3 6 2020 Nervous and Endocrine System 1 How organisms respond to their environment a All organisms respond to their environment b Animals Nervous system rapid environmental response Endocrine system slow or chronic environmental response 2 Nervous system a Major nervous tissues i ii i ii Neurons Glial cells 1 Axons covered in myelin 1 Secrete myelin a Oligodendrocytes b Schwann cells iii A Schwann cells envelops an axon 1 The Schwann cell then rotates around the axon wrapping its plasma membrane loosely around it in successive layers 2 The Schwann cell cytoplasm is forced from between the membranes a The tight membrane wrappings surrounding the axon form the myelin sheath iv Myelin increases conduction speed v Long thin cells with fine branches at the ends capable of conducting electrical impulses b Functions i ii Sensory input 1 All five sense Integration 1 Going to your brain iii Motor output c 3 types of neurons 1 Working the muscles to output the sensory input Sensory neurons Interneurons i ii iii Motor neurons d Nerve fascicle of neurons Fascicle bundle of fibers e Parts of the nervous system i i ii Central nervous system brain and spinal cord Peripheral nervous system 1 Somatic nervous system a Motor neurons b Skeletal muscle 2 Autonomous nervous system a Sympathetic Fight or flight b Parasympathetic i Rest and digest c Autonomous regulation i i 3 Enteric nervous system a Digestive organs only b Gut 3 Defining terms a Voltage potential energy due separated electrical charges Smooth muscle cardiac muscle exocrine glands some endocrine glands b Current flow of electrical charge 4 Membrane potential differences in ionic concentrations in a resting cell a Electrical potential b Maintenance of membrane potential i Sodium potassium pump 3 Na out 1 2 2 K in a Negative charge relative to outside 3 Cytoplasmic Na binds to the sodium potassium pump 4 Na binding stimulates phosphorylation ATP 5 Phosphorylation causes the protein to change its conformation 6 Extracellular K binds to the protein triggering the release of expelling Na to the outside the phosphate group 7 Loss of phosphate restores the protein s original conformation 8 K is released and Na sites are receptive again a The cycle then repeats c Channels I Leak channels 1 Always open ii Gated channels 2 Open and close a Voltage b Chemicals d Resting membrane potential ii iii iv v vi 70 mV No ions move through voltage gated channels Depolarization caused by Na flowing into the cell Repolarization caused by K flowing out of the cell Hyperpolarization some K channels remain open and Na channels reset e Action potential i Brief change in membrane potential membrane is unstable and requires homeostasis mechanisms 1 Voltage gated sodium channel 2 Voltage gated potassium channels b Refractory period when Na channels inactivate Remember that depolarization occurs when Na channels are active i ii Myelin increases conduction speed
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