November 7, 2016 Journal: What is the difference between dendrites and the axon terminal?
How Neurons and Synapses Work
Excitable Cells Neurons, glands, and muscle cells Can carry an electrical charge when stimulated
Local Potential A stimulus causes a response in a cell called a local potential aka graded potential If its big enough it causes action potential
Occurs in response to an internal or external change Action Potential Occurs in response to an internal or external change Series of permeability changes within the neuron that carry the electrical impulse down the axon Impulse conduction
How Action Potential Works When a cell is not excited it is said to be at rest A resting cell is considered to be polarized Meaning that there is a difference in charge across the cell membrane with more negative charges inside the cell
How Action Potential Works When a neuron becomes stimulated, sodium ion channels open and let Na+ ions to travel into the neuron, making the cell more positive This is called depolarization
How Action Potential Works Then K+ leaves the cell through potassium ion channels These positive charges leaving the cell begin to return the cell back to a resting state. This is called repolarization.
How Action Potential Works Hyperpolarization - cell becomes more negative then when at rest Sodium-potassium pump works to restore equilibrium Refractory Period – Cell is unable to accept another stimulus until it returns to rest
How Action Potential Moves Down the Axon As the Na+ comes into one section of the axon, it triggers the sodium ion channels in the neighboring section to open Continues in a domino effect
Myelin Sheath Speeds up Impulse Conduction If a myelin sheath is present around the axon the impulse conduction will move faster
Axon Diameter Speeds up Impulse Conduction The wider the axon diameter the faster the ions will flow because there is more room for the ions to flow Action Potential Video: https://www.youtube.com/watch?v=OZG8M_ldA1M
November 7, 2016 Journal: Explain how an impulse is conducted down the axon of one neuron.
Chemical Synapses
Chemical Synapses Step 1: Sodium arrives at the axon terminal
Chemical Synapses Step 2: The terminal depolarizes and calcium enters through calcium ion channels
Chemical Synapses Step 3: Neurotransmitters are released from vesicles via exocytosis and are released into the synapse
Chemical Synapses Step 4: Neurotransmitters bind to the cell receiving signal and causes gates to open or close, either exciting or calming down the receiving cell
Chemical Synapses Step 5: Neurotransmitter is taken away from the synapse by an inactivator, usually an enzyme, to stop the neurotransmitter from continuously binding to the receiving cell
Important Neurotransmitters Acetylcholine: Controls skeletal muscles Norepinephrine: Control visceral and cardiac muscle Dopamine: Controls motivation and mood Epinephrine: Adrenaline; Increased fight or flight response Serotonin: Regulates mood and anxiety Endorphins: Increase pleasure and decrease pain
Synapse Video https://www.youtube.com/watch?v=p5zFgT4aofA