Neurons, Neurotransmission, and Brain Structure: Study Notes for Psychology

Neurons: The Brain’s Communicators

Overview of Neurons

Neurons are specialized nerve cells that serve as the fundamental building blocks of the nervous system. They are responsible for transmitting information throughout the body in the form of electrical and chemical signals.

• Specialization: Neurons are highly specialized for communication with each other.

• Function: They 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.

• Axons: Long "tails" that transmit information away from the cell body.

• Axon terminal: End of the axon where synaptic vesicles filled with neurotransmitters are stored.

• Synapse (synaptic cleft): The space between neurons where neurotransmitters travel to transmit signals.

Example: Dendrites listen, axons speak!

Glial Cells

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

• Glial = glue

• Plentiful in the brain

• Play a vital role in psychological functioning (e.g., make myelin)

• Bodyguards: feed and protect neurons

Myelin Sheath

• Function: Fatty insulation from glial cells surrounding the axon

• Importance: Loss of myelin causes erratic signals (e.g., multiple sclerosis)

Electrical Signaling: Action Potentials

How Does a Neuron Fire?

Neurons communicate via electrical impulses called action potentials.

• Step 1: Resting Potential

  • Neuron is polarized (negative inside, positive outside)

  • Selective permeability allows sodium ions (Na+) to pass through

• Step 2: Action Potential

  • Brief electrical charge that travels down the neuron

  • Transmits neural messages to other neurons, muscles, etc.

  • When stimulated, neuron depolarizes (Na+ rushes in)

  • All-or-none law: neuron either fires or it doesn’t

  • Frequency = intensity

• Step 3: Repolarization

  • Potassium (K+) flows out, repolarizing the neuron

Neurotransmitters and Synaptic Transmission

Release and Action of Neurotransmitters

When an action potential reaches the end of an axon, it triggers the release of neurotransmitters into the synaptic cleft. These chemical messengers bind to receptors on the receiving neuron, transmitting the signal.

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

• Inhibitory neurotransmitters: Decrease the likelihood of firing.

Types of Neurotransmitters

• Acetylcholine: Controls movement, memory

• Dopamine: Involved in reward, motivation, and voluntary movement

• Serotonin: Mood regulation, sleep, appetite

• GABA and Glutamate: GABA is inhibitory, glutamate is excitatory

Neurotransmitter Fate: After Release

• Reuptake: Neurotransmitters are reabsorbed by the presynaptic neuron

• Enzymatic breakdown: Enzymes break down neurotransmitters in the synaptic cleft

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

Agonists and Antagonists

• Agonist: Mimics or enhances the effect of a neurotransmitter

• Antagonist: Blocks or impedes the normal activity of neurotransmitters

Glutamate and GABA

• Most common neurotransmitters in the CNS

• Glutamate: excitatory, learning and memory

• GABA: inhibitory, calming neural activity

• Example: Caffeine increases glutamate, alcohol increases GABA and decreases glutamate

Major Neurotransmitters and Their Functions

Dopamine

• Pleasure and reward, voluntary movement

• Attention

• Parkinson’s = deficit of dopamine

• Schizophrenia’s symptoms = excess dopamine

Serotonin

• Mood regulation, sleep-wake cycles

• Supports cognition and emotional memory

• Influenced by diet, exercise, sunlight, and sleep

Selective Serotonin Reuptake Inhibitors (SSRIs)

• Used to treat depression

• Block reuptake of serotonin

• Examples: Zoloft, Prozac, Lexapro

Brain Structure and Function

Neural Plasticity

Neural plasticity refers to the brain’s ability to change its structure and function in response to experience or injury.

• Greatest in childhood, decreases in adulthood

• Examples: recovery after trauma, learning new skills

Major Regions of the Brain

• Hindbrain: Controls basic functions (breathing, heart rate, sleep)

• Midbrain: Relays information between the hindbrain and forebrain

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

Key Brain Structures

• Cerebral cortex: Higher mental processes (reasoning, self-awareness)

• Corpus callosum: Connects the two hemispheres

• Medulla: Controls vital functions (breathing, heart rate)

• Cerebellum: Motor coordination

• Reticular activating system: Regulates sleep and wakefulness

Lobes of the Cerebral Cortex

• Frontal lobes: Planning, executive functions, motor control

• Parietal lobes: Sensory information, spatial awareness

• Temporal lobes: Hearing, language, memory

• Occipital lobes: Vision

Hemispheric Specialization

The brain’s two hemispheres have specialized functions.

Left Hemisphere	Right Hemisphere
Fine-tuned language skills (speech, reading, writing)	Coarse language skills (simple speech, tone of voice)
Actions (making facial expressions, motion detection)	Visuospatial skills (perceptual grouping, face perception)

Split Brain Surgery

• Procedure that involves severing the corpus callosum

• Used to treat severe epilepsy

Broca’s Area and Wernicke’s Area

• Broca’s area: Language production

• Wernicke’s area: Language comprehension

Phineas Gage: Prefrontal Cortex Damage

• Railroad foreman who survived a traumatic brain injury in 1848

• Damage to prefrontal cortex led to changes in personality and judgment

The Psychopathy Connection

• PFC damage linked to changes in moral judgment, deficits in guilt, empathy, and learning from punishment

Other Key Brain Structures

• Limbic system: Emotion, motivation, memory

• Amygdala: Fear, aggression

• Hippocampus: Memory formation

• Thalamus: Sensory relay

Toxoplasmosis and Concussion

• Toxoplasmosis: Parasitic infection, may affect brain and behavior

• Concussion: Traumatic brain injury affecting brain function

Brain Mapping and Measurement Techniques

The Polygraph

• Measures physiological responses (e.g., heart rate, skin response) to detect deception

Brain Mapping Methods

• Phrenology: Discredited method that linked skull shape to personality

• Neuropsychology: Studies of brain function in people with brain damage

• CT Scan: X-rays to image brain structure

• PET Scan: Measures brain activity using radioactive substances

• MRI/fMRI: Magnetic fields to produce images of brain structure and activity

• EEG: Records electrical activity via electrodes on the scalp

Brain Stimulation Techniques

• Deep Brain Stimulation (DBS): Implanted electrodes modify brain function (e.g., Parkinson’s treatment)

• Transcranial Magnetic Stimulation (TMS): Magnetic fields applied to the skull to enhance or interrupt brain function