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UI BIOL 1140 - Nervous System
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BIOL 1140 1st Edition Lecture 20Outline of Last LectureI. The Hypothalamus and Pituitary GlandII. The HypothalamusIII. The Posterior Pituitary GlandIV. The Anterior Pituitary Gland V. Temperature RegulationVI. Disorders of the Pituitary GlandOutline of Current LectureI. Nervous system Has Two Principal PartsII. Neurons Make Action PotentialsIII. Sodium-Potassium Pump Maintains resting potentialIV. Graded Potentials Alter the Resting PotentialV. An Action Potential Is a Sudden Reversal of Membrane VoltageVI. Action Potentials are All-or-None VII. Information is Transferred from a Neuron to its TargetVIII. Neurotransmitter is ReleasedIX. Neurotransmitters Exert Excitatory or Inhibitory EffectsX. Postsynaptic Neurons Integrate and Process InformationXI. Peripheral Nervous System Relays Info Between Tissues and CNSXII. Sensory Neurons Provide Info to the CNSXIII. The Somatic Division Controls Skeletal MusclesXIV. Neuroglia Cells Support and Protect NeuronsXV. Disorders Associated with Degeneration of Myelin SheathsXVI. The Autonomic Division Controls Automatic Body FunctionsXVII. The Sympathetic and Parasympathetic Divisions Oppose Each OtherCurrent Lecture II. Nervous system Has Two Principal Partsa. Central Nervous System (CNS)i. Components1. Brain and spinal cordii. Functions1. Receives, processes, and transfers infob. Peripheral nervous system (PNS)i. Components are nerves outside CNSii. Sensory division1. Carries info towards the CNSiii. Motor division1. Carries info away from CNSThese 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.III. Neurons Make Action Potentialsa. Neurons generate and transmit action potentialsb. An action potential is basically and electrical impulsec. Action potentials are the primary means of communication throughout the nervous systemIV. Sodium-Potassium Pump Maintains resting potentiala. Functions of NA+/K+ pumpi. Maintains cell volumeii. Maintains resting potential by transport of three Na+ out of the cell and two K+ into the cellb. Resting potentiali. Measurable difference in voltage across the cell membrane in a resting cellii. 70 mViii. Interior of cell negative relative to the exteriorV. Graded Potentials Alter the Resting Potentiala. Graded potentiali. Transient local changes in the resting potentialii. May depolarize or hyperpolarize the membraneb. Summationi. Graded potentials can add up in space or timeii. This additive effect may reach a trigger point, or threshold, which initiates an action potential VI. An Action Potential Is a Sudden Reversal of Membrane Voltagea. Depolarizationi. Voltage-sensitive Na+ channels open, Na+ moves into the axon b. Repolarizationi. Na+ channels close, K+ channels open, K+ moves out of the axonc. Reestablishment of the resting potentiali. K+ channels close, the normal activity of the sodium-potassium pump restores resting potentialVII. Action Potentials are All-or-None a. All or nonei. Once triggered, an action potential is always the same in speed and voltageb. Self-propagatingi. Continues to propagate itself in the next region of the axonii. Moves likes a wave down the axon, with constant speed and amplitudec. The number of the action potentials/unit time encodes the strength of stimulusi. Stronger stimuli generate more action potentials/unit timed. Speed of action potentiali. Always the same for a particular neuronii. Can be different in different neurons1. In larger diameter axons, action potentials travel at greater speedVIII. Information is Transferred from a Neuron to its Targeta. Targets: another neuron, muscle cell, or glandb. Synapse: special junction between axon terminus and target cellc. Synaptic transmissioni. Process of transmission of impulse from sending (presynaptic neuron) across synaptic cleft to receiving (postsynaptic) targetii. Involves release and diffusion of chemical neurotransmitterIX. Neurotransmitter is Releaseda. Events that occur during synaptic transmission:i. Action potential arrives at axon terminus, causing Ca2+ to diffuse into axon bulbii. Ca2+ causes release of neurotransmitter from vesiclesiii. Neurotransmitter diffuses across synaptic cleftiv. Neurotransmitter binds to receptors on target membrane and opens gated channelsv. Graded potential results from Na+ movement through opened channelsX. Neurotransmitters Exert Excitatory or Inhibitory Effectsa. Response of postsynaptic target cell depends on i. Type of neurotransmitterii. Type of receptorsiii. Type of gated ion channelsb. Excitatory neurotransmittersi. Depolarize the postsynaptic cell, approaching or exceeding thresholdc. Inhibitory neurotransmittersi. Hyperpolarize the postsynaptic cellXI. Postsynaptic Neurons Integrate and Process Informationa. Response in postsynaptic cells depends on i. How many neurons are forming synapses with itii. Whether the neurons forming synapses with it are excitatory or inhibitoryb. Convergence: occurs when one neuron receives input from many others c. Divergence: occurs when one neuron sends action potentials to multiple other neuronsXII. Peripheral Nervous System Relays Info Between Tissues and CNSa. Nervei. Contains axons of many neurons wrapped together in a protective sheathii. Carries info to and from the CNSb. Cranial nervesi. 12 pairsii. Connect directly to brainc. Spinal nervesi. 31 pairsii. Connect to spinal cordXIII. Sensory Neurons Provide Info to the CNSa. Provide info for both somatic and autonomic motor divisions of the PNSb. Incoming info arrives at the CNS as action potentials from sensory neurons located throughout the body XIV. The Somatic Division Controls Skeletal Musclesa. Functionsi. Voluntary 1. Conscious control of skeletal musclesii. Involuntary1. Spinal reflexes: involuntary responses mediated primarily by spinal cord and spinal nerves, with little brain involvementa. Flexor (withdrawal) reflexb. Crossed extensor reflexc. Stretch reflex: important in maintaining upright posture, movementXV. Neuroglia Cells Support and Protect Neuronsa. Neuroglia cells make up around 50% of nervous system cellsi. Function1. Support2. Protection3. Glial cells do NOT transmit action potentialsii. Two types1. Oligodendrocytes (in CNS, Schwann cells in PNS)2. Astrocytesb. Schwann Cells: form myelin sheaths in PNSi. Role of myelin sheath:1. Save the neuron energy2. Speed up the transmission of impulsesa. Salutatory conduction: leaping pattern of action potential conduction3.


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UI BIOL 1140 - Nervous System

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