Principles of Pharmacology

Question 1

What is endocrine signalling ?

Answer 1

a cell targets a distant cell through the bloodstream

Question 1

How was Chemical Transmission discovered ?

Answer 1

Loewi showed that stimulation of the vagosympathetic trunk connected to an isolated and cannulated frog’s heart could cause the release into the cannula of a substance (‘Vagusstoff’) that, if the cannula fluid was transferred from the first heart to a second, would inhibit the second heart.

Question 2

What are the 2 groups of mediators and give examples ?

Answer 2

(1) Mediators which are Preformed are stored in vesicles from which they are released by exocytosis- allows for ‘rapid’ (msec) communication
(2) Mediators produced on demand released by diffusion or constitutive secretion take longer (minutes-hours) to act

Question 3

What is paracrine signalling?

Answer 3

a cell produces a signal to induce changes in nearby cells

Question 4

What is contact-dependent signalling ?

Answer 4

cell–cell or cell–extracellular matrix signalling in multicellular organisms that requires close contact. In this type of signalling, a ligand on one surface binds to a receptor on another adjacent surface.

Question 5

What is synaptic signalling ?

Answer 5

Synaptic signaling is similar to paracrine signaling but there is a special structure called the synapse between the cell originating and the cell receiving the signal.

Question 6

What is an Agonist ?

Answer 6

Drugs or chemical mediators that bind to a receptor producing a response are referred to as agonists
Eg. pilocarpine, nicotine, acetylcholine, morphine

Question 7

What is an Antagonist ?

Answer 7

Drugs that prevent or inhibit the response of an agonist. They may bind to the receptor but DO NOT elicit a response
Majority of clinically useful drugs
Eg. atropine, curare, naloxone

Question 8

What are ionotropic receptors ?

Answer 8

Ligand-gated channels involved with fast synaptic transmission

Eg. Nicotinic Ach Receptor, GABA Receptor, Glutamate (NMDA, AMPA, Kainate) receptors, P2X receptors etc.

Question 9

What is a ligand ?

Answer 9

a molecule that binds to the receptor, agonist ir antagonist

Question 10

What are metabotropic receptors ?

Answer 10

G protein coupled receptors

Question 11

What happens when an agonist binds to a GPCR ?

Answer 11

G protien is activated (20 differtn types). That G protein will control the activity of a variety of downstream effector molecules. These molecules may be enzymes involved in production of 2nd messengers (cAMP) or iron channels

Question 12

What happens when Phospholipase C is activated by GPCRs?

Answer 12

Phospholipase C activation by GPCRsleads to generation of the second messengers IP3 and DAG & increased intracellular Ca2+ and activation of protein kinase C

Question 13

What is the Sympathetic Pathway ?

Answer 13

Fight or Flight – activated when defending or running away
Exercise, excitement, emergency, embarrassment
Co-ordinated, whole body response
OR
Discrete and organ specific

Question 14

What is the Parasympathetic pathway ?

Answer 14

Rest and digest
Digestion, defecation, and diuresis(urinating)
Functions in a discrete, organ specific manner

Question 15

Features of Preganglionic neurones ?

Answer 15

Ionotropic receptor (NICOTONIC Ach receptor), lets ions move through it itself
Always cholinergic fibres i.e release Ach as their primary neurotransmitter
Ach activates nicotinic receptors on the postsynaptic cell

Question 16

What sort of neurones are found in the sympathtic pathway?

Answer 16

Short, cholinergic preganglionic neurons from thoracic and lumbar spinal cord
Long, adrenergic postganglionic neurons
Target tissue expresses α- and β- adrenergic receptors (G protein receptrors)

Question 17

Why is the adrenal medulla an exception to the anatomical organization?

Answer 17

The adrenal medulla acts as a modified postganglionic neuron and causes cells in adrenal medulla to release adrenaline.

Adrenaline is acting as a neurohormone when released from the adrenal medulla

Question 17

What sort of neurons are found in the parasympathetic pathway?

Answer 17

The adrenal medulla acts as a modified postganglionic neuron and causes cells in adrenal medulla to release adrenaline.

Adrenaline is acting as a neurohormone when released from the adrenal medulla

Question 18

Whta is the implortance of the vagus nerve

Answer 18

Carries 80 % of parasympathetic outflow and tonnes of visceral afferents

Question 19

What does the spinal cord and brainsteam nuclei do ?

Answer 19

Spinal cord
Mediates autonomic reflexes
Receives sensory afferent and brainstem input

Brainstem nuclei
Mediate autonomic reflexes

Question 19

What does the spinal cord and brainsteam nuclei do ?

Answer 19

Spinal cord
Mediates autonomic reflexes
Receives sensory afferent and brainstem input

Brainstem nuclei
Mediate autonomic reflexes

Question 20

How does the forebrain regulate ANS output ?

Answer 20

Minimal conscious cortical control BUT cortical processes do regulate autonomic output
For example:
anxiety and stress can lead to GI disturbance
fear initiates fight or flight response (limbic system)

Question 21

How do visceral afferents regulate ANS output

Answer 21

Sensory input from visceral afferent neurons takes priority over cortical functions i.e. nothing else seems to matter
For example, bladder distension.

Question 22

What are the clinical uses of adrenoreceptor antagonists ?

Answer 22

Hypertension - prazosin (a1 selective)
Heart failure - carvedilol (a & b)
Anxiety (somatic symptoms) propranolol (b1 & b2)

Question 23

What are the clinical uses of adrenoreceptor agonists ?

Answer 23

1.Adrenaline (non-selective)Cardiovascular system
Cardiac Arrest Adrenaline
Anaphylaxis Adrenaline

2.B2 selective
Respiratory system
Bronchodilator Salbutamol (b2 selective)
Nasal decongestant Ephedrine (indirectly acting sympathomimetic drug ie. causes NA release)

Question 24

What are the effects of the Muscuranic antagonist Atropine