Biological Basis of Psychology: Neurons, Signals, Synapses, and Methods

Vocabulary practice flashcards covering neuron anatomy, action potential physiology, synaptic transmission, neuropharmacology, and cognitive neuroscience research methods.

Neuroplasticity

The brain's capacity to continuously modify its physical structure and functional organization in response to environmental demands and learning experiences.

Hippocampus

A brain region involved in spatial navigation that physically expands with intensive navigation experience—as shown in London taxi drivers by Maguire et al. (2006)—and reduces in volume following retirement.

Neuron

The primary signaling cell and central decision-maker of the brain that integrates incoming inputs to determine whether to transmit an electrical signal.

Four Roles of the Neuron

The distinct functions divided across a single neuronal cell: dendrites listen, the soma adds up inputs, the axon sends the answer, and the synapse talks to downstream cells.

Dendrites

Branch-like extensions of the neuron that serve as listening devices, receiving excitatory and inhibitory inputs from as many as $10{,}000$ other neurons.

Soma

The cell body of the neuron where incoming excitatory and inhibitory signals are collected and summed to determine if the threshold is crossed.

Axon

A long fiber extending from the soma—reaching lengths of more than $1\,m$—that conducts the action potential toward the synapse.

Synapse

A microscopic junction with a cleft measuring $0.00002\text{ to }0.00004\,mm$ wide between neurons, across which electrical signals are converted into chemical messengers.

Summation

The integration process wherein multiple small electrical inputs add together to reach the threshold necessary to trigger an action potential.

Temporal Summation

The compounding of repeated inputs arriving from the same source in rapid succession over time before previous inputs decay.

Spatial Summation

The pooling of inputs arriving simultaneously from different dendritic locations across physical space.

All-or-None Response

The principle that once the threshold is crossed, a neuron fires an action potential completely and at full amplitude, never partially or halfway.

Action Potential

A rapid electrical impulse produced when voltage-gated $Na^+$ channels open to allow sodium influx, followed by $K^+$ efflux, sweeping down the axon.

Concentration Gradient

A differential in particle density between two compartments that drives passive diffusion from crowded regions to less crowded regions without external energy input.

Sodium-Potassium Pump

An energy-consuming transport mechanism that actively extrudes $Na^+$ and imports $K^+$ against their concentration gradients to restore resting ionic balance.

Myelin

An insulating sheath enclosing axonal segments, interrupted by small gaps, which allows action potentials to leap down the axon and propagate significantly faster.

Lidocaine and Novocaine

Local anaesthetics that block voltage-gated sodium channels, preventing $Na^+$ influx so pain-sensing neurons cannot reach threshold and fire.

Tetrodotoxin

A toxin found in pufferfish that blocks voltage-gated sodium channels throughout the entire body, leading to paralysis of respiratory muscles and potentially lethal outcomes.

Multiple Sclerosis

An autoimmune disorder characterized by immune attack on myelin sheaths, leading to slowed or failed propagation of electrical impulses along axons.

Presynaptic Terminal

The specialized, swollen axonal tip of the sending neuron that stores neurotransmitters in vesicles and releases them into the synaptic gap upon stimulation.

Synaptic Vesicles

Tiny membranous bubbles in the presynaptic terminal that each package approximately $10{,}000$ neurotransmitter molecules to prevent metabolic degradation.

Calcium Channels ($Ca^{2+}$)

Voltage-gated channels in the presynaptic terminal that open when an action potential arrives, allowing $Ca^{2+}$ influx that triggers vesicle fusion and neurotransmitter release.

Ionotropic Receptors

Postsynaptic receptor proteins that function directly as ion channels, opening when bound by matching neurotransmitters to admit positive or negative ions.

Excitation

A positive 'go' input generated when a postsynaptic receptor admits positive ions into the cell, moving the membrane potential closer to the firing threshold.

Inhibition

A negative 'stop' input generated when a postsynaptic receptor admits negative ions into the cell, pushing the membrane potential away from the firing threshold.

Dopamine Receptors

A set of five receptor subtypes ($D_1$ through $D_5$), where $D_1$ and $D_5$ excite cells while $D_2$, $D_3$, and $D_4$ inhibit them, distributed across distinct structures such as $D_1$ in the cortex and $D_{2a}$ in the pituitary gland.

Reuptake Transporter

A protein embedded in the presynaptic membrane that hoovers released neurotransmitter molecules back out of the synaptic cleft to terminate signaling and recycle messengers.

Acetylcholinesterase

A synaptic enzyme that breaks down and inactivates acetylcholine in the gap between nerve and muscle or within neuronal junctions.

Agonist

A drug or agent that increases neurotransmission when physiological communication across the synapse is too low.

Antagonist

A drug or agent that decreases neurotransmission when physiological communication across the synapse is too high.

Direct (Ant)agonist

A substance that acts directly at the receptor site like a false key, either activating the lock or jamming it to prevent endogenous neurotransmitter binding.

Indirect (Ant)agonist

A substance that alters synaptic transmission by affecting other mechanisms—such as release, reuptake, or degradation—without binding directly to the receptor lock.

Selective Serotonin Reuptake Inhibitors (SSRIs)

Antidepressant medications such as fluoxetine (Prozac) that act as indirect agonists by blocking the serotonin reuptake transporter, leaving serotonin in the synapse longer.

Curare

A arrow poison that acts as a direct antagonist by blocking acetylcholine receptors at neuromuscular junctions, preventing muscle contraction and causing paralysis.

Sarin and Donepezil

Compounds that share the mechanism of inhibiting acetylcholinesterase, where sarin acts as a lethal chemical weapon by causing uncontrolled firing, and donepezil provides gentle therapeutic enhancement of acetylcholine for Alzheimer's disease.

Transcranial Magnetic Stimulation (TMS)

A neurostimulation technique that delivers magnetic pulses over the skull to temporarily perturb or change neural activity in targeted cortical areas.

Functional Magnetic Resonance Imaging (fMRI)

A non-invasive neuroimaging technique that detects regional blood flow changes, offering high spatial resolution to pinpoint where cognitive processing occurs, but low temporal resolution.

Electroencephalography (EEG)

A recording method that detects electrical brain activity using scalp electrodes, providing precise temporal resolution to track the timecourse of thought ('when') but poor spatial localization ('where').

P300 Wave

A positive event-related potential component peaking roughly $300\,ms$ after stimulus onset in EEG recordings during an oddball task, indexing target stimulus discrimination.

Brain Networks

Coordinated, large-scale systems of specialized brain areas—including the default mode network (DMN), central executive network (CEN), and dorsal attention network (DAN)—that interact to support complex behaviour.