Chapter 12 - Nervous Tissue - Study Guide - Testing Your Comprehension - Page 473: 3

If a poison were to slow down the sodium-potassium (Na+-K+) pumps in nerve cells, it would have a significant impact on the resting membrane potentials (RMPs) of neurons. Let's explore how this would affect neural excitability and responsiveness: 1. **Normal Function of Na+-K+ Pumps**: - The Na+-K+ pumps are essential for maintaining the normal ionic gradients across the neuronal cell membrane. They actively transport sodium ions (Na+) out of the cell and potassium ions (K+) into the cell against their respective concentration gradients. - This pump action helps establish and maintain the RMP of neurons. It ensures that there are more sodium ions outside the cell and more potassium ions inside the cell, contributing to the negative RMP (typically around -70 mV). 2. **Effect of Slowed Na+-K+ Pumps**: - Slowing down the Na+-K+ pumps would impair their ability to maintain the ionic gradients. Specifically, it would hinder the ability of the pumps to actively transport sodium ions out of the cell and potassium ions into the cell. - As a result, there would be a gradual buildup of sodium ions inside the cell and a decrease in potassium ions inside the cell over time. 3. **Effect on RMP and Neural Excitability**: - The slowing down of the Na+-K+ pumps would lead to a gradual depolarization of the RMP. This means that the RMP would become less negative and move closer to zero mV. - A less negative RMP means that neurons are closer to their threshold for firing action potentials. This makes neurons more excitable because it would take less external stimulation to reach the threshold and initiate an action potential. - Neurons may also become more prone to spontaneous firing, even without external stimuli, due to the closer proximity to the threshold. 4. **Consequences for Neuronal Function**: - The increased excitability of neurons due to the slowed Na+-K+ pumps could lead to overexcitability and potentially result in excessive or inappropriate neural signaling. - Neurons may fire action potentials more easily, which can manifest as increased sensitivity to stimuli, a lower threshold for activation, and a greater likelihood of generating spontaneous action potentials. In summary, if a poison were to slow down the Na+-K+ pumps of nerve cells, it would lead to a gradual depolarization of the resting membrane potentials, making neurons more excitable than normal. This increased excitability could have detrimental effects on the normal functioning of the nervous system, potentially causing excessive neural activity and altered sensory or motor responses.

If a poison were to slow down the sodium-potassium (Na+-K+) pumps in nerve cells, it would have a significant impact on the resting membrane potentials (RMPs) of neurons. Let's explore how this would affect neural excitability and responsiveness: 1. **Normal Function of Na+-K+ Pumps**: - The Na+-K+ pumps are essential for maintaining the normal ionic gradients across the neuronal cell membrane. They actively transport sodium ions (Na+) out of the cell and potassium ions (K+) into the cell against their respective concentration gradients. - This pump action helps establish and maintain the RMP of neurons. It ensures that there are more sodium ions outside the cell and more potassium ions inside the cell, contributing to the negative RMP (typically around -70 mV). 2. **Effect of Slowed Na+-K+ Pumps**: - Slowing down the Na+-K+ pumps would impair their ability to maintain the ionic gradients. Specifically, it would hinder the ability of the pumps to actively transport sodium ions out of the cell and potassium ions into the cell. - As a result, there would be a gradual buildup of sodium ions inside the cell and a decrease in potassium ions inside the cell over time. 3. **Effect on RMP and Neural Excitability**: - The slowing down of the Na+-K+ pumps would lead to a gradual depolarization of the RMP. This means that the RMP would become less negative and move closer to zero mV. - A less negative RMP means that neurons are closer to their threshold for firing action potentials. This makes neurons more excitable because it would take less external stimulation to reach the threshold and initiate an action potential. - Neurons may also become more prone to spontaneous firing, even without external stimuli, due to the closer proximity to the threshold. 4. **Consequences for Neuronal Function**: - The increased excitability of neurons due to the slowed Na+-K+ pumps could lead to overexcitability and potentially result in excessive or inappropriate neural signaling. - Neurons may fire action potentials more easily, which can manifest as increased sensitivity to stimuli, a lower threshold for activation, and a greater likelihood of generating spontaneous action potentials. In summary, if a poison were to slow down the Na+-K+ pumps of nerve cells, it would lead to a gradual depolarization of the resting membrane potentials, making neurons more excitable than normal. This increased excitability could have detrimental effects on the normal functioning of the nervous system, potentially causing excessive neural activity and altered sensory or motor responses.