Autonomic Nervous System 3 Flashcards
Describe the synthesis of dopamine, adrenaline and noradrenalin
- Tyrosine converted to DOPA by Tyrosine hyroxylase
- DOPA converted into dopamine by DOPA decarboxylase
- Dopamine converted into Noradrenaline by DBH
- Noradrealine converted into adrenaline by PNMT.
How can noradrenaline inhibit the release of more Noradrenaline?
By acting upon α2 adrenoceptors
How is the action of noradrenaline limited and how does this occur?
It is limited by re-uptake; this occurs by the enzyme NET taking NA from the ECF into the cell and then VMAT which repackages the NA into vesicles
What is the function of Monoamine oxidase (MAO)
To breakdown excessive NA to prevent a level that is too high for extracellular fluid. However it can also breakdown Dopamine.
Name some of the ways in which drugs can affect noradrenergic neurons
- Affect catecholamine synthesis (methyldopa)
- Affect catecholamine release (Amphetamines or clonidine)
- Inhibit catecholamine uptake (NET inhibitors - cocaine, tricylic antidepressants)
- Inhibit catecholamine metabolic degradation (MAO inhibitors - depression)
What are teh different groups of adernegic receptors and what type of receptor are they
- Metabotropbic receptors (G-protein couples receptors)
- Two main groups, Alpha (α1 and α2) and beta (β1, β2 and β3)
What are the main locations, cellular response and functional ANS response of receptor α1
Locations - Cardiovascular, GI tract and Genitourinary
Cellular response - Increase in IP3 and DAG
Functional Response - Vasoconstriction and Smooth muscle contraction (GI and GU sphincters)
What are the main locations, cellular response and functional ANS response of receptor α2
Location - Neuronal
Cell Response - Decrease cAMP
Function - Decrease transmitter release
What are the main locations, cellular response and functional ANS response of receptor β1
Functional - Heart and kidneys
Cell response - Increase cAMP
Response - Increased cardiac rate and force, and renin release
What are the main locations, cellular response and functional ANS response of receptor β2
Location - Lungs, Smooth muscle, Skeletal muscle
Cell response - Increased cAMP
Response - Bronchodilation, Relaxation of visceral smooth muscle, vasodilation of vessels in skeletal muscle.
What drug is used for nasal congestion and how does it work?
Phenylephrine - Constriction of airway blood vessels (α1)
What drugs are used for asthma?
Salbutamol or Salmeterol which all cause bronchodilation (β2)
What is the difference between Salbutamol and Salmeterol
Salbutamol = Short acting
Salmeterol =Long lasting
What can they give pregnant women for premature labour
Salbutamol or Turbutaline, they cause the relaxation of uterine smooth muscle to stop giving
How can the sympathetic NS stimulate cardiac output and total peripheral resistance
Cardiac Output - Increasing heart rate and increasing volume pumped out in each stroke which is mediated by β1 receptor.
Total Peripheral Resistance - By contracting blood vessels which is mediated by α1
In cardiogenic shock, what drug can you give?
Dobutamine as it increase the heart rate and force by acting on β1 receptors.
What drugs can you give for Hypertension
Prazosin - vasodilation by blocking α1 receptors
Propranolol - Decreases heart rate, force and renin released by blocking β1
Atenolol - Decreases heart rate, force and renin released by blocking β1
Clonidine - Stimulation of pre-synaptic α2 receptors to decrease NA release
What drug is used in cardiac arrests?
Adrenaline - As it causes vasoconstriction by acting on α1 and increase heart rate and force by acting on β1
What drug is used in Anaphylaxis?
Andrenaline because it causes vasoconstriction (α1), increases heart rate and force (β1), Bronchodilation (β2) and decreases histamine release by mass cells (β2)
What drug can be used with a swollen prostate that causes problems with passing urine
Prazosin - relax bladder neck and prostate capsule by blocking α1 receptors
