Ch. 12 Review/Study guide
Ch. 12 Review/Study guide BIOL 3455.001
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This 6 page Study Guide was uploaded by Filza on Friday November 6, 2015. The Study Guide belongs to BIOL 3455.001 at University of Texas at Dallas taught by Dr. Ramirez in Summer 2015. Since its upload, it has received 77 views. For similar materials see Anatomy and Physiology in Biology at University of Texas at Dallas.
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Date Created: 11/06/15
Ch. 12 Review/Study guide CNS brain & spinal cord; site of higher function ex: learning, intelligence, emotion, memory • integrating, processing, coordinating sensory data & motor commands PNS deliver sensory info to CNS & carry motor commands to peripheral tissues/systems • afferent division bring sensory info to CNS from receptors • efferent division carry motor commands from CNS to effectors & include somatic & autonomic divisions somatic nervous system (SNS) voluntary contractions/skeletal muscles; conscious control autonomic nervous system (ANS) aka visceral motor system involuntary control • sympathetic division accelerate heart rate, inc. BP & adrenaline, “fight or flight” response • parasympathetic division slows heart rate, low BP, “rest” response receptors detect changes in environment or respond to stimuli effector target organ that responds by doing something CNS PNS Somatic Autonomic sympathetic parasympathetic neuroglia aka glial cells; are supporting cells; preserve physical/biochemical structure of neural tissue • provide supportive framework for neural tissue • act as phagocytes • help regulate composition of interstitial fluid • outnumber neurons CNS Neuroglia A) Ependymal cells produce, monitor, circulate CSF line central canal & ventricles ependyma simple cuboidal to columnar epithelium • ependymocytes contain cilia/microvilli that help in circulation of CSF • tanycytes nonciliated w/microvilli on surface transport substances btw CSF & brain B) Astrocytes largest, most numerous in CNS maintain bloodbrain barrier secrete chemicals that maintain permeability of capillary endothelial cells structural support regulate ion/nutrient/gas concentrations absorb/recycle neurotransmitters repair damaged neural tissue C) Oligodendrocytes wrap axons with myelin sheath tie clusters of axons together white matter made up of myelinated axons gray matter made up of unmyelinated axons D) Microglia phagocytic cells (engulf waste, pathogens, etc.) smallest/least numerous PNS Neuroglia A) ganglia cell bodies of neurons that are clustered in masses B) satellite cells regulate environment around neurons C) Schwann cells aka neurilemma cells form myelin sheath around axons • Parts of neuron axon hillock connects to axon from cell body Nissl bodies regions stain darkly and contain free ribosomes and clusters of RER (rough endoplasmic reticulum) telodendria terminal branches synaptic knobs aka synaptic terminals perikaryon cytoplasm surrounding nucleus axolemma specialized portion of plasma membrane that surround axoplasm neuromuscular junction synapse btw neuron and muscle cell neuroglandular junction neuron control activity of gland cell presynaptic cell sends message and includes axon terminal postsynaptic cell receives message Structural classification of neurons A. anaxonic neurons many small dendrites & no axon located in brain & special sense organs B. bipolar neurons relay info about sight, smell, hearing from receptor cells to other neurons small and fairly rare C. unipolar neuron aka pseudounipolar neuron most sensory neurons are unipolar longest axons carry sensation from tip of toes to spinal cord D. multipolar neuron 2 or more dendrites & single axon (ex: motor neuron) most common neurons in CNS Functional Classification of neurons 1) Sensory neuron afferent neuron is unipolar deliver sensory info to CNS sensory neuron monitor outside world & our position w/in it visceral sensory neuron monitor internal conditions • interoceptors monitor digestive/respiratory/cardiovascular/urinary/reproduc. systems ;and sensation of pain/deep pressure • exteroceptors info of external environment in form of touch, temp., pressure, taste, smell, sight, equilibrium, hearing • proprioceptors monitor position/movement of skeletal system 2) Motor neuron efferent neuron; carry signal from CNS to peripheral effectors 3) Interneuron distribute sensory info & coordinate motor activity; also part of higher functions • neural response to injury: schwann cells play part in repairing damaged nerves in PNS Wallerian degeneration axon distal to injury site degenerates & macrophages migrate into area to clean up debris • gated & nongated channels active channels are gated channels open/close in response to specific stimuli • 3 classes of gated channels: 1) chemically (ligand) gated 2) voltagegated 3)mechanically gated chemically gated channels most abundant on dendrites/cell body of neuron voltagegated channels abundant on axon mechanically gated channels located on dendrites of sensory neurons mechanically gated channels open in response to distortion of membrane passive channels are leak channels are always open transmembrane potential aka membrane potential electrochemical gradient sum of chemical & electrical forces acting on ion across plasma membrane equilibrium potential no net movement of particular ion across membrane NaK pump exchange 2 extracellular K+ ions for 3 intracellular Na+ ions & one molecule of ATP is broken down to ADP resting membrane potential unstimulated membrane potential graded potential localized change in resting mem. potential; decrease w/distance from stimulus • generation of action potentials: 1. depolarization to threshold 2. activation of gated Na+ channels & rapid depolarization 3. inactivation of gated Na+ channels & activation of gated K+ channels 4. closing of gated K+ channels refractory period membrane doesn ’t respond normally to additional depolarizing stimuli from time action potential begins until normal resting mem. potential has stabilized absolute refractory period membrane can ’t respond to further stimulation from moment Na+ channels open at threshold until Na+ channel inactivation ends (first part of refractory period) relative refractory period begins when Na+ channels regain normal resting condition & continues until membrane potential stabilizes at resting levels depolarization results from influx of Na+ & repolarization involve loss of K+ • Continuous propagation along unmyelinated axon: ac. potential move across surface of membrane in series of tiny steps 1. as action potential develops at initial segment, mem. potential here depolarize to +30 mV 2. as Na+ ions entering at initial segment spread away from open gated channels, graded depolarization brings 2nd segment to threshold 3. action potential occurs in 2nd segment while 1st segment begins repolarization 4. as Na+ ions entering at 2nd segment spread laterally, graded depolarization brings membrane in 3rd segment to threshold & cycle is repeated (Martini, Nath, & Bartholomew 410) • Saltatory propagation along myelinated axon 1. action potential occurs at initial segment 2. local current produces graded depolarization that brings axolemma at next node to threshold 3. action potential develops at node (2nd segment) 4. local current produces graded depolarization that brings axolemma at node (3rd segment) to threshold larger axon diameter = lower resistance to ion movement; myelinated = faster speed 1. Type A fibers largest myelinated axons (420 μm) carry ac. potentials at speed up to 120 m/s carry sensory info (position, balance, light touch/pressure) to CNS 2. Type B fibers smaller myelinated axons (24 μ m) 18 m/s carry info to and from CNS temp, pain, general touch/pressure carry instruction to smooth/cardiac muscle, glands, peripheral effectors 3. Type C fibers unmyelinated (less than 2 μm) 1 m/s same functions as Type B fibers most sensory info received from Type C fibers • Action potentials v. Graded potentials (Martini, Nath, & Bartholomew 412) chemical synapse involves neurotransmitter most abundant synapse no direct contact btw cells excitatory neurotransmitters cause depolarization & promote generation of ac. potentials inhibitory neurotransmitters cause hyperpolarization & suppress generation of ac. potentials effect of neurotransmitter on postsynaptic membrane depends on properties of receptor, not on nature of neurotransmitter • Cholinergic synapse (this type of synapse releases ACh) events: 2. action potential arrives & depolarizes axon terminal 3. extracellular Ca+ ions enter axon terminal triggering exocytosis of ACh 4. ACh binds to receptors & depolarizes the postsynaptic membrane • ACh receptors are chemically gated channels —> inc. permeability to Na+ • depolarization is graded potential 4. ACh is removed by AChE • depolarization ends as ACh broken down into acetate & choline by AChE (hydrolysis) • axon terminal reabsorbs choline from synaptic cleft & use it to resynthesize ACh (Martini, Nath, & Bartholomew 416 categories of neurotransmitters: biogenic amines, amino acids, neuropeptides, dissolved gases • norepinephrine (NE) in brain and ANS adrenergic synapse release NE excitatory, depolarizing effect on postsynaptic membrane • dopamine CNS neurotransmitter either inhibitory (control movements) or excitatory effects Parkinson ’s disease rigidity/stiffness resulting from damaged dopamineproducing neurons cocaine inhibit removal of dopamine from some synapses —> result in “high” • serotonin effect attention & emotional states antidepressant drugs inhibit reabsorption of serotonin by axon terminals —> relieve symptoms of depression • GABA inhibitory effect; 20% of synapses release GABA functions incompletely understood neuromodulator alter rate of neurotransmitter release by the presynaptic neuron or change neuromodulator act by binding to receptors in pre/postsynaptic membranes & activating cytoplasmic enzymes neuromodulators called opioids similar to opium 4 classes of opioids: 1) endorphins 2) enkephalins 3) endomorphins 4) dynorphins neurotransmitters/neuromodulators fall into 3 functional groups: • compounds that have direct effect on mem. potential (open/close gated ion channels; ionotropic effect; ex: ACh) • compounds that have indirect effect on mem. potential (metabotropic) • lipidsoluble gases that exert their effects inside cell ionotropic effect when neurotransmitters alter ion movement across membrane metabotropic effect involve changes in metabolic activity of postsynaptic cell 2. Also know the spinal and cranial nerves. Works Cited Martini, Frederic, Judi Lindsley Nath, and Edwin Bartholomew. Fundamentals of Anatomy & Physiology. Tenth ed. San Francisco: Pearson Education, 2015. Print.
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