Introduction to receptors

Question 1

Define pharmacology.

Answer 1

The study of the effects of chemical substances on the function of living systems in relation to their therapeutic value - it involves aspects of physiology and chemistry.

Question 2

What are drugs?

Answer 2

1. Chemical substances of known structure other than a nutrient or an essential dietary ingredient, which, when administered to a living organism, produces a biological effect.
2. They can be synthetic, from plants, animals or from genetic engineering.

Question 3

What are medicines?

Answer 3

1. Chemical preparations is a chemical preparation, which usually, but not necessarily, contains one or more drugs
2. Administered with the intention of producing a therapeutic effect.
3. Medicines usually contain other substances (excipients, stabilisers, solvents, etc.) besides the active drug, to make them more convenient to use.

Question 4

What is pharmacokinetics?

Answer 4

How an organism reacts to a drug/processes the drug, absorption, distribution, metabolism and secretion.

Question 5

What is pharmacodynamics?

Answer 5

How the drug affects the organism.

Question 6

Who introduced opium and mercury into medicine for the first time?

Answer 6

Paracelsus.

Question 7

What natural substances were involved in pharmacology before the 19th century?

Answer 7

1. Quinine (malaria)
2. digitalis (heart failure)
3. atropine (pupils dilate)
4. ephedrine (active principle of herb ‘ma-huang’).

Question 8

What are the two main theories of neurotransmission?

Answer 8

The electrical theory and the humoral theory.

Question 9

What are the main points of the electrical theory?

Answer 9

1. Electrical current from a large muscle mass may excite a nerve.
2. Effect should be bi-directional.
3. However, the current in the nerve is too small to excite a muscle; amplification required.
4. Amplification occurs at the nerve/muscle junction and is achieved chemically.

Question 10

What are the main points of the humoral (chemical) theory?

Answer 10

1. Transmission across the gap is uni-directional.
2. Delay in transmission across the gap.
3. Fatigue occurs more readily at junctions.
4. Drugs may act selectively at synapses/junctions.

Question 11

What did Schmiedeberg discover?

Answer 11

Muscarine (found in certain toadstools) can stimulate the vagus nerve of the heart - decreasing heart rate. (vagul stimulation)

Question 12

What synthetic drugs appeared in the 20th century?

Answer 12

Barbituarates, local anaesthetics, antimicrobial chemotherapy and antibacterials.

Question 13

What did Paul Ehrlich do?

Answer 13

Studied effect of dyes on bacteria

Question 14

What did Henry Dale do?

Answer 14

Conducted studies on histamine and acetylcholine.

Question 15

What did Henry Dale discover?

Answer 15

Noticed Ach was equipotent with muscarine.
Also, that Ach mimicked parasympathetic nerve stimulation and that low doses of Ach were blocked by atropine, but high doses mimicked the effects of nicotine (stimulation of sympathetic ganglionic cells).

Question 16

What was Otto Loewi’s significance?

Answer 16

The first man to discover evidence of chemical transmission in 1921.

Question 17

What was Lowei’s first experiment?

Answer 17

1. Set up two frog hearts
2. Connected vagal fluid of heart 1 to vagal fluid of heart 2 by a pump
3. When the vagus nerve was stimulated- saw reduction in heart rate
4. Noticed second heart also started to slow
5. Concluded that a substance- Vagusstoff- was released from nerve endings of heart 1 and conveyed to heart 2 in perfusion fluid.

Question 18

What was Loewi’s second experiment?

Answer 18

1. The accelerans nerve was stimulated (sympathetic) increases rate of heart 1
2. Then stimulated heart 2 to beat more rapidly
3. He concluded Acceleranstoff was released from sympathetic nerve endings, similar to adrenaline.

Question 19

What did Loewi show Vagusstoff was similar to?

Answer 19

1. Acetylcholine
2. Showed that the effects of both were blocked by atropine and potentiated (increase in power) by physotigmine (inhibits cholinesterase which breaks down Ach).
3. Nerve fibres that released Ach were cholinergic (classified by Dale)

Question 20

What did Loewi show that Acceleranstoff was similar to?

Answer 20

1. Adrenaline

2. nerve fibres that released adrenaline-like substances were adrenergic (classified by Dale)

Question 21

Ehrlich experiments

Answer 21

1. Showed a drug will not work unless it is bound
2. Proposed there was a collection of chemoreceptors on cells for dyes
3. Applied dye, only stuck to cell wall- showed there must be recognition sites in the cell wall