Download Endocrine System Tortora, Chapter 18, 13th ed.

Endocrine System
Tortora, Chapter 18, 13th ed.
Ebaa M Alzayadneh, PhD
Integrative Physiology and Pharmacology
Adrenal Glands
• 2 structurally and functionally distinct regions
• Adrenal cortex: secretion stimulated by ACTH and CRH
• Mineralocorticoids affect mineral homeostasis (Na+/K+)
• Glucocorticoids affect glucose homeostasis
• Cortisol or hydrocortisone
• Androgens have masculinizing effects
• Dehydroepiandrosterone (DHEA) more important in females
and prepubertal growth spurt in both genders
• Adrenal medulla
•
•
•
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Modified sympathetic ganglion of autonomic nervous system
Intensifies sympathetic responses
Epinephrine and norepinephrine
Receives preganglionic input by splanchnic nerve
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Adrenal Glands
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Adrenocortical Hormones
•
Mineralocorticoids regulate the concentrations of Na+ and K+
in the blood (affects blood volume/pressure)
– Aldosterone is the major hormone in this group,
stimulates reabsorption of Na+ and secretion (loss) of
K+ in the kidneys. Stimulated by Ang II and high blood
K.
•
Glucocorticoids influence glucose metabolism and the ability
to resists the effects of stress
– Cortisol =hydrocortisone is the major hormone in this
group
•
Weak androgens (masculinizing sex hormones)
DHEA the main source for estrogen for women after menopause
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Functions of the Adrenal Cortex
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Renin-angiotensin-aldosterone system (RAAS)
Aldosterone release is stimulated by
Ang II and hyperkalemia (K+)
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Glucocorticoids (mainly cortisol)
1- Protein breakdown to amino acids that can be used for ATP
production.
2- Lipolysis: the breakdown of triglycerides to release fatty acids.
3- Glucose formation from certain amino acids or lactic acid by
liver (gluconeogenesis)
4- Resistance to stress: by glucose supply and ATP to combat
stress and by sensitizing blood vessels to vasoconstrictive
hormones.
5- Anti-inflammatory effects by inhibiting white blood cells and
suppressing the immune response.
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Glucocorticoids
Although glucocorticoids retard tissue repair, slow wound
healing, and high doses may cause mental disturbances
• glucocorticoids are very useful for the treatment of chronic
inflammatory disorders such as rheumatoid arthritis, and
for transplant rejection prevention.
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Glucocorticoids
•
High levels of circulating cortisol, as seen
with corticosteroid drugs (prednisone), or
hypersecretion by tumors (adrenal cortex,
pituitary gland) is called Cushing’s syndrome
– Manifestations include hyperglycemia,
hypertension, poor wound healing,
osteoporosis, dermatitis, fat
redistribution (spindly arms and
legs, moon face, buffalo hump at
the neck), and truncal obesity
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Glucocorticoids
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In adults, hyposecretion of
glucocorticoids and aldosterone,
usually as a result of an autoimmune
disorder, is called Addison’s disease
– The physiologic effects include
hypoglycemia, Na+ loss,
hyperkalemia (high k+), hypotension,
dehydration, weight loss and anorexia
and muscle weakness.
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Pancreatic Islets
 Both exocrine and endocrine gland
 Roughly 99% of cells produce digestive enzymes (Acini)
 Pancreatic islets or islets of Langerhans rae endocrine
 Alpha or A cells secrete glucagon – raises blood sugar
 Beta or B cells secrete insulin – lowers blood sugar
 Delta or D cells secrete somatostatin – inhibits both insulin
and glucagon ( same as GHIH =somatostatin) and reduces
absorption of nutrients in GI.
 F cells secrete pancreatic polypeptide – inhibits
somatostatin, gallbladder contraction, and secretion of
pancreatic digestive enzymes
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Pancreas
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Pancreatic Islets (Islets of Langerhans)
• Alpha cells secrete glucagon.
• Stimulus is decrease in blood
[glucose].
• Stimulates glycogenolysis and
lipolysis.
• Stimulates conversion of fatty
acids to ketones.
• Beta cells secrete insulin.
• Stimulus is increase in blood
[glucose].
• Promotes entry of glucose into
cells. (liver and muscles)
• Converts glucose to glycogen
and fat.
• Aids entry of amino acids
into
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cells.
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1 Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
Negative
Feedback
Regulation
of Glucagon
and Insulin
and Glucose
GLUCAGON
2 Glucagon acts on
hepatocytes
(liver cells) to:
• convert glycogen
into glucose
(glycogenolysis)
• form glucose from
lactic acid and
certain amino acids
(gluconeogenesis)
3 Glucose released
by hepatocytes
raises blood glucose
level to normal
5 High blood glucose
(hyperglycemia)
stimulates beta cells
to secrete
INSULIN
6 Insulin acts on various
body cells to:
• accelerate facilitated
diffusion of glucose
into cells
• speed conversion of
glucose into glycogen
(glycogenesis)
• increase uptake of
amino acids and increase
protein synthesis
• speed synthesis of fatty
acids (lipogenesis)
• slow glycogenolysis
• slow gluconeogenesis
7 Blood glucose level falls
4 If blood glucose
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8 If blood glucose continues
continues to rise,
to fall, hypoglycemia
hyperglycemia inhibits
release of
Universityinhibits
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release of glucagon
insulin
Glucagon
stimulates
insulin
But insulin
inhibits
glucagon
Pancreatic disorders: Diabetes
• most common endocrine disorder
• Type 1: Insulin dependent ( mostly beta cells destruction)
• Type 2: non insulin dependent (more common) esp with
obese, less responsive to insulin (insulin insensitivity)
Metformin to induce insulin release
• Insulin Shock! hyperinsulinism=Blood glucose fall
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Ovaries and Testes
• Gonads – produce gametes and hormones
• Ovaries produce 2 estrogens (estradiol and estrone) and
progesterone
• With FSH and LH regulate menstrual cycle, maintain pregnancy,
prepare mammary glands for lactation, maintain female
secondary sex characteristics
• Inhibin inhibits FSH
• Relaxin produced during pregnancy
• Testes produce testosterone – regulates sperm production
and maintains male secondary sex characteristics
• Inhibin inhibits FSH
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Growth Factors
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Stress Response
Integration of all to combat
stress
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