Pathophysiology of skeletal muscle Flashcards
Muscle is extremely plastic and adapts to changes in functional demand.
During (1) endurance exercise (2) resistance training muscles respond to:
(1) Total contractile activity
(2) Loading and stretch
When does adaptation of muscle occur?
From embryogenesis into maturity
What kind of structural adaptations can muscle undergo?
What limits this?
How does the muscle grow? By how much can muscle grow in this way?
Size, capillarisation
Total number of muscle fibres fixed at births
Muscle growth occurs by hypertrophy
- synthesis of myofilaments
- addition of sarcomeres
- satellite cell activation
- angiogenesis and vascularisation
- Enlargement by 15-50%
Give an example of an endurance exercise?
What adaptation occur in muscle in response to this type of exercise?
e.g. distance running, swimming, cycling
- increased fibre diameter, blood supply (increase oxidative capacity) and mitochondrial content
- fibres became slower (graded transformation of IIX –> IIA –> I)
Give an example of a non-endurance exercise?
What adaptation occur in muscle in response to this type of exercise?
What is the outcome?
e.g. walking, short distance running, cycling
- conversion of type IIX–> IIA. This means that muscle contracts with greater force and strength
- increase in IIX fibre size due to increase in numbers of sarcomeres and myofilaments –> increase in POWER
Muscles get bigger
What is the impact of using ICE on skeletal muscle?
When would you do this?
- reduce swelling by decreasing perfusion to site (vasoconstriction)
- AFTER an acute injury i.e. sprain and in overuse injury
What is the impact of using HEAT on skeletal muscle?
When would you do this?
- relax and loosen tissues
- increased blood flow
- BEFORE activities that irritate chronic injuries i.e. sprain
ASPIRIN IS USED IN TREATMENT OF MSK INJURIES
Describe it using the following parameters
- MOA
- Effect
- Indication
- Side effects
- NSAID: inhibits COX, decreases synthesis of prostaglandins (part of arachidonic acid pathway)
- Reduces pain and inflammation
- Used for MSK pain in OS and sports injuries + ice
- Side effects: GI- stomach ulcers –> bleeding
State the anabolic effects of testosterone
- Increases protein synthesis
- Decreases catabolism (opposes cortisol and glucocorticoids)
- Decreases fat: increases BMR (basal metabolic rate), increases differentiation into muscle
What are the effects of testosterone in abuse?
- Increase muscle size and strength
- Kidney, liver, heart, mood changes
- MALES: testes atrophy, sterility, baldness
- FEMALES: breast/uterus atrophy, menstrual changes
What is the effect of spaceflight on muscle?
- transition of type I–> IIA/X
- decrease in relative muscle mass- mall muscles atrophy but predominantly weight bearing muscles
What is the effect of bed rest on muscle?
How are these effects avoided/treated?
- transition of type I –> IIA
- weight bearing muscle atrophy due to decreased protein synthesis, myofibrillar breakdown, decrease strength
Resume minor activity early + physiotherapy to prevent contractures
Define a contracture
- process of growth is reversed, sarcomeres removed in series from myofibrils resulting in shortening of muscle
- caused by immobilisation of limb for long periods of time
Briefly describe the nucleic arrangement of skeletal muscle
What does this mean for mitosis?
- Multinucleate (they develop as myoblasts which are mononucleate and later fuse together)
- Nuclei are peripheral
Skeletal muscle enlarged by fibre enlargement and increased vascularisation as mitosis is impossible as they cant divide
Consider muscle regeneration
When does it happen?
How?
- during inflammation and degeneration of damaged muscle tissue
- previous quiescent (resting) myogenic cells (satellite cells) are activated. They proliferate, differentiate and fuse onto existing fibres–> contribute to forming multinucleate myofibers
