Q2-MB7/Regulation of muscle contraction and energy sources Flashcards
What is excitation-contraction coupling?
it is the relationship between electrical signals of action potentials AND mechanical changes in the heart muscle cells that causes them to contract
What are the 6 steps of excitation-contraction coupling?
When the AP comes to the axon terminal, ACh is released into the synpased and binds to nicotinic receptors.
The nicotinic receptors will open channels for sodium to flood into the cell and potassium to leak out. (Na+’s driving force to come in is a lot higher than K+’s driving force to go out.)
The Na+ influx causes the cell to depolarize. The depolarization spreads across the sarcolemma and down the T tubule.
Once the depolarization goes down the T-tubule it eventually reaches the dihydropyridine (DHP) receptor. Since DHP receptor is voltage regulated, so when the depolarization reaches the receptor, it changes shape.
When the DHP changes shape, it causes the ryanodine receptor to open. The ryanodine receptor is on the terminal cisternae of the sarcoplasmic reticulum, so when it open, it allows calcium to diffuse out of the SR and diffuse into the cytosol.
In addition to calcium, there is another protein in the SR called calciquesterin which acts as a big buffer for calcium. (can bind Ca++ ions to it)
https://www.youtube.com/watch?v=eLhxnGMBovQ
What is malignant hyperthermia?
rare disorder where, if untreated, anaesthesia can cause a rapid rise in body temp, muscle rigidity, muscle damage, or death.
What causes malignant hyperthermia?
it is caused when certain agents in the anesthesia react with an abnormal ryanodine receptor that causes an excess amt of calcium entering the sarcoplasm (cytoplasm of muscle cell)
What is used to treat malignant hyperthermia?
dantrolene
What is dantrolene?
a muscle relaxant that blocks ryanodine receptor and help with malignant hyperthermia
In the cell, there is a small store of ______ and ___-____ times more creatine phosphate
ATP, 5-10
Chemical equation:
creatine phosphate + _________ -> _____ + _______
creatine phosphate + ADP -> creatine + ATP
What is the enzyme in this reaction?
creatine phosphate + ADP -> creatine + ATP
creatine kinase
_______ can inc. muscle creatine phosphate levels
dietary creatine
Where does ATP come from in energy for contraction?
aerobic oxidative metabolism of glycogen, glucose and fatty acids when there is enough O2
when there is not enough O2, ATP comes from anaerobic glycolysis to lactic acid
the muscle can be regarded as a machine that converts _____ into ______
chemical energy into work
what 2 stages of contraction do skeletal muscles require ATP for?
- ATP required for myosin head to release from actin
- Ca2+ ATPase uses ATP to transport Ca2+ back into sarcoplasmic reticulum
Explain creatine phosphates role in energy for contraction.
Explain oxidative phosphorylation’s role in energy for contraction.
Explain glycolysis’s role in energy for contraction.
high serum levels of creatine kinase are a useful indicator of __________
muscle disease
What is rigor mortis?
stiffening of body muscles after death
How does rigor mortis work?
Since ATP is required for the detachment of myosin crossbridges from actin and no more ATP is produced after death, myosin and actin filaments remain bound to one another, so the muscle stays contracted.
When does rigor mortis begin?
3-4 hours after death
Does rigor mortis ever decrease?
it gradually decreases a few days after as the proteins degrade
Explain isotonic contractions.
equals the weight to be lifted. then the muscle shortens and the tension stays the same.
Explain isometric contractions.
Tension is developed but the overall length of muscle doesnt change
Explain eccentric contractions.
Isotonic contractions are either concentric or eccentric in which tension is developed but the muscle lengthens due to an external force.
