Adrenal Glands Flashcards
What are the two regions of the adrenal gland?
Cortex (outer) and Medulla (inner)
What is the function of the cortex?
Responds to long-term stress
What hormones does the cortex secrete?
Cortisol
Aldosterone
Androgens
What is the function of the medulla?
Responds to short-term stress
What hormones does the medulla secrete?
Catecholamines (epi/nor)
Enkephalins and other peptides
What are examples of long term stress responses?
Retention of water/salt by the kidneys
Increased BP/blood volume
Increased blood glucose/proteolysis/lipolysis
Suppress immune response
Maintain/promote anabolic growth
What are examples of short term stress responses?
Increase HR/BP
Bronchodilation
Glycogenolysis + increase in plasma glucose
Blood diverted from GI to heart, CNS, + muscles
Increase metabolism
The adrenal medulla is a functional “____________” of the _____________ nervous system
“extension” ; sympathetic
Short term stress signaling starts in the _____________, which then signals the ______________, which sends action potentials to the adrenal _____________ via the sympathetic division of the _______________ nervous system
Hypothalamus
Brainstem/Spinal Cord
Medulla
Autonomic
What are catecholamines?
Epinephrine (adrenaline)
Norepinephrine (noradrenaline)
What are the percentages of catecholamines released by the adrenal medulla?
80% Epinephrine
20% Norepinephrine
What responses do enkephalins stimulate?
Analgesic
What stimulates the adrenal medulla and what is the response?
Stressor or threats to survival
(think adrenaline related)
Fight or flight response
What happens in a fight or flight response?
HR/BP/TPR increase
Ventilation increases
Metabolism increases
Glycogenolysis/lipolysis
CNS “alertness” increases
GI function decreases
What tissues does the adrenal medulla target?
Heart
Blood vessels
Bronchioles
Liver
Adipose
Intestines
Kidneys
CNS
How do sympathetic stimuli affect the kidneys?
Decrease GFR and RBF (think long term stress response)
How are catecholamines removed from circulation?
Metabolized by enzymes in the kidneys and excreted via kidneys
What are the layers of the adrenal cortex?
Zona Glomerulosa (outer)
Zona Fasiculata (middle)
Zona Reticularis (inner)
What does the zona glomerulosa contain?
Enzymes that synthesize aldosterone
What does the zona fasiculata contain?
Enzymes that synthesize cortisol
What does the zona reticularis contain?
Enzymes that synthesize adrenal androgens
What is the precursor/stimuli to adrenal cortex hormones?
Cholesterol
______ binds to receptors and delivers cholesterol into the adrenal ___________
LDL
Cortex
_______ stimulates the adrenal cortex to convert cholesterol into ______________
ACTH
Pregnenolone
What is pregnenolone used for?
To synthesize aldosterone, cortisol, and adrenal androgens
What can cause adrenal pathologies?
Enzyme deficiencies
What does cortisol do?
Enhances enzyme activity to allow metabolism to occur more efficiently
“Gas pedal, not the ignition”
What can excess cortisol cause?
Suppressive effects
(Think negative feedback loop)
What does cortisol influence?
Plasma glucose
Immune response
CV function
Kidney function
CNS function
Fetal growth and surfactant
What is the target tissue of cortisol?
Heart
Blood vessels
Kidneys
Liver
Adipose
Muscles
Immune system
CNS
CT (bone, ligaments, tendons)
Cortisol effect on heart and blood vessels
Vasoconstriction
Increase HR and stroke volume
Cortisol effect on kidneys
Increase GFR and RBF
Increase salt/water retention
Increase potassium excretion
How does cortisol affect the immune system?
Enhance anti-inflammatory response
How does excess cortisol affect the immune system?
Impairs immune system
Reduces both cellular and humoral immunity
(Poor wound healing/immune defenses)
How does cortisol affect the CNS?
Increases excitability
Increases attention and memory formation but may impair recall
Alters mood and perception
How does excess cortisol affect the CNS?
Can cause neuronal death and impair CNS function (depression/dementia)
How does cortisol effect bone? What can excess cortisol cause?
Stimulates osteoclasts/calcium resorption
Excess can cause osteoporosis
How does cortisol affect muscle? What can excess cortisol cause?
Stimulate proteolysis
Excess can cause muscle wasting/weakness and loss of lean body mass
How does cortisol affect tendons/ligaments/CT? What can excess cortisol cause?
Inhibits fibroblasts/collagen production (weakens CT)
Excess can cause ligament/tendon failure
What stimulates cortisol?
Circadian rhythm
Stress
When is most cortisol released and when does it peak?
Released between midnight and 8am, peaks right before waking
What inhibits cortisol?
Negative feedback loops
Elevated levels of cortisol inhibit ACTH and CRH (which stimulate cortisol)
What is the function of aldosterone?
Influence renal regulation of salt, water, and potassium
What tissues does aldosterone target?
Kidneys and blood vessels
How does aldosterone affect the kidneys?
Increases Na reabsorption promoting water resorption
Increases potassium excretion
What is the function result of aldosterone’s affect on the kidneys?
Increase BP/BV
Decrease plasma potassium
Increase pH
How does potassium affect pH?
Potassium excretion is coupled with hydrogen excretion in the kidneys
The loss of hydrogen promotes alkalosis in the plasma
What stimulates aldosterone?
Angiotensin II
Hyperkalemia
What inhibits aldosterone?
Negative feedback loops
Atrial natriuretic peptide (ANP)
Beta Blockers
What are androgens responsible for?
Development and maintenance of male characteristics
Role in reproductive activity
Precursor to estrogen
What are examples of active androgens and what is their MOA?
Dihydrotestosterone (DHT)
Testosterone (precursor to DHT)
MOA: bind to androgen receptors and exert androgenic effects on target tissue
What are examples of inactive androgens and what is their MOA?
DHEAS/DHEA
Androstenedione
MOA: Converted to active androgen (testosterone) which does on to exert androgenic effects
The adrenal glands release which androgens?
Inactive
(DHEAs/DHEA and androstenedione)
What other organs secrete androgens?
Gonads (testes and ovaries)
What is the most abundant androgen?
DHEAS/DHEA
Testosterone is synthesized in which organs?
Mostly in gonads but small amount in peripheral tissues
What is the difference between males and females regarding testosterone production and release?
Males’ testes release testosterone into bloodstream/circulation
Females’ ovaries convert most testosterone into estrogen w/ small amount of testosterone released into circulation
Where are inactive androgens converted into testosterone?
Peripheral tissues
The conversion of testosterone into DHT requires?
5 alpha reductase
DHT is the most __________ androgen
Potent
What is the approximate ratio of DHT:Testosterone in the body?
1:10
What is the difference between females and males in regards to DHT synthesis?
Females have less 5 alpha reductase than males which results in less DHT synthesis
Androgens and pre-puberty
Play important role in development of axillary hair, pubic hair, muscle mass, sebaceous glands (acne)
Adrenal excess during pre-puberty in males causes?
Significant androgenic effects
Isosexual precocious puberty
What is isosexual precocious puberty?
Early development of male secondary sexual characteristics before the age of 9
Adrenal excess during pre-puberty in females causes?
Significant androgenic effects
Heterosexual precocious puberty
What is heterosexual precocious puberty?
Early development of male secondary sexual characteristics before the age of 8
Androgens and post-puberty in males
Limited role in maintenance of male sex characteristics
Testosterone plays the dominant role instead
Androgens and post-puberty in females
Significant role in maintenance of axillary/pubic hair growth, muscle mass, libido
Since ovaries produce such a small amount of testosterone
What is the difference in having adrenal excess post-puberty in males vs. females?
Adrenal excess will have no/minimal androgenic effect in males but a significant androgenic effect in females
Excess androgens post-puberty in females
Development of male sexual characteristics
cystic acne, male type baldness, infertility
