Action potential This is how neurons communicate with each other Fluid outside the axon membrane has mostly positively charged ions (+) At rest, the fluid interior of an axon has negatively charged particles This state is called the resting potential The surface of the axon is selectively permeable

Action Potential: Electrical & Chemical Communication A brief electro/chemical signal that travels down the axon to the terminal buttons.

The Synapse A junction between the terminal buttons of the sending cell and a portion of the membrane of the receiving cell

Threshold and firing the action potential…

The Flow of Transmission Intensity comes from quantity of neurons firing and frequency of firing but the action potential’s strength and speed are constant

Keys in the lock Neurotransmitter – the key fits in nicely Agonist – (excites) mimics the neurotransmitter and stimulates the receptor Antagonist – (inhibits) blocks and does not stimulate the receptor

Four ways neurotransmitters are inactivated 1. Diffusion: the neurotransmitter drifts away, out of the synaptic cleft where it can no longer act on a receptor. 2. Enzymatic degradation (deactivation): a specific enzyme changes the structure of the neurotransmitter so it is not recognized by the receptor. Acetylcholinesterase is the enzyme that breaks acetylcholine into choline and acetate. 3. Glial cells: astrocytes remove neurotransmitters from the synaptic cleft. 4. Reuptake: the whole neurotransmitter molecule is taken back into the axon terminal that released it. This is a common way the action of norepinephrine, dopamine and serotonin is stopped...these neurotransmitters are removed from the synaptic cleft so they cannot bind to receptors.

Done talking! Grab a text book and start mapping neurons and information about them – use text and images and MAKE IT MEANINGFUL TO YOU!

A Closer Look at a Terminal Button Neurotransmitter endogenous* chemical messengers that cross the synaptic gaps between neurons * originates within the organism synapse - hyperlink

Keys in the lock Neurotransmitter – the key fits in nicely Agonist – (excites) mimics the neurotransmitter and stimulates the receptor Antagonist – (inhibits) blocks and does not stimulate the receptor

Neurotransmitters Serotonin Dopamine Acetylcholine Norepinephrine GABA Substance P Endorphins Hyperlink

A Closer Look at Reuptake the process by which the sending neurons collect the excess neurotransmitter hyperlink

Pathways 40 billion neurons each connect to approx. 10 000 other neurons, thus we end up with possibly 400 trillion synapses Neurons cluster into neural networks Neurotransmitter pathways – may use only one or two neurotransmitters and neurotransmitters may affect specific behaviours and emotions Learning occurs as experience strengthens connections

Two key pathways

Dopamine pathways The most important reward pathways in the brain and work as a key detector of a rewarding stimulus Under normal conditions dopamine pathways control an individual's responses to natural rewards, such as food, sex, and social interactions, and is important for motivation Activation of the pathway tells the individual to repeat what it just did to get that reward and tells the memory centers in the brain to pay particular attention to all features of that rewarding experience, so it can be repeated in the future

https://www. ted. com/talks/nicole_avena_how_sugar_affects_the_brain https://www.ted.com/talks/nicole_avena_how_sugar_affects_the_brain?language=en

Plasticity This is the brain’s ability to change, especially during childhood Reorganizing after damage or building new pathways based on new experiences or neurogenesis (new brain cells produced) Not all damage can be remediated – neurons that are severed usually do not regenerate Neurons that fire together, wire together We have synaptic pruning but we also have creation of synapses