Muscle physiology 2 - pathology Flashcards
What are the types of muscle contraction?
Isotonic
Isometric
Eccentric
What is isotonic muscle contraction?
Shortening of muscle
- due to constant load but movement
What is isometric muscle contraction?
Muscle remains same length
- constant load, no movement
What is eccentric muscle contraction?
Lengthening of muscle
- force acting against muscle > force acting on muscle
What are type I muscle fibres?
Slow twitch, oxidative fibres
- red in colour due to high myoglobin, very vascular
- very resistant to fatigue
What are type IIa muscle fibres?
Fast twitch, oxidative fibres
- red in colour due to high myoglobin, vascular
- resistant to fatigue
What are type IIb muscle fibres?
Fast twitch, glycolytic fibres
- white in colour due to low myoglobin, low vascularity
- fatigue rapidly
What it the muscle fibre recruitment order?
- Type I - smallest motor neurones (depolarise fastest)
- Type IIa
- Type IIb - largest motor neurones (depolarise slowest)
What two factors determine contraction strength?
No. of motor units recruited
- more => more tension
Frequency of impulses
- more => more tension
What are the reasons for peripheral fatigue?
Contraction failure
Lactic acid build up
ADP + P build up
What is the reasons for central fatigue?
Cerebral cortex not firing appropriate action potentials
- due to tiredness and low motivation
What is muscle cramp?
Painful strong muscular contraction in response to ischaemia or metabolic disturbance
- nerve APs firing at abnormally high rates
What are the aggrevating factors of muscle cramp?
Overexercising
Dehydration
Lactic acid build up
Tight clothing
What is a muscle strain?
Associated with eccentric contractions - more forceful due to elastic recoil of connective tissue elements and elastic filaments in the muscle fibres
- associated with fast twitch muscle fibres
