Chapter 12 - Section 12.4 - Study Guide - Assess Your Learning Outcomes - Page 471: 3

Stimulation of a neuron generates a local potential, which is also known as a graded potential. These local potentials are the initial electrical changes that occur in response to a stimulus, and they are essential for initiating and modulating the generation of action potentials in neurons. Let's explore how stimulation generates a local potential and the physiological properties of local potentials: **1. Stimulation of a Neuron:** - Stimulation of a neuron can occur through various mechanisms, such as the binding of neurotransmitters to receptor sites on the neuron's dendrites, mechanical deformation of the cell membrane, or changes in the local environment (e.g., changes in temperature or pH). - Neurotransmitters released from neighboring neurons can bind to receptors on the postsynaptic membrane, leading to changes in ion permeability and membrane potential. **2. Generation of a Local Potential:** - When a neuron is stimulated, it can result in the opening of ion channels in the neuron's cell membrane. - These ion channels can be ligand-gated (opened by neurotransmitters) or mechanically-gated (opened by physical deformation of the membrane). - The opening of these channels allows the movement of ions across the membrane, leading to changes in the local membrane potential. - The nature of the local potential (depolarization or hyperpolarization) depends on the specific ions involved and the direction of their movement. **3. Physiological Properties of Local Potentials:** Local potentials have several important physiological properties: - **Graded:** Local potentials are graded, meaning their magnitude varies with the strength of the stimulus. A stronger stimulus leads to a larger local potential, and a weaker stimulus results in a smaller local potential. - **Decremental:** Local potentials tend to decrease in strength as they spread away from the site of stimulation. This property is known as decremental conduction. As the electrical signal travels along the neuron's dendrites and cell body, it gradually diminishes in strength. - **Reversible:** Local potentials are reversible and do not always lead to the generation of an action potential. If the local potential is not strong enough to reach the threshold level (typically around -55 to -50 mV) to trigger an action potential, it will decay without propagating further. - **Summation:** Neurons can integrate multiple local potentials from different sources. If the summation of these local potentials brings the neuron's membrane potential closer to the threshold, it increases the likelihood of an action potential being generated. - **Local:** Local potentials are localized to specific regions of the neuron, typically in the dendrites and cell body. They do not propagate over long distances like action potentials, which travel along the axon. In summary, the stimulation of a neuron generates local potentials, which are graded and decremental changes in membrane potential resulting from the opening of ion channels. These local potentials serve as the initial electrical responses to stimuli and play a crucial role in determining whether an action potential will be generated. Local potentials can summate and influence the neuron's overall excitability and information processing.

Stimulation of a neuron generates a local potential, which is also known as a graded potential. These local potentials are the initial electrical changes that occur in response to a stimulus, and they are essential for initiating and modulating the generation of action potentials in neurons. Let's explore how stimulation generates a local potential and the physiological properties of local potentials: **1. Stimulation of a Neuron:** - Stimulation of a neuron can occur through various mechanisms, such as the binding of neurotransmitters to receptor sites on the neuron's dendrites, mechanical deformation of the cell membrane, or changes in the local environment (e.g., changes in temperature or pH). - Neurotransmitters released from neighboring neurons can bind to receptors on the postsynaptic membrane, leading to changes in ion permeability and membrane potential. **2. Generation of a Local Potential:** - When a neuron is stimulated, it can result in the opening of ion channels in the neuron's cell membrane. - These ion channels can be ligand-gated (opened by neurotransmitters) or mechanically-gated (opened by physical deformation of the membrane). - The opening of these channels allows the movement of ions across the membrane, leading to changes in the local membrane potential. - The nature of the local potential (depolarization or hyperpolarization) depends on the specific ions involved and the direction of their movement. **3. Physiological Properties of Local Potentials:** Local potentials have several important physiological properties: - **Graded:** Local potentials are graded, meaning their magnitude varies with the strength of the stimulus. A stronger stimulus leads to a larger local potential, and a weaker stimulus results in a smaller local potential. - **Decremental:** Local potentials tend to decrease in strength as they spread away from the site of stimulation. This property is known as decremental conduction. As the electrical signal travels along the neuron's dendrites and cell body, it gradually diminishes in strength. - **Reversible:** Local potentials are reversible and do not always lead to the generation of an action potential. If the local potential is not strong enough to reach the threshold level (typically around -55 to -50 mV) to trigger an action potential, it will decay without propagating further. - **Summation:** Neurons can integrate multiple local potentials from different sources. If the summation of these local potentials brings the neuron's membrane potential closer to the threshold, it increases the likelihood of an action potential being generated. - **Local:** Local potentials are localized to specific regions of the neuron, typically in the dendrites and cell body. They do not propagate over long distances like action potentials, which travel along the axon. In summary, the stimulation of a neuron generates local potentials, which are graded and decremental changes in membrane potential resulting from the opening of ion channels. These local potentials serve as the initial electrical responses to stimuli and play a crucial role in determining whether an action potential will be generated. Local potentials can summate and influence the neuron's overall excitability and information processing.