Lecture 3 Flashcards
What is a neuron?
A cell found in the nervous system that is specialized for the reception, conduction, and transmission of electrochemical signals
What is Dendrite?
A short process (projection) emanating from a neuron cell body, that receives synaptic contacts from other neurons
What is an Axon?
a long, narrow process (projection) emanating from a neuron cell body, the end of which releases chemicals into a synapsef
What is a synapse?
a gap between adjacent neurons across which chemical signals are transmitted
What is a glial cell
A cell found in the nervous system that helps support, protect, and nourish neurons
-type of cell that is most numerous in the nervous system
What is myelin?
-a fatty insulating substance that wraps around axons
-increases the speed and efficiency of axonal conduction
What two types of glia is myelin produced by?
-oligodendrocytes in the central nervous system
-schwann cells in the peripheral nervous system
What is resting potential?
-a steady membrane potential of about -70 mV
-the membrane potential of a neuron at rest
When does resting potential occur?
When the neuron is in a state where there are more sodium (Na+) ions outside the cell than inside, and more potassium (K+) ions inside than outside
What is Depolarization?
-would be a shift in the membrane potential from -70 mV to -67 mV
-a decrease in the negativity of a neuron at resting membrane potential
-is a type of postsynaptic potential that is also known as an excitatory postsynaptic potential because it increases the likelihood that the neuron will fire
What is hyperpolarization?
-would be a shift in the membrane potential from -70 mV to -72 mV
-is an increase in the negativity of a neuron at resting membrane potential
-type of postsynaptic potential that is also known as an inhibitory postsynaptic potential because it decreases the likelihood that the neuron will fire
What is the threshold of excitation?
-the cutoff amount of stimulation required in order to make a neuron fire
-the level of depolarization necessary to generate as action potential, usually about -65 mV
What is action potential?
-is the firing of a neuron
-a massive but momentary reversal of the membrane potential from about -70 mV about +50 mV
-an all or none response; that is, it either occurs to its full extent or does not occur at all
-actively conducted along an axon in a non decremental fashion; it does not grow weaker as it travels along the axonal membrane due to the opening of adjacent voltage-activated sodium channels
How is an action potential unlike a postsynaptic potential?
It is not graded response; its magnitude is not related in any way to the intensity of the stimulus that elicited it
When does action potential occur?
When there is a large influx of sodium (Na+) ions into the neuron due to the opening of voltage-activated sodium channels
What is spatial summation?
-is the integration of signals that occur at different sites on the neuron’s membrane
-the adding together on the axon of all excitatory and inhibitory potentials produced at different sites on the neuron’s membrane, in order decide whether to fire or not to fire on the basis of their sum
What is temporal summation?
-the integration of signals that occur at different times at the same synapse
-allows a brief sub-threshold excitatory stimulus to fire a neuron of it is administered twice in rapid succession
When does temporal summation occur?
When a particular synapse is activated and then activated again before the original postsynaptic potential has completely dissipated, thus causing the effect of the second stimulus to be superimposed on the lingering postsynaptic potential produced by the first
What is the absolute refractory period?
-is the time immediately after an action potential when the neuron is unable to fire again
-the brief period after an action potential during which it is impossible to elicit another action potential in the same neuron
-the hyper polarized state seen after an action potential during which potassium (K+) ions are driven out of the cell and the voltage-activated sodium channels are actively closed
What is the relative refractory period?
-the time immediately after an action potential when it is difficult, but nevertheless possible, for the neuron to fire
-the period of time after the absolute refractory period during which a higher-than-normal amount of stimulation is necessary to make a neuron fire
-the hyper polarized state seen after an action potential during which voltage-activated sodium channels can possibly be opened again
