Term
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Definition
| Almost all animals have a __ __ in which electrical impulses are transmitted along the specialized plasma membrane of nerve cells |
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Term
| central nervous system (CNS), peripherial nervous system (PNS) |
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Definition
| The nervous system has two main components: the __ __ __ ( __ ), which consists of the brain and the spinal cord, and the __ __ __ ( __ ), which comprises other sensory and motor components. |
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Term
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Definition
| Cells that make up the nervous system can be divided into two groups: __ and __ cells. |
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Term
| neurons, sensory neurons, motor neurons, interneurons |
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Definition
| All __ send or receive electrical impulsis, and can be subdivided into three basic types based on function: __ __, __ __, and __. |
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Term
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Definition
| Sensory neurons are a diverse group of cells specialized for the detection of various types of __; they provide a __ stream of information from various sensory receptors to the brain about the state of the body and its environment. |
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Term
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Definition
| Motor neurons transmit signals from the __ to the __ or gland they innervate -- that is, the tissues with which they make synaptic connections. |
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Term
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Definition
| Interneurons process signals recieved from other __ and relay the information to other parts of the __ system. |
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Term
| abundant, infection, myelin sheath, blood-brain barrier |
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Definition
| Glial cells are by far the most __ types of cells in the CNS. microglia are phagocytic cells that fight __ and remove debris. Oligodendrocytes and Schwann cells form the insulating __ __ around neurons of the CNS and those of the peripheral nerves. Astrocytes control access of blood-borne components into the extracellular fluid surrounding nerve cells, therby forming the __-__ __. |
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Term
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Definition
| Intricate networks of neurons make up the complex tissues of the brain that are responsible for coordinating __ function -- in humans about 10 billion neurons. Each neurons can receive imput from __ of other neurons, so the brain's connections number will into the trillions. |
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Term
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Definition
| The __ __ of the neuron is similiar to that of other cells and includes the nucleus and many components of the endomembrane system. |
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Term
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Definition
| Neurons also contain extensions, or branches, called __. Transporting components to and from these extentions is a special challenge for neurons. |
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Term
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Definition
| There are two types of processes: those that recieve signals and combine them with signals recieved from other neurons called __, and those that conduct signals, sometimes over long distances, are called __. |
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Term
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Definition
| The cytosol within an axon is commonly referred to as __ |
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Term
| myelin sheath, nodes of Ranvier |
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Definition
| Many vetebrate axons are surronded by a discontinuous __ __, which insulates the segments of axon separating the __ __ __. Axons can be very long -up to sever thousand times longer than the diameter of the cell body. |
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Term
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Definition
| A __ is simply a tissue composed of bundles of axons. |
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Term
| synaptic boutons, boutons, synapse |
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Definition
| The axon of a typical neuron is much longer than the dendrites and forms multiple branches, which terminate in structures called __ __. The __ are responsible for transmitting the signal to the next cell, which may be another neuron or a muscle or gland cell. In each case the junction is called a __. |
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Term
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Definition
| For neuron-to-neuron junctions, synapses usually occur between an __ and a __. |
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Term
| resting membrane potential |
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Definition
| Cells at rest normally have an excess of negative charge inside and an excess of positive charge outside the cell; the resulting electical potential is called the __ __ __, denoted Vm. |
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Term
| negative resting membrane potential |
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Definition
| The __ compare the ratio of negative to positive charge inside the cell and outside the cell. Because the inside of a cell typically has an excess of negative charge, we say that the cell has a __ __ __ __. |
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Term
| electrical excitability, action potential |
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Definition
| Nerve, muscle, and certain other cell types such as the islet cells of the pancreas of vertebrates exhibit a special property called __ __. In these cells, certain types of stimuli trigger a rapid sequence of changes in membrane potential known as __ __ --where the membrane potential changes from negative to positive values and then back to negative values again, all in as little as a few miliseconds. |
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Term
| stimulating electrode, stimulating electrode, stimulating electrode |
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Definition
| An electrode called the __ __ is connected to a power source and inserted into the axon some distance from the recording electrode. A brief impulse of this __ __ depolarizes the membrane by about 20mV, bringing the neuron beyond the threshold potential. This triggers an action potential that propagates away from the __ __. |
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Term
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Definition
| The resting membrane potential develops because the cytosol of the cell and the extracellular fluid contain different compositions of __ and __. |
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Term
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Definition
| Extracellular fluid contains dissolved salts, including sodium chloride and __ amounts of potassium chloride. The cytosol contains potassium rather than sodium as its main cation because of the action of the Na+/K+ pump. |
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Term
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Definition
| These negatively charged macromolecules cannot pass through the plasma membrane and therefore remain __ the cell. |
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Term
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Definition
| Substances tend to diffuse from an area where they are more __ concentrated to an area where they are __ concentrated. |
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Term
| inside, outside, potassium ion gradient, potassium ion gradient |
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Definition
| Cells normally have a high concentration of potassium ions __ and a low concentration of potassium ions __. We refer to this uneven distribution of potassium ions as a __ __ __. Given a large __ __ __, potassium ions will tend to diffuse out of the cell. |
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Term
| electroneutrality, counterion, anions, counterion |
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Definition
| The second principle is that of __, when ions are in a solution, they are always present in pairs (one positive on for each neagitive ion), so that theyre is not net charge imbalance. Inside the cell, potassium ions serve as the __ for the trapped __. Outisde the cell, sodium is the main cation and chloride is the __. |
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Term
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Definition
| Although a solution must have an __ number of positive and negative charges overall, these charges can be locally __ so that one region has more positive charges while another region has more negative charges. |
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Term
| electrical potential, current |
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Definition
| The tendency of oppositely charged ions toflow back toward each other is called an __ __ or voltage. When negative or positive ions are actually moving, one toward the other, we say that __ is flowing; this current is measured in amperes (A). |
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Term
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Definition
| The plasma membrane is normally permeable to potassium due to the __ of some types of potassium channels, which permits potassium ions to diffuse out of the cell. There are __ channels for negatively charged macromolecules. |
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Term
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Definition
| Because of the concentration gradient, potassium ions diffuse across the membrane from (from left to right). However, the negatively charged macromolecules are not free to follow. The result is an accumulation of anions on the __ and cations on the __ side. |
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Term
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Definition
| Although the plasma membrane is relatively impermeable to sodium ions, there is always a small amount of __. To compensate for this, the _/_ __ continually pumps sodium out of the cell while carrying potassium inward. |
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Term
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Definition
| On average, the pump transports __ sodium ions out of the cell and __ potassium ions into the cell for every molecule of ATP that is hydrolyzed. |
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Term
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Definition
| The Na+/K+ pump maintains the large potassium ion __ across the membrane that provides the basis for the __ membrane potential |
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Term
| Extracellular fluid, Cl- usually crosses the membrane together with a permeable cation (normally K+). As Cl- enters a cell, it tends to make the membrane potential more negative. |
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Definition
| Where would Cl be located in the cell? |
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Term
| Extracellular fluid: as Na+ ions enter, the neutralize some excess negative charge in the cytosol, and membrane potential becomes more positive. |
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Definition
| Where would Na+ usually be located? |
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Term
| Cytosol: K+ are more concentrated in the cytosol and have a tendency to move out of the cell, leaving behind trapped anions. membrane potential becomes more negative. |
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Definition
| Where would potassium ions usually be located? |
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Term
| chloride, cytosol, extracellular fluid |
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Definition
| The main anion in the extracellular fluid is __. As we have seen, sodium potassium, and chloride ions are the major ionic components present in both the __ and the __ __. |
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Term
| membrane potential, electrochemical gradient |
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Definition
| Because of their unequal distributions across the cell membrane, each ion has a different impact on the __ __. Each ion will tend to diffuse down its __ __ and therby producing a change in the membrane potential |
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Term
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Definition
| Potassium ions tend todiffuse out of the cell, which maked the membrane potential more __. |
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Term
| positive, depolarization, negative |
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Definition
| Sodium ions tend to flow into the cell, driving the membrane potential in the __ directionand therby causing a __ of the membrane--that is, causing the membrane potential to be less __) |
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Term
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Definition
| Chloride ions tend to diffuse into the cell, which should in principle make the membrane potential more __. However, chloride ions are also __ by the negative membrane potential, so that chloride ions usually enter the cell in association with positively charged ions such as sodium. This paired movement nullifies the depolarizing effect of the sodium entry. |
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Term
| decrease, hyperpolarization |
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Definition
| Increasing the permeability of cells to chloride can have two effects, both of which __ neuronal excitability. First, the net entry of chloride ions (chloride entry without a matching cation) causes __ of the membrane (that is membrane potential becomes more highly negative than usual). |
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Term
| chloride, chloride, neurotransmitters |
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Definition
| Second, when the membrane becomes permeable to sodium ions, some __ will tend to enter the cell along with sodium. This effect of __ entry will be prominent later when we discull inhibitory __. |
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Term
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Definition
| The establishment of a resting membrane potential and its dependence on ion gradients and ion permeability are properties of almost __ cells. |
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Term
| membrane depolarization, resting membrane potential, action potential |
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Definition
| The unique feature of electrically excitable cells is their response to __ __. Wheras a nonexcitable cell that has been temporarily and slightly depolarized will simply return to its origional __ __ __, an electrically excitable cell that is depoarized to the same degree will respond with __ __. |
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Term
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Definition
| Electrically excitable cells produce and action potential because of __-__ __ in the plasma membrane. |
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Term
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Definition
| In general, __ __ are integral membrane proteins that form ion-conducting pores through the lipid bilayer. |
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Term
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Definition
| __-__ ion channels, respond to changes in the voltage across a membrane. |
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Term
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Definition
| Voltage-gated sodium and potassium channels are responsible for the __ __. |
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Term
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Definition
| __-__ ion channels open when a particular molecule binds to the channel. |
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Term
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Definition
| Other channels contribute to the steady-state ionic permeabilities of membranes. these __ __ allow resting cells to be somewhat permeable to cations, in particular potassium ions. |
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Term
| Voltage-gated potassium channels, voltage-gated sodium channels |
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Definition
| The structure of voltage-gated ion channels fall into two different, though similar, categories: __-__ __ __ and __-__ __ __. |
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Term
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Definition
| Voltage-gated potassium channels are __ proteins--that is, they consist of several separate protein subuints that associate with one another to form the functional channel. |
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Term
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Definition
| Voltage-gated sodium channels, are large, __ proteins--consist of a single polypeptide--with 4 separate domains. Each domain is similar to one of the subunits of the voltage-gated potassium channel. |
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Term
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Definition
| In both kinds of channels, each subunit or domain contains __ transmembrane __ helices (called subunits S1-S6). |
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Term
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Definition
| The size of the central pore and, more importantly the way it interacts with an ion, give a channel its __ __. |
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Term
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Definition
| Oxygen atoms in amino acids lining the center of the channel are precisely positioned to interact with ions as they move through the __ __, allowing them to give up their waters of hydration |
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Term
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Definition
| The fit between K+ ions and oxygens lining the channel is remarkably __. Na+, which is smaller than K+, can only interact with oxygen atoms on __ __ of the channel. This makes the entertically unfavorable for Na+ to give up its waters of hydration and enter the channel. |
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Term
| channel gating, all-or-none |
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Definition
| Voltage-gated sodium channels have the ability to open rapidly in response to some stimulus and then to close again, a phenomenon know as __ __. This open or closed state is an __-__-__ phenomenon --that is, gates do not appear to remain partially open. |
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Term
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Definition
| Most voltage-gated channels can also adopt a second type of closed state, referred to as __ __, which is an important feature of voltage-gated sodium and potassium channels. |
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Term
| stimulated, inactivating particle |
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Definition
| When a channel is inactivated, it cannot reopen immediately, even if __ to do so. It's lke placking a padlock on a closed gate;only when the padlock os unlocked can the gate be opened again. Inactivation is caused by a portion of the canned called the __ __. |
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Term
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Definition
| Defects in several voltage-gated ion channels have been linked to human __ diseases such as epilepsy. |
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Term
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Definition
| An ion gradient across a selectively permeable membrane can generate a __ __. |
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Term
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Definition
| A resting neuron is a system __ for electrical action |
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Term
| gradients, permeability, depolarization |
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Definition
| The membrane potential of the cell is set by a delicate balance of ion __ and ion __. __ of the membrane upsets this balance. |
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Term
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Definition
| If the depolarization of the membrane is small, the membrane potential will normally drop back to __ levels without further consequences. |
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Term
| threshold potential, threshold potential, action potential |
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Definition
| Further depolarization brings the membrane to the __ __. Above the __ __, the nerve cell membrane undergoes rapid and dramatic alterations in its electrical properties and permeability to ions, and an __ __ is initiated. |
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Term
| action potential, inward, outward |
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Definition
| An __ __ is a brief but large electrical depolarization and repolarization of the neuronal plasma membrane caused by the __ movement of sodium ions and the subsequent __ movement of potassium ions |
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Term
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Definition
| These ion movements are controlled by the opening and closing of voltage gated __ and __ channels. |
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Term
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Definition
| Once an action potential is initiated in one region of the membrane, it will travel along the membrane away from the site of origin by a process called __. |
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Term
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Definition
| Most axons in vertebrates have an additional specialization: They are surrounded by a discontinuous __ __ consisting of many concentric layers of membrane. |
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Term
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Definition
| The myelin sheath is a reasonably effective electrical __ for the segments of the axon that it envelops. |
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Term
| oligodendrocytes, Schwann cells |
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Definition
| The myelin sheath of neurons in the CNS is formed by __; in the PNS, the myelin sheath is formen by __ __, each of which wraps layer after layer of its own plasma membrane around the axon in a tight spiral. |
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Term
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Definition
| Because each Schwann cell surrounds a short segment of a single axon, __ Schwann cells are required to encase a PNS axon with a discontinuous sheath of myelin. |
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Term
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Definition
| Myelination __ the ability of the neuronal membrane to retain electric charge (i.e. myelination __ its capacitance), permitting a depolarixation event to spread farther and faster than it would aldon a nonmyelinated axon. |
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Term
| propagation, renewed, nodes of Ranvier |
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Definition
| Myelination does not eliminate the need for __. For depolarization to spread from one site to the rest of the neuron, the action potential must still be __ periodically down the axon. This happens at the __ __ __, interruptions in the myelin layer that are spaced just close enough together to ensure that depolarization spreading out to form an action potential at one node is still strong enough to bring an adjacent node above its threshold potential. |
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Term
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Definition
| The nodes of Ranvier are the only places on a myelinated axon where an action potential can be __ because current flow through the membrane is restricted elsewhere and because voltage-gated __ channels are concentrated there. |
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Term
| action potentials, saltatory propagation |
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Definition
| Thus, __ __ jump from node to node along myelinated axons rather than moving as a steady ripple along the membrane. This so called __ __ is much more rapid than the continuous propagation that occurs in nonmyelinated axons. |
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Term
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Definition
| Myelination is a crucial feature of __ axons. Loss of myelination results in a dramatic decrease in the __ resistance of the axonal membrane. Much like the flow of water through a leaky garden hose, this loss of resistance dramatically reduces conduction velocity along an axon. |
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Term
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Definition
| __ __ results when a patient's immune system attacks his or her own myelinated nerve fibers, causing demyelination. |
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Term
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Definition
| Nodes of Ranvier are highly __ structures that involve close contact between the loops of glial or Schwann cell membrane and the plasma membrane of the axon(s) they myelinate. |
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Term
| sodium, paranodal, septate, juxtaparanodal |
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Definition
| Three distinct regions are associated with these specialized sites of contact. In the node of the Ranvier itself, voltage-sensitive __ channels are highly concentrated. In the adjacent regions, called __ regions, the axonal and glial cell membranes contain specialized adhesive proteins that are similiar to those in __ junctions. Finally, the region next to the paranodal areas, called the __ regions, potassium channels are highly concentrated. |
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Term
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Definition
| The organization of nodes of Ranvier prevents __ movement of the sodium and potassium channels within the axon's plasma membrane in regions around the nodes. |
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Term
| K+, Sodium/Potassium pump, Resting potential |
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Definition
| For the firing of a neuron to occur, there is a high concentration of __ inside the plasma membrane, that will leak out and cause the cell to become more -. To try and compensate for this, the __/__ __ will try and counteract whats going on by bringing in more Na+. This is constantly going on to keep the cell at the __ __. |
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Term
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Definition
| The mechanism for the transmission of an action potential along a nonmyelinated axon occurs in 5. Ultimately, the stimulation of a resting membrane results in a __ of the membrane and a sudden rush of __ ions into the axon at that location. |
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Term
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Definition
| Step 1: Membrane polarity is temporarily __ at that point, and this depolarization then spreads to an adjacent point. |
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Term
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Definition
| Step 2: The depolarization at this adjacent point is sufficient to bring it above the threshold potential, triggerng the inward rush of __ ions. |
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Term
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Definition
| Step 3: By this time, the origional region of the membrane has become highly permeable to __ ions. |
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Term
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Definition
| As the potassium ions rush out of the cell, __ polarity is restored and that portion of the membrane reterns to its __ __. |
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Term
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Definition
| Step 5: Meanwhile, the __ has spread to a new region, initiating the same sequence of events there. |
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Term
| porpagated action potential, Nerve implule |
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Definition
| The propagation of this cycle of events along the nerve fiber is called a __ __ __, or __ __, which can move only away from the initial depolarization because the sodium channels that have just been depolarized are in the inactivated state and cannot respond immediatley to further stimulation. |
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Term
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Definition
| Because an action potential is actively propagated, it does not __ as it travels. The reason is that it is generated anew, as an all-or-none event, at each successive point along the membrane. Thus, a nerve impulse can be transmitted over essentially any distance with no __ in strength. |
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Term
| nodes of Ranvier, K+, Na+, saltatory propagataion |
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Definition
| The transmission of an action potential along the myelinated axon: action potential can only be generated at the __ __ __, therefore, at each node we have a large concentration of volatge-gated sodium channels since at each node, we need the __ to leave and and __ to enter causeing the repolarization and depolarization (respectively). Because it only has to be regenerated at each node instead of along the entire nerve, this __ __ is much more rapid. |
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Term
| synapses, electrical, chemical |
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Definition
| Nerve cells communicate wih one anoher and with glands and muscles at __. There are two structurally distinct types of them: __ and __. |
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Term
| presynaptic, postsynaptic, gap junctions |
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Definition
| In an electrical synapse, one neuron, the __ neuron, is conncted to a second neuron, the __ neuron, by __ __. As ions move back and forth between the two cells, the depolarization in one cell spreads passavily to the connected cell. |
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Term
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Definition
| Electrical synapses provide for transmission with virtually no __ and occur in places in the nervous system where speed of __ is critical. Similiar electrical connections can be found between nonneuronal cells, such as the cardiac muscles in the heart. |
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Term
| cell adhesion ,synaptic cleft |
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Definition
| In chemical synapse, the presynaptic and postsynaptic neurons are not connected by gap junctions, although they are connected by __ __ proteins. Instead the presynaptic plasma membrane is separated from the postsynaptic plasma membrane by a small space known as the __ __. |
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Term
| chemical signal, neurotransmitter, synaptic boutons, postsynaptic |
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Definition
| For synaptic transmission to take place, the electrical signal must be converted at the presynaptic neuron to a __ __ carried by a __, which are stored in the __ __ of the presynaptic neuron. An action potential arriving at the terminal causes the neurotransmitter to be secreted into and diffuse across the synaptic cleft. The neurotransmitter molecules then bind--normally not immediately-- to specific proteins embedded within the plasma membrane of the __ neuron (receptors) and are converted back into electrical signals, setting in motion a sequence of events that either stimulates of inhibits the production of an action potential in the postsynaptic neuron, depending of the kind of synapse. |
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Term
| ligand-gated ion channels, ligand-gated channels, postsynaptic |
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Definition
| Neurotransmitter receptors fall into two broad groups: __-__ __ __ (sometimes called ionotropic receptors), in which activation directly affects the cell, and receptors that exert their effects indierctly through a system of intracellylar messengers (sometimes called metabotropic receptors), or the __-__ __, these membrane ion channels open in response to the binding of a neurotransmiter, and they can mediate either excitatory or inhibitory responses in the __ cell. |
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Term
| channels, connexon, connexins |
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Definition
| For the electrical synapse, we have gap junctions-- the whole thing (from the inside of the presynaptic to the inside of the postsynaptic) is called a __. Which is made up of larger proteins (the actual channel) called __. Which are made up of __. |
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Term
| neurotransmitter, neurotransmitter |
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Definition
| A __ is essentially any signaling molecule released by a neuron. Many kinds of molecules can serve as __, and most are detected by the postsynaptic cell by a specific type of receptor. |
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Term
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Definition
| When a neurotransmitter molecule binds to its receptor, the properties of the receptor are altered, and the __ neuron responds accordingly. |
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Term
| excitatory receptor, inhibitory receptor |
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Definition
| An __ __ causes depolarization of the postsynaptic neuron, wheras an __ __ typically causes the postsynaptic cell to hyperpolarize |
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Term
| synaptic cleft, presynaptic, stimulated |
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Definition
| To qualify as a neurotransmitter, a compound must satisfy 3 criteria: 1: it must elicit the appropriate response when introduced into the __ __. 2: It must occur naturally in the __ neuron. 3: It must be released at the right time with the presynaptic neuron is __. |
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Term
| acetylcholine, excitatory neurotransmitter, increases, Na+, cholinergic synapses |
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Definition
| In vertebrates, __ is the most common neurotransmitter for synapses between neurons outside the CNS, as well as for neuromuscular junctions. Its an __ __, that __ the permeability of the postsynpatic membrane to __. Synapses that use this molecule as their neurotransmitter are called __ __. |
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Term
| Catecholamines, adrenergic synapses, nerves, smooth muscles |
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Definition
| The __ include dopamine, and the hormones norepinephrine and epinephrine, all derivatives of the amino acid tyrosine. They are also synthesized in the adrenal gland, so synapses that use them as neurotransmitters are termed __ __ which are found at the junctions between __ and __ __ in internal organs such as the intestines, as well as at nerve-nerve junctions in the brain. |
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Term
| CNA, excitatory neurotransmitter, close, opening, inhibitory neurotransmitters, excitatory |
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Definition
| Other neurotransmitters that consist of amino acids and derivatives include histamine, serotonin, and GABA, as well as glycine and glutamate. Serotonin functions in the __. It is considered an __ __ because it indirectly causes potassium channels to __, which has an effect similiar to __ sodium channels in that the postsynaptic cells is depolarized. However, its effect is exerted much more slowly that that of sodium chanels. GABA and glycine are __ __., wheras glutamate has an __ effect. |
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Term
| neuropeptides, excite, inhibit, modify, long-lasting |
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Definition
| Short chains of amino acids called __ are formed by proteolytic cleavage of precursor proteins. Some exhibit characteristics similiar to neurotransmitters in that they __, __, or __ the activity of other neurons in the brain. However, they differ from typical neurotransmitters in that they act on groups of neurons and have __-__ effects. |
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Term
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Definition
Examples of neuropeptides include: enkephalins, which are
__ produced in the mammalian brain and __ the activity of neurons in regions of the brain ivolved in perception of pain. Some pharmaceuticals that contain these are: morphine, codine, demerol and marijuana is derived from the leaves from a olant that contains this substance in it. |
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Term
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Definition
direct neurotransmitter action
[image] |
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Term
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Definition
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Term
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Definition
| For the neurotransmitter to act on a postsynaptic cell, it must be secreted by the process of __, in which the neurosecretory vesicle fuses with the plasma membrane, discharging the vesicle's contents into the synaptic cleft. |
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Term
| synaptic bouton, presynaptic, docked |
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Definition
| When an action potential arrives at an axon terminal and triggers the opening of voltage-gated calcium channels, calcium enters the __ __. Neurosecretory vesicles near the plasma membrane are now capable of fusing with the plasma membrane of the __ neuron. Because this can occur very rapidly, vesicle fusion is thought to involve vesicles tha are already "__" at the plasma membrane. |
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Term
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Definition
| Docking and fusion of neurosecretory vesicles with the plasma membrane of the active zone are mediated by _- and _- __ proteins, just as we say with other exocytosis events. |
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Term
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Definition
| The calcium "sensor" involved in coordinated docking of vesicles appears to be the protein synaptotagmin, which can bind __;when it does, it undergoes a __ change that allows the t- and v-SNARE complexes to interact effeciently. |
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Term
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Definition
| Docking takes place at a specialized site, called the __ __, within the membrane of the presynaptic neuron. It's a highly organized structure. |
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Term
| proximity, rapid, stimulated |
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Definition
| Synaptic vesicles and the calcium channels that elicit their release are found in close __ to one another, which helps to explain the extremely __ fusion of docked vesicles with the presynaptic neuron's plasma membrane with that neuron is __. |
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Term
| neurotoxin, spinal cord, motor neurons |
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Definition
| Tetanus and botulism result from interference by __ with vesicle docking and release. Tetanus toxin prevents the release of the neurotransmitter from inhibitory neurons in the __ __ resulting in uncontrolled muscle contraction, and botulinum toxin prevents the release of the neurotransmitter from __ __ resulting in muscle weakness/paralysis. |
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Term
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Definition
| Exocytosis of vesicles involves addition of the vesicle's membrane to the __ __. |
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Term
| presynaptic, compensatory endocytosis |
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Definition
| When neurons release man neurosecretory vesicles in rapid succession, this has the potential to lead to accummulation of excess membrane in the __ nerve terminal. Neurons solve this by __ __: which relies on the formation of clathrin-dependent vesicles, which allow the recycling of membranes and therby maintains the size of the nerve terminal. |
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Term
| kiss-and-run exocytosis, some, reseals |
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Definition
| In cases in which neurons need to fire very rapidly, they may use a more transient method for the release of neurotransmitter, called the __-__-__ __. In this case a vesicle may temporarily fuse with the plasma membrane by a tiny opening, causing release of __ neurotransmitter from the vesicle. The vesicle then rapildy __ without the added step of complete fusion with the plasma membrane. |
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Term
| detected, receptor, specific |
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Definition
| When neurotransmitters are secreted across a synapse, their presence must be __ by the postsynaptic cell. Typically this response requires a protein __, which binds the neurotransmitter and mediates the response of the postsynaptic neuron. Different neurotransmitters are bound by __ receptors. |
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Term
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Definition
| For neurons to transmit signals effectively, it is just as important to turn the stimulus __ as it is to turn it on. Whether excitatory or inhibitory, once the neurotransmitter has been secreted, it must be rapidly __ from the synaptic cleft. If it were not, stimulation or inhibition of the postsynaptic neuron would be abnormally __ even without further signals from presynaptic neurons. |
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Term
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Definition
| Neurotransmitters are removed from the synaptic cleft by two specific mechanisms: __ into inactive molecules or __. |
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Term
| hydrolyzes, acetic acid, choline |
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Definition
| Degradation into inactive molecules is exemplified by acetylcholine. The enzyme acetylcholinesterase __ acetylcholine into __ __ and __, neither of which stimulates the acetylcholine receptor. Puring nucleotide neurotransmitters are also degraded by specific enzymes. |
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Term
| pumping, axon terminals, support cells, rapid, increase |
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Definition
| Neurotransmitter reuptake involves __ neurotransmitters back into the presynaptic __ __ or nearby __ __. The rate of neurotransmitter reuptake can be __; for some neurons, the synapse may be cleared of stray neurotransmitter within as little as a millisecond. For example: Prozac blocks the reuptake of serotonin, leading to a local __ in the level of serotonin avilable to postsynaptic neurons. (endocytosis) |
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Term
| When the nerve impulse from the presynaptic axyn arrives at the synapse, it causes synaptic vesicles contianing neurotransmitters in the synaptic couton to fuse with the presynaptic membrane releasing its contents into the synaptic cleft. |
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Definition
| When does the presynaptic nerve cell know when to secrete the synaptic vesicles? |
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Term
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Definition
| Secretion of neurotransmitters by presynaptic cell is directly controlled by the concentration of __ ions in the synaptic __. |
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Term
| depolarization, voltage-gated calcium channels, rush |
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Definition
| Each time a action potential arrives, the __ causes the calcium concentration in the synaptic bouton to increase temporarily due to the opening of __-__ __ __ in the synaptic boutons. Normally, the cell is relatively impermeably to calcium ions, so that the cytosolic calcium concentration remains low. However, there is a very large concentration gradient o calcium across the membrane because the calcium concentration outside the cell is about 10,000 times higher than that of the cytosol. As a result, calcium ions will __ into the cell when these channels open. |
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Term
| neurosecretory vesicles, synaptic boutons |
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Definition
| Before they are released, neurotransmitter molecules are stored in small, membrane-bounded __ __ in the __ __. |
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Term
| rapid release, dock, fuse, axon terminal |
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Definition
| The release of clacium within the synaptic bouton has two main effects on neurosecretory vesicles. First, vesicles held in storage are mobilized for __ __. Second, vesicles that are ready for relase rapidly __ and __ with the plasma membrane in the synaptic bouton region. During this process, the membrane vesicle moves into close contact with the plasma membrane of the __ __ and the fuses with it to release the contents of the vesicle. |
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Term
shut down the Ca+ channel.
block the v- and t-SNAREs |
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Definition
| If you want to stop the signal from being passed there are two ways which are? |
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