Neuroscience Overview: Glial Cells & Membrane Potential

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Questions and Answers

What primarily triggers the influx of Na+ during the rising phase of an action potential?

Gated K+ channels opening

Large driving force causing Na+ to rush into the cell (correct)

Inactivation of Ca2+ channels

Hyperpolarization of the cell

What occurs during the falling phase of an action potential?

The intercellular voltage becomes more positive

K+ channels open, allowing K+ to flow out of the cell (correct)

Na+ continues to rush into the cell

The cell remains depolarized

What is the effect of Na+ rushing into the cell on its membrane potential during the rising phase?

It causes hyperpolarization of the cell

It has no effect on membrane potential

It makes the inside of the cell more positive (correct)

It stabilizes the resting membrane potential

What value does the membrane potential approach during the peak of depolarization?

+40 mV Signup and view all the answers

What initiates the inactivation of Na+ channels during the action potential?

Repolarization of the membrane Signup and view all the answers

What causes the depolarization of a neuron to reach the threshold?

Increased sodium ion permeability due to open sodium channels Signup and view all the answers

Which statement describes the role of sodium channels in the action potential?

Sodium channels facilitate a positive feedback loop during depolarization Signup and view all the answers

What event occurs after sodium channels open and sodium rushes into the cell?

Potassium channels open and potassium ions leave the cell Signup and view all the answers

Why is a threshold voltage important in the generation of an action potential?

It triggers the opening of sufficient sodium channels Signup and view all the answers

What is the primary effect of increased sodium permeability during a neuron’s depolarization phase?

The membrane potential becomes more positive Signup and view all the answers

What happens to the neuron's membrane potential during repolarization?

The membrane potential returns to resting level Signup and view all the answers

What triggers the opening of potassium channels during the action potential process?

The rapid depolarization phase due to sodium influx Signup and view all the answers

What is the consequence of a cell becoming depolarized?

The likelihood of firing an action potential increases Signup and view all the answers

What is the primary characteristic of Gray's Type I synapses?

They are excitatory and have round vesicles. Signup and view all the answers

Which type of receptors are primarily associated with EPSPs?

Nicotinic ACh receptors. Signup and view all the answers

What occurs immediately after the presynaptic membrane depolarizes and reaches threshold?

Action potentials are generated. Signup and view all the answers

What are the two major functions of receptors?

Recognize ligands and activate effector proteins. Signup and view all the answers

Which statement is true regarding ionotropic receptors?

They contain multiple subunits that form a ligand-binding site and ion channel. Signup and view all the answers

What is an example of an inhibitory neurotransmitter that may lead to an IPSP?

GABA. Signup and view all the answers

Which feature distinguishes Gray's Type II synapses?

They mainly form inhibitory connections with flat vesicles. Signup and view all the answers

Which type of potential is primarily generated by ligand-gated ionotropic receptors?

Post-synaptic potentials. Signup and view all the answers

What is the primary function of microglia in the central nervous system?

Phagocytose cellular debris Signup and view all the answers

Which glial cell type is responsible for forming the blood-brain barrier?

Astrocytes Signup and view all the answers

What ion primarily contributes to repolarization during an action potential?

K+ (Potassium) Signup and view all the answers

Which equation relates the concentration of ions outside and inside the cell to the membrane potential?

Nernst Equation Signup and view all the answers

What does a membrane potential of -70 mV indicate?

The cell is at resting potential Signup and view all the answers

What is the main role of oligodendrocytes in the central nervous system?

Myelinate CNS axons Signup and view all the answers

What drives the ion flow until equilibrium is reached according to the Nernst Equation?

Concentration gradient Signup and view all the answers

What characteristic of a membrane does the Goldman Equation take into account?

Selective permeability to multiple ions Signup and view all the answers

What is hyperpolarization in the context of membrane potential?

Decrease in membrane potential making it more negative Signup and view all the answers

What force opposes the concentration gradient for ions during membrane potential changes?

Electrical attraction Signup and view all the answers

Which type of cell in the peripheral nervous system myelinates neurons?

Schwann cells Signup and view all the answers

What does Ohm's Law relate to in the context of neuronal function?

Current, resistance, and voltage Signup and view all the answers

What potential difference exists across the resting membrane of most neurons?

Around -60 to -70 mV Signup and view all the answers

What ion is more concentrated outside of a resting neuron compared to inside?

Na+ (Sodium) Signup and view all the answers

What effect does depolarization have on a neuron's membrane potential?

It makes the membrane potential more positive. Signup and view all the answers

What role do voltage-gated channels play in neuronal function?

They allow ions to flow based on membrane potential. Signup and view all the answers

What is the primary function of the Sodium-Potassium pump?

To exchange sodium for potassium against their concentration gradients. Signup and view all the answers

What does hyperpolarization refer to in neuronal activity?

The membrane potential becomes more negative. Signup and view all the answers

What type of ion is primarily involved in depolarization?

Sodium ions (Na+). Signup and view all the answers

What effect does TTX have on neuronal activity?

It blocks sodium currents. Signup and view all the answers

Which ionic condition describes the term 'cation'?

An ion with a positive charge. Signup and view all the answers

What does permeability refer to in the context of ion channels?

The ability of ions to move freely across barriers. Signup and view all the answers

What is the effect of TEA on neuronal currents?

It blocks potassium currents. Signup and view all the answers

How does the concept of 'current' relate to ion movement in neurons?

Current indicates the flow of ions across a membrane. Signup and view all the answers

What happens to membrane potential during the influx of sodium ions?

It increases. Signup and view all the answers

Which of the following statements about ion gradients is true?

Ion gradients are maintained by ATP consumption. Signup and view all the answers

What occurs during the depolarization phase of an action potential?

Voltage-gated Na+ channels open, leading to Na+ influx. Signup and view all the answers

What role does ATP play in the function of the Sodium-Potassium pump?

It provides energy for the active transport of ions. Signup and view all the answers

Study Notes

Glial Cells

Microglia are immune cells that phagocytize (engulf and digest) foreign invaders and cellular debris in the central nervous system (CNS).
Ependymal cells line the ventricles of the brain and the central canal of the spinal cord.
Oligodendrocytes are responsible for creating the myelin sheath, which insulates axons in the CNS and aids in signal transmission.
Astrocytes are star-shaped cells that provide structural support and maintain the blood-brain barrier, limiting potassium (K+) movement. They fill most of the space between neurons in the brain.
Schwann cells myelinate axons in the peripheral nervous system (PNS).

Membrane Potential

The membrane potential (Vm) is the difference in electrical potential across the cell membrane.
Vm depends on ion concentration gradients and the selective permeability of the membrane.
At rest, neurons typically have a Vm of around -65 to -70 mV, which is considered hyperpolarized.
This resting potential exists due to the differences in ion concentrations across the membrane – sodium ions (Na+) have a higher concentration outside the cell, while potassium ions (K+) have a higher concentration inside the cell.
Forces driving ion movement include:
- Chemical diffusion: Ions move down their concentration gradients, from areas of high concentration to low concentration.
- Electrical opposition: Ions move to areas with opposite charges.
Conductance (g) represents how easily ions can move across the membrane. Ohm's Law (V = IR) relates membrane potential (V), current (I), and resistance (R), which is the inverse of conductance.
Driving force refers to the difference between the membrane potential (Um) and the ion's equilibrium potential (Eion), which is the potential at which there is no net ion movement.
Nernst Equation calculates the equilibrium potential (Eion) for a specific ion. It considers the charge of the ion, the concentrations of the ion inside and outside the cell, and the ideal gas constant.
Goldman Equation calculates the membrane potential (Um) considering the permeability of the membrane to multiple ions, including potassium (K+), sodium (Na+), and chloride (Cl-).
Depolarization: The membrane potential becomes less negative, moving towards zero.
Hyperpolarization: The membrane potential becomes more negative, moving further away from zero.
Current: The flow of ions across the membrane. Inward current causes depolarization, while outward current causes hyperpolarization.
Permeability: How easily ions can cross the membrane.
Voltage-gated channels: Open and close in response to changes in membrane potential.

Sodium-Potassium Pump

The sodium-potassium pump uses ATP to actively transport 3 Na+ ions out of the cell and 2 K+ ions into the cell.
This exchange works against the concentration gradients of both ions, maintaining the resting membrane potential.
The pump contributes to the neuron's ability to depolarize and repolarize.

Action Potential

An action potential (AP) is a rapid change in membrane potential that travels down the axon of a neuron.
Threshold potential: The membrane potential at which enough voltage-gated Na+ channels open to trigger a positive feedback cycle, leading to a rapid depolarization.
Rising phase: The depolarization of the membrane due to the influx of Na+ ions through open voltage-gated Na+ channels.
Peak: The point at which the membrane potential reaches its most positive value, typically around +40 mV.
Falling phase: The repolarization of the membrane as voltage-gated Na+ channels inactivate and voltage-gated K+ channels open, allowing K+ ions to flow out of the cell.
Undershoot: The membrane potential briefly becomes more negative than the resting potential due to the continued efflux of K+ ions.
This all-or-none event is essential for neural communication, enabling the transmission of information over long distances in the nervous system.

Important Considerations

Tetrodotoxin (TTX) blocks Na+ currents, while Tetraethyl ammonium (TEA) blocks K+ currents.
These toxins are useful tools for studying the roles of specific ions in neural function.
Understanding these fundamental processes allows for a deeper understanding of neural signaling and its connection to brain function and behavior.

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Description

Explore key concepts in neuroscience focusing on glial cells and membrane potential. This quiz covers the roles of different glial cells in the central and peripheral nervous systems, as well as the fundamentals of membrane potential in neurons. Test your understanding of these vital topics in neurobiology.