NUR 0012 Lecture 28 Ch. 11 Fundamentals of the Nervous System ContinuedOutline of Last LectureI. Ch. 11 nervous systemA. 3 basic parts1. Integration2. Afferent input3. Efferent outputB. Divisions of nervous system1. CNS2. PNS3. ANSC. Neurological cellsD. Salutatory conductionOutline of Current LectureI. Ch. 11 nervous system cont.A. Salutatory conductionB. Neurons have 3 major partsC. Tracts vs. nervesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.D. Myelinated vs. unmyelinated neuronsE. Neurons can be classified structurally and functionallyF. 3 basic principles applied to electricityG. Concentration differences across cell membranesH. Movements through cell membraneI. Resting membrane potentialJ. Electrically excitable cellsCurrent LectureI. Ch. 11 nervous system cont.A. Salutatory conduction (review): AP’s move in a jumping motion along myelinated axons much faster than in unmyelinated axons, know the diagramB. Most neurons have 3 major parts1. Dendrites: receptive regionsa. receive axons of other neurons, conduct electrical potentials toward cell body2. Cell body: soma, biosynthetic center and receptive regiona. Contain a large nucleus, lots of RER, golgi apparatus, and prominent nucleolusb. Don’t have centrioles: reflects amitotic naturec. Ganglia: cell bodies outside CNSd. Have extensions of their cell membranes that form the dendrites and axons3. Axon: impulse generating and conducting regiona. Normally, a single axon forms from an enlarged region in cells body called axon hillock1) AP arise from hillock and travel down the axolemmab. Can vary in length from a few mm to up to 1 mc. Terminal buttons (presynaptic terminal, synaptic knobs): branched terminal fibers of axons, can be as many as 10,000C. Tracts vs. nerves1. Tracts: bundles of neuron cell processes (axons) in CNS2. Nerves: bundles of neuron cell processes (axons) in PNSD. Myelinated vs. unmyelinated neurons1. Myelinateda. Axons have a lipid sheath created by oligodendrocytes or Schwann cellsb. Nodes of Ranvier, salutatory conductionc. Speed of generation much greater (5-30m/s)d. In general, longer axons tend to be myelinated and short ones not2. Unmyelinateda. No myelin sheath surrounding axonb. Conduction much slower (0.5-2m/s)E. Neurons can be classified structurally and functionally 1. Structural: found in different parts of the nervous systema. Multipolar: have 3 or more processes (axon and multiple dendrites)b. Bipolar: have an axon and a dendrite, rare, found in some special sensory organs (olfactory mucosa, eye, ear)c. Unipolar: have a cell body with short processes that can’t be classified as dendrites or axons, found mainly in PNS, common only in dorsal root ganglia of the spinal cord and sensory ganglia of cranial nerves2. Functional: depend on which type of info they carrya. Afferent (sensory): transmit pulses from receptors into CNSb. Efferent (motor): transmit impulses from CNS to effectorsc. Interneurons (association): found in CNS, transmit impulses between sensory and motor neuronsF. 3 basic principles applied to electricity1. Voltage: potential energy generated by keeping positive and negative chargesseparate2. Current: when charge is allowed to flow3. Resistance: hindrance of flow of charges4. Can be condensed into Ohm’s Law: I=V/Ra. I=currentb. V=voltagec. R=resistanced. Higher the resistance the less the flow of currente. Decreasing resistance will allow charges to travel much fasterf. Best way to defeat resistance is to increase size of axon and use myelinG. Concentration differences across cell membrane1. Intracellular: more K+ ions and negatively charged particlesa. Concentration gradient for K+ ions is greater from inside cell to outside2. Extracellular: more Na+ ions and Cl- ionsa. Concentration gradient for Na+ ions is greater from outside the cell to inside3. Sodium/potassium exchange pump: uses ATP to move ions against their concentration gradients to maintain ion levelsH. Movements through the cell membrane1. Ion channelsa. Nongated: always openb. Voltage gated: open and close in response to voltage changes c. Ligand gated: open and close in response to different ligandsI. Resting membrane potential (RMP): at rest, electrically excitable cells are slightly more positive on the outside than inside1. Can range from -90 to -40 mV in different neurons (generally around -70 mV)2. Depolarization: makes inside of cell less negative from the RMP, caused by increase in extracellular K+ ions or influx of Na+ ions3. Hyperpolarization: makes inside of cell more negative from the RMP, caused by decrease in extracellular K+ ions, so more K+ ions tend to diffuse out of cell and make inside more negativeJ. Electrically excitable cells1. Graded potential: local potential2. Summation of graded potentials3. Action