Chapter 14 Notes
Chapter 14 Notes 80887 - BIOL 3150 - 001
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This 7 page Class Notes was uploaded by Abigail Towe on Thursday October 1, 2015. The Class Notes belongs to 80887 - BIOL 3150 - 001 at Clemson University taught by Tamara L. McNutt-Scott in Fall 2015. Since its upload, it has received 29 views. For similar materials see Functional Human Anatomy in Biological Sciences at Clemson University.
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Date Created: 10/01/15
Chapter 14 Nervous Tissue 0 Structural organization CNS amp PNS o CNS brain spinal cord 0 PNS cranial nerves spinal nerves ganglia 0 NS together sensory motor forms 3 general functions 1 PNS receptors collect information and send to CNS sensory receptors sensory input 2 CNS processes information to determine if there should be a response 3 If response then CNS initiates by sending signal to PNS to command effectors motor output 0 Functional Organization sensory amp motor 0 sensory information in somatic sensory visceral sensory 0 motor information out somatic motor autonomic motor I somatic voluntary I autonomic involuntary Cytology of Nervous Tissue o neurons basic functional unit 0 excitable cells that start and transmit nerve impulses o glial cells neuroglia non excitable cells support and protect neurons found in CNS amp PNS smaller than neurons capable of mitosis unlike neurons assist neurons in their function protects and nourish neurons provides framework for nervous tissue little connective tissue present mostly glial cells far outnumber neurons glial cells are different within CNS and PNS because size intracellular organization and specific cytoplasmic processes change between the two systems OOOOOOOOOOO c Mlcmgllal cell CNS Glial Cells Central canal of spinal cord PNS Gllal Coll mam at 39i A Lin t 1 Astrocytes CNS a b c most abundant perivascular feet CLING to neurons amp capillaries regulates tissue fluid in brain regulates what flows out of blood vessels i blood brain barrier has cytoskeletal elements robust structure When neurons are damaged astrocytes fill in the space but don t perform the functions that the neuron did less need for connective tissue when neurons are young astrocytes help to guide the neurons in building synapses 2 Ependymal cells CNS a b C epithelial cells that are ciliated lines cavities of brain and spinal cord i cilia helps move cerebrospinal fluid through these areas forms fibrous network because the processes of the ependymal cells branch extensively to make contact with other glial cells d choroid plexus production of cerebrospinal fluid microglia CNS a ramification many branches b when activated microglia become macrophages to remove what doesn t belong i important because neural tissue doesn t have immune response c small cells with thorny processes that monitor nearby neurons health Oligodendrocytes PNS a large cells with bulbous body cytoplasmic processes ensheath portions of multiple axons myelin sheath b need fluorescents to view these cells Satellite cells PNS a satellite cells basically astrocytes in the PNS b flat cells that physically separate ganglion cells from interstitial fluid c regulate nutrients and wastes and removal of those wastes i between neurons and the environment Schwann Cells PNS a neurolemmocytes b Neurolemmocytes are used to wrap around to form myelin sheath around PNS axons c They are also able to act as phagocytic cells to remove dead cells d helps in regeneration e Oligodendrocytes do not offer regeneration only function to form myelin sheath Neurons Neurons are highly specialized communication cells 0 generate ATP 0 love glucose as fuel source 0 amitotic do not have centrioles so they cannot divide Structure Nissl bodies chromatic philic substances they are in a condense area where we see rough ER and ribosomes pigment inclusions as neurons get older they get darker in color retrograde toward the cell body anterograde away from cell body Anaxonic neurons neurons that do not have an axon ONLY HAVE DENDRITES not common only found in CNS no idea of functionality Neuron Classification 0 when in doubt choose multipolar most common 0 bipolar axon dendrites o sensory neurons information in 0 motor neurons information out o interneuron serve to connect sensory and motor I aids in forming reflexes o sensory and motor are almost always multipolar Mvelination of Axons Why only myelination of axons 0 has significant impact on nerves serves as insulation 0 it wraps around until it looks stacked myelin sheath 0 the organelles are located in the outer layers no change in voltage can occur where myelination is present 0 There is a change in voltage across the plasma membrane because there is high sodium on the outside of the cell but low on the inside The charge difference gt voltage occurs Mvelination in CNS and PNS o in the CNS oligodendrocytes they wrap the axon but in small portions 1 mm sized portions individually wraps one neurolemmocyte on one axon o in PNS schwann cells neurolemmocytes myelinates a 1 mm area on axon o saltatory conduction wherever there is myelination no chance in voltage so the signal pops through each node super fast Unmvelinated axons 0 much slower conduction because the signal must travel through the entire length and change voltage a lot Svnaptic Communication 1 electrical infrequent a gap junctions are utilized b message passes directly from one cell to the next c so there is a local flow of current gt which is the movement of charge ion d no synaptic delay 2 chemical more frequent most numerous uses nervous tissue there is a synaptic delay very precise sequence of events so that the rate of nerve impulse conduction are only influenced by 2 factors 1 axon s diameter 2 myelin sheath present or not a present faster b absent slow e there is a synaptic delay 9065 o synaptic delay 0 occurs in a chemical synpase because it takes time for us to relase the neurotransmission diffuse and bind to the channel on the post synaptic membrane Events of Chemical Svnapse 1 nerve impulse that flows down axon gt terminal region of axon gt synaptic knob 2 arrival of nerve impulse gt causes increase in calcium ion movement into synaptic knob a this is because it s a voltageregulated calcium ion channel 3 when calcium ions enter the synaptic knob synaptic vesicles move also to bind to the side of membrane a then neurotransmitters that are inside the vesicles are released into synaptic cleft by exocytosis 4 the neurotransmitters diffuse across synaptic cleft to the plasma membrane of the postsynaptic cell 5 neurotransmitters then bind to protein receptors of postsynaptic cell gt causing ion gates to open 6 influx of sodium ions moves into postsynaptic cells while gates are open gt changes charge across membrane Summary 1 nerve impulse gt synaptic knob gt increase in calcium ions into synaptic knob 2 synaptic vesicles move in and attach to plasma membrane gt they release neurotransmitters 3 neurotransmitters diffuse across syanptic cleft toward the plasma membrane of postsynaptic cell 4 neurotransmitters bind to specific protein receptors gt ions gates open gt sodium ions move in gt charge chances across membrane Neural Integration and Neuronal Pools 0 neuronal pools complex patterns that neurons are arranged in o 4 types 0 converging circuit I many inputs into single output concentrates signal 0 this creates strong stimulation or inhibition 0 diverging circuit I one input into multiple outputs amplifying circuit 0 amplifies the information o Reverberating circuit I continuously runs until inhibitory signal that will stop the signal or synaptic fatigue when you run out of neurotransmittors or gets to levels so low that it can t communicate with the subsequent cell I it oscillates into itself o parallelafterdischarge circuit I single output but the pathway to getting there is a burst of impulses 0 one input in but 5 out through the single output because there are many input neurons in the pathway to get to output I responsible for higher level thinking Axon Regeneration 0 when you have trauma in the peripheral nervous system skeletal muscle fiber neurolemma schwann cells 0 the end of the axon seals itself out and swells up and anything distal to this breaks down 0 the hope is that the endomysium stays in tact and that there is some aspect of schwann cells left that survived I with the endomysium and schwann cells it forms a regeneration tube to help the axon regenerationreconnect o limits I more damage the harder it is to repair I distance 0 if close it s likely to occur 0 but far away as in 34 mm will decrease probability I and have some schwann cells to release nerve growth cells to help reach 0 In CNS 0 regeneration is limited 0 because no release of nerve growth factors 0 cellular density is greater and tends to complicate regrowth o higher cellular density increases chance of connecting to wrong axon so it tries to use a different pathway or retrain another area of perform 0 when there is damage there are astrocytes and connective tissue coverings that may form scar tissue 0 this scar tissue obstructs pathway for axon regrowth NerveTracts ln PNS a bundle of parallel axons nerve ln CNS a bundle of parallel axons tract Nervetract is surrounded by 3 consecutive connective tissue 0 endoneurium wraps around axon O perineurium wraps around fascicle o epineurium wraps around the entire collect c There is vasculature in each wrapping Sensory neuron O afferent motor neurons 0 efferent mixed 0 some neurons carry motor but some other ones carry sensory neurons
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