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, specialized for communication. They transmit information via electrical signals known as action potentials.

• Definition: Neurons are nerve cells that communicate with each other to process and transmit information.

• Role: Serve as the building blocks of the nervous system.

• Action Potentials: Electrical impulses that travel along the neuron to convey information.

• Example: Sensory neurons transmit signals from the skin to the brain when you touch a hot surface.

Neural Components

Neurons have specialized structures that facilitate their function.

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

• Dendrites: Branch-like extensions that receive information from other neurons.

• Axon: Long 'tail' 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 gap between neurons where neurotransmission occurs.

• Mnemonic: "Dendrites listen, axons speak!"

Glial Cells

Glial cells are non-neuronal cells that provide support and protection for neurons.

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

• Functions: Support, nourish, and protect neurons; involved in psychological functioning (e.g., myelin production).

• Bodyguards: Feed and protect neurons.

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

Myelin and Multiple Sclerosis

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

• Function: Myelin sheath enables rapid signal conduction.

• Multiple Sclerosis (MS): Loss of myelin leads to erratic neural signaling and impaired function.

• Example: MS patients may experience muscle weakness and coordination problems due to disrupted neural communication.

How Does a Neuron Fire?

The process of neural firing involves several steps, each crucial for proper signal transmission.

• Step 1: Resting Potential

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

  • Membrane is selectively permeable, preventing sodium ions (Na+) from entering.

  • $V_{rest} \approx -70\,\text{mV}$

• Step 2: Action Potential

  • Brief electrical charge travels down the axon.

  • Neuron depolarizes (gates open, Na+ rushes in).

  • All-or-none law: Neuron fires completely or not at all.

  • Frequency of firing encodes intensity of stimulus.

  • $V_{action} \rightarrow +40\,\text{mV}$

• Step 3: Repolarization

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

• Step 4: Return to Resting Potential

  • Neuron resets to its original polarized state.

• Step 5: Refractory Period

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

Electrochemical Communication

Neurons communicate through a combination of electrical and chemical processes.

• Electrical Signal: Action potential travels down the axon.

• Chemical Signal: Neurotransmitters are released into the synapse.

• Neurotransmitters: Bind to receptors on the receiving neuron's dendrites, transmitting the signal.

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

• Inhibitory Messages: Decrease the likelihood of firing.

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

Summary Table: Neural Components

Component	Function
Cell Body (Soma)	Contains nucleus, builds neural components
Dendrites	Receive information
Axon	Transmits information
Axon Terminals	Release neurotransmitters
Synapse	Site of neurotransmission
Glial Cells	Support, nourish, protect neurons
Myelin Sheath	Insulates axon, speeds transmission

Key Equations

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

• Action Potential: $V_{action} \rightarrow +40\,\text{mV}$

Example Application

• In multiple sclerosis, the loss of myelin disrupts the transmission of action potentials, leading to symptoms such as muscle weakness and impaired coordination.