* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Nerves Powerpoint
Premovement neuronal activity wikipedia , lookup
Clinical neurochemistry wikipedia , lookup
Signal transduction wikipedia , lookup
Development of the nervous system wikipedia , lookup
Multielectrode array wikipedia , lookup
Optogenetics wikipedia , lookup
Neuromuscular junction wikipedia , lookup
Neurotransmitter wikipedia , lookup
Synaptogenesis wikipedia , lookup
Feature detection (nervous system) wikipedia , lookup
Nonsynaptic plasticity wikipedia , lookup
Neuroregeneration wikipedia , lookup
Circumventricular organs wikipedia , lookup
Patch clamp wikipedia , lookup
Synaptic gating wikipedia , lookup
Chemical synapse wikipedia , lookup
Pre-Bötzinger complex wikipedia , lookup
Nervous system network models wikipedia , lookup
Node of Ranvier wikipedia , lookup
Single-unit recording wikipedia , lookup
Biological neuron model wikipedia , lookup
Action potential wikipedia , lookup
Channelrhodopsin wikipedia , lookup
Neuroanatomy wikipedia , lookup
Neuropsychopharmacology wikipedia , lookup
Membrane potential wikipedia , lookup
End-plate potential wikipedia , lookup
Resting potential wikipedia , lookup
Electrophysiology wikipedia , lookup
Nerves By the end of this class you should understand: • The divisions of the nervous system and how they interconnect • The general role of glial cells and the specific function of selected glial cells • The structure and function of a neuron • The mechanism of an action potential and neuron signaling • The function of myelin in the nervous system Nervous System • The nervous system is one of the two control systems of the body – The other being the endocrine system – These two systems have a lot of interaction! • Made of neurons and neuroglia – Nervous tissue! Nervous System Organization Neuroglia • Also known as glial cells • Serve many functions related to protecting the neurons – Physical protection – Myelination (more on that later) – Chemical protection – Antimicrobial protection Neurons • There are three classifications of neurons – Sensory Neurons – Interneurons – Motor Neurons • Interneurons form the central nervous system (CNS) • Sensory and motor neurons form the peripheral nervous system (PNS) Neuron Structure • Neurons have three general structures: – Soma (cell body) – Axon (signal transmission) – Dendrite (signal reception) • Some neurons look rather different but all have these three parts in some way Electrical Activity • Recall that muscle and nervous tissue are electrically active • They maintain a potential across their cell membrane (outside has different electrical charge than inside) – This is also called a voltage Membrane Potential • There are many negatively charged particles both inside and outside the cell – Outside: chloride, inside: proteins • Whichever side of the membrane has more positively charged particles will be positive – The other side will be negative even though it clearly has many positively charged particles as well Positive Ions • Sodium and potassium are two positively charged particles found throughout the body • Neurons have sodiumpotassium pumps that pump three sodiums out of the cell for every two potassiums they pump into the cell – Creates a net positive charge outside the cell Sodium/Potassium Balance • Our diet must include both sodium and potassium on a regular basis – This is why sodium tastes good – The kidneys can help adjust this balance • Cramping and nervous problems can result from chronic or acute imbalances of ions – Sweating profusely can lose ions, which is why it is recommended to rehydrate with salt pills or gatorade Resting Membrane Potential • When a neuron is at rest, it is constantly pumping sodium out and potassium in to create a net positive charge on the outside of the cell – Typically the inside is -70mV compared to the outside • This requires a lot of daily ATP – Neurons can only use glucose, so blood sugar must be maintained at a constant level Graded potentials • Neuron potentials can be altered by many different structures – Sensory neurons can have their potentials altered by the stimulus they are supposed to detect (pressure, heat, stretch, light, etc) • These stimuli may cause the membrane potential to be reduced to -55 mV Threshold Voltage • -55mV is usually the threshold voltage, at which point the behavior of certain membrane proteins changes • These membrane channels are voltage-gated which means they open or close depending on the cell voltage • When the voltage hits 55mV, the voltage-gated sodium channels open THINK FAST! • When the voltage-gated sodium channels open, what happens to the: – Sodium? – Potassium? – Membrane Voltage? • Bonus thought: what would happen if these voltage-gated sodium channels were blocked? Voltage-Gated Ion Channels • The sodium will rush into the cell – Potassium ions cannot fit through the sodium channel and so remain concentrated inside the cell • Net effect: the voltage is now positive inside the cell! Voltage-gated Potassium Channels • The voltage change also opens voltage-gated potassium channels – These open more slowly than the sodium channels • When they open, potassium rushes out of the cell – Sodium channels inactivate quickly, whereas potassium channels inactivate slowly Voltage Changes • The potassium rushing out of the cell counterbalances the sodium rushing in – Cell voltage drops back to 70mV or more and the voltage-gated channels close • This brief flicker back and forth of voltage is called an action potential – All-or-none due to the voltage-gated ion channels Action Potential • The action potential can happen again only once the sodium and potassium have been replaced back to the outside and inside of the cell – Sodium-potassium pump required for this – The delay before firing again is called the refractory period Action Potential • So what is the purpose of the action potential?? – Must send a signal somehow! • Each voltage flip (action potential) on the membrane triggers the neighboring membrane proteins to flip their voltage – Sends a rapid wave down the cell membrane Speed of Conduction • Action Potentials may be sped up if there is myelin on the axon – In peripheral nervous system, Schwann cells provide the myelin and can also regrow the axon if it is damaged • Myelin conducts the voltage from one ion-channel node to the next much more quickly than if they were continuous Neurotransmitter • Recall from muscles that a neuron will release a neurotransmitter called acetylcholine onto a muscle • All neurons release a neurotransmitter at the end of the axon! – Acetylcholine is most common and usually stimulating – Dopamine and serotonin are commonly used in the brain and may be stimulating or inhibiting – There are many others! That’s our show! • See you Wednesday for more of the nervous system including the brain!