BIOL 252 1st EditionExam # 1 Study Guide Lectures: 1 - 7The Nervous System- Sensory division: stimulus received- Integration: the brain- Motor: effect producedDivision of the Nervous System-- Central nervous systemo Brain and spinal cord- Peripheral nervous systemo Cranial nerves, spinal nervesPeripheral 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 Structureo Soma (neurosoma) = cell bodyo Dendrites = receive infoo Nissl bodies = rough ER, make proteinso Axon hillocko No centrioles – do not divideo Axono Axoplasm-inside; axolemma-coveringo Axon collateral: branch early on to instruct many cellso Schwann cells = help electrical signal go faster, contain myelino Axonal transporto Retrograde transport: dyneins (to cell body)o Anterograde transport: kinesins (away from cell body)o Lots of synaptic knobs at terminal arborizationStructural Classifications of Neuronso Unipolar: sensory neurons from skin and organs to spinal cordo Bipolar: olfactory cells, retina, inner earo Multipolar: found in brain and spinal cordo Anaxonic neuron: many dendrites but no axon, help in visual processNeurons form Circuitso 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)Organizationo 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, guidanceo CNSo Oligodendrocytes: large, bulbous, forms myelin sheatho Ependymal: cuboidal, produce CSFo Microglia: phagocytic, destroy foreign mattero Astrocytes: cover brain surface and most of neuron, forms capillaries Secrete nerve growth factors Form blood brain barrier Convert glucose to lactate Regulate chemical compositiono PNSo Satellite: surround peripheral neurons, insulate and regulate; control environmento Schwann: enclose nerve fibers in neurilemma (like oligodendrocytes of CNS) Hydrophobic insulation Forms myelin sheatho Myelino Nodes of Ranvier (gaps) & internodes (myelin covered)o Layers of plasma membraneo In CNS-reaches out to several nerve fiberso In PNS-one wraps around each nerve fiberElectrophysiologyo Extracellular: Na+, Cl-  positive chargeo Intracellular: K+, proteins and HPO42-  negative chargeo Cell membrane has a potential (difference in charge) o Current = flow of electronso Resting membrane potential = -70 mVo 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 Potentialso Local potential: NT binds to channel, which openso 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 mVo Na+ diffuses (repel each other) causing local potentials to moveo Action potentials: self-propagating potentials that travel the entire length of axono 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 APo Not all local potentials produce AP’s  Usually requires multiple local potentialsHow do Action Potentials work?o 1. At rest, Na+ and K+ gates closedo 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 balanceo Na+ and K+ switched places, restore chemical composition after electrical gradiento 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 openRefractory Periodo 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 thresholdo Must have a greater stimulus o Refraction limits frequency of Aps, ensures one way communicationMyelinated Axonso Leave only small patches of exposed membrane, allows “salutatory propagation”o Voltage-regulated Na+ gates open, generating APo Na+ is pushed to next node; no ions to limit diffusiono Excitation of voltage-regulated gates generates AP at next nodeo Occurs 50x faster than unmyelinated axonso Where?o Peripheral parts of the body, longer axonsSynapseso Intercellular communicationo Presynaptic neuron (releases 1 type of NT)  synapse  postsynaptic neuron (has receptors = ligand regulated gate)o Cessation of the signalo 1. Diffusion Can leak out of synapse because no walls to containo 2. Enzymes breakdown NT’so 3. Presynaptic neuron = re-uptake SSRI: inhibits re-uptake, NT stays in synapse Pumped back into presynaptic neurono Postsynaptic potentialso Post synaptic cell, a depolarization is an EPSP Multiple required Depolarization = excitatory, leads to action potentialo A hyperpolarization is an IPSP Can negate effects of other neurons Want to prevent neurons from having AP’sNeuronal Circuitso Reverberating: ex: control of respiration, ON/OFF switcho Diverging: ex: control of muscleso Converging: ex: sensory system (take info to brain)Autonomic Nervous System (Visceral Motor)o Responsible for changing body’s physiology for fight or flight responseo Returning it to state of resting and digestingo Maintaining homeostasis:o Temperatureo Blood pressureo Blood pHo Ion balanceo Somatic vs. visceralo Visceral neurons innervate smooth muscle and glands even if they are found in the somatic part of the bodyo