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Bisc 276 Exam 3- Dynamic Study Modules and Learning Catalytics
Terms in this set (120)
The resting membrane potential depends directly or indirectly on what?
The concentration gradients of ions across the cell membrane, the ion permeability of the cell membrane, and the Na+/K+ ATPase- a neuron at rest, but poised to carry an electrical impulse, is said to exhibit a resting membrane potential. This condition is established by a concentration gradient of higher sodium ions on the outside of the membrane versus a higher concentration of potassium and anionic protein molecules on the inside. This concentration gradient is established through the activity of the Na+/K+ active transport pump and is maintained due to the lack of permeability to the ions via diffusion. The ions do not diffuse unless gated protein channels in the membrane open to allow them to do so.
Refractory periods contribute to what properties of action potentials?
Directionality, all or none, and coding of stimulus strength by frequency (the threshold of the membrane is not consequential to the timing of either of the refractory periods)- absolute and relative refractory periods
What is NOT a function of glial cells?
Movement- glial cells are engaged in providing functions that aid and support the functions of neurons in both the peripheral and central nervous systems; providing directions for growth and repair is accomplished by astrocytes, and phagocytosis is provided by microglial cells.
Outside the central nervous system, clusters of neuron cell bodies are called BLANK, and axons travel together in bundles called BLANK.
Cell bodies are called ganglia, and axon bundles are called nerves- when sharing the same arrangement within the CNS, cell bodies are called nuclei
What is true of myelinated axons?
Action potentials propagate by electronic conduction, currents must reach the next node before the membrane potential falls below threshold, and some current leaks across the membrane between nodes- once initiated, action potentials travel along the length of the axon, with no decrease in voltage, regardless of the distance traveled, and in one direction only, which is largely due to the manner in which the AP is first generated and then propagated at each node of Ranvier.
Neurons that innervate smooth muscle (such as the lining of blood vessels or the GI tract) belong to what part of the nervous system?
The peripheral and autonomic- the PNS is broadly defined as the neurons and receptors that supervise conditions throughout the body and convey information to and from the brain and spinal cord (CNS), and the neurons of the autonomic system are those components of the PNS that function in communication and control of involuntary responses in smooth muscle.
The resting membrane potential of a cell is produced by ion movements through what?
Potassium leak channels and sodium leak channels
In neurons that generate many action potentials, why don't the ion gradients across the neuron's cell membrane dissipate?
The Na+/K+ ATPase helps reestablish the gradients by actively transporting these ions back across the neuronal membrane and even though the membrane potential can change dramatically, very few ions actually move across the neuronal membrane during each action potential.
The amplitude (highest voltage achieved- maximum amount of sodium ions have diffused into the cell) of the peak of the action potential depends on what?
The relative sizes of the electrochemical gradients for Na+ and K+ and the differences in Na+ and K+ permeability.
Graded potentials and action potentials are different in what way(s)?
Action potentials DO typify the all-or-none law of neurons, they DO NOT diminish with distance and are therefore non-decremental, but they DO NOT code for stimulus strength by amplitude. Stimulus strength is coded for by frequency coding.
In sodium channels at resting membrane potential, what happens?
The activation gate is closed and the inactivation gate is open- a stimulus creates just enough energy to cause a sodium activation gate to open slightly, while the inactivation gate remains open, allowing small number of Na+ ions to diffuse through the membrane to the inside of the cell >> this voltage increase rises to a level that causes the activation gate to open fully, producing an influx of Na+ ions and a corresponding peak action potential voltage, and the inactivation gate will then close to prevent movement of Na+ ions before the gates reset to their resting position in prep for another action potential.
In contrast to almost all other cell types in the body, neurons can do what?
Can change their membrane potential and the permeability of their plasma membranes (as a means of transmitting an electrical signal- accomplished through the use of both mechanical and voltage-gated protein channels in response to stimuli capable of generating and propagating increased electrical voltage)
The types of channels that can be found in excitable cells such as neurons include what?
Leak (ions leak through the membrane), voltage-gated (voltage achieved at threshold that opens sodium and potassium ion channel gates in order to conduct an action potential), and ligand-gated (chemicals are released that attach to receptors that act like switches).
Describe Schwann cells.
They are located in the peripheral nervous system and they are a type of glial cell- function is to create sections along the length of an axon, which are electrically insulated from one another by myelin (similar to oligodendrocytes in the CNS); Schwann cells are associated with only one axon, but oligodendrocytes can be associated with multiple axons.
Action potentials propagate down the axon how?
Like a row of falling dominoes, by current flow through the intra- and extracellular fluid around sequential areas of axonal membrane, and by current flow through electronic conduction- propagation meaning the electrical signal is stopped and started every segment as it progresses to the end of the neuron (like dominoes, it cannot "fall" again without being reset)
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