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The influx of Na+ occurs at a membrane potential of +90 mV.
False
K+ channels remain open for 2 msec during the action potential process.
False
The Na+ / K+ pump aids in returning the membrane potential to -70 mV after an action potential.
True
An action potential cannot initiate when Na+ channels are inactivated.
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Action potentials propagate in both directions along the axon.
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Na+ channels at the axon hillock are crucial for the initiation of action potentials.
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The maximum potential reached during an action potential is -90 mV.
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A new action potential can occur immediately after the previous action potential is completed.
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Repeated action potentials (APs) can be generated when the stimulus on a sensory cell remains high, resulting in a persistent graded potential at the axon hillock.
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A graded potential at the axon hillock falls below -70 mV when the stimulus stops, leading to the generation of new action potentials.
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Rapid generation of action potentials is facilitated by the short distances between the sensory sites.
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Action potentials will continue to be generated even after the stimulus on the sensory cell has stopped.
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Sites A and D display consistently high graded potentials when exposed to a sufficient stimulus.
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If action potentials are generated, the distance between the sensory sites is irrelevant.
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When the stimulus is active, the axon hillock potential must remain above -55 mV to initiate action potentials.
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The mechanism of action potential generation relies on active transport rather than diffusion.
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The axon hillock is critical for determining whether a stimulus is strong enough to trigger a new action potential.
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Once a sufficient stimulus is removed, all areas will immediately return to a resting potential of -70 mV.
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Multiple Sclerosis (MS) is characterized by the absence of myelin sheaths, resulting in efficient action potential transmission.
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Nerve diameter has an inverse relationship with conduction rates.
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The nodes of Ranvier are gaps where Na+ and K+ channels cluster, facilitating efficient action potential propagation.
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In sensory synapses, voltage-gated Na+ channels must open before Ca2+ channels to promote neurotransmitter release.
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Endolymph is an extracellular fluid characterized by low concentration of K+ ions.
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Calcispetin enhances synaptic transmission by promoting the release of neurotransmitters.
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The directional propagation of action potentials in neurons is influenced by the presence of myelin sheaths.
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Neurotransmitters always cause the generation of action potentials in the target cells they bind to.
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In synaptic transmission, neurotransmitters diffuse across the synapse and bind directly to voltage-gated Na+ channels.
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An action potential propagates in both directions along the nerve axon due to inconsistent channel activation.
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One EPSP combined with one IPSP results in an action potential and subsequent grip.
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Local anaesthetics like Novocaine and Lidocaine block voltage gated Na+ channels to prevent nerve impulses.
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Tetrodotoxin (TTX) has the same mechanism of action as local anaesthetics.
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The propagation of action potentials in nerve axons occurs in multiple directions simultaneously.
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Inhibition of an inhibitor in neural circuits results in activation and the maintenance of grip.
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Metabotropic responses are mediated by a GPCR.
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Temporal summation involves multiple signals arriving from different locations at the same time.
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Two weak signals that arrive several milliseconds apart can trigger an action potential (AP).
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Excitatory post-synaptic potentials (EPSP) inhibit the generation of action potentials.
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Inhibitory post-synaptic potentials (IPSP) contribute to the activation of the postsynaptic cell.
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Spatial summation occurs when multiple signals arrive simultaneously but from different locations.
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The brain can override inhibitory signals to maintain a grip during reflex actions.
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The convergence of many presynaptic cells onto one postsynaptic cell can simplify neural processing.
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A decision-making process in the brain only considers excitatory signals for synaptic integration.
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Simultaneous arrival of two weak signals will not trigger an action potential due to their low amplitude.
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Study Notes
Nodes of Ranvier
- Myelin sheaths cause sodium and potassium channels to aggregate at discrete regions along the axon.
- The gaps between myelin where sodium and potassium channels cluster are called nodes of Ranvier.
- Their spacing allows efficient propagation of action potentials.
Multiple Sclerosis
- Is an autoimmune disease where myelin is absent.
- Inefficient action potential transmission is a result of myelin absence.
Nerve Diameter & Conduction Rates
- Nerve diameter is directly proportional to conduction rate
Action Potentials in Nerve Cell Axons
- Action potentials propagate in one direction because of the refractory period of the sodium channels.
- This means that sodium channels cannot be immediately reactivated after they have been open, preventing the action potential from traveling backwards.
Local Anaesthetics
- Local anaesthetics block voltage-gated sodium channels, preventing nerve impulses.
- Examples of local anaesthetics include Novocaine and Lidocaine.
Neurotoxins
- Tetrodotoxin (TTX) blocks voltage-gated sodium channels, preventing nerve impulses.
- TTX can be fatal, and effects can be observed in four stages.
Sensory Synapses
- Sensory synapses connect cells that detect changes in the body's internal and external environment to the nervous system.
- In most sensory synapses, the stimulus triggers activation of voltage-gated calcium channels.
- This causes the release of neurotransmitters, which diffuse across the synapse and bind to receptors on the afferent neuron.
- This can generate action potentials that are propagated along the afferent neuron.
Hearing and Vision
- In hearing, activation of voltage-gated calcium channels causes the release of neurotransmitters which diffuse across the synapse and bind receptors on the target cell.
- The extracellular fluid surrounding these cells is called endolymph, which has a high potassium concentration.
- In vision, activation of voltage-gated calcium channels causes the release of neurotransmitters which diffuse across the synapse and bind receptors on the target cell.
Neuronal Synaptic Transmission
- In neuronal synaptic transmission, the arrival of an action potential at the presynaptic terminal triggers the opening of voltage-gated calcium channels.
- The influx of calcium ions causes the release of neurotransmitters.
- These neurotransmitters diffuse across the synaptic cleft and bind to receptors on the postsynaptic membrane.
- This binding can either excite or inhibit the postsynaptic neuron.
Calcispetin
- Calcispetin blocks calcium channels.
- If calcium channels are blocked, there is no neurotransmitter release, and no synaptic transmission.
Synaptic Transmission - Signal Termination
- The signal must be terminated when the action potentials stop.
- The mechanism of signal termination depends on the nature of the channel.
Summation
- Occurs when multiple presynaptic neurons synapse with the cell body of a single postsynaptic neuron.
- Spatial summation refers to the summation of signals from multiple inputs at different locations on the neuron.
- Temporal summation refers to the summation of signals from a single input over time.
Role of Synapses in Neuronal Circuits
- Synapses are crucial for information processing in the nervous system.
- They allow for the integration of signals from multiple neurons.
- Summation plays a key role in decision making within the nervous system.
Local Anaesthetics vs Neurotoxins
- Local anaesthetics block voltage-gated sodium channels, preventing nerve impulses.
- Neurotoxins also block voltage-gated sodium channels, but they can be fatal.
- Local anaesthetics are typically used for pain relief, while neurotoxins are dangerous and should be avoided.
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Description
This quiz explores key concepts in neurobiology, focusing on the structure and function of neurons, the significance of nodes of Ranvier, and the impact of diseases like multiple sclerosis. Additionally, it delves into the role of local anesthetics in nerve impulse transmission and how nerve diameter affects conduction rates.
