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Definition
| a network of billions of nerve cells linked together in a highly organized manner to form the rapid control system of the body; controlled by the brain & spinal cord |
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| nerve cells that carry electrical signals rapidly & sometimes over long distances |
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| long, thin extensions that most neurons have that can extend up to a meter in length; give neurons their unique shapes |
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| chemical signals released by neurons in most pathways into the ECF to communicate with neighboring cells |
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Definition
| complex processes (consciousness, intelligence, & emotion) that cannot be predicted from what we know about the properties of individual nerve cells & their specific connections |
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| 2 things that make up the central nervous system (CNS) |
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Definition
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| 2 things that make up the peripheral nervous system (PNS) |
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Definition
1. sensory (afferent) neurons
2. efferent neurons |
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| 2 divisions of the efferent neurons |
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Definition
1. somatic motor division (controls skeletal muscles)
2. autonomic division (controls smooth & cardiac muscles, exocrine glands, some endocrine glands, & some types of adipose tissue) |
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| 2 branches of the autonomic neurons |
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Definition
1. sympathetic branch
2. parasympathetic branch
*can be distinguished by their anatomical organization & by the chemicals they use to communicate with their target cells* |
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Definition
| a network of neurons in the walls of the digestive tract |
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| 2 types of processes that extend from the nerve cell body |
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Definition
1. dendrites (receive incoming signals)
2. axons (carry outgoing information) |
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| neurons that lie entirely within the CNS |
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| branches into with axons may divide several times |
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| enlarged endings of efferent neurons |
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| enlarged regions along the axon of many autonomic neurons |
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| cordlike fibers into which the long axons of both afferent & efferent peripheral neurons are bundled with connective tissue that extend from the CNS to the targets of the component neurons |
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Definition
1. sensory nerves (nerves that carry only afferent signals)
2. motor nerves (carry only efferent signals)
3. mixed nerves (nerves that carry signals in both directions) |
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Term
| Does the cell body of a neuron resemble a typical cell with a nucleus & all organelles needed to direct cellular activity? |
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Definition
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| How can a dendrite's surface area by expanded? |
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Definition
| by the presence of dendritic spines that vary from thin spikes to mushroom-shaped knobs |
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Definition
| the specialized region of the cell body from which a single axon originates in most peripheral neurons |
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Definition
| the process by which proteins are moved down the axon |
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| How does slow axonal transport move material from the cell body to the axon terminal? |
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Definition
| axoplasmic or cytoplasmic flow |
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| How fast can fast axonal transport move organelles? |
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Definition
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Definition
| the region where an axon terminal meets its target cell |
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| 2 types of neurons involved in a synapse |
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Definition
1. presynaptic cell (the neuron that delivers a signal to the synapse)
2. postsynaptic cell (the cell that receives the signal) |
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Definition
| the narrow space between two cells |
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| The human CNS also contains _____, where the presynaptic & postsynaptic cells are connected by gap junction channels |
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Definition
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Definition
| special tips put out by the axons of embryonic nerve cells that extend through the extracellular compartment until they find their target cell |
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| The survival of neuronal pathways depends on _____ secreted by neurons & glial cells |
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Definition
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| Are there more glial cells or neurons in the nervous system? |
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Definition
| glial cells (outnumber neurons by 10-50 to 1) |
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| _____ in the PNS & _____ in the CNS support & insulate axons by forming myelin, a substance composed of multiple concentric layers of phospholipid membrane |
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Definition
| Schwann cells; oligodendrocytes |
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Definition
| tiny gaps left between the myelin-insulated areas of each axon because each Schwann cell wraps around a 1-1.5mm segment of an axon |
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Definition
| the second type of PNS glial cell; a nonmyelinating Schwann cell |
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Definition
| highly branched glial cells that by some estimates make up about half of all cells in the brain |
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| Are microglia cells actually neural tissue? |
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Definition
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Definition
| the final class of glial cells; specialized cells that create a selectively permeable epithelial layer (the ependyma) that separates the fluid compartments of the CNS |
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Definition
| immature cells that can differentiate into neurons & glial cells (ex. ependyma) |
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| 2 factors that influence the membrane potential |
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Definition
1. the uneven distribution of ions across the cell membrane
2. differing membrane permeability to those ions |
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| What does the Goldman-Hodgkin-Katz (GHK) equation calculate? |
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Definition
| the membrane potential that results from the contribution of al lions that can cross the membrane |
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Definition
| the ease with which ions flow through a channel |
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| 3 categories of gated channels |
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Definition
1. mechanically gated ion channels
2. chemically gated ion channels
3. voltage-gated ion channels |
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Definition
| the flow of electrical charge carried by an ion |
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| Current flow, whether across a membrane or inside a cell, obeys a rule known as _____ |
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Definition
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Definition
| a force that opposes flow |
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Definition
| variable-strength signals that travel over short distances & lose strength as they travel through the cell |
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Definition
| very brief, large depolarizations that travel for long distances through a neuron without losing strength |
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Definition
| a wave of depolarization that moves through the cell |
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| 2 reasons why graded potentials lose strength as they move through the cytoplasm |
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Definition
1. current leak
2. cytoplasmic resistance |
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Term
| Graded potentials that are strong enough eventually reach the region of the neuron known as the _____ |
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Definition
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Definition
| the very first part of the axon; along with the axon hillock, it is the trigger zone for efferent neurons & interneurons |
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Definition
| the high-speed movement of an action potential along the axon |
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| Why are action potentials sometimes called all-or-none phenomena? |
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Definition
| they either occur as a maximal depolarization or do not occur at all |
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Term
| 9 steps in the changing ion permeability along the axon during an action potential |
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Definition
1. resting membrane potential
2. depolarizing stimulus
3. membrane depolarizes to threshold
4. rapid Na+ entry depolarizes the cell
5. Na+ channels close & slower K+ channels open
6. K+ moves from cell to ECF
7. K+ channels remain open & additional K+ leaves cell, hyperpolarizing it
8. voltage-gated K+ channels close, less K+ leaks out of the cell
9. cell returns to resting ion permeability & resting membrane potential |
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Term
| The double gating of Na+ channels plays a major role in the phenomenon known as the _____ |
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Definition
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Term
| absolute refractory period |
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Definition
| the delay where a second action potential cannot be triggered once an action potential has begun; represents the time required for the Na+ channel gate to reset to their resting positions |
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Term
| Which comes first: absolute refractory period or relative refractory period? |
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Definition
| absolute refractory period |
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Term
| 5 steps for the conduction of an action potential |
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Definition
1. a graded potential above threshold reaches the trigger zone
2. voltage-gated Na+ channels open & Na+ enters the axon
3. positive charge flows into adjacent sections of the axon by local current flow
4. local current flow from the active region causes new sections of the membrane to depolarize
5. the refractory period prevents backward conduction |
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Term
| 2 physical parameters that influence the speed of action potential conduction |
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Definition
1. diameter of the axon
2. resistance of the axon membrane to ion leakage out of the cell |
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Term
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Definition
the apparent jump of the action potential from node to node
*"saltare" means "to leap" in Latin* |
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| What is the most common & best-known de-myelinating disease? |
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Definition
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Definition
| an increase in blood K+ concentration; shifts the resting membrane potential of a neuron closer to threshold & causes the cells to fire action potentials in response to smaller graded potentials |
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Term
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Definition
| when blood K+ concentration is too low; the resting membrane potential of the cells hyperpolarizes, moving farther from treshold |
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Term
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Definition
1. the axon terminal of the presynaptic cell
2. the membrane of the postsynaptic cell |
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Term
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Definition
| pass an electrical signal (current) directly from the cytoplasm of one cell to another through the pores of gap junction proteins |
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Term
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Definition
| use neurocrine molecules to carry information from one cell to the next; make up the vast majority of synapses in the nervous system |
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Term
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Definition
| receptor-channels that mediate rapid responses by altering ion flow across the membrane |
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Definition
| GPCRs for neuromodulators |
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Term
| 7 classes of neurocrine molecules (according to their structure) |
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Definition
1. acetylcholine
2. amines
3. amino acids
4. peptides
5. purines
6. gases
7. lipids |
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Term
From what 2 things is acetylcholine (ACh) synthesized?
*it is a chemical class by itself |
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Definition
1. choline
2. acetyl coenzyme A |
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Term
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Definition
| neurons that secrete ACh & receptors that bind ACh |
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Term
| 2 main subtypes of cholinergic receptors |
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Definition
1. nicotinic (nicotine is an agonist)
2. muscarinic (muscarine, a compound found in fungi, is an agonist) |
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Term
| From what is serotonin (5-hydroxytryptamine or 5-HT) made? |
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Definition
| the amino acid tryptophan |
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Term
| 3 things that the amino acid tyrosine is converted into |
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Definition
1. dopamine
2. norepinephrine
3. epinephrine |
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Term
| adrenergic neurons (noradrenergic neurons) |
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Definition
| neurons that secret norepinephrine |
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Term
| 2 classes of adrenergic receptors (there are multiple subtypes of each) |
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Definition
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Term
| _____ is the primary excitatory neurotransmitter of the CNS, and _____ is an excitatory neurotransmitter in selected regions of the brain |
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Definition
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Term
| gamma-aminobutyric acid (GABA) |
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Definition
| the main inhibitory neurotransmitter in the brain |
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Term
| What are AMPA receptors (ligand-gated monovalent cation channels) similar to? |
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Definition
| nicotinic acetylcholine channels |
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Term
| Where do NMDA receptors get their name from? |
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Definition
| the glutamate agonist N-methyl-D-aspartate |
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Term
| 2 peptides involved in pain sensation |
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Definition
1. substance P (involved in some pain pathways)
2. opioid peptides (enkephalines & endorphins)(mediate pain relief or analgesia) |
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Term
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Definition
| filled with neurotransmitter that is released on demand; can be seen under an electron microscope when looking at the axon terminal of a presynaptic cell |
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Term
| 5 steps in neurotransmitter release |
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Definition
1. an action potential depolarizes the axon terminal
2. the depolarization opens voltage-gated Ca2+ channels & Ca2+ enters the cell
3. calcium entry triggers exocytosis of synaptic vesicle contents
4. neurotransmitter diffuses across the synaptic clef & binds with receptors on the postsynaptic cell
5. neurotransmitter binding initiates a response in the postsynaptic cell |
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Term
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Definition
| a model of secretion where synaptic vesicles fuse to the presynaptic membrane at a complex called the fusion pore just long enough to diffuse its neurotransmitters before releasing itself back into the cell as an intact vesicle |
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Term
| acetylcholin-esterase (AChE) |
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Definition
| an enzyme that rapidly breaks acetylcholine down into choline & acetyl CoA in the ECF; exists in the extracellular matrix & the membrane of the postsynaptic cell |
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Definition
| the pattern when a group of presynaptic neurons provide input to a smaller number of postsynaptic neurons |
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Definition
| the ability of the nervous system to change activity at synapses |
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Definition
| changes in membrane potential resulting from alterations in ion flow; the response of the second messenger pathway takes longer than the direct opening or closing of a channel |
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Term
| Why is the change in membrane potential called fast synaptic potential named "fast"? |
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Definition
| it begins quickly & lasts only a few milliseconds |
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Term
| excitatory postsynaptic potential (EPSP) |
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Definition
| if the synaptic potential is depolarizing; makes the cell more likely to fire an action potential |
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Term
| inhibitory postsynaptic potential (IPSP) |
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Definition
| if the synaptic potential is hyperpolarizing; hyperpolarization moves the membrane potential away from threshold & makes the cell less likely to fire an action potential |
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Definition
| the combination of several nearly simultaneous graded potentials |
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Definition
| the type of summation if summation prevents an action potential in the postsynaptic cell |
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Definition
| summation that occurs from graded potentials overlapping in time |
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Definition
| process in which activity at a synapse brings about sustained changes in the quality or quantity of synaptic connections; opposite of long-term depression; one of the "hot topics" in neurobiology today |
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