✅Muscle Function Flashcards
What does the process of muscle contraction involve?
- Neural stimulation of sarcolemma
– Causes excitation–contraction coupling - Muscle fibre contraction
– Interaction of thick and thin filaments
• Tension (force) production
What is essential for contraction?
ATP
Where is the enzyme myofibrillar ATPase (mATPase) located?
In the myosin head.
What is ATP also required for?
To pump calcium back into the SR during relaxation.
Describe Slow fibres
• Type I fibres
– Slow-twitch fibres
– Slow-oxidative fibres
– Large amounts of mitochondria
– Myoglobin
Describe Fast fibres
• Type IIb fibres
– Fast-twitch fibres
– Fast-glycolytic fibres
– Larger in diameter
• Type IIa fibres
– Intermediate fibres
– Fast-oxidative fibres
– Hybrid of type I & IIb
What is muscle tone?
The resting tension in a muscle
What are contractions classified based on?
Patterns of tension production
What are the two types of contraction?
- Isotonic contraction
* Isometric contraction
Describe isotonic contraction
• Skeletal muscle changes length
- Resulting in motion
• If muscle tension > load (resistance):
- Muscle shortens (concentric contraction)
• If muscle tension < load (resistance):
- Muscle lengthens (eccentric contraction)
Describe isometric contraction
Skeletal muscle develops tension, but is prevented from changing length
iso- = same, metric = measure
What are inversely related?
Load and speed of contraction
What does the load (resistance) on a muscle affect?
The longer it takes for shortening to begin
The less the muscle will shorten
What are the affects of types of number of motor units recruited?
– More motor units = greater force
– Fast motor units = greater force
What is the affect of initial muscle length on force?
- Optimum overlap produces greatest amount of tension
- Nature of the motor unit neural stimulation
What affect does the frequency of stimulation have?
-simple twitch, summation, and tetanus
What is a single muscle twitch composed of?
Latent, contraction and relaxation periods.
What are the two receptors in muscle?
Muscle Spindle
Golgi Tendon Organ
What does a muscle spindle do?
– Detect dynamic and static changes in muscle length
– Stretch reflex
– Stretch on muscle causes reflex contraction
What does a golgi tendon organ do?
-Monitor tension developed in muscle
– Prevents damage during excessive force generation
– Stimulation results in reflex relaxation of muscle
When can a muscle no longer perform at the required level of activity?
– Depletion of metabolic reserves
– A decline in pH within the muscle fibre – lactic acid
– A sense of weariness due to low blood pH
– Damage to sarcolemma or sarcoplasmic reticulum
– Pathological conditions – premature fatigue – heart problems, blood loss etc
What is anaerobic pathway?
Lactic acid
Describe atrophy
• Results due to lack of activity or loss of neuronal innervation
• Reduction in muscle fibre size, tone and power
• Examples are sedentary life style, bed rest, spinal cord injury
Describe hypertrophy
• Results due to repeated, exhaustive stimulation
• Muscle fibre increases in diameter
• Number of muscle fibre remains the same
• There is an increase in mitochondria, glycolytic enzymes, larger glycogen reserve
