10) Adrenal Medulla Flashcards
The adrenal medulla constitutes __% of the weight of the total adrenal gland.
15
The adrenal medulla and pre-ganglia are part of which nervous system?
- Autonomic
- Sympathetic
The adrenal medulla is under (conscious/unconscious) control.
unconscious control
What is the overall function of the adrenal medulla? What are characteristic effects?
- Coordinates the “fight-or-flight” response
- Increases blood pressure and cardiac output, dilates pupils
What is the function of pre-ganglionic neurons from the spinal cord in terms of the adrenal medulla?
Stimulates medullary modified nervous cells to release hormones
What are the hormones that are synthesized and released from the adrenal medulla?
Catecholamines (norepinephrine and epinephrine)
Which metabolite is the precursor to the catecholamine hormones?
Tyrosine
What is the rate-limiting enzyme in the synthesis of catecholamines?
Tyrosine hydroxylase
(Norephrine/epinephrine) is synthesized from (norepinephrine/epinephrine).
Epinephrine
norepinephrine
What are the four intermediate steps in the biosynthesis of epinephrine?
1) Tyrosine
2) Dopamine
3) Norepinephrine
4) Epinephrine
Which enzyme catalyzes the conversion of norepinephrine to epinephrine?
PNMT
_____ is required to enhance the actions of PNMT.
Cortisol
Stress increases _____, which increases ______.
cortisol
PNMT
Which tissues contain PNMT?
- Lung
- Kidney
- Pancreas
- Adrenal medulla
What is the effect of a decreased quantity of PNMT on the biosynthesis of catecholamines?
- Less cortisol
- Less PNMT
- Less epinephrine
__% of released catecholamines are epinephrine, and __% are norepinephrine.
80
20
The conversion of norepinephrine to epinephrine requires which metabolite? What structure provides the metabolite?
- Glucocorticoids
- Cortical capillaries relay the cortisol produced in the zona fasciculata to the adrenal medulla
What are the two different pathways for degradation of the catecholamines?
- MAO (monoamine oxidase)
- COMT (catechol-O-methyltransferase)
The inactivation of norepinephrine or epinephrine by MAO produces which metabolite? What does further degradation by COMT produce?
- DOMA
- VMA
The inactivation of norepinephrine by COMT produces which metabolite?
Metanoradrenaline
The inactivation of epinephrine by COMT produces which metabolite?
Metepinephrine
The inactivation of metanoradrenaline and metepinephrine produce which metabolite?
VMA
Are catecholamines stored or released following synthesis?
They are stored in granules in the cytoplasm, and released upon stimulation
Which metabolites are contained within granules of the catecholamines? What are they related to?
- Met-enkephalin
- Leu-enkephalin
- Related to endorphins
What are functions of enkephalins? (2)
1) Block neurotransmitters (similar to morphine)
2) Act as an endogenous analgesic
What is an example of enkephalins acting as an endogenous analgesic?
Runners overcoming pain and being euphoric
In response to a stressor, what are the two responses of the hypothalamus? (2)
1) Activation of the sympathetic nervous system
2) Activates the adrenal-cortical system by releasing CRH
What is the immediate effect of the activation of the sympathetic nervous system?
Impulses activate glands and smooth muscles
What is the slower effect of the activation of the sympathetic nervous system?
- Activates the adrenal medulla
- Releases norepinephrine and epinephrine from granules into the bloodstream
What is the slowest effect caused by the fight-or-flight response?
- Hypothalamus releases CRH
- Anterior pituitary synthesizes ACTH
- ACTH stimulates the biosynthesis of hormones from the adrenal cortex de novo
What are the four immediate short-term responses to crises? (4)
1) Mobilization of glucose reserves
2) Changes in circulation
3) Increases in heart and respiratory rates
4) Increased energy use by all cells