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Chapter 3-11&16

Textbook Notes Chapters 3-11 & 16

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Deanna Singhal

Anatomy of the Nervous System 3102013 32900 PM GENERAL LAYOUT OF THE NERVOUS SYSTEMDIVISIONS OF THE NERVOUS SYSTEM CNS the brain and the spinal cordPNS somatic nervous system and autonomic nervous systemSomatic nervous system the part of the PNS that interacts with the external environmento Composed of afferent nerves that carry sensory signals from the skin skeletal muscles joints eyes ears and so on TO the CNS arriving o And efferent nerves that carry motor signals from the CNS to the skeletal muscles EXITING Autonomic nervous system the part of the PNS that regulates the bodys internal environmento Composed of afferent nerves that carry sensory signals from internal organs to the CNS and efferent nerves that carry motor signals from the CNS to internal organso 2 types of efferent nerves sympathetic and parasympathetic o Sympathetic nerves those autonomic motor nerves that project from the CNS in the lumbar small of the back and thoracic chest regions of the spinal cord o Parasympathetic nerves those autonomic motor nerves that project from the brain and sacral lower back region of the spinal cordo Both parasympathetic and sympathetic nerves project from the CNS and then at some point synapse on other neurons that carry the signal the rest of the way to the target organs Difference Sympathetic neurons project on secondstage neurons far from their target organs and parasympathetic neurons synapse on secondstage neurons right by their target organso Cranial nerves the 12 exceptions in the PNS that project from the brain Include purely sensory nerves Longest cranial nerves are the vagus nervesMENINGES VENTRICLES AND CEREBROSPINAL FLUID The brain and spinal cord are encased in bone and covered by three meninges protective membranes o Outer meninx is a tough membrane called the dura mater o Then the fine arachnoid membraneo Then the subarachnoid spacecontains vessels and cerebrospinal fluido Then the delicate pia mater which adheres to the surface of the CNS o Look at figure 3 page 57 for the ventricles Cerebrospinal fluid fills the subarachnoid space the central canal of the spinal cord and the cerebral ventricles of the brain o This fluid supports and cushions the braino When patients have this fluid drained they often suffer raging headaches and experience stabbing pains when they move their headso It is continuously produced by the choroid plexuses small blood vessels that protrude into the ventricles from the pia mater o The excess fluid is continuously absorbed from the subarachnoid space into large blood filled spaces dural sinuses which drain into the jugular veins of the necko Figure 4 page 58 o If the flow of cerebrospinal fluid blocked by a tumor near a channel that connect the ventricles the result is hydrocephalusa buildup of fluid that causes the walls of the ventricles and the brain to expando This can be treated by draining the excess fluid and removing the obstructionBLOOD BRAIN BARRIERBloodbrain barrier the mechanism that keeps certain toxic substances in the blood from passing into brain tissue o A tightly packed wall of blood cellso The degree to which recreational and therapeutic drugs can effect brain activity depends on how easily they can pass through this barrier CELLS OF THE NERVOUS SYSTEMANATOMY OF NEURONS Neurons cells that are specialized for the reception conduction and transmission of electrochemical signals Figure 5 page 59Figure 6 page 60Cell membranethe neuron cell membrane is made up of the lipid bilayerin this are several embedded proteins some are channel and some are signalo Channel proteins regulate the passing of certain molecules and signal proteins transfer a signal to the inside of the neuron when particular molecules bind to the outside of the membrane Classes of neuronsmultipolar unipolar bipolar and interneurons o Multipolar a neuron with more than two processes extending from its cell body o Unipolar a neuron with one process extending from its cell body o Bipolar a neuron with two processes extending from its cell bodyo Interneurons neurons with a short axon or no axon at all function is to integrate the neural activity within a single brain structure not to conduct signals between structures o Figure 8 page 62Neurons and Neuroanatomical Structurethere are two kinds of neural structures in the nervous system those made up of mostly cell bodies and those made up of mostly axons o In the CNS clusters of cell bodies are nucleiin the PNS they are called gangliao In the CNS bundles of axons are called tractsin the PNS they are called nerves GLIAL CELLSThey second cell type that is found in the nervous system There are 4 main types of glial cells oligodendrocytes Schwann cells astrocytes and microgliaOligodendrocytes glial cells with extensions that wrap around the axons of some neurons in the CNSo Are made up of myelin and form myelin sheaths that increase the speed and efficiency of axon conduction Schwann cells the glial cells that form myelin sheaths in the PNS and promote the regeneration of damaged axons Figure 9 page 62Microglia the smallest glial cells respond to injury or disease by multiplying engulfing cellular debris and triggering inflammatory responses Astrocytes the largest glial cellso Have been shown to send and receive signals from neurons and other glial cells to control the establishment and maintenance of synapses between neurons to modulate neural activity to maintain the function of axons and to participate in glial circuits
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