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About Neuron, Glia cells and Neurotransmitters.pdf

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About Neuron, Glia cells and Neurotransmitters.pdf

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This pdf is about the Neuron, Glia cells & Neurotransmitters.

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About Neuron, Glia cells and Neurotransmitters.pdf

  1. 1. Saba Parvin Haque MSc in Neuroscience from “Sophia College For Women”, Mumbai. https://www.youtube.com/chann el/UCAiarMZDNhe1A3Rnpr_WkzA
  2. 2. https://www.ninds.nih.gov/Disorders/Patient- Caregiver-Education/Life-and-Death-Neuron ➢ The central nervous system (which includes the brain and spinal cord) is made up of two basic types of cells: neurons (1) and glia (4) & (6). ➢ Glia outnumber neurons in some parts of the brain, but neurons are the key players in the brain. ➢ Neurons are information messengers. ➢ They use electrical impulses and chemical signals to transmit information between different areas of the brain, and between the brain and the rest of the nervous system. ➢ Everything we think and feel and do would be impossible without the work of neurons and their support cells, the glial cells called astrocytes (4) and oligodendrocytes (6). ➢ Neurons have three basic parts: a cell body and two extensions called an axon (5) and a dendrite (3). ➢ Within the cell body is a nucleus (2), which controls the cell’s activities and contains the cell’s genetic material. ➢ The axon looks like a long tail and transmits messages from the cell. ➢ Dendrites look like the branches of a tree and receive messages for the cell. ➢ Neurons communicate with each other by sending chemicals, called neurotransmitters, across a tiny space, called a synapse, between the axons and dendrites of adjacent neurons. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Life-and-Death-Neuron Figure: The architecture of the neuron
  3. 3. https://images.app.goo.gl/uSkUVepZ7Bi2yg6p6 There are three classes of neurons: 1.Sensory neurons carry information from the sense organs (such as the eyes and ears) to the brain. 2.Motor neurons control voluntary muscle activity such as speaking and carry messages from nerve cells in the brain to the muscles. 3.All the other neurons are called interneurons. • Scientists think that neurons are the most diverse kind of cell in the body. Within these three classes of neurons are hundreds of different types, each with specific message- carrying abilities. Source: Brain Basics: The Life and Death of a Neuron | National Institute of Neurological Disorders and Stroke. (n.d.). https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Life-and-Death-Neuron
  4. 4. ➢Glia are non-neuronal cells (i.e. not nerves) of the brain and nervous system. ➢There are a variety of subtypes of glial cells, including astrocytes, oligodendrocytes, and microglia, each of which is specialized for a particular function. ➢Neurons have axons and dendrites. However, glia, unlike neurons, cannot generate action potentials (also known as spikes, or nerve impulses). https://images.app.goo.gl/V8Z6tbKSJoKPoSXQ6 Figure: Glial cells
  5. 5. Figure: Major types of glial cells in the nervous system Central Nervous System ❑ Microglia ❑ Macroglia: • Astrocytes • Oligodendrocytes Peripheral Nervous system ❑ Schwann cells ❑ Satellite cells ❑ Enteric glial cells
  6. 6. ➢Microglia are the brain’s immune cells, serving to protect it against injury and disease. ➢Microglia identify when something has gone wrong and initiate a response that removes the toxic agent and/or clears away the dead cells. ➢Thus microglia are the brain’s protectors. ➢However, the situation may be different in neurodegenerative disorders such as Alzheimer’s disease—there is evidence that microglia may become hyperactivated, promoting neuroinflammation that can lead to the characteristic toxic protein deposits seen in Alzheimer’s (amyloid plaques and neurofibrillary tangles). ➢Finally, recent work shows that microglia play a role in the developing brain. ➢Normally, far more synapses are created than are needed, with only the strongest, most important ones surviving. ➢Microglia directly contribute to this synaptic ‘pruning’ process by eating up the synapses tagged as unnecessary.
  7. 7. Central Nervous System: Ependymal cells: Ependymal cells line the spinal cord and ventricles of the brain. They are involved in creating cerebrospinal fluid (CSF). Radial glia: Radial glial cells are progenitor cells that can generate neurons, astrocytes and oligodendrocytes.
  8. 8. ➢Astrocytes are star-shaped cells that maintain a neuron’s working environment. They do this by controlling the levels of neurotransmitter around synapses, controlling the concentrations of important ions like potassium, and providing metabolic support. ➢But astrocytes don’t just maintain the environment around synapses. An active area of research addresses how astrocytes modulate how neurons communicate. ➢Because astrocytes have the ability to sense neurotransmitter levels in synapses, and can respond by releasing molecules that directly influence neuronal activity, astrocytes are increasingly seen as important for modifying synapses.
  9. 9. ➢Oligodendrocytes provide support to axons of neurons in the central nervous system, particularly those that travel long distances within the brain. ➢They produce a fatty substance called myelin, which is wrapped around axons as a layer of insulation. ➢Similar in function to insulation layers around power cables, the myelin sheath allows electrical messages to travel faster, and gives white matter its name—the white is the myelin wrapped around axons. ➢Multiple sclerosis is caused by a loss of the myelin sheath around neurons. • Major glial cells in the brain include oligodendrocytes (blue), astrocytes (green) and microglia (maroon). • Neurons are shown in yellow, with the blue of oligodendrocytes forming the myelin sheath around the axon.
  10. 10. Schwann cells: Similar to oligodendrocytes in the central nervous system, Schwann cells myelinate neurons in the peripheral nervous system. Satellite cells: Satellite cells surround neurons in the sensory, sympathetic and parasympathetic ganglia and help regulate the chemical environment. They may contribute to chronic pain. Enteric glial cells: Enteric glial cells are found in the nerves in the digestive system.
  11. 11. o Neurotransmitters are often referred to as the body’s chemical messengers. They are the molecules used by the nervous system to transmit messages between neurons, or from neurons to muscles. o Communication between two neurons happens in the synaptic cleft (the small gap between the synapses of neurons). Here, electrical signals that have travelled along the axon are briefly converted into chemical ones through the release of neurotransmitters, causing a specific response in the receiving neuron. o A neurotransmitter influences a neuron in one of three ways: excitatory, inhibitory or modulatory. o An excitatory transmitter promotes the generation of an electrical signal called an action potential in the receiving neuron, while an inhibitory transmitter prevents it. Whether a neurotransmitter is excitatory or inhibitory depends on the receptor it binds to. https://qbi.uq.edu.au/files/27919/what-are-neurotransmitters-QBI.jpg Fig; Neurotransmitters
  12. 12. oNeuromodulators are a bit different, as they are not restricted to the synaptic cleft between two neurons, and so can affect large numbers of neurons at once. Neuromodulators therefore regulate populations of neurons, while also operating over a slower time course than excitatory and inhibitory transmitters. o Most neurotransmitters are either small amine molecules, amino acids, or neuropeptides. There are about a dozen known small-molecule neurotransmitters and more than 100 different neuropeptides, and neuroscientists are still discovering more about these chemical messengers. These chemicals and their interactions are involved in countless functions of the nervous system as well as controlling bodily functions. Fig: Neurotransmitters https://images.app.goo.gl/oe48B4zgvSo6Y9Tf6
  13. 13. o The first neurotransmitter to be discovered was a small molecule called acetylcholine. It plays a major role in the peripheral nervous system, where it is released by motor neurons and neurons of the autonomic nervous system. It also plays an important role in the central nervous system in maintaining cognitive function. Damage to the cholinergic neurons of the CNS is associated with Alzheimer disease (excitatory neurotransmitter). o Glutamate is the primary excitatory transmitter in the central nervous system. Conversely, a major inhibitory transmitter is its derivative γ- aminobutyric acid (GABA), while another inhibitory neurotransmitter is the amino acid called glycine, which is mainly found in the spinal cord. o Many neuromodulators, such as dopamine, are monoamines. There are several dopamine pathways in the brain, and this neurotransmitter is involved in many functions, including motor control, reward and reinforcement, and motivation. o Noradrenaline (or norepinephrine) is another monoamine, and is the primary neurotransmitter in the sympathetic nervous system where it works on the activity of various organs in the body to control blood pressure, heart rate, liver function and many other functions. o Neurons that use serotonin (another monoamine) project to various parts of the nervous system. As a result, serotonin is involved in functions such as sleep, memory, appetite, mood and others. It is also produced in the gastrointestinal tract in response to food. o Histamine, the last of the major monoamines, plays a role in metabolism, temperature control, regulating various hormones, and controlling the sleep-wake cycle, amongst other functions.
  14. 14. •Brain Basics: The Life and Death of a Neuron | National Institute of Neurological Disorders and Stroke, https://www.ninds.nih.gov/health-information/patient-caregiver-education/brain-basics-life-and-death- neuron#:%7E:text=Neurons%20are%20information%20messengers.,rest%20of%20the%20nervous%20system. •What are glia?. Queensland Brain Institute. https://qbi.uq.edu.au/brain-basics/brain/brain-physiology/what-are- glia •Types of glia. Queensland Brain Institute. https://qbi.uq.edu.au/brain-basics/brain/brain-physiology/types-glia •What are neurotransmitters?. Queensland Brain Institute. https://qbi.uq.edu.au/brain/brain-functions/what- are-neurotransmitters
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