Chapter 3 Study Questions Flashcards
Like other body cells, the neuron under steady state conditions exhibits a slight _______ different b/t the inside of its cell membrane and the outside. This is known as the _______ potential. This potential is attributable to differential concentrations of _______ inside the cell relative to the outside, and is about -50 to -80 _______ in magnitude.
electrical; resting membrane; ions; millivolts
Positively charges ions are called _______, and negatively charged ions are called _______. Since the inside of a resting cell is negative relative to the outside, _______ on the outside of the cell will be attracted to the intracellular fluid and _______ will be repelled by it.
cations; anions; cations; anions
A second force that helps determine the distribution of ions is the concentration _______, which refers to the propensity of ions to move from regions of _______ concentration to areas of _______ concentration. Neuronal membranes exhibit selective _______, which means that the types of _______ _______ present in the membrane determine the types of ions that can be moved by these forces through the cell membrane. Neurons at rest re selectively permeable to _______.
gradient; high; low; PERMEABILITY; ION CHANNELS; POTASSIUM
Proteins are large anions within a neuron that create a ______ charge that tends to pull potassium ions into the cell. However, there are already about _______ times as many potassium ions inside the neuron as there are outside, so the ______ tends to push potassium ions out of the cell. Eventually the 2 forces are exactly balanced, yielding the neuron’s _______ potential, which corresponds to the potassium _______ potential, in the range of -50mV to -80 mV.
negative; FIVE; CONCENTRATION GRADIENT; resting; EQUILIBRIUM
The exact value of a given neuron’s resting membrane potential can be predicted by means of the _______ equation. However, the measured value is generally slightly less negative than the predicted value, due to they leakage of _______ ions into the neuron. The cell employs _______ pumps to actively counter this leakage; if it did not, the cell’s resting potential would eventually be at _______ mV.
Nernst; SODIUM (NA+); sodium-potassium; zero
The generation of an action potential is critically dependent on _______ -gated _______ channels. At threshold depolarization, these channels start to open, and the depolarization caused by the entry of _______ into the axon causes still more _______ -gated channels to open, until _______ floods in and causes the membrane potential to suddenly become _______. The sodium channels are open for a little less than _______ ms. Positive charges inside the cell then push _______ ions out, and the resting potential is reap idly restored, although brief oscillations called _______ are observed.
voltage; sodium; voltage; sodium; POSITIVE; ONE (1); potassium; AFTERPOTENTIALS
Increasingly strong depolarizing stimuli are also _______ mirrored by the neuronal membrane, up to the point at which the cell’s _______ depolarization is reached. At this point, a brief _______ potential is produced, consisting of a positive membrane potential that is propagated along the length of the _______.
PASSIVELY; threshold; action; axon
An action potential is generated in its full form or not at all, called the _______ property. The stimulus is encoded in _______ rather than _______ of action potentials.
all-or-none; FREQUENCY; AMPLITUDE
Axonal membrane as an action potential is generated
Membrane State State of gated K+ channels “ “Na+”
Resting
Depolarization
Threshold depolarization and action potential generated
Action potential collapses
closed; closed CLOSED; some open CLOSED; many open open; closed closed; closed
The active membrane, while firing the action potential, acts as a _______ membrane. The Nernst equation predicts the membrane potential of such a membrane to be _______ mV, which corresponds to the _______ voltage of the action potential.
sodium; +40; peak
The action potential starts at the _______, which is studded with voltage-gated _______ channels, and its is recreated at successive positions down the length of the axon; in other words, the action potential _______ itself.
axon hillock, sodium, REGENERATES
_______ provides insulation around axons, forcing action potentials to jump between nodes of _______. This process, termed _______ conduction, promotes much _______ propagation of the action potential along the length of the axon.
myelin; Ranvier; saltatory; faster
During the absolute refractory period, the membrane potential has collapsed (so there is no scope for further depolarization), and the _______ channels are inactivated. During the relative refractory phase, _______ flows out of the cell, so the membrane potential is partially restored and a very _______ stimulation may elicit a second action potential.
sodium; K+; strong
A _______ is a medical condition in which the form and function of ion channels is altered as a result of genetic _______.
CHANNELOPATHY; mutation
TTX is short for _______, and STX is short for _______; both TTX and STX selectively block the outer part of _______, preventing neurons from producing _______ potentials.
TETRODOTOXIN; SAXITOXIN; SODIUM; ACTION
Invertebrate axons lack _______, and instead rely on large-_______ axons to carry action potentials quickly. Such _______ axons usually mediate important behaviors, such as _______ movements, but even so, they are only as fast as _______ myelinated fibers in vertebrates. When an action potential arrives at the axon _______ of an excitatory presynaptic neuron, a local, graded _______, known as an _______ potential, is produced in the posynaptic cell. If the presynaptic cell is inhibitory, then an IPSP is produced on the postsynaptic cell instead, generally as a consequence of the opening of the _______ channels. A single neuron may be subject to hundreds of _______ potentials at any given time, each produced by the action of _______ substance at chemical synapses. The decision to produce an _______ generally depends on the effect of numerous EPSPs and IPSPs working together. Whether or not a synapse producers an IPSP or EPSP generally depends on the particular _______ used by that synapse.
myelination; DIAMETER; giant; ESCAPE; TERMINAL; depolarization; excitatory POSTSYNAPTIC; CL-; POSTSYNAPTIC; neurotransmitter; action potential; TRANSMITTER
Electrical synapses are found where conduction must occur very _______, such as in circuits involved in _______ behavior, and also in regions where a large number of fibers must be activated _______, such as in the oculomotor system.
rapidly; escape; SIMULTANEOUSLY
Electrical synapses feature special _______ ion channels line dup on both sides of the synapses, which allow _______ to flow directly from the presynaptic cell into the postsynaptic cell across a very _______ cleft. Transmission at these synapses resembles the conduction along a cell’s _______.
LARGE; IONS; SMALL; axon
Incoming information, in the for of EPSPs and_______, is integrated in the postsynaptic neuron through the process of _______ There are two mechanisms by which thos occurs:
- _______ summation is the addition of two potentials that occur close together in _______.
- _______ summation is the addition of two potentials that occur close together physically on the cell membrane.
IPSPs; SUMMATION; TEMPORAL; TIME; SPATIAL
Imagine a simplified neuron (lacking dendrites) with 4 synapses on the cell body–2 inhibitory and 2 excitatory. Pick the correct net (i.e. postsummation) effect on the cell’s membrane of each of the following situations.
- When 1 excitatory synapse fires (extent…effect)
- When 1 inhibitory synapse fires
- When both excitatory synapses fire simultaneously
- When both inhibitory synapses fire simultaneously
- When one excitatory synapse and one inhibitory synapse fire simultaneously
- When all four synapses fire simultaneously
- When one excitatory synapse fires several times in rapid succession
- First an inhibitory synapse fires, then a few moments later an excitatory synapse fires (think carefully before answering this one!)
- MODERATE depolarization
- MODERATE hyperpolarization
- larger depolarization
- larger hyperpolarization
- no change
- no change
- LARGER depolarization
- SLIGHT DEPOLARIZATION
Imagine a simplified neuron (lacking dendrites) with four synapses on the cell body—two inhibitory and two excitatory. A pattern of firing that would provide the maximal likelihood of producing an action potential would be rapid repeated firing at both _______ synapses with no firing at _______ synapses, thus maximizing the likelihood of a threshold _______. This is because both _______ and spatial summation of the EPSPs would occur, with no _______.
excitatory; inhibitory; depolarization; temporal; IPSP’S
The presence of dendrites adds additional information processing to the neuron because the _______ postsynaptic potentials must spread passively along dendrites; consequently, they tend to be _______ in terms of their proximity to the cell body. The farther out on the dendrite a _______ potential occurs, the less overall effect it can have at the axon _______. Glia can _______ the overall strength of the postsynaptic potentials, perhaps by preventing _______ leakage from synapses.
graded; WEIGHTED; graded; hillock; increase; neurotransmitter
There is a delay between the arrival of the presynaptic action potential and the postsynaptic action potential because most synapses are _______ ; the presynaptic potential is first translated into _______release and then back into an _______ signal on the postsynaptic side.
CHEMICAL; NEUROTRANSMITTER; ELECTRICAL
Put events in order.
A _______ potential (EPSP or IPSP) spreads toward the axon hillock.
Postsynaptic _______ respond by opening ion channels.
Synaptic transmitter is rapidly_______.
Presynaptic action potential propagates to the _______.
Neurotransmitters are removed rapidly from the synaptic cleft by transporters.
Calcium influx induces synaptic vesicles to fuse to the _______ membrane and release neurotransmitter.
Volatage-gated _______ channels open.
(GOT ALL STEP #S WRONG) 5. GRADED 4. RECEPTORS 6. INACTIVATED 1. AXON TERMINAL 7. 3. presynaptic 2. calcium
(my guess: 1,5,3,2,4,7,6) (chemical, membrane, fired, axon hillock)
When an action potential arrives, the membrane of the axon terminal becomes more permeable to _______ . The amount of _______ that then enters the cell determines the amount of _______ released: A large influx of _______ into the cell causes more vesicles to discharge their contents than does a small influx. Processes associated with the entrance of _______ into the axon terminal are the main cause of synaptic _______.
calcium; calcium; neurotransmitter; calcium; calcium; DELAY
Imagine that a single vesicle discharges its transmitter into the cleft, followed a short time later (after the transmitter has been cleared from the synapse) by the release of transmitter from a second vesicle. Compared to the size of the effect that the first vesicle has on the postsynaptic potential, the size of the second vesicle’s effect is _______ because each vesicle contains about the same number of _______ of transmitter.
IDENTICAL; MOLECULES
There are two major mechanisms for clearing neurotransmitter from the synaptic cleft: _______ degradation and neuronal _______. In neuronal _______, special receptors on the _______ membrane called _______ remove molecules of neurotransmitter from the synapse. The _______ removal of neurotransmitter by these mechanisms contributes to the accuracy of neural messages.
ENZYMATIC; REUPTAKE; REUPTAKE; PRESYNAPTIC; TRANSPORTERS; PROMPT
A given neurotransmitter may have _______ an excitatory _______ inhibitory effect, depending on _______. For instance, acetylcholine
1. inhibits the postsynaptic cell by closing K+ and Na+ channels. _______
2. excites the postsynaptic cell by opening Ca2+ channels. _______
3. excites the postsynaptic cell by opening K+ and Na+ channels. _______
4. excites the postsynaptic cell by opening Cl– channels.
_______
5.inhibits the postsynaptic cell by opening Cl– channels.
_______
either; OR; the type of ion channel it activates. false; false; true; false; true
The nicotinic ACh receptor is a(n) _______ -gated ion channel consisting of _______ protein subunits, of which _______ are identical and contain Ach-binding sites; _______ such sites must be bound in order for the channel to open.
ligand; TWO; 2
A drug classified as a(n) _______ mimics the actions of a neurotransmitter; a drug classified as a(n) _______ prevents a neurotransmitter’s action. Nicotine and muscarine function as _______ , whereas curare and bungarotoxin are _______ for receptors of the neurotransmitter_______
agonist; antagonist; agonists; antagonists; acetylcholine
Loewi won the Nobel Prize for demonstrating that _______ transmission is responsible for decreasing a frog’s heart with stimulation of the _______ nerve. The substance Loewi called Vagusstoff was later identified as _______.
chemical; vagus; acetylcholine
