The ______ phase of a muscle twitch corresponds to removal of Ca2+ from the sarcoplasm. 

_________ are proteins that cause exocytosis of neurotransmitter (via synaptic vesicle fusion with the cell plasma membrane). 

CB1 receptors in the CNS are activated by:

Which letter is labeling “depolarization”:

In a fused tetanus, intracellular levels of ____ increase as this ion accumulates in muscle fibers. 

Which type of muscle fiber gets the largest:

Which of these is NOT a factor that typically determines the strength of a graded contraction:

___________ occur in dendrites.

Which term designates the cell plasma membrane in muscle:

The trachea is composed of: