Muscle Physiology Flashcards
Events at the NEUROMUSCULAR JUCTION: Part one - In the SYNANPTIC KNOB of SOMATIC MOTOR NEURON
- AP opens voltage-gated Ca2+ channels
- Ca2+ influx triggers exocytosis of SYNAPTIC VESICLES
- Ach diffuses across SYNAPTIC CLEFT
Events at the NEUROMUSCULAR JUNCTION: Part two - At the motor end plate of SKELETAL MUSCLE FIBER
- Ach binds ligand-gated channels
- Na+ influx depol. MUSCLE FIBER to threshold
- AP generated along SARCOLEMMA
- AchE removes Ach and stops signal
What does the āEā is AchE stand for?
AcetylcholinESTERASE
After travelling along the SARCOLEMMA, where does AP go?
Down the TRANSVERSE TUBULES
What kind of channels does AP open in the TERMINAL CISTERNAE of SR?
Voltage-gated Ca2+ channels
Where is Ca2+ released into?
The CYTOSOL
What does Ca2+ bind to?
TROPONIN
When TROPONIN changes shape, what effect does it have on TROPOMYOSIN?
It moves TROPOMYOSIN to expose the MYOSIN binding sites on ACTIN
How does Ca2+ get back into the SR?
A PUMP
What would happen if Ca2+ pumps stop working?
Ca2+ will build up and the MUSCLE will stay contracted, no relaxation
What is it called when MYOSIN HEADS bind to ACTIN?
The CROSS BRIDGE
What happens during a POWERSTROKE?
MYOSIN pulls ACTIN, shortening the SARCOMERE and causing CONTRACTION
What releases MYOSIN from ACTIN?
ATP
What provides energy for the MYOSIN HEAD to re-cock for another POWERSTROKE?
ATP splitting
How many times does the CROSS BRIDGE CYCLE repeat?
Many times
ISOTONIC, CONCENTRIC CONTRACTION = ?
Muscle shortens e.g. lift object
ISOTONIC, ECCENTRIC CONTRACTION = ?
MUSCLE lengthens e.g put down object
ISOMETRIC CONTRACTION = ?
MUSCLE stays the same length e.g. holding object, maintaining body position