The fact that the oxygen atom of a water molecule is negatively charged and the hydrogen atom is positively charged, means that hydrogen atoms of one water molecule attract oxygen atoms of its neighbor, etc. Opposites attract This electrostatic attraction is called a hydrogen bond. This bond is important in determining the many properties of…
Covalent bonds involve a complete sharing of electrons. It occurs most often between atoms that have partially filled outer shells. Thus, if the atoms share similar needs, then electrons will be shared. An atom like carbon forms covalent bonds with other atoms. The electrons travel in orbits around the nuclei of the atoms involved. A…
Ionic bonds arise from elements with an almost empty outer shell acting with elements with an almost full outer shell. A complete transfer of electrons takes place. A well known example is table salt, sodium chloride. In order to become stable, sodium gives its one outer shell electron to chlorine which needs only one electron…
Important Atoms & Electrons ? Electrons are important for several reasons: Chemical bonds form when electrons are transferred/shared between atoms. When the outermost energy level of an atom is almost empty, the atom tends to give up electrons. When the outermost energy level of an atom is almost full, the atom tends to grab electrons…
Nitrogen’s atomic mass = (number of protons: 7) + (number of neutrons: 7) = 14. Therefore, a neutral nitrogen atom must have 7 electrons to balance its 7 protons. Electrons are very tiny particles which surround the nucleus of an atom. They all have a negative electrical charge. A neutral atom has an electrical charge…
The situation is quite different for the third circuit, the Behavioral Inhibition System (BIS). It is associated with the hippocampus, the amygdala, and the basal nuclei. It receives inputs from the prefrontal cortex. The BIS is activated when both fight and flight seem impossible and the only remaining behavioral option is to surrender, submit passively….
Aversive stimuli that provoke action responses activate the brain’s punishment (pain) circuit which enables us to cope with unpleasant situations. It includes brain structures, such as the hypothalamus, thalamus, amygdala, hippocampus, and insular cortex. The Peri-Ventricular System (PVS) or punishment circuit, functions by means of acetylcholine, which stimulates the secretion of adrenal cortico-trophic hormone (ACTH)….
In addition to exerting their effects through molecular mechanisms, these drugs intervene at various points in the brain’s central reward circuit (see above diagram). It is through this combination of effects on the reward circuit and on other brain structures that a drug induces the behaviors and specific subjective sensations. Because neural communication is so…
All these regions are connected by the ‘pleasure or reward bundle’. Their activation causes repetitions of a gratifying action. This then strengthens their associated neural pathways. That’s why reward (pleasure) & punishment (pain) circuits supply the needed motivation for our behaviors. These circuits, acting as programs, flip on or off. The main centers of the…
The axons of the VTA neurons project out synthesized dopamine to modulate the activity of the prefrontal cortex, septum, nucleus accumbens, and amygdala. All of them play an important role in what is called the reward circuit. The punishment and the reward circuits were one of the first to evolve. Parts of it use neurotransmitters,…
The amygdala twins have also many connections with the hypothalamus, the septum, the reticular formation of the brainstem, and the hippocampus. Since the hippocampus is involved in storing and retrieving explicit memories, its connections to the amygdalas are the origin of strong emotions triggered by particular memories. The primary and automatic bodily responses involved in…
The amygdala allows us to react so rapidly to a danger, that only afterwards do we realize what frightened us. How? It connects events with emotions, and helps arouse survival feelings such as fear, pity, outrage. All messages from the senses go first to the thalamus. From there to the appropriate sensory cortex (visual cortex,…
