5 - Nervous system 2 : Synaptic Transmission
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Put these statements into the correct order for synaptic transmission:
a. Neurotransmitter diffuses across the synaptic cleft.
b. The presence of calcium inside the cell causes the synaptic vesicles to fuse with the membrane.
c. Most often, the neurotransmitter is pumped back into the presynaptic terminal and into nearby glial cells.
d. An action potential in the axon terminal causes voltage-gated calcium channels to open and calcium to enter the terminal.
e. Each vesicle releases a fixed amount of neurotransmitter into the synaptic cleft.
f. Neurotransmitter binds to a receptor on the postsynaptic neuron where it can act. - postsynaptic neuron
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Neurotransmitter binds to a receptor on the ___________ __________ where it can act directly or indirectly.
a. postsynaptic neuron
b. presynaptic neuron - neurotransmitter
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Chemically-gated ion channels remain open as long as the ___________ is bound to the receptor, and are not sensitive to changes in the membrane potential.
a. synapse
b. neurotransmitter
c. ion - b. depolarize, hyperpolarize
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Synaptic current, or ion movement through chemically-gated channels, may _____________ or ___________ the neuron.
a. excite or inhibit
b. depolarize, hyperpolarize - b. neurotransmitter
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Synaptic transmission ends when the _____________ dissociates from the receptor and is removed from the synaptic cleft.
a. synapse
b. neurotransmitter
c. ion - b. presynaptic terminal
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Most often, the neurotransmitter is pumped back into the __________ __________and into nearby glial cells.
a. postsynaptic neuron
b. presynaptic neuron - A. acetyl choline
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In some cases, the neurotransmitter is broken down by enzymes, and the breakdown products are pumped away. The neurotransmitter __________ ___________ is an example of this process.
a. acetyl choline
b. GABA
c. norepinephrine
d. glycine - a. presynaptic terminal
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When breakdown products are transported into the ____________ __________, they are used to resynthesize neurotransmitter.
a. presynaptic terminal
b. postsynaptic terminal -
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Put these statements in order:
a. Neurotransmitter diffuses across the synaptic cleft and binds to the postsynaptic receptor .
b. The voltage-gated calcium channels open and calcium diffuses into the axon terminal .
c. Neurotransmitter dissociates from the receptor and is pumped back into the axon terminal.
d. The synaptic vesicles fuse with the presynaptic cell membrane and open.
e. An action potential occurs in the presynaptic terminal.
f. Current flows across the postsynaptic cell membrane. - A. postsynaptic receptors
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We have examined the mechanism of synaptic transmission. Now let’s look at the consequences of synaptic activity on the postsynaptic cell. The action of the ______________ _______ depends on which neurotransmitter is involved, and the specific receptor found on that cell.
a. postsynaptic neuron
b. presynaptic neuron - a. nicotine, muscarine
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There are two groups of receptors, called cholinergic receptors, which bind acetylcholine. One group also binds the chemical ________; the other group also binds the chemical __________.
a. nicotine, muscarine
b. alpha receptors, beta receptors - b. nicotinic
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At this receptor, acetylcholine acts directly to open an ion channel producing a fast excitatory postsynaptic potential. Acetylcholine is excitatory at ________ receptors. It causes skeletal muscle to contract.
a. muscarinic
b. nicotinic
c. alpha
d. beta - a. muscarinic
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Acetylcholine is excitatory at these ____________ receptors, causing neurons to fire action potentials, and smooth muscle to contract.
a. muscarinic
b. nicotinic
c. alpha
d. beta - a. mACH
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Acetylcholine acts indirectly at these _____ receptors producing a slow excitatory postsynaptic potential.
a. mACh
b. nACh - c. heart
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A second type of mACh receptor is found in the central nervous system, and in the _______.
a. lungs
b. kidney
c. heart
d. liver - b. slow inhibition, decreases
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Acetylcholine acts indirectly at these receptors, producing a _______ ___________of the postsynaptic cells. In the heart, this effect _________ the heart rate.
a.fast excitation, increasing
b. slow inhibition, decreases - a. hyperpolarize
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Acetylcholine is inhibitory at these muscarinic receptors causing neurons to __________, and the heart to slow down.
a. hyperpolarize
b. depolarize - a. postsynaptic neuron
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The action of acetylcholine may be excitatory or inhibitory. The effect depends on which receptor is present on the _________ _______.
a. postsynaptic neuron
b. presynaptic neuron - e. alpha and beta
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There are two families of receptors for the neurotransmitter norepinephrine, _______ receptors and ______ receptors.
a. muscarinic
b. nicotinic
c. alpha
d. beta
e. alpha, beta - a. adrenergic
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.) These are called _________ receptors, and norepinephrine acts indirectly when binding to them.
a. adrenergic
b. cholinergic - a. sympathetic nervous system
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Both alpha and beta adrenergic receptors are found in the central nervous system, and more importantly, on effector organs of the _____________ ___________ ___________.
a. sympathetic nervous system
b. parasympathetic nervous system - c. blood vessels
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Norepinephrine acts indirectly at alpha-one receptors to produce slow excitation. This causes smooth muscle to contract. Alpha-one receptors are located on ______ ______, which supply the skin, mucosae, and abdominal viscera. Norepinephrine is excitatory at alpha one receptors.
a. heart
b. lung
c. blood vessels - a. heart rate
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Norepinephrine also acts indirectly at beta-one receptors in the heart to produce slow excitation. ________ ______ and strength of contraction increase. Norepinephrine is excitatory at beta one receptors.
a. Heart rate
b. Lung rate
c. Skeletal muscle - c. dilate, respiratory, skeletal
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Norepinephrine acts indirectly at beta-two receptors, to produce a slow inhibition. This causes smooth muscle to _______. Beta-two receptors are located on the ________ airways, blood vessels that supply _______ muscle and heart, and most other effector organs of the sympathetic system. Norepinephrine is inhibitory at beta-two receptors.
a. constrict, respiratory, smooth
b. constrict, respiratory, heart
c. dilate, respiratory, skeletal - a. acetyl choline, norepinephrine
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We have learned that ________ ________ and _______________ are found in the central nervous system and at effector organs of the nervous system.
a. acetyl choline, norepinephrine
b. GABA and glycine - b. acetylcholine, cholinergic, nACh
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Motor neurons of the somatic nervous system release __________. They are __________. Skeletal muscles bear ____ receptors.
a. norepinephrine, adrenergic, alpha
b. acetylcholine, cholinergic, nACh - b. excitatory
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Thus the action of acetylcholine on skeletal muscle is direct, fast, and _________.
a. inhibitory
b. excitatory - slow excitation
- Norepinephrine acts in directly at alpha-one receptors to produce _____ __________.
- a. cholenergic
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The first of two neurons in the sympathetic chain, the preganglionic neuron, is _________.
a. cholinergic
b. adrenergic - a. cholinergic
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The first of two neurons in the parasympathetic chain, the preganglionic neuron, is also ________.
a. cholinergic
b. adrenergic - b. nACh
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The second neuron, or postganglionic neuron, in both the sympathetic and parasympathetic chains, has ______ receptors.
a. mACh
b. nACh
c. alpha
b. beta - a. norepinephrine, adrenergic
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Sympathetic postganglionic neurons release ___________. They are _________.
a. norepinephrine, adrenergic
b. acetyl choline, cholinergic - b. acetyl choline, cholinergic
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Parasympathetic postganglionic neurons release ___________. They are __________.
a. norepinephrine, adrenergic
b. acetyl choline, cholinergic - a. sodium, potassium
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.) Glutamate is the most common and most potent excitatory neurotransmitter in the central nervous system. Glutamate acts directly on ion channels that permit passage of both _______ and _______, producing fast excitatory postsynaptic potentials.
a. sodium, potassium
b. chloride - b. chloride
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The major inhibitory neurotransmitters in the central nervous system are GABA and glycine. Like GABA, glycine binds to receptors which directly open ___________ channels, producing fast inhibitory postsynaptic potentials.
a. sodium, potassium
b. chloride - synaptic cleft
- The space between the axon terminal and the membrane of the target cell. For example, the space between the axon terminal and the folded region of the muscle cell membrane called the motor end plate.
- Cholinergic
- Associated with acetylcholine (ACh).
- Adrenergic
- Associated with norepinephrine (NE) and epinephrine (adrenaline).
- Inhibitory postsynaptic potential (IPSP)
- A local, graded, hyperpolarization of an excitable cell. Functions to prevent generation of an action potential in a postsynaptic cell.
- hyperpolarize
- To change the membrane potential of a cell to a value that is more negative than its resting membrane potential.
- depolarize
- To change the membrane potential of a cell to a value that is more positive than its resting membrane potential.