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NEURON FUNCTION WORKSHEET
CERTIFICATION SCRIPT 2026 QUESTIONS
WITH SOLUTIONS GRADED A+
◍ Define repolarization. Answer: Occurs immediately after depolarization and is the movement of positively charged ions back to the outside of the cell, returning the cell back to its original polarized state. A cell must repolarize before it can depolarize again.
◍ At what potential are the potassium ion gates closed?. Answer: The potassium ion gates close when the membrane potential reaches -80 mV
◍ Define depolarized. Answer: When an action potential is in progress the cell membrane is depolarized. The potential difference between the two sides of the membrane is decreased
◍ looking at model 1at what potential are the sodium ion gates closed. Answer: the sodium ion gates close when the membrane potential reaches +35 mV
◍ Which of the gated embedded proteins in Model 1 allow potassium ions ( triangles ) through the membrane?. Answer: Gates C, E, and G allow potassium ions through the membrane
◍ The neuron illustrated in Model 1 has received a signal from either a sensory cell (taste bud, skincell, retinal cell, etc.) or from another neuron. What evidence do you find in diagram 1 of themodel that indicates a signal has been received?. Answer: A signal Ligand has bound to the ligand-gated embedded protein
and the gate has opened
◍ C. Could another signal be sent down the length of the neuron cell if the sodium ions and potassium ions were not returned to their original position?. Answer: No, the neuron cannot transmit another signal until the ions are returned because the concentration gradients for the ions are going in the wrong direction
◍ Describe how the electrical signal in the neuron moves. Answer: the gates open one at a time from left to right in model 1. the high concentration of sodium ions inside the cell moves from left to right in model 1
◍ Schwann cells. Answer: Form myelin sheath in the PNS; provide myelin insulation to neurons in the peripheral nervous system
◍ Neurotransmitters. Answer: Chemicals released at the end of an axon terminal that diffuse across the synapse and transfer the nerve impulse to another nerve, muscle, or gland
◍ according to model 1 ,what is the membrane potential near sodium ion gates during the refractory period ?. Answer: the lowest potential in model 1 is -80mv
◍ Astrocytes. Answer: Largest and most numerous neuroglial cells; anchor neurons to blood capillaries and provide oxygen and nutrients
◍ When a signal moves down the axon of the neuron, which direction do sodium ions movethrough the voltage-gated embedded proteins?. Answer: sodium ions move into the cell when the sodium gates are opened
◍ Microglial cells. Answer: Sense and approach injured neurons; phagocytose bacteria and debris
ions diffused out of the immediate area and raised the potential to -55mv , the protein would open again
◍ define hyperpolarization. Answer: hyper means beyond normal. Hyperpolarization means there is a difference in membrane potential that is GREATER than normal
◍ Sodium-potassium pumps. Answer: Require ATP to open; pump 3 Na+ out and 2 K+ in to restore ion concentrations
◍ In diagram 2 of Model 1, gated embedded protein B has opened. Was this opening triggered bythe arrival of a signal ligand? If no, propose an alternate stimulus that might have triggered thegate to open.. Answer: No, diagram 2 does not show a ligand bound to embedded protein B. The gate may have opened because of the change in membrane potential from the flood of ions nearby
◍ Define refractory period. Answer: After a sodium ion gate has been opened and closed it is in a refractory period where the membrane potential in the immediate vicinity is very low and the embedded protein cannot be opened again. This is called hyperpolarizaton and and repolarization
◍ Which of the gated embedded proteins in Model 1 allow sodium ions ( O ) through the membrane?. Answer: gates A, B, D and F allow sodium ions through the membrane
◍ what is the job of a neuron. Answer: to move an electrical signal from one place to another in order to send sensory messages throughout the body
◍ Ependymal cells. Answer: Use cilia to circulate cerebrospinal fluid around the brain and spinal cord
◍ Neurons.
Answer: Main cells of the nervous system; send impulses from one part of the body to another; have a long lifespan and cannot divide
◍ Reflex Arc. Answer: Pathway followed by nerve impulses that produce a reflex action
◍ Concentration Gradient. Answer: Difference in concentration of ions on the inside versus the outside of a cell; causes ions to flow through channels to reach equilibrium
◍ Not every signal that a neuron receives is acted upon and transmitted to the next nerve cell. In some cases the signal is too weak to make the membrane potential reach the threshold potential. What advantage does the organism have when there is a minimum signal required that may have influenced the evolution of this mechanism?. Answer: organisms receive alot of sensory input. Not all of it is important. The necessity of a minimum signal to fire off an impulse saves resources to react to sensory information that is vital for survival.
◍ Action Potential. Answer: Quick electrical messages that travel down the axon of a neuron, reversing the charge of the axon from negative to positive
◍ One student described the diagrams in Model 1 by saying "As more gates open the concentrationof sodium inside the cell increases and this causes even more gates to open." Is this an example ofa positive or negative feedback loop?. Answer: This is a positive feedback because the end result of the process makes the process happen again and escalates the response. The response, opening of gated embedded proteins, amplifies the stimulus, a change in cell membrane potential.
◍ how is the degree of polarization measured?. Answer: the degree of polarization is measured by the cell membrane potential
◍ Synapse.
◍ the gated embedded proteins in the axon of a neuron are triggered to open by changes in electrical potential across the membrane.. Answer: the voltage at which they open is called the threshold potential
◍ Voltage-gated channels. Answer: Require only an impulse to open; involved in the flow of K+ and Na+ ions
