Questions and Answers
Which type of cell is responsible for myelinating axons in the central nervous system?
Astrocytes are involved in the regeneration of damaged axons in the peripheral nervous system.
False
What is the primary function of microglia in the central nervous system?
Immune defense
Glucose is transported into astrocytes by the __________ transporter.
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Match the cell type with its role:
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Which statement about nodes of Ranvier is correct?
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Glutamine can be transported back to neurons where it is converted into GABA.
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What is the role of astrocytes concerning glucose levels for neurons?
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The fatty insulating layer surrounding axons is called __________.
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What happens when oligodendrocytes are damaged?
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What is one of the primary functions of astrocytes?
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The blood-brain barrier is made up of four layers.
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Name a location in the brain where the blood-brain barrier is compromised to allow molecular exchange.
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Astrocytes help regulate levels of _______ and GABA in the brain.
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Match the following substances with their ability to cross the blood-brain barrier:
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Which of the following processes is NOT a function of astrocytes?
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Astrocytes can redistribute excess potassium between each other through gap junctions.
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What enzyme do astrocytes use to convert excess glutamate into glutamine?
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The _______ in the hypothalamic-pituitary axis allows for hormone signaling between glands.
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What role do astrocytes play in the blood-brain barrier?
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Which of the following substances can easily cross the blood-brain barrier?
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Astrocytes play a role in the formation of the blood-brain barrier.
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What is the primary function of the blood-brain barrier?
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Astrocytes help in __________ excess potassium from the extracellular space during action potentials.
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Match the brain region with its specific function relating to the blood-brain barrier:
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Which type of molecule requires specific transport proteins to pass through the blood-brain barrier?
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The blood-brain barrier consists only of endothelial cells.
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What do astrocytes convert excess glutamate into?
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The process of __________ allows astrocytes to redistribute excess potassium between each other.
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Astrocytes secrete growth factors to enhance the formation of which structure?
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What is the primary function of astrocytes in relation to glycogen?
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Schwann cells are responsible for myelinating axons in the central nervous system.
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What do nodes of Ranvier contain that is crucial for action potential propagation?
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Astrocytes assist in synthesizing GABA from glutamate via the enzyme __________.
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Which type of cells help regulate potassium homeostasis in the peripheral nervous system?
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Match the following cells with their primary functions:
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Glutamate can convert back to glutamine in neurons.
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What is one disease associated with central nervous system demyelination?
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Microglia originate from __________ in the bone marrow.
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Which factor does NOT increase conduction velocity in neurons?
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Which of the following substances can easily cross the blood-brain barrier?
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Astrocytes only function in the central nervous system.
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What structure helps form the blood-brain barrier?
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Astrocytes help to regulate levels of _______ in the brain.
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Match each brain region with its specific function relating to the blood-brain barrier:
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Which of the following is NOT a function of astrocytes?
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Potassium ions can easily cross the blood-brain barrier without assistance.
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What enzyme do astrocytes use to convert excess glutamate to glutamine?
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Astrocytes absorb excess potassium during action potentials to maintain neuronal _______.
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What role do astrocytes play concerning the blood-brain barrier?
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What type of cell is primarily responsible for producing cerebrospinal fluid (CSF)?
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Oligodendrocytes have the ability to regenerate after damage, similar to Schwann cells.
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What is the main function of Schwann cells in the peripheral nervous system?
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The gaps between myelin sheaths on axons are called __________.
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Match the following cells with their corresponding primary roles:
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Which of the following molecules helps transport glucose into astrocytes?
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Type A fibers have the lowest conduction velocity due to high myelination.
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What role do astrocytes play in relation to potassium levels in the brain?
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Microglia originate from __________ in the bone marrow.
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What is one of the consequences of excessive microglial activity?
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Which of the following substances can easily cross the blood-brain barrier?
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Astrocytes only exist in the peripheral nervous system.
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What type of tissue do glial cells mainly support?
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Astrocytes help maintain neuronal __________ by absorbing excess potassium during action potentials.
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Match the brain region with its specific function relating to the blood-brain barrier:
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Which statement best describes the blood-brain barrier?
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Astrocytes convert excess glutamate into glutamine using the enzyme glutamine synthetase.
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What role do astrocytes play in relation to potassium ions during action potentials?
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Certain regions of the brain have a __________ blood-brain barrier to allow molecular exchange.
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Match the molecule type with its ability to cross the blood-brain barrier:
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What type of cells are equivalent to astrocytes in the peripheral nervous system?
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Oligodendrocytes are responsible for myelinating multiple axons in the peripheral nervous system.
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Name one disease associated with peripheral nervous system demyelination.
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The gaps between the myelin sheaths are called __________.
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What is the primary role of microglia in the central nervous system?
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Match the following cells with their functions:
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Glucose transport into astrocytes is facilitated by the GLUT3 transporter.
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What is the function of the neurolemma in Schwann cells?
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Myelin is primarily composed of _______ and proteins.
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Which type of fibers have the fastest conduction velocity due to high myelination?
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Which of the following correctly describes the blood-brain barrier (BBB)?
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Astrocytes are primarily found in the peripheral nervous system.
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What is the role of astrocytes in potassium buffering?
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The _____ consists of regions in the brain where the blood-brain barrier is compromised to allow molecular exchange.
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Match the region of the brain with its function in relation to the blood-brain barrier:
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Which of the following substances can easily cross the blood-brain barrier?
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Astrocytes enhance the formation of tight junctions within the blood-brain barrier.
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What enzyme do astrocytes use to convert excess glutamate into glutamine?
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Astrocytes help maintain neuronal _______ by absorbing excess potassium during action potentials.
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Which process occurs at the astrocytic foot processes of the blood-brain barrier?
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What is the main function of ependymal cells?
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Schwann cells have regenerative capabilities after injury while oligodendrocytes do not.
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What role do oligodendrocytes play in the central nervous system?
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Microglia respond to pathogens in the central nervous system by releasing __________ substances.
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Match the following types of neuron fibers with their myelination characteristics:
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Which type of transport protein do neurons use to uptake glucose?
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The nodes of Ranvier contain voltage-gated sodium channels that are crucial for action potential conduction.
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What do astrocytes convert excess glutamate into?
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Astrocytes assist in the metabolism of __________ from glycogen for ATP production in neurons.
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What is a common disease associated with peripheral nervous system demyelination?
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Study Notes
Glial Cells Overview
- Nervous tissue consists of neurons and glial cells.
- Glial cells are found in both the central nervous system (CNS: brain and spinal cord) and peripheral nervous system (PNS: all nerves).
Astrocytes
- Astrocytes are a type of glial cell only located in the CNS.
- They have multiple functions, including forming part of the blood-brain barrier (BBB).
Blood-Brain Barrier Structure
- Blood-brain barrier consists of three layers:
- Endothelial cells with tight junctions.
- Basal lamina, a type of connective tissue.
- Foot processes from astrocytes that help form the barrier.
Blood-Brain Barrier Function
- The BBB controls the movement of molecules between blood and nervous tissue.
- Lipid-soluble substances and gases (like CO2 and O2) can easily cross the BBB.
- Charged ions and larger molecules need specific transport proteins to pass through the BBB.
- Astrocytes secret growth factors to enhance tight junction formation within the BBB, maintaining its selectivity.
Areas with Compromised Blood-Brain Barrier
- Certain regions in the brain have a compromised BBB to allow for necessary molecular exchange:
- Area postrema: samples blood for toxins and triggers vomiting response.
- Osmoreceptors near the hypothalamus: monitor blood saltiness and glucose levels to regulate fluid balance.
- Hypothalamic-pituitary axis: allows hormone signaling between the hypothalamus and pituitary gland.
Potassium Buffering
- Astrocytes absorb excess potassium from the extracellular space during action potentials to maintain neuronal excitability.
- Astrocytes can redistribute excess potassium between each other through gap junctions, preventing disruptive increases in extracellular potassium concentrations.
Neurotransmitter Regulation
- Astrocytes help regulate glutamate and GABA levels:
- They uptake excess glutamate from synaptic clefts and convert it to glutamine using the enzyme glutamine synthetase.
- Glutamine can then be transported back to neurons, where it is converted back to glutamate.
- They assist in the synthesis of GABA from glutamate via the enzyme glutamate decarboxylase.
Glycogen and Glucose Metabolism
- Astrocytes store glycogen and regulate glucose levels for neurons:
- They can sense decreased ATP levels in neurons and respond by breaking glycogen into glucose.
- Glucose can be converted into pyruvate and then into lactate which is transported to the neurons for ATP production.
- Glucose transport into astrocytes is facilitated by the GLUT1 transporter, while neurons utilize GLUT3 to uptake glucose.### Glut Transporters
- Blood-brain barrier (BBB) has one type of glut transporter.
- Neurons contain three types of glut transporters.
Astrocytes
- Play a role in increasing synaptic connections between neurons.
- Mechanism behind this enhancement remains unclear in existing literature.
Satellite Cells
- Considered the peripheral nervous system (PNS) equivalent of astrocytes.
- Function similarly to astrocytes, excluding blood-brain barrier involvement.
- Regulate nutrient metabolism, neurotransmitter levels, and potassium homeostasis.
Locations of Satellite Cells
- Found in two key areas: dorsal root ganglia and autonomic ganglia.
- Dorsal root ganglia consist of cell bodies outside the spinal cord; satellite cells surround these bodies.
- Autonomic ganglia include sympathetic and parasympathetic ganglia:
- Sympathetic ganglia: pre-vertebral (near vertebrae) and para-vertebral (alongside spinal cord).
- Parasympathetic ganglia: terminal ganglia, located near target organs.
Oligodendrocytes vs. Schwann Cells
- Oligodendrocytes myelinate axons in the central nervous system (CNS).
- They produce lipid protein sheaths around CNS axons, including cranial nerve II (optic nerve).
Schwann Cells
- Responsible for myelinating axons in the peripheral nervous system.
- Myelination includes all spinal nerves and cranial nerves III to XII.### Myelination in the Nervous System
- Schwann cells myelinate axons in the peripheral nervous system, covering segments of a single axon.
- Oligodendrocytes myelinate multiple axons (30-60 axons) in the central nervous system, including cranial nerve II.
- Damage to oligodendrocytes leads to irreversible demyelination; there is no regeneration ability.
- Schwann cells have regenerative capacities; damage can potentially lead to remyelination, especially in conditions like Guillain-Barre Syndrome.
Demyelination Diseases
- Central nervous system demyelination is associated with multiple sclerosis.
- Peripheral nervous system demyelination is often referred to as Guillain-Barre Syndrome.
Structure and Function of Schwann Cells
- Schwann cells extend "arms" to wrap around axons, creating concentric layers; this structure constitutes the myelin sheath.
- The outer layer of Schwann cells is known as the neurolemma, which is crucial for regeneration following damage.
Myelin Composition and Function
- Myelin is composed mainly of lipids and proteins, acting as an insulator that enhances action potential propagation along axons.
- Myelinated axons facilitate saltatory conduction, resulting in faster signal transmission compared to non-myelinated axons, which use continuous conduction.
Nodes of Ranvier
- The gaps between myelin sheaths on axons are called nodes of Ranvier, where voltage-gated sodium channels are concentrated.
- Action potentials "skip" from node to node due to the absence of channels under the myelin sheath, maximizing conduction speed.
Factors Affecting Conduction Velocity
- Myelination and axon diameter both increase conduction velocity; larger diameters reduce resistance to signal flow.
- Neuron types vary by myelination:
- Type A (alpha, beta, gamma, delta) fibers have the fastest conduction velocity due to high myelination.
- Type B fibers possess moderate myelination and conduction speed.
- Type C fibers have little to no myelin, resulting in low conduction speeds.
Ependymal Cells
- Ependymal cells line the ventricles of the brain and contribute to the blood-cerebrospinal fluid (CSF) barrier.
- They have tight junctions that ensure selective permeability and regulate the movement of molecules like water, glucose, and ions.
- Ependymal cells produce and circulate cerebrospinal fluid (CSF) via ciliary movement.
Microglia
- Microglia are specialized immune cells in the central nervous system, originating from monocytes in the bone marrow.
- They respond to pathogens and neuronal damage by releasing pro-inflammatory substances and reactive oxygen species, which can inadvertently harm healthy tissue.
- Microglia can phagocytose pathogens and present their antigens to T cells through MHC class II molecules, amplifying the immune response.
- Overactivity of microglia can lead to demyelination and contribute to conditions such as encephalitis, particularly in diseases like HIV.
Glial Cells Overview
- Nervous tissue is composed of neurons and glial cells.
- Glial cells are present in both the central nervous system (CNS) and peripheral nervous system (PNS).
Astrocytes
- Found exclusively in the CNS, astrocytes perform various functions, including maintaining the blood-brain barrier (BBB).
Blood-Brain Barrier Structure
- The BBB comprises three layers:
- Endothelial cells with tight junctions.
- Basal lamina, a connective tissue layer.
- Foot processes from astrocytes that help in forming the barrier.
Blood-Brain Barrier Function
- Regulates the transport of molecules between blood and nervous tissue.
- Lipid-soluble substances and gases (e.g., CO2, O2) cross the BBB easily.
- Charged ions and larger molecules require specialized transport proteins to pass through.
- Astrocytes secrete growth factors to strengthen tight junctions, enhancing the barrier's selectivity.
Areas with Compromised Blood-Brain Barrier
- Certain brain regions permit molecular exchange due to a compromised BBB:
- Area postrema: Detects blood toxins and triggers vomiting.
- Osmoreceptors near the hypothalamus: Monitor blood salts and glucose for fluid balance regulation.
- Hypothalamic-pituitary axis: Facilitates hormone signaling between hypothalamus and pituitary gland.
Potassium Buffering
- Astrocytes absorb excess potassium ions during neuronal action potentials to maintain neuronal excitability.
- They redistribute potassium among themselves via gap junctions, preventing dangerous extracellular potassium increases.
Neurotransmitter Regulation
- Astrocytes manage glutamate and GABA levels:
- Uptake excess glutamate from synapses and convert it to glutamine through glutamine synthetase.
- Glutamine is transported back to neurons, where it is reconverted to glutamate.
- Synthesize GABA from glutamate using glutamate decarboxylase.
Glycogen and Glucose Metabolism
- Astrocytes store glycogen and manage glucose levels for neurons.
- They sense low ATP levels in neurons, breaking down glycogen to release glucose.
- Glucose is transformed into pyruvate and lactate, which is sent to neurons for ATP production.
- Glucose enters astrocytes through GLUT1, while neurons use GLUT3.
Glut Transporters
- The BBB contains one type of glut transporter.
- Neurons have three distinct types of glut transporters.
Astrocytes and Synaptic Connections
- Astrocytes enhance synaptic connections between neurons, though the underlying mechanisms remain unclear.
Satellite Cells
- Satellite cells serve as the PNS counterpart to astrocytes.
- They regulate nutrient metabolism, neurotransmitter levels, and potassium homeostasis without involvement in the BBB.
Locations of Satellite Cells
- Present in the dorsal root ganglia and autonomic ganglia:
- Dorsal root ganglia: Contain cell bodies outside the spinal cord, surrounded by satellite cells.
- Autonomic ganglia: Include sympathetic (pre-vertebral and para-vertebral) and parasympathetic ganglia (near target organs).
Oligodendrocytes vs. Schwann Cells
- Oligodendrocytes myelinate axons in the CNS, covering multiple axons (30-60 per cell).
- Schwann cells myelinate axons in the PNS, covering distinct segments of individual axons.
Myelination in the Nervous System
- Damaged oligodendrocytes result in irreversible demyelination with no regeneration capacity.
- Schwann cells have regenerative potential, facilitating remyelination in damage scenarios like Guillain-Barre Syndrome.
Demyelination Diseases
- Multiple sclerosis affects demyelination in the CNS.
- Guillain-Barre Syndrome refers to demyelination in the PNS.
Structure and Function of Schwann Cells
- Schwann cells envelop axons with "arms" forming concentric layers, creating the myelin sheath.
- The neurolemma, the outer layer of Schwann cells, is crucial for post-injury regeneration.
Myelin Composition and Function
- Myelin primarily consists of lipids and proteins, serving as an electrical insulator to enhance action potential propagation.
- Myelinated axons facilitate saltatory conduction, leading to faster signal transmission compared to non-myelinated axons, which transmit signals continuously.
Nodes of Ranvier
- Gaps between the myelin sheath on axons are called nodes of Ranvier, densely packed with voltage-gated sodium channels.
- Action potentials leap from node to node, boosting conduction speed.
Factors Affecting Conduction Velocity
- Myelination and axon diameter both increase conduction velocity; larger diameters reduce resistance to signal flow.
- Neuron types vary:
- Type A fibers (alpha, beta, gamma, delta) have the fastest conduction due to high myelination.
- Type B fibers have moderate myelination and conduction speed.
- Type C fibers are unmyelinated or minimally myelinated, resulting in low conduction speeds.
Ependymal Cells
- Ependymal cells line brain ventricles and create a blood-cerebrospinal fluid barrier.
- They regulate molecule movement (water, glucose, ions) and produce cerebrospinal fluid (CSF) via ciliary movement.
Microglia
- Microglia are immune cells in the CNS, derived from bone marrow monocytes.
- They react to pathogens and injury by releasing inflammatory substances, which can harm healthy tissues.
- Capable of phagocytosing pathogens and presenting antigens to T cells, thus amplifying the immune response.
- Overactive microglia can lead to demyelination and contribute to conditions such as encephalitis, particularly in diseases such as HIV.
Glial Cells Overview
- Nervous tissue is composed of neurons and glial cells.
- Glial cells are present in both the central nervous system (CNS) and peripheral nervous system (PNS).
Astrocytes
- Found exclusively in the CNS, astrocytes perform various functions, including maintaining the blood-brain barrier (BBB).
Blood-Brain Barrier Structure
- The BBB comprises three layers:
- Endothelial cells with tight junctions.
- Basal lamina, a connective tissue layer.
- Foot processes from astrocytes that help in forming the barrier.
Blood-Brain Barrier Function
- Regulates the transport of molecules between blood and nervous tissue.
- Lipid-soluble substances and gases (e.g., CO2, O2) cross the BBB easily.
- Charged ions and larger molecules require specialized transport proteins to pass through.
- Astrocytes secrete growth factors to strengthen tight junctions, enhancing the barrier's selectivity.
Areas with Compromised Blood-Brain Barrier
- Certain brain regions permit molecular exchange due to a compromised BBB:
- Area postrema: Detects blood toxins and triggers vomiting.
- Osmoreceptors near the hypothalamus: Monitor blood salts and glucose for fluid balance regulation.
- Hypothalamic-pituitary axis: Facilitates hormone signaling between hypothalamus and pituitary gland.
Potassium Buffering
- Astrocytes absorb excess potassium ions during neuronal action potentials to maintain neuronal excitability.
- They redistribute potassium among themselves via gap junctions, preventing dangerous extracellular potassium increases.
Neurotransmitter Regulation
- Astrocytes manage glutamate and GABA levels:
- Uptake excess glutamate from synapses and convert it to glutamine through glutamine synthetase.
- Glutamine is transported back to neurons, where it is reconverted to glutamate.
- Synthesize GABA from glutamate using glutamate decarboxylase.
Glycogen and Glucose Metabolism
- Astrocytes store glycogen and manage glucose levels for neurons.
- They sense low ATP levels in neurons, breaking down glycogen to release glucose.
- Glucose is transformed into pyruvate and lactate, which is sent to neurons for ATP production.
- Glucose enters astrocytes through GLUT1, while neurons use GLUT3.
Glut Transporters
- The BBB contains one type of glut transporter.
- Neurons have three distinct types of glut transporters.
Astrocytes and Synaptic Connections
- Astrocytes enhance synaptic connections between neurons, though the underlying mechanisms remain unclear.
Satellite Cells
- Satellite cells serve as the PNS counterpart to astrocytes.
- They regulate nutrient metabolism, neurotransmitter levels, and potassium homeostasis without involvement in the BBB.
Locations of Satellite Cells
- Present in the dorsal root ganglia and autonomic ganglia:
- Dorsal root ganglia: Contain cell bodies outside the spinal cord, surrounded by satellite cells.
- Autonomic ganglia: Include sympathetic (pre-vertebral and para-vertebral) and parasympathetic ganglia (near target organs).
Oligodendrocytes vs. Schwann Cells
- Oligodendrocytes myelinate axons in the CNS, covering multiple axons (30-60 per cell).
- Schwann cells myelinate axons in the PNS, covering distinct segments of individual axons.
Myelination in the Nervous System
- Damaged oligodendrocytes result in irreversible demyelination with no regeneration capacity.
- Schwann cells have regenerative potential, facilitating remyelination in damage scenarios like Guillain-Barre Syndrome.
Demyelination Diseases
- Multiple sclerosis affects demyelination in the CNS.
- Guillain-Barre Syndrome refers to demyelination in the PNS.
Structure and Function of Schwann Cells
- Schwann cells envelop axons with "arms" forming concentric layers, creating the myelin sheath.
- The neurolemma, the outer layer of Schwann cells, is crucial for post-injury regeneration.
Myelin Composition and Function
- Myelin primarily consists of lipids and proteins, serving as an electrical insulator to enhance action potential propagation.
- Myelinated axons facilitate saltatory conduction, leading to faster signal transmission compared to non-myelinated axons, which transmit signals continuously.
Nodes of Ranvier
- Gaps between the myelin sheath on axons are called nodes of Ranvier, densely packed with voltage-gated sodium channels.
- Action potentials leap from node to node, boosting conduction speed.
Factors Affecting Conduction Velocity
- Myelination and axon diameter both increase conduction velocity; larger diameters reduce resistance to signal flow.
- Neuron types vary:
- Type A fibers (alpha, beta, gamma, delta) have the fastest conduction due to high myelination.
- Type B fibers have moderate myelination and conduction speed.
- Type C fibers are unmyelinated or minimally myelinated, resulting in low conduction speeds.
Ependymal Cells
- Ependymal cells line brain ventricles and create a blood-cerebrospinal fluid barrier.
- They regulate molecule movement (water, glucose, ions) and produce cerebrospinal fluid (CSF) via ciliary movement.
Microglia
- Microglia are immune cells in the CNS, derived from bone marrow monocytes.
- They react to pathogens and injury by releasing inflammatory substances, which can harm healthy tissues.
- Capable of phagocytosing pathogens and presenting antigens to T cells, thus amplifying the immune response.
- Overactive microglia can lead to demyelination and contribute to conditions such as encephalitis, particularly in diseases such as HIV.
Glial Cells Overview
- Nervous tissue is composed of neurons and glial cells.
- Glial cells are present in both the central nervous system (CNS) and peripheral nervous system (PNS).
Astrocytes
- Found exclusively in the CNS, astrocytes perform various functions, including maintaining the blood-brain barrier (BBB).
Blood-Brain Barrier Structure
- The BBB comprises three layers:
- Endothelial cells with tight junctions.
- Basal lamina, a connective tissue layer.
- Foot processes from astrocytes that help in forming the barrier.
Blood-Brain Barrier Function
- Regulates the transport of molecules between blood and nervous tissue.
- Lipid-soluble substances and gases (e.g., CO2, O2) cross the BBB easily.
- Charged ions and larger molecules require specialized transport proteins to pass through.
- Astrocytes secrete growth factors to strengthen tight junctions, enhancing the barrier's selectivity.
Areas with Compromised Blood-Brain Barrier
- Certain brain regions permit molecular exchange due to a compromised BBB:
- Area postrema: Detects blood toxins and triggers vomiting.
- Osmoreceptors near the hypothalamus: Monitor blood salts and glucose for fluid balance regulation.
- Hypothalamic-pituitary axis: Facilitates hormone signaling between hypothalamus and pituitary gland.
Potassium Buffering
- Astrocytes absorb excess potassium ions during neuronal action potentials to maintain neuronal excitability.
- They redistribute potassium among themselves via gap junctions, preventing dangerous extracellular potassium increases.
Neurotransmitter Regulation
- Astrocytes manage glutamate and GABA levels:
- Uptake excess glutamate from synapses and convert it to glutamine through glutamine synthetase.
- Glutamine is transported back to neurons, where it is reconverted to glutamate.
- Synthesize GABA from glutamate using glutamate decarboxylase.
Glycogen and Glucose Metabolism
- Astrocytes store glycogen and manage glucose levels for neurons.
- They sense low ATP levels in neurons, breaking down glycogen to release glucose.
- Glucose is transformed into pyruvate and lactate, which is sent to neurons for ATP production.
- Glucose enters astrocytes through GLUT1, while neurons use GLUT3.
Glut Transporters
- The BBB contains one type of glut transporter.
- Neurons have three distinct types of glut transporters.
Astrocytes and Synaptic Connections
- Astrocytes enhance synaptic connections between neurons, though the underlying mechanisms remain unclear.
Satellite Cells
- Satellite cells serve as the PNS counterpart to astrocytes.
- They regulate nutrient metabolism, neurotransmitter levels, and potassium homeostasis without involvement in the BBB.
Locations of Satellite Cells
- Present in the dorsal root ganglia and autonomic ganglia:
- Dorsal root ganglia: Contain cell bodies outside the spinal cord, surrounded by satellite cells.
- Autonomic ganglia: Include sympathetic (pre-vertebral and para-vertebral) and parasympathetic ganglia (near target organs).
Oligodendrocytes vs. Schwann Cells
- Oligodendrocytes myelinate axons in the CNS, covering multiple axons (30-60 per cell).
- Schwann cells myelinate axons in the PNS, covering distinct segments of individual axons.
Myelination in the Nervous System
- Damaged oligodendrocytes result in irreversible demyelination with no regeneration capacity.
- Schwann cells have regenerative potential, facilitating remyelination in damage scenarios like Guillain-Barre Syndrome.
Demyelination Diseases
- Multiple sclerosis affects demyelination in the CNS.
- Guillain-Barre Syndrome refers to demyelination in the PNS.
Structure and Function of Schwann Cells
- Schwann cells envelop axons with "arms" forming concentric layers, creating the myelin sheath.
- The neurolemma, the outer layer of Schwann cells, is crucial for post-injury regeneration.
Myelin Composition and Function
- Myelin primarily consists of lipids and proteins, serving as an electrical insulator to enhance action potential propagation.
- Myelinated axons facilitate saltatory conduction, leading to faster signal transmission compared to non-myelinated axons, which transmit signals continuously.
Nodes of Ranvier
- Gaps between the myelin sheath on axons are called nodes of Ranvier, densely packed with voltage-gated sodium channels.
- Action potentials leap from node to node, boosting conduction speed.
Factors Affecting Conduction Velocity
- Myelination and axon diameter both increase conduction velocity; larger diameters reduce resistance to signal flow.
- Neuron types vary:
- Type A fibers (alpha, beta, gamma, delta) have the fastest conduction due to high myelination.
- Type B fibers have moderate myelination and conduction speed.
- Type C fibers are unmyelinated or minimally myelinated, resulting in low conduction speeds.
Ependymal Cells
- Ependymal cells line brain ventricles and create a blood-cerebrospinal fluid barrier.
- They regulate molecule movement (water, glucose, ions) and produce cerebrospinal fluid (CSF) via ciliary movement.
Microglia
- Microglia are immune cells in the CNS, derived from bone marrow monocytes.
- They react to pathogens and injury by releasing inflammatory substances, which can harm healthy tissues.
- Capable of phagocytosing pathogens and presenting antigens to T cells, thus amplifying the immune response.
- Overactive microglia can lead to demyelination and contribute to conditions such as encephalitis, particularly in diseases such as HIV.
Glial Cells Overview
- Nervous tissue is composed of neurons and glial cells.
- Glial cells are present in both the central nervous system (CNS) and peripheral nervous system (PNS).
Astrocytes
- Found exclusively in the CNS, astrocytes perform various functions, including maintaining the blood-brain barrier (BBB).
Blood-Brain Barrier Structure
- The BBB comprises three layers:
- Endothelial cells with tight junctions.
- Basal lamina, a connective tissue layer.
- Foot processes from astrocytes that help in forming the barrier.
Blood-Brain Barrier Function
- Regulates the transport of molecules between blood and nervous tissue.
- Lipid-soluble substances and gases (e.g., CO2, O2) cross the BBB easily.
- Charged ions and larger molecules require specialized transport proteins to pass through.
- Astrocytes secrete growth factors to strengthen tight junctions, enhancing the barrier's selectivity.
Areas with Compromised Blood-Brain Barrier
- Certain brain regions permit molecular exchange due to a compromised BBB:
- Area postrema: Detects blood toxins and triggers vomiting.
- Osmoreceptors near the hypothalamus: Monitor blood salts and glucose for fluid balance regulation.
- Hypothalamic-pituitary axis: Facilitates hormone signaling between hypothalamus and pituitary gland.
Potassium Buffering
- Astrocytes absorb excess potassium ions during neuronal action potentials to maintain neuronal excitability.
- They redistribute potassium among themselves via gap junctions, preventing dangerous extracellular potassium increases.
Neurotransmitter Regulation
- Astrocytes manage glutamate and GABA levels:
- Uptake excess glutamate from synapses and convert it to glutamine through glutamine synthetase.
- Glutamine is transported back to neurons, where it is reconverted to glutamate.
- Synthesize GABA from glutamate using glutamate decarboxylase.
Glycogen and Glucose Metabolism
- Astrocytes store glycogen and manage glucose levels for neurons.
- They sense low ATP levels in neurons, breaking down glycogen to release glucose.
- Glucose is transformed into pyruvate and lactate, which is sent to neurons for ATP production.
- Glucose enters astrocytes through GLUT1, while neurons use GLUT3.
Glut Transporters
- The BBB contains one type of glut transporter.
- Neurons have three distinct types of glut transporters.
Astrocytes and Synaptic Connections
- Astrocytes enhance synaptic connections between neurons, though the underlying mechanisms remain unclear.
Satellite Cells
- Satellite cells serve as the PNS counterpart to astrocytes.
- They regulate nutrient metabolism, neurotransmitter levels, and potassium homeostasis without involvement in the BBB.
Locations of Satellite Cells
- Present in the dorsal root ganglia and autonomic ganglia:
- Dorsal root ganglia: Contain cell bodies outside the spinal cord, surrounded by satellite cells.
- Autonomic ganglia: Include sympathetic (pre-vertebral and para-vertebral) and parasympathetic ganglia (near target organs).
Oligodendrocytes vs. Schwann Cells
- Oligodendrocytes myelinate axons in the CNS, covering multiple axons (30-60 per cell).
- Schwann cells myelinate axons in the PNS, covering distinct segments of individual axons.
Myelination in the Nervous System
- Damaged oligodendrocytes result in irreversible demyelination with no regeneration capacity.
- Schwann cells have regenerative potential, facilitating remyelination in damage scenarios like Guillain-Barre Syndrome.
Demyelination Diseases
- Multiple sclerosis affects demyelination in the CNS.
- Guillain-Barre Syndrome refers to demyelination in the PNS.
Structure and Function of Schwann Cells
- Schwann cells envelop axons with "arms" forming concentric layers, creating the myelin sheath.
- The neurolemma, the outer layer of Schwann cells, is crucial for post-injury regeneration.
Myelin Composition and Function
- Myelin primarily consists of lipids and proteins, serving as an electrical insulator to enhance action potential propagation.
- Myelinated axons facilitate saltatory conduction, leading to faster signal transmission compared to non-myelinated axons, which transmit signals continuously.
Nodes of Ranvier
- Gaps between the myelin sheath on axons are called nodes of Ranvier, densely packed with voltage-gated sodium channels.
- Action potentials leap from node to node, boosting conduction speed.
Factors Affecting Conduction Velocity
- Myelination and axon diameter both increase conduction velocity; larger diameters reduce resistance to signal flow.
- Neuron types vary:
- Type A fibers (alpha, beta, gamma, delta) have the fastest conduction due to high myelination.
- Type B fibers have moderate myelination and conduction speed.
- Type C fibers are unmyelinated or minimally myelinated, resulting in low conduction speeds.
Ependymal Cells
- Ependymal cells line brain ventricles and create a blood-cerebrospinal fluid barrier.
- They regulate molecule movement (water, glucose, ions) and produce cerebrospinal fluid (CSF) via ciliary movement.
Microglia
- Microglia are immune cells in the CNS, derived from bone marrow monocytes.
- They react to pathogens and injury by releasing inflammatory substances, which can harm healthy tissues.
- Capable of phagocytosing pathogens and presenting antigens to T cells, thus amplifying the immune response.
- Overactive microglia can lead to demyelination and contribute to conditions such as encephalitis, particularly in diseases such as HIV.
Glial Cells Overview
- Nervous tissue is composed of neurons and glial cells.
- Glial cells are present in both the central nervous system (CNS) and peripheral nervous system (PNS).
Astrocytes
- Found exclusively in the CNS, astrocytes perform various functions, including maintaining the blood-brain barrier (BBB).
Blood-Brain Barrier Structure
- The BBB comprises three layers:
- Endothelial cells with tight junctions.
- Basal lamina, a connective tissue layer.
- Foot processes from astrocytes that help in forming the barrier.
Blood-Brain Barrier Function
- Regulates the transport of molecules between blood and nervous tissue.
- Lipid-soluble substances and gases (e.g., CO2, O2) cross the BBB easily.
- Charged ions and larger molecules require specialized transport proteins to pass through.
- Astrocytes secrete growth factors to strengthen tight junctions, enhancing the barrier's selectivity.
Areas with Compromised Blood-Brain Barrier
- Certain brain regions permit molecular exchange due to a compromised BBB:
- Area postrema: Detects blood toxins and triggers vomiting.
- Osmoreceptors near the hypothalamus: Monitor blood salts and glucose for fluid balance regulation.
- Hypothalamic-pituitary axis: Facilitates hormone signaling between hypothalamus and pituitary gland.
Potassium Buffering
- Astrocytes absorb excess potassium ions during neuronal action potentials to maintain neuronal excitability.
- They redistribute potassium among themselves via gap junctions, preventing dangerous extracellular potassium increases.
Neurotransmitter Regulation
- Astrocytes manage glutamate and GABA levels:
- Uptake excess glutamate from synapses and convert it to glutamine through glutamine synthetase.
- Glutamine is transported back to neurons, where it is reconverted to glutamate.
- Synthesize GABA from glutamate using glutamate decarboxylase.
Glycogen and Glucose Metabolism
- Astrocytes store glycogen and manage glucose levels for neurons.
- They sense low ATP levels in neurons, breaking down glycogen to release glucose.
- Glucose is transformed into pyruvate and lactate, which is sent to neurons for ATP production.
- Glucose enters astrocytes through GLUT1, while neurons use GLUT3.
Glut Transporters
- The BBB contains one type of glut transporter.
- Neurons have three distinct types of glut transporters.
Astrocytes and Synaptic Connections
- Astrocytes enhance synaptic connections between neurons, though the underlying mechanisms remain unclear.
Satellite Cells
- Satellite cells serve as the PNS counterpart to astrocytes.
- They regulate nutrient metabolism, neurotransmitter levels, and potassium homeostasis without involvement in the BBB.
Locations of Satellite Cells
- Present in the dorsal root ganglia and autonomic ganglia:
- Dorsal root ganglia: Contain cell bodies outside the spinal cord, surrounded by satellite cells.
- Autonomic ganglia: Include sympathetic (pre-vertebral and para-vertebral) and parasympathetic ganglia (near target organs).
Oligodendrocytes vs. Schwann Cells
- Oligodendrocytes myelinate axons in the CNS, covering multiple axons (30-60 per cell).
- Schwann cells myelinate axons in the PNS, covering distinct segments of individual axons.
Myelination in the Nervous System
- Damaged oligodendrocytes result in irreversible demyelination with no regeneration capacity.
- Schwann cells have regenerative potential, facilitating remyelination in damage scenarios like Guillain-Barre Syndrome.
Demyelination Diseases
- Multiple sclerosis affects demyelination in the CNS.
- Guillain-Barre Syndrome refers to demyelination in the PNS.
Structure and Function of Schwann Cells
- Schwann cells envelop axons with "arms" forming concentric layers, creating the myelin sheath.
- The neurolemma, the outer layer of Schwann cells, is crucial for post-injury regeneration.
Myelin Composition and Function
- Myelin primarily consists of lipids and proteins, serving as an electrical insulator to enhance action potential propagation.
- Myelinated axons facilitate saltatory conduction, leading to faster signal transmission compared to non-myelinated axons, which transmit signals continuously.
Nodes of Ranvier
- Gaps between the myelin sheath on axons are called nodes of Ranvier, densely packed with voltage-gated sodium channels.
- Action potentials leap from node to node, boosting conduction speed.
Factors Affecting Conduction Velocity
- Myelination and axon diameter both increase conduction velocity; larger diameters reduce resistance to signal flow.
- Neuron types vary:
- Type A fibers (alpha, beta, gamma, delta) have the fastest conduction due to high myelination.
- Type B fibers have moderate myelination and conduction speed.
- Type C fibers are unmyelinated or minimally myelinated, resulting in low conduction speeds.
Ependymal Cells
- Ependymal cells line brain ventricles and create a blood-cerebrospinal fluid barrier.
- They regulate molecule movement (water, glucose, ions) and produce cerebrospinal fluid (CSF) via ciliary movement.
Microglia
- Microglia are immune cells in the CNS, derived from bone marrow monocytes.
- They react to pathogens and injury by releasing inflammatory substances, which can harm healthy tissues.
- Capable of phagocytosing pathogens and presenting antigens to T cells, thus amplifying the immune response.
- Overactive microglia can lead to demyelination and contribute to conditions such as encephalitis, particularly in diseases such as HIV.
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Description
Explore the fascinating world of glial cells and the blood-brain barrier in this quiz. Learn about the types of glial cells, particularly astrocytes, and their roles in the central nervous system. Understand the structure and function of the blood-brain barrier and how it regulates the movement of substances within the nervous tissue.
