Neuron Function How does a signal travel across and between neurons? Why? Just as the coaxial cables that run down your street or through your house carry television and Internet signals, the job of a neuron is to move an electrical signal from one place to another in order to send sensory messages throughout the body. In a previous activity you saw how a membrane potential is formed both at rest and during an inflow of ions. In this activity you will explore how changes in membrane potentials can propagate a signal down the axon of a neuron. 1. Which of the gated embedded proteins in Model 1 allow sodium ions ( ) through the membrane? 2. Which of the gated embedded proteins in Model 1 allow potassium ions ( ) through the membrane? 3. The neuron illustrated in Model 1 has received a signal from either a sensory cell (taste bud, skin cell, retinal cell, etc.) or from another neuron. What evidence do you find in diagram 1 of the model that indicates a signal has been received? 4. In diagram 2 of Model 1, gated embedded protein B has opened. Was this opening triggered by the arrival of a signal ligand? If no, propose an alternate stimulus that might have triggered the gate to open. 5. Consider Model 1. a. When a signal moves down the axon of the neuron, which direction do sodium ions move through the voltage-gated embedded proteins? b. What does the movement of sodium ions across the membrane do to the membrane potential near the open embedded protein? 6. Consider Model 1. a. When a signal moves through the axon of the neuron, which direction do potassium ions move through the voltage-gated embedded proteins? b. What does the movement of potassium ions across the membrane do to the membrane potential near the open embedded protein? GatesA BDandFallowsodiumionsthroughthemembrane GatesC EandGallowpotassiumionsthroughthemembrane Asignalligandhasboundtotheligandgatedembeddedproteinandthegatehasopened Nodiagram2doesnotshowaligandboundtoembeddedproteinBThegatemayhave openedbecauseofthechangeinmembranepotentialfromthefloodofionsnearby Sodiumionsmoveintothecellwhenthesodiumgatesareopened Themembranepotentialincreasesgetsmorepositiveasthesodiumionsmoveintothecell Potassiumionsmoveoutofthecellwhenthepotassiumgatesareopened Themembranepotentialdecreasesgetsmorenegative asthepotassiumionsmoveoutof thecel