Muscle Contraction Flashcards
What are the functions of muscle in the body?
- movement
- maintain posture
- breathe, eat and talk
- hold and attach structures
- source of heat
- dynamic metabolic store
What are the percentages of components in the muscle?
75% water
20% protein (40% myosin, 20% actin)
5% inorganic salts
What attaches muscle to bone?
What are muscle fibres grouped into?
Tendons
Fascicles
What are the three types of mysium in muscle fibres?
Epimysium which surrounds the entire muscle fibre.
Endomysium which surrounds individual muscle fibres.
Perimysium which surrounds a group of muscle fibres.
What cells can be found around the outside of muscle fibres?
Satellite cells
Explain how calcium leads to a contraction of a muscle?
Impulse reaches the end of a neurone (synaptic transmission at neuromuscular junction occurs) and then causes the sarcolemma to be depolarised. This stimulates the sarcoplasmic reticulum to release calcium ions and these then bind to tropomyosin and causes a conformational change which exposes the actin binding site. Myosin heads bind to the actin active site and cause a contraction.
What is a tetanum?
A mechanical response to multiple stimuli.
What happens to calcium after it is released from the sarcoplasmic reticulum experimentally?
At 3Hz, there is time for the calcium to be pumped back into the sarcoplasmic reticulum. If there is less of a delay, calcium does not have time to be pumped back to sarcoplasmic reticulum.
What happens if there is a high rate of impulses of calcium in the cytoplasm?
Permits cross-bridge cycling.
Reaches a point where the force no longer can be increased and contraction can no longer occur
What is the difference between type 1 and type 2 muscle fibres?
1 = slow 2 = fast
Slow fibres can reach tetanus at — stimulation frequencies than fast fibres. Therefore, they can reach their maximal force at — rates of stimulation
lower, lower
What do we need slow fibres for in the body?
maintaining posture, eating and breathing
What are the two types of muscle fibre recruitment? Explain each
Spatial recruitment - individual muscle fibres can be activated in isolation
Temporal recruitment - motor unit activity can br modulated by increasing or reducing rate coding
What does a motor unit consist of?
1 motor neuron and muscle fibres that it innervates