Answer: Transmitter is released in discrete, all-or-nothing packages (quanta = synaptic vesicles) each containing ~5,000 molecules.
- A Transmitter release scales smoothly and continuously in direct proportion to action potential firing frequency according to conventional understanding
- B Transmitter is released in discrete, all-or-nothing packages (quanta = synaptic vesicles) each containing ~5,000 molecules
- C The total amount of transmitter released varies continuously along an unbroken smooth gradient curve in routine practice
- D Exactly one single transmitter molecule is released from the presynaptic terminal at any given time overall in most cases
Correct answer: B. Transmitter is released in discrete, all-or-nothing packages (quanta = synaptic vesicles) each containing ~5,000 molecules
Explanation: Quantal release (Fatt and Katz): neurotransmitter is released in discrete, fixed packets (quanta). Each quantum = one synaptic vesicle (~5,000 molecules). mEPPs (miniature end-plate potentials) represent single quanta.
Structure of a neuron. Image: LadyofHats (Mariana Ruiz), Public Domain, via Wikimedia Commons.
Concept context
Brain, spinal cord, neurons, reflex arcs, and sense organs.