1. Endocrine System

2. Homeostasis Maintaining internal balance in the body Regulation
Organisms must keep internal conditions stable even if environment changes
Regulation
Nervous system
Nerve signals control body functions
Endocrine system
Hormones
Chemical signals control body functions

3. Endocrine System
includes the organs of the body that secrete hormones directly into body fluids such as blood
Regulates chemical reaction in cells and therefore control functions of the organs, tissues, and other cells

4. Hormones Endocrine glands Hormones Ductless Release hormones
Into bloodstream to be carried to target tissues
Hormones
Chemicals secreted by a cell that affect the functions of other cells
Growth hormones
Sex hormones
Response hormones
Metabolism hormones
And more…

5. Negative & Positive Feedback Loops
Control Hormone Levels
Negative feedback loop
Hormone release stops in response to decrease in stimulus
Stimulus (eating) raises blood glucose levels
Pancreas releases insulin in response to elevated blood glucose
Blood glucose decreases as it is used by the body or stored in the liver
Insulin release stops as blood glucose levels normalize

7. Negative & Positive Feedback Loops
As long as stimulus is present, action of hormone continues
Infant nursing at mother’s breast stimulates hypothalamus stimulates posterior pituitary
Oxytocin released stimulates milk production & ejection from mammary glands
Milk release continues as long as infant continues to nurse

8. Endocrine Glands
Pineal gland & thymus gland are ductless but little is know about their endocrine function
Pineal gland
Secretes melatonin
Supports body’s biological clock
Thought to induce sleep
Thymus gland
Produces thymosin
Important in the development of immune responses in newborns

9. Endocrine Glands Thyroid Gland
Composed of right & left lobe on either side of trachea
Major hormones
Thyroid hormone
Stimulates protein synthesis & increase metabolism
Calcitonin
Lowers blood calcium levels

10. Endocrine Glands Parathyroid Glands
Four small oval bodes located on the dorsal aspect of the thyroid gland
Major hormone
Parathyroid hormone (PTH)
Agonist to calcitonin by raising blood calcium levels

11. Endocrine Glands Adrenal Glands Glands on top of kidneys
Adrenal Cortex (outer)
Increases blood glucose
Increases salt reabsorption
Sexual characteristics
Adrenal medulla (inner)
Epinephrine (adrenaline) & Norepinephrine (noradrenaline)
Sympathomimetic
Mimic the actions of the sympathetic nervous system

12. Endocrine Glands Pancreas Located near & partly behind the stomach
islets of Langerhans
Hormone-producing cells
Produce insulin
Lowers blood sugar
Produce glucagon
Raises blood sugar

13. Endocrine Glands Pituitary Gland
(hypophysis) “Master Gland”- controls several other endocrine glands
Pea-sized gland located at the base of the brain
Consists of an anterior lobe (adenohypophysis) & posterior lobe (neurohypophysis)

16. Endocrine Glands Ovaries Testes
Produce the ovum & hormones responsible for female sex characteristic & regulation of the menstrual cycle
Estrogen
Female sex characteristics
Progesterone
Maintains pregnancy
Testes
Produce the spermatozoa & testosterone
Testosterone is an androgen
Stimulates secondary sex characteristics

18. Common Diseases and Disorders
Disease/Disorder
Description
Acromegaly
Too much growth hormone produced in adults; enlargement of bones and thickened skin
Addison’s disease
Adrenal gland fails to produce enough corticosteroids
Cretinism
Extreme form of hypothyroidism present prior to or soon after birth
Cushing’s disease
Hypercortisolism; over-production of cortisol
Diabetes insipidus
Kidneys fail to reabsorb water, resulting in excessive urination; hyposecretion of ADH

19. Acromegaly
Cushing’s disease

20. Common Diseases and Disorders (cont.)
Disease/Disorder
Description
Diabetes mellitus
Type I
Type II
Gestational
Chronic disease characterized by elevated blood glucose levels
Insulin-dependent diabetes mellitus; usually develops in childhood
Noninsulin-dependent diabetes mellitus; primarily in adults but increased incidence in teens
Occurs during pregnancy; usually temporary
Dwarfism
Too little growth hormone (somatotropin) produced during childhood

21. Common Diseases and Disorders (cont.)
Disease/Disorder
Description
Gigantism
Too much growth hormone produced during childhood
Goiter
Enlargement of thyroid gland, causing swelling in neck; deficiency of iodine in diet
Grave’s disease
Hyperthyroidism; antibodies attach to thyroid gland, causing it to produce too much thyroid hormone
Myxedema
Thyroid gland produces inadequate amounts of thyroid hormone; common in females over 50

22. Gigantism
Goiter