Question 1

Use the information in the table to answer the question.

Calculate the equilibrium potential for sodium. Assume a temperature of 37°C.

Accepted Answer

Using the Nernst equation for sodium: 
E(Na) = (RT/zF) ln([Na]outside/[Na]inside)
At 37°C (310 K), R = 8.314 J/mol∙K, z = +1 for sodium, and F = 96,485 C/mol.
Assuming [Na]outside = 145 mM and [Na]inside = 15 mM (as given in the table):
E(Na) = (8.314 x 310 / 1 x 96,485) ln(145/15) = +48.2 mV

Question 2

The three stages of information processing in animals include ________.

Accepted Answer

The three stages of information processing in animals are sensory reception, an integrating center, and effectors (motor neurons), which are represented in option D. Option A lists different types of sensory systems, option B describes the structure of a neuron, and option C describes the process of neurotransmission at a synapse.

Question 3

The concentrations of ions are very different inside and outside a nerve cell due to ________.

Accepted Answer

The concentrations of ions inside and outside a nerve cell are maintained by the active transport of ions by sodium-potassium pumps. These pumps move three sodium ions out of the cell for every two potassium ions moved into the cell, creating a concentration gradient that allows for the generation and transmission of electrical signals. Osmosis and diffusion play a role in the movement of water and molecules across the cell membrane, but they do not specifically account for the ion concentration gradient. Symports and antiports are types of transport proteins that move molecules across the membrane but are not directly involved in the maintenance of the ion concentration gradient.

Question 4

The motor (somatic nervous) system can alter the activities of its targets, the skeletal muscle fibers, because ________.

Accepted Answer

The somatic nervous system controls skeletal muscle fibers by releasing signals (neurotransmitters) at the neuromuscular junctions, where these signals bind to receptor proteins on the muscles and initiate the contraction process.

Question 5

The operation of the sodium-potassium pump moves ________.

Accepted Answer

The sodium-potassium pump is an active transport mechanism that moves ions against their concentration gradients. It moves three sodium ions out of the cell and two potassium ions into the cell, resulting in a net exchange of one positive charge from the intracellular to the extracellular side of the membrane. Therefore, the correct answer is sodium ions out of the cell and potassium ions into the cell.

Question 6

In a resting potential, an example of a cation that is more abundant as a solute in the cytosol of a neuron than it is in the interstitial fluid outside the neuron is ________.

Accepted Answer

The cation that is more abundant in the cytosol of a neuron compared to the interstitial fluid is K⁺. This is because K⁺ channels in the cell membrane allow K⁺ to move out of the cell, leading to a higher concentration of K⁺ in the cytosol. This gradient is important for maintaining the resting potential of -70 mV in neurons. Other options like Na⁺, Ca⁺⁺, and Cl⁻ are typically more abundant in the interstitial fluid compared to the cytosol of a neuron.

Question 7

If you experimentally increase the concentration of Na⁺ outside a cell while maintaining other ion concentrations as they were, what would happen to the cell's membrane potential?

Accepted Answer

Increasing the concentration of Na⁺ outside the cell will result in a decrease in the concentration gradient of Na⁺ across the membrane. Since Na⁺ is positively charged, a decrease in its concentration gradient would result in a more positive membrane potential. Therefore, the membrane potential would become more positive.

Question 8

Which of the following ions is most likely to cross the plasma membrane of a resting neuron?

Accepted Answer

The resting membrane potential of a neuron is primarily influenced by the ion concentrations of K⁺ and Na⁺. At rest, the neuron is more permeable to K⁺, meaning that it is more likely to cross the plasma membrane. Na⁺ is also able to cross the membrane, but to a lesser extent. Ca²⁺ is primarily involved in synaptic neurotransmitter release and is less likely to cross the membrane. Cl⁻ is negatively charged and would require an active transport mechanism to cross the membrane.

Question 9

Two fundamental concepts about the ion channels of a "resting" neuron are that the channels ________.

Accepted Answer

Ion channels can be open or closed depending on their type, and each channel is specific as to which ion can traverse them. During resting conditions, some ion channels are closed, while others are open to maintain a resting potential.

Question 10

Refer to the following graph of an action potential to answer the question.

The membrane's permeability to sodium ions is greatest at label ________.

Accepted Answer

At label B, the membrane's permeability to sodium ions is greatest as there is a rapid influx of sodium ions into the cell, resulting in the depolarization phase of the action potential. This is due to the opening of voltage-gated sodium channels, allowing more sodium ions to flow into the cell than any other point in the graph.

Question 11

A researcher uses the chemical inhibitor cyanide to reduce ATP production in a neuron. What would be one effect of preventing ATP production?

Accepted Answer

ATP is required for the function of the sodium-potassium pump, which helps maintain the normal distribution of potassium and sodium ions across the neuron's plasma membrane. Without ATP, the pump would not function properly, leading to a disruption of the resting distribution of ions.

Question 12

In a simple synapse, neurotransmitter chemicals are released by ________.

Accepted Answer

Neurotransmitter chemicals are released by the presynaptic membrane of a neuron during a synapse, where they then bind to receptors on the postsynaptic membrane of another neuron.

Question 13

The membrane potential in which there is no net movement of the ion across the membrane is called the ________.

Accepted Answer

Equilibrium potential is the membrane potential at which there is no net flow of an ion across the membrane. In other words, the concentration gradient and the electrical gradient are balanced and there is no driving force for the ion to move. Graded potential refers to changes in the membrane potential that are not strong enough to trigger an action potential. Threshold potential refers to the minimum membrane potential required to generate an action potential. Action potential refers to the rapid change in membrane potential that allows for communication along a neuron or muscle cell.

Question 14

Although the membrane of a "resting" neuron is highly permeable to potassium ions, its membrane potential does not exactly match the equilibrium potential for potassium because the neuronal membrane is also ________.

Accepted Answer

The membrane is slightly permeable to sodium ions, which also contributes to the membrane potential not exactly matching the equilibrium potential for potassium.

Question 15

Refer to the following graph of an action potential to answer the question.

The membrane potential is closest to the equilibrium potential for potassium at label ________.

Accepted Answer

The answer of Refer to the following graph of an...

Question 16

The Nernst equation specifies the equilibrium potential for a particular ion. This equilibrium potential is a function of ________.

Accepted Answer

The Nernst equation calculates the equilibrium potential for a specific ion based on the concentration gradient of that ion across the cell membrane.

Question 17

Most of the neurons in the human central nervous system are ________.

Accepted Answer

Interneurons make up the majority of neurons in the central nervous system (CNS) and are responsible for connecting sensory and motor neurons. Sensory neurons receive input from sensory organs and transmit it to the CNS, while motor neurons receive signals from the CNS and control muscles and glands. Peripheral neurons are located outside of the CNS, in the peripheral nervous system.

Question 18

Use the information in the table to answer the question.

Calculate the equilibrium potential for potassium. Assume a temperature of 37°C.

Accepted Answer

Using the Nernst equation: 
E = RT/zF * ln([K+]/[K+]) 
where R is the gas constant (8.314 J/mol*K), T is the temperature in Kelvin (37°C = 310 K), z is the charge (1 for potassium), F is the Faraday constant (96,485 C/mol), [K+] is the concentration of potassium (120 mM in this case), and [K+] is the concentration outside the cell (4 mM). Plugging in the values gives: 
E = (8.314 J/mol*K)(310 K)/(1)(96,485 C/mol) * ln(120/4) 
E = -58.4 mV, which is choice C.

Question 19

The point of connection between two communicating neurons is called the ________.

Accepted Answer

The synapse is the point of connection between two neurons where communication occurs. The axon hillock is part of the cell body and is where the axon originates. Dendrites are the part of the neuron that receive signals from other neurons. The cell body contains the nucleus and most of the cell's organelles, but is not directly involved in communication between neurons.

Question 20

In a simple synapse, neurotransmitter chemicals are received by ________.

Accepted Answer

Neurotransmitter chemicals are received by dendrites in a simple synapse. The dendrites contain receptors that bind to the neurotransmitters, triggering a response in the postsynaptic neuron. The other options listed (presynaptic membrane, axon hillocks, cell bodies) are not typically involved in receiving neurotransmitter chemicals in a simple synapse.

Quiz 48: Neurons, Synapses, and Signaling

Use the information in the table to answer the question. Calculate the equilibrium potential for sodium. Assume a temperature of 37°C.