Question 1

How do temporal and spatial summation improve the processing power of the brain?

Accepted Answer

Temporal summation allows a neuron to recognize a persistent signal from a single presynaptic cell, and spatial summation allows a neuron to recognize a broad signal from multiple presynaptic cells.

Question 2

Sodium ions are single atoms.Why can't they simply diffuse through the cell membrane's lipid bilayer?

Accepted Answer

Since sodium ions are charged, they cannot easily cross the hydrophobic center of the membrane without a channel or pump. The lipid bilayer is hydrophobic, meaning it repels charged particles like ions. Therefore, sodium ions require specialized channels or pumps to cross the membrane.

Question 3

What does the Nernst equation allow us to do?

Accepted Answer

The Nernst equation allows us to calculate the equilibrium potential for an ion.

Question 4

If sympathetic and parasympathetic neurons both release acetylcholine (ACh),how can they have antagonistic effects? (Check all that apply.)

Accepted Answer

Even though both sympathetic and parasympathetic neurons release ACh, the target cells of each set of neurons respond differently to the same signal. For example, sympathetic neurons release ACh that binds to nicotinic receptors on the chromaffin cells in the adrenal medulla, causing them to secrete epinephrine and norepinephrine, while parasympathetic neurons release ACh that binds to muscarinic receptors on target cells. Additionally, sympathetic neurons also activate the adrenal gland, causing secretion of epinephrine, which can have antagonistic effects compared to the actions of the parasympathetic nervous system.

Question 5

Another toxin that also blocks neurotransmitter release is tetanus toxin; however,it primarily affects inhibitory interneurons of the spinal cord that negatively regulate motor neurons.Which would be symptoms of tetanus toxin poisoning?

Accepted Answer

Tetanus toxin primarily affects inhibitory interneurons, leading to an excessive activation of motor neurons and muscle spasms, which is characteristic of spastic paralysis. Flaccid paralysis is generally caused by toxins that primarily affect motor neurons themselves, such as botulinum toxin. Slowed action potential conduction and pupil dilation are not typical symptoms of tetanus toxin poisoning.

Question 6

In contrast to these toxins,strychnine acts postsynaptically,to block glycine from binding to receptors on motor neurons.Would you expect the symptoms of strychnine poisoning to be more similar to those of botulinum or tetanus toxin?

Accepted Answer

Since strychnine acts postsynaptically to block glycine from binding to receptors on motor neurons, this suggests an increase in motor neuron excitability. This is similar to tetanus toxin, which also causes increased excitability of motor neurons, leading to muscular spasms and eventually paralysis. Botulinum toxin, on the other hand, blocks the release of acetylcholine from presynaptic neurons, leading to muscle weakness and paralysis. Therefore, the symptoms of strychnine poisoning are more similar to those of tetanus toxin, rather than botulinum toxin.

Question 7

What limits the frequency of action potentials?

Accepted Answer

The refractory period limits the frequency of action potentials by causing a brief period of time during which the neuron cannot generate a new action potential, as it needs time to reset its ion channels. Thus, the refractory period sets a limit on how quickly the neuron can fire.

Question 8

Why are mammalian reflexes so fast? (Check all that apply.)

Accepted Answer

Mammalian reflexes are fast because they involve a simple circuit with only a few neurons (B), they often bypass the brain to reduce processing time (C), and there was evolutionary pressure to develop quick responses to certain stimuli for survival (E).

Question 9

K⁺ channels in the heart do not have binding sites for ACh,yet parasympathetic release of ACh causes outward flux of K⁺ from heart cells.How does this occur?

Accepted Answer

ACh binds to a G-protein coupled receptor on heart cells, activating the G protein alpha subunit, which then binds to a separate K⁺ channel and causes it to open. This allows for the outward flux of K⁺ from heart cells, despite the fact that the channels themselves do not have binding sites for ACh.

Question 10

When an action potential begins and sodium channels open,why does sodium rush into the cell? (Check all that apply.)

Accepted Answer

A) The inside of the cell is negatively charged, creating an electrochemical gradient that attracts the positively charged sodium ions. D) The diffusion gradient, where sodium ions move from an area of high concentration (outside the cell) to an area of low concentration (inside the cell), also drives sodium into the cell.

Question 11

Since there is a larger concentration of potassium ions inside a neuron,why is the inside of the neuron negative (-70mV)relative to the outside?

Accepted Answer

While potassium ions do carry a positive charge, the inside of the cell is negative relative to the outside due to the presence of negatively charged proteins inside the cell that counteract the positive charge of the potassium ions. This results in an overall negative charge inside the neuron. The high concentration of sodium ions outside the cell does play a role in generating this charge, but it is not the primary reason for the negative charge inside the cell. The negative sign is not just a historical convention, as it reflects the overall charge of the neuron relative to its environment.

Question 12

A patient of yours is injured in a car accident.The surgeon reports that while there is damage to the dorsal roots,the spinal cord and nerves otherwise appear intact.What functions would you expect to be affected in the patient?

Accepted Answer

Damage to the dorsal roots may result in loss of some sensory perception, and lack of proprioceptive input may make muscle control difficult. However, since the spinal cord and nerves otherwise appear intact, the patient should retain motor function. Autonomic function is not directly affected by damage to dorsal roots. The parasympathetic and sympathetic nervous systems are both part of the autonomic nervous system and damage to dorsal roots would not selectively affect only one branch. Therefore, choices A and D are not accurate. Choice B is also not accurate because while the patient may experience some loss of motor function, they should not necessarily retain sensory perception completely.

Question 13

What would happen if the G-protein coupled receptor in heart cells that binds to ACh had a mutation that caused it to bind more tightly to the G-protein alpha subunit?

Accepted Answer

The answer of What would happen if the G-protein coupled...

Question 14

The outside of a neuron is positively charged at resting potential.Why don't negative ions exit from the cell to normalize charge across the membrane?

Accepted Answer

The negative charge inside the cell is carried by large proteins that cannot diffuse through the membrane, so they are unable to exit the cell and restore the balance of charges across the membrane.

Question 15

What is the basis of the typical -70mV resting potential in neurons? Rank the factors in order from most important to least important. 1.Na⁺ equilibrium potential 2.Ca⁺² equilibrium potential 3.K⁺ equilibrium potential

Accepted Answer

The answer of What is the basis of the typical...

Question 16

The outside of a neuron is positively charged at resting potential.Why do K⁺ ions leave the cell when K⁺ channels open during an action potential?

Accepted Answer

Voltage-gated K+ channels open when membrane potential reaches +50 mV during the depolarization phase. The diffusion gradient and electrical force cooperate to drive K+ ions out of the cell. This is called repolarization, and it returns the neuron to its resting potential state.

Question 17

How do somatic neurons and autonomic neurons differ? (Check all that apply.)

Accepted Answer

The answer of How do somatic neurons and autonomic neurons...

Question 18

If K⁺ can exit the cell through leak channels,why don't they flow out until there are equal concentrations on both sides of the membrane?

Accepted Answer

The negative electrical potential inside the cell creates a force that holds the K⁺ ions in. This is known as electrostatic force, which opposes the concentration-based gradient that would otherwise cause the ions to flow out of the cell. Therefore, even though there may be a concentration gradient favoring the movement of K⁺ ions out of the cell through leak channels, the electrostatic force keeps most of the ions inside the cell.

Quiz 42: The Nervous System

How do temporal and spatial summation improve the processing power of the brain?

Sodium ions are single atoms.Why can't they simply diffuse through the cell membrane's lipid bilayer?

What does the Nernst equation allow us to do?

If sympathetic and parasympathetic neurons both release acetylcholine (ACh) ,how can they have antagonistic effects? (Check all that apply.)

Another toxin that also blocks neurotransmitter release is tetanus toxin; however,it primarily affects inhibitory interneurons of the spinal cord that negatively regulate motor neurons.Which would be symptoms of tetanus toxin poisoning?

In contrast to these toxins,strychnine acts postsynaptically,to block glycine from binding to receptors on motor neurons.Would you expect the symptoms of strychnine poisoning to be more similar to those of botulinum or tetanus toxin?

What limits the frequency of action potentials?

Why are mammalian reflexes so fast? (Check all that apply.)

K⁺ channels in the heart do not have binding sites for ACh,yet parasympathetic release of ACh causes outward flux of K⁺ from heart cells.How does this occur?

When an action potential begins and sodium channels open,why does sodium rush into the cell? (Check all that apply.)

Since there is a larger concentration of potassium ions inside a neuron,why is the inside of the neuron negative (-70mV) relative to the outside?

A patient of yours is injured in a car accident.The surgeon reports that while there is damage to the dorsal roots,the spinal cord and nerves otherwise appear intact.What functions would you expect to be affected in the patient?

What would happen if the G-protein coupled receptor in heart cells that binds to ACh had a mutation that caused it to bind more tightly to the G-protein alpha subunit?

The outside of a neuron is positively charged at resting potential.Why don't negative ions exit from the cell to normalize charge across the membrane?

What is the basis of the typical -70mV resting potential in neurons? Rank the factors in order from most important to least important. 1.Na⁺ equilibrium potential 2.Ca⁺² equilibrium potential 3.K⁺ equilibrium potential

The outside of a neuron is positively charged at resting potential.Why do K⁺ ions leave the cell when K⁺ channels open during an action potential?

How do somatic neurons and autonomic neurons differ? (Check all that apply.)

If K⁺ can exit the cell through leak channels,why don't they flow out until there are equal concentrations on both sides of the membrane?

Quiz 42: The Nervous System

How do temporal and spatial summation improve the processing power of the brain?

Sodium ions are single atoms.Why can't they simply diffuse through the cell membrane's lipid bilayer?

What does the Nernst equation allow us to do?

If sympathetic and parasympathetic neurons both release acetylcholine (ACh) ,how can they have antagonistic effects? (Check all that apply.)

Another toxin that also blocks neurotransmitter release is tetanus toxin; however,it primarily affects inhibitory interneurons of the spinal cord that negatively regulate motor neurons.Which would be symptoms of tetanus toxin poisoning?

In contrast to these toxins,strychnine acts postsynaptically,to block glycine from binding to receptors on motor neurons.Would you expect the symptoms of strychnine poisoning to be more similar to those of botulinum or tetanus toxin?

What limits the frequency of action potentials?

Why are mammalian reflexes so fast? (Check all that apply.)

K+ channels in the heart do not have binding sites for ACh,yet parasympathetic release of ACh causes outward flux of K+ from heart cells.How does this occur?

When an action potential begins and sodium channels open,why does sodium rush into the cell? (Check all that apply.)

Since there is a larger concentration of potassium ions inside a neuron,why is the inside of the neuron negative (-70mV) relative to the outside?

A patient of yours is injured in a car accident.The surgeon reports that while there is damage to the dorsal roots,the spinal cord and nerves otherwise appear intact.What functions would you expect to be affected in the patient?

What would happen if the G-protein coupled receptor in heart cells that binds to ACh had a mutation that caused it to bind more tightly to the G-protein alpha subunit?

The outside of a neuron is positively charged at resting potential.Why don't negative ions exit from the cell to normalize charge across the membrane?

What is the basis of the typical -70mV resting potential in neurons? Rank the factors in order from most important to least important. 1.Na+ equilibrium potential 2.Ca+2 equilibrium potential 3.K+ equilibrium potential

The outside of a neuron is positively charged at resting potential.Why do K+ ions leave the cell when K+ channels open during an action potential?

How do somatic neurons and autonomic neurons differ? (Check all that apply.)

If K+ can exit the cell through leak channels,why don't they flow out until there are equal concentrations on both sides of the membrane?

K⁺ channels in the heart do not have binding sites for ACh,yet parasympathetic release of ACh causes outward flux of K⁺ from heart cells.How does this occur?

What is the basis of the typical -70mV resting potential in neurons? Rank the factors in order from most important to least important. 1.Na⁺ equilibrium potential 2.Ca⁺² equilibrium potential 3.K⁺ equilibrium potential

The outside of a neuron is positively charged at resting potential.Why do K⁺ ions leave the cell when K⁺ channels open during an action potential?

If K⁺ can exit the cell through leak channels,why don't they flow out until there are equal concentrations on both sides of the membrane?