* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Ch 34 Action Potential and Neurons
Caridoid escape reaction wikipedia , lookup
Multielectrode array wikipedia , lookup
Patch clamp wikipedia , lookup
Clinical neurochemistry wikipedia , lookup
Microneurography wikipedia , lookup
Development of the nervous system wikipedia , lookup
Neuroregeneration wikipedia , lookup
Biology and consumer behaviour wikipedia , lookup
Signal transduction wikipedia , lookup
Channelrhodopsin wikipedia , lookup
Electrophysiology wikipedia , lookup
Nonsynaptic plasticity wikipedia , lookup
Synaptic gating wikipedia , lookup
Neuromuscular junction wikipedia , lookup
Biological neuron model wikipedia , lookup
Membrane potential wikipedia , lookup
Single-unit recording wikipedia , lookup
Action potential wikipedia , lookup
Node of Ranvier wikipedia , lookup
Nervous system network models wikipedia , lookup
Resting potential wikipedia , lookup
Chemical synapse wikipedia , lookup
Neuropsychopharmacology wikipedia , lookup
Neurotransmitter wikipedia , lookup
Synaptogenesis wikipedia , lookup
Molecular neuroscience wikipedia , lookup
CH 34 Neurons and Action Potential AP Biology Neurons dendrites cell body Structure fits function many entry points one path out transmits signal axon signal direction synapse AP Biology dendrite cell body axon Cells are surrounded by charged ions Anions [more within the cell] Cl-, charged amino acids (aa-) Cations [more in the extracellular fluid] K+, Na+ Na+ Na+ K+ AP Biology aa- K+ Na+ aaCl- Na+ ClK+ Na+ aa- Na+ K+ aa- K+ Na+ ClCl- Na+ aa- Na+ Na+ Na+ Claa- Cl- – K+ + channel leaks K+ voltage! membrane is polarized negative charge inside; positive outside stored energy (battery) nerve impulses are called action potentials + + + + + + + + + + + + + + + – – – – – – – – – – – – – – – – – – – – – – – – – – – – + + + + + + + + + + + + + + + AP Biology Action potential steps 1. Resting potential [-70mv] 2. Threshold potential [-55mv] 3. Depolarization [30mv] K+ AP Biology channels close slowly 40 mV 4 30 mV Membrane potential Na+ channels open; K+ channels closed 4. Na+ channels close; K+ channels open 5. Repolarization reset charge gradient 6. Hyperpolarization 20 mV 10 mV Depolarization Na+ flows in 0 mV –10 mV 3 –20 mV Repolarization K+ flows out 5 –30 mV –40 mV –50 mV Threshold –60 mV 2 –70 mV –80 mV 1 Resting potential Hyperpolarization (undershoot) 6 Resting Action Potential 1. Stimulus Na+ channels in membrane open Na+ diffuses in Axon reaches threshold potential 2. Charges reverse at that point = depolarized positive inside; negative outside – + + + + + + + + + + + + + + + – – – – – – – – – – – – – – Na+ AP Biology + – – – – – – – – – – – – – – – + + + + + + + + + + + + + + 3. Wave travels down neuron change in charge opens next Na+ gates Na+ ions continue to diffuse into cell – – – + + + + + + + + + + + + + + + – – – – – – – – – – – – Na+ + + + – – – – – – – – – – – – – – – + + + + + + + + + + + + AP Biology wave 4. 2nd wave travels down neuron K+ channels open K+ diffuses out charges reverse [negative inside; positive outside] Combined waves are called an action potential K+ + – – – – + + + + + + + + + + – + + + + – – – – – – – – – – Na+ – + + + + – – – – – – – – – – + – – – – + + + + + + + + + + AP Biology wave 5. Re-set Na+ needs to move back out K+ needs to move back in both move against concentration gradients need a pump!! K+ + Na Na+ + Na+ + K K Na+ + Na+ Na+ K+ K Na+ +Na + Na Na + + + + + + + + + + – – – – + – – +– – – – – – – – + + + + – Na+ Na K+ K+ + + K K++ Na + + + + Na K K Na K Na+ Na+ K+ – – – – – – – – – – + + + + – + + + + + + + + + + – – – – + AP Biology Na+ + Na+ / K+ pump active transport protein in membrane requires ATP 3 Na+ pumped out + 2 K pumped in AP Biology ATP Neuron is ready to fire again Na+ Na+ Na+ K+ aa- aaNa+ Na+ Na+ K+ Na+ Na+ K+ Na+ aa- K+ Na+ Na+ Na+ Na+ K+ aaNa+ Na+ Na+ K+ Na+ Na+ Na+ K+ aa- aa- K+ K+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ resting potential + + + + + + + + + + + + + + + – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – AP Biology + + + + + + + + + + + + + + + Myelin sheath Axon insulated signal direction speeds signal signal hops from node to node saltatory conduction myelin sheath AP Biology What happens at the end of the axon? Impulse has to jump the synapse! junction between neurons Synapse AP Biology Chemical synapse 1. 2. 3. 4. 5. 6. action potential reaches synapse Ca++ channels open neurotransmitters released into synapse neurotransmitters bind with protein receptor Ion channels open neurotransmitter broken down or reabsorbed AP Biology Examples of Neurotransmitters Acetylcholine signals skeletal muscle Epinephrine (adrenaline) fight-or-flight response Dopamine affects sleep, mood, learning AP Biology widespread in brain Too little Parkinson’s disease Too much schizophrenia The Trouble with Neurotransmitters Weak point substances that affect neurotransmitters affect nerve function Gases like carbon monoxide Mood altering drugs Stimulants caffeine amphetamines, caffeine, nicotine poisons AP Biology Acetylcholinesterase Enzyme which breaks down acetylcholine n inhibitors = neurotoxins snake venom, insecticides neurotoxin in green active site in red acetylcholinesterase AP Biology snake toxin blocking acetylcholinesterase active site Reflex Arc nerve pathway involving a sensory nerve and a motor nerve with a synapse between five (5) parts of a reflex: 1. 2. 3. 4. 5. AP Biology Receptor - sense organ in skin, muscle, organ Sensory neuron - carries impulse TO CNS Interneuron - carries impulse IN CNS Motor neuron - carries impulse AWAY from CNS Effector - structure that responds (ex: muscle, gland)