neuromuscular junction to myocytes Flashcards
What are the 4 classes of second messengers?
- ions
- G proteins
- phosphorylation
- intracellular receptors
What is the second messenger used in muscles?
free calcium
Where does most of the calcium come from in muscle cells?
the sarcoplasmic reticulum (smooth ER in muscle cell)
What is twitching?
when series of AP stimulate contraction but interval between them is long enough for muscle to relax
What is tetany?
continuous maximal contractile force and shortening
What happens to calcium during twitching?
it is pumped back into the SR during relaxation
What happens to the calcium in tetany?
accumulation of free calcium in cytosol
What are the 3 subunits of troponin?
- troponin T
- troponin C
- troponin I
What are the 4 steps of the powerstroke?
- myosin releases actin
- myosin head cleaves ATP
- myosin binds actin
- power stroke
What is an agonist?
drug that can combine with receptor on a cell to produce a physiological reaction
What is an antagonist?
drug that blocks the activity of the agonist or neurotransmitter
What are the 2 types of ACh receptors?
- nicotinic
- muscarinic
What is the second messenger in nicotinic receptors?
ions flowing through an ion channel
What is the second messenger in muscarinic receptors?
G protein
How do nicotinic receptors work?
- allows both Na+ and K+ to flow
- net effect is inward current cuz more Na+ comes in
- makes AP firing more likely
