Patient: Alpha Adrenoceptors Flashcards
Alpha Adrenoceptors
Two branches of the autonomic nervous system and what kind of receptors lie there
Sympathetic- noradrenaline
Parasympathetic - acetylcholine
Alpha Adrenoceptors
Adrenal Medulla
Adrenaline (epinephrine)
which is under he sympathetic nervous system
Alpha Adrenoceptors
Adenoreceptors modulate the “fight or flight” response. Name 9 examples of tissues where they can act
- Blood vessels
- heart
- Lungs
- GI tract
- Salivary glands
- bladder
- genitalia
- eyes
- sweat glands
Alpha Adrenoceptors
Name 3 adrenoreceptors
Alpha1, alpha2
beta1, beta2, beta3
Alpha Adrenoceptors
Functional responses of alpha1 adrenoceptors
- GPCR - Galphaq
- Increases Ca2+ concentration via..activating phospholipase C–>IP3
- vasoconstriction (increase BP)
- Contraction of visceral smooth muscle e.g. bladder sphincter, uterus, iris radial muscle, seminal tract, pilomotor muscles
- Relax GI tract
Alpha Adrenoceptors
Define seminal tract
Secrete semen
Alpha Adrenoceptors
Define pilomotor muscles
Contraction of the smooth muscle of the skin caused by mild application of a tactile stimulus or by local cooling and resulting in goose bumps
Alpha Adrenoceptors
Functional response of alpha2 adrenoceptors
- Decrease in noradrenaline and acetylcholine transmitter release
- Decrease in insulin release
- GPCR Galphai activates adenylyl cyclase
- causes reduction in cAMP
- Decrease in Protein kinase A
Alpha Adrenoceptors
Functional response of beta1 adrenoceptors in the
Heart
Kidney
Adipocytes
Binds GPCR Galphas activates adenylyl cyclase increase in cAMP increase in protein kinase A hence: Heart - Increase heart rate (SA node) and increase force of contraction Kidney - release of renin Adipocytes - activates lipolysis
Alpha Adrenoceptors
Describe what renin is
Hormone that affects:
- Na reabsorption
- angiotensin 2
- vasoconstrictor
Alpha Adrenoceptors
Functional response of beta2 adrenoceptors
GPCR Galpha2s activates adenylyl cyclase increase in cAMP increase PKA
Bronchodilation-vasodilation (sk muscle) very little change in BP
- relax visceral smooth muscle
- bladder
- detrusor muscle
- uterus
- ciliary muscle
- seminal tact
- muscle tremor
- glcogenolysis
Alpha Adrenoceptors
Define detrusor muscle
Muscle that forms layer of wall in the bladder
Alpha Adrenoceptors
Define ciliary muscle
muscle in the eye
forms part of the ciliary body
Alpha Adrenoceptors
Name an alpha1 agonist
Phenylephrine
Alpha Adrenoceptors
Name an alpha2 agonist
Clonidine
Alpha Adrenoceptors
Name a beta1 agonist
Dobutamine
Alpha Adrenoceptors
Name a beta2 agonist
Salbutamol
Alpha Adrenoceptors
Name an agonist that works on both alpha1 and alpha2 receptors
Methoxamine
Alpha Adrenoceptors
Name an agonist that works on both beta1 and beta2 receptors
Isoprenaline
Alpha Adrenoceptors
Name an agnoist compound that work on alpha1, alpha2 and beta1 adrenoreceptors
Noradrenaline
Alpha Adrenoceptors
Name an agnoist that works on alpha1, alpha2, beta1, beta2 receptors (all 4)
Adrenaline
Alpha Adrenoceptors
Name an alpha1 antagonist for adrenoreceptors
Prazosin
Alpha Adrenoceptors
Name an alpha2 antagonist for adrenoceptors
Yohimbine (not in clinical use)
Alpha Adrenoceptors
Name a beta1 antagonist for adrenoceptors
atenolol
Alpha Adrenoceptors
Name a beta2 antagonist for adrenoceptors
Butoxamine
Alpha Adrenoceptors
Name two antagonists that work on both alpha1 and alpha2 adrenoceptors
Phentolamine (competitive)
Phenoxybenzamine (non-competitive)
Alpha Adrenoceptors
Name an antagonist that works on both beta1 and beta2 adrenoceptors
Propanolol
Alpha Adrenoceptors
Structural difference between noradrenaline and adrenaline
Same but Adrenaline has a CH3 off the amine group
whereas noradrenaline just has a H atom off it
Alpha Adrenoceptors
How is adrenaline for cardiopulmonary resuscitation
As an adjunct to cardiopulmonary resuscitation
By causing arterial and venous vasoconstriction, adrenaline increases the blood pressure
Blood flow in coronary and cerebral arteries is promoted
In ventricular fibrillation, adrenaline may coarsen the ECG waveform, and render electrical cardio-version more likely to suceed
Alpha Adrenoceptors
Name 2 clinical uses of adrenaline
- adjunct to cardiopulmonary resuscitation
- to control anaphylactic shock
Alpha Adrenoceptors
Name symptoms of anaphylactic shock
- Profound hypotension
- Largngeal Oedema
- Bronchospasm
Alpha Adrenoceptors
2 main ways to control anaphylactic shock and how to address it therapeutically
1.Restore blood pressure
-Patient with feet raised (supine)
-Adrenaline IV (slowly) or IM every 10 minutes
alpha1 adrenoceptor activated, vasoconstriction occurs and causes an increase in blood pressure
2. Secure the airway/administer oxygen
-Beta2-adrenoceptor
-bronchodilation
-decrease histamine release
Alpha Adrenoceptors
Name 2 drugs you would use to control a case of anaphylactic shock
Chlorpheniramine (Slow IV injection)
Hydrocortisone IV
Alpha Adrenoceptors
How are agonists used to reduce intra-ocular pressure in chronic simple glaucoma?
Adrenaline eyedrops used
They reduce the production of aqueous humor and increase its drainage through the trabecular meshwork
Alpha Adrenoceptors
How are agonists used alongside local anaesthetics?
Local anaesthetics cause vasodilation and hence facilitate their own redistribution
Addition of adrenaline to local anaesthetic causes vasoconstriction (mediated by alpha-adrenoceptors) and prolongs the action of the local anaesthetic and reduces its systemic toxicity
Alpha Adrenoceptors
When do you avoid use of vasoconstrictors?
Near bases of body appendages and digits
Alpha Adrenoceptors
What is Phenylephrine used for?
alpha1-selective agonist at adrenoceptors
it is used to offset the hypotension attributable to sympathetic block induced by spinal or epidural anaesthesia
ALSO:
To produce brief periods of mydriasis (pupil dilation) using eyedrops
Alpha Adrenoceptors
Where is phenylephrine injected for:
1-Spinal anaesthesia
2-epidural anaesthesia
1-injected into subarachnoid space
2-epidural space
Alpha Adrenoceptors
What is a Phaeochromocytoma? How is it treated?
Tumour of the adrenal medulla that secretes adrenaline erratically, causing episodes of severe hypertension
treated with antagnoists of adrenoceptors: Phentolamine for treatment
and Phenoxybenzmine is used during surgery
Alpha Adrenoceptors
What does Prazosin do?
- dilates arterioles and veins by blocking alpha1 adrenoceptors
- used where other therapy has proven ineffective or unacceptable
- used also in the treatment of benign prostatic hyperlplasia
Alpha Adrenoceptors
Unwanted effects of prazosin
postural hypotension (fades) retrograde ejaculation (relaxation of bladder neck)
Alpha Adrenoceptors
What is benign prostatic hyperplasia?
Swelling of prostate that districts uretha, resulting in patient being unable to release urine
