Lec 21/22 - MCQ - Neurons and Glia

Astrocytes are star-shaped glial cells that play a crucial role in the formation and maintenance of synapses in the central nervous system (CNS).

Astrocytes release extracellular protein signals that act as triggers for synapse formation in the CNS. These signals guide the growth and development of neuronal connections.

Similar to the CNS, adult hippocampal stem cells also rely on astrocytes to guide the formation of new synapses, showcasing the critical role of astrocytes in neuronal plasticity.

In the peripheral nervous system, Schwann cells, a type of glial cell, play the role of astrocytes in triggering the formation of neuromuscular junctions, which connect motor neurons to muscle fibers.

Glial cells, like astrocytes, can sense neuronal activity by registering calcium transient currents, indicating the electrical firing of neurons.

In response to neuronal activity, glial cells release gliotransmitters, signaling molecules that can modulate neuronal function and synaptic transmission. This highlights the active role of glial cells in brain activity.

Astrocytes and other macroglia (large glial cells) are essential participants in synaptogenesis. They provide structural support, regulate the extracellular environment, contribute to synapse maturation, and even influence the strength of synaptic connections.

The movement of ions across the cell membrane is primarily governed by diffusion through ion channels. These channels act like selective gates, allowing specific ions to pass through the membrane based on their concentration gradient and electrical potential.

At rest, the concentration of sodium ions (Na+) is higher outside the cell, while the concentration of potassium ions (K+) is higher inside the cell. This unequal distribution of ions across the membrane creates an electrical potential difference.

At rest, the cell membrane is more permeable to potassium ions (K+) than to sodium ions (Na+). This means that K+ ions can move more easily across the membrane, contributing to the establishment of the negative resting membrane potential inside the cell.

The resting membrane potential of cells typically ranges from -60 to -80 millivolts (mV). This negative potential is maintained by the unequal distribution of ions and the activity of the sodium-potassium pump.

The sodium-potassium pump (Na+/K+ pump) is an electrogenic pump that actively transports ions across the cell membrane. It pumps 3 potassium ions (K+) out of the cell and 2 sodium ions (Na+) into the cell, consuming energy in the process. This action contributes to the negative resting membrane potential inside the cell.

The voltage difference that exists across a cell membrane at rest is called the resting membrane potential. This potential difference is primarily due to the unequal distribution of ions across the membrane.

The main factor contributing to the resting membrane potential is the unequal distribution of ions, particularly sodium (Na+) and potassium (K+). This unequal distribution creates a concentration gradient that drives the movement of ions, leading to the negative resting membrane potential.

Neurons are specialized cells that are responsible for generating and transmitting electrical signals throughout the nervous system. They communicate with each other and with other cells using electrical current.

Ions move across the cell membrane primarily through diffusion through ion channels. These channels are specialized proteins embedded in the membrane that allow特定イオンの通過のみ許可し、その通過はイオンの濃度勾配及び電気化学的勾配に依存する。

Glial cells, also known as neuroglia, are a diverse population of cells in the nervous system that support and protect neurons. They provide structural support, maintain the extracellular environment, insulate axons, and contribute to the formation and maintenance of synapses.

The Nernst equation is a mathematical formula that can be used to predict the equilibrium potential for a specific ion, such as potassium (EK+). This equation takes into account the concentration of the ion inside and outside the cell, as well as its charge.

The resting membrane potential typically ranges between -60 to -80 millivolts (mV). This potential is maintained by the unequal distribution of ions, particularly sodium (Na+) and potassium (K+), and the activity of the sodium-potassium pump.

The main function of the sodium-potassium pump (Na+/K+ pump) is to maintain a negative charge inside the cell. It does this by actively transporting three potassium ions (K+) out of the cell and two sodium ions (Na+) into the cell, consuming energy in the process.

Voltage-gated channels are a type of ion channel that opens and closes in response to changes in the membrane potential. They are typically composed of protein subunits that undergo conformational changes when the membrane potential reaches a certain threshold.

The threshold for the activation of voltage-gated sodium (Na+) channels during an action potential is approximately +15 mV. Once the membrane potential reaches this threshold, the channels open, allowing Na+ ions to rush into the cell and further depolarize the membrane.

The inactivation gate is a part of the voltage-gated sodium (Na+) channel structure. It closes shortly after the channel opens, preventing further influx of Na+ ions. This inactivation is crucial for facilitating action potential propagation in one direction only, preventing it from traveling backwards.

In unmyelinated axons, the distance between nodes of Ranvier is typically 1-3 mm. These nodes are gaps in the myelin sheath, allowing action potentials to regenerate and travel faster along the axon.

Oligodendrocytes are a type of glial cell found in the central nervous system (CNS) that are responsible for myelinating axons. They wrap their membrane around axons, forming a fatty insulating layer that speeds up action potential conduction.

Astrocytes are star-shaped glial cells that play a crucial role in regulating the extracellular environment around neurons. They help maintain ion balance, remove neurotransmitters, and provide structural support to neurons.

Metabotropic receptors are a type of receptor that indirectly activates intracellular signaling pathways through a series of molecular intermediates. They are typically slower acting than ionotropic receptors, but their effects can last longer.