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Nervous SystemLecture 5 – Oct 4 – BIOL 105012.1-12.4, 13.1,13.2, Labs 16,17Internal communicationEndocrine and nervous system maintain internalcoordination1. Endocrine system• uses hormones secreted into blood• “long - distance” communication• slow2. Nervous system• uses electrical and chemical means• sends message from cell to cell• very quick (e.g. reflexes, perception-Nervous system is tightly integrated with all other body systemsNervous System Components1. Centralnervous system (CNS)• Brain and spinal cord• Enclosed by cranium and vertebral column2. Peripheral nervous system (PNS)• Consists of nerves and ganglia outside the brain and spinal cordNerves -bundle of nerve fibres (axons) wrapped in fibrousconnective tissueGanglion-knot like swelling in a nerve where neuron cellbodies are concentrated• Two divisions (sensoryandmotor), each with somatic and visceral subdivisionsNervous system organization: input/output1.Sense organs receive informationand transmit coded messages to the CNSInformation – changes in body or external environment2.CNS processes the information, determines appropriate response3.CNS issues commands to muscles and gland cellsto carry out the responseFunctional Classes of NeuronsAfferent Neuron -> Interneuron -> Efferent Neuron1.Afferent (sensory) NeuronsDetect stimuli and transmit the informationtoward the CNS
2.Interneurons (within CNS)-Connecting neurons - Receive signals from many neurons and carry out integrativefunctions (make decisions)-About 90% of our neurons are interneurons3.Efferent (motor) neuronsSends signals to muscles and/ or gland cellsPeripheral Nervous System1.Sensory (afferent) divisionSomatic• Signals from skin, muscles, bones, and jointsVisceral• Signals from the viscera (heart, lungs,stomach, and urinary bladder)2. Motor (efferent) divisionSomatic• Carries signals to skeletal muscles-Produces muscle contractionsVisceral(autonomic nervous system)-Signals to glands, cardiac, and smoothmuscleoInvoluntary responses arevisceral reflexesVisceral motor division (autonomic nervous system)Subdivisions:1.Sympathetic division• Tends to arouse body for action (“fight or flight”)-Accelerates heart beat and respiration-Inhibits digestive and urinary systems2. Parasympathetic division• Tends to have a calming effect (“rest and digest”)-Slows heart rate and breathing-Stimulates digestive and urinary systemsProperties of Neurons1. Excitability-will respond to stimuli (environmental changes)
2. Conductivity-produce electrical signals that are quickly conducted to other cells at distant locations3. Secretion-when signal reaches the end of a nerve fiber, a neurotransmitterwill be released thatcrosses the gap and influences the next cellNeuron StructureDendrites• branches off of the soma• receiving signals from other neurons• more dendrites a cell has, the more information it can receiveSoma(a.k.a. neurosoma or cell body)

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