BIOL 252 1st Edition Exam 1 Study Guide Lectures 1 7 The Nervous System Sensory division stimulus received Integration the brain Motor effect produced Division of the Nervous System Central nervous system o Brain and spinal cord Peripheral nervous system o Cranial nerves spinal nerves Peripheral Nervous System Somatic protects and carries us Visceral comprises guts of the body organs help us survive Divided into sensory and motor Somatic sensory visceral sensory somatic motor visceral motor ANS Neuron Structure o Soma neurosoma cell body o Dendrites receive info o Nissl bodies rough ER make proteins o Axon hillock o No centrioles do not divide o Axon o Axoplasm inside axolemma covering o Axon collateral branch early on to instruct many cells o Schwann cells help electrical signal go faster contain myelin o Axonal transport o Retrograde transport dyneins to cell body o Anterograde transport kinesins away from cell body o Lots of synaptic knobs at terminal arborization Structural Classifications of Neurons o Unipolar sensory neurons from skin and organs to spinal cord o Bipolar olfactory cells retina inner ear o Multipolar found in brain and spinal cord o Anaxonic neuron many dendrites but no axon help in visual process Neurons form Circuits o 1 PNS sensory neurons conduct signals from receptors to CNS unipolar o 2 CNS interneurons confined to CNS multipolar o 3 PNS motor neurons conduct signals from CNS to effectors such as muscles glands multipolar Organization o Bundles of neurons nerves PNS tracts CNS o Cluster of cell bodies ganglia PNS nuclei CNS Glia supportive cells o Provide physical support environmental control guidance o CNS o Oligodendrocytes large bulbous forms myelin sheath o Ependymal cuboidal produce CSF o Microglia phagocytic destroy foreign matter o Astrocytes cover brain surface and most of neuron forms capillaries Secrete nerve growth factors Form blood brain barrier Convert glucose to lactate Regulate chemical composition o PNS o Satellite surround peripheral neurons insulate and regulate control environment o Schwann enclose nerve fibers in neurilemma like oligodendrocytes of CNS Hydrophobic insulation Forms myelin sheath o Myelin o Nodes of Ranvier gaps internodes myelin covered o Layers of plasma membrane o In CNS reaches out to several nerve fibers o In PNS one wraps around each nerve fiber Electrophysiology o Extracellular Na Cl positive charge o Intracellular K proteins and HPO42 negative charge o Cell membrane has a potential difference in charge o Current flow of electrons o Resting membrane potential 70 mV o Why does RMP exist o Selective permeability plasma membrane is hydrophobic proteins and channels allow things to enter semipermeable to K o Chemical diffusion difference in concentration pushes K out o Electrical attraction repulsion created exterior repels further K movement out of cell places limit o How is it maintained o K diffusion is in dynamic equilibrium o Na K ATPase Pump Breaks apart ATP Pumps 3 Na out and 2K in Keeps amount of Na in cell to a minimum Maintains chemical difference gradients Generates electrical potential adding net 1 charge to outside Intracellular Communication Manipulation of Membrane Potentials o Local potential NT binds to channel which opens o Sodium flows into cell because of chemical and electrical gradient depolarization o Less polar closer to zero less difference i e 50 mV vs 70 mV o Na diffuses repel each other causing local potentials to move o Action potentials self propagating potentials that travel the entire length of axon o Trigger zone action potential threshold o What is threshold Voltage regulated Na gate axon vs chemical regulated Na gate soma o Must reach threshold potential to create AP o Not all local potentials produce AP s Usually requires multiple local potentials How do Action Potentials work o 1 At rest Na and K gates closed o 2 Na gates open Na enters cell K gates beginning to open depolarization o 3 Na gates close K gates open K leaves cell repolarization o 4 Na gates closed K gates closing o But not everything is back to normal o Na K pump restores proper ion balance o Na and K switched places restore chemical composition after electrical gradient o How do they spread o Opening of voltage regulated gates is self propagating all or none o Opening 1 channel so much Na moves in that membrane potential a little bit away from source changes and causes next gate to open Refractory Period o Absolute RP Na gates are either open or inactivated impossible to produce another AP o Relative RP Na gates closed by RMP is further from threshold o Must have a greater stimulus o Refraction limits frequency of Aps ensures one way communication Myelinated Axons o Leave only small patches of exposed membrane allows salutatory propagation o Voltage regulated Na gates open generating AP o Na is pushed to next node no ions to limit diffusion o Excitation of voltage regulated gates generates AP at next node o Occurs 50x faster than unmyelinated axons o Where o Peripheral parts of the body longer axons Synapses o Intercellular communication o Presynaptic neuron releases 1 type of NT synapse postsynaptic neuron has receptors ligand regulated gate o Cessation of the signal o 1 Diffusion Can leak out of synapse because no walls to contain o 2 Enzymes breakdown NT s o 3 Presynaptic neuron re uptake SSRI inhibits re uptake NT stays in synapse Pumped back into presynaptic neuron o Postsynaptic potentials o Post synaptic cell a depolarization is an EPSP Multiple required Depolarization excitatory leads to action potential o A hyperpolarization is an IPSP Can negate effects of other neurons Want to prevent neurons from having AP s Neuronal Circuits o Reverberating ex control of respiration ON OFF switch o Diverging ex control of muscles o Converging ex sensory system take info to brain Autonomic Nervous System Visceral Motor o Responsible for changing body s physiology for fight or flight response o Returning it to state of resting and digesting o Maintaining homeostasis o Temperature o Blood pressure o Blood pH o Ion balance o Somatic vs visceral o Visceral neurons innervate smooth muscle and glands even if they are found in the somatic part of the body o Ex hair standing up Visceral Reflexes o Unconscious automatic stereotypes responses to stimulation o Visceral receptor interneuron visceral effector o Ex regulation of blood pressure o Baroreceptor in carotid artery receptor o Glossopharyngeal nerve transmits signals to