Endocrine System

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Mariebs Human Anatomy and Physiology Marieb w
Hoehn

• Chapter 16
• Endocrine System
• Lecture 14
• Part 2 The Pancreas, Stress, and the Stress
  Response

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Endocrine Pancreas
Figures from Holes Human AP, 12th edition, 2010
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Cells of the Pancreatic Islets

• Alpha cells - Glucagon
• Beta cells Insulin, amylin
• Delta cells
• Somatostatin (growth hormone-inhibiting hormone,
  GH-IH)
• Suppresses release of insulin and glucagon
• Slows rates of food absorption
• F cells
• Pancreatic polypeptide (inhibits GB contractions
  exact physiological role is uncertain)

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Insulin
Insulin decreases blood glucose levels by
allowing cells to take up glucose from the
blood Binding enhances glucose uptake Brain,
kidneys, liver, RBCs are insulin
independent Insulin release is also affected by
the ANS
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
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Glucagon
Raises blood glucose levels by - stimulating
breakdown of stored molecules- increasing
release and formation of glucose
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
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Insulin and Glucagon
Figure from Holes Human AP, 12th edition, 2010
Example of a humoral stimulus (glucose) for
hormone secretion
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Pineal Gland
Pinealocytes synthesize melatonin from serotonin
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Melatonin

• regulates circadian rhythms - daily changes in
  physiological processes that follow a regular
  pattern
• Light (eyes) ? retina ? hypothalamus ? reticular
  formation ?
• ? melatonin ? pineal ? sympathetic fibers ?
  spinal cord
• may control onset of puberty (melatonin levels
  decline at puberty)
• helps regulate female reproductive cycle
• may protect CNS against free radicals
  (antioxidant)

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Other Endocrine Glands

• Reproductive Glands
• ovaries secrete estrogen and progesterone
• testes secrete testosterone
• placenta secretes estrogen, progesterone, and
  gonadotropins, e.g., hCG

• Thymus Gland
• secretes thymosins
• promotes development of T-lymphocytes

• Heart
• secretes natriuretic peptides (ANP, BNP)
• - Natri sodium uretic in the urine
• promote loss of water and Na at the kidney
• secreted when atria/ventricles are stretched
• - inhibit renin release
• - inhibit secretion of ADH and aldosterone

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Other Endocrine Glands

• Adipose Tissue
• Leptin
• After eating, adipose tissue absorbs glucose and
  lipids
• Peptide hormone, leptin, is released
• Binds to receptors in hypothalamus (esp. arcuate
  and paraventricular nuclei)
• Alters levels of other substances in brain
• Increased sympathetic activity
• Decreased insulin secretion
• Permissive effect on GnRH (effects on
  reproductive function)
• Sense of satiety and suppression of appetite
• Levels are normal in most obese individuals
  receptors or cellular pathways may be defective
• Resistin
• Reduces insulin sensitivity throughout body
  (insulin antagonist)
• May be one of the missing links between obesity
  and diabetes
• TNF? - in obese people, inhibits glut4 protein
  activates stress hormones

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Stress

• Types of Stress
• physical stress
• psychological (emotional) stress
• (Stress is any condition, physical or emotional,
  that threatens homeostasis)

• Stress Response (General Adaptation Syndrome
  GAS)
• hypothalamus triggers sympathetic impulses to
  various organs
• epinephrine is released
• cortisol is released to promote longer-term
  responses

• Three general phases of the GAS in response to
  stress A R E
• Alarm phase
• Resistance phase
• Exhaustion phase

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Responses to Stress
Exhaustion - ? lipid reserves - ? production of
glucocorticoids - electrolyte imbalance -
damage to vital organs
Figure from Holes Human AP, 12th edition, 2010
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GH Abnormalities
Figure from Holes Human AP, 12th edition, 2010
Growth Hormone Ups and Downs

• Gigantism - hypersecretion of GH in children
• Acromegaly hypersecretion of GH in adults
• Dwarfism hyposecretion of GH in children

Age 9
Age 16
Age 33
Age 52
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Diabetes ( Overflow)

• Diabetes Mellitus (DM) (mellitum honey)
• Hyposecretion or hypoactivity of insulin
• Three Ps of Diabetes Mellitus
• Polyuria (increased urination)
• Polydipsia (increased thirst)
• Polyphagia (increased hunger)
• Hyperglycemia, glycosuria, ketonuria
• Diabetes Insipidus (insipidus tasteless)
• Hyposecretion or hypoactivity of ADH
• Polyuria
• Polydipsia
• Renal Glycosuria
• excretion of glucose in the urine in detectable
  amounts
• normal blood glucose concentrations or absence of
  hyperglycemia

Oxaloacetic acid
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Hormone Summary Table I Pituitary Hormones
Tissue Tissue
Name Origin Destination Action on Target Tissue Control of Release1
FOLLICLE STIMULATING HORMONE (FSH) anterior pituitary males seminiferous tubules of testes females ovarian follicle males sperm production females follicle/ovum maturation Gonadotropin Releasing Hormone (GnRH)
LUETINIZING HORMONE (LH) anterior pituitary In males interstitial cells in testes in females mature ovarian follicle males testosterone secretion females ovulation Gonadotropin Releasing Hormone (GnRH)
THYROID STIMULATING HORMONE (TSH) anterior pituitary thyroid secrete hormones Thyrotropin Releasing Hormone (TRH)
GROWTH HORMONE (GH) anterior pituitary bone, muscle, fat growth of tissues Growth Hormone Rleasing Hormone (GHRH)
ADRENOCORTICO-TROPIC HORMONE (ACTH) anterior pituitary adrenal cortex secrete adrenal hormones Corticotropin Releasing Hormone (CRH)
PROLACTIN (PRL) anterior pituitary mammary glands produce milk Prolactin Releasing Hormone (PRH)
ANTI-DIURETIC HORMONE (ADH) (VASOPRESSIN) posterior pituitary Collecting ducts of kidneys reabsorption of water increases blood pressure increase in osmolarity of plasma or a decrease in blood volume
OXYTOCIN (OT) posterior pituitary uterine smooth muscle breast contraction during labor milk letdown Stretching of uterus infant suckling
Se(x)
T
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A
P
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Hormone Summary Table II
Tissue Tissue
Name Origin Destination Action on Target Tissue Control of Release
TRIIODOTHYRONINE (T3) THYROXINE (T4) Thyroid (follicular cells) all cells increases rate of metabolism (BMR) Thyroid Stimulating Hormone (TSH)
CALCITONIN Thyroid (C cells) Intestine, bone, kidney Decreases plasma Ca2 (? intestinal absorp of Ca ? action of osteoclasts ? excretion of Ca by kidney ? plasma Ca2
PARATHYROID HORMONE (PTH) Parathyroids Intestine, bone, kidney Increases plasma Ca2 (? intestinal absorp of Ca ? action of osteoclasts ? excretion of Ca by kidney ? plasma Ca2
EPINEPHRINE/ NOREPINEPHRINE(Catecholamines) Adrenal Medulla cardiac muscle, arteriole and bronchiole smooth muscle, diaphragm, etc increases heart rate and blood pressure... (fight or flight) Sympathetic Nervous System
ALDOSTERONE (Mineralocorticoids) Adrenal Cortex Kidneys sweat glands salivary glands pancreas reabsorption of water and Na (increases blood pressure) and excretion of K (mineralocorticoid) Angiotensin II ? plasma Na ? plasma K
CORTISOL(Glucocorticoids) Adrenal Cortex all cells Diabetogenic anti-inflammatory(glucocorticoid) ACTH
INSULIN ß-cells of Pancreatic Islets all cells, liver and skeletal muscle pushes glucose into cells from blood, glycogen formation (decreases blood glucose) ? plasma glucose SNS
GLUCAGON a-cells of pancreatic Islets liver and skeletal muscle breakdown of glycogen (increase in blood glucose) ? plasma glucose
TESTOSTERONE Testes secondary sex organs development and maintenance LH
ESTROGEN Ovaries secondary sex organs development at puberty and maintenance throughout life LH
NATRIURETIC PEPTIDES atria and ventricles of heart adrenal cortex, kidneys increased excretion of sodium and water from kidneys, ? blood volume, ? blood pressure Stretching of atria and ventricles
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Review

• Reaction to stress occurs in three stages
• Short term
• Alarm or fight or flight
• Reactions similar to sympathetic stimulation
• Mediated by hormones of the adrenal medulla
• Long term
• Resistance
• Long-term raising of blood glucose
• Mediated by hormones of the adrenal cortex
• Exhaustion
• Failure of compensatory mechanisms

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Mid-term Checkup
Based on the three (3) grades you have received
so far, you should do a mid-term checkup. To find
your average so far, total the three grades
youve received and divide by 300 (the total
amount of points possible so far for the course).
Example (83 67 90) ? 300 0.80
(80) Dropping the low grade (8390) ? 200
0.87 (87) To figure out what you need to
AVERAGE for the next lecture or lab exam and the
final COMBINED to get a particular grade
( (Grade you want) ? 100 x 600 ) - Total pts.
so far
Average grade needed

300 (if no grade dropped) or 400 (if low grade
dropped)