1. Chemical Signals in Animals
Chapter 45
Chemical Signals in Animals

2. Hormones are chemical signals.
The endocrine system consists of:
Endocrine cells which are hormone-secreting cells and
Endocrine glands which are hormone-secreting organs.
Specific target cells respond to specific hormones.

3. Primary Function of Hormones
Homeostasis
Growth and Development
Reproduction
Energy Metabolism
Behavior

4. Negative Feedback Loop
blood glucose low
stimulates
glucagon from pancreas
glucose release from liver
stimulates
blood glucose high
inhibits

5. Biological Cycles

6. Mechanism of Action on Target Cells
response
hormones
receptor protein
endocrine cell
target cell

7. Mechanism of Action on Target Cells
intracellular receptor
hormones
response
endocrine cell
target cell

8. Tropic vs Nontropic Hormones
Tropic hormones- stimulate the production and secretion of hormones by other endocrine glands; ex. TSH
Nontropic hormones- stimulates cellular growth, metabolism, or other functions; ex. thyroxine

9. Invertebrate nervous systems clearly illustrate endocrine and nervous system interactions
Invertebrates have a wide variety of hormones that are involved in the regulation of homeostasis.

10. An example from a mollusk:
An example from hydra:
One hormone stimulate asexual reproduction.
Another hormone prevents sexual reproduction.
An example from a mollusk:
The hormone that regulates egg laying also inhibits feeding and locomotion.

11. Arthropods have extensive endocrine systems regulating molting in insects and crustaceans.
The regulation of molting in insects.
Ecdysone also promotes the development of adult features.
Neurosecretory cells in the brain produce brain hormone (BH), which regulates the secretion of ecdysone.
Juvenile hormone (JH) promotes the retention of larval characteristics.

13. Different signal-transduction pathways in different cells can lead to different responses to the same signal.

14. Major Endocrine Organs

15. Endocrine Organs of the Brain
pineal gland
hypothalamus
Major Regions of the Brain
pituitary gland

16. Pineal Gland
Produces melatonin (synthesized from seratonin, a derivative of tryptophan)
Secreted directly in CSF to blood
High levels at night make us sleepy; low level during day
Pineal gland is stimulated by darkness and inhibited by light
Function in regulating circadian rhythms (sleep, body temp, appetite)  biological clock

17. Pituitary Gland
hypothalamus
anterior pituitary
posterior pituitary

18. Posterior Pituitary Hypothalamus Posterior Pituitary
Anterior Pituitary

19. Antidiuretic Hormone (ADH)
Hormones of the
Posterior Pituitary
Antidiuretic Hormone (ADH)
Oxytocin (+ feedback)

20. Anterior Pituitary
Hypothalamus
Posterior Pituitary
Anterior Pituitary

21. Hormones of the Anterior Pituitary Growth Hormone (GH) Dwarfism
Gigantism & Acromegaly
Thyroid Stimulating Hormone (TSH)
Adrenocorticotropic Hormone (ACTH)
Gonadotropins (FSH, ICSH, LH)
Prolactin (PRL)
Melanocyte-stimulating Hormone (MSH)

22. Growth Hormone (GH)
Acts on the liver, stimulating it to release several polypeptide hormones.
Stimulates amino acid uptake and protein synthesis in target cells.
Ultimately stimulates cell growth (cell size and number), especially in muscle and bone.
Also stimulates fat breakdown.

23. GH Levels
awake
sleep
strenuous exercise

24. Thyroid-Stimulating Hormone (TSH)
Acts on the thyroid gland, stimulating it to release T3 & T4
These thyroid hormones increase glucose catabolism and body heat production.
Negative feedback mechanism involved in regulating levels.

25. Adrenocorticotropic Hormone (ACTH)
Acts on the adrenal cortex, stimulating it to secrete glucocorticoids (e.g., cortisol).
Glucocorticoids promote the synthesis of glucose from noncarbohydrate sources such as amino acids, and fatty acids
Negative feedback mechanism involved in regulating levels.

26. Thyroid Gland
larynx
thyroid
trachea

27. Thyroid Follicles

28. Thyroid Hormones
Thyroid gland selectively uptakes iodine to produce T3 & T4
Thyroxine (T4)
Triiodothyronine (T3)
Both control metabolic rate and cellular oxidation
Calcitonin (from parafolicular cells)- lowers blood CA ++ levels and causes CA++ reabsorption in bone

29. Thyroid Hormone Regulation

30. Thyroid Disorders Hyperthyroidism (Grave’s, Goiter)
Hypothyroidism (Cretinism, Myxedima)

31. Parathyroid Glands
parathyroid glands
thyroid
esophagus
trachea

32. Parathyroid Hormone (PTH)
PTH release:
stimulates osteoclasts
enhances reabsorption of Ca++ by kidneys
increases absorption of Ca++ by intestinal mucosal cells
Hyperparathyroidism- too much Ca++ drawn out of bone; could be due to tumor
Hypoparathyroidism- most often follow parathyroid gland trauma or after removal of thyroid--- tetany, muscle twitches, convulsions; if untreatedrespiratory paralysis and death

33. PTH Effects

34. Pancreas

35. Pancreas Regulates glucose uptake by cells
Controlled via negative feedback: insulin & glucagon
Blood sugar level: 90 mg/mL

36. Islets of Langerhan

37. Insulin Produced by the  cells of the Islets of Langerhan
Catalyze oxidation of glucose for ATP production
Lowers blood glucose levels by promoting transport of glucose into cells.
Stimulates glucose uptake by the liver and muscle cells.
Stimulates glycogen synthesis in the liver and muscle cells.
Also stimulates amino acid uptake and protein synthesis of muscle tissue

38. Glucagon Produced by the  cells of the Islets of Langerhans
Stimulates change of glycogen to glucose in the liver.
Synthesis of glucose from lactic acid and non carbohydrate molecules such as fatty acids and amino acids
Causes  in blood glucose concentration
hypoglycemic- low blood sugar; deficient in glucagon
   

39. Regulation of Blood Sugar Levels

40. Diabetes Melitus

41. Type I Diabetes. hyposecretion of insulin. insulin dependant
Type I Diabetes hyposecretion of insulin insulin dependant juvenile onset Type II Diabetes late onset (adult) insensitivity of cells to insulin manage by exercise & diet

42. Adrenal Glands
adrenal cortex
adrenal medulla

44. Hormones of the Adrenal Medulla
Adrenalin (epinephrine): converts glycogen to glucose in liver
Noradrenalin (norepinephrine): increases blood pressure
(sympathetic nervous system)
Corticosteroids: glucose levels)

45. Hormones of the Adrenal Cortex
Glucocorticoids- cortisol
Decrease protein synthesis
Increase release and use of fatty acids
Stimulates the liver to produce glucose from non carb’s
Mineralcorticoids- aldosterone
Stimulates cells in kidney to reabsorb Na+ from filtrate
Increases water reabsorption in kidneys
Increases blood pressure
Sex Steroids- small amts (androgens)
Onset of puberty
Sex drive

46. Cushing’s Syndrome
Hypersecretion of cortisone; may be caused by an ACTH releasing tumor in pituitary
Symptoms: trunkal obesity and moon face, emotional instability
Treatment: removal of adrenal gland and hormone replacement

47. Addison’s Disease
Hyposecretion of glucocorticoids and mineral corticoids;
Symptoms- wt loss, low levels of plasma glucose and Na+ levels, high levels of K+
Treatment- corticosteroid replacement therapy

48. Thymus Located anterior to the heart
Produces- thymopoetin and thymosin helps direct maturation and specialization of T-lymphocytes (immunity)

49. Gonads
Ovaries- produce estrogen and progesteroneresponsible for maturation of the reproductive organs and 2ndary sex characteristics in girls at puberty

50. Female Reproductive System

51. Gonads
Testes- produce sperm and testosterone (initiates maturation of male repro organs and 2ndary sex characteristics in boys at puberty)

52. Male Reproductive System