Flashcards in Lecture 25: Skeletal Muscle: Structure & Function Deck (15):
Why do we need cardiac muscle?
- The main function is to contract and make sure that the heart is pumping blood
Why do we need smooth muscle?
- For the control of movement of fluids contraction = movement of blood, urine, digested food
Why do we need skeletal muscle?
- To move
- Maintain posture
- Heat generation (numerous + highly active)
Structure of Skeletal Muscle
- Muscle bundle
- Muscle Fibre / Myocyte / Muscle Cell
The skeletal muscle cell membrane is called the....and the cytoplasm is called...
The contractile unit is called the...
The sarcoplasmic reticulum acts as an....
- Internal calcium store
A triad is a...
- T-tubule sandwiched between two sarcoplasmic reticulum
The motor unit consists of ....
- One somatic neuron and muscle fibres innervated by its branched
Excitation occurs at the....an AP reaches end of motor neuron, which causes _____ entry into nerve terminal. Synaptic vesicles release ____, which diffuse into synaptic cleft. ____ stimulates receptors on the adjacent muscle fibre. ____polarisation of muscle sarcolemma, initiating an action potential. ______ coupling occurs. AP travels over _____ and T-Tubules, triggering release of _____ ions from the adjacent _____ _____. Ca2+ ions diffuse in the _______ where a cross-bridge formation occurs.
- Neuromuscular Junction
- Sarcoplasmic Reticulum
What is cross-bridge cycling?
- The myosin head is in an energised state, with ATP bound. In this stage it has a high affinity to bind with the actin
- Calcium interacted with troponin which exposes active sites
- Actin and Myosin interact
- Energised myosin head pulls the actin / POWERSTROKE
- Each part is driven by high energy bonds of ATP
Do the actin and myosin become shorter?
- No, they just slide into each other
What is the powerstroke?
- The flipping of the myosin head
How does uncoupling of the cross-bridge formation occur?
- ATP must bind to the myosin