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YR1 - Pharmacology SEM 1 > 2. Mechanism of Drug Action > Flashcards

2. Mechanism of Drug Action Flashcards

1
Q

The ability of a drug to form a drug- receptor complex is called

  1. Efficacy
  2. Intrinsic activity
  3. Potency
  4. Affinity
  5. Specificity
A

The ability of a drug to form a drug- receptor complex is called

  1. Efficacy
  2. Intrinsic activity
  3. Potency
  4. Affinity
  5. Specificity
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2
Q

An agonist is a drug which

  1. Has both affinity and intrinsic activity (efficacy)
  2. Must combine with 100% of receptors to produce a response
  3. Can combine with many different types of receptors
  4. Generally binds irreversibly with a receptor
  5. Has affinity but no intrinsic activity (efficacy)
A

An agonist is a drug which

  1. Has both affinity and intrinsic activity (efficacy)
  2. Must combine with 100% of receptors to produce a response
  3. Can combine with many different types of receptors
  4. Generally binds irreversibly with a receptor
  5. Has affinity but no intrinsic activity (efficacy)
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3
Q

Pharmacodynamics refers to

  1. What the body does to a drug
  2. The formation of a drug-receptor complex
  3. The maximum response a drug can produce
  4. What a drug does to the body
  5. The potency of a drug
A

Pharmacodynamics refers to

  1. What the body does to a drug
  2. The formation of a drug-receptor complex
  3. The maximum response a drug can produce
  4. What a drug does to the body
  5. The potency of a drug
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4
Q

The effect of a competitive antagonist on the log-dose response curve of an agonist is to

  1. Shift the curve to the left without affecting the maximum response
  2. Shift the curve to the right without affecting the maximum response
  3. Shift the curve to the left and reduce the maximum response
  4. Shift the curve to the right and reduce the maximum response
  5. A competitive antagonist has no effect on the log-dose response curve of an agonist
A

The effect of a competitive antagonist on the log-dose response curve of an agonist is to

  1. Shift the curve to the left without affecting the maximum response
  2. Shift the curve to the right without affecting the maximum response
  3. Shift the curve to the left and reduce the maximum response
  4. Shift the curve to the right and reduce the maximum response
  5. A competitive antagonist has no effect on the log-dose response curve of an agonist
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5
Q

Which of the following drugs is a competitive antagonist

  1. Morphine
  2. Salbutamol
  3. Naloxone
  4. Acetylcholine
  5. Histamine
A

Which of the following drugs is a competitive antagonist

  1. Morphine = μ-opioid receptor agonist
  2. Salbutamol = B2 receptor agonist
  3. Naloxone = opioid receptor antagonist
  4. Acetylcholine = Ach receptor agonists
  5. Histamine = histamine receptor agonists
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6
Q

Drugs achieve their therapeutic effects by acting primarily on what 4 things?

A

Drugs achieve their therapeutic effects by acting primarily on either:

  1. Receptors
  2. Enzymes
  3. Ion channels
  4. Carrier molecules
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7
Q

What are 4 Types of Drug Receptors?

A

Types of Drug Receptors

  1. Ligand gated ion channel receptors
  2. G-protein coupled receptors (GPCRs)
  3. Kinase linked receptors
  4. Nuclear receptors
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8
Q

How quickly do Ligand Gated Ion Channel Receptors produce a response?

A

Ligand gated ion channel receptors

  1. Stimulation of receptor
  2. Opening of ion channel
  3. Rapid response (msec)
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9
Q

What is an example of a Ligand gated ion channel receptor?

A

Ligand gated ion channel receptor - Example

Acetylcholine nicotinic receptors on skeletal muscle causing contraction

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10
Q

What is the structure of an Acetylcholine Nicotinic Receptor?

A

Acetylcholine Nicotinic Receptor

  • Pentameric assembly of subunits
  • There are four subunits - α, β, γ and δ
  • There are two acetylcholine binding sites - acetylcholine must bind to both to activate the receptor
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11
Q

What is another example of a Ligand Gated Ion Channel Receptors?

Which drugs work on this receptor?

A

Ligand Gated Ion Channel Receptors - Example

= Gamma amino butyric acid GABAA receptors (CNS inhibition)

  • GABAA receptor channel is selectively permeable to Cl ions
  • Increasing the permeability and concentration of Cl- ions in the cell hyperpolarises the cell and reduces excitability
  • BZ = Benzodiazepines → work on these receptors but at a different place
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12
Q

What is the structure of a G-Protein Coupled Receptor (GPCR)?

How are they identified?

A

G-Protein Coupled Receptors (GPCR)

  • G-protein coupled receptors consist of a single polypeptide chain with seven transmembrane segments
  • When the receptor is stimulated signals are transmitted to, and activate an attached G-protein (guanine nucleotide-binding protein)
  • G-proteins are composed of alpha (α), beta (β) and gamma (γ) subunits
  • G-proteins are identified by their G alpha subunits and are grouped into four families: Gs, Gi, Go, and Gq
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13
Q

What binds to the G-protein alpha subunit of a GPCR?

What happens next?

A

G-Protein Coupled Receptors (GPCR)

  • G-protein alpha subunits bind either guanosine diphosphate (GDP) or guanosine triphosphate (GTP) depending on whether the G-protein is inactive (GDP) or active (GTP)
  • When the receptor is stimulated GDP on the G-protein is replaced by GTP and the G-protein is activated
  • When activated the alpha subunit splits from the beta and gamma subunits and moves from the receptor
  • The alpha subunit, and the beta and gamma subunits, can then act on enzymes within the cell and cause the formation of a “second messenger” e.g. adenylyl cyclase and the formation of cyclic adenosine monophosphate (cAMP), or can have an action on ion channels in the cell membrane
  • This results in a response being produced
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14
Q

Which receptors are the largest in the body?

What is their response time?

A

G-Protein Coupled Receptors (GPCR)

  • G-protein coupled receptors are the largest and most diverse membrane receptors in the body
  • It is estimated that around 50% of all drugs used today act on G-protein coupled receptors
  • Response time is in seconds (slower than ligand gated)
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15
Q

What are 5 examples of GPCR agonists?

A

GPCR Agonists

  1. adrenaline and beta1 receptors (tachycardia), beta2 receptors (bronchodilation) and alpha receptors (vasoconstriction)
  2. acetylcholine and muscarinic M2 receptors (bradycardia)
  3. histamine and H1 receptors (bronchoconstriction)
  4. angiotensin II and angiotensin II type1 receptors (vasoconstriction)
  5. opioids e.g. morphine and mu receptors (analgesia)
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16
Q

What happens when beta1 adrenergic GPCRs are stimulated?

A

GPCRs - beta1 adrenergic receptors

  • Stimulation of beta1 adrenergic G-protein coupled receptors in the heart increases heart rate (tachycardia)
  • receptor stimulation, activation of G protein (Gs), stimulation of adenyl cyclase, increase in cAMP formation, activation of protein kinase and tachycardia
17
Q

What happens when M2 muscarinic GPCRs are stimulated?

A

GPCRs - M2 muscarinic receptors

  • Stimulation of M2 muscarinic G-protein coupled receptors in the heart decreases heart rate (bradycardia)
  • receptor stimulation, activation of G protein (Gi), inhibition of adenyl cyclase, decrease in cAMP formation, reduced activation of protein kinase and bradycardia
18
Q

What are 3 examples of competitive antagonists of GPCRs?

A

G-Protein Coupled Receptors (GPCR) - Examples of competitive antagonists include

  1. beta blockers (eg. propranolol) → inhibit beta adrenergic receptors
  2. angiotensin II receptor antagonists (eg. irbesartan) → inhibit angiotensin II type1 receptors
  3. narcotic antagonists (eg. naloxone) → inhibit opioid mu receptors
19
Q

Where are Kinase linked receptors located?

What do they involve?

What are they activated by?

Response time?

A

Kinase linked receptors

  • Located on the cell membrane
  • Involve intracellular enzymes - e.g. protein kinase and gene transcription
  • Activated by a number of agents including growth factor, cytokines and insulin
  • Response in minutes to hours = slow
20
Q

Where are Nuclear receptors located?

What do they involve?

What are they activated by?

Response time?

A

Nuclear Receptors

  • Intracellular receptors within nucleus
  • Involve gene transcription and DNA
  • Activated by a number of agents including oestrogen, glucocorticoids, thyroid hormone and vitamin D
  • Response in hours = slower
21
Q

Give examples of a drug that works by inhibiting enzymes?

A

Mechanism of Action - Inhibiting Enzymes

  • Nonsteroidal anti-inflammatory drugs (NSAIDS) such as diclofenac, ibuprofen and naproxen inhibit the enzyme cyclooxygenase and block the production of prostaglandins
22
Q

Which prostaglandins are inhibited by NSAIDs?

A

NSAIDs

  • Naproxen
  • Diclofenac
  • Ibuprofen
23
Q

What is another example of a group of drugs that work by inhibiting enzymes?

A

ACE Inhibitors

Angiotensin converting enzyme (ACE) inhibitors such as perindopril and ramipril inhibit angiotensin converting enzyme and block the conversion of angiotensin I (1) to angiotensin II (2)

All ACE inhibitors end in -pril

24
Q

What are Angiotensin II type 1 receptor antagonists and how do they work?

Examples?

A

Angiotensin II type 1 receptor antagonists

eg. Candesartan & Irbesartan

25
Q

Give an example of a drug that achieves its therapeutic effects by inhibiting ion channels.

A

Mechanism of Action - Inhibiting Ion Channels

Calcium channel blocking agents such as amlodipine and verapamil which bind to the alpha1 subunit of the voltage- gated L type calcium channels and block the entry of calcium into the cell.

26
Q

How do Calcium Channel Blocking Agents work?

A

Calcium Channel Blocking Agents

  • Bind to the alpha1 subunit of the voltage-gated L type calcium channels and block the entry of calcium into the cell
  • Block the entry, not the intracellular actions of calcium
  • In blood vessels reduced calcium levels result in vascular smooth muscle relaxation (vasodilation), a reduction in peripheral vascular resistance and a drop in blood pressure
27
Q

What is an example of a drug that works by inhibiting carrier molecules?

A

Mechanism of Drug Action - Inhibiting carrier molecules.

Selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine and sertraline which inhibit the neuronal uptake (re-uptake) of serotonin (5HT)

YR1 - Pharmacology SEM 1 (14 decks)

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