Electrical Signals in Neurons and Synaptic Transmission

Vocabulary flashcards summarizing key terms and definitions from BIO 105 lecture notes on neuronal electrical signaling, synaptic transmission, neurotransmitters, memory mechanisms, and related disorders.

Action Potential (Nerve Impulse)

Electrochemical signal that travels along a neuron’s membrane, transmitting information in an all-or-none, self-propagating wave.

Membrane Potential

Voltage difference across a cell membrane caused by unequal ion distribution; measured in millivolts (mV).

Resting Membrane Potential (RMP)

Baseline electrical charge of a resting neuron (≈ –70 mV); the membrane is polarized with more negative charge inside.

Polarized Phase

State in which the neuron maintains its resting membrane potential prior to stimulation.

Depolarizing Phase

Action-potential phase in which Na⁺ rushes into the cell, making the inside less negative.

Repolarizing Phase

Phase where K⁺ exits and the Na⁺/K⁺ pump restores negative internal charge after depolarization.

Threshold Potential

Critical membrane voltage (≈ –55 mV) that must be reached to trigger an action potential.

Gated Channels

Membrane proteins that open or close to ions, helping establish and restore resting potential.

Sodium–Potassium Pump

Active transporter that moves 3 Na⁺ out and 2 K⁺ in, re-establishing ionic balance after an impulse.

Absolute Refractory Period

Time during which a second action potential cannot be generated, regardless of stimulus strength.

Relative Refractory Period

Interval when a stronger-than-normal stimulus can initiate another action potential.

Continuous Conduction

Slow propagation of an action potential along unmyelinated axons.

Saltatory Conduction

Fast "leaping" of an action potential from node to node along myelinated axons.

Myelination (Effect on Speed)

Greater myelin thickness increases conduction velocity of nerve impulses.

Axon Diameter (Effect on Speed)

Larger axon diameter results in faster propagation of action potentials.

Synapse

Junction where a neuron communicates with another cell via chemical or electrical signals.

Presynaptic Neuron

Neuron that sends the signal toward a synapse.

Postsynaptic Neuron

Neuron that receives the signal at a synapse.

Synaptic Bulb (Knob)

Swollen axon ending containing neurotransmitter-filled vesicles.

Synaptic Cleft

Tiny extracellular gap between presynaptic bulb and postsynaptic membrane.

Postsynaptic Receptors

Membrane proteins that bind neurotransmitters and initiate postsynaptic responses.

Calcium Channels in Synaptic Bulb

Voltage-gated channels that allow Ca²⁺ influx, triggering neurotransmitter exocytosis.

Neurotransmitter

Chemical messenger released by neurons to communicate across synapses.

Excitatory Postsynaptic Potential (EPSP)

Depolarization of the postsynaptic membrane that increases likelihood of an action potential.

Inhibitory Postsynaptic Potential (IPSP)

Hyperpolarization of the postsynaptic membrane that decreases likelihood of firing.

Neurotransmitter Diffusion

Removal method where neurotransmitter drifts away into interstitial fluid.

Enzymatic Degradation

Breakdown of neurotransmitter by enzymes (e.g., acetylcholinesterase).

Reuptake (Uptake by Presynaptic Neuron)

Process in which neurotransmitter is transported back into the presynaptic terminal for reuse.

Acetylcholine (ACh)

Neurotransmitter excitatory at skeletal NMJ and inhibitory at cardiac muscle.

Serotonin

Amine neurotransmitter involved in mood, sleep, appetite, temperature regulation, and sensory perception.

Dopamine

Amine neurotransmitter linked to emotion, reward, addiction, and skeletal muscle tone control.

Epinephrine

Amine neurotransmitter/hormone involved in arousal, dreaming, and mood regulation.

Norepinephrine

Primary autonomic neurotransmitter; influences arousal, dreaming, and mood.

Amino Acid Neurotransmitters

Most common transmitters in CNS and stored in PNS vesicles (e.g., glutamate, GABA).

Nitric Oxide (NO)

Gaseous neurotransmitter causing widespread vasodilation and muscle relaxation.

Enkephalins

Neuropeptides that act as natural opioids with pain-relieving effects.

Endorphins

Body’s endogenous opiates producing analgesia and euphoria.

Substance P

Neuropeptide that enhances perception of pain.

Short-Term Memory (Neural Basis)

Seconds-to-minutes storage due to transient facilitation or inhibition at synapses.

Long-Term Memory (Neural Basis)

Months-to-years storage requiring structural changes and increased information flow at synapses.

Multiple Sclerosis (MS)

Demyelinating disease that disrupts nerve conduction leading to neurological deficits.

Cerebrovascular Accident (Stroke)

Loss of blood flow causing reduced glucose/O₂ and neuronal damage.

Myasthenia Gravis

Autoimmune disorder where antibodies block ACh receptors at skeletal NMJ, causing muscle weakness.

Autism Spectrum Disorder

Developmental condition associated with synaptic signaling abnormalities affecting social and communication skills.

Nerve Damage

Physical injury to nerve fibers that impairs conduction of action potentials.