- rate limiting step (most sensitive to disruption) - inhibited by catecholamines

Autonomic Nervous System 3 Flashcards by Hannah Mathias

State the Adrenergic neurotransmitters

Catecholamines :

Dopamine
Adrenaline
Noradrenaline

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Describe the production of adrenaline

Tyrosine

DOPA

Dopamine

Noradrenaline

Adrenaline

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Describe the enzymes produced between each step to produce adrenaline

Tyrosine
(Tyrosine hydroxylate)

DOPA
(DOPA decarboxylase)

Dopamine
(Dopamine Beta-hydroxylase - DBH)

Noradrenaline
(PNMT)

Adrenaline

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Tyrosine hydroxylate

rate limiting step (most sensitive to disruption)
inhibited by catecholamines

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DOPA decarboxylase

METHYLDOPA - inhibits DOPA decarboxylase

Methyldopa is useful in some cases treating hypertension in pregnancy

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Dopamine Beta-hydroxylase

DBH
Membrane bound

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PNMT

Location
Induced by

Mainly located in adrenal medulla
Induced by adrenal cortex hormones

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Function of tyrosine hydroxylate

Converts tyrosine into DOPA

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Function of DOPA decarboxylase

Converts DOPA into Dopamine

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Function of Dopamine Beta-hydroxylase

Converts Dopamine into Noradrenaline

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Function of PNMT

Converts Noradrenaline into Adrenaline

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What is the release of noradrenaline facilitated by ?

Calcium

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How can we limit the duration of action of noradrenaline ?

By re-uptake

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State the mechanisms in place to take noradrenaline back up into cells

NET
VMAT

transporters

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NET transporter

Norepinephrine transporter
75% recaptured by neurons

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Function of NET transporter

Transport nor-adrenaline back into the presynaptic neurones. (75%)

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Alpha 2 Adrenoreceptor location

Presynaptic terminal

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VMAT transporter

“Repackaged” by vesicular monoamine transporter

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Function of VMAT transporter

Packages the nor-adrenaline into vesicles by vesicular monoamine transporter.

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Alpha 2 Adrenoreceptor Function

Reduces Calcium influx
Reduces NA release

Almost exclusively expressed on neurones.

Inhibits further release of noradrenaline if there is an XS already being released out.

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Activation of Alpha 2 Adrenoreceptor

Reduces the amount of noradrenaline released

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Storage of noradrenaline

Stored with ATP in a vesicles in the presynaptic neurone.

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How do amphetamines work ?

Work by slowly, insidiously releasing noradrenaline from cells and bypassing a lot of the feedback mechanisms.

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Results of amphetamines

Large amount of continuous release of noradrenaline in the CNS.

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Describe the action of amphetamines

Making NET and VMAT work in reverse. Rather than taking noradrenaline up and repackaging it, what happens is you displace noradrenaline out and pump it out into the synaptic region.

Amphetamines

Indirectly acting sympathomimetic drugs

What is noradrenaline uptake and degradation affected by ?

Amphetamines Monoamine oxidase inhibitors (MAO) Uptake inhibitors

MAO - Monoamine oxidase

Normally if you get an XS of noradrenaline in the neurone, that isn't packaged within vesicles. It gets degraded by the action of enzymes called monoamine oxidases.

Drugs that affect catecholamine synthesis

Methyldopa

Drugs that affect catecholamine release

Indirectly acting sympathomimetics - amphetamines By acting on alpha-2 adreno-receptors : clonidine

Inhibitors of catecholamine uptake

NET inhibitors Cocaine, Tricyclic antidepressants

Inhibitors of catecholamine metabolic degradation

Monoamine oxidase inhibitors used in depression

Adrenergic receptor type

Metabotropic (G-protein coupled receptors)

State the 2 main groups of adrenoreceptors

Alpha 1 and 2 Beta 1,2 and 3

Alpha 1 - ANS location

Cardiovascular GI tract Genitourinary

Alpha 2 - ANS location

Neuronal

Beta 1 - ANS location

Heart Kidneys

Beta 2 - ANS location

Lungs Smooth muscle Skeletal muscle

Alpha 1 - cellular response

Increases IP3 and DAG

Alpha 2 - cellular response

Decreases cAMP

Beta 1 cellular response

Increases cAMP

Beta 2 cellular response

Increases cAMP

Alpha 1 - Functional ANS response

Vasoconstriction Smooth muscle contraction

Alpha 2 - Functional ANS response

Decreases Transmitter release

Beta 1 - Functional ANS response

Increases cardiac rate Increases cardiac force Renin release

Beta 2 - Functional ANS response

Broncho-dilation Relaxation of visceral smooth muscle Vasodilation (sk. muscle) Tremor

What adrenoreceptor is used for : Upper respiratory tract infection (nasal congestion) ?

Alpha 1 agonist Constriction of airway blood vessels PHENYLEPHRINE

What adrenoreceptor is used for : Asthma ?

Beta 2 agonists All cause bronchodilation SALBUTAMOL or SALMETEROL

Duration of action of salbutamol

SABA Short acting

Duration of action of salmeterol

LABA Long acting

What adrenoreceptor is used for : Premature labour (to delay delivery) ?

Salbutamol Relaxation of uterine smooth muscle Beta 2 agonists

Why use salbutamol instead of salmeterol for premature delivery ?

As soon as the patient is in the right location, you want the effects of the drug to wear off rather than waiting hours for the birth to continue.

How to calculate mean arterial blood pressure ?

Cardiac output X total peripheral resistance Heart X Blood Vessels

Function of sympathetic stimulation on the heart

Increases cardiac output : - By increasing heart rate - By increasing volume pumped on each stroke - Both mediated by beta 1 receptors

Function of sympathetic stimulation on blood vessels

Increases total peripheral resistance : - By constricting blood vessels - Mediated by alpha 1 receptors

What adrenoreceptor is used for : Cardiogenic shock ?

DOBUTAMINE Beta 1 agonists Alpha 1 antagonists Increases heart rate and force

What adrenoreceptor is used for : Hypertension ?

Antagonists for alpha 1 Antagonist for beta 1 Agonist for alpha 2

Function of agonising alpha 2

Prevent the release of noradrenaline Reduce the effect on the heart

Prazosin

Vasodilation by blocking alpa 1 receptors

Propranolol

Decreases heart rate and force by blocking beta 1 receptors Decreases renin release by kidneys (Beta 1)

Atenolol

Decreases heart rate and force by blocking beta 1 receptors Decreases release by kidneys (beta 1)

Clonidine

Stimulation of pre-synaptic alpha 2 receptors to decrease NA release. Also has central effect.

Beta blockers

Often referred to as cardioselective or non-cardioselective. IN asthmatic - non-cardioselective is not permitted

What adrenoreceptor is used for : cardiac arrest ?

ADRENALINE Vasoconstriction Alpha 1 agonist Increases heart rate and force Beta 1 agonist

What adrenoreceptor is used for : Anaphlyaxis ?

ADRENALINE Vasoconstriction Alpha 1 agonist Increases heart rate and force Beta 1 agonist Bronchodilation Beta 2 agonist Decreased histamine release by mast cells Beta 2 agonist

What adrenoreceptor is used for : Benign prostatic hyperplasia ?

Prazosin Alpha 1 antagonists Tamsulosin (prostate specific)

Autonomic Nervous System 3 Flashcards

(66 cards)