SNS Antagonists Flashcards
What do alpha 1 receptors do?
- vasoconstriction
- relax GI tract
What do alpha 2 receptors do?
- inhibit neurotransmitter release
- contract vascular smooth muscle
- CNS effects
What do beta 1 receptors do?
- increased heart rate
- increased contractility
- relax GI tract smooth muscle
- renin release stimulated
What do beta 2 receptors do?
- bronchodilation
- vasodilation
- relax visceral smooth muscle
- hepatic glycogenolysis
What do beta 3 receptors do?
lipolysis
How does the presynaptic neurone monitor the neurotransmitter environment in the synapse?
They also bind to auto receptors on the pre-synaptic neurone (controls later synthesis and release)
What do pre-synaptic alpha 2 adrenoreceptors do?
They negatively affect NA synthesis and release (inhibitory)
What is carvedilol selective/nonselective for?
Non selective a1, b1, b2 antagonist
What causes the vasodilator properties of carvedilol?
the a1 antagonism
What is phentolamine selective/non selective for?
Non selective for alpha (1+2)
What is propranalol selective/non selective for?
Non selective for beta (1+2)
What is prazosin selective for?
alpha 1
What is atenolol selective for?
b1
What is nebivolol and sotalol selective?
N - b1
S - beta receptor selective and inhibits K+ channels
What are the clinical uses of SNS antagonism?
- hypertension
- cardiac arrhythmia
- angina
- glaucoma
What is the implication of hypertension on health?
Single most important risk factor for stroke, causing about 50% of ischaemic strokes (hypertension associated with atherosclerosis)
Accounts for ~25% of heart failure cases
Major risk factor for MI and CKD
How is blood pressure increased?
BLOOD VOLUME, CO AND VASCULAR TONE:
- increases renin
- increased HR and contractility
- venoconstriction
What are some targets for anti hypertensives?
- heart
- kidney
- arterioles
- sympathetic nerves
- CNS (determines BP set point)
Where do beta blockers act?
- CNS β to reduce sympathetic tone
- Heart (B1) β reduce ionotropic and chronotropic effect (this effect disappears in chronic treatment)
- Kidneys (B1) β reduce renin production (common long term feature is a reduction in TPR)
B1-receptor on the pre-synaptic membrane and blockade of this reduces positive feedback on NE release and may contribute to anti-hypertensive effects
What are the unwanted effects of beta blockers?
Bronchoconstriction β little importance unless the patient has an airway disease
Cardiac failure β in patients with heart disease this may be a problem
Hypoglycaemia - B blockers may mask symptoms (tremors etc.) and non-selective B -blockers will also block hepatic glycogenolysis (B2)
Fatigue β reduced CO
Cold extremities β loss of B-receptor mediated vasodilation
Bad dreams