Principles of Pharmacology Flashcards
What is endocrine signalling ?
a cell targets a distant cell through the bloodstream
How was Chemical Transmission discovered ?
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.
What are the 2 groups of mediators and give examples ?
(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
What is paracrine signalling?
a cell produces a signal to induce changes in nearby cells
What is contact-dependent signalling ?
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.
What is synaptic signalling ?
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.
What is an Agonist ?
Drugs or chemical mediators that bind to a receptor producing a response are referred to as agonists
Eg. pilocarpine, nicotine, acetylcholine, morphine
What is an Antagonist ?
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
What are ionotropic receptors ?
Ligand-gated channels involved with fast synaptic transmission
Eg. Nicotinic Ach Receptor, GABA Receptor, Glutamate (NMDA, AMPA, Kainate) receptors, P2X receptors etc.
What is a ligand ?
a molecule that binds to the receptor, agonist ir antagonist
What are metabotropic receptors ?
G protein coupled receptors
What happens when an agonist binds to a GPCR ?
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
What happens when Phospholipase C is activated by GPCRs?
Phospholipase C activation by GPCRsleads to generation of the second messengers IP3 and DAG & increased intracellular Ca2+ and activation of protein kinase C
What is the Sympathetic Pathway ?
Fight or Flight – activated when defending or running away
Exercise, excitement, emergency, embarrassment
Co-ordinated, whole body response
OR
Discrete and organ specific
What is the Parasympathetic pathway ?
Rest and digest
Digestion, defecation, and diuresis(urinating)
Functions in a discrete, organ specific manner
Features of Preganglionic neurones ?
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
What sort of neurones are found in the sympathtic pathway?
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)
Why is the adrenal medulla an exception to the anatomical organization?
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
What sort of neurons are found in the parasympathetic pathway?
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
Whta is the implortance of the vagus nerve
Carries 80 % of parasympathetic outflow and tonnes of visceral afferents
What does the spinal cord and brainsteam nuclei do ?
Spinal cord
Mediates autonomic reflexes
Receives sensory afferent and brainstem input
Brainstem nuclei
Mediate autonomic reflexes
What does the spinal cord and brainsteam nuclei do ?
Spinal cord
Mediates autonomic reflexes
Receives sensory afferent and brainstem input
Brainstem nuclei
Mediate autonomic reflexes
How does the forebrain regulate ANS output ?
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)
How do visceral afferents regulate ANS output
Sensory input from visceral afferent neurons takes priority over cortical functions i.e. nothing else seems to matter
For example, bladder distension.
