* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download the neural impulse
Neurocomputational speech processing wikipedia , lookup
Neuroeconomics wikipedia , lookup
Central pattern generator wikipedia , lookup
Microneurography wikipedia , lookup
Apical dendrite wikipedia , lookup
Neuroethology wikipedia , lookup
Endocannabinoid system wikipedia , lookup
Caridoid escape reaction wikipedia , lookup
Clinical neurochemistry wikipedia , lookup
Neural modeling fields wikipedia , lookup
Multielectrode array wikipedia , lookup
Feature detection (nervous system) wikipedia , lookup
Neural oscillation wikipedia , lookup
Mirror neuron wikipedia , lookup
Optogenetics wikipedia , lookup
Neuroregeneration wikipedia , lookup
Neuromuscular junction wikipedia , lookup
Electrophysiology wikipedia , lookup
Membrane potential wikipedia , lookup
Artificial neural network wikipedia , lookup
Metastability in the brain wikipedia , lookup
Convolutional neural network wikipedia , lookup
Resting potential wikipedia , lookup
Neuroanatomy wikipedia , lookup
Holonomic brain theory wikipedia , lookup
Neural coding wikipedia , lookup
Channelrhodopsin wikipedia , lookup
Recurrent neural network wikipedia , lookup
Action potential wikipedia , lookup
Types of artificial neural networks wikipedia , lookup
Node of Ranvier wikipedia , lookup
Axon guidance wikipedia , lookup
Chemical synapse wikipedia , lookup
Neural engineering wikipedia , lookup
Neurotransmitter wikipedia , lookup
Synaptogenesis wikipedia , lookup
Nonsynaptic plasticity wikipedia , lookup
Single-unit recording wikipedia , lookup
Neuropsychopharmacology wikipedia , lookup
End-plate potential wikipedia , lookup
Development of the nervous system wikipedia , lookup
Synaptic gating wikipedia , lookup
Molecular neuroscience wikipedia , lookup
Biological neuron model wikipedia , lookup
Stimulus (physiology) wikipedia , lookup
Neural Impulse SP4.20 Learning Centre THE NEURAL IMPULSE A neuron, or nerve cell, is the most basic component of the nervous system (Figure 1). To understand how neurons send messages, it is important to become familiar with their specialized structures. The soma (or cell body) is the neuron’s control centre. It contains the nucleus and other organelles which are necessary for the neuron’s survival. Dendrites are branched structures specialized to receive information from other neurons or cells. Therefore, the dendrites are the neuron's information receivers. Axons are long, tail-like fibers that extend from the soma. Their function is to send information to other neurons. Axons can be thought of as the neuron's information senders. The structure at the end of the axon is called the axon terminal. This is where neurotransmitters are released. A neuron may have many dendrites, but it has only one axon. Figure 1 D:\HANDOUTS\on h drive under Current Handouts\SPECIAL PURPOSE\SP4 Psychology\SP4.20 The Neural Impulse.doc I. Jakovljevic/2005 1 Neural Impulse SP4.20 Neurons' specialized structures allow them to transmit messages throughout the nervous system. The sending of a message from one neuron to the next is called the neural impulse. Figure 2 is a series of simplified diagrams meant to familiarize you with the steps involved in the neural impulse. Refer to diagrams 2 and 3 as you read through the description of each step. The transmission of a neural impulse occurs on the neuron's axon. 1. At rest, there is a different concentration of ions, or charged atoms, between the outside and the inside of the axon. Namely, there is a larger concentration of positive ions outside of the axon than there is inside of it. As is well known, opposite charges are strongly attracted to each other. That is, the positive charges on the outside of the axon are strongly drawn to the axon's more negative interior. Keeping these charges apart is the neuron's membrane. The membrane has small channels through which these ions can pass, but at rest, these channels are closed. This is called the resting potential (Figure 2a). 2. Eventually, a stimulus will excite a neuron's information receiver- the dendrite. This stimulus may come from an organism's external environment (such as touching a hot flame) or may originate from within the organism (for example, the release of hormones). D:\HANDOUTS\on h drive under Current Handouts\SPECIAL PURPOSE\SP4 Psychology\SP4.20 The Neural Impulse.doc I. Jakovljevic/2005 2 Neural Impulse SP4.20 Once the stimulus reaches a certain strength or the threshold, the small channels on the axon's membrane open. The opening of the channels on the axon's membrane allows the positive ions outside of the axon to rush in. The influx of positive ions changes the charge inside the axon, making it more positive. This process is called depolarization (Figure 2b). 3. As ions rush in through one gate, their positive charge causes the next, nearby gate to open, letting in more positive ions. The gates on the axon continue to open, and in this way, transmit the message down its entire length. The message traveling down the axon is the action potential (Figure 2c). D:\HANDOUTS\on h drive under Current Handouts\SPECIAL PURPOSE\SP4 Psychology\SP4.20 The Neural Impulse.doc I. Jakovljevic/2005 3 Neural Impulse SP4.20 4. After transmitting a message, the axon returns to its resting state by pumping out positive ions through the channels on its membrane. This process is called the refractory period. Once the refractory period is over, the neuron is ready to transmit a message again. How does the axon of one neuron transmit messages to other, nearby neurons? In the nervous system, the axon terminals of one neuron are in very close contact with the dendrites of neighboring neurons. The signal is transmitted from one neuron to the next through the release of neurotransmitters, or chemical messengers. More specifically, when the action potential reaches the axon terminal of the sending neuron, it causes neurotransmitters to be released. The neurotransmitters then attach to receptors located on the receiving dendrite. This starts another action potential, and the entire process is repeated (Figure 3). After stimulating the receiving dendrite, neurotransmitters are taken back into the sending neuron. This recycling process is called reuptake. References: Kalat, J. W. (2004). Biological Psychology (8th ed.). Belmont: Wadsworth. 29-48 Myers, D. G. (2004). Psychology (7th ed.). New York: Worth. 57-68 D:\HANDOUTS\on h drive under Current Handouts\SPECIAL PURPOSE\SP4 Psychology\SP4.20 The Neural Impulse.doc I. Jakovljevic/2005 4