Neuron Anatomy and Function: Terms and Definitions, Quizzes of Psychology of Human Development

Download Neuron Anatomy and Function: Terms and Definitions and more Quizzes Psychology of Human Development in PDF only on Docsity! TERM 1 Neuron DEFINITION 1 A neuron ( , also known as a neurone or nerve cell) is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. TERM 2 Dendrites DEFINITION 2 Dendrites (from Greek dndron, -tree-) are the branched projections of a neuron that act to conduct the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project. RECEIVE synaptic contacts from other neurons TERM 3 Axon DEFINITION 3 long narrow process that projects from the cell body (soma) TERM 4 Axon Hillock DEFINITION 4 cone shaped region between the axon and soma TERM 5 Myelin DEFINITION 5 Myelin is a dielectric (electrically insulating) material that forms a layer, the myelin sheath, usually around only the axon of a neuron. causes faster transmission of impulses! TERM 6 Node of Ranvier DEFINITION 6 Nodes of Ranvier are the gaps (approximately 1 micrometer in length) formed between the myelin sheaths generated by different cells. action potentials jump from node to node TERM 7 Terminal buttons DEFINITION 7 endings of axon branches (opposite to the end of cell body) which release chemicals into synapses TERM 8 Synapse DEFINITION 8 In the nervous system, a synapse is a junction that permits a neuron to pass an electrical or chemical signal to another cell. gaps between adjacent neurons where chemical signals are transmitted TERM 9 Membrane Potential DEFINITION 9 Membrane potential (or transmembrane potential) is the difference in voltage (or electrical potential difference) between the interior and exterior of a cell . TERM 10 Resting Membrane Potential DEFINITION 10 -70 millivolts this means that the potential inside the resting neuron is about 70 mv less than outside the neuron ratio of negative to positive ions is greater inside neuron TERM 21 EPSP's DEFINITION 21 excitatory post synaptic potentials increase likelihood that the neuron will fire proportional to the the intensity of the signals that elicit them TERM 22 IPSP's DEFINITION 22 inhibitory post synaptic potential decrease the likelihood that a neuron will fire proportional to the the intensity of the signals that elicit them TERM 23 Threshold of Excitation DEFINITION 23 usually about -65 mV If the sum of the depolarizations and hyperpolarizations (due to excitatory and inhibitory signals received from thousands of synapses) reaching the adjacent section of the axon hillock (the generating point of action potentials) is sufficient to depolarize the membrane to this level, then an action potential is generated. TERM 24 Action Potential DEFINITION 24 a massive but momentary- 1 millisecond, reversal of the membrane potential from -70 mV to about 50 mV these are all or none responses see fig 4.3 TERM 25 Voltage activated ion channels DEFINITION 25 ion channels that open or close in response to changes in the level of the membrane potential TERM 26 Ion activity during action potential DEFINITION 26 Voltage activated sodium channels in the axon membrane open wide when the membrane potential of the axon is reduced to the threshold of excitation, Na+ ions rush in, which raises the membrane potential from -70 to about 50. This voltage change triggers the opening of voltage- activated potassium channels and K+ ions are driven out (first by their relatively high internal concentration, and then by the positive internal charge when the action potential is near its peak) TERM 27 Refractory period DEFINITION 27 The 1-2 mseconds after an action potential in which another action potential cannot fire. A relative refractory period means that it is possible for the neuron to fire again, but a high level of stimulation would be necessary. TERM 28 Node of Ranvier DEFINITION 28 Nodes of Ranvier are the gaps (approximately 1 micrometer in length) formed between the myelin sheaths generated by different cells. Action potentials hop between these and cause them to move faster TERM 29 Myelin sheath DEFINITION 29 Myelin is a dielectric (electrically insulating) material that forms a layer, the myelin sheath, usually around only the axon of a neuron. insulates axon so there is less Na+ exchange and potentials can move faster TERM 30 Synaptic Vesicles DEFINITION 30 filled with neurotransmitters and and stored in clusters next to the presynaptic membrane. TERM 31 Neurotransmitters DEFINITION 31 small and large large are all neuropeptides- short amino acid chains (proteins) small are usually synthesized in the cytoplasm of the terminal button and packaged in synaptic vesicles by the golgi apparatus neuropeptides are assembled on ribosomes and are then packaged in vesicles by the golgi and transported by microtubles to the terminal buttons. TERM 32 Exocytosis DEFINITION 32 the process of neurotransmitter release When stimulated by an action potential, voltage activated Ca+ channels open, and Ca+enters the button. The entry of Ca+ ions cause the synaptic vesicle to fuse with the presynaptic membrane and empty the contents into the synaptic cleft