BIO 1150 1st Edition Lecture 14Topic Discussed: Nervous SystemAction potential- transient change in membrane voltage (Vm)Voltage gated ion channels- electrical environment influences shape of channelResting voltage= -70• More potassium ions are in inside the cell• More sodium ions are outside of the cell• Sodium ion entry contributes to positive voltageIf Vm reaches threshold, voltage is gatedVmis positive enough, sodium ion channels closeBlocking voltage gated sodium channels- prevents depolarization and then neurons don’t workOuabain- blocks sodium potassium pumpsRefractory period- after a region of neuron firing and AP, this is the recovery periodNeural Conduction• An action potential occurs in a localized spot on axonThese 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.• Once APs are initiated at a point in the axon they stimulate additional APs sequentially along axon (conduction; propagation)1. Sodium ion entry stimulates action potential2. Sodium ions spread, depolarizing next region on the axon3. Depolarization activates next action potentialSalutatory conduction- many neuronal axons are surrounded by myelin sheaths• Insulate axon- no leaked energy (schwann cell)Nerve conduction test- fast nerve signals means that the myelin is goodBigger axons- increases conduction velocitySynapse- how cell to cell communication works• End of one cell attaches to another• Axonterminal (presynaptic) leads to the soma/ dendrite (postsynaptic)• Neurotransmitter binds to receptor which causes change in receiving cells• Receptors and ion channels (ligand gated)- neurotransmitters activatedNeurotransmitters- released from neuron and diffuse across the synapse to the target cell• Must bind to a certain receptor on postsynaptic membrane to influence opening/closing ofion channels• Removal of neurotransmitters shuts off neural signalsNeurotransmitter inactivation- involves metabolism and reuptake (SSRIs= Selective Serotonin Reuptake Inhibitors)Serotonin defficiency- causes mood disordersNeural integration- cell body• 1 neuron= up to 1000s of synapsesAxon hillock (decider) depolarized enough will activate action potential• Excitation- away from threshold• Inhibition- towards thresholdMotor control1. Skeletal muscles controlled by motor neurons (motor units) • Neurons (motor) activates targets• Peripheral nerves- motor and sensory neurons2. Motor neurons have cell bodies in ventral spinal cord• In the spine, the dorsal side= sensory and the ventral side = motor• Cell bodies = integration points• Axons= conductors3. Simple motor responses can be the result of simple reflex pathways• Reflex and reflex arc• Sensor (senses muscles length) coordinates posturesimple pathway- one sensory neuron, one motor neuron• Synapse in CNS• No brain involvement (reflex)4. Spinal nerves receive input from “descending tracts” of neurons that originate in motor cortex and cross over in medulla• Left side motor control coordinates to the right side of the brain• Each motor neuron originates in cortex and ends in the ventral spinal cord5. Motor cortex is in the frontal lobe• Neurons in motor cortex organized as a map of a body6. Motor cortex receives input from cerebellum• Early brain activity before movement is in the basal ganglia and substantia
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