Biological Psychology: Neurons, Glial Cells, and Neural Communication

Biological Psychology: Foundations

Introduction to Biological Psychology

Biological psychology explores the relationship between the brain, nervous system, and behavior. It focuses on how neural structures and processes underlie psychological functions.

Neurons: The Brain’s Communicators

Definition and Function

• Neurons are specialized nerve cells responsible for communication within the nervous system.

• They are the building blocks of the nervous system.

• Neurons transmit information via electrical signals known as action potentials.

Neural Components

• Cell body (soma): Contains the nucleus and builds new cell components.

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

• Axon: Long, thin fiber 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 junction between neurons where communication occurs.

Dendrites listen, axons speak!

Glial Cells: The Brain’s Support System

Definition and Roles

• Glial cells (from "glue") are plentiful in the brain and play a vital support role.

• They are involved in psychological functioning, such as producing myelin.

• Glial cells act as bodyguards, feeding and protecting neurons.

Myelin and Multiple Sclerosis

• Myelin sheath: Fatty insulation produced by glial cells that surrounds axons, increasing the speed and efficiency of neural transmission.

• Multiple sclerosis (MS): A disease characterized by the loss of myelin, resulting in erratic neural signals.

How Does a Neuron Fire?

Action Potential: The Neural Impulse

• An action potential is an electrical impulse that travels down the axon, enabling neural communication.

Step 1: Resting Potential

• The neuron is polarized: negative inside, positive outside.

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

Step 2: Action Potential

• A brief electrical charge travels down the axon.

• When stimulated, the neuron becomes depolarized (gates open, Na+ rushes in).

• All-or-none law: The neuron either fires completely or not at all.

• Frequency of firing encodes intensity of the signal.

Step 3: Repolarization

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

Step 4: Return to Resting Potential

• The neuron returns to its original polarized state.

Step 5: Refractory Period

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

Electrochemical Communication

• When an electrical signal reaches the end of an axon, it triggers the release of neurotransmitters into the synapse.

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

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

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

Summary Table: Neural Components

Component	Function
Cell body (soma)	Contains nucleus, builds cell components
Dendrites	Receive information
Axon	Transmits information
Axon terminal	Releases neurotransmitters
Synapse	Site of communication between neurons
Glial cells	Support, nourish, protect neurons; produce myelin

Key Equations

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

• Action potential threshold: $V_{threshold} \approx -55\,\text{mV}$

Example: Multiple Sclerosis

In multiple sclerosis, the immune system attacks the myelin sheath, leading to disrupted neural communication and symptoms such as muscle weakness and coordination problems.

Additional info:

• Neural communication is fundamental to all psychological processes, including sensation, perception, movement, and cognition.