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20. does the action potential travel down the axon all at once or littl…

Question

  1. does the action potential travel down the axon all at once or little by little?
  2. true or false: the action potential passes from one neuron to the next.

steps of action potential

  1. which are the 4 stages of action potential in order?
  2. when a neuron is not sending any message, what stage is the neuron in?
  3. during resting potential, what is the charge inside the axon?
  4. during resting potential, what is the charge outside the axon?
  5. during resting potential, which pumps/channels are open?
  6. describe the concentration of k+ ions during resting potential.
  7. during resting potential is there a concentration gradient of k+ ions?
  8. describe the concentration of na+ ions during resting potential.
  9. during resting potential is there a concentration gradient of na+ ions?

Explanation:

Brief Explanations
Question 20:

Action potential travels down the axon little by little (through a process of local depolarization and repolarization that propagates, with each segment of the axon depolarizing in sequence, not all at once).

Question 21:

False. Action potential does not pass directly from one neuron to the next. Instead, it is transmitted via neurotransmitters across the synapse (the gap between neurons). The action potential reaches the axon terminal of the presynaptic neuron, triggering the release of neurotransmitters that then bind to receptors on the postsynaptic neuron, potentially initiating a new action potential there, but it is not a direct passing of the action potential.

Question 1 (Steps of Action Potential - 4 stages):

The four stages of action potential in order are: 1) Resting Potential, 2) Depolarization, 3) Repolarization, 4) Hyperpolarization (and then back to resting potential, but the four main stages in the sequence of the action potential event are resting, depolarization, repolarization, hyperpolarization).

Question 2:

When a neuron is not sending any message, it is in the Resting Potential stage. During resting potential, the neuron is at its resting membrane potential, with the inside of the axon being negatively charged relative to the outside, and ion channels/pumps maintaining the ion concentrations (like the sodium - potassium pump and leaky potassium channels) to keep this resting state until a stimulus causes a change.

Question 3:

During resting potential, the charge inside the axon is negative (typically around - 70 mV relative to the outside). This negative charge is mainly due to the presence of large anionic (negative) proteins inside the cell and the differential distribution of ions (more $K^+$ inside but also the negative - charged proteins, and more $Na^+$ outside).

Question 4:

During resting potential, the charge outside the axon is positive (relative to the inside). This is because there is a higher concentration of sodium ions ($Na^+$) outside the axon compared to the inside, and also other positive ions contribute to the positive charge outside.

Question 5:

During resting potential, the sodium - potassium pumps (which actively transport 3 $Na^+$ out of the cell and 2 $K^+$ into the cell) and leaky potassium channels (which allow $K^+$ to diffuse out of the cell down its concentration gradient) are open. The leaky potassium channels are more permeable at rest, while the sodium channels (voltage - gated sodium channels) are closed during resting potential.

Question 6:

During resting potential, the concentration of $K^+$ ions is higher inside the axon (intracellular fluid) than outside (extracellular fluid). The sodium - potassium pump helps maintain this concentration gradient, and the leaky potassium channels allow some $K^+$ to diffuse out, but the overall concentration inside remains higher.

Question 7:

Yes, during resting potential, there is a concentration gradient of $K^+$ ions. The concentration of $K^+$ is higher inside the axon than outside, so there is a concentration gradient that drives the diffusion of $K^+$ out of the cell through the leaky potassium channels (until the electrical gradient counteracts the concentration gradient at the resting membrane potential).

Question 8:

During resting potential, the concentration of $Na^+$ ions is higher outside the axon (extracellular fluid) than inside (intracellular fluid). The sodium - potassium pump actively transports $Na^+$ out of the cell, and the voltage - ga…

Answer:

Question 20:

The action potential travels down the axon little by little.

Question 21:

False

Question 1:

Resting Potential, Depolarization, Repolarization, Hyperpolarization

Question 2:

Resting Potential

Question 3:

Negative (typically around - 70 mV relative to outside)

Question 4:

Positive (relative to inside)

Question 5:

Sodium - potassium pumps and leaky potassium channels

Question 6:

Higher inside the axon than outside

Question 7:

Yes

Question 8:

Higher outside the axon than inside

Question 9:

Yes