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 efficient communication via electrical and chemical signals.

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

• Role: They serve as the building blocks of the nervous system.

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

• Example: Sensory neurons transmit signals from the skin to the brain, allowing perception of touch.

Neural Components

Neurons have distinct structural components that facilitate 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, tail-like structure that transmits information away from the cell body.

• Axon Terminals: Knobs at the end of the axon containing synaptic vesicles filled with neurotransmitters.

• Synapse: The junction between neurons where communication occurs via neurotransmitters.

• Mnemonic: "Dendrites listen, axons speak!"

Glial Cells

Glial cells are non-neuronal cells that provide support and protection for neurons. They are essential for maintaining the health and function of the nervous system.

• 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 provide insulation.

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

Myelin and Multiple Sclerosis

Myelin is a fatty substance produced by glial cells that insulates axons, increasing the speed and efficiency of electrical signal transmission.

• Function: Myelin sheath surrounds axons, allowing rapid signal conduction.

• Clinical Relevance: Multiple sclerosis (MS) is a disease characterized by the loss of myelin, resulting in erratic neural signaling and impaired motor and sensory function.

Neural Communication: The Action Potential

How Does a Neuron Fire?

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

1. Step 1: Resting Potential

   • The neuron is polarized (negative inside, positive outside).

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

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

2. 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: A neuron either fires completely or not at all.

   • Frequency of firing encodes intensity of stimulus.

3. Step 3: Repolarization

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

4. Step 4: Return to Resting Potential

   • Ion gradients are re-established, preparing the neuron for another action potential.

5. Step 5: Refractory Period

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

Electrochemical Communication

Neural communication involves both electrical and chemical processes. The action potential triggers the release of neurotransmitters, which carry the signal across the synapse.

• Electrical: Action potential travels down the axon.

• Chemical: Neurotransmitters are released into the synapse and 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.

Summary Table: Key Neural Components

Component	Function
Neuron	Transmit electrical signals (action potentials)
Dendrite	Receive information from other neurons
Axon	Send information away from cell body
Axon Terminal	Release neurotransmitters into synapse
Glial Cell	Support, nourish, and protect neurons; produce myelin
Myelin Sheath	Insulate axon, speed up signal transmission

Example: Multiple Sclerosis

• Loss of myelin leads to slower, erratic neural signaling.

• Symptoms include muscle weakness, coordination problems, and sensory disturbances.

Additional info:

• Neural communication is foundational for all psychological processes, including sensation, perception, movement, and cognition.

• Disorders affecting neurons or glial cells can have profound effects on behavior and mental health.