MCAT resting membrane potential key terms

What is resting membrane potential?

The voltage across the neuronal membrane when it is not actively sending signals, typically around -70 mV.

True or False: Resting membrane potential is always positive.

False. It is typically negative, indicating the inside of the cell is more negative compared to the outside.

Which ions primarily influence resting membrane potential?

Potassium (K+) and Sodium (Na+) are the primary ions.

Fill in the blank: The resting membrane potential is primarily established by the __________ of potassium ions.

diffusion out.

Cause → Effect: Increased permeability to K+ leads to...?

Hyperpolarization, making the inside of the cell more negative.

How do Na+/K+ pumps contribute?

They maintain resting membrane potential by pumping 3 Na+ out and 2 K+ in, creating a net negative charge inside.

What role does the lipid bilayer play?

It acts as a barrier, preventing free movement of ions and maintaining potential differences.

Comparison: Resting membrane potential vs. Action potential.

Resting membrane potential is stable (-70 mV), while action potential is a temporary reversal of this potential.

What happens during depolarization?

The membrane potential becomes less negative, moving towards zero and potentially becoming positive.

Short example: How is resting potential measured?

Using microelectrodes to compare the inside and outside of a neuron.

True or False: Resting membrane potential can change dramatically with stimulation.

True. It can change significantly during action potentials.

Define equilibrium potential.

The membrane potential at which there is no net movement of a particular ion across the membrane.

What is the typical value of resting membrane potential?

Around -70 mV, varying slightly between cell types.

Which cell types have resting membrane potentials?

Neurons, muscle cells, and some endocrine cells.

What maintains the concentration gradient of Na+ and K+?

Active transport via Na+/K+ ATPase pumps.

Fill in the blank: At rest, the permeability of the membrane is much greater for __________ than for sodium.

potassium.

What is the role of potassium channels?

Potassium channels allow K+ to flow out of the cell, contributing to hyperpolarization and resting membrane potential.

True or False: Sodium channels maintain resting membrane potential.

False. Sodium channels primarily depolarize the membrane during action potentials, not resting potential.

Fill in the blank: The primary ion contributing to resting potential is _____.

Potassium (K+)

What do leak channels do?

Leak channels allow ions like Na+ and K+ to passively move across the membrane, helping stabilize resting potential.

Compare Na+/K+ pump and ion channels.

Na+/K+ pump uses ATP to move 3 Na+ out and 2 K+ in, while ion channels allow passive ion flow.

What is the significance of chloride channels?

Chloride channels help to stabilize resting potential by allowing Cl- ions into the cell, influencing excitability.

Cause → Effect: Opening of K+ channels leads to _____.

Hyperpolarization of the membrane.

What is the purpose of the Na+/K+ ATPase?

It maintains the concentration gradients of Na+ and K+ across the membrane, essential for resting potential.

True or False: All cells have the same resting membrane potential.

False. Resting membrane potential varies by cell type due to different ion channel distributions.

What do voltage-gated ion channels respond to?

They respond to changes in membrane potential, opening or closing in response to depolarization or hyperpolarization.

Example: Calculate resting membrane potential using Nernst equation for K+.

$\displaystyle E_K = 61.5 imes ext{log} \frac{[K^+]_{outside}}{[K^+]_{inside}}$

What is the effect of increasing extracellular K+ concentration?

It can depolarize the cell, raising the resting membrane potential closer to 0 mV.

Fill in the blank: Resting membrane potential is typically around _____ mV.

-70 mV

How do calcium channels influence resting potential?

Calcium channels can depolarize the membrane when opened, affecting excitability but are not primary in maintaining resting potential.

What is the primary ion that creates the negative resting potential?

Potassium (K+) creates a negative potential due to its higher permeability at rest.

True or False: Resting membrane potential is solely determined by Na+ concentrations.

False. It is predominantly influenced by K+ due to its permeability and leak channels.

What happens if Na+ channels open at resting potential?

The cell becomes depolarized, moving toward a more positive membrane potential.

What is the function of anion channels?

Anion channels allow negatively charged ions to enter or exit, influencing membrane potential.

Cause → Effect: Closing of Na+ channels leads to _____.

Repolarization of the membrane.

What role do transporters play in resting potential?

Transporters, like the Na+/K+ ATPase, maintain ion gradients essential for establishing resting membrane potential.

What does the Nernst Equation calculate?

The equilibrium potential for a specific ion based on its concentration gradient and charge.

Nernst Equation formula?

$\displaystyle E_{ion} = \frac{RT}{zF} imes ext{ln} \frac{[ion]_{outside}}{[ion]_{inside}}$

True or False: The Goldman Equation considers multiple ions.

True - It accounts for the permeability of different ions to calculate the resting membrane potential.

Fill in the blank: The Goldman Equation incorporates ____ of ions.

permeability coefficients.

Write the Goldman Equation.

$\displaystyle E_{m} = 61.5 imes ext{log} \frac{P_{K}[K^+]_{outside} + P_{Na}[Na^+]_{outside}}{P_{K}[K^+]_{inside} + P_{Na}[Na^+]_{inside}}$

What is the significance of the Nernst Equation?

It predicts the voltage at which an ion is at equilibrium across a membrane.

Compare Nernst and Goldman Equations.

- Nernst: single ion - Goldman: multiple ions and permeability

Cause → Effect: High permeability for K+ leads to?

A negative resting membrane potential, as K+ will flow out of the cell.

What happens if ion concentrations change?

Equilibrium potentials calculated by Nernst Equation will shift, affecting overall membrane potential.

True or False: The Nernst Equation can be used for any ion.

True - It can be applied to any ion with known concentrations inside and outside the cell.

Example: Calculate K+ equilibrium potential with 140 mM outside and 4 mM inside.

$\displaystyle E_{K} = 61.5 imes ext{log} \frac{140}{4} = +90 mV$

What factors affect membrane potential?

- Ion concentrations - Ion permeability - Temperature

Why is resting membrane potential important in neurons?

It allows for the generation of action potentials, essential for nerve impulse transmission.

True or False: Resting membrane potential is the same in all cells.

False. Different cell types have varying resting membrane potentials due to ion channel distribution.

Compare resting membrane potential in neurons and muscle cells.

Both are typically around -70 mV, but muscle cells have a faster response to stimuli.

Fill in the blank: The resting membrane potential is primarily determined by ____ permeability.

potassium (K+)

How does the Na+/K+ pump maintain resting membrane potential?

It pumps 3 Na+ out and 2 K+ in, creating a net negative charge inside.

What effect does depolarization have on resting membrane potential?

It makes the inside of the cell more positive, moving towards threshold potential.

What is the typical value of resting membrane potential in neurons?

-70 mV to -90 mV, often around -70 mV.

Cause → Effect: Increased K+ permeability leads to?

Hyperpolarization of the cell membrane.

What role do leak channels play in resting membrane potential?

They allow ions to flow passively, mainly K+, contributing to negative charge.

True or False: Resting membrane potential can change under pathological conditions.

True. Conditions like ischemia can alter ion concentrations, affecting membrane potential.

What happens to the resting membrane potential when chloride ions enter a cell?

It may become more negative, leading to hyperpolarization.

Explain the physiological role of resting membrane potential in cardiac muscle.

It helps regulate heartbeats and ensures coordinated contractions of heart muscle.

What happens during repolarization?

K+ channels open, allowing K+ to exit, returning the membrane potential towards resting state.

How does resting membrane potential affect synaptic transmission?

It establishes the baseline to trigger neurotransmitter release upon reaching threshold.

What is the impact of reduced extracellular Na+ on resting membrane potential?

It can cause the resting membrane potential to become more negative.

How does resting membrane potential relate to muscle contractions?

It sets the stage for action potentials, crucial for initiating muscle contractions.