NP Resting Neuronal and Membrane Potential

What is neuronal membrane potential?

Neuronal Membrane Potential: The voltage difference across a neuron's membrane (between intracellular and extracellular fluid voltage) at rest, typically around -65 mV, critical for neuronal signaling. It is changed by information arriving at the neuron or inputs or the movememt of ions across the membrane.

What happens to salts when dissolved in solution?

Salts Dissociate into Constituent Ions: When dissolved in solution, salts separate into individual ions, essential for conducting electricity in neurons.

What is the purpose of the cell membrane in terms of ions?

Cell Membranes as Ion Barriers: The lipid bilayer of the cell membrane prevents the free movement of ions, maintaining ion separation between intracellular and extracellular spaces. However, ions can interact across the neuronal membrane (capacitance). In resting nerve cells, the membrane is quite permeable to potassium.

What are ionic concentration differences, how are the created and why are they important?

Ionic Concentration Differences: Varying concentrations of ions (e.g., Na+, K+, Ca2+) exist inside and outside of neurons, creating the conditions necessary for action potentials. Ion concentrations are maintained by active (ion transporters) and passive (ion exchangers) transport mechanisms, using energy to create gradients.

What are the two ion movement principles?

Ions move under concentration and electrical gradients. These principles explain how ions diffuse from areas of higher concentration to lower concentration and how they move along electrical gradients creating a current, both contributing to neuronal excitability.

What do ionic concentration gradients create?

The disparities in ion concentrations store potential energy that drives neuronal signaling processes.

What is the purpose of ion channels?

Specialized proteins (ion channels) allow ions to cross the membrane in response to specific signals, crucial for action potentials and synaptic transmission.

Describe how ion channels can be opened and closed and discuss different kinds of gating.

Gating of Ion Channels. Channel states can change (open/closed) based on stimuli, which can be voltage changes, chemical (ligand) binding, or mechanical stress. Gating is when the stimuli causes a conformational change in the channel, hinging to allow the movement of ions across the channel along their electrical and concentration gradients.

• Voltage-gated: Open in response to membrane potential changes.

• Ligand-gated: Open in response to binding of neurotransmitters.

• Mechanically-gated: Open in response to physical changes.

Discuss ion selectivity and it’s importance.

Ion Selectivity: Ion channels can be highly selective for specific ions. Channels often prefer particular ions, allowing for controlled signaling in response to specific physiological conditions.

• The selective movement of ions is created by a selectivity pore (more particularly the exact alignment of the amino acids with the oxygen of the partially hydrated ion) in the channel that filters the particular molecule through

• The position of the oxygen ion is different for different ions, thus this exact alignment of oxygen to amino acids allows for ion selectivity through the channel

Discuss diversity of ion channel families and what this means.

Diversity of Ion Channel Families: Multiple ion channel types exist, each with unique properties that enable complex neuronal function and contribute to various neuronal functions and signaling pathways.

What is the impact of selective ion permeability?

Different ions contribute to the resting membrane potential and action potentials, with selectivity shaping the overall electrical behavior of a neuron.

What is equilibrium potential and what is its role in determining the resting membrane potential?

Equilibrium Potential: This is the membrane potential where the concentration and electrical gradients for a specific ion balance out (and there is NO NET movement of an ion), influencing the resting voltage of the neuron. It represents the voltage at which the ion's flow across the membrane is zero, crucial for maintaining the resting membrane potential.

• It doesn't mean that the concentrations are equal it means the NET movement is equal as both concentration and electrical gradients influence membrane potential

Discuss the Goldman and Nernst equations

Mathematical models (Goldman for multiple ions, Nernst for a single ion) used to calculate ion gradients and predict resting and equilibrium potentials, aiding in understanding neuronal function.

What is depolarization and hyperpolarization?

Depolarization refers to a decrease in the electrical potential difference or membrane potential of a cell, making it less negative or more positive and occurring from an excitatory input.

Hyperpolarization refers to an increase in the membrane potential difference, or making it more negative usually due to inhibitory input.

Describe the general trends of the ion concentrations of sodium, potassium, chloride and calcium ions?

Sodium ions (Na+) are typically more concentrated outside the cell, while potassium ions (K+) are more concentrated inside. Chloride concentration changes based on the maturation of neurons or depending on various circumstances, but generally are more concentrated outside the cell. Calcium ions (Ca2+) are also more concentrated outside the cell, contributing to various cellular processes.

What are Ion transporters and Ion Exchangers with an example.

Ion Transporters (pumps) use energy to move ions against concentration gradients e.g. Sodium potassium pump which transport sodium out of and potassium into the cell. They are important as they establish ion concentration gradients across the neuronal membrane, vital for maintaining resting potential.

Ion Exchangers use energy stored in ion concentration gradients to transport ions. e.g. Sodium calcium exchanger where energy stored as one molecule (Na+) travels along it's concentration gradient allows another molecule (Ca2+) to move against it's concentration gradient. These can also transport other molecules other than ions such as neurotransmitter

These concentration gradients create the basis on which the neuron can function

Why is membrane potential important for neuronal function and what influences neuronal firing?

Membrane potential is crucial for neuronal communication, as it determines whether a neuron will reach the threshold to fire an action potential.

• If we can change membrane potential enough (through concentration and electrical gradients), an action potential will fire

• Excitatory postsynaptic potentials (EPSP) increase the likelihood of an action potential, while inhibitory postsynaptic potentials (IPSP) decrease it.

• Summation of these potentials across dendrites and axon influences neuronal firing.