Neurophysiology: Action Potential and Repolarization

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Questions and Answers

What primarily causes the repolarization of a neuron after depolarization?

Calcium influx

Increased sodium influx

Potassium efflux (correct)

Chloride efflux

What is the result of potassium channels being slower to respond compared to sodium channels?

Prolonged depolarization

Immediate sodium influx

Hyperpolarization (correct)

Early repolarization

How does the sodium-potassium pump contribute to membrane potential?

It prevents any ion movement across the membrane.

It exchanges sodium for potassium to maintain homeostasis. (correct)

It allows sodium influx while preventing potassium efflux.

It exclusively pumps potassium into the cell.

What happens to the sodium channel after it becomes inactivated during the action potential?

It changes conformation to a closed state and does not respond to a stimulus. (D) Signup and view all the answers

What ion is typically more abundant outside the cell at resting membrane potential?

Sodium (B) Signup and view all the answers

What characteristic of potassium channels contributes to the overshoot of repolarization leading to hyperpolarization?

They are slow to open and close. (C) Signup and view all the answers

What does a hyperpolarized state indicate about the electrical charge of the neuron?

It is more negative than the resting potential. (D) Signup and view all the answers

Which statement correctly describes the difference between sodium and potassium channels during action potential?

Sodium channels open quickly, whereas potassium channels are slower to react. (C) Signup and view all the answers

At a pH of 7.2, what form of an acid-base equilibrium is more predominant?

Unionized form (C) Signup and view all the answers

What happens to the concentration of A minus as the pH approaches 7.4 compared to 7.2?

It increases slightly (A) Signup and view all the answers

What characteristic of the plasma at a pH of 7.4 can be implied regarding H plus ions?

There is a higher concentration of ionized form (D) Signup and view all the answers

In the discussion of acid-base equilibrium, what is the role of the blood-brain barrier mentioned?

It influences the effective concentration of drugs (D) Signup and view all the answers

What implication can be drawn from the statement that pH 7.4 is slightly basic compared to pH 7.2?

There is a shift towards more conjugate base presence (B) Signup and view all the answers

What is a primary reason for preferring shorter-acting alpha blockers over phenoxybenzamine?

They have fewer side effects. (C) Signup and view all the answers

Which type of bond is generally considered the strongest in receptor interactions?

Dipole-dipole interactions (A) Signup and view all the answers

Why is esketamine preferred over the racemic mixture of ketamine?

It is more potent and reduces delirium. (A) Signup and view all the answers

Which factor describes the term 'chirality' in molecules?

Asymmetry in 3D structure. (D) Signup and view all the answers

What is the significance of a racemic mixture in pharmacology?

It can lead to inconsistent drug potency. (D) Signup and view all the answers

What distinguishes phenoxybenzamine as an alpha blocker?

It is an irreversible blocker. (B) Signup and view all the answers

What does the term 'ES' refer to in reference to ketamine?

The preferred isomer for therapeutic use. (B) Signup and view all the answers

Which drug is often associated with significant cardiotoxicity when overdosed?

Arbupivacaine (B) Signup and view all the answers

Which characteristic defines non-competitive drugs in relation to receptor binding?

They provide no antidote for reversal. (A) Signup and view all the answers

In which scenario would prolonged drug binding generally be undesirable?

Acute allergic reactions. (C) Signup and view all the answers

What type of interaction significantly affects drug formulation and manufacturing?

Covalent bonding (C) Signup and view all the answers

What describes the 'S-ketamine' and 'R-ketamine' forms of ketamine?

They have varying side effects. (A) Signup and view all the answers

Which of the following compounds is known to have chirality?

Glucose (D) Signup and view all the answers

Which statement about drug-receptor interactions is accurate?

Lipophilic molecules are generally nonpolar and need assistance to cross membranes. (C) Signup and view all the answers

What type of receptor is described as crossing a membrane seven times?

G protein-coupled receptor (D) Signup and view all the answers

Which type of molecular interaction helps maintain the structure of globular proteins primarily?

Hydrogen bonds (C) Signup and view all the answers

What describes an aceptor in pharmacology?

An alternative binding site that is not a desired receptor. (C) Signup and view all the answers

Which is true about nonpolar tails in a biochemical context?

Nonpolar tails are hydrophobic and prefer to interact with each other. (D) Signup and view all the answers

Which drug is noted for its covalent bonding characteristics in the context of receptor interactions?

Phenoxybenzamine (C) Signup and view all the answers

In drug pharmacology, which type of molecular bond is the least common for receptor interaction?

Covalent bonding (B) Signup and view all the answers

Which factor contributes to a drug's long duration of action regarding receptor binding?

The covalent nature of the drug-receptor interaction. (A) Signup and view all the answers

Which of the following interactions is considered the weakest?

Van der Waals interactions (A) Signup and view all the answers

When discussing drug molecules, what is an essential requirement for pharmacological activity?

The drug should be lipid soluble and non-ionized. (D) Signup and view all the answers

In the context of pharmacology, which force is primarily responsible for the non-specific interactions between molecules?

Hydrophobic interactions (B) Signup and view all the answers

Which statement is correct regarding the influences of drug size on membrane permeability?

Size can impede the ability of hydrophobic molecules to cross membranes. (B) Signup and view all the answers

What physiological condition is associated with catecholamine depletion leading to fatigue in heart failure patients?

Excessive sympathetic nervous system stimulation (B) Signup and view all the answers

What kind of interaction can typically disrupt hydrogen bonds during receptor binding?

Temperature changes (C) Signup and view all the answers

Which molecular property is crucial for a drug to bind effectively to its receptor?

Specific conformational shape (D) Signup and view all the answers

In the context of aging, what role do catecholamines play when referring to chronic illness or acute disease?

They may be continuously released as a compensatory mechanism. (A) Signup and view all the answers

What is the goal of post-titanic facilitation in monitoring neuromuscular blockade?

To enhance neurotransmitter release and compete with blockers (D) Signup and view all the answers

What can cause decreased excitability of neurons aside from fatigue and neurotransmitter depletion?

Hypoxia (C) Signup and view all the answers

Which factor is NOT typically involved in determining a receptor's sensitivity?

Rate of neurotransmitter degradation (B) Signup and view all the answers

What component of the phospholipid bilayer is primarily responsible for the membrane's selective permeability?

Proteins embedded in the membrane (B) Signup and view all the answers

What determines the specificity of a receptor's response?

Tissue type where the receptor is located (D) Signup and view all the answers

In the context of receptor pharmacology, which statement is true regarding selectivity?

Selectivity is based on the molecular fit into the receptor. (A) Signup and view all the answers

What effect does ligand binding typically have on a receptor?

It alters the receptor's conformation. (B) Signup and view all the answers

Which of the following ions generally causes depolarizing effects when entering the cell?

Calcium (A) Signup and view all the answers

What happens to receptors when there is a significant increase in neurotransmitter concentration due to post-titanic facilitation?

They may activate additional receptors outside the synapse. (B) Signup and view all the answers

Which neurotransmitter is recognized as the primary excitatory neurotransmitter in the central nervous system?

Glutamate (B) Signup and view all the answers

Which statement accurately describes the structure of the phospholipid bilayer?

It contains both polar heads and nonpolar tails. (A) Signup and view all the answers

What is the primary effect of hypocalcemia on sodium channels during action potentials?

It prevents sodium channels from closing. (D) Signup and view all the answers

What is the general result of activating G protein-coupled receptors?

Conversion of guanosine diphosphate to guanosine triphosphate. (A) Signup and view all the answers

How does hypercalcemia affect cell membrane permeability to sodium?

Decreases permeability, reducing sodium influx. (A) Signup and view all the answers

What physiological effect may an alkalosis condition have on neuronal excitability?

It increases neuronal excitability. (C) Signup and view all the answers

What is the consequence of hypokalemia on the resting membrane potential?

It hyperpolarizes the neuron, making it more negative. (C) Signup and view all the answers

What role do additional receptors outside the synapse play after neurotransmitter flooding?

They can enhance the postsynaptic response. (B) Signup and view all the answers

Which of the following receptors is predominantly inhibitory?

GABA receptors (C) Signup and view all the answers

Which mechanism allows neurotransmitters to be released into the synaptic cleft?

Vesicle fusion with the presynaptic membrane triggered by calcium binding. (C) Signup and view all the answers

Which of the following scenarios may impair the ability of neurons to respond effectively?

Low levels of oxygen supply (A) Signup and view all the answers

What physiological response can occur as a result of receptor activation?

Increased cellular metabolism. (C) Signup and view all the answers

Which type of ion channels respond to changes in the membrane potential?

Voltage-gated ion channels (C) Signup and view all the answers

Which condition may contribute to long-term neurotransmitter depletion in chronic illnesses?

Continuous sympathetic activation (C) Signup and view all the answers

What role do reuptake pumps serve at the presynaptic membrane?

They transport neurotransmitters back into the presynaptic cell. (A) Signup and view all the answers

What occurs during synaptic modulation?

A change in synaptic function or communication. (D) Signup and view all the answers

What role does acetylcholine play in the nervous system?

It mediates excitatory signals through nicotinic receptors. (B) Signup and view all the answers

What is a common mechanism by which ligands promote intracellular signaling?

Causing a conformational change in the receptor. (D) Signup and view all the answers

What is the purpose of the slight delay in neuron communication across the synapse?

To reduce fatigue and constant triggering of the postsynaptic cell. (D) Signup and view all the answers

Which channel type is affected predominantly by local anesthetics?

Voltage-gated sodium channels (A) Signup and view all the answers

What impact does downregulation of receptors have on a neuron?

It decreases receptor sensitivity to neurotransmitter binding. (C) Signup and view all the answers

Which of the following best describes the role of the postsynaptic density?

To maintain homeostasis and integrity in the synaptic environment. (A) Signup and view all the answers

Which is NOT a mechanism through which activated receptors can mediate effects in cells?

Immediate apoptosis of all target cells. (B) Signup and view all the answers

What is primarily responsible for generating an action potential in the postsynaptic cell?

Binding of neurotransmitters to their receptors. (C) Signup and view all the answers

Which of the following effects is most closely associated with excitatory neurotransmitters?

Depolarization of the postsynaptic membrane. (A) Signup and view all the answers

How do ligand-gated ion channels typically operate upon ligand binding?

They cause ions to flow according to concentration gradients. (B) Signup and view all the answers

What happens to a neuron if sodium channels are blocked?

It becomes harder to initiate an action potential. (A) Signup and view all the answers

Which is a common terminal effect of receptor signaling in cells?

Altered enzyme function. (A) Signup and view all the answers

What typically occurs during excessive stimulation of a postsynaptic cell?

Reduction in the postsynaptic cell's responsiveness. (C) Signup and view all the answers

What initial change occurs when an action potential reaches the presynaptic membrane?

Calcium channels open to facilitate neurotransmitter release. (D) Signup and view all the answers

Why is it difficult to generate an action potential during hypokalemia?

Hyperpolarization makes it harder to reach action potential threshold. (B) Signup and view all the answers

What is receptor upregulation primarily a response to?

Decreased activity below baseline (D) Signup and view all the answers

What is the goal of down regulation in cellular responses?

To decrease receptor sensitivity and cellular response (A) Signup and view all the answers

What type of drug is propofol considered?

A GABA agonist (A) Signup and view all the answers

In a graded dose response curve, what typically happens at the plateau phase?

The highest achievable response at a certain dose is reached (B) Signup and view all the answers

Why is individualization of drug therapy important in clinical practice?

Clinical trials only focus on young, healthy individuals (D) Signup and view all the answers

What does receptor upregulation typically NOT involve?

Decreased number of receptors (B) Signup and view all the answers

When does a cell undergo down regulation?

When it experiences excessive stimulation (B) Signup and view all the answers

What effect does metallas metallism have on furosemide?

It potentiates the diuretic effect. (B) Signup and view all the answers

Which mechanism primarily describes the relationship between drug potency and receptor affinity?

Direct relationship. (C) Signup and view all the answers

What aspect does titration in pharmacology primarily address?

Adjusting drug dosage based on patient-specific responses (D) Signup and view all the answers

On which axis is drug potency depicted on a dose response curve?

X-axis. (A) Signup and view all the answers

Which axis typically represents drug dose in a dose response curve?

X-axis (A) Signup and view all the answers

What effect does constant antagonism have on receptor numbers?

It decreases receptor numbers and sensitivity (C) Signup and view all the answers

What does a leftward shift in a dose response curve indicate?

Decreased drug concentration needed for effect. (D) Signup and view all the answers

What does a steep slope on a dose-response curve typically indicate regarding receptor binding?

A large proportion of receptors need to be bound for clinical effect. (A) Signup and view all the answers

In a quantal dose-response curve, what is the primary focus of the plotted data?

Identifying whether a specific drug concentration has an effect. (C) Signup and view all the answers

Which of the following is NOT a superpower mentioned as a preference?

Invisibility (A) Signup and view all the answers

What happens to the dose response curve when a competitive antagonist is introduced?

Shifts right and maintains plateau. (B) Signup and view all the answers

What term describes the effective dose that yields the desired response in 50% of a population?

ED50 (D) Signup and view all the answers

What is the primary definition of efficacy in pharmacology?

The ability to produce a desired clinical effect. (C) Signup and view all the answers

What happens when a drug reaches a therapeutic plateau in a dose response curve?

The response plateaus and remains constant (A) Signup and view all the answers

What type of information would you be least likely to find in drug trials?

Responses in diverse age groups (C) Signup and view all the answers

Which of the following best describes the therapeutic index?

The ratio of LD50 to ED50. (A) Signup and view all the answers

What does the slope of a dose response curve represent?

Number of receptors occupied. (D) Signup and view all the answers

When discussing dose response curves, what does the log scale often represent?

Logarithmic increase in drug concentration (B) Signup and view all the answers

What does partial efficacy mean in the context of drug response?

The drug achieves a response less than the maximum effect. (B) Signup and view all the answers

How does a non-competitive antagonist alter a dose response curve?

Shifts down and right. (D) Signup and view all the answers

What is identified by the therapeutic index?

LD50 to ED50 ratio. (C) Signup and view all the answers

How is potency best defined in pharmacology?

The dose needed to elicit a specified response. (D) Signup and view all the answers

How does receptor upregulation primarily affect a cell's response?

It allows for enhanced sensitivity to stimuli (B) Signup and view all the answers

What describes tachyphylaxis in pharmacology?

Decreased response to a drug over time. (A) Signup and view all the answers

Which statement regarding agonists is true?

Agonists typically engage in weaker bonding interactions with receptors. (A) Signup and view all the answers

Which statement is true regarding a racemic mixture?

It consists of two enantiomers in equal amounts. (B) Signup and view all the answers

What is indicated by an inverse agonist on a dose-response curve?

Produces a response below the baseline of receptor activity. (B) Signup and view all the answers

Why is the ED50 significant in drug studies?

It serves as a benchmark for establishing a drug's safety margin. (A) Signup and view all the answers

What is indicated by a decreased slope on the dose response curve?

Less drug efficacy. (C) Signup and view all the answers

What is the primary focus of pharmacogenetics?

To explore variations in drug response due to genetics. (B) Signup and view all the answers

In the context of anesthetics, what does the expression 'spectrum from awake to totally unconscious' refer to?

The range of clinical effects based on receptor occupancy. (A) Signup and view all the answers

Which factor influences the shape of a dose-response curve significantly?

The binding strength of the drug to its receptor. (C) Signup and view all the answers

What should researchers primarily study to assess potential toxic side effects of a drug?

The relationship between therapeutic and lethal doses. (B) Signup and view all the answers

Why might researchers prefer to use LD50 over TD50 in calculating the therapeutic index?

LD50 is generally easier to determine in animal studies. (B) Signup and view all the answers

What is a common feature of receptor pharmacology that underlies the application of agonists?

Agonists can cause receptor desensitization. (D) Signup and view all the answers

What is the primary effect of a full agonist on a receptor?

It activates the receptor to produce maximal response. (C) Signup and view all the answers

What is the result of continuous administration of a full agonist?

Downregulation of receptors. (C) Signup and view all the answers

What characterizes a partial agonist compared to a full agonist?

It has a ceiling effect and cannot achieve maximal response. (D) Signup and view all the answers

What issue may arise if a patient on buprenorphine undergoes surgery without stopping the medication?

Inadequate pain control due to receptor saturation with partial agonist. (D) Signup and view all the answers

How do antagonists typically interact with receptors?

They block agonists from activating the receptor. (B) Signup and view all the answers

What happens when a non-competitive antagonist is introduced in the presence of an agonist?

The agonist's efficacy is permanently reduced regardless of dose. (D) Signup and view all the answers

What is the primary distinction between competitive and non-competitive antagonism?

Competitive antagonists can be displaced by increasing the amount of agonist. (D) Signup and view all the answers

In a dose-response curve, what effect does introducing a competitive antagonist have?

It maintains the agonist's maximal efficacy but decreases potency. (B) Signup and view all the answers

Why might a partial agonist not be appropriate for pain management in opioid-dependent patients?

They can precipitate withdrawal symptoms and inadequate pain control. (B) Signup and view all the answers

What role do catecholamines play in the body related to agonism?

They are full agonists that stimulate sympathetic nervous responses. (D) Signup and view all the answers

What best describes a scenario of a patient experiencing a femur fracture while on buprenorphine?

They may require significantly more agonist to overcome the partial agonist. (B) Signup and view all the answers

What can occur as a result of receptor downregulation after continuous administration of an agonist?

Decreased responsiveness to subsequent agonist doses. (D) Signup and view all the answers

What is the effect of a mixed agonist-antagonist on receptor activation?

It activates and blocks different receptor subtypes. (C) Signup and view all the answers

What defines the 'ceiling effect' of a partial agonist?

It cannot achieve the highest levels of receptor activation. (A) Signup and view all the answers

What factors determine the time limit for the exam?

The number of questions provided (C) Signup and view all the answers

In terms of expectation management, what advice was humorously suggested for students?

Release the need to control (B) Signup and view all the answers

When will students typically find out their exam grades?

On the same day before a meeting (A) Signup and view all the answers

What is the correct physiological pH referenced in the discussion concerning weak acids?

7.4 (A) Signup and view all the answers

What pharmacokinetic factor could significantly influence a patient's drug response aside from age and weight?

Genetic markers (A) Signup and view all the answers

Which side of the blood-brain barrier is expected to have a greater fraction of ion trapping for a weak acid with a pKa of 9?

The plasma side (A) Signup and view all the answers

What did the instructor emphasize about the use of study materials for the exam?

PowerPoint slides are the primary resource (C) Signup and view all the answers

Which population is more likely to be classified as ultra-rapid metabolizers of certain medications?

Ethiopian populations (D) Signup and view all the answers

What will the instructor provide concerning the exam format before the exam date?

A brief announcement (B) Signup and view all the answers

What is a single nucleotide polymorphism (SNP)?

A variation in DNA sequence (D) Signup and view all the answers

What is likely to happen if a question from the practice examples is found confusing?

Ask the instructor for clarification (D) Signup and view all the answers

How do hormonal differences between sexes potentially affect drug response?

By modifying liver enzyme activity (B) Signup and view all the answers

What could indicate that a patient is not responding to a medication as expected?

Exaggerated or toxic response (C) Signup and view all the answers

For a weak acid, which parameter is essential for determining if it is ionized or non-ionized in solution?

pKa value (D) Signup and view all the answers

What potential issue arises if a student focuses only on lecture content and neglects other materials?

They might miss important topics covered in the book (D) Signup and view all the answers

Why might a patient require higher anesthesia doses based on genetic factors?

Presence of red hair genetics (B) Signup and view all the answers

Which drugs are commonly studied for genetically based treatment algorithms?

Beta blockers and ACE inhibitors (B) Signup and view all the answers

What is the expected range of questions students can anticipate in the upcoming exam?

40 to 50 questions (A) Signup and view all the answers

Why might students not receive preliminary results immediately after the exam?

The instructor needs to analyze results first (D) Signup and view all the answers

What can lead to differences in how quickly patients emerge from anesthesia?

Body composition and hormonal influences (A) Signup and view all the answers

How does population-based variability influence pharmacologic dosing?

It requires dose adjustments for non-typical patient groups. (B) Signup and view all the answers

What humorous method did the instructor suggest they could use to motivate students?

Make bumper stickers (B) Signup and view all the answers

In the context of pharmacogenomics, what do variances in CYP450 isoenzymes typically affect?

Drug metabolism rates (B) Signup and view all the answers

In ion trapping, which solution would potentially hold more of a weak acid's non-ionized form?

An acidic solution (B) Signup and view all the answers

Which factor does NOT contribute to pharmacologic response variability among individuals?

Food preferences (B) Signup and view all the answers

What percentage of Caucasians might be classified as poor metabolizers for certain drugs metabolized by CYP2D6?

7% to 10% (A) Signup and view all the answers

Which term refers to the scientific study of how genetic differences affect individual responses to drugs?

Pharmacogenomics (B) Signup and view all the answers

What might clinicians do if they observe a patient requiring unusually high doses of opioids post-operatively?

Consider a potential genetic variation (D) Signup and view all the answers

What effect do positive allosteric modulators have on GABA receptors?

They increase the effect of GABA. (D) Signup and view all the answers

How does the interaction between anesthetic gases illustrate additive effects?

The combination allows for a full dose with reduced individual dosages. (D) Signup and view all the answers

Which of the following interactions is an example of a synergistic effect?

Propofol and fentanyl used together. (A) Signup and view all the answers

What is the primary characteristic of tachyphylaxis in drug administration?

Decreased response to a drug after repeated administration. (A) Signup and view all the answers

What is an example of potentiation in pharmacological terms?

One drug enhancing the effect of another without changing its mechanism. (B) Signup and view all the answers

Which of the following best describes antagonistic effects in drug interactions?

One drug inhibits the effect of another drug. (A) Signup and view all the answers

In the context of anesthesia, why is it important to monitor the use of propofol and fentanyl together?

To avoid excessive sedation and loss of airway control. (A) Signup and view all the answers

What should be considered if phenylephrine's effectiveness appears to diminish at high doses?

The patient likely is in tachyphylaxis. (C) Signup and view all the answers

What is the primary mechanism by which tachyphylaxis may occur?

Decreased receptor sensitivity due to overstimulation. (A) Signup and view all the answers

What is the risk of using high doses of multiple vasopressors like phenylephrine?

It may obscure the contributions of each drug's effects. (C) Signup and view all the answers

What can be suggested if a patient on phenylephrine is not responding at high doses?

Switch to a different vasopressor for better effectiveness. (D) Signup and view all the answers

Which situation summarizes a misunderstanding related to how GABA agonists and benzodiazepines interact?

They enhance their individual effects without being potentiating. (B) Signup and view all the answers

How do drugs combined for antiretroviral therapy function typically?

They work by a mechanism of potentiation. (B) Signup and view all the answers

Why is understanding the concept of synergistic effects crucial for anesthetists?

It can lead to unintentional respiratory compromise during procedures. (A) Signup and view all the answers

How does a competitive antagonist affect catecholamine potency on alpha and beta receptors?

It requires a higher concentration of catecholamines to achieve a clinical response. (B) Signup and view all the answers

What happens to receptors when there is continuous blockade by antagonists?

There will be downregulation of the target receptor. (A) Signup and view all the answers

What characterizes inverse agonists compared to traditional antagonists?

They decrease or stop the activity of a receptor that has intrinsic activity. (D) Signup and view all the answers

Which action is NOT characteristic of antagonists?

They activate receptors. (D) Signup and view all the answers

In a competitive antagonism scenario, what is required to achieve a therapeutic effect when a patient is on metoprolol?

Increased levels of catecholamines to compete for receptor binding. (C) Signup and view all the answers

How do allosteric modulators function compared to traditional agonists?

They bind to a different site than the ligand and modify receptor activity. (A) Signup and view all the answers

What is the consequence of using an opioid antagonist like Narcan in a patient with significant opioid exposure?

Multiple doses may be necessary due to the longer duration of action of the agonists. (D) Signup and view all the answers

Which statement is true regarding beta blockers like metoprolol?

They occupy beta receptors, affecting the response to other catecholamines. (D) Signup and view all the answers

What is an effect of using neostigmine in the context of neuromuscular junction antagonism?

It prevents the breakdown of acetylcholine to increase agonist concentration. (B) Signup and view all the answers

In what situation might antagonists and agonists coexist at a receptor site?

When the antagonist has a longer duration of action than the agonist. (B) Signup and view all the answers

What role do inverse agonists play in receptor pharmacology?

They reduce the baseline activity of a receptor that is already active. (D) Signup and view all the answers

What differentiates an agonist from an inverse agonist regarding their effects on cyclic AMP?

Agonists increase cyclic AMP, while inverse agonists decrease it. (D) Signup and view all the answers

Why is it challenging to achieve a clinical effect with high opioid concentrations?

The effects of agonists are significantly prolonged at higher concentrations. (C) Signup and view all the answers

What is a potential outcome of prolonged antagonist use on receptor systems?

Upregulation of the receptor in response to constant blockade. (C) Signup and view all the answers

What effect does progesterone have on the sensitivity to general anesthetics during pregnancy?

Increases sensitivity leading to a lower anesthetic requirement. (A) Signup and view all the answers

Why might pregnant patients at risk for emergent procedures require less general anesthetic?

To minimize fetal effects and postpartum hemorrhage risk. (D) Signup and view all the answers

What is one reason that neonates may struggle with drug elimination compared to older children?

Immaturity of both renal and metabolic systems. (B) Signup and view all the answers

What are the characteristics of drugs that do not undergo metabolism?

They can be either charged or uncharged depending on the drug. (C) Signup and view all the answers

How does the volume of distribution for propofol compare to that of rocuronium?

Propofol has a higher volume of distribution than rocuronium. (B) Signup and view all the answers

What is the primary reason for keeping anesthetic levels low in pregnant patients under general anesthesia?

To avoid adverse effects on the fetus and manage hemodynamic stability. (D) Signup and view all the answers

What might increase the risk of awareness during general anesthesia in a pregnant patient?

Lower anesthetic doses caused by the effects of progesterone. (A) Signup and view all the answers

In neonates, what characteristic of renal function affects drug excretion?

Underdeveloped renal structures leading to inefficient drug elimination. (D) Signup and view all the answers

Why would it be important to consider drug ionization in neonates?

Ionization affects the solubility and elimination of drugs. (B) Signup and view all the answers

What is the relationship between drug solubility and its elimination by renal systems?

Water-soluble, especially ionized drugs, are typically eliminated more efficiently. (B) Signup and view all the answers

How does the effect site concentration relate to the volume of distribution of a drug?

Higher volume of distribution means lower effect site concentration. (D) Signup and view all the answers

How might the immaturity of neonatal renal systems specifically impact drug management?

Drug dosing must be adjusted for slower elimination rates. (B) Signup and view all the answers

What conclusion can be drawn regarding drug metabolism in neonates compared to adults?

Neonates rely more heavily on renal excretion than metabolic processing. (A) Signup and view all the answers

Study Notes

Repolarization and Action Potentials

Cations are lost, specifically potassium, causing the cell to repolarize (return to a negative membrane potential).
Potassium channels are slower than sodium channels. Sodium channels open rapidly, flooding the cell with sodium, then inactivate. Potassium channels take longer to both open and close.
Potassium efflux can lead to hyperpolarization—the cell becomes more negative than its resting potential.
The sodium-potassium pump restores the resting membrane potential by pumping sodium out and potassium in.
Sodium channels transition from inactivated to closed state, preparing for the next stimulus

Electrolyte Abnormalities and Neuronal Responsiveness

Hypocalcemia: Prevents sodium channels from closing between action potentials, causing repetitive firing (tetany).
Hypercalcemia: Decreases cell membrane permeability to sodium, hindering neuronal excitation..
Hypokalemia: Leads to a more negative resting membrane potential, decreasing neuronal excitability due to hyperpolarization.
Sodium channel blockade: Prevents reaching threshold potential, inhibiting action potential generation.

Synaptic Transmission

Presynaptic cells release neurotransmitters into the synaptic cleft via vesicles.
Calcium influx triggers the fusion of vesicles with the cell membrane.
Reuptake pumps bring neurotransmitters back into the presynaptic cell for reuse or breakdown.
Acetylcholine is an example of a neurotransmitter that's broken down and reabsorbed.

Postsynaptic Density and Synaptic Modulation

Postsynaptic density maintains homeostasis and integrity in the postsynaptic region.
Synaptic modulation refers to changes in synaptic function, including signaling, depolarization, and responses.
Synaptic delay is a slight delay between neural communication, beneficial in reducing fatigue and constant triggering of the postsynaptic cell.
Tachyphylaxis can also occur with repetitive stimulation or depletion of neurotransmitters.

Receptor Pharmacology

Receptors are proteins that bind endogenous chemicals or drugs.
Receptor properties include:
- Sensitivity: Concentration needed for cellular response.
- Selectivity: Ability of a molecule to fit into the receptor opening.
- Specificity: Cellular response dependent on tissue type.
Receptor binding often involves hydrophobic bonding, for lipid-soluble drugs
Acceptors are alternative drug binding sites.
Different receptor types exist (G protein-coupled, ligand-gated ion channels, voltage-gated ion channels, kinase-linked, and nuclear receptors).

Receptor Activation and Cellular Responses

Ligand binding causes a conformational change in the receptor.
Receptors transduce signals, amplifying or integrating biochemically pathways, causing changes in gene expression, cellular metabolism, and even apoptosis.
Ion channels (sodium, calcium, chloride, potassium) play a critical role; cations (sodium & calcium) are excitatory, anions (chloride) are inhibitory.
Different conformations can affect their pharmacologic effects.

Receptor Upregulation and Downregulation

Upregulation: Increases receptor number and sensitivity in response to insufficient agonist stimulation or consistent antagonist blockade.
Downregulation: Decreases receptor number and sensitivity in response to excessive agonist stimulation.

Receptor Types (Agonists, Partial Agonists, Antagonists, Inverse Agonists)

Agonists: Activate the receptor. Examples include catecholamines, propofol, and fentanyl. Continuous administration may cause downregulation.
Partial agonists: Limited receptor activation, cannot reach maximal response. Examples include buprenorphine.
Antagonists: Block receptor activation and prevent agonist binding. Examples include beta-blockers (esmolol, metoprolol) and competitive antagonists like Narcan.
Inverse agonists: Decrease receptor activity. Examples include certain beta blockers (like carvedilol and propranolol).

Allosteric Modulators

Allosteric modulators bind to a different site on a receptor than the agonist, modifying the agonist's effect.
Benzodiazepines are an example of positive allosteric modulators of GABA receptors.

Drug Interactions and Variability

Additive effects: Summation of drug effects.
Antagonistic effects: One drug blocks the response of another.
Synergistic effects: Combined effect is greater than the sum of individual effects (common with anesthetics and opioids).
Potentiation: One drug enhances the effect of another. Examples include antiretroviral therapies.
Tachyphylaxis: Decreased efficacy after repeated drug administration.
Pharmacogenetics/pharmacogenomics: Study of genetic variations in drug response; metabolism, absorption, distribution, and excretion can all be affected. Polymorphisms, particularly SNPs, play an important role.

Population-based Variability and Pharmacokinetics/Pharmacodynamics

Consideration of age, sex, weight, body surface area, and other factors in drug administration for optimal response.
Clinical responses vary greatly in diverse populations due to genetic variations. CYP enzymes, like CYP2D6, affect drug metabolism and responses.

Clinical Example of Receptor Interactions

Competitive antagonism: Beta-blocker (esmolol) may require higher doses of catecholamines (epinephrine) to overcome the blockade and stimulate the heart.
Noncompetitive antagonism (not common clinically): A scenario where the patient is receiving an irreversible competitive antagonist, for example, Succinylcholine, which is being blocked by an irreversible competitive antagonist, Rocuronium, which is hard to overcome the blockade and may require Neostigmine to reverse the block.

Stereochemistry and Chirality

Stereochemistry: Describes the 3D molecular structure of molecules like drugs and endogenous substances.
Chirality: Molecules with 3D asymmetry (e.g., enantiomers).
Racemic mixtures: 50/50 mix of enantiomers. Example: Ketamine.
Certain enantiomers (e.g., S-ketamine) may be more potent or produce fewer side effects than others (e.g., R-ketamine).

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This quiz explores the mechanisms behind neuron repolarization, including the roles of sodium and potassium channels during action potentials. Test your knowledge on ion distribution, membrane potential, and the characteristics that influence neuronal excitability. Perfect for students studying neurophysiology!