Neuroscience Foundations: Neurons, Brain Structure, and Brain Mapping

Neurons: The Brain’s Communicators

Overview of Neurons

Neurons are specialized nerve cells that serve as the building blocks of the nervous system. They transmit information via electrical signals known as action potentials.

• Neurons: Specialized for communication within the nervous system.

• Transmit information in the form of electrical signals (action potentials).

Neural Components

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

• Dendrites: Branchlike extensions that receive information.

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

• Axon terminal: End of the axon containing synaptic vesicles filled with neurotransmitters.

• Synapse (synaptic cleft): Space between neurons where neurotransmitters travel; meeting place for communication.

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: Loss of myelin causes erratic signals.

Electrical Signaling: Action Potentials

How Does a Neuron Fire?

Neurons communicate via action potentials, which are rapid electrical impulses.

• Step 1: Resting Potential

  • Neuron is polarized (negative inside, positive outside).

  • Sodium-potassium pump creates a gradient.

• Step 2: Action Potential

  • Brief electrical charge 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, restoring resting state.

Neurotransmitters and Synaptic Transmission

Neurotransmitter Release and Effects

• Action potential triggers release of neurotransmitters (NTs) from vesicles into the synaptic cleft.

• NTs bind to receptors on the postsynaptic neuron (lock and key mechanism).

Types of Neurotransmitters

• Excitatory: Increase likelihood neuron will fire.

• Inhibitory: Decrease likelihood neuron will fire.

Major Neurotransmitters

• Dopamine: Pleasure, reward, voluntary movement, attention.

  • Deficit: Parkinson’s disease.

  • Excess: Schizophrenia symptoms.

• Serotonin: Mood regulation, sleep-wake cycles, appetite, emotional memory.

  • Deficit: Depression, anxiety.

• Acetylcholine: Control movement, learning, memory.

• GABA: Inhibitory, dampens neural activity.

• Glutamate: Excitatory, learning and memory.

Neurotransmitter Fate: Reuptake and Drugs

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

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

• SSRIs (Selective Serotonin Reuptake Inhibitors): Block reuptake of serotonin, used to treat depression.

Agonists and Antagonists

• Agonist: Mimic or enhance the effect of a neurotransmitter.

• Antagonist: Block or impede the normal activity of neurotransmitters.

Glutamate and GABA

• Most common NTs in the CNS.

• Glutamate: Excitatory, learning and memory.

• GABA: Inhibitory, calming neural activity.

• Examples:

  • Caffeine: Increases glutamate, decreases GABA.

  • Alcohol: Increases GABA, decreases glutamate.

Brain Structure and Function

Major Regions of the Brain

• Hindbrain: Controls basic functions (breathing, sleeping).

  • Medulla: Vital functions (breathing, heart rate).

  • Pons: Sleep and arousal.

  • Cerebellum: Motor coordination.

  • Reticular activating system: Regulates sleep/wakefulness.

• Midbrain: Relays information between brain areas and eyes/ears.

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

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

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

Cerebral Cortex: Lobes and Lateralization

• Frontal lobes: Planning, executive functions, motor control.

• Broca’s area: Language production.

• Prefrontal cortex: Thinking, planning, judgment.

• Motor cortex: Voluntary movement.

• Parietal lobes: Sensation, spatial awareness.

• Temporal lobes: Hearing, language, memory.

• Occipital lobes: Vision processing.

Left vs. Right Hemisphere

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

Split Brain Surgery

• Procedure that involves severing the corpus callosum to reduce severe epileptic seizures.

Phineas Gage: Prefrontal Cortex Damage

• Railroad foreman injured in 1848; tamping iron passed through his head.

• Damage to prefrontal cortex led to changes in personality and behavior.

The Psychopathy Connection

• Impairment in thoughtful decisions, controlling impulses, regulating emotions.

• PFC damage linked to "pseudopsychopathy".

• Abnormal/reduced activity in PFC in people with psychopathic traits.

Limbic System and Emotional Processing

• Limbic system: Emotional center; also involved in motivation and memory.

• Amygdala: Detects danger, triggers fear/aggression.

• Hippocampus: Forms new long-term memories.

• Thalamus: Sensory relay; sends signals to appropriate brain regions.

Brain Plasticity and Injury

Neural Plasticity

• Brain’s ability to change structure/function in response to experience.

• Pruning: Elimination of unused neural connections.

• Plasticity decreases in adulthood.

Brain Injury and Disorders

• Concussion: Traumatic brain injury affecting function.

• Toxoplasmosis: Infection affecting responses and personality.

Brain Mapping and Measurement Techniques

The Polygraph

• Uses physiological measurements (e.g., skin response, heart rate) to detect deception.

Brain Mapping Methods

• Phrenology: Early method; now discredited.

• Brain damage studies: Observe function loss to infer brain region roles.

• CT Scan: X-rays to visualize brain structures.

• PET Scan: Monitors brain activity via radioactive substances.

• MRI/fMRI: Magnetic fields to produce images; fMRI shows metabolic activity.

• EEG: Records electrical activity via scalp electrodes.

• Deep Brain Stimulation (DBS): Implanted electrodes modify brain function; used for disorders.

• Transcranial Magnetic Stimulation (TMS): Magnetic fields applied to skull to enhance/interfere with function.

Additional Info

• Brain circuits for reward are important for natural rewards (food, music, sex).

• Brain maturation continues into early adulthood; higher-order thinking and voluntary action handled by the cerebral cortex.