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Toxicology > Midterm > Flashcards

Midterm Flashcards

1
Q

The amount of a substance administered at one time = ?

A

Dose

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2
Q

What is exposure dose?

A

The amount of xenobiotics encountered in the environment

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3
Q

The actual amount of the exposed dose that enters the body = ?

A

Absorbed dose

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4
Q

The quantity administered usually orally or by injection = ?

A

Administered Dose

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5
Q

What is total dose?

A

The sum of all individual doses.

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6
Q

What does Fractionating mean?

A

When you split up the total dose as to decrease the probability that the total dose will cause toxicity.
** reason = the body often can repair the effect of each subtoxic dose if sufficient time passes before receiving the next dose.

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7
Q

The clinical and toxic effects of a dose must be related to ___ , ___ & ___

A

Age, body size & time

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8
Q

A common dose measurement is?

A

mg/kg

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9
Q

Why is knowledge of the dose-response relationship important? (3)

A
  1. Establishes causality that the chemical has in fact induced the observed effects.
  2. Establishes the lowest dose where an induced effect occurs - the threshold effect.
  3. Determines the rate at which injury builds up - the slope for the dose response.
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10
Q

What form dose the dose response curve normally take?

A

Sigmoid curve

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11
Q

The point at which toxicity first appears is known as?

A

The Threshold dose level

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12
Q

When does the threshold for toxic effects occur?

A

At the point where the body’s ability to detoxify a xenobiotic or repair toxic injury has been exceeded.

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13
Q

The usual measure for variability of a toxic response is the standard deviation. One standard deviation represents what percent of the responses?

A

68%

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14
Q

What is LD50?

A

This is a common dose estimate for acute toxicity. This is a statistically derived dose at which 50% of the individuals will be expected to die.

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15
Q

The toxicity of a substance depends on what factors?

A 
Form, and innate chemical activity
Dosage
Exposure route
Species
Age 
Sex
Ability to absorb 
Metabolism 
Distribution within the body
Excretion
Presence of other chemicals
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16
Q

The innate chemical activity of substances varies greatly. Some can quickly damage cells causing immediate death while others slowly interfere. For example hydrogen cyanid binds to _________ resulting in ________.

A

Cytochrome oxidase resulting in hypoxia and rapid death.

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17
Q

Nicotine binds to what type of receptors in the CNS?

A

Cholinergic

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18
Q

______ is the most important critical factor in determining if a substance will be an acute or chronic toxicant.

A

Dosage

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19
Q

Ingested chemicals, when absorbed from the intestine distribute first to?

A

Liver and may be immediately detoxified.

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20
Q

What is meant by selective toxicity?

A

Refers to species differences in toxicity between two species simultaneously exposed.

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21
Q

what are the two types of metabolism?

A

Detoxification and bioactivation

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22
Q

What is meant by detoxification?

A

The process by which a xenobiotic is converted to a less toxic form.
This is a natural defence mechanism of the organism.
Generally detox = converting lipid-soluble compounds to polar compounds.

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23
Q

What is Bioactivation?

A

Bioactivation is the process by which a xenobiotic may be converted to more reactive or toxic form.

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24
Q

What is a major determinant of whether or not a toxicant will damage cells?

A

Its lipid solubility.

Lipid soluble = readily penetrates cell membranes

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25
Q

What is the primary excretory organ? What are the other two organs that follow in function?

A

Kidney
GI Tract
Lungs (for gases)
**xenobiotics may also be excreted in sweat, tears, and milk.

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26
Q

When the presence of other chemicals decreases toxicity this is known as?

A

Antagonism

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27
Q

When a chemical adds to the toxicity this is termed?

A

Additivity

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28
Q

When a chemical increases toxicity this is termed?

A

Synergism or potentiation

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29
Q

Define interaction

A

The effect that one chemical has on the toxic effect of another chemical.

30
Q

T or F

Additivity is the least common type of drug interaction

A

False

Most common

31
Q

T or F

Antagonism is often a desirable effect in toxicology

A

True

Often the basis for most antidotes.

32
Q

Give an example of a chemical antagonism

A

Mercury toxicity can be reduced by chelating (binding) the mercury ions with dimercaprol

33
Q

Swallowed poison is absorbed by introducing charcoal into the stomach is what type of antagonism

A

Disposition Antagonism

34
Q

_______ occurs when a chemical that does not have a specific toxic effect makes another chemical more toxic.

A

Potentiation

35
Q

What is disposition?

A

Often used in place of toxicokinetics to describe the time-course of movement of chemicals through the body

36
Q

Ingested and inhaled materials are still considered outside the body until when?

A

They cross the cellular barriers of the GI tract or respiratory system.

37
Q

What are the factors that affect the likelihood that a xenobiotic will be absorbed?

A

Route of exposure
Concentration of the substance at the site of contact.
Chemical and physical properties of the substance.

38
Q

T or F

Due to such route-specific differences in absorption, xenobitocis are often ranked for hazard in accordance with the route of exposure.

A

True

39
Q

What route of exposure is the main route for many pharmaceuticals?

A

GI

**environment to food and water contaminants as well

40
Q

What are the primary types of specialized transport mechanisms?

A

Facilitated Diffusion
Active Transport
Endocytosis (phagocytosis & pinocytosis)

41
Q

Whittier the properties of a chemical substance that affects its ability for passive transfer?

A

Lipid Solubility
Molecular Size
Degree of ionization

42
Q

T or F

In general, highly ionized chemicals have low lipid solubility and pass with difficulty through the lipid membrane

A

True

43
Q

Most aqueous pores allow chemicals of what molecular weight to pass through?

A

100-200

44
Q

What pores allow for larger sized chemicals to pass through? What is the molecular weight of these chemicals?

A

Capillaries and Kidney Glomeruli

- 50 000

45
Q

Phagocytosis is very important process in what areas of the body?

A

Lung

Certain liver and spleen cells.

46
Q

What are the three main factors that affect absorption within the various sites of the gastrointestinal tract?

A

Types of cells at the specific site
Period of time that the substance remains at the site
pH of stomach or intestinal contents at the site.

47
Q

T or F

In the stomach weak acids are absorbed and bases are not

A

True

48
Q

T or F
The small intestine has a pH near neutral and both weak bases and weak acids are ionized and are usually readily absorbed by passive diffusion

A

False

are UNIONIZED

49
Q

What are the three basic regions to the respiratory tract

A
  1. nasopharyngeal
  2. Tracheobronchial
  3. Pulmonary
50
Q

Absorption through the alveolar membrane is by?

A

Passive Diffusion

51
Q

The only way to increase the amount of a toxin to absorbed is to increase the rate and depth of breathing. What is the term describing this?

A

Ventilation-limitation

52
Q

What is flow-limitation

A

When you increase absorption by increasing the rate of blood supply to the lung.

53
Q

Why does minimal absorption take place in the nasopharyngeal region?

A

Due to the cell thickness of the mucosa and the rapid movement of gases and particles through the region.

54
Q

Coal dust and asbestos fibres may lead to what conditions?

A

Black lung or asbestosis respectively

55
Q 
Which of the following can passthrough the skin and cause nerve damage:
Hexane
Carbon Tetrachloride
Ether 
Organophosphate pesticides
A

Hexane

56
Q

What layer is the most important in regulation penetration of a skin contaminant?

A

Epidermis particularly the stratum corneum

57
Q

What is the stratum corneum made of?

A

Keratin

58
Q

Where is the stratum corneum the thinnest?

A

Axillary

Inquinal and Scrotum especially.

59
Q

The most prevalent skin conditions that enhance dermal absorption are?

A

Skin burns and dermatitis

60
Q

What is meant by parenteral route?

A

Injection into the body via syringe and hollow needle.

61
Q

The total volume of body fluids in which toxicant is distributed is known as?

A

The apparent volume of distribution Vd and is expressed in litres

62
Q

T or F

If a toxicant is distributed only in the plasma a high Vd results, and if a toxicant is distributed in all sites there is a lower Vd

A

True

Greater dilution in all the sites compared to just the plasma

63
Q

body burden = _____ x ______

A

plasma conc x VD

64
Q

What is meant by the first pass effect?

A

Toxicants entering the GI tract or peritoneum are immediately subject to biotransformation or excretion by the liver and elimination by the lung.

65
Q

The term used to integrate all the processes of distribution, biotransformation, and elimination is?

A

Disposition

66
Q

Disposition models are named for the number of areas of the body that the chemical may go to. What are these areas termed?

A

Compartments

67
Q

What is the one-compartment model?

A

This describes the disposition of a substance that is introduced and distributed instantaneously and evenly in the body, and eliminated at a rate and amount that is proportional to the amount left in the body.

68
Q

T or F

A half-life for a chemical whose kinetic behaviour fits a one-compartment model is often referred to as the “biological half-life”

A

False

Two-compartment model

1 compartment = Half life which is just the time it takes for half of the chemical to be lost from the plasma.

69
Q

The liver receives what percent of cardiac output?

A

roughly 28%

70
Q

What is the most abundant plasma protein that binds toxicants?

A

Albumin

71
Q

What are the primary sites for toxicant storage?

A

Adipose tissue
Bone
Liver
Kidneys

72
Q

T or F

Toxicants that are lipophobic, polar and high molecular weight are readily absorbed through the cell membranes of the skin, GI and lung

A

False

Lipophilic, non-polar, and low molecular weight.

Toxicology (1 decks)

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