1 Know all the neuroglia and what they do Neuroglia of the CNS Astrocytes Form foot processes which cover surfaces of blood vessels neurons and pia mater Extensive cytoskeleton of microfilaments which allows for supporting framework in blood vessels and neurons Release chemicals that regulate extracellular composition of the brain and promote tight junctions o Blood brain Barrier protects neurons from toxic substances in the blood by determining which substances can pass from Almost all injuries to CNS tissue induce reactive astrocytosis wall off injury site and help limit spread of inflammation Ependymal Cells Microglia Line the cavities of the brain and the central canal of the spinal cord Specialized ependymal cells and blood vessels form the Choroid plexus located w in certain regions of the cavities secretes cerebrospinal fluid cilia helps to move the cerebrospinal fluid Neuroglia in the CNS that become mobile in phagocytic in response to inflammation Phagocytize foreign substances that invade the CNS SPECIALIZED MACROPHAGE Oligodendrocytes Cytoplasmic extensions that can surround axons If the extensions wrap around the axons many times a myelin sheath is formed can wrap around MULTIPLE axons Neuroglia of the PNS Schwann and Satellite Cells Schwann wrap around axons each Schwann cell form a myelin sheath around a portion of only one axon Satellite surround neuron cell bodies in sensory and autonomic ganglia provide support and nutrients absorbs heavy metal poisons 2 Functions of each system nervous and endocrine Functions of the Nervous System a Maintaining homeostasis trillions of cells do not work separately but instead must work together b Receiving sensory input sensory receptors must monitor external and internal stimuli including pH levels temp hearing pain blood pressure some are processed at unconscious and conscious level c Integrating information brain and spinal cord process sensory input initiate responses input can produce immediate delayed or no response d Controlling muscles and glands skeletal muscle is normally only stimulated by nervous some smooth and cardiac muscle is controlled by nervous nervous controls secretions from many glands e Establishing and maintaining mental activity brain is center for mental activity including emotions memory thinking and consciousness The endocrine system effects Uses hormones produced by endocrine structures to produce processes Among other things they Endocrine hormones control a variety of physiological o Balance the composition and volume of body fluids o Regulate metabolism and energy production o Direct the rate and timing of growth and development o Exert emergency control during physical and mental o Oversee reproductive mechanisms stress trauma starvation hemorrhage Hormone secretion is regulated by signals from the nervous system chemical changes in the blood and other hormones 3 Know the purpose of the myelin sheath and where it is a Located around the axon protects and insulates speeds transmission functions in repair of axons not continuous interruptions are nodes of Ranvier b Myelin protects and electrically insulate axons from one another c Action potential travel more rapidly along myelin d Myelinated sheath is NOT continuous e Nodes of Ranvier interruptions in the Myelin Sheath f Completion of development of myelin sheaths at 1 yr g Degeneration of myelin sheaths occurs in multiple sclerosis and some cases of diabetes mellitus h Unmyelinated axons rest in invaginations of Schwann cells or oligodencrcytes GRAY matter i Gray Matter i Neuron cell bodies and their dendrite w little myelin ii In CNS gray matter on brain is cortex deeper w in the brain are nuclei In PNS cluster of neuron cells is ganglion iii j White Matter i White matter of the CNS forms nerves tracts ii Bundles of axons w their myelin sheaths k In brain gray is outer cortex as well as inner nuclei white is deeper l In spinal cord white is outer gray is deeper 4 Permeability of cell nerve cell know what s on inside outside a Na is on outside more K is on inside more proteins cannot easily diffuse out Cl is repelled by proteins inside the cell b When gated ions open or close they change the permeability of the cell 5 What happens when you change equilibrium of the membrane a At equilibrium there is very little movement of K or other ions across plasma membrane 6 Graded potential occurs first then a Must reach threshold b Then action potential happens Action Potential Frequency of AP produced per unit of time in response to a stimulus directly proportional to stimulus strength and size of graded potential c Sub threshold stimulus does not cause a graded potential to reach threshold thus is not great enough to initiate action potential d Threshold stimulus produces a graded potential just strong enough to reach threshold and cause the production of a single action potential e Maximal stimulus just strong enough to produce a maximum f Submaximal stimulus includes all stimuli between threshold frequency of action potentials and maximal stimulus strength g Supramaximal stimulus any stimulus stronger than a maximal stimulus do not produce greater frequency of action potential than maximal 7 Must know characteristic of graded potential a change in membrane potential localized to one area b Can result from and occur often in cell body or dendrites i Chemical signals binding to receptors ii Changes in charge across membrane iii Mechanical stimulation iv Temp Changes v Spontaneous opening of ion channels Magnitude of graded potentials can vary depending on stimulus or strength 8 Know how summation happens a occurs when the effects from one graded potential add to another graded potential and can result in an action potential Spread over the plasma in decremental fashion like teachers voice in large lecture hall rapidly decreases as spreads over surface a Depolarization moves from resting state to more positive as long as inactivation gates are closed further depolarization cannot occur 9 Excitatory vs inhibitory b Repolarization afterpotential slight hyperpolarization returns toward resting to more negative may get c Depolarizing graded potentials STIMULATORY can produce AP but hyperpolarizing INHIBATORY can never reach threshold to produce and AP 10 On which point of hyperpolarization or depolar what is going in or out The membrane potential can become more neg or pos a Depolarization when the membrane potential become more POSITIVE and movement is
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