Neurotransmitters are formed in a presynaptic neuron and stored in small membrane-bound sacks, called vesicles, inside this neuron. When this neuron is activated, these intracellular vesicles fuse with the cell membrane and release their contents into the synapse, a process called exocytosis.
Modern timekeeping defines a day as the sum of 24 hours â but that is not quite correct. The Earth's rotation slows down over time. So in terms of solar time, most days are a little longer than 24 hours.
Definition of day for Students. 1 : the time between sunrise and sunset : daylight. 2 : the time a planet or moon takes to make one turn on its axis A day on earth lasts 24 hours. 3 : a period of 24 hours beginning at midnight The offer expires in ten days.