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175 Cards in this Set
- Front
- Back
the action potential is also known as what?
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the nerve impulse
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do action potentials diminish over distance?
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no, they are signals of fixed size and duration
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information in action potentials is encoded in the pattern of what?
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electrical impulses
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what are cells that are capable of generating and conducting action potentials called?
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they have an excitable membrane
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what types of cells are capable of having an excitable membrane?
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nerve and muscle cells
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the "action" in action potentials occurs where?
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at the cell membrane
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the difference in electrical charge across the membrane is called?
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the resting membrane potential
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what is another name for the resting membrane potential?
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the resting potential
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the action potential is simply a brief reversal of what condition?
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the resting potential
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what is the main ingredient of fluid inside the neuron, the intracellular fluid or cytosol?
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water
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what is the fluid that bathes the neuron?
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the extracellular fluid
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what is the most important property of the water molecule?
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the uneven distribution of electrical charge
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covalent bonds means?
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they share electrons
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the oxygen atom in water acquires what type of charge?
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a net negative charge (because it has extra electrons)
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the hydrogen atoms in water acquire what type of charge?
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a net positive charge
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H20 is what type of molecule?
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a polar molecule
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atoms or molecules that have a net electrical charge are called?
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ions
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the electrical attraction of oppositely charged atoms is called?
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ionic bond
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what are the purpose of spheres of hydration?
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they are clouds of water that surround each ion and they effectively insulate the ions from one another
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the electrical charge of an atom depends on the difference between what?
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the number of protons and electrons
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ions with a difference of 1 protons or electrons is?
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monovalent
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ions with a difference of 2 protons or electrons is?
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divalent
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ions with a net positive charge are called?
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cations
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ions with a negative charge are called?
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anions
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the ions of particular importance for cellular neurophysiology are?
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the monovalent cations Na+ (sodium) and K+ (potassium) and the divalent cation Ca2+ (calcium) and the monvalent anion Cl- (chloride)
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water loving molecules are?
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hydrophilic
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compounds whose atoms are bonded by nonpolar covalent bonds have?
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no basis for chemical interactions with water
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water fearing molecules are?
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hydrophobic
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lipid
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a class of water insoluble biological molecules
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the main chemical building blocks of cell membranes are?
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phospholipids
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how are phospholipids like other lipids?
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they contain long nonpolar chains of carbon atoms bonded to hydrogen atoms
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how are phospholipids different from other lipids?
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they have a polar phosphate group (a phosphorous atom bonded to three oxygen atoms) attached to one end of the molecule
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phospholipids have what types of ends?
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a polar "head" (containing phosphate) that is hydrophilic, and a nonpolar "tail" (containing hydrocarbon) that is hydrophobic
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how is a phospholipid bilayer composed?
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hydrophilic heads face the outer and inner watery environments and the hydrophobic tails face each other
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what does a phospholipid bilayer do?
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it effectively isolates the cytosol of the neuron from the extracellular fluid
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enzymes, cytoskeleton and receptors are all made up of?
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protein molecules
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proteins are?
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molecules assembled from various combinations of 20 different amino acids
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all amino acids have what?
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a central carbon atom (the alpha atom), which is covalently bonded to four molecular groups: a hydrogen atom, an amino group, a carboxyl group, and a variable group called the r group (r for residue)
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how are proteins synthesized?
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by the ribosomes of the neuronal cell body
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what is the process of synthesizing a protein?
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amino acids assemble into a chain connected by peptide bonds, which join the amino group of one amino acid to the carboxyl group of the next
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proteins made of a single chain of amino acids are also called?
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polypeptides
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what are the four levels of protein structure?
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primary structure
secondary structure tertiary structure quaternary structure |
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what are the structures like for a primary structure?
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like a chain, in which the amino acids are linked together by peptide bonds
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alpha helix
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a spiral-like configuration that a polypeptide chain can coil into as a protein molecule is being synthesized
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alpha helix is an example of what type of protein structure?
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a secondary structure
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the protein structure that is acquired by interaction with r groups is ?
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tertiary structure
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when different polypeptide chains can bond together to form a larger molecule, what type of protein structure does this create?
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quaternary structure
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each of the different polypeptides contributing to a protein with a quaternary structure is called?
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a subunit
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what did civilization believe before the time of Hippocrates?
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the heart was the seat of consciousness and thought
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who is the father of Western medicine?
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Hippocrates
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hippocrates believed what about the brain?
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the brain not only was involved in sensation but also was the seat of intelligence
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what did aristotle believe?
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the heart was the center of intellect and that the brain was the radiator for the cooling of blood that was overheated by the seething heart
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Galen was?
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an important figure in Roman medicine; a Greek physician;
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what did Galen believe?
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the cerebrum must be the recipinet of sensations and the cerebellum must command the muscles; sensations were registered and movements initiated by the movement of humors to or from the brain ventricles via the nerves
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the cerebrum does what?
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is a repository for memory
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what are ventricles?
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hollow spaces in the brain
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who was Descartes?
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a French mathematician and philosopher;
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what did Descartes believe?
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believed in the fluid-mechanical theory of brain function; believed that the mind is a spiritual entity that receive sensations and commands movements by communicating with the machinery of the brain via the pineal gland
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what was an important breakthrough in neuroanatomy?
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the observation that the same general pattern of bumps "gyri" and grooves "sulci" and "fissures" could be identified on the surface of the brain in every individual; those patterns enable the parceling of the cerebrum into lobes
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the nervous system consists of two divisions?
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the central nervous system and the peripheral nervous system
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what is the central nervous system?
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the brain and the spinal cord
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what is the peripheral nervous system?
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the nerves and the nerve cells that lie outside the brain and spinal cord
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what is a Sylvian fissure?
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divides the frontal lobe from the temporal lobe
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what is the central sulcus?
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divides the frontal lobe from the parietal lobe
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who learned that the nerves are 'wires' that conduct electrical signals to and from the brain?
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Luigi Galvani and Emil du Boi-Reymond
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Within each nerve of the body there are many...?
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thin filaments, or nerve fibers, each one of which could serve as an individual wire carrying information in a different direction
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What did Charles Bell and Francois Magendie do?
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showed that the two spinal roots, the dorsal root and the ventral root carry information in different directions; they experimented on animals; discovered that within each nerve there is a mixture of many wires, some of which bring information into the brain and spinal cord and others that send information out to the muscles
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Magendie later showed that?
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the dorsal roots carry sensory information to the spinal cord
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Bell proposed what about the cerebrum and cerebellum?
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that the origin of motor fibers is the cerebellum and the destination of the sensory fibers is the cerebrum
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what is the experimental ablation method?
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destroying parts of the brain to determine their function
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what is phrenology?
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developed by Franz Gall; different behavioral traits could be related to the size of different parts of the skull
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what is the inner space between the cristae called?
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matrix
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what are site of cellular respiration?
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mitochondria
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what happens when a mitochondrion inhales?
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it pulls inside pyruvic acid (derived from sugars and digested proteins and fats) and oxygen, both of which are floating in the cytosol
within the inner compartment of the mitochondrion, pyruvic acid enters into a complex series of biochemical reactions called the Krebs cycle |
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what does the Krebs cycle do?
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Krebs cycle creates biochemical products that fuel the electron-transport chain and eventually yielding ATP
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how many ATP molecules are released for every molecule of pyruvic acid taken in by a mitochondrion?
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17 ATP
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when a mitochondrion exhales...?
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17 ATP molecules are released
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what does the chemical energy in ATP fuel?
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most of the biochemical reaction of the neuron
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what does the neuronal membrane do?
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serves as a barrier to enclose the cytoplasm inside the neuron and to exclude certain substances that float in the fluid that bathes the neuron
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what do some of the membrane-associated proteins do?
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pump substances from the inside to the outside; others form pores that regulate which substances can gain access to the inside of the neuron
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what is an important characteristic of neurons?
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the protein composition of the membrane varies depending on whether it is in the soma, the dendrites, or in the axon
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what is the cytoskeleton?
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it gives the neuron its characteristic shape; acts as scaffolding to the neuronal membrane
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what are the "bones" of the cytoskeleton?
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the microtubules, microfilaments and neurofilaments
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Characteristics of microtubules?
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big and run longitudinally down neurites; it appears as a straight, thick-walled hollow pipe; the wall of the pipe is composed of smaller strands that are braided like rope around the hollow core
each of the smaller strands consists of the protein tubulin |
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what is a single tubulin molecule like?
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small and globular
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what is polymerization?
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the process of joining small proteins to form a long strand
the resulting strand is a polymer |
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what are MAPs and what do they do?
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Microtubule-associated proteins
they participate in the regulation of microtubule assembly and function they anchor the microtubules to one another and to other parts of the neuron |
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what is tau?
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pathological changes in an axonal MAP; has been implicated in the dementia that accompanies Alzheimer's disease
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what is the severity of the dementia in Alzheimer's disease well correlated with?
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the number and distribution of what are now commonly known as neurofibrillary tangles, the "tombstones" of dead or dying neurons
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what is the first step in the process that leads to neurofibrillary tangle formation and dementia?
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the abnormal secretion of amyloid by neurons
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what are microfilaments?
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braids of two thin strands, which are made of polymers of the protein actin
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what is actin?
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a protein; and one of the most abundant in cells of all types and is believed to play a role in changing cell shape
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what do microtubules and actin microfilaments do similarly?
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they are constantly undergoing assembly and disassembly, and this process is regulated by signals in the neuron
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information about microfilaments
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they are anchored to the membrane by attachments with a meshwork of fibrous proteins that line the inside of the membrane like a spiderweb
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Neurofilaments exist ...?
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in all cells of the body as intermediate filaments; only in neurons are they called neurofilaments
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neurofilament characteristics
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consists of multiple subunits (building blocks) that are organized like a chain of sausages
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what is the internal structure of each subunit consist of?
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three protein strands woven together
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what makes up the brain's neurotransmitter systems?
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collections of cells that use a common neurotransmitter
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what are the most numerous glia in the brain?
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astrocytes
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what cells fill the spaces between neurons?
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astrocytes
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what is the primary function of oligodendroglial and Schwann cells?
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provide layers of membrane that insulate axons
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what spirals around axons in the brain?
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myelin
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what is the entire covering of the axon called?
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myelin sheath
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the region that an axonal membrane is exposed whtn the sheath is interrupted periodically is called?
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a node of Ranvier
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oligodendroglia are only found where?
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in the central nervous system
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Schwann cells are only found where?
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in the peripheral nervous system
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one oligodendroglial cell can do what?
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will contribute myelin to several axons
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this type of cells myelinates only a single axon
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schwann cell
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what provides the lining of the fluid-filled ventricles within the brain, and direct cell migration during brain development?
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Ependymal cells
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what functions as phagocytes to remove debris left by dead or degenerating neurons and glia?
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microglia
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this type of protein could be suspended in a phospholipid bilayer, with its hydrophobic portion inside the membrane and its hydrophilic ends exposed to the watery environments
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channel proteins
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what is one important property of most ion channels?
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ion selectivity
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what is an important property of many ion channels?
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gating
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channels with the gating property can be opened or closed by?
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changes in the local microenvironment of the membrane
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what do ion channels consist of?
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they consist of membrane-spanning proteins that assemble to form a pore
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what do other membrane-spanning proteins form to create?
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ion pumps
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what are enzymes that use the energy released by the breakdown of ATP to transport certain ions across the membrane?
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ion pumps
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what plays a critical role in neuronal signaling by transporting Na+ and Ca2+ from the inside of the neuron to the outside?
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ion pumps
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movement made by ions from regions of high concentration to regions of low concentration
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diffusion
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what is the difference between high and low concentration called?
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a concentration gradient
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ions will flow in which direction in a concentration gradient?
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down
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besides diffusion down a concentration gradient, what is another way to induce a net movement of ions in a solution?
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use an electrical field
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the movement of electrical charge is?
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electrical current
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what is the symbol for electrical current?
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I
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what is electrical current measured in?
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units called amperes (amps)
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what two factors determine how much current will flow?
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electrical potential and electrical conductance
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what is another term for electrical conductance?
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voltage
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what is the force exerted on a charged particle and it reflects the difference in charge between the anode and the cathode
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electrical potential or voltage
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the symbol for voltage
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V
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what is the relative ability of an electrical charge to migrate from one point to another
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electrical conductance
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the symbol for electrical conductance
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g
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what is electrical conductance measured in?
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units called siemens (S)
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what does conductance depend on?
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depends on the number of particles available to carry electrical charge and the ease with which these particles can travel through space
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what is electrical resistance?
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the relative inability of an electrical charge to migrate
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what is electrical resistance measured in?
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ohms
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symbol for electrical resistance?
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R
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what is the inverse of conductance?
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resistance
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current is the product of the conductance and potential difference; if the conductance is zero, no current will flow even when the potential difference is very large and also, when the potential difference is zero, no current will flow even when the conductance is very large
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ohm's law
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formula for ohm's law
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I = gV
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what is required in order to drive an ion across the membrane electrically?
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(1) the membrane possesses channels permeable to that ion, and (2) there is an electrical potential difference across the membrane
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what is the membrane potential?
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the voltage across the neuronal membrane at any moment
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the symbol for membrane potential?
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Vm
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when Vm or membrane potential is not at rest is due to?
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an action potential
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how can membrane potential be measured?
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by inserting a microelectrode into the cytosol
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a thin glass tube with an extremely fine tip that will penetrate the membrane of a neuron with minimal damage; it is filled with an electrically conductive salt solution and connected to a device called a voltmeter
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microelectrode
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what does the voltmeter measure?
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the electrical potential difference between the tip of this microelectrode and a wire placed outside of the cell
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when is an equilibrium state reached?
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when the diffusional and electrical forces are equal and opposite, and the net movement of K+ across the membrane ceases
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what is the electrical potential difference that exactly balances an ionic concentration
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an ionic equilibrium potential
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what is the symbol for electrical potential difference?
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Eion
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large changes in membrane potential are caused by?
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miniscule changes in ionic concentrations
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where does the net difference in electrical charge occur?
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the inside and outside surfaces of the membrane
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what is capacitance?
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when a membrane is said to store electrical charge it has capacitance
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ions are driven across the membrane ..?
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at a rate proportional to the difference between the membrane potential and the equilibrium potential
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what is the difference between the real membrane potential and the equilibrium potential for a particular ion called?
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the ionic driving force
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if the concentration difference across the membrane is known for an ion, then?
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an equilibrium potential can be calculated for that ion
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an impermeable membrane separates two regions:
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one of high salt concentration (outside) and the other of low salt concentration (inside)
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the Nernst equation calculates?
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the exact value of an equilibrium potential in mV
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what does the Nernst equation consider?
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the charge of the ion
the temperature the ratio of the external and internal ion concentrations |
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what is the sodium-potassium pump?
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an enzyme that breaks down ATP in the presence of internal Na+
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the Na-K pump pushes ions how?
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across the membrane against their concentration gradients
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what is a membrane-associated protein that transports ions across the membrane against their concentration gradients at the expense of metabolic energy?
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sodium-potassium pump
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what type of pump is also an enzyme that actively transports Ca2+ out of the cytosol across the cell membrane?
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the calcium pump
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characteristic of neurons:
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neurons are not permeable to only a single type of ion
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a mathematical formula that takes into consideration the relative permeability of the membrane to different ions
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Goldman equation
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Jan
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determined the amino acid sequences of a family of potassium channels; the search was conducted using the fruit fly Drosophila melanogaster
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Shaker potassium channel
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enabled researchers to find the genes for other potassium channels based on sequence similarity
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when you increase extracellular potassium it?
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depolarizes neurons
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a blood-brain barrier is what?
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a specialization of the walls of brain capillaries that limit the movement of potassium (and other bloodborne substances) into the extracellular fluid of the brain
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the neuronal membrane at rest is highly permeable to what?
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K+, owing to the presence of membrane potassium channels
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when there is a movement of K+ ions across the membrane
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they move down their concentration gradient, leaving the inside of the neuron negatively charged
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the extensive network of astrocytic processes
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helps dissipate the K+ over a large area
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the electrical potential difference across the membrane can be thought of as
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a battery whose charge is maintained by the work of the ion pumps
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Weaver rat strain
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the mutation of an amino acid in these rats allows Na+ and K+ to pass through the channel (a region of the brain important for motor function)
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what fills most of the space beween neurons?
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astrocytes
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what is a blood-brain barrier?
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a specialization of the walls of brain capillaries that limits the movement of potassium (and other bloodborne substances) into the extracellular fluid of the brain
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