BIO 105 – Electrical Signaling & Synaptic Physiology

Vocabulary flashcards covering key terms from BIO 105 lecture notes on neuronal electrical signaling, synaptic physiology, neurotransmitters, memory, and related disorders.

Action Potential (Nerve Impulse)

An all-or-none electrochemical wave that travels along a neuron’s membrane to transmit information.

Membrane Potential

Voltage difference across a neuron’s plasma membrane caused by unequal ion distribution.

Resting Membrane Potential (RMP)

Baseline −70 mV charge inside a resting neuron; the cell is said to be polarized.

Gated Ion Channel

Membrane protein that opens or closes in response to stimuli, helping reset or change membrane potential.

Sodium-Potassium Pump

Active transporter that moves 3 Na⁺ out and 2 K⁺ in, restoring and maintaining the RMP.

Polarized Phase

Initial state of a neuron at RMP before stimulation.

Threshold Potential

Approximately −55 mV; the voltage that triggers opening of voltage-gated Na⁺ channels to start an action potential.

Depolarizing Phase

Stage in which Na⁺ rushes into the cell, making the interior less negative.

Repolarizing Phase

Stage in which K⁺ exits and the Na⁺/K⁺ pump works to return the membrane toward RMP.

Refractory Period

Brief time after an action potential when the neuron resists re-stimulation.

Absolute Refractory Period

Phase when no new action potential can be generated, regardless of stimulus strength.

Relative Refractory Period

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

Continuous Conduction

Slow, step-by-step propagation of impulses along unmyelinated axons.

Saltatory Conduction

Rapid “leaping” of action potentials between nodes of Ranvier on myelinated axons.

Myelination

Insulating sheath around axons; greater myelin yields faster impulse conduction.

Axon Diameter

Larger diameter fibers conduct impulses more rapidly than thinner ones.

Synapse

Junction where a neuron communicates with another cell.

Presynaptic Neuron

The sending neuron that releases neurotransmitter into the synapse.

Postsynaptic Neuron

The receiving neuron that binds neurotransmitter and may generate a new impulse.

Synaptic Bulb (Knob)

Enlarged axon terminal containing neurotransmitter-filled vesicles.

Synaptic Cleft

Tiny extracellular gap between presynaptic bulb and postsynaptic membrane.

Calcium’s Role in Synapse

Influx of Ca²⁺ into the presynaptic bulb triggers exocytosis of neurotransmitter vesicles.

Exocytosis (at Synapse)

Vesicular release of neurotransmitter into the synaptic cleft.

Excitatory Postsynaptic Potential (EPSP)

Depolarization of the postsynaptic membrane that moves it closer to threshold.

Inhibitory Postsynaptic Potential (IPSP)

Hyperpolarization of the postsynaptic membrane that moves it farther from threshold.

Diffusion (NT Clearance)

Neurotransmitter drifts away into interstitial fluid, ending its action.

Enzymatic Degradation

Breakdown of neurotransmitter by enzymes, e.g., acetylcholinesterase for ACh.

Reuptake (Presynaptic Uptake)

Transport of neurotransmitter back into the presynaptic neuron for recycling.

Acetylcholine (ACh)

Neurotransmitter that is excitatory at skeletal NMJ and inhibitory at cardiac muscle.

Serotonin

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

Dopamine

Amine that modulates emotion, reward, addictive behavior, and skeletal muscle tone.

Epinephrine

Amine involved in arousal, dreaming, and mood regulation; part of fight-or-flight response.

Norepinephrine

Main autonomic neurotransmitter; influences wakefulness, mood, and dreaming.

Amino Acid Neurotransmitters

Common transmitters stored in PNS synaptic vesicles (e.g., glutamate, GABA, glycine).

Nitric Oxide (NO)

Gaseous transmitter causing widespread vasodilation and smooth muscle relaxation.

Enkephalins

Neuropeptides that act as natural opiates, reducing pain perception.

Endorphins

Body’s endogenous opioids with pain-relieving and euphoria-inducing effects.

Substance P

Neuropeptide that enhances perception of pain.

Synaptic Plasticity

Ability of synapses to strengthen or weaken, forming the basis of learning and memory.

Short-Term Memory

Seconds-to-minutes storage produced by facilitation or inhibition at existing synapses.

Long-Term Memory

Months-to-years storage requiring structural synaptic changes, such as new dendritic spines.

Multiple Sclerosis (MS)

Demyelinating disease that impairs nerve conduction in the CNS.

Cerebrovascular Accident (Stroke)

Loss of brain function due to reduced blood flow, depleting glucose and O₂ to neurons.

Myasthenia Gravis

Autoimmune disorder where antibodies block ACh receptors at skeletal NMJs.

Autism Spectrum Disorder

Neurodevelopmental condition linked to atypical synaptic signaling and network connectivity.