Question 1

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 ________.
A) A
B) B
C) C
D) D Disallow randomisation

Accepted Answer

D

Question 2

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 ________.
A) Cl-
B) Ca⁺⁺
C) Na⁺
D) K⁺

Accepted Answer

The resting potential of a neuron is primarily maintained by the unequal distribution of ions across the plasma membrane, with K⁺ ions being more concentrated in the cytosol of the neuron than in the interstitial fluid outside. In fact, the concentration gradient for K⁺ is the main driving force for the resting potential, as K⁺ tends to leak out of the neuron through K⁺ leak channels, making the inside of the neuron more negative. The concentrations of Cl-, Ca⁺⁺, and Na⁺ are all higher outside the neuron relative to inside, so they cannot be the correct answer.

Question 3

The concentrations of ions are very different inside and outside a nerve cell due to ________.
A) osmosis
B) diffusion
C) sodium-potassium pumps
D) symports and antiports

Accepted Answer

The concentration of ions being different inside and outside a nerve cell is due to the activity of sodium-potassium pumps, which actively transport sodium ions out of the cell and potassium ions into the cell. This creates a concentration gradient that allows for the transmission of electrical impulses. Osmosis and diffusion may impact the movement of water and molecules across the cell membrane, but they do not account for the concentration of ions specifically. Symports and antiports refer to types of transport proteins, but they do not fully explain the concentration differences between inside and outside the cell.

Question 4

The point of connection between two communicating neurons is called the ________.
A) axon hillock
B) dendrite
C) synapse
D) cell body

Accepted Answer

The synapse is the point of connection between two communicating neurons where one neuron sends a neurotransmitter across a tiny gap to another neuron or other target cell. The other options listed are parts of an individual neuron, but not the point of connection between two neurons.

Question 5

The operation of the sodium-potassium pump moves ________.
A) sodium and potassium ions into the cell
B) sodium and potassium ions out of the cell
C) sodium ions into the cell and potassium ions out of the cell
D) sodium ions out of the cell and potassium ions into the cell

Accepted Answer

The sodium-potassium pump is a type of ion pump that uses energy (in the form of ATP) to move three sodium ions out of the cell and two potassium ions into the cell. This creates an electrochemical gradient across the membrane, which is important for various cellular processes such as nerve transmission and muscle contraction. Therefore, the correct answer is D, as the sodium and potassium ions are moved in opposite directions by the pump.

Question 6

The three stages of information processing in animals include ________.
A) chemical senses, mechanoreception, and vision
B) dendrites, a cell body, and an axon
C) a presynaptic cell, neurotransmitters, and a postsynaptic cell
D) sensory reception, an integrating centre, and effectors (motor neurons)

Accepted Answer

The three stages of information processing in animals are sensory reception (receiving information from the environment), an integrating center (processing and interpreting the information received), and effectors (motor neurons, which carry out a response based on the interpreted information). Option A refers to different types of sensory receptors, Option B describes the basic structure of a neuron, and Option C refers to the process of neurotransmission at a synapse.

Question 7

The motor (somatic nervous) system can alter the activities of its targets, the skeletal muscle fibres, because ________.
A) it is electrically coupled by gap junctions to the muscles
B) its signals bind to receptor proteins on the muscles
C) its signals reach the muscles via the blood
D) it is connected to the internal neural network of the muscles

Accepted Answer

The motor (somatic nervous) system can alter the activities of its targets, the skeletal muscle fibres, because its signals bind to receptor proteins on the muscles, causing them to contract. The other options (A,C, and D) are not accurate explanations of the interaction between the nervous system and skeletal muscles.

Question 8

Most of the neurons in the human central nervous system are ________.
A) sensory neurons
B) motor neurons
C) interneurons
D) peripheral neurons

Accepted Answer

Interneurons are responsible for connecting sensory and motor neurons in the central nervous system, and they make up the majority of neurons in this system. Sensory neurons are responsible for carrying information from sensory organs to the central nervous system, while motor neurons carry information from the central nervous system to muscles and glands. Peripheral neurons refer to all neurons outside of the central nervous system.

Question 9

Refer to the following graph of an action potential to answer the question.  The membrane's permeability to sodium ions is greatest at label ________.
A) A
B) B
C) C
D) D Disallow randomisation

Accepted Answer

The graph shows that the peak of the action potential coincides with the increase in the permeability of sodium ions. Therefore, the label with the highest point in the graph is where the membrane's permeability to sodium ions is greatest, which is at label B.

Question 10

$$\begin{array} { | l | l | l | } 
\hline & \begin{array} { l } 
\bf{ Extracellular-concentration } \
( \bf { mM } )
\end{array} & \begin{array} { l } 
\bf { Intracellular-concentration } \
( \bf { mM } )
\end{array} \
\bf{ Inn }\
\hline \mathbf  { Na } ^ { + } & 300 & 50 \
\hline \mathbf { K } ^ { + } & 40 & 350 \
\hline
\end{array}$$
-Calculate the equilibrium potential for sodium. Assume a temperature of 37°C.
A) +48.2 mV
B) 0.0 mV
C) -58.4 mV
D) -80.0 mV

Accepted Answer

The equilibrium potential for sodium can be calculated using the Nernst equation: $ E_{Na} = \frac{RT}{zF} \ln \left( \frac{[Na^+]_{outside}}{[Na^+]_{inside}} \right) $. At 37°C, this simplifies to approximately $ E_{Na} = 61.5 \log \left( \frac{300}{50} \right) $, which equals +48.2 mV.

Question 11

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 ________.
A) slightly permeable to sodium ions
B) fully permeable to calcium ions
C) impermeable to sodium ions
D) highly permeable to chloride ions

Accepted Answer

Although the resting neuron membrane is highly permeable to potassium ions, it is also slightly permeable to sodium ions. This causes a small influx of sodium ions, which prevents the membrane potential from exactly matching the equilibrium potential for potassium.

Question 12

A researcher uses the chemical inhibitor cyanide to reduce ATP production in a neuron. What would be one effect of preventing ATP production?
A) The sodium and potassium channels would all be closed.
B) The membrane would become more permeable to sodium.
C) Disruption to the normal "resting" distribution of potassium and sodium ions.
D) A physical breakdown of the plasma membrane would occur.

Accepted Answer

ATP is required for the sodium-potassium pump to maintain the normal distribution of ions across the neuron's membrane. Without ATP, the cell would no longer be able to maintain its ion balance, leading to disruption of its normal resting potential.

Question 13

The membrane potential in which there is no net movement of the ion across the membrane is called the ________.
A) graded potential
B) threshold potential
C) equilibrium potential
D) action potential

Accepted Answer

The equilibrium potential is the membrane potential at which there is no net movement of a particular ion across the membrane. This occurs when the electrical gradient and the concentration gradient for that ion are balanced. Graded potentials are changes in the membrane potential that do not reach the threshold for an action potential. The threshold potential is the membrane potential at which an action potential is triggered. An action potential is a rapid and transient change in the membrane potential that allows for long-distance signaling in neurons. Therefore, option C is the correct choice.

Question 14

In a simple synapse, neurotransmitter chemicals are released by ________.
A) the presynaptic membrane
B) axon hillocks
C) cell bodies
D) ducts on the smooth endoplasmic reticulum

Accepted Answer

Neurotransmitter chemicals are released by the presynaptic membrane, which is the end of the axon closest to the synapse.

Question 15

Two fundamental concepts about the ion channels of a "resting" neuron are that the channels ________.
A) are always open, but the concentration gradients of ions frequently change
B) are always closed, but ions move closer to the channels during excitation
C) are open or closed depending on their type, and are specific as to which ion can traverse them
D) open in response to stimuli, and then close simultaneously, in unison

Accepted Answer

Ion channels of a "resting" neuron are specific as to which ion can traverse them and can be open or closed depending on their type. This is what allows for selective permeability and the maintenance of resting membrane potential. Option A is incorrect because ion channels are not always open. Option B is incorrect because ion channels do not move, rather ions move towards them during excitation. Option D is incorrect because ion channels do not open and close in unison, but rather independently.

Question 16

$$\begin{array} { | l | l | l | } 
\hline & \begin{array} { l } 
\bf{ Extracellular-concentration } \
( \bf { mM } )
\end{array} & \begin{array} { l } 
\bf { Intracellular-concentration } \
( \bf { mM } )
\end{array} \
\bf{ Inn }\
\hline \mathbf  { Na } ^ { + } & 300 & 50 \
\hline \mathbf { K } ^ { + } & 40 & 350 \
\hline
\end{array}$$
-Calculate the equilibrium potential for potassium. Assume a temperature of 37°C.
A) +48.2 mV
B) 0.0 mV
C) -58.4 mV
D) -80.0 mV

Accepted Answer

The equilibrium potential for potassium can be calculated using the Nernst equation:E = (RT/zF) * ln([K+]o/[K+]i)where:E is the equilibrium potential in voltsR is the ideal gas constant (8.314 J/mol*K)T is the absolute temperature in Kelvin (37°C = 310K)z is the valence of the ion (+1 for potassium)F is the Faraday constant (96,485 C/mol)[K+]o is the extracellular potassium concentration (40 mM)[K+]i is the intracellular potassium concentration (350 mM)Plugging in these values, we get:E = (8.314 J/mol*K * 310K) / (1 * 96,485 C/mol) * ln(40 mM / 350 mM)E = -58.4 mVTherefore, the equilibrium potential for potassium is -58.4 mV.

Question 17

Which of the following ions is most likely to cross the plasma membrane of a resting neuron? A) K⁺ B) Na⁺ C) Ca²⁺ D) Cl^-

Accepted Answer

K⁺ is the ion that is most likely to cross the plasma membrane of a resting neuron because it is positively charged and is attracted to the negatively charged interior of the cell. Additionally, the resting membrane potential of neurons is predominantly determined by the concentration gradient of K⁺ ions, meaning that K⁺ is always more concentrated inside the cell than outside, which creates a driving force for the ion to move out of the cell. Na⁺ and Ca2+ ions are also positively charged, but they are less likely to cross the plasma membrane of a resting neuron because they are less concentrated inside the cell and because the membrane has lower permeability to these ions. Cl- ions are negatively charged and are repelled by the negatively charged interior of the cell, making them less likely to cross the membrane.

Question 18

The Nernst equation specifies the equilibrium potential for a particular ion. This equilibrium potential is a function of ________.
A) hydrostatic pressure
B) ion concentration gradient
C) osmotic gradient
D) temperature (thermal) gradient

Accepted Answer

The equilibrium potential specified by the Nernst equation is a function of the ion concentration gradient. All other options - hydrostatic pressure, osmotic gradient, and temperature gradient - are not relevant to the Nernst equation.

Question 19

In a simple synapse, neurotransmitter chemicals are received by ________.
A) the presynaptic membrane
B) dendrites
C) axon hillocks
D) cell bodies

Accepted Answer

Neurotransmitter chemicals are received by dendrites in a simple synapse.

Question 20

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?
A) The membrane potential would become more negative.
B) The membrane potential would become more positive.
C) The membrane potential would be unaffected.
D) The answer depends on the thermodynamic potential.

Accepted Answer

Increasing the concentration of Na⁺ outside a cell while maintaining other ion concentrations constant would lead to an increase in the concentration gradient of Na⁺ across the cell membrane. Na⁺ is a positively charged ion, so the increase in its concentration outside the cell would drive it into the cell, making the inside of the cell more positive. This would cause the membrane potential to become more positive.

Quiz 48: Neurons, Synapses, and Signalling

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 ________.

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 ________.

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

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

The operation of the sodium-potassium pump moves ________.

The three stages of information processing in animals include ________.

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

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

Refer to the following graph of an action potential to answer the question. The membrane's permeability to sodium ions is greatest at label ________.

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 ________.

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

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

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

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

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

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

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

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?