1. Endocrine System
Chapter 30
AP Biology 2012

2. Endocrine System
Consists of cells that produce and release chemical signals called hormones.

3. In the body Endocrine vs. Exocrine Out of the body Endocrine Signals
Exocrine Signals
Secrete substances into the extracellular fluid
Done by endocrine cells or secretory organs called endocrine glands (testes, thyroid)
Example; Signaling molecules
Secrete substances into a duct or internal body cavity that communicates with the external world
Example: saliva, sweat
In the body
Out of the body

4. Hormones
“long distance” endocrine signals that are released into the bloodstream and circulate through the entire body
3 chemical groups
Peptide and protein hormones
Steroid hormones
Amine hormones

5. Peptide and protein hormones
Large
Water soluble – therefore easily transported in the blood
Packaged in vesicles and released by exocytosis
Most hormones are this type
Examples: insulin and growth hormone

6. Steroid Hormones Made from cholesterol (look similar too!)
Lipid soluble
Do not dissolve well in blood plasma so they are bound to carrier proteins for transport in the blood
Found inside target cells
Example: aldosteroids, cortisol, testosterone

8. Amine hormones Small molecules Made from single amino acids
Could be polar or nonpolar depending on the R group of the amino acid it was synthesized from
Example: Tyrosine  epinephrine and thyroxine

10. 30.2 Review
That same hormone could cause very different responses in different types of cells

11. Fight or Flight Response
Rapid physiological response to sudden danger or highly stressful situations
Involves epinephrine (adrenaline) and norepinephrine (noradrenaline)

12. What’s really happening
Epinephrine and norepinephrine bind to a set of adrenergic receptors (G proteins!)
2 categories
Alpha
Beta
Have different affinities for ephinephrine and norepinephrine!

13. Adrenergic Receptors Alpha Beta
It causes blood vessels in the skin to constrict, causing cold hands and feet
Shut off the secretion of digestive enzymes and decrease blood flow through the gut (digesting lunch waits)
In heart cells, it causes a faster and stronger heartbeat (thus pumping more blood)
Cause arterioles in skeletal muscles to enlarge so increased blood flow goes there enabling you to run
Breakdown of glycogen in liver for quick energy!
Breakdown of fats to yield fatty acids – another source of energy!!

16. Hormone receptors are regulated
Downregulation – makes the cells less sensitive to the hormone, causing cells to ignore the excess hormone
Example in diabetes
High levels of insulin downregulates the production of insulin receptors in body

17. Hormone receptors are regulated
upregulation – occurs if hormone secretion is chronically low; cell makes more receptor for that hormone
Example in high blood pressure
People who are regular medication (beta blockers)
Let’s say they go off the medication suddenly, the effects of the receptors are amplified, resulting in heightened anxiety and blood pressure
Explains why dosages for medications are carefully supervised. 

18. 30.3 Nervous system and Endocrine System are linked.
This is done by the Pituitary Gland!

19. Pituitary Gland Endocrine gland
Attached to a region of the brain called the hypothalamus
Has 2 parts
Anterior Pituitary
Posterior Pituitary

20. Anterior Pituitary Releases 4 tropic hormones
Hormones that direct and control the activities of other endocrine glands
TSH – thyroid stimulating hormone
LH – luteinizing hormone
FSH – follicle stimulating hormone
ACTH – adrenocorticotropic hormone
Produces peptide hormones
Prolactin (stimulates milk production)
Growth hormone (promotes growth)
Overproduction causes GIGANTISM
Underproduction causes pituitary dwarfish

22. Posterior Pituitary Releases 2 neurohormones ADH Oxytocin
Increases amount of water conserved by the kidneys
When high, kidneys produce little volume of highly concentrated urine
When low, kidneys produce large volume of dilute urine
Oxytocin
Stimulates uterine contractions during birth
Stimulates flow of milk from mother’s breasts
Promotes pair bonding and trust; “cuddle hormone”

23. Negative Feedback Loop
Corticotropin-releasing hormone (CRH) from hypothalamus stimulates release of adrenocorticotropic hormone (ACTH) from anterior pituitary, which in turn stimulates release of hormone cortisol from adrenal glands.
Once cortisol is released, it circulates thru body, where it directly inhibits further release of both CRH and ACTH
This maintains a constant level of cortisol

24. 30.4
Mammal hormones

25. Thyroid Glands Wrap around trachea (windpipe) Produce two hormones
Thyroxine
Calcitonin

26. Thyroxine Amine hormone made from amino acid tyrosine
Known as T4 – for 4 iodine atoms (T3 is a nearly identical hormone)
Raises metabolic rate
Lipid soluble
Critical during growth and development
Insufficient amount during growth results in physical and mental retardation - cretinism

27. Thyroxine continued…
Levels are controlled by hypothalamus and anterior pituitary
Hypothalamus releases thyrotropin-releasing hormone (TRH) which stimulates the anterior pituitary to release thyroid-stimulating hormone (TSH) which stimulates thyroid gland to produce and release thyroxine
Regulated by a negative feedback loop (like cortisol)

28. Goiters Is an enlarged thyroid gland associated with
Hyperthyroidism (too much thyroxine)
Hypothyroidism (too little thyroxine)

29. Hyperthyroidism
Caused by an antibody binding to and activating TSH receptors, causing uncontrolled production and release of thyroxine
Symptoms:
High metabolic rate
Nervous and jumpy
Hot
Eyes bulge due to buildup of fat behind eye

30. Hypothyroidism
Caused by a lack of circulating thyroxine to turn off TSH production
Caused by lack of iodine in diet
Symptoms:
Low metabolism
Intolerance of cold
Sluggish
Greatly reduced by widespread use of iodized table salt

31. Homeostasis of Calcium is VITAL!!
Why?
trigger neurotransmitter release
Muscle contraction

32. Calcium levels Too little Ca Too much Ca Muscle spasms Seizures
Nervous system to be depressed
Muscles and heart to weaken or stop
99% of Calcium is in bone
1% in cells – so this tiny pool of Ca must be maintained!!

33. 3 Mechanisms the body does to maintain Ca levels
Deposition or resorption of bone
Excretion or retention of calcium by kidneys
Absorption of Calcium from digestive tract
These mechanisms
Are controlled
By calcitonin, calcitriol
And parathyroid hormone
(PTH)

34. Calcitonin Released by thyroid gland
Lowers the concentration of Ca in the blood by regulating bone turnover
Bone is continuously being made (resorption of old bone and synthesizing new bone)
Osteoclasts break down bone and release Ca into blood
Osteoblasts take up Ca and put it in new bone
Decreases activity of osteoclasts
Does not play major role in adults, but does in younger actively growing individuals

35. Calcitriol Made from Vitamin D in the liver and kidneys
Vitamin D is obtained from the sun (UV waves in sunlight convert cholesterol into vitamin D)
Otherwise Vitamin D must be obtained from diet
Hormone that stimulates the cells of the digestive tract to absorb calcium from ingested food

36. Parathyroid Hormone Most important for homeostasis
Glands located to the rear of the thyroid
Synthesis is triggered when blood calcium fall below set point
Increases concentration of calcium 3 ways
Stimulates bone turnover activities of osteoclasts and osteoblasts
Stimulates kidney to reabsorb Calcium
Increases body absorption of calcium from food by activitating the synthesis of calcitriol from vitamin D

38. Adrenal Glands Sit above the kidneys 2 of them
Has a core, called the adrenal medulla, which produces epinephrine and norepinephrine
This release is under control of the nervous system
Both hormones increase heart rate and bp
Cause fat and liver cells to release metabolic fuel

39. Arenal Cortex
Surrounds the adrenal medulla
Produces 2 corticosteroid hormones
Mineralocorticoids
Glucocorticoids
Mineralocorticoids
Increase salt and water balance of the extracellular fluid
Example: aldosterone – stimulates the kidneys to conserve sodium and excrete potassium
Glucocorticoids
Increase blood glucose concentrations and affect macromolecule metabolism
Example: cortisol – critical for mediating long term metabolic responses to stress

40. Gonads Male – testes; Female – Ovaries
Both produce hormones as well as the gametes (sperm and egg)
Male hormones produced are called androgens, Example: testosterone
Female hormones produced are estrogen and progesterone
** Both sexes produce both testosterone and estrogen

41. Sexual Differentiation
Y chromosome – embryonic glands begin producing testosterone in 7th week of development and a peptide hormone called MIS (Mullerian-inhibiting substance)
Testosterone causes testes and ducts develop and MIS induces apoptosis of cells of female reproductive ducts, so they disappear
So androgens are required for male development in humans

44. Puberty
Time of sexual maturation and dramatic physical transformation around age 12-13
Controlled by gonadotropins
Contain two hormones, LH (luteinizing hormone) and FSH (follicle-stimulating hormone)
Under control of a hypothalamic neurohormone called gonadotropin-releasing hormone GnRH
Before puberty, the hypothalamus is producing very low levels of GnRH

45. Puberty Continued…
Initiated by a reduction in the sensitivity of GnRH producing cells by negative feedback
The reduced sensitivity overcomes the negative feedback and so GnRH release increases, stimulating production of gonadotropins and hence production of sex steroid hormones

46. Puberty Continued…
In females, increased levels of LH stimulates the ovaries to increase estrogen production
This initiates development of enlarged breasts, vagina and uterus, broadened hips, increased fat, pubic hair, and menstrual cycle
In males, increased levels of LH stimulates the testes to produce testosterone
This initiates the voice to deepen, facial and body hair, muscle mass increase, testes and penis grow larger