Notes for Chapter 15 Nervous System .docx

Notes for Chapter 15 Nervous System .docx - Nervous System...

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The Neurons Neuron are basic unit of the Nervous system. Transmits signal via electric or chemical. Does not divide thru mitosis; always at the G0 of the interphase. Neurons cannot store glucose or oxygen. Glucose/O2 is brought to the neurons by facilitated diffusion. Parts of Neurons - Dendrites - Projection on the cell body that receives electric signal from the other cells or neurons. Cannot initiate action potential Nervous System Central Nervous System Made of interneurons only Peripheral Nervous System No interneurons, has motor (efferent) and Sensory (afferent) neurons Autonomic Parasympathet ic Sympathetic Somatic
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- Axon Hillock – Connects the cell body to the axon. They are long conductive body that carries nerve imuplses away from the cell body. Generates the action potential. - Axon Terminal = Axon Bouton = Presynaptic Bouton – Projection at the end of the neuron. Transmits signal to postsynaptic cells (ex. Muscle cells) or other neurons. Types of Neurons - Motor Neurons – transmits impulses away from the CNS. It transmits signals from that begins in the CNS and exit the ventral side of the spinal cord to an effector organ or another neuron. It follows the Efferent Pathway. - Sensory Neurons – Follows the afferent pathway, which receives signal from an effector organ or tissue to CNS through the dorsal side of the spinal cord. - Interneurons – transmits signal to other neurons Neuroglia Support Cells of the Nervous System Support cells in the CNS - Astrocytes – most abundant of the glial cells. Carries nutrients from the blood vessels and establish proper concentration outside the neuron. Support neuron physically. See pg 450 - Oligodendrocytes – Deposits myelin sheath around the cell. - Ependymal cells – lines the spinal cord and part of the brain. They are involved in the Cerebrospinal Fluid (CSF) production and movement. - Mircoglia Cells – removes debris from the CNS thru phagocytosis. Support cells in the PNS - Satellite cells provide physical support and create a protective layer around the cell and also give the cell the nutrients they need - Schwann cells synthesize myelin around the axon of the neuron. Propagation of Action potential The neuron is a specialized cell that is capable of generating an action potential on the cell membrane of the axon hillock. It does this by using special voltage-gated ion channels that respond to changes in voltage across the membrane of the cell. There are two types of voltage-gated channels, one for sodium and one for potassium. At the resting membrane potential of about -70 millivolts, these two voltage-gated ion channels are closed. During stimulation, when the stimulus has reached or exceeded the threshold value of around -45 millivolts, this change in voltage will signal the voltage-gated sodium channels to open up. An influx of sodium ions down their electrochemical gradient will cause the inside of the
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