Action Potential Worksheet, Assignments of Biology

Download Action Potential Worksheet and more Assignments Biology in PDF only on Docsity! Action Potential Worksheet Name: _________________________ I. Resting Potential (resting potential, sodium-potassium pump) 1. What is the condition of a nerve cell at resting potential (the charge, location of different ions, etc.)? At resting potential, a nerve cell's membrane maintains a negative charge inside relative to the outside. This is typically around -70 millivolts in neurons. The key ions involved are potassium (K+), which is more concentrated inside the cell, and sodium (Na+) and chloride (Cl-) ions, which are more concentrated outside. The cell's resting potential is primarily established and maintained by the sodium-potassium pump, which actively transports three sodium ions out of the cell for every two potassium ions pumped in. Additionally, there are potassium leak channels that allow a small amount of K+ to leak out, contributing to the negative resting potential. This difference in ion concentration and selective ion permeability across the cell membrane is essential for the cell's ability to generate action potentials and transmit signals. 2. If a neuron’s membrane suddenly becomes more permeable to sodium ions, there is a rapid net transport of the sodium ions into the cell. What are the two forces that drive the ions inward? Concentration Gradient: Sodium ions move from an area of higher concentration (outside the cell) to an area of lower concentration (inside the cell). Electrostatic Attraction: Sodium ions are positively charged, and the interior of the neuron is negatively charged. This electrostatic attraction also pulls sodium ions into the cell. II. Action Potential (stimulus, action potential, threshold potential) 1. What is an action potential? Action potential is a brief electrical impulse that travels down the axon of a neuron, allowing it to transmit signals over long distances. 2. What is a stimulus and how does it trigger an action potential? A stimulus is a signal or change in the environment that can excite a neuron. When a stimulus reaches a neuron's threshold of excitation, it opens ion channels, allowing an influx of sodium ions, which depolarizes the cell membrane. This depolarization triggers an action potential, a brief electrical impulse that travels along the neuron's axon, enabling the transmission of information. 3. Explain what happens during an action potential (charge, flow of ions, gates, threshold potential). During an action potential, a neuron's membrane potential rapidly changes. It begins with a resting membrane potential, typically around -70mV. When a stimulus surpasses the threshold potential (usually around -55mV), voltage-gated sodium channels open, allowing an influx of sodium ions, causing depolarization. This creates a positive charge inside the neuron, raising the membrane potential to about +30mV. Subsequently, voltage-gated potassium channels open, leading to an efflux of potassium ions, repolarizing the membrane. Finally, the membrane briefly hyperpolarizes before returning to the resting potential, as ion channels close and the sodium-potassium pump restores ion balance. 1. What occurs at the synapse? At the synapse, which is the junction between two neurons, neurotransmitters are released from the presynaptic neuron into the synaptic cleft. These neurotransmitters bind to receptors on the postsynaptic neuron, transmitting signals and enabling communication between neurons. 2. Why does the message travel in only one direction? In a synapse, messages travel in only one direction due to the presence of neurotransmitter receptors on one side (the postsynaptic membrane) and the absence of such receptors on the other side (the presynaptic membrane). IV. Chemical synapse (Summation) 1. What do neurotransmitters actually do to receiving neurons? Neurotransmitters are chemical messengers that transmit signals between neurons. When released into the synaptic cleft, neurotransmitters bind to receptors on the receiving neuron, either exciting or inhibiting its activity. This binding can lead to the generation of action potentials and the transmission of information across the nervous system. 2. What is the difference between excitatory and inhibitory neurotransmitters? Excitatory neurotransmitter cause depolarization (decrease in membrane potential). Inhibitory neurotransmitter cause hyperpolarization (increase in membrane potential).