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Physiology > Pharmacology > Flashcards

Pharmacology Flashcards

1
Q

Definition of pharmacology

A

Study of effects of drugs on function of living systems

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2
Q

What is a drug?

A

Chemical substance with biological effects

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3
Q

What are receptors?

A

Proteins that recognise and respond to a chemical signal with a binding and functional site

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4
Q

What is a ligand?

A

A chemical that binds to a receptor. Can be endogenous (hormone) or exogenous (applied drug)

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5
Q

Agonist vs Antagonist

A

Agonist: ligand that activates a receptor
Antagonist: ligand that blocks an agonist and doesn’t activate a receptor

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6
Q

Specificity

A

Receptors that are only activated by one endogenous agonist

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7
Q

Potency

A

Amount of agonist needed to induce a given response. Expressed as a dose or concentration

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8
Q

Affinity

A

How effective a ligand binds to its receptor

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9
Q

Efficacy

A

How effective a ligand activates its receptor

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10
Q

Size of response is proportional to…

A

Number of receptors occupied by an agonist

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11
Q

What is the strength of ligand-receptor determined by?

A

Electrical charge interactions, hydrogen bonding and hydrophobic interactions

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12
Q

Law of mass action

A

Rate of chemical reaction is proportional to the product of concentrations of reactants

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13
Q

What does acute mean?

A

Single drug that induces immediate response due to direct action to receptor

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14
Q

What does chronic mean?

A

Repeated drug treatment that induces a delayed response due to indirect action on receptor

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15
Q

Tolerance

A
  • Gradual decrease in effectiveness of drug
  • Chronic treatment can cause tolerance
  • Tolerance occurs because the drug has an effect on homeostasis which minimises drug effects
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16
Q

Downregulation vs Upregulation

A

Downregulation: decrease in the number of receptors on a cell surface
Upregulation: increase in the number of receptors on a cell surface

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17
Q

Desensitisation vs Super sensitivity

A

Desensitisation: reduction in functional response with binding to receptors
Super sensitivity: increase in functional response with binding to receptors

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18
Q

Withdrawal

A

Avoiding drugs completely leading to adverse effects. Avoided by removing drugs gradually

19
Q

Receptor classification

A

Classified based on differences in how functional responses are induced when drug binds to receptors

20
Q

Signal transduction

A

Mechanism involved in translating signal to a response

21
Q

What are receptor subtypes?

A

Endogenous agonists that can bind to and activate more than one receptor

22
Q

What do ion channels do?

A

Mediate very fast synaptic transmission in nervous system and communicate between neurones or between a neuron and a muscle cell

23
Q

How does agonist binding effect ion channels?

A

Allows ions to pass through using proteins to prevent the membrane being hydrophobic

24
Q

What is ion movement based on?

A

Electrochemical gradient where concentration of ions on either side determines movement

25
Q

Name the 3 ion channels

A

Cation channels (positive), anion channels (negative) and ion specific (sodium and potassium)

26
Q

What do G-protein-coupled receptors (GPCRs) do?

A

Involved in fast synaptic transmission. Agonist binding to receptor induces functional response indirectly through G-proteins present in membrane

27
Q

Why are they called G-proteins?

A

Association with guanine nucleotides GTP and GDP and are comprised of a trimetric structure with three units (α, β, and γ)

28
Q

GPCR structure

A

Long third cytoplasmic loop of receptor coupled to G-proteins

29
Q

GPCR activation

A
  • GDP binds with alpha
  • GDP is converted to GTP causing dissociation with complex
  • Resulting in α-GTP with βγ complex
  • These are active forms of G-protein and bind to various effectors in membrane
30
Q

GPCR inactivation

A

Reverse reaction

31
Q

Kinase-linked receptors

A

Mediate slow forms of communication by altering gene transcription and target peptides and hormones

32
Q

What is kinase?

A

An enzyme that phosphorylates proteins

33
Q

What is phosphatase?

A

An enzyme which de-phosphorylates proteins

34
Q

Kinase-linked receptors structure

A

Single large polypeptide chain with one transmembrane domain and large extracellular ligand-binding domain and an intracellular catalytic domain

35
Q

What is dimerization?

A

Two receptors become associated together in membrane

36
Q

Auto-phosphorylation

A

Two receptors phosphorylating themselves

37
Q

Kinase-linked receptors activation

A

Dimerization results in auto-phosphorylation of tyrosine which serves as a binding site for other enzymes

38
Q

Nuclear receptors

A

Mediate very slow forms of communication by altering gene transcription which target hormones and fat-soluble vitamins

39
Q

Orphan receptors

A

Receptors with an unknown ligand

40
Q

How many classes of nuclear receptors are there?

A

2

41
Q

Homodimers vs Heterodimers

A

Homodimers: two identical receptors associate and function together and act outside nucleus
Heterodimers: two different receptors associate and function together and act inside nucleus

42
Q

Class 1 of nuclear receptors

A

Located in cytosol and form homodimers

43
Q

Class 2 of nuclear receptors

A

Located in nucleus and form heterodimers

44
Q

Structure of nuclear receptors

A
  • N-terminal domain (contains co-activator region that binds to transcription factors)
  • DNA binding domain (binds to specific DNA sequences known as hormone response element to alter gene transcription)
  • Hinge region (binding site for two nuclear receptors during dimerization)
  • Ligand binding domain (binding site for ligand that is specific for different receptors).

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