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Safari File Edit View History Bookmarks Window Help ezto.mheducation.com Class summary-Google Slides Post Lab 9 (Brain and Cranial Nerves) Forum: Extra Credit 5 points -E connect Umm ANATOMY &PHYSIOLOGY; ost Lab 9 (Brain and Cranial Nerves instruct Question 21 (of 30) Save & Exit ? Time remaining: veluer 0.16 points Astrocytes: Functions Check all that are true statements regarding astrocytes. Astrocytes are the most abundant glial cells in the CNS Astrooytes help form the blood-brain barrier by wrapping around capillariesin Astrocytes respond to infections in the CNS through phagocytic activity by wrapping around capillaries in the brain assist in neuronal fetal development by secreting chemicals that regulate neuronal connections References Check All ThatAstrocytés: Functions Apply

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Astrocytes are group of star shaped cells with branching process. It comes from two greek word astro which means astron or star and cyte means kytos or cavity or it can be called cells.

Astrocytes are also known as astroglia. These are star shaped glial cells, found in brain and spinal cord. Brain and spinal cord combinely form central nervous system or CNS. There are 2 types of astrocytes.

1- Protoplasmic astrocytes- it is chiefly found in gray matter of brain and spinal cord. The cells have large ovoid nuclei, granular cytoplasm, coarse and protoplasmic process which branch repeatedly. Some process attach to small blood vessesls by expanded vascular end feet or pedicles. These cells contain no fibrils.

2-Fibrous Astrocytes- These found between the myelinated fibre tracts of the white matter of the CNS. The cell possesses fewer but longer processes than the protoplasmic type. Long, unbranched fibrils of a keratin develop within the cytoplasm.

1- So astrocytes are most abudant in glial cess in CNS. It may be true because astrocyte cells are 20% to 40% in glial cells. Its number may increase according to its function in the CNS like BBB, PHagocytosis and gap sealing of neuron. During this time there is need of astrocytes to perform these functions.These are macroglial cells om CNS. It is also found in the glial cells which are associated with synapse. So it is most abudant in synapse.

2-Astrocytes help form the blood- brain- barrier by wrapping around capillaries in the brain. Its true because astrocytes seal the injury or gap in the axon of neurins by forming new cytoskelital structure.The wall of brain capillaries are less permiable than other capillaries because they are non fenestrated and their endothelial cells are connected by tight junctions. This feature is called (BBB) blood-brain-barrier. So only water CO2. O2, lipid soluble substances like alcohol, anasthetics cross the cerebral capillaries easily. They are impermiable to large molecules like plsma proteins and non-lipid organic molecules. Astrocytes are essential for formation of BBB by secreting factors which make an association between BBB and formation of the tight junction. Its like filling the gap/space of neurons.

3-Astrocytes respond to infections in CNS through phagocyte activity. Its true but most of the functions of astrocytes are still remaines or scientists are working on it. Astrocytes are reactive or active during any injury of brain. This reactive astrocytes function as phagocyte.

4-Astocytes assist in neural fatal development by secreting chemicals that regulate neuronal connects. Its also true statement of functions of astrocytes.

Because astrocytes are main cellular components of the glial scar. After injury, astrocytes undergo morphological changes, secretes a protein which is acidic in nature(GFAP-glial fibrillary acidic protein). It helps astrocytes to synthesize more skeletal structure. Astrocutes form a network of plasma membrane that will fill the injury/empty spaces. But recent study shows that astrocytes have been creating a reactive phenotype (astrogliosis-filling the injury regulated by GFAP) is toxic to neurons. It releases signals that can kill neurons. So astrocytes also assist in neuronal fatal.

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