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Definition
| Nonexcitable cells that provide structural support or that serve important physiological and immunological functions in the nervous system. Also called glial cells. |
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| An atom or small molecule with a positive or negative electrical charge |
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| The brain and spinal cord |
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| Peripheral Nervous System |
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| That portion of the nervous system that lies outside the brain and spinal cord; includes nerves and ganglia |
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| Refers to a cell that responds to stimuli by generating an electrical signal at the cell membrane. Neurons and muscle cells are excitable. |
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| A cell that recieves signals from a neuron or a hormone |
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| A neuron with a central cell body that gives rise to multiple dendrites and a single axon. The most common type of neuron in humans. |
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| All Neurons have these three characteristic structural features: |
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Definition
| Cell body, receptive portion, and a transmitting portion. |
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| The portion of the neuron containing the nucleus and organelles; also called the soma[image] |
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| A cytoplasmic process that extends from a neuron's cell body, Neurons typcially have many dendrites, which are usually shorter and thicker than axons and highly branched. Dendrites recieve signals from other neurons.[image] |
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Definition
| A long, thin cytoplasmic process that extends from a neuron's cell body. The axon may be insulated with myelin. Each neuron has a single axon, which transmits action potentials.[image] |
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Definition
| A long-distance regenerative electrical signal transmitted along an axon. The action potential is an all-or-none event. Also called a nerve impulse, spike, or discharge. |
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Definition
| A junction between a neuron and its target cell (another neuron, muscle, or gland). Signals between neurons and other cells are communicated across synapsese. |
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Definition
| The first portion, or initial segment, of the axon |
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| The bulbous ending of a branch of an axon. Also called synaptic ending or synaptic bouton. |
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Definition
| Movement toward axonal terminal |
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Definition
| Movement away from axonal terminal |
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Definition
| The insulation surrounding axons. The myelin sheath is formed by support cells that wrap repeatedly around an axon, forming a thick layer of cell membrane. |
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Definition
| One type of support cell in the nervous system. Found in the peripheral nervous system, Schwann cells form myelin sheaths around axons. |
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Definition
| The insulation of an axon with myelin |
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Definition
| Tiny areas of bare axon between neighboring segments of myelin sheath. In a myelinated axon, charge flows across the membrane only at the nodes of Ranvier so the action potential appears to jump along the axon. |
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Definition
| Proteins that are embedded in the lipid bilayer of the cell membrane |
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Definition
| Integral proteins containing watery pores through which ions pass to cross the cell membrane |
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Definition
| Selective, Passive or active, Regionally located, and Functionally unique |
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Definition
| Ion channels that can be opened or closed by gates |
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Definition
| Ion channels that are always open. Also called leakage channels. |
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Definition
| Ion channels that are opened or closed by changes in membrane voltage |
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Term
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Definition
| The electrical potential, or voltage, across a cell membrane that results from the separation of charged particles across the membrane. |
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| Passive Channels are located: |
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Definition
| In the cell membrane on the dendrites, the cell body, and the axon |
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Term
| Chemically gated channels for the most part are located: |
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Definition
| In the dendrites and the cell body of the neuron |
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Term
| Voltage gated channels for the most part are located: |
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Definition
| On the axon hillock, all along unmyelinated axons, and at the nodes of Ranvier in myelinated axons. |
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Term
| Passive channels are responsibel for: |
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Definition
| The resting membrane potential |
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Term
| Chemically gated channels are responsibel for: |
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Definition
| Synaptic potentials, the incoming signals to the neuron. |
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| Voltage-gated channels are responsible for: |
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Definition
| Generation and propagation of the action potential, the outgoing signal from the neuron. |
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Term
| Resting Membrane Potential |
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Definition
| The membrane potential when a cell is at rest. |
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Definition
| A short-distance electrical signal that can vary in amplitude. Synaptic potentials are the imcoming signals to neurons. |
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Definition
| The movement of molecules from one location to another because of random thermal motion. Net movement is from a region of higher concentration to a region of lower concentration. |
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| A negatively charged ion. |
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| The characteristic of a cell membrane that permits some particles to cross it, but prevents other particles from crossing. |
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Definition
| The characteristic of a cell membrane that permits particles such as ions to pass from one side of the membrane to the other |
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Definition
| An electrical force across a cell membrane that results from the separation of charged particles across that membrane. |
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Definition
| The combined electrical and chemical forces on an ion. This force determines the net movement of charged particles. |
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Definition
| A state of chemical stability in which no net change occurs. For an ion in equilibrium across a cell membrane, the amount moving out is equal to the amount moving in. |
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Definition
| For a given ion, the membrane potential at which the electrical and chemical forces that drive that ion across the cell membrane are equal and opposite. |
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Definition
| A critical level of membrane potential at which the depolarization process becomes regenerative and the cell generates an action potential. |
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Definition
| Self-generating. Regenerative processes produce positive feedback loops. |
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Term
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Definition
| A regenerative process that amplifies an original signal. For example, at threshold, depolarization leads to greater influx of Na+, which leads to further depolarization. |
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Definition
| The process whereby the membrane potential of a cell moves back toward its resting value. |
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Definition
| The process by which the membrane potential of a cell changes to become more negative than its resting membrane potential. |
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Term
| Concentration (mM)/L of NA+ in intracellular and extracellular fluid. |
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Definition
| Inside cell=15. Outside cell=150. |
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Term
| Concentration (mM)/L of K+ in intracellular and extracellular fluid. |
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Definition
| Inside cell=150. Outside cell=5. |
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Term
| Concentration (mM)/L of Ci- in intracellular and extracellular fluid. |
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Definition
| Inside cell=10. Outside cell=125. |
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Term
| Absolute Refractory Period |
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Definition
The period of time following an action potential when an excitable cell cannot generate another action potential no matter how large a stimulus it receives.
Many Na+ channels are inactive and will not open no matter what voltage is applied to the membrane. Most K+ channels are open. |
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Term
| Relative Refractory Period |
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Definition
| The period of time following an action potential when an excitable cell can generate another action potential, but only if it is depolarized to a value more positive than normal threshold. This is true because some Na+ channels are still inactive and some K+ channels are still open. |
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Term
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Definition
| The speed with which an action potential is propagated along an axon. |
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Term
| Conduction velocity depends on: |
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Definition
| the diameter of the axon and how well the axon is insulated with myelin. |
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Term
| Ions flow along their chemical gradient when: |
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Definition
| They move from an area of high concentration to an area of low concentration |
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Term
| Ions flow along their electrical gradient when... |
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Definition
| they move toward an area of opposite charge |
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Definition
| The electrical and chemical gradients taken together. |
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