1. 13
The Endocrine System 1

2. The Endocrine System Produces Hormones
Is the ‘other' control system
Endocrine control is slower than nervous system
Endocrine glands: ductless organs that release hormones into blood
Hormones
Chemical messengers secreted by endocrine glands
Circulate in the bloodstream
Act on specific cells in the body (target cells) that have the appropriate hormone receptor

3. Hypothalamus Pituitary gland Thyroid gland Pancreas Adrenal glands
- Anterior lobe
- Posterior lobe
Hypothalamus
Releasing hormones
Inhibiting hormones
Pineal gland
Melatonin
Pituitary gland
Anterior lobe
Adrenocorticotropic hormone (ACTH)
Thyroid-stimulating hormone (TSH)
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Prolactin
Growth hormone
Posterior lobe (stores)
Antidiuretic hormone (ADH)
Oxytocin
Thyroid gland
Thyroid hormones (T3, T4)
Parathyroid glands
Parathyroid hormone (PTH)
Thymus gland
Thymosin
Thymopoietin
Heart
Atrial natriuretic hormone
Stomach
Gastrin
Pancreas
Glucagon
Insulin
Adrenal glands
Cortex
Cortisol
Aldosterone
Medulla
Epinephrine
Norepinephrine
Kidneys
Erythropoietin
Renin
Intestines
Secretin
Cholecystokinin
Ovaries (Female)
• Estrogen
• Progesterone
Testes (Male)
Testosterone
Figure 13.1

4. Types of hormones Steroid hormones Structurally related to cholesterol
Lipid soluble
Receptors inside the cell
Activate specific genes to produce specific proteins
Slow acting (min. to hrs.)
Examples: sex hormones, steroid hormones
Nonsteroid hormones
Made of amino acids, generally a protein
Water soluble
receptors on cell membrane
fast acting (secs. to mins.)
Examples: insulin, thyroid hormones

5. Hormones Participate in Negative Feedback Loops
Many hormones participate to maintain internal homeostasis
Hormone levels regulated by:
negative feedback: deviations detected and counteracted
Hormone regulation mostly by negative feedback loops
example, insulin, thyroid hormones
positive feedback: amplifies original change
Example oxytocin release and child birth

6. Oxytocin is transported by blood to mammary glands.
Figure 13.6
Neuroendocrine cell 3
Release of oxytocin when stimulated.
Hypothalamus
Anterior pituitary 4
Spinal cord
Oxytocin is transported by blood to mammary glands. 2
Sensory and spinal nerves carry impulses to the hypothalamus.
Posterior pituitary
Milk ejected
Figure 13.6 The control of oxytocin secretion by nursing.
Oxytocin 1
Nursing stimulates nerve receptors in nipple. 6

7. The Hypothalamus and the Pituitary Gland
Homeostatic control center of the brain
Produces two hormones of its own (ADH, oxytocin)
controls hormone secretions of the pituitary gland (by inhibiting & releasing hormones
Pituitary gland
“Master” gland
Secretes six different hormones most of which regulate other endocrine organs
Two lobes: posterior and anterior

8. Posterior Pituitary Stores ADH and Oxytocin
Posterior pituitary stores & releases:
Antidiuretic hormone (ADH)
Conserves water in kidneys
Regulates water balance in body
Oxytocin
Causes uterine contractions during labor and milk ejection through a reflex

9. The Anterior Pituitary Produces Six Key Hormones
ACTH
Stimulates adrenal cortex to release its hormones
TSH (thyroid-stimulating hormone)
promoting release of thyroid hormones
FSH and LH
Stimulate growth and function of ovaries and testes
Prolactin
Stimulates milk production
Growth hormone
Major effects on bone, muscle
Most of its growth effects occur during childhood

10. Hypersecretion of growth hormone in childhood Pituitary dwarfism
Figure 13.8
Gigantism
Hypersecretion of growth hormone in childhood
Pituitary dwarfism
Decreased secretion of growth hormone
Figure 13.8 Effect of growth hormone on body growth.
Acromegaly
Excessive growth
hormone secretion in
adults 10

11. The Pancreas Secretes Glucagon & Insulin
Pancreatic hormones are involved in regulating blood glucose levels
Alpha cells: secrete glucagon
Beta cells: secrete insulin
Glucagon
Raises blood glucose by breakdown of glycogen to glucose in liver
Insulin
Lowers blood sugar by promoting uptake of glucose by cells in muscle and adipose tissue
Promotes storage of glycogen, fat & protein formation

12. Disorders of the Endocrine System
Diabetes mellitus
Type 1: insulin-dependent diabetes
5–10% of all cases
Inadequate insulin
Treated with insulin injections
Type 2: non-insulin-dependent diabetes
90–95% of all cases
Insulin resistance

13. The Adrenal Glands consist of the cortex and medulla
Adrenal cortex: outer layer of adrenal gland; produces:
Cortisol- increases blood levels of glucose, fatty acids & glucose
For stress response
Aldosterone- promotes sodium, water retention by the kidney
Adrenal medulla: inner layer of adrenal gland; releases
Epinephrine (adrenaline)
Norepinephrine (noradrenaline)

14. Adrenal medulla Hormones: Neuroendocrine organ Secretion stimulated by
Perceived or
real threat
Brain
Activation of
sympathetic
nerves
Adrenal
medulla
cortex
Norepinephrine
and epinephrine
Target cells
Adrenal medulla
Neuroendocrine organ
Secretion stimulated by
Sympathetic nervous system
Hormones:
Epinephrine & norepinephrine
enhance function of sympathetic nervous system (fight-or-flight response)
Figure 13.11

15. Thyroid located just below larynx in neck
Figure 13.12
Thyroid located just below larynx in neck
Parathyroid glands embedded in back of thyroid
Opening to trachea
Larynx
Thyroid gland
Parathyroids
Trachea
Figure The thyroid and parathyroid glands.
Anterior (front)
Posterior (back)
T4 and T3
Increase the metabolic rate 15

16. Disorders of the Endocrine System
Hypothyroidism: underactive thyroid gland
Children: cretinism
slowed body growth, untreated can cause mental retardation
Adults: lethargy, weight gain, cold intolerance due to low metabolism
Hyperthyroidism: overactive thyroid gland
Increased metabolism, hyperactivity, nervousness, agitation, weight loss, heat intolerance
Graves’ disease: autoimmune form of hyperthyroidism

17. Parathyroid Hormone (PTH) Controls Blood Calcium Levels
Secretion
In response to lowered blood calcium levels
Action
Removes calcium from bones
Increases absorption of calcium from food in the digestive tract
Causes kidneys to retain calcium
Combined effects increase blood calcium levels
Major regulator of blood calcium concentration in adults

18. Table 13.2
Table 13.2 Hormones of endocrine glands other than the hypothalamus and pituitary. 18