Nervous System Physiology

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Questions and Answers

What is the relationship between action potentials and graded potentials?

Every graded potential causes an action potential

Action potentials are initiated when the membrane is depolarised to threshold by a graded potential (correct)

Two terms describing the same event

An action potential is the sum of several graded potentials

Why do voltage regulated K+ channels not need to inactivate?

Because the equilibrium potential for K+ is higher than the threshold of the K+ channels (ca -60 mV)

Because they are always open

Because the equilibrium potential for K+ is lower than the threshold of the K+ channels (ca -60 mV) (correct)

Because they are blocked by Na+ ions

Which feature of voltage-regulated ion channels is responsible for a neurons refractory period?

K+ channel inactivation

Na+ channel inactivation (correct)

Na+ channel threshold

K+ channel activation

What is the correct sequence of events during an action potential?

IV - III - II - I-V Signup and view all the answers

Why can an action potential not be initiated during the refractory period?

Because voltage-gated Na+ channels are inactivated Signup and view all the answers

Why does continuous propagation of the action potential not occur in myelinated axons?

Because the myelin sheath blocks the flow of ions across the membrane Signup and view all the answers

Why do action potentials travel long distances while graded potentials do not?

Because action potentials are actively propagated Signup and view all the answers

What determines the duration of an action potential?

Stimulus duration Signup and view all the answers

Which of the following CANNOT initiate a graded potential?

Action potentials Signup and view all the answers

Pick the correct statement. At a chemical synapse:

Generally communication only occurs in one direction Signup and view all the answers

What terminates transmission at the cholinergic synapse?

Breakdown of acetylcholine (ACh) by acetylcholinesterase (AChE) Signup and view all the answers

Pick the correct statement. Slow postsynaptic receptors:

May trigger more than one response in the postsynaptic cell Signup and view all the answers

What function of neurons is performed by summation?

Integration of several different synaptic inputs Signup and view all the answers

Why do alkalosis and acidosis affect neural impulse conduction?

Because the concentration of H+ affects the potential difference across the cell membrane Signup and view all the answers

Atropine binds to muscarinic acetylcholine receptors and prevents their activation by acetylcholine. This means it acts as an:

Antagonist Signup and view all the answers

Selective serotonin reuptake inhibitors (SSRIs, Prozac) prolong the action of serotonin (5HT) at a synapse by preventing its removal from the synaptic cleft. This means they act as:

Agonists Signup and view all the answers

Parkinson's disease is caused by deficient dopamine pathways in the brain. It is therefore best treated with:

Dopamine agonists Signup and view all the answers

The tendon-stretch reflex can be classified as a:

Monosynaptic reflex Signup and view all the answers

Damage to which area of the brain would be expected to impair control of food intake?

Hypothalamus Signup and view all the answers

Which of the following is part of the 'rest-and-repose' response?

Decrease in heart rate Signup and view all the answers

Study Notes

Nervous System Physiology - Advanced

Action potentials and graded potentials: Action potentials are initiated when graded potentials depolarize the membrane to threshold; they are the sum of several graded potentials. Graded potentials are not propagated over long distances and do not have refractory periods. Action potentials are propagated over long distances and characterized by a refractory period.
Voltage-gated K+ channels and inactivation: Voltage-gated K+ channels do not require inactivation because their equilibrium potential (-60 mV) is higher than the threshold of the channels. In contrast, voltage-gated Na+ channels do require inactivation, which is a critical component of the refractory period of neurons.
Refractory period: The refractory period is a result of Na+ channel inactivation, and contributes to unidirectional action potential propagation.
Action potential sequence: The sequence of events in an action potential is: I - Graded depolarization to threshold, II - Activation of voltage-gated Na+ channels, III - Inactivation of voltage-gated Na+ channels, and IV - Activation of voltage-gated K+ channels. Then, the final step is V - Return to normal permeability.
Refractory period and action potential initiation: Action potentials cannot be initiated during the refractory period, because voltage-gated Na+ channels are inactivated.
Myelinated axons and continuous propagation: Continuous propagation does not occur in myelinated axons, because the myelin sheath insulates the axon, preventing the flow of ions across the membrane. Myelinated axons are faster because of saltatory conduction.
Action potential vs. graded potential distance: Action potentials travel long distances due to propagation through refractory periods, while graded potentials do not propagate as they are not actively propagated and dissipate quickly.
Action potential duration: The duration of an action potential is determined by the stimulus duration (not its strength).
Graded potentials and receptors: Various stimuli (like neurotransmitters or sensory receptors) can initiate graded potentials.
Chemical Synapses: Communication occurs in one direction at a chemical synapse, and it's not always propagated to the next cell. Generally a unidirectional transmission occurs.
Termination of transmission at cholinergic synapses: transmission at cholinergic synapses is terminated by the breakdown of acetylcholine (ACh) by acetylcholinesterase (AChE).
Slow postsynaptic receptors: Slow postsynaptic receptors are not always inhibitory, often have multiple responses & are not limited to the CNS. They are often used for neuromuscular transmission.
Function of summation in neurons: Summation integrates multiple synaptic inputs to determine whether or not an action potential is triggered.
Effects of alkalosis and acidosis on neural impulse conduction: The changes in H+ ions' concentration alter the potential difference across the neuronal membrane, therefore affecting conduction.
Acetylcholine receptors and ligands: Atropine acts as an antagonist by binding to muscarinic receptors preventing the activation by acetylcholine. This prevents the receptor activation.
Selective serotonin reuptake inhibitors (SSRIs): SSRIs act as agonists by prolonging the action of serotonin at synapses.
Parkinson's disease and treatment: Parkinson's disease is treated with dopamine agonists because of deficient dopamine pathways in the brain.
Tendons, reflex, and brain regions: Damage to the hypothalamus could impair food intake regulation.
Rest-and-repose response: Decrease in heart rate, dilation of pupils and secretion of adrenaline are part of the rest-and-repose response.

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Test your knowledge on advanced concepts of nervous system physiology, including action potentials and graded potentials. This quiz covers topics such as voltage-gated channels, refractory periods, and the sequence of action potential events. Perfect for those studying neurobiology or physiology at an advanced level.