Brain Communication and Regions
Neurobiology of the Brain
Neurons: The Building Blocks of the Nervous System
Definition: Neurons are nerve cells, considered the fundamental building blocks of the nervous system (brain and spinal cord). They specialize in transmitting information through electrochemical signals.
Action Potentials: Neurons communicate using action potentials, which are bursts of electrical activity. For example, sensing something hot triggers neurons to send a danger signal.
Key Features of a Neuron:
Cell Body: The central part of the neuron, responsible for building new cell components.
Dendrites: Tree-branch-like extensions that receive information from other neurons (think of them as 'listening').
Axon: A long tail-like structure that transmits information away from the cell body (think of it as 'speaking'). Information flows from dendrites, down the axon, to the axon terminals.
Axon Terminal: The knob-like end of the axon containing vesicles filled with neurotransmitters (chemical messengers).
Neurotransmitters: Chemical substances like dopamine and serotonin, released into the synapse to communicate with other neurons.
Synapse: The tiny gap between neurons. Neurons do not physically touch; they communicate across this gap where neurotransmitters are released.
Glial Cells and Myelin
Glial Cells (The Bodyguards/Worker Bees): These cells are more numerous than neurons and play multiple crucial roles, including supporting neurons and forming myelin.
Myelin Sheath: A fatty insulation wrapped around the axon, made by glial cells. Its purpose is to help electrical messages travel smoother and faster along the axon.
Damage to Myelin: Conditions like Multiple Sclerosis (MS) involve the immune system attacking myelin, leading to communication problems between the brain and body (e.g., mobility issues) because messages are not transmitted smoothly.
The Action Potential (Neuron Firing)
Definition: The electrical pulse neurons use to send signals to other neurons.
Stages of an Action Potential:
Resting Potential: The neuron is polarized, meaning it has a negative charge inside and a positive charge outside. Gates on the cell membrane are selectively permeable, only opening with electrical stimulation.
Depolarization (Action Potential Fires): When sufficiently stimulated by a nearby neuron (e.g., receiving dopamine), the gates open, allowing positive ions to rush in. The inside of the neuron temporarily becomes positive (depolarized). This electrical signal then travels down the axon.
Repolarization: After the electrical signal passes, the neuron repolarizes, returning to its negative-inside, positive-outside resting state.
Refractory Period: A brief period immediately after an action potential during which the neuron cannot fire again, regardless of stimulation. (Analogy: flushing a toilet – you can't flush it again immediately).
All-or-None Law: Neurons either fire completely (if stimulation reaches a sufficient threshold) or not at all (if stimulation is insufficient). There's no