1. The Endocrine System
chapter 16

2. Endocrine System: Definitions
Endocrine – releasing substances into blood
Endo = within or internal
Contrast with Exocrine – releasing substances outside the body
Hormone – a chemical that influences the function of a remote tissue (acts at a distance)

3. Endocrine System: Overview
9 glands in total
Endocrine glands
pituitary
thyroid
parathyroid
adrenal
pineal
thymus
Mixed glands
produce both hormones and exocrine products
pancreas
gonads
produce hormones and has neural functions
hypothalamus

5. Pineal gland
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
(on dorsal aspect
of thyroid gland)
Thymus gland
Adrenal glands
Pancreas
Ovary
(female)
Testis
(male)

6. Hormones How they work Regulate the metabolic function of other cells
Have lag times ranging from seconds to hours
Tend to have prolonged effects
Are classified as amino acid-based hormones, or steroids

7. 2 M ain Types of Hormones Amino acid based Steroids Water-soluble
Do not enter the cell
e.g., insulin, norepinepherine, epinephrine
Steroids
Lipid soluble
Act intracellularly and activate genes
e.g., testosterone, estrogen, cortisol

8. Mechanism of Hormone Action
Act on receptors in the plasma membrane
Amino acid–based hormones
e.g., epinephrine- binds to smooth muscle cells in blood vessels - causing contraction
Direct gene activation
Steroid hormones, thyroid hormones
e.g., growth hormone - stimulates cells to increase in size and divide
The precise response depends on the type of the target cell
The ONLY tissue to respond is the Target Tissue (may be very specific (1) tissue, or multiple tissues)

9. Hormone Blood Concentrations
Concentrations of circulating hormone reflect:
Rate of release
Speed of inactivation and removal from the body
Hormones are removed from the blood by:
Degrading enzymes
The kidneys
Liver enzyme systems

10. Hypothalamic Control
Hypothalamus “releasing hormones” and “inhibiting hormones” tells of central control by brain
GHRH (growth hormone RH) and GHIH (growth hormone IH) control GH from Ant. Pituitary
PRH (prolactin RH) and PIH control PL from Ant. Pit.
TRH  thyrotropin RH – release of TSH from Ant. Pit.
CRH  corticotropin releasing hormone – release of hormones from adrenal cortex  Stress
GnRH  gonadotropin RH – release of gonadal hormones from Ant. Pit.  LH and FSH

11. Pituitary (Hypophysis)
Pituitary gland
two-lobes
secretes 9 major hormones
Connected to the hypothamus by
Posterior Lobe
Neurohypophysis – neural tissue) and the infundibulum
Receives, stores, and releases hormones from the hypothalamus
Anterior Lobe
Adenohypophysis – made up of glandular tissue
Synthesizes and secretes a number of hormones

12. Pituitary (Hypophysis)
Figure 16.6

13. Anterior Pituitary Hormones
regulate other endocrine glands
GH – growth hormone
TSH – thyroid stimulating hormone
ACTH – adrenocorticotrophic hormone
FSH – follicle stimulating hormone
LH – luteinizing hormone
PRL - prolactin
(latter 3 are called gonadotropins)

14. Growth Hormone (GH) Underproduction in children  dwarfism
Overproduction in children  gigantism
Overproduction in adults  acromegaly

15. Posterior Pituitary Hormones
stores antidiuretic hormone (ADH) and oxytocin
ADH and oxytocin are synthesized in the hypothalamus
Oxytocin stimulates smooth muscle contraction in breasts and uterus
“cuddle hormone”
Both are amino acid based
Receptor location?

16. Pancreas both exocrine and endocrine cells,
Acinar cells  enzyme-rich juice used for digestion (exocrine product)
Pancreatic islets (islets of Langerhans) produce hormones (endocrine products)
The islets contain two major cell types:
Alpha () cells that produce glucagon
Beta () cells that produce insulin
Class 05

17. Regulation of Blood Glucose Levels
hyperglycemic
 glucagon  glucose uptake
hypoglycemic
 insulin  glucose release
Figure 16.18

18. Diabetes Mellitus (DM)
Results from hyposecretion or hypoactivity of insulin
The three cardinal signs of DM are:
Polyuria – huge urine output
Polydipsia – excessive thirst
Polyphagia – excessive hunger and food consumption

19. Thyroid Gland thyroid hormone calcitonin metabolism, BP, growth
T3 (10x) T4
calcitonin
response to rising blood calcium – inhibit gut absorption and kidney reabsorption of Ca++

20. Thyroid Disorders Hypothyroidism
Thyroid gland defect, inadequate TSH, lack of iodine
Low metabolic rate, feeling chilled
Goiter formation ( if cause is lack of iodine)
Cretinism = Hypothyroidism in infants
Stunted growth, low mentality
can be prevented by hormone replacement therapy

21. Grave’s Disease Hyperthyroidism
Autoimmune disease- body attacks and stimulates the thyroid cells - increased thyroid hormone
High BMR, Weight loss, Increased heart rate, Protrusion of the eyeballs, goiter
Treated by surgical removal of the thyroid gland

22. Parathyroid Glands PTH (parathormone)
response to falling calcium in blood – promotes gut absorption and kidney reabsorption of Ca++
Question:
what two hormones regulate calcium in blood?

23. Adrenal (Suprarenal) Glands
Adrenal glands
cope with stressful events
Structurally and functionally, they are two glands in one
Adrenal cortex – glandular tissue
Adrenal medulla – neural tissue that acts as part of the SNS

24. Adrenal Cortex Hormones
Aldosterone - dehydration
causes kidney to reabsorb Na+  reabsorb water
stimulated by angiotensin (remember Renin)
Cortisol - stress
increases blood glucose levels & reduces edema of tissues
prolonged high levels  changes in neural and circulatory function, depressed bone/cartilage growth, suppressed immune response

25. Adrenal Cortex Hormones
Androgens (masculinizing hormones)
most important is testosterone
the onset of puberty
secondary sex characteristics
sex drive in females
testosterone can be converted to estrogen in females after menopause

26. Disorder Addison’s disease Cushings disease
Hyposecretion of the adrenal cortex
Deficiency in cortisol and aldosterone
Low BP
Hypoglycemia
Cushings disease
Hypersecretion of adrenal cortex (tumor of the adrenal cortex)
Hyperglycemia
“buffalo hump” (fat on upper back)

27. Adrenal Medulla secretes the catecholamines
epinephrine
norepinephrine
“Fight or Flight” secretion causes:
blood glucose levels to rise
blood vessels to constrict
faster heart rate
blood diversion to brain, heart, and skeletal muscle

28. Adrenal Medulla
Epinephrine is the more potent stimulator of the heart and metabolic activities
Norepinephrine is more influential on peripheral vasoconstriction and blood pressure

29. Stress and the Adrenal Gland
Figure 16.16