Graded potentials

Definition

Graded potentials are changes in membrane potential that vary in size and occur in response to a stimulus, allowing neurons to communicate signals. They can be depolarizing or hyperpolarizing and are localized to specific regions of the neuron, primarily occurring in dendrites and the cell body. Unlike action potentials, graded potentials do not follow the all-or-nothing principle; their amplitude is proportional to the strength of the stimulus.

5 Must Know Facts For Your Next Test

1. Graded potentials can vary in size, meaning they can be small or large depending on the intensity of the stimulus that triggers them.
2. They decrease in strength as they move away from the point of origin, a phenomenon known as decremental conduction.
3. Graded potentials can summate, meaning multiple inputs can combine to produce a larger change in membrane potential.
4. These potentials play a crucial role in integrating signals received by a neuron before determining whether to fire an action potential.
5. Graded potentials can result from various types of stimuli, including chemical (neurotransmitter) and physical (mechanical) changes.

Review Questions

• How do graded potentials contribute to the overall function of neurons in transmitting signals?
  • Graded potentials play a key role in neuronal signaling by allowing neurons to integrate and process incoming stimuli. When a neuron receives input, graded potentials occur locally, either depolarizing or hyperpolarizing the membrane potential. If these changes are strong enough and reach the axon hillock, they can summate and potentially trigger an action potential, which then propagates along the axon. This process is essential for effective communication between neurons.
• In what ways do graded potentials differ from action potentials in terms of their properties and roles within neuronal communication?
  • Graded potentials differ significantly from action potentials in several aspects. While graded potentials vary in amplitude based on stimulus strength and decrease with distance from the site of stimulation, action potentials are all-or-nothing events that maintain a consistent amplitude. Additionally, graded potentials can summate over time and space, influencing whether an action potential is initiated, while action potentials are uniform and travel along the axon without losing strength.
• Evaluate how graded potentials affect synaptic transmission and neuronal integration within networks of connected neurons.
  • Graded potentials are crucial for synaptic transmission as they arise from neurotransmitter binding at synapses, leading to changes in membrane potential. These localized changes can either promote or inhibit the likelihood of generating action potentials in connected neurons. By allowing multiple signals to summate, graded potentials enable neurons to integrate various inputs from their surroundings effectively. This integration determines neuronal response patterns within complex neural circuits, influencing behavior and physiological responses.

Related terms

Action potentials: Rapid, large changes in membrane potential that occur once a threshold is reached, leading to the propagation of electrical signals along the axon.

Resting membrane potential: The stable, baseline electrical charge across the neuronal membrane when the neuron is not transmitting signals, typically around -70 mV.

Synaptic transmission: The process by which neurotransmitters are released from one neuron and bind to receptors on another neuron, resulting in graded potentials.