1. Jasmine Han, Inam Sakinah, & Kirstin Nygaard
The Endocrine System:
the human body system that is responsible for our raging teenage hormones and homeostasis
Jasmine Han, Inam Sakinah, & Kirstin Nygaard

2. The Endocrine System: Overview
The overall goal of this body system is to maintain homeostasis.
Hormones are chemicals released by one or more cells that affects cells in other parts of the organism. They assist by carrying messages through the bloodstream to target cells throughout the bloodstream.
These hormones have different jobs, such as: growth & development, reproduction; they also regulate things like metabolism, biological clock, extracellular fluids , and glandular secretion. 
Although this system is slower than the nervous system's communication systems, hormones have a powerful influence on the body.

3. Where is the Endocrine System?
The Pituitary Gland is considered the MASTER GLAND since it controls the other glands.

4. GLANDS & Hormones 

5. Pineal Gland Stimulated by nerves in the eyes
Produces melatonin at night
Melatonin – involved in circadian rhythm. Levels rise at night (makes you sleepy) and drop in the morning (wakes you up)
Affects reproductive functions in the gonads
Affects thyroid and adrenal cortex functions

6. Hypothalamic-pituitary axis
Forms two distinct systems – the hypothalamus and the pituitary gland
The axis is the functional interaction between these two systems

7. Hypothalamus
Maintains the body’s internal environment by regulating the autonomic nervous system, endocrine system, body temperature, water balance, and appetite
The neurons in the hypothalamus influence the two sections of the pituitary gland
Neurosecretory cells produce and release hormones into the bloodstream

8. Hypothalamus hormones
Growth-hormone-releasing hormone
Stimulates the synthesis and release of growth hormone (GH)
Corticotropin-releasing hormone (CRH)
Secreted in response to stress
Thyroid-releasing hormone
Stimulates the release of thyrotropin (TSH)
Gonadotropin-releasing hormone (GnRH)
Stimulates the release of  Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH)
Antidiuretic hormone (ADH)
Oxytocin

9. Pituitary Gland Located below the hypothalamus
Secretes growth hormones
1930 experiment
Biologists removed the pituitary gland from rats
The rats stopped growing, couldn’t maintain a normal body temperature, and their genitals, thyroid glands, and adrenal cortexes shrunk
Suggests that the pituitary gland secretes hormones that regulates the production of other hormones
Two types – posterior and anterior

10. Posterior pituitary Extension of the brain
Stores antidiuretic hormones (ADH) and oxytocin which are produced from the neurosecretory cells in the hypothalamus

11. Antidiuretic Hormone
Released when someone is dehydrated (prevents you from peeing)
Helps the kidneys reabsorb water
Triggers the insertion of aquaporins into the apical membrane -> cells become more permeable to water -> large amounts of water are reabsorbed
Increases permeability to urea -> increases osmolarity of surrounding fluid -> water loss from the filtrate
Defective forms of ADH produces an abundance of urine. May suffer from diabetes insipidus
Negative feedback –Maintains stable conditions and homeostasis
The effect of the hormone causes the hormone to not be released

12. Oxytocin
Causes uterine contractions during childbirth and milk release when a baby is being nursed
More contractions -> more nerve impulses to the hypothalamus -> release of oxytocin
Positive feedback – the stimulus brings about an effect
Stimulates affiliative behaviors in both sexes

14. Anterior pituitary
Develops from cells in an embryo’s mouth and throat lining (not directly connected to the hypothalamus)
Neurosecretory cells secrete stimulatory or inhibitory signals into blood vessels. The signals are carried to the anterior pituitary -> the anterior pituitary alters the secretion of hormones that enter the bloodstream and act on target tissues or glands
Hormones produced stimulate the production of other hormones

15. Anterior Pituitary Hormones Affecting Other Glands
Adrenocorticotropic hormone (ACTH)
When injected into humans, cortisol levels in their blood rises
Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH)
Involved in producing sex hormones and regulating the menstrual cycle
Thyroid-stimulating hormone (TSH)
Triggers the production of thyroid hormones
Gonadotropic hormones
Stimulates the testes and ovaries to produce gametes and sex hormones

16. Anterior Pituitary Hormones Not Affecting Other Glands
Growth hormone (GH)
Promotes lengthening of the long bones in children and muscle growth, tissue repair, and lactation in adults
Prolactin
Stimulates mammary gland growth and milk production
Melanocyte-stimulating hormone (MSH)
Skin-color changes in fish, amphibians, and reptiles

18. Parathyroid Glands Embedded in the thyroid gland
Can be as small as a grain of rice or as big as a pea
Control how much calcium there is in our bones and blood
Releases the parathyroid hormone (PTH) to increase the calcium levels in the blood

19. Thyroid Gland Located in the neck
Releases thyroid hormone and calcitonin
Thyroid hormone – increases metabolic rate
Calcitonin – lowers blood calcium
Two distinct lobes
Follicles filled with triiodothyronine (T3) and thyroxine (T4)

20. T3 and T4 Increases cellular metabolism
In mammals, T3 has a stronger effect than T4
In mammals, T4 is converted to T3 in the liver
T4 increases metabolic rate and heart rate. It also promotes growth
In amphibians, T3 is responsible for most of the changes that occur in metamorphosis

22. Adrenal Glands
Two small glands that sit on top of the kidneys. The cortex (outer portion) secretes steroid hormones. The medulla (inner portion) secretes epinephrine and norepinephrine.

23. Catecholamines
Small compounds derived from tyrosine (an amino acid) that are used as hormones or neurotransmitters
Includes epinephrine, norepinephrine, and dopamine

24. Epinephrine (Adrenaline)
Released when the adrenal medulla is stimulated by action potentials from your sympathetic nerves
Released during the fight-or-flight response (short term response to stress)
When humans are injected with epinephrine, there is an increase in the concentration of free fatty acids and glucose in the blood, pulse rate, blood pressure, and oxygen consumption by the brain and they feel anxiety and excitement
Redirects blood away from the skin and digestive system and toward the heart, muscles, and brain
Relaxes smooth muscles -> opens blood vessels -> increases blood delivery to target tissues

25. Norepinephrine Stress hormone Produced in the adrenal medulla
Released directly onto target cells
Affects the brain (parts where attention and responding actions are controlled)
Fight-or-flight
Increases heart rate -> triggers the release of glucose -> more blood to skeletal muscles

27. Pancreas Thin organ that is located in the abdomen
Two types of tissue – exocrine and endocrine
Exocrine tissue produces digestive juices which are sent to the small intestines
Endocrine tissue (pancreatic islets) produces and secrete insulin and glucagon directly into the blood
Pancreatic islets – groups of pancreatic cells (3 types)
Alpha cells secrete glucagon
Beta cells secrete insulin
Delta cells secrete somatostatin
Insulin – secreted when there is too much glucose in the blood. Insulin tells the liver to take the extra glucose out of circulation. Regulates blood sugar
Glucagon – secreted in response to low blood sugar. Forces cells to produce or release glucose. Regulates blood sugar
Somatostatin – inhibits the release of glucagon and insulin. Helps with carb metabolism

28. Glands Endocrine Exocrine
Secrete products into the bloodstream (instead of ducts) -> delivered to the rest of the body
Only target cells can respond to certain hormones
Exocrine
Secretes substances through a duct into a space

31. Gonads
Primary function is to produce gametes (a mature haploid male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote)
Gender specific
Females have ovaries
Males have testes

32. Ovaries
Located on both sides of the uterus below the openings of the fallopian tubes
Secrete sex hormones
Produce estrogen and progesterone
Estrogen – helps maintain sexual organs and secondary sex characteristics. Necessary for egg maturation
Progesterone – secreted after ovulation. Causes the uterine lining to thicken

33. Testes Secrete sex hormones Located outside of the body in the scrotum
Produce androgens (e.g. testosterone)
Testosterone – stimulates sperm production and reproductive behaviors
Causes the development of male characteristics such as facial hair, deepening of the voice, and the growth spurt that takes place during puberty

34. Communication in Endocrine System

35. Secreted Signaling Molecules
Stimulate responses by binding to receptors on target cells
Endocrine Cells secrete hormones into extracellular fluids
Reach target cells through bloodstream (hemolymph)
Can exist within organs from organ systems or in endocrine glands (ductless organs)
Travel to all parts of the body
Local Regulators act over short distances and reach target cells by diffusion
Paracrine signaling – target cells are close to secreting cell
Autocrine signaling – regulators act on secreting cell
Receptors = protein
Cells with receptors = target cells because receptors trigger response
Different pathways
Contrast with exocrine glands – ducts carry substances on body surfaces (within and out of)
Paracrine sometimes also acts on distant cells
Hormones can be local regulators according to AP (Some only apply hormones in 1st category)

36. Secreted Signaling Molecules
Neurohormones are secreted by neurosecretory cells through diffusion from nerve cells into bloodstream
Called neuroendocrine signaling
Example: ADH involved in water balance and kidney function
Pheromones NOT classified as hormones
Communication that occurs in external environment between other animals
Link to nervous system detecting signals

37. Secreted Signaling Molecules
Hormones classified into 4 categories or chemical groups
Peptide and Proteins (Polypeptide)
Derived from long protein chains
Steroids
Derived from cholesterol
Amines
Derived from single amino acid
Eicosanoids
Derived from fatty acids
Divided based on structure and synthesis process
Thus, vary in solubility and therefore, cellular response pathways
Because of this variation in structure, hormones also vary in solubility in water and lipids. Polypeptides and some amines Amines (polar) are not lipid – soluble and thus, cannot pass through plasma membranes while steriods and eicosanoids and some amines can. This leads to differences in receptor locations. Surface vs. inside.

38. Cellular Response Pathways
Refers to how binding of hormones to certain receptors causes changes in cytoplasmic molecules , amplifies signaling, and can sometimes alter gene transcription

39. Water-Soluble Hormones
Water-Soluble Hormones secreted by exocytosis
Bind to receptors on cell surface
Travel solo in blood stream
Pathway
Binding stimulates cellular response through signal transduction
Converts extracellular chemical signal to an intracellular response
Occurs through a series of molecular interactions
Changes in pathway can alter cellular response reflecting many diseases

40. Example
Triggers cascade of molecular interactions resulting in synthesis of cyclic AMP (second messenger)
Stress triggers Adrenal gland to secrete epinephrine
Epinephrine arrives at liver cell and binds to G protein-coupled receptor
cAMP activates protein kinase A
kinase A activates an enzyme that stimulates glycogen breakdown and an enzyme that inhibits glycogen synthesis
Process initiated with G-protein
Primary messenger = hormones
Other secondary messengers include cyclic GMP, cyclic AMP, and Ca ions
Represents cell communication – secretion from one cell prompts (endocrine in adrenal) another cell (target: liver) to respond

41. Lipid-Soluble Hormones
Lipid-soluble hormones are secreted through diffusion
Bind to receptors within cell (intracellular)
Travel in blood stream connected to transport protein
Pathway
Receptor transduces signal within cell
No intermediate molecular interactions like signal transduction
L-S usually involved in changes in gene transcription because actually entering cell

42. Steroid hormone receptors exist in cytosol before binding
Hormone-receptor complex forms
Receptor interacts with DNA directly or via DNA binding protein
Allows for gene expression by activating specific genes
Non-Steroid hormone receptors present in nucleus
Receptor binds to specific locations on DNA to stimulate gene transcription
Non-steroid hormones

43. Hormone Effects
Type of receptor and cell location = integral to chemical responses produced by a single hormone
Different effects allow body to have more effective and intense reactions during emergencies.
Specialized based on species
Ex: frog
Relate to previous slides pg. 980

44. Local Regulators
Act on target cells (neighboring cells or secreting cells) quicker than hormones despite following similar pathways
Prostaglandins
Produced by many cell types
Have different effects
Control of blood pressure
Dilation and constriction of blood vessels
Contraction and relaxation of smooth muscles
Other Examples: cytokines, growth factors, and nitric oxide
Reason: process begins immediately (no entering bloodstream)

45. Types of Feedback Positive Feedback Negative Feedback
 Positive feedback occurs when the rate of a process increases as the concentration of the product increases. It is not a way to maintain stable conditions and homeostasis. 
Example: Oxytocin 
Negative feedback occurs when the rate of the process decreases as the concentration of the product increases. It controls the rate of a process to avoid accumulation of a product. 
Example: Insulin

46. Negative Feedback Process of response limiting the initial stimulus
Results in turning off hormone pathway
Final and essential step in simple hormone pathways
Prevents excessive pathway activity
MAINTAINS HOMEOSTASIS
Homeostasis

47. Negative Feedback Example
Oxytocin regulation of milk during nursing
Nuerohormone pathway:
1) Baby suckling stimulates sensory neurons in nipples to send signals to hypothalamus
2) Triggers neurosecretory cell (posterior pituitary gland) to secrete neurohormone (oxytocin)
3) Oxytocin diffuses and travels to smooth muscles in breasts prompting milk release
4) Leads to more suckling increasing release
Response increasing stimulus = positive feedback
Baby stops suckling and pathway shuts off = negative feedback
Example of animal responding to environmental changes

48. Biorhythms and Melatonin
Melatonin secretion by pineal gland allows for regulation of functions connected to seasons or light
Main target for melatonin = suprchiasmatic nucleus (biological clock)
Decreases SCN activity
Amount of secretion depends on length of night
Demonstrates influence of external environment on hormone behavior

49. ADH ADH pathway responds to changes in internal environment
Osmoreceptors help regulate water balance in body

50. Insulin and Glucagon Example of a twin hormone pathway
Pathways counterbalance each other
Optimal blood glucose concentration = 90 mg/100 mL
When glucose concentration rises above this set point, insulin is released
Stimulates all body cells outside brain to uptake of glucose
Slows glycogen breakdown in liver
Prevents conversion of amino acids and glycerol to glucose
Decreases glucose concentration

51. Insulin and Glucagon
When glucose concentration drops below set point, glucagon is released
Prompts liver cells to increase glycogen hydrolysis
Converts amino acids and glycerol to glucose
Releases glucose into bloodstream
Increases glucose concentration

52. Production of located in pancreas in endocrine cell clusters called islets of Langerhans
Glucagon produced by alpha cells
Insulin produced by beta cells
Target cells = liver
Liver involved in accepting nutrients from small intestine
Opposing effect of glucagon and insulin within liver allow for control of fuel (glucose) storage and consumption
Retains homeostasis

53. Alpha Cells: secrete glucagon
Beta Cells: secrete insulin 

54. ENDOCRINE SYSTEM DISORDERS

55. Endocrine Disorders: consequences of malfunction
These disorders develop due to: 
Disruptions in the hormone levels that are caused by feedback systems. A hormone imbalance occurs when the negative feedback system fails to maintain stable conditions and homeostasis. 
Failure of certain glands to stimulate other glands in order to release hormones or release too much of the hormone. 
Injury or tumors found in any of the endocrine glands. 
Some of these disorders are Autoimmune disorders (or autoimmune related), meaning that the immune system mistakenly attacks and destroys healthy body tissue.

56. Adrenal insufficiency: Addison Disease
Autoimmune Disorder
Occurs when the Adrenal cortex secretes low levels of aldosterone into the bloodstream.
Lack of aldosterone in the blood causes low levels of sodium and water, potentially leading to low blood pressure
Severe dehydration can also occur. 
ACTH is built up and is ineffective causing one's skin to bronze, leading to a buildup of melanin. 

57. Cushing Syndrome Adrenal cortex secretes an excess amount of cortisol.
An excess of aldosterone and reabsorption of sodium and water by the kidneys
Hgh blood pressure and a basic pH blood level. 
Obesity of the midsection occurs due to muscle protein being metabolized and fat being deposited there.
Diabetes mellitus can also occur. 

58. But hey, why is this kind of important?
Thyroid gland control
The hypothalamus secretes TRH to stimulate the anterior pituitary gland, causing that gland to secrete TSH (or thyrotropin). TRH then stimulates the thyroid gland to release the hormone thyroxine. 
Thyroxine targets the hypothalamus and the anterior pituitary gland causing NEGATIVE FEEDBACK INHIBITION to occur, inhibiting the secretion of TRH and TSH. 
The negative feedback keeps thyroxine levels constant.
Thyroxine has four iodine molecules attached to its molecular structure
But hey, why is this kind of important? 

59. What is suppose to happen
Remember the iodine? Without iodine the thyroid gland cannot produce thyroxine.
The lack of thyroxine causes the hypothalamus and anterior pituitary to receive little negative feedback inhibition, thus causing high secretion levels of TRH and TSH.
High levels of TSH causes the thyroid to ENLARGE, creating a goiter.
What is suppose to happen

60. THIS IS WHY WE HAVE HAVE IODINE IN OUR TABLE SALT.
Even Disney knows what a goiter is. 
Goiters can get pretty large.
THIS IS WHY WE HAVE HAVE IODINE IN OUR TABLE SALT. 
Goiter size can be reduced if iodine is provided in one's diet. 

61. Graves' Disease
Autoimmune Disorder
A disorder in which the immune system attacks the thyroid gland, causing it to produce too much thyroxine (T4). 
It is a form and/or cause of hyperthyroidism, a condition in which the thyroid gland produces excessive hormones. 
Exophthalmos or bulging of the eyes also is a sign of Graves' disease. GOITERS, weight loss, and irregular heartbeat are also a few signs of this disease. 

62. Growth Hormone Effects
Which is controlled by the pituitary gland of course! 
Pituitary gigantism is caused by the excessive secretion of GH (growth hormone) during childhood.
Tumors in the pituitary gland can cause gigantism and dwarfism. 
Pituitary dwarfism is the opposite of gigantism: a deficiency in GH secretion during childhood causes it.
Arcomegaly is a form of gigantism that occurs when there's excessive secretion of GH in ADULTHOOD. In this form, people have protruding jaws, elongated fingers, and thickening of the skin.

63. Diabetes Mellitus: Type I
A virus causes the cytotoxic T cells (a type of white blood cell that would kill damaged or infected cells) to destroy pancreatic islets, which produce and secrete insulin and glucagon into the bloodstream.
β cells do not produce enough insulin or none at all.
The treatment for this type are insulin injections that can control glucose levels. 
Onset is early, found usually in childhood. This type is not as common as Type II.

64. Diabetes Mellitus: Type II
Type II Diabetes occurs when not enough insulin is produced by the body for it to function properly, or when the body’s cells do not react to insulin. This is called insulin resistance.
Patients with this generally have normal or even high levels of insulin in their blood, but their cells have a reduced sensitivity to it.  
Can lead to other health problems such as kidney disease and heart disease.