Adrenal medulla Flashcards by Reza Ghasemian

ß2 target tissues

vascular smooth muscle of

SKELETAL Muscle

GI tract, wall

Bladder, wall Bronchioles

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catecholamine storage

storage vesicles of chromaffin cells

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Conversion of Tyr to DOPA takes place in —— and is regulated by——.

Cytosol ( TYR → DOPA).

ACh released from preganglionic sysmpathetic neurons (nicotinic receptor).

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ß1 target tissues

Heart

Salivary glands

adipose tissue

kidneys

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Control the stimulation of catecholamine release

hypothalamus and the brain stem

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À receptors are more sensitive to (EPi or NE)

Norepinephrine (NE)

ANEEE

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a2 mechanism of action

Inhibition of adenylyl cyclase, dec. cAMP

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Compate the effects of medullary hormones vs NTs

medullary hormones- Global

NT’s - Local

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COMT and it’s function

Catechol-O-methyl transfrase – inactivates catecholamines

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Adrenal medulla action during an exercise:

How simoultaneously increase CO and bld flow to skeletal muscle:

B2 adrenergic receptors of skeletal muscle vasculature is coupled to AC which cause an inc. cAMP.

In cardiac muscle, an inc. in cAMP, inhibits phosphorylation of MLC (myosin light chain).

The combination of the two results in an increase in O2 availibility. (B2 is also a bronchiodialator)

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Stimulates NE ⇒ Epi

Cortisol (adrenal cortex)

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The modulator of the following synthetic step (catecholamine synthesis):

NE –> Epi

Cortisol released by adrenal cortex

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The adrenergic receptor(s) with higer affinity for NE (NE>E):

All the ones + B3

a1, B1

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what are the cells capable of storing catecholamines:

catecholamine cells

80% release NE

20% Epi

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à1 target tissues

vascular smooth muscle skin renal, splanchnic, GI tract SPINCTERS bladder, sphincters radial muscles, iris

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cells responsible for synthesis and release of catecholamines

chromaffin- adrenal medula

Adrenal medulla action on

1- veind and lymphatics

2- skeletal muscle arterioles

3- splanchnic arterioles

1- veins and lymphatic-

à vasocistriction ⇒ inc. venus return

2- skeletal muscle arterioles-

ß2 vasodialation ⇒ inc. blood flow

3- Splanchnic arterioles

à vasoconstriction ⇒ red. blood flow to GI

ß receptors are more sensitive to (Epi or NE).

EPI BEEPEE

Parent compound of catecholamines:

Tyr

Hormonal reinforcement of adrenal medulla during exercise

1- ß cells- à2 Receptors.

2- à cells- ß2 Receptors.

1- dec. insulin

2- inc glucagon

physiological effect of medullary hormones

Global

Inc, HR and contractile force

Skeletal mucles blood vessels DIALATED

blood vessel constriction

Bronciole dialation

lipolysis stimulation

Inc metabolic rate-

Increase O₂consumption and heat production

breakdown glycogen in skeletal muscle

pupil dialation

Cortex secrets steroids, while medulla secret ——

catecholamines- epinephrine, norepinephrine

à2 target tissues

GI tract, wall

How the followings are acheived by adrenal medula during exercise in order to **conserve energy**: Inc Blood glusoce Inc Blood ketone bodies (KB) Inc Blood FFA Inc Blood Lactate Inc Blood Glycerol

GI and urinary tracts - B2- dec motility Adipose- B2-B3- inc lipolysis- dec. glucose uptake liver B2- Increased ( glycogenolysis, gluconeogenesis, and ketogenesis) Skeletal muscle B2- inc glycogenolysis, decreased Glucose uptake

The recptor with equal affinity for E and NE (E=NE)

a2 mechanism of action inhibition of AC (The only inhibitory)

Catecholamine a- transport b- inactivation c- excretion

a- transported in blood: **FREE** or **SULFATE conj** with short half life b- Inactivation- 1. target tissue uptake, 2. MAO 3. COMT inactive metabolites c- Excrete in urine

**Rate determining** step of catecholamine synthesis

dopa conversion to norepinephrine (NE) ## Footnote **DOPA → NE**

**Both *_postganglionic sympathetic_*** neurons and ***_chromaffin cells_*** are derived from:

neuronal crest

The main regulator of the catecholamine synthesis and release:

Hypothalamus and brain stem

The adrenergic receptor with higher affinity for E ( E\>NE):

B (1 and 2) adrenergic mechanism of action

Stimulation of AC, Inc. cAMP

ACh released from preganglionic sysmpathetic neurons (nicotinic receptor) modulates these two synthetic steps of catecholamine synthesis:

Tyrosine --\> XDopa Dopa --\> NE

What are the stimuli for catecholamine release: What is the mechanism of release:

Stress is the stimuli for release (catecholamines are stress hormones) Mode of release: exocytosis

**Stimuli** for catecholamine release and its **mechanism**

Stress as stimuli- stimulation - ACh binding to nicotinic receptors Mechanism: exocytosis