Skeletal Muscle (2) Flashcards
What are the different arrangements of skeletal muscle?
Give examples.
- Circular: orbicularis oris
- Convergent: Pectoralis major
- Parallel: Sartorius
- Unipennate: Exterior digitorum longus
- Multipennate: Deltoids
- Fusiform: Biceps brachii
- Bipennate: Rectus femoris
What are the roles of skeletal muscle?
- Movement
- Stability of joints
- Posture
- Heat generation
What is fasciculation?
- Muscle twitch
Explain what is meant by 1st, 2nd and 3rd class levers.
- ALL: Force, load and fulcrum(pivot)
- 1st: Force and load on opposite ends acting in different directions
- 2nd: Force and load on the LHS upwards
- 3rd: Force and load on RHS upwards
Give examples of 1st, 2nd and 3rd class levers
- 1st: Skull/spinal cord
- 2nd: Leg to foot
- 3rd: Biceps
What are the different types of muscle groups and their roles?
- Agonist: prime movers
- Antagonist: opposes prime movers
- Synergists: assist prime movers (neutralises extra movement)
- Fixators: stabilises action of prime movers (non-moving joints)
What are the different types of muscle contraction?
- Isotonic contraction: constant tension variable muscle length
- Isometric: constant length, variable tension (hand grip)
What are the different types of isotonic contraction?
- Concentric: muscle shortens (lifting load with arm)
- Eccentric: muscle exerts a force whilst extended (downhill)
can cause delayed-onset muscle soreness
What are type I, type IIa and type IIb muscle fibres?
- Type I: slow oxidative
- Type IIa: fast oxidative
- Type IIb: fast glycolytic
Compare type I and type IIa muscle fibres.
- Aerobic
- High myoglobin levels
- Red colour
- Many mitochondria
- Rich capillary supply - (type IIa /pink)
- Fatigue resistant - (type IIa /moderate)
- Endurance activities & posture -(type IIa /walking/sprinting)
How does type IIb differ to type IIa?
- Anaerobic glycolysis
- Low myoglobin levels
- White colour
- Few mitochondria
- Poorer capillary supply
- Rapidly fatigues
- Short, intense movement.
What is proprioception?
- Feedback control of movement.
- Muscles tell CNS how much force is being exerted.
What does a motor unit consist of?
- Motor neurone and muscle fibres it innervates.
What is neuro-musculo communication?
- ‘cross-talk’
- signalling molecules communicate between nerves and muscles
- atrophy of muscle/nerve leads to atrophy of corresponding neurone/muscle.
What is muscle tone?
- Baseline tone in muscles at rest due to: motor-neurone activity/muscle elasticity
How is muscle tone controlled?
- Motor control centres in brain
- Afferent fibre signals, originating in muscle.
What is hypotonia?
- Cerebral/spinal neural shock
- Lesions of cerebellum
- Lesions of sensory afferents from muscle spindles
- Primary degeneration of muscle (myopathies)
What is spatial summation?
- More motor neurones activated
- So more muscles recruited to develop more force
- Reflex pathways have a role
What is temporal summation?
- Increased frequency of action potentials to muscle fibres
- If frequent enough then muscles are constantly contracted - tetanus
What does EMG stand for and what does it show?
- Electromyograph
- Muscle activity
How does relaxation of muscles occur?
- Ca pumped back into SR via Ca pumps
- Some Ca can bind to calmodulin (calcium binding messenger protein)
How do muscle fatigue?
- Depletion of muscle glycogen stores
- Occurs within one minute of blood supply being disrupted
- Intermittent claudication: pain during exercise that is relived once rested.
How does muscle contracture occur?
- State of continuous contraction
- Occurs when ATP’s depleted - myosin cross bridges can’t detach = rigor mortis
