In 1913 Bohr proposed his quantized shell model of the atom to explain how electrons can have stable orbits around the nucleus.n 1913 Bohr proposed his quantized shell model of the atom to explain how electrons can have stable orbits around the nucleus.
Norepinephrine, also called noradrenaline, is an organic chemical in the catecholamine family that functions in the human brain and body as a hormone and neurotransmitter.n the most basic terms, the function of norepinephrine is to mobilize the brain and body for action. Norepinephrine release is lowest during sleep, rises during wakefulness, and reaches much higher levels during situations of stress or danger, in what has been called the fight-or-flight response.
Norepinephrine is a neurotransmitter that is important for attentiveness, emotions, sleeping, dreaming, and learning. Norepinephrine is also released as a hormone into the blood, where it causes blood vessels to contract and heart rate to increase.n a typical chemical synapse between two neurons, the neuron from which the nerve impulse arrives is called the presynaptic neuron. The neuron to which the neurotransmitters (chemical messengers) bind is called the postsynaptic neuron.