BIO 105 – Electrical Signals, Synapses, and Neurotransmitters

These flashcards review key points on neuronal electrical signals, synaptic transmission, neurotransmitter actions, memory mechanisms, and related disorders.

What is a nerve impulse (action potential)?

An electrochemical signal used by neurons to transmit information and to integrate thoughts within the brain and spinal cord.

Which ion distribution creates a neuron’s membrane potential?

More negatively charged ions inside the cell and more positively charged ions in the extracellular fluid.

What is the numerical value of a typical resting membrane potential (RMP)?

About –70 mV.

Which two mechanisms primarily restore the resting membrane potential after an action potential?

Gated ion channels and the sodium-potassium (Na⁺/K⁺) pump.

Describe the all-or-none principle of action potentials.

Once threshold is reached, the neuron fires completely and the action potential self-propagates without diminishing.

At approximately what membrane voltage is threshold reached to start an action potential?

Around –55 mV.

During which phase do voltage-gated Na⁺ channels open and Na⁺ floods into the cell?

Depolarizing phase.

What happens during the repolarizing phase of an action potential?

Voltage-gated K⁺ channels open, K⁺ exits the cell, and the Na⁺/K⁺ pump helps restore RMP.

Define the absolute refractory period.

A time when no second action potential can be generated, regardless of stimulus strength.

Define the relative refractory period.

A time when a stronger-than-normal stimulus can trigger another action potential.

In which type of axon does continuous conduction occur?

Unmyelinated axons.

What is saltatory conduction?

Rapid propagation in myelinated axons where the action potential “jumps” from one node of Ranvier to the next.

Name two factors that increase the speed of impulse propagation.

Greater myelination and larger axon diameter.

What is the role of a presynaptic neuron?

It sends the nerve impulse toward the synapse.

What is the synaptic cleft?

The small gap between the synaptic bulb of the presynaptic neuron and the postsynaptic membrane.

Which ion enters the synaptic bulb to trigger neurotransmitter release?

Calcium (Ca²⁺).

What does an excitatory postsynaptic potential (EPSP) cause?

Depolarization of the postsynaptic membrane, increasing the chance of an action potential.

What does an inhibitory postsynaptic potential (IPSP) cause?

Hyperpolarization of the postsynaptic membrane, decreasing the chance of an action potential.

List three ways neurotransmitters are removed from a synaptic cleft.

Diffusion, enzymatic degradation, and reuptake by the presynaptic neuron.

Which enzyme breaks down acetylcholine at skeletal neuromuscular junctions?

Acetylcholinesterase.

At the skeletal neuromuscular junction, acetylcholine is __ (excitatory or inhibitory?).

Excitatory.

At the cardiac neuromuscular junction, acetylcholine is __ (excitatory or inhibitory?).

Inhibitory.

Which neurotransmitter is linked to mood, appetite, sleep induction, and temperature regulation?

Serotonin.

Which neurotransmitter is involved in emotional responses, addictive behaviors, and regulating skeletal muscle tone?

Dopamine.

Which two catecholamines play roles in arousal from sleep, dreaming, and mood regulation?

Epinephrine and norepinephrine.

What is the primary physiological effect of nitric oxide (NO) as a neurotransmitter?

It causes widespread vasodilation and smooth muscle relaxation.

Which neuropeptides provide the body’s natural pain relief?

Enkephalins and endorphins.

What is the function of Substance P?

It enhances the body’s perception of pain.

How are short-term memories believed to be stored at synapses?

By facilitation or inhibition of neurotransmitter release at presynaptic terminals.

What structural change is required for long-term memory formation?

Physical remodeling of synapses within specific neural pathways.

Name one disorder caused by damage to myelin sheaths.

Multiple sclerosis (MS).

What autoimmune disorder blocks acetylcholine receptors at skeletal neuromuscular junctions?

Myasthenia gravis.

How can a cerebrovascular accident (stroke) impair nerve signaling?

By reducing blood flow, glucose, and oxygen to nervous tissue, damaging neurons and fibers.