

Answer 7

Genitofemoral nerve (L1-L2)

Also sensory to scrotum/labia + anterior thigh

Question 8

Obturator nerve

Answer 8

L2-L4

Thigh adductors motor and sensory of medial thigh

Injured during pelvic surgery

Question 9

What is the order of structures in the femoral triangle from lateral –> medial?

Answer 9

Nerve
Artery
Vein
Lymph

Question 10

Femoral nerve

Answer 10

Flexion of thigh + extension of knee
Patellar reflex
Sensation to anterior thigh and medial leg

Question 11

Sciatic nerve branches into what?

Answer 11

Common peroneal (common fibular)
Evert and dorsiflex the foot (foot drop when injured) 
Sensory to dorsum of foot 

Tibial
Plantar flexion and inversion (can’t stand on toes)
Sensory to sole of foot

Question 12

What innervates the external anal sphincter?

Answer 12

Pudendal nerve (S2-S4)

Also supplies perineum, urethral sphincter, and levator ani and is sensory to these areas

Question 13

Marker for a pudendal nerve block

Answer 13

Ischial spine of pelvis

Question 14

What innervates the hamstrings?

Answer 14

Sciatic nerve (L4-S3)

Knee flexion, hip extension, and hip rotation

Question 15

What can cause sciatic neuropathy?

Answer 15

Posterior hip dislocation and prolonged compression

Question 16

Most common nerve roots compressed by IVD rupture?

Answer 16

L5 (lateral leg pain, cannot walk on heels)

S1 (back leg pain, no ankle reflex)

Question 17

Rotator cuff

Answer 17

Supraspinatus - initial abduction (0-15)
Infraspinatus - external rotation
Subscapularis - internal rotation
Teres minor - external rotation

Question 18

Shoulder abductors

Answer 18

0-15: supraspinatus
15-90: deltoid
90-180: trapezius
>180: serratus interior

Question 19

Supracondylar fracture injures what

Answer 19

Median nerve (ulnar deviation and supination) 
Brachial artery

Question 20

Dihydropyridine receptors

Answer 20

Proteins that span the ga between T-tubule and SR

L-type Ca+ channels that open ryanodine receptors to release Ca+ to initiate muscle contraction

Question 21

Cause of malignant hyperthermia

Answer 21

Abnormal ryanodine receptors
Triggered by anesthetic use
Treat with dantrolene