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 units of the nervous system. They are responsible for transmitting information throughout the body in the form of electrical and chemical signals.

• Building blocks of the nervous system

• Transmit information via electrical signals (action potentials)

Neural Components

• Cell body (soma): Center of the neuron; 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; contains synaptic vesicles filled with neurotransmitters

• Synapse (synaptic cleft): Space between neurons where neurotransmitters travel; site of communication

Mnemonic: Dendrites listen, axons speak!

Glial Cells

• Support neurons

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

• Bodyguards: feed and protect neurons

Myelin Sheath

• Fatty insulation from glial cells surrounding axons

• Multiple sclerosis (MS): Loss of myelin causes erratic signals

Electrical Signaling: Action Potentials

How Does a Neuron Fire?

Neurons communicate by generating and transmitting 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 axon

  • Transmits neural messages to other neurons, muscles, or glands

  • 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, restoring resting potential

Neurotransmission: Chemical Communication

Neurotransmitters and Synaptic Transmission

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

Major Neurotransmitters

• Acetylcholine: Controls movement

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

• Serotonin: Regulates mood, appetite, and sleep

• GABA and norepinephrine: Involved in learning, memory, and arousal

Neurotransmitter Fate: After Release

• Release: Action potential triggers neurotransmitter release into the synaptic cleft

• Binding: Neurotransmitters bind to receptors on the postsynaptic neuron

• Reuptake: Neurotransmitters are reabsorbed by the presynaptic neuron (e.g., SSRIs block serotonin reuptake)

• Enzymatic breakdown: Some neurotransmitters are broken down by enzymes

Neurotransmitter Helpers and Blockers

• Agonists: Mimic or enhance the effect of a neurotransmitter

• Antagonists: Block or impede the normal activity of neurotransmitters

Glutamate and GABA

• Glutamate: Most common excitatory neurotransmitter in the CNS; associated with learning and memory

• GABA: Main inhibitory neurotransmitter; reduces brain activity

Examples:

• Coffee: Increases glutamate, decreases GABA

• Alcohol: Increases GABA, decreases glutamate

Major Neurotransmitters and Their Functions

Neurotransmitter	Main Functions	Associated Disorders
Dopamine	Pleasure, reward, voluntary movement, attention	Parkinson’s (deficit), Schizophrenia (excess)
Serotonin	Mood, sleep, appetite, emotional memory	Depression (deficit)
Acetylcholine	Movement, learning, memory	Alzheimer’s (deficit)
GABA	Inhibition, anxiety reduction	Anxiety disorders (deficit)
Glutamate	Excitation, learning, memory	Schizophrenia (excess)

Brain Structure and Function

Major Regions of the Brain

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

  • Medulla: Vital functions (breathing, heartbeat)

  • Pons: Sleep and arousal

  • Cerebellum: Motor coordination

  • Reticular activating system: Arousal and attention

• Midbrain: Relays information between the hindbrain and forebrain; involved in vision and hearing

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

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

  • Consists of two hemispheres (four lobes each), connected by the corpus callosum

Cerebral Cortex: Lobes and Lateralization

• Frontal lobes: Planning, executive functions, motor control

• Parietal lobes: Sensory information, spatial awareness

• Temporal lobes: Hearing, language, memory

• Occipital lobes: Vision

Hemispheric Specialization

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

Split Brain Surgery

• Procedure that involves severing the corpus callosum to treat severe epilepsy

Key Brain Areas

• Broca’s area: Language production

• Wernicke’s area: Language comprehension

• Prefrontal cortex: Thinking, planning, judgment

• Motor cortex: Voluntary movement

Limbic System

• Emotional center of the brain; also involved in motivation and memory

• Amygdala: Triggers fear or aggression

• Hippocampus: Forms new long-term memories

• Thalamus: Sensory relay station

Brain Plasticity and Injury

Neural Plasticity

• Brain’s ability to change structure and function in response to experience or injury

• Greatest in childhood; decreases in adulthood

• Examples: Recovery after trauma, learning new skills

Brain Injury and Case Studies

• Phineas Gage: Railroad worker with prefrontal cortex damage; personality and judgment changed

• Psychopathy connection: PFC damage linked to impulsivity, lack of empathy, and poor judgment

Brain Mapping and Measurement Techniques

Common Methods

• Phrenology: Discredited; believed skull bumps indicated traits

• CT scan: X-rays to image brain structure

• PET scan: Tracks radioactive substances to show brain activity

• MRI/fMRI: Uses magnetic fields to image brain structure and function

• EEG: Records electrical activity via scalp electrodes

• Deep brain stimulation (DBS): Implants electrodes to treat disorders (e.g., Parkinson’s)

• Transcranial magnetic stimulation (TMS): Uses magnetic fields to alter brain function

Additional Topics

• Toxoplasmosis: Parasitic infection; may affect behavior and risk-taking

• Concussion: Traumatic brain injury affecting function

• Polygraph: Measures physiological responses to detect deception

Summary Table: Brain Lobes and Functions

Lobe	Main Functions
Frontal	Planning, decision-making, motor control
Parietal	Sensory processing, spatial orientation
Temporal	Hearing, language, memory
Occipital	Vision

Additional info: These notes provide a comprehensive overview of neural communication, neurotransmitters, brain structure, and methods for studying the brain, suitable for introductory psychology students.