Which types of cells are not present in CNS? A. Osteoblasts B. Astrocytes C. Mic
ID: 176501 • Letter: W
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Which types of cells are not present in CNS? A. Osteoblasts B. Astrocytes C. Microglia D. Neurons What is the role of astrocytes in physiology of CNS? How can be described action potential in neurons? A. Depolarization of cellular membrane by influx of sodium ions inside the cell B. Depolarization of cellular membrane by outflow of sodium ions from cytoplasm C. Depolarization of cellular membrane by influx of potassium ions inside the cell D. Depolarization of cellular membrane by outflow of potassium ions from cytoplasm What is the mechanism of propagation of action potential? What is the role of vascular endothelial growth factor in angiogenesis? A. Interaction with MMPs for matrix degradation B. Initiation of angiogenesis by stimulation endothelial cells for proliferation, as well as participation in induction of these cells for migration C. Binding to pericytes for stimulation of these cells to attach to newly formed capillary D. Binding to ECM proteins to stimulate endothelial cells for migration What is the difference between angiogenesis and vasculogenesis?Explanation / Answer
4. Osteoblasts are not found in the CNS. They are cells responsible for bone synthesis in the body.
Astrocytes are star shaped glial cells found in the brain and spinal cord. They are associated with the repair of the nervous system. When the nerve cells gets injured in the CNS, these cells fill up the gap and form a glial cell scar. They in turn get transformed to neurons and repair the injured area. They play a major role in repair of cells in CNS that cannot regenerate themselves.
5. A. Depolarisation of cellular membrane by influx of sodium ions inside the cell
Mechanism of propagation of action potential:
1. Depolarisation: The first step of the propagation of action potential is the depolarisation of the cellular membrane. There is influx of positively charged sodium ions into the cell. This causes a reveral in cellular polarity and the inside of the cell becomes more positive while the outside of the membrane is relatively negative.
2. Repolarisation: Repolarisation takes place when the electric gradient reaches a threshold value. The sodium channels gets closed while potassium channels are opened. These postassium channels lead to the release of postassium ions from the neuron which results in the restoration of the normal membrane potential of the cell.
3. Refractory phase: This is a short phase that takes place after depolarisation. This is also called the resting phase and the cells cannot be depolarized during this phase. After some time of the opening of sodium channels, they automaticalls close themselves and become inavtive for a certain period of time. They cannot be opened until the normal resting potential of the cells are reached again.
6. B. Initiation of angiogeneis by stimulation of endothelial cells for proliferation as well as participation in induction of these cells for migration.
Vasculogenesis is the de novo generation of blood vessels from vascular progenitor cells while angiogenesis is the formation of new blood vessels from the existing capillaries. Vasculogenesis begins after the initiation of gastrulation in mammalian embryos while angiogenesis is a continuous process involved mainly in wound healing.
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