Adrenal Medulla: Catecholamines and Adrenergic Receptors Flashcards
True or False
The Adrenal medulla is part of the autonomic nervous system which is composed of sympathetic and parasympathetic systems
True
Sympathetic
preganglionic nerves exit the central nervous system via the thoracic and lumbar spinal nerves
- secrete norepinephrine as neurotransmitter at synaptic junctions
Parasympathetic
Preganglionic nerves exit the central nervous system by the cranial nerves and sacral spinal nerves
Adrenal Medulla
lack axons and secrete their neurotransmitter (epinephrine) directly into the blood)
- Blood acts as synapse carrying epinephrine to receptors throughout the body
Adrenal Medulla is under the control of ….
Autonomic sympathetic system
Chromaffin cells
- produce EPI and NEP
- released into the blood (acts as a synapse but instead of a post ganglionic neuron)
Catecholamine Biosynthesis
Tyrosine
Dopamine
Norepinephrine
(PNMT) –> epinephrine
Tyrosine, Dopamine, Norepinephrine happen …
Outside the Adrenal medulla b/c post ganglionic neurons»_space; produce catecholamine
Local Cortisol
- diffused cortisol into the medulla stimulating PNMT to produce epinephrine from norepinephrine
PNMT
Limiting step for the conversion of norepinephrine into Epinephrine
Epinephrine: 80-85% of the catecholamine secreted by the …
adrenal medullar cells
- cells bathed by blood coming from the adrenal cortex
Norepinephrine 15-20& of most NE in circulation originates from
leakages of adrenergic neurons
Catecholamines originate from 2 sources
Chromaffin cells and sympathetic neurons
primary source of circulating norepinephrine is
spillover from sympathetic nerves innervating blood vessels
high sympathetic nerve activation
small amount of norepinephrine that is diffused into the blood and circulates throughout the body increases dramatically
Common stimuli for catecholamine release
- exercise
- hypoglycemia
- hypotension
- hypoxia
- hemorrhage
- heart failure
- exposure to cold
- pain
- emotional distress
Actions of catecholamines
Flight or flight response
- fast response mediated by nervous reflex
- epinephrine release from the adrenal medulla
- norepinephrine release in adrenergic synapse
EPI (fight or flight response)
- breakdown of hepatic glycogen (stored glu)
- increase heart rate (chronotropic effect)
- increase stroke volume (strength of heart contraction- inotropic effect)
- increase peripheral vasoconstriction
- increase blood pressure
- dilation of coronary arteries & dilation of muscle vessels
Epinephrine and Norepinephrine in the bloodstream has a
improves response
EPI in the adipose tissue in response to hypoglycemia
EPI (in the bloodstream) binds to receptor on adipocyte to stimulate (HSL), which breaks down triglycerides into FA and glycerol
FFA and glycerol in the blood are taken up bby hepatocyte where FFA are made into ketones and Glycerol is broken down to glucose by (PEPCK and G-6-P) and input of cortisol
