Session 10 - The ANS Flashcards
How does the post-ganglionic innervation of the adrenal glands differ from others?
- Sympathetic postganglionic neurones are the chromaffin cells of the adrenal gland which secrete adrenaline directly
- Activated by stimulation of NA from preganglionic fibre of SNS
What are the results of parasympathetic innervation to the heart?
-Bradycardia (SA node)
-Reduced conduction velocity (AV node)
M2 activation (Gai)
What are the locations and the result of parasympathetic innervation of smooth muscle?
-Bronchiolar contraction
-Increased intestinal mobility (increased contraction)
-Bladder contraction (detrusor)
-Bladder relaxation (sphincter)
-Penile erection
M3 receptor (Gaq)
What is the result of parasympathetic innervation of glandular tissue?
-Increased sweat, salivary, lacrimal secretion
M1/M3 (gaq)
What is the effect of sympathetic innervation of the heart?
-Positive chronotropy (SAnode)
-Positive inotropy (ventricles)
b1 (some B2)
What are the locations and effects of sympathetic innervation of smooth muscle?
- Arteriolar/venous contraction (a1)
- Arteriolar vasodilation in liver, skeletal and myocardium (b2)
- Bronchiolar, intestinal and uterine relaxtion (b2)
- Bladder sphincter contraction
What is the effect of sympathetic innervation to the kidney?
-Renin release
What effect does angiotensin II have on the brain and adrenal cortex?
- Stimulates ADH release from brain to upregulate aquaporin channels
- Stimulates aldosterone release from cortex
Name a glucocorticoid receptor antagonist used to decrease aldosterone release?
-Spironolactone
Describe the autonomic innervation of the prostate gland
Parasympathetic -> stimulates secretion from epithelia
Sympathetic-> smooth muscle contraction
What enzyme is responsible for the synthesis of acetylcholine?
-Choline acetyltransferase
What AchE inhibitor is used to treat myasthenia gravis?
-Pyridostigmine
Why is the use of cholinergic drugs limited?
-They lack selectivity and often produce many unwanted side effects
Name an muscarinic agonist used in glaucoma
-Pilocarpine
Name a muscarnic antagonist used to treat asthma
-Ipratropium
What is a variscosity?
-A vesicle in neurones which contains everything necessary for NA synthesis, store and release
What is NA synthesised from?
-Tyrosine
Briefly outline NA synthesis
Tyrosine -> DOPA (tyrosine hydroxylase)
DOPA-> Dopamine (DOPA decarboxyase)
Dopamine -> NA (Dopamine b-hydroxylase)
How is NA removed from a synaptic cleft?
-Noradrenaline transporter proteins Uptake 1 and Uptake 2 facilitate re-uptake into presynaptic terminal
What ion are uptake 1 and uptake 2 dependant upon?
-Na+
How is NA not cleared by uptake 1 and 2 removed from the synpatic cleft?
-Metabolised by MAO (monoamine oxidase) and COMT (catechol-O-methyltransferase)
How is NA release modulated from pre-synaptic neurones?
- a2-adrenoreceptors present on the pre-synaptic terminal membrane
- Activation of a2 causes dissociation of bg which binds to VOCC
- Reduces Ca influx of ca2+ and thus decreased neurotransmitter release
How do indirect sympathomimetic agents work?
- Enter presynaptic terminal by uptake 1
- Mimic NA and are taken up into neurotransmitter vesicles with higher affinity
- Cause NA to leak from vesicle and into the synaptic cleft by a mechanism other than Ca2+ dependant exocytosis
What are the three drugs used to treat HF?
- B-blocker
- ACE inhibitor
- Diuretic
Name some other neurotransmitters which can be co-released with NA/Ach
- ATP
- NO
- 5-HT
- Neuropeptides (Vasoactive Intestinal Peptide)
