Biomechanics Midterm

Stress 

			   A  Compression
					 
			      B Tension  

				 C Torsion
			
			          D Shear

Strain %

1.  More elastic = D

2.  Most rigid = A

3.  Most resistant to failure (strongest) = B

4.  Least resistant to failure (weakest) = D

5.	On a stress strain curve diagram, the area under the curve is ?
Equal to the energy stored by the bone.

	

	

												        
		A	wk				B	wk			C                wk

Which of the above musculoskeletal lever system has the advantage in

6.  Speed = A

7.  Lifting efficiency = B

8.  Fine motor control - C  (Short lever arm)

9.  Increased POM = A  (muscle attachment is closer to the fulcrum)

10.	Normal bone is strongest in testing
Compression stress
11.  Which muscle, when fatigued plays a role in femoral neck stress      Gluteus Medius
12.	Osteoporotic bone has discriminative appearance on plain radiograph, this appearance is due 
to     Osteoclasts preferential removal of horizontal trabeculae

13-17	Components of Hyaline cartilage has the primary role of
13.	Attracting H2O molecules = proteoglycans
14.	Collagen synthesis = chondrocytes
15.	Resting compression = Water
16.	Collagenase synthesis = chondrocytes
17.	Providing tensile strength = collagen
18.	Which part of a synovial joint has the least nociceptive nerve endings    Hyaline Cartilage
19.	Which of the following has the most proprioceptive nerve endings  Fibrous Capsule
20.	Why is motion necessary for synovial normal function
a.	prevents adhesions
b.	provides nutrition to cells
c.	provides elasticity to hydrodynamic lubrication
d.	helps the repair and maintenance process
e.	removes waste products of catabolism
21.  What is lubricin    A glycoprotein used for _____________ layer friction reduction
22.	Which one of the following ligaments base the largest number of elastin collagen     ligamentum flavum
23.	When a musculotendinous unit is exposed to a rapid tensile load it will usually tear    in the muscle
24.	In Moyes’ experiment w/primates abnormal anterior cruciate ligament immobilized for 8 wks in a cast took 52 wks to return to approximate full strength
25.	Which of the following components of a nerve bundle is likely to collapse under tensile load    the vein
26.	The H2O content of a nucleus pulposus is approximately 88% at birth and drops to 65-72% by age 75 most of this dehydration occurs at the first and second decade (b/w age 10-20)
27.	A muscle is able to produce more force w/ Eccentric contraction (concentric contraction = weakest)
28.	Why is a warm muscle able to produce more force than a cold muscle
a.	increased conduction velocities
b.	increased … activity of muscle metabolism
c.	increased elasticity of collagen
29.  What determines which muscle fibers will be fast twitch or slow twitch nerve innervation
30.	 When a vertebral motor unit is rotated to the left the number of … fibers resisting torsion 
 stress   reduced by ½
31.	Define Biomechanical Creep and give an example
•	Continued displacement when a constant force is maintained.  Creep appears to be due to the gradual re-arrangement of collagen fibers, proteoglycans and water in the ligament or capsule being stressed
•	If a constant force is left applied to a collagenous structure for a prolonged period, further movement is detectable
•	Constant load over time causing deformation (i.e.:  brick layering)
32.	Between the second and seventh decade (20-70 y/o) the height at a normal L3 disc will   increase by 10%
33.	Young children have a higher disc to body ratio which allows more flexibility
34.	Lateral flexion of the lumbar spine to the right disc bulge will be present to the right
35.	Explain three theories of disc herniation of the disc
a.	Bogdeck Theory—a tear in the annulus must be present for a herniation of the annulus to occur
b.	Tumor Theory—tumor present may cause herniation
c.	Repetitive Motion
•	Flexion/rotation while picking something up
•	Friction due to lumbar spine motion causes tears resulting in nucleus protrusion
36.	Example of Biomechanical Stress Relaxation—lock the load in position and the body adapts (braces, casts for a club-foot)
37-40	name 4 bones that heal very slowly when fractured and explain
37.	Scaphoid—poor blood supply
38.	Femur head—poor blood supply and difficult to immobilize
39.	Tibia—poor blood supply and oblique fractures
40.	Clavicle—poor blood supply
41.	Ribs—difficult to immobilize