brain

Analogy

Neuron as a home; potassium as the introverted roommate and sodium as the extroverted party guests.
Neurons are depolarized (excited) when sodium ions enter (party guests arrive).
Repolarization occurs when potassium ions leave (the introvert leaves for quiet).
Hyperpolarization requires a sodium-potassium pump (bouncer) to reset the internal environment of the neuron.

Sodium-potassium pump function: pumps 3 sodium ions out and 2 potassium ions into the neuron.
Importance of myelination: increases signal speed by allowing action potentials to jump between nodes (saltatory conduction).

Presynaptic neuron: neurotransmitters are synthesized and packaged in vesicles.
Action potential triggers the opening of voltage-gated calcium channels which leads to neurotransmitter release into the synaptic cleft.
Chemical messengers are transferred to the postsynaptic neuron by binding to receptors.

Receptors
- Ionotropic: Fast-acting, directly opens ion channels.
- Metabotropic: Slow-response, involves second messenger pathways.
Clearing neurotransmitters from synaptic cleft:
- Degradation: enzymatic breakdown of neurotransmitters (e.g., action of monoamine oxidase).
- Reuptake: presynaptic cell recycling neurotransmitters for future use.

GABA (inhibitory): decreases likelihood of action potentials; helps regulate anxiety.
Glutamate (excitatory): essential for learning and memory consolidation.
Acetylcholine: involved in learning/memory in CNS and muscle contraction in PNS.
Dopamine: links to movement control and reward; significant in addiction pathways.
Serotonin: regulates mood, appetite, and sleep; modulates aggression.
Norepinephrine/Epinephrine: affects arousal and stress response; norepinephrine in CNS, epinephrine in PNS.

Definition: the ability of the brain to change and form new neural connections
- Synaptogenesis: formation of new synapses.
- Neuroplasticity: occurs throughout life and is critical for learning and recovery from trauma.