Muscles/Ligaments/Tendons tutorial Wk 6

Question 1

What factors many contribute to high “muscle tone” or higher muscle stiffness in an affected musculotendinous unit of a child with CP?

Answer 1

Increase on collagen content and sarcomere length –> increase passive tension

Question 2

Describe spasticity and contracture using language that is appropriate for a patient of a child with CP

Answer 2

• Spasticity is just when your muscle continue to contract without any control from the person this is due to an upper motor neuron lesion. This is due to a decreased inhibition of stretch reflexes
• Contractures is when your muscles continuously contract without control and this causes your muscles, tendons and ligaments to become hardened and causes deformity and rigidity of your joints
• Spasticity- neural
• Contractures- non-neural
• With CP = loss of function, greater contraction affects bones

Question 3

What is the order of events that can lead to spasticity and contractures of the musculotendinous unit?

Answer 3

Muscles sense stimulus (fake) –> sends signal to troponin for tropomyosin to open the myosin heads –> actin attaches –> actin and myosin cross bridging

Question 4

Which structures transmit forces passively?

Answer 4

• Actin and myosin cross bridging generate force
• Titin (anchors myosin to z line) and connective tissue (endomysium; perimysium; epimysium transmits force passively

Question 5

Where do most injuries occur within the musculotendinous unit?

Answer 5

musculotendinous junction

Question 6

Why is the musculotendinous junction the most prone location to injury?

Answer 6

• Going from a elastic material to a more stiff material
• A lot of force being transmitted

Question 7

What is the pre-cursor of somites?

Answer 7

Mesoderm

Question 8

What does the notocord do?

Answer 8

sends out stimulus to differentiate- neural tube

Question 9

What structures develop from mesoderm?

Answer 9

dermatomes; myotomes; scleratomes –> skeletal muscles, skin, bone and connective tissue In series and bilateral paired- symmetry

Question 10

Describe some of the changes that are likely with active loading (e.g. increased exercise) to: Tendon stiffness

Answer 10

• increases tendon stiffness
• isometric (esp. eccentric) contraction is beneficial
• not endurance, stretching (short term)
• 3-5% strain

Question 11

Describe some of the changes that are likely with active loading (e.g. increased exercise) to: Muscle fibres

Answer 11

• Endurance training- changes from type II to I (due to exercise)
• Have changes due to genetics (predisposed)
• Type II- easily fatiguable
• Type I (slow twitch)- smaller force generated but able to be sustained
• Muscle changes occur faster (wraps up)
• Tendon changes occur faster (after detraining)

Question 12

What is sacropenia?

Answer 12

Loss of mean body mass

Question 13

What are 7 changes in the musculotendinous unit that are likely with ageing?

Answer 13

1. Muscle fibres decrease in number and size; greater change to type II
2. Muscle fibre type transformation (fast –> slow)
3. Myofilaments
   
   • reduce in single fibre max. force reduce in myosin protein content and function
   • Reduce in elasticity
4. Mitochondria
   
   • Reduce in no of type II
   • Loss in enzyme content = decreased ability to create ATP from oxygen = type I fibres more affected (type I and IIa more oxydated)
5. Excitation-contraction coupling
   
   • Disruption or uncoupling
   • Deficits in Ca2+ release
6. Satellite cells reduce in number- less response to injury
7. Adipose tissue infiltration
   
   • Where the muscle was –> increase pennation angle –> increase ability to transfer forces (can help a bit)
   • Fascicle length increase