Graded/Local Potentials Flashcards

Study Notes

Hyperpolarization

Increases cell polarization by making the inside more negative compared to the outside.
Achieved by opening K+ channels, facilitating the exit of positive charges.
Results in a membrane potential greater than -70 mV, making action potentials less likely.

Depolarization

Reduces cell polarization, making it more positive.
A graded potential rising from -70 mV to -65 mV results in a +5 mV change.
Brings cell potential closer to the action potential threshold of -50 mV, increasing likelihood of action potentials.

Mechanism for Depolarization

Can be initiated by a chemical stimulus, such as neurotransmitters.
Dendrites with sodium-gated channels receive ligands (e.g., acetylcholine), leading to sodium channel activation and cell depolarization.

Role of Sodium-Potassium Pump

Continuously operates in the background during graded and local potential changes.
Maintains ion concentration gradients even as other ions enter the cell.

Local Potential Change

Defined as a short-range change in membrane potential triggered by a stimulus.

Graded Potential

Synonymous with local potential.
Graded potentials are essential for generating action potentials; they are smaller in magnitude.
Their strength increases with a stronger stimulus due to more ions entering the cell.
Occur locally, initiated at the site of stimulation, and proportionate to stimulus size.
Present in various cell types, demonstrating versatility in neuronal signaling.

Spreading of Graded Potential

Cations move towards negatively charged areas, propagating depolarization locally.
Neighboring sites can also depolarize due to positive charge diffusion, creating additional graded potentials.
Graded potentials can spread out in both directions along the membrane but decay over distance; less decay occurs near the trigger zone, enhancing action potential generation.

Trigger Zone

Located at the beginning of the axon, it is critical for the initiation of action potentials.

Threshold Potential

The essential membrane potential around the trigger zone, typically around -50 mV.
Once this threshold is surpassed due to cumulative graded potentials, an action potential is triggered, traveling down the axon.

Summations

The process of accumulating multiple graded potentials at the trigger zone, fundamental for information processing in neurons.

Description

Test your knowledge on graded and local potentials with these flashcards. Dive into the concepts of hyperpolarization and depolarization, and understand their impact on action potentials. Ideal for students looking to reinforce their understanding of cell membrane dynamics.