Biological Psychology: Neurons, Glial Cells, and Neural Communication

Biological Psychology: Foundations

Neurons: The Brain’s Communicators

Neurons are the fundamental units of the nervous system, responsible for transmitting information throughout the brain and body. Their specialized structure allows for rapid and precise communication.

• Definition: Neurons are nerve cells specialized in communication with each other.

• Function: They transmit information in the form of electrical signals known as action potentials.

• Role: Neurons are the building blocks of the nervous system.

• Example: Sensory neurons carry information from sensory organs to the brain, while motor neurons transmit signals from the brain to muscles.

Neural Components

Neurons have distinct structural components that enable their function in communication.

• Cell Body (Soma): Contains the nucleus and builds new cell components.

• Dendrites: Branchlike extensions that receive information from other neurons.

• Axon: Long, thin 'tail' that transmits information away from the cell body.

• Axon Terminal: Knob at the end of the axon containing synaptic vesicles filled with neurotransmitters.

• Synapse: The space between neurons where neurotransmitters are released and received (the meeting place).

• Mnemonic: "Dendrites listen, axons speak!"

Glial Cells

Glial cells are non-neuronal cells that provide support and protection for neurons. They are essential for healthy brain function.

• Definition: 'Glial' means glue; these cells are plentiful in the brain.

• Functions:

  • Support neuronal function (e.g., produce myelin).

  • Feed and protect neurons.

  • Maintain homeostasis and form myelin sheaths.

• Example: Oligodendrocytes in the central nervous system produce myelin.

Myelin and Multiple Sclerosis

Myelin is a fatty substance produced by glial cells that insulates axons, allowing for faster transmission of electrical signals.

• Function: Myelin increases the speed and efficiency of neural communication.

• Multiple Sclerosis (MS): A disease characterized by the loss of myelin, resulting in erratic neural signaling and impaired function.

• Comparison Table:

Condition	Myelin Sheath	Signal Transmission
Normal	Intact	Efficient
Multiple Sclerosis	Damaged/Lost	Erratic/Impaired

How Does a Neuron Fire? (Action Potential)

Neurons communicate via action potentials, which are rapid changes in electrical charge that travel along the axon.

• Step 1: Resting Potential

  • Neuron is polarized (negative inside, positive outside).

  • Membrane is selectively permeable; sodium ions (Na+) cannot pass through.

  • Equation: $V_{rest} \approx -70\,\text{mV}$

• Step 2: Action Potential

  • Brief electrical charge travels down the axon.

  • When stimulated, gates open and Na+ rushes in, depolarizing the neuron.

  • All-or-None Law: Neuron fires completely or not at all.

  • Frequency: Intensity of stimulus is encoded by the frequency of action potentials.

  • Equation: $V_{peak} \approx +40\,\text{mV}$

• Step 3: Repolarization

  • Potassium ions (K+) flow out, restoring negative charge inside the axon.

• Step 4: Return to Resting Potential

• Step 5: Refractory Period

  • Brief period during which the neuron cannot fire, regardless of stimulation.

Electrochemical Communication

Neurons communicate with each other through a combination of electrical and chemical signals.

• Electrical Signal: Action potential travels down the axon.

• Chemical Signal: Arrival of the action potential at the axon terminal triggers the release of neurotransmitters into the synapse.

• Neurotransmitters: Chemical messengers that bind to receptors on the receiving neuron's dendrites.

• Types of Messages:

  • Excitatory: Increase the likelihood that the receiving neuron will fire.

  • Inhibitory: Decrease the likelihood that the receiving neuron will fire.

• Example: Glutamate is an excitatory neurotransmitter; GABA is inhibitory.

Summary Table: Steps in Neural Firing

Step	Description
Resting Potential	Neuron is polarized; Na+ outside, K+ inside
Action Potential	Na+ rushes in; depolarization
Repolarization	K+ flows out; restores negative charge
Return to Resting	Ion gradients re-established
Refractory Period	Neuron temporarily unable to fire

Additional info: These notes cover the foundational concepts of biological psychology, focusing on the structure and function of neurons, glial cells, and the mechanisms of neural communication. Understanding these principles is essential for further study of brain function, behavior, and psychological disorders.