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 and glial cells are the primary cellular components of the nervous system.

• Neural communication is essential for sensation, movement, cognition, and emotion.

Neurons: The Brain’s Communicators

Definition and Function

Neurons are specialized nerve cells responsible for transmitting information throughout the nervous system.

• Neurons are the building blocks of the nervous system.

• They communicate with each other via electrical signals called action potentials.

• Neurons enable complex behaviors, thoughts, and emotions.

Neural Components

Each neuron consists of several key structures that facilitate 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.

Dendrites listen, axons speak!

Glial Cells: The Brain’s Support System

Definition and Roles

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

• Glial means "glue"; these cells hold the nervous system together.

• They are plentiful in the brain and play a valuable support role.

• Functions include making myelin, feeding neurons, and protecting them from harm.

Myelin and Multiple Sclerosis

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

• Myelin sheath: Fatty layer that insulates axons.

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

Neural Firing: The Action Potential

Steps in Neural Firing

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

1. Resting potential: The neuron is polarized (negative inside, positive outside). The membrane is selectively permeable, preventing sodium ions (Na+) from entering.

2. Action potential: When stimulated, the neuron depolarizes (gates open, Na+ rushes in), generating a brief electrical charge that travels down the axon. All-or-none law: The neuron either fires completely or not at all. Frequency = intensity: The strength of a stimulus is encoded by the frequency of action potentials.

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

4. Return to resting potential: The neuron resets its electrical state.

5. Refractory period: A brief period during which the neuron cannot fire again, regardless of stimulation.

Electrochemical Communication

Synaptic Transmission

Neural communication involves both electrical and chemical processes.

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

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

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

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

Key Terms and Concepts

• Action potential: The electrical impulse that travels down the axon ($V_{m}$ changes rapidly).

• Resting potential: The baseline electrical state of a neuron ($V_{rest} hickapprox -70$ mV).

• Depolarization: The process by which the neuron becomes less negative inside ($Na^+$ influx).

• Repolarization: Restoration of the negative charge ($K^+$ efflux).

• Refractory period: Time during which a neuron cannot fire another action potential.

• Neurotransmitter: Chemical messenger released at the synapse.

• Synapse: The gap between neurons where neurotransmission occurs.

Example: Action Potential Sequence

• At rest, the neuron maintains a negative charge inside ($V_{rest}$).

• Stimulation opens sodium channels, causing depolarization ($Na^+$ influx).

• Potassium channels open, repolarizing the neuron ($K^+$ efflux).

• The neuron returns to resting potential and enters the refractory period.

Additional info:

• Neural communication underlies all psychological processes, including sensation, perception, movement, and cognition.

• Disorders such as multiple sclerosis highlight the importance of myelin and glial cell function.