Biological Psychology: Neurons, Neurotransmission, and Brain Structure

Biological Psychology

Neurons: The Brain's Communicators

Neurons are specialized nerve cells responsible for communication within the nervous system. They are the fundamental building blocks of the nervous system and transmit information via electrical signals known as action potentials.

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

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

• Axon: "Tails" that transmit information away from the cell body.

• Axon terminals: End of the axon, where neurotransmitters are released to communicate with other neurons.

• Synapse: The junction between neurons where neurotransmitters are released.

Glial cells: Support, nourish, and protect neurons. The term "glial" means glue.

Myelin and Multiple Sclerosis

Myelin is a fatty sheath that insulates axons, speeding up neural transmission. Multiple sclerosis (MS) is a disorder characterized by the loss of myelin, resulting in erratic neural signals and impaired function.

How Does a Neuron Fire?

An electrical impulse called the action potential enables neurons to communicate. The process involves several steps:

1. Resting potential: The neuron is polarized (negative inside), and gates are closed.

2. Action potential: A brief electrical charge travels down the neuron, transmitting neural messages.

3. Repolarization: Potassium ions ($K^+$) flow out, repolarizing the axon.

4. Return to resting potential: The neuron resets.

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 neurotransmitters: Increase the likelihood that the neuron will fire.

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

Neurotransmitters: Functions and Examples

Neurotransmitters are chemical messengers that facilitate communication between neurons. They influence mood, emotions, movement, and cognition.

• Serotonin: Regulates mood, sleep-wake cycles, appetite, and pain perception. Low levels are associated with depression and anxiety.

• Dopamine: Involved in pleasure, reward, voluntary movement, and attention. Deficits are linked to Parkinson's disease; excess is associated with schizophrenia.

• Acetylcholine: Controls movement, arousal, attention, memory, and sleep. Drugs like Aricept boost acetylcholine levels; insecticides limit breakdown.

• Glutamate: The most common excitatory neurotransmitter in the CNS, associated with learning and memory. High levels may contribute to mental disorders.

• GABA (gamma-aminobutyric acid): The most common inhibitory neurotransmitter, dampening neural activity.

Neurotransmission: Release and Reuptake

After neurotransmitters are released into the synaptic cleft, they bind to receptors on the postsynaptic neuron. Excess neurotransmitters are removed by:

• Reuptake: Neurotransmitters are taken back into the presynaptic neuron for recycling.

• Some drugs (e.g., cocaine) block reuptake, prolonging neurotransmitter effects.

The Nervous System: An Overview

The nervous system is divided into several components, each with specialized functions:

• Central nervous system (CNS): Brain and spinal cord; processes information and coordinates activity.

• Peripheral nervous system (PNS): Connects the CNS to limbs and organs.

• Autonomic nervous system: Controls involuntary functions (e.g., heart rate, digestion).

• Somatic nervous system: Controls voluntary movements.

• Sympathetic division: Prepares the body for action (fight or flight).

• Parasympathetic division: Calms the body and conserves energy.

Neural Plasticity

The brain is adaptable and can change throughout life:

• Myelination: Increases speed and efficiency of neural transmission.

• Pruning: Removal of unused synaptic connections to improve efficiency.

• Plasticity decreases with age.

Intergenerational Trauma

Trauma can be passed down through generations, affecting brain structure and function. First observed in children of Holocaust survivors, it is also seen in other populations exposed to severe stress.

• PTSD is associated with changes in the brain.

Major Brain Structures

Hindbrain

The hindbrain is the most primitive part of the brain, controlling basic functions necessary for survival.

• Medulla: Controls vital functions (heartbeat, breathing, swallowing).

• Pons: Sleep and arousal.

• Cerebellum: Motor coordination (e.g., timing of leg movement).

• Reticular Activating System: Key in arousal.

Midbrain & Forebrain

• Midbrain: Controls movement and transmits information for seeing and hearing.

• Forebrain: Manages complex cognitive activities, sensory and associative functions, and voluntary action.

Cerebral Cortex

The cerebral cortex is responsible for higher mental processes and is divided into four lobes:

• Frontal: Planning, decision making.

• Parietal: Sensation (somatosensory).

• Temporal: Auditory processing.

• Occipital: Vision.

Lateralization

Cognitive functions can be specialized to one hemisphere of the brain. The following table summarizes key differences:

Left Hemisphere	Right Hemisphere
Fine-tuned language skills - Speech comprehension, production, reading, writing Actions - Making facial expressions - Motion detection	Coarse language skills - Simple speech - Simple writing - Tone of voice Visuospatial skills - Perceptual grouping - Face perception

Split-Brain Surgery

This procedure involves severing the corpus callosum to reduce the spread of epileptic seizures. It provides insight into lateralization and the independent functioning of the brain's hemispheres.

Additional info: These notes expand on the original content by providing definitions, examples, and context for key terms and processes in biological psychology, including neurotransmission, brain structure, and neural plasticity.