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UNIIT 8: Nervous SystemBy the end of this unit you should be able to:1.Name the major anatomical structures of the nervous system.2.Describe the function of major brain structures in the telencephalon, diencephalon,mesencephalon, metencephalon & myelencephalon.3.Explain the structural organization and function of the autonomic nervous system (ANS).4.Identify the major neurotransmitters families in the CNS and ANS.5.Identify all of the components of a reflex arc.Required Readings-Chapter 8: Pages 206-233 (stop at Section 8.5)-Chapter 9: Pages 243-261Nervous System Overview:-Divided into central nervous system (CNS) and peripheral nervous system (PNS)-CNS: Consists of brain and spinal cord-PNS: Made up of cranial nerves that arise from brain and spinal nerves that arise from spinalcord-Action potential or nerve impulses transmitted from CNS to PNSBrain Facts:-Gray matter forms the cortex and deep nuclei; white matter is deep forming tracts
-Adult brain has 100 billion neurons and weighs about 1.5 kg (3−5 pounds).-Adult brain receives 15% of the total blood flow to the body per minute.-Scientists have demonstrated neurogenesis (the formation of new brain cells from neural stemcells) in adult brains is within the subgranular zone of the hippocampus and subventricular zoneof the lateral ventriclesCNS-Composed of brain and spinal cord-Receives input from sensory neurons and directs activity of motor neurons that innervatemuscles and glands-Brain is composed of neurons and support cells-Sensory peripheral nerves send info to the brainbrain integrates the inforesponse generated-Response can take form of motor neurons responses or higher brain functions like: emotions,memory, learning and perceptions-Spinal cord is connected caudally and it connects spinal nerves to the brain-Ascending tracts bring sensory info from periphery to brain-Descending tracts sends motor nerve impulses down spinal cord-Spinal cord also performs some info integration in form of reflex arcs
Brain Development:-20 days after conception: brain develops from embryonic ectodernal neural tube-From ectoderm comes a groove that will become neural tube-The cavity becomes a fluid filled ventricular system and walls develop into neurons of the brain-Between neural tube and developing epidermis, a neural crest formsthis becomes PNS ganglia-Week 4: three distinct swellings are soon on neural tube:oProsencephalon (forebrain)oMesencephalon (midbrain)oRhombencephalon (hindbrain)-Week 5: further differentiate into 5 regionsoTelecephalon (forebrain)will be cerebral hemispheres in adultoDiencephalon (forebrain)will be thalamus & hypothalamus in adultoMesencephalon (midbrain)will be midbrain in adultoMetencephalon (hindbrain)will be pons & cerebellum in adultoMyelencephalon (hindbrain)will be medulla oblangata in adult-In humans, the telencephalon develops at an accelerated rate resulting in cerebral hemispherescovering the thalamus, hypothalamus, and part of the pons and cerebellum