L1 - Nervous System Flashcards
What is the primary function of neurons?
Neurons transmit information both chemically and electrically, from the environment/periphery to the brain and from the brain to the periphery.
What ability allows neurons to transmit information?
Neurons generate and conduct electrical impulses, making them excitable cells.
How many neurons are estimated to be in the human brain?
Approximately 80 billion neurons are found in the human brain.
What are the two main divisions of the nervous system?
The two main divisions of the nervous system are the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
What does the Central Nervous System consist of?
The Central Nervous System consists of the brain and spinal cord.
What are the two main components of the Peripheral Nervous System?
The Peripheral Nervous System consists of the autonomic nervous system and the somatic nervous system.
What are the two divisions of the autonomic nervous system?
The autonomic nervous system is divided into the sympathetic and parasympathetic systems.
What are the two types of pathways in the nervous system?
The two types of pathways in the nervous system are sensory (afferent) and motor (efferent).
Sensory (afferent) pathways carry information toward the CNS, while motor (efferent) pathways carry information away from the CNS.
What is the main structural role of astrocytes?
Astrocytes provide structural support by interweaving with neurons and supplying a matrix in which neurons can sit.
How do astrocytes support neurons energetically?
Astrocytes provide energy and nutrients to neurons
What role do astrocytes play in blood flow?
Astrocytes help control blood flow in the brain.
How do astrocytes contribute to neurotransmitter activity?
Astrocytes are involved in the release and reuptake of neurotransmitters in the synapse.
What is the main function of microglia in the brain?
Microglia act as brain macrophages, defending the brain against infections.
How do microglia defend the brain against infection?
Microglia eliminate bacteria through phagocytosis.
What role do microglia play in clearing cellular debris?
Microglia clear debris, such as dead or damaged cells.
What is synaptic pruning and how are microglia involved?
Synaptic pruning is the process by which microglia remove excess or unused synapses to optimize brain function.
What is the function of oligodendrocytes in the central nervous system?
Oligodendrocytes extend processes that wrap around axons to form the myelin sheath.
: What is the role of the myelin sheath?
The myelin sheath protects and supports the axon, and insulates it to improve signal transmission.
What are the nodes of Ranvier, and how are they formed?
The nodes of Ranvier are gaps in the myelin sheath where ion channels are concentrated. They are formed by the spacing between oligodendrocytes’ myelin-wrapped axons.
What is the primary function of ependymal cells in the central nervous system?
Ependymal cells are involved in the production and flow of cerebrospinal fluid (CSF).
How do ependymal cells contribute to brain metabolism?
Ependymal cells assist in brain metabolism and help with waste clearance in the brain.
What stem cell-like function do ependymal cells have?
Ependymal cells may have the potential to differentiate into other types of cells, such as astrocytes or oligodendrocytes, though this is still under investigation.
What is synaptic transmission?
ynaptic transmission is the process by which neurons transmit chemical or electrical signals across a synapse to communicate with other neurons.
How many neurons are estimated to be in the human brain?
here are approximately 80 billion neurons in the human brain.
How many synapses are estimated to exist in the cortex alone?
The cortex contains around 0.15 quadrillion synapses.
What is the main role of synaptic transmission in the nervous system?
Synaptic transmission allows the passing of signals between neurons, facilitating communication within the central and peripheral nervous systems.
What is the first step in synaptic transmission?
Neurotransmitter (NT) synthesis – The neurotransmitter is synthesized in the presynaptic neuron.
What happens after neurotransmitter synthesis?
Uptake into a vesicle – The neurotransmitter is taken up into synaptic vesicles for storage.
How does depolarization occur in synaptic transmission?
Depolarization via opening of voltage-gated Na+ channels – This causes an influx of Na+ ions, leading to depolarization.
What occurs after depolarization in synaptic transmission?
Influx of Ca2+ via voltage-gated Ca2+ channels – Calcium ions enter the presynaptic terminal.
What happens when calcium ions enter the presynaptic terminal?
Release of neurotransmitter via exocytosis – The neurotransmitter is released from synaptic vesicles into the synaptic cleft.
What happens after the release of neurotransmitters?
Presynaptic receptor activation – The released neurotransmitter may activate presynaptic receptors to regulate further neurotransmitter release
What happens after neurotransmitter release?
Postsynaptic receptor activation – The neurotransmitter binds to receptors on the postsynaptic neuron, leading to a response.
How is neurotransmitter activity terminated?
Reuptake of neurotransmitter via transporters – Neurotransmitters are taken back into the presynaptic neuron for recycling.
What is the final step in the process?
Neurotransmitter metabolism – The neurotransmitter is broken down or metabolized to stop its action.
What is the voltage-gated sodium (VGNa+) channel?
VGNa+ channels are specialized ion channels that allow the passage of sodium ions (Na+) across the cell membrane in response to changes in membrane potential.
What state is the VGNa+ channel in at a resting membrane potential?
At a resting membrane potential of -70 mV, the VGNa+ channel is in a closed state, preventing the flow of sodium ions.
What triggers the opening of VGNa+ channels?
The VGNa+ channels open when the membrane potential becomes more positive (depolarized) to around -50 mV, allowing sodium ions (Na+) to enter the cell.
What happens when the VGNa+ channel opens?
When the VGNa+ channel opens, sodium ions (Na+) rapidly flow into the cell, causing further depolarization, which is an essential part of the action potential.
What happens after VGNa+ channels open and sodium enters the cell?
The influx of sodium ions leads to the rapid depolarization of the cell membrane, which propagates the action potential along the neuron.
How are VGNa+ channels closed after depolarization?
After depolarization, the VGNa+ channel enters an inactive state, where it cannot reopen immediately. This is followed by a recovery period during which the channel returns to its closed state and is ready to open again in response to a new depolarization.
What are voltage-gated calcium (VGCa2+) channels?
VGCa2+ channels are ion channels that open in response to changes in membrane potential, allowing calcium ions (Ca2+) to flow into the cell.
What is the role of calcium ions (Ca2+) in the cell?
Calcium ions (Ca2+) act as a critical intracellular messenger and are involved in various cellular processes, including changes in membrane potential and vesicle fusion during synaptic transmission.
How does calcium influence neurotransmitter release?
The influx of Ca2+ through VGCa2+ channels during depolarization triggers the fusion of synaptic vesicles with the presynaptic membrane, leading to the release of neurotransmitters into the synapse.
What is the calcium concentration before and after depolarization?
Before depolarization, the intracellular calcium concentration is less than 0.1 μM. After depolarization, it rises to 1-100 μM, allowing for cellular signaling and vesicle fusion.
What is the function of Ca2+ during exocytosis?
Calcium binds to proteins involved in exocytosis, facilitating the fusion of synaptic vesicles with the cell membrane and enabling the release of neurotransmitters into the synapse.
What triggers the opening of VGCa2+ channels?
VGCa2+ channels open in response to membrane depolarization, allowing calcium ions to enter the cell and initiate downstream signaling events.
What is the importance of calcium influx during synaptic transmission?
Calcium influx is essential for vesicle fusion and neurotransmitter release, which are fundamental processes for synaptic signaling and communication between neurons.
What are ligand-gated ion channels (LGICs)?
Ligand-gated ion channels (LGICs) are a type of ionotropic receptor that open in response to the binding of a ligand (such as a neurotransmitter), allowing ions to flow through the membrane.
What is the structure of ligand-gated ion channels (LGICs)?
LGICs are ion channels that form a pore in the cell membrane, allowing the passage of ions between the extracellular and intracellular spaces. The specific structure can vary among different types of LGICs.
: How do LGICs function?
When a ligand binds to the LGIC, it induces a conformational change that opens the ion channel, allowing ions to move down their concentration gradients across the membrane.
What is the role of LGICs in postsynaptic receptor activation?
LGICs are involved in postsynaptic receptor activation, where neurotransmitters bind to the receptor, opening the ion channel and enabling ions to flow into or out of the postsynaptic cell, altering its membrane potential.
What happens to ions when they pass through LGICs?
Ions move through LGICs down their concentration gradients, contributing to changes in the electrical potential across the membrane and participating in processes like synaptic signaling.
What are ligand-gated ion channels (LGICs) also known as?
Ligand-gated ion channels are commonly known as ionotropic receptors.
What is the structure of ligand-gated ion channels (LGICs)?
LGICs are ion channels that connect the extracellular environment with the intracellular space, allowing the movement of ions across the membrane. Their structure can vary depending on the type of LGIC.
What occurs during postsynaptic receptor activation via LGICs?
When a neurotransmitter binds to a postsynaptic receptor (LGIC), the ion channel opens, allowing specific ions to flow into or out of the postsynaptic cell.
How does ion influx or efflux from LGICs affect the cell?
The influx or efflux of ions through LGICs activates intracellular signaling pathways and alters the excitability of the cell, influencing its electrical properties and the transmission of signals.
Which ions typically flow through ligand-gated ion channels (LGICs)?
Common ions that flow through LGICs include calcium (Ca²⁺), sodium (Na⁺), chloride (Cl⁻), and potassium (K⁺), which play roles in regulating cell excitability and signaling.
How fast is the activation of postsynaptic receptors via LGICs?
The activation of postsynaptic receptors via LGICs occurs within milliseconds, allowing for rapid signaling in the nervous system.
How does the activation of LGICs contribute to depolarization?
When LGICs open, ions like sodium (Na⁺) flow into the cell, making the inside of the cell more positive compared to the outside, leading to depolarization.
What is depolarization in terms of cellular potential?
Depolarization refers to a reduction in the membrane potential, making the inside of the cell more positive relative to the outside.
How does sodium (Na⁺) contribute to depolarization?
When sodium (Na⁺) ions enter the cell through LGICs, it causes the membrane potential to become more positive, which is a key step in initiating an action potential.
What is the role of voltage-gated sodium channels (VGNa⁺) in depolarization?
Voltage-gated sodium channels (VGNa⁺) open in response to membrane depolarization, allowing more Na⁺ to enter the cell and further propagate the depolarization, leading to the generation of an action potential.
What is the connection between neurotransmission and postsynaptic receptor activation
Neurotransmission involves the release of neurotransmitters that activate postsynaptic receptors, such as LGICs, causing ion influx (e.g., Na⁺) that leads to changes in membrane potential and potentially triggers an action potential.
What is hyperpolarization in terms of cellular potential?
Hyperpolarization refers to an increase in the membrane potential, making the inside of the cell more negative compared to the outside.
How does the activation of LGICs contribute to hyperpolarization?
When certain LGICs open (e.g., chloride channels), ions like chloride (Cl⁻) enter the cell or potassium (K⁺) exits, making the inside of the cell more negative, leading to hyperpolarization.
: How does hyperpolarization prevent an action potential
Hyperpolarization moves the membrane potential further from the threshold required to trigger an action potential, effectively preventing the depolarization needed for an action potential to occur.
Why is there no activation of voltage-gated sodium channels (VGNa⁺) during hyperpolarization?
During hyperpolarization, the membrane potential is too negative to reach the threshold required for the VGNa⁺ channels to open, thus no action potential is generated.
What effect does hyperpolarization have on cell excitability?
Hyperpolarization decreases cell excitability, making it less likely for the cell to fire an action potential.
What happens to cell excitability during depolarization?
During depolarization, the inside of the cell becomes more positive compared to the outside, making the cell more excitable and more likely to generate an action potential.
What happens to cell excitability during hyperpolarization?
During hyperpolarization, the inside of the cell becomes more negative compared to the outside, making the cell less excitable and less likely to generate an action potential.
How does ion movement contribute to depolarization?
Depolarization occurs when ions like sodium (Na⁺) and calcium (Ca²⁺) flow into the cell, making the inside more positive compared to the outside.
How does ion movement contribute to hyperpolarization?
Hyperpolarization occurs when ions like chloride (Cl⁻) enter the cell or potassium (K⁺) exits the cell, making the inside more negative compared to the outside.
How does the flow of calcium (Ca²⁺) influence the cell membrane potential?
Calcium (Ca²⁺) influx contributes to depolarization by making the inside of the cell more positive, thus increasing excitability.
How does the flow of chloride (Cl⁻) or potassium (K⁺) influence the cell membrane potential?
Chloride (Cl⁻) influx or potassium (K⁺) efflux results in hyperpolarization by making the inside of the cell more negative, thereby reducing excitability.
What is an agonist?
An agonist is a drug or an endogenous ligand (e.g., neurotransmitter) that binds to a receptor and induces a physiological effect.
What is an antagonist?
An antagonist is a drug that binds to a receptor but does not induce a physiological effect; it prevents the agonist or endogenous ligand from producing an effect.
What are the steps in synaptic transmission?
Neurotransmitter (NT) synthesis
Uptake into a vesicle
Depolarization via opening of voltage-dependent Na+ channels
Influx of Ca2+ via voltage-gated Ca2+ channels
Release of NT via exocytosis
Activation of presynaptic receptors
Activation of postsynaptic receptors
Reuptake of NT via transporters
NT metabolism
What is synaptic transmission?
Synaptic transmission is the process by which a neuron communicates with another neuron or target cell. It involves the release of neurotransmitters from a presynaptic neuron, the activation of receptors on the postsynaptic neuron, and the initiation of cellular responses.
