Biomechanics Final

Osteocytes whose canalculi were broken by a microcrack in bone are thought to initiate the bone remodeling response by

• activation of osteoblasts
• removing the normal inhibition of osteoclastic activity
• activation of the basic multicellular unit
• none of the above

The sensitivity of the muscle spindle to stretch is altered via the

• gamma neurons
• type Ia neurons
• type II neurons
• none of the above

Which of the following nerve fibers are NOT found on a muscle spindle

• Type Ia
• Type II
• Type Ib
• all of the above

The typical joint changes observed by Radin following excessive impact loading are

• cortical bone thinned and articular cartilage thickened
• cancellous bone became soft and compliant
• cartilage becomes thin or non-existent, cancellous bone became brittle and corical bone tickened
• none of the above

A subject is instructed to generate a 40% MVC eccentric contraction, as a result fast twitch motor units will

• not be active since the force is only 40% MVS
• be activated throughout the contraction
• only be activated at the start of the contraction
• none of the above

A stretch-shorten cycle is defined as

• an isometric contraction followed by an immediate eccentric contraction
• a concentric contraction followed by an immediate eccentric contraction
• an eccentric contraction followed by an immediate concentric contraction
• none of the above

In a ramp contraction (slow contraction taking 3-5 sec to reach 100% MVC) when a new motor unit is recruited it

• fires at the same rate as currently active motor units
• fires at a slower rate than currently active motor unit
• fires at a faster rate than currently active motor unit
• NOTA

The sum all the muscle fiber action potentials that pass thru the recording zone of the electrodes

• Electromechanical delay (EMD)
• Electromyography (EMG)
• a stretch relax
• NOTA

Which of the following responses occur when a viscoelastic material is loaded fast?

• no change in stiffness
• it becomes less stiff
• it becomes stiffer
• it creeps less

A muscle spindle is pulled about the level of its currently sensitivity causing Ia neurons to send impulses, which of the following occur and the spinal cord level

• the muscle and its synergist get alpha stimulation
• the antagonists of the stretched muscle get alpha inhibition
• the Ia impulse stimulates gamma to reset the muscle spindle
• NOTA