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The Endocrine System. Nervous vs. Endocrine. Intro to Endocrine System Animation. Both systems oversee cell-to-cell communication using chemical signals Chemical signals both bind to receptor molecules Receptors are VERY specific to only respond to certain signals. Exocrine vs Endocrine.

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nervous vs endocrine
Nervous vs. Endocrine

Intro to Endocrine System Animation

  • Both systems oversee cell-to-cell communication using chemical signals
    • Chemical signals both bind to receptor molecules
    • Receptors are VERY specific to only respond to certain signals
exocrine vs endocrine
Exocrine vs Endocrine

Classified by location of secretion


Through tube or duct to a surface (outside)

Ex: skin, lining of digestive tract


Secrete into internal environment

Help regulate metabolic processes

How? Controlling rate of chemical rxns, aiding in transport of substances , regulating H2O and electrolytes

Ex: Thymus, hypothalamus, pineal, adrenal

endocrine glands
Endocrine Glands

Can be cell, tissue, or organ (gland)

Secrete hormones

Hormones are chemical messengers

Diffuse from interstitial fluid into the blood stream, eventually acting on a target cell

Target cell

Receives the message

Receptor for hormone

Hormone creates a response in target cell

Tropic hormones

Hormone whose target cell is another endocrine gland

other chemical messengers
Other Chemical Messengers

“Local Hormones”

Never reach bloodstream

2 types:

Paracrine - affect neighboring cells

Autocrine - affect only cell secreting them


Lipids messenger usually affecting organ secreted into

Ex: inducing childbirth, treat glaucoma, treat erectile dysfunction

types of hormones
Types of Hormones

Two types:

1) Cholesterol Derivatives

Ex: Steroids (estrogen, testosterone, aldosterone, cortisol)

2) Amino Acid Derivatives

Ex: Amines (norepinephrine, epinephrine)

Ex: Peptides (ADH, oxytocin)

Ex: Proteins (Parathyroid hormones, growth hormones, prolactin)

Ex: Glycoprotein (follicle-stimulating hormone, luteinizing hormone, thyroid-stimulating hormone)

hormone action
Hormone Action

Steroid Hormone


Must be carried by plasma proteins through blood

Insoluble in water

Made of rings of carbon and hydrogen atoms

Action sequence of events for steroids:

Diffuse into any cell

Binds to receptor in cell , enters the cell

Activates specific area of DNA

Protein synthesis is end result

Examples: Estrogen, testosterone, aldosterone, cortisol

hormone action cont
Hormone Action (cont)

Nonsteriod hormone (amines, peptides, proteins)


Activate proteins which alter cellular processes

Ex: altering membrane permeabilities, activating enzymes, stimulating metabolic processes, release of other hormones

Ex: growth hormone, epinephrine, oxytocin

Sequence of events in nonsteroids:

Hormone (primary messenger) binds to receptor on outside of cell

Binding causes activity center inside cell to activate a messenger (sometimes cAMP) – called second messenger

This messenger then causes change

hormonal control
Hormonal Control

Controlled by increasing or decreasing hormone secretion (VERY precise!)

See Figure 11.5!!!!!!!

Stimulation of hormone release:

All use negative feedback mechanisms

Hypothalamus and pituitary

Nervous system

Changing internal environment

Inhibition of hormone release:

Negative feedback loop

practice quiz take on notes
Practice Quiz (take on notes)
  • 1.  The hormone _______________ helps to stimulate the development of female secondary sex characteristics. This hormone is produced by the ovaries in the female.
  • 2. The hormone _______________ is called the "fight or flight" hormone.
  • 3. The hormone _______________ maintains the thickness of the uterus lining in preparation for a possible pregnancy.
  • 4. The hormone _______________ stimulates the conversion of excess sugar in the blood to glycogen which is animal starch in the liver and assists in taking glucose into the cells.  This hormone is produced in the pancreas.

1.    estrogen

2.    adrenalin

3.    progesterone

4.    insulin

practice quiz continued
Practice Quiz Continued
  • 5. The major secretions of the endocrine glands are called _______________.
  • 6. The hormone _______________ helps to stimulate the development of secondary sex characteristics in the male.
  • 7. The condition _______________ results usually from an inability to regulate blood glucose levels properly. (Usually the blood glucose tend to become too high.)
  • 8. _______________ are all the ductless glands.

5.    hormones

6.  testosterone

7.  diabetes

8.  endocrine glands

  • Located deep inside the brain
  • Releasing and inhibiting hormone secretion to anterior pituitary
  • Direct innervations to posterior pituitary
pituitary gland
Pituitary Gland
  • Located deep within the brain
  • Divided into 2 sections:
    • Anterior Pituitary
      • glandular epithelium with many blood vessels
    • 2) Posterior Pituitary
      • nerve fibers and neuroglial cells
tropic hormones of the anterior pituitary
Tropic Hormones of the Anterior Pituitary

Thyroid-stimulating hormone (TSH)

Adrenocorticotropic hormone (ACTH)

Gonadotropins: 2 types

Follicle-stimulating hormone (FSH)

Lutenizing hormone (LH)

thyroid stimulating hormone tsh
Thyroid-stimulating hormone (TSH)


Thyrotropin-releasing hormone (TRH) from hypothalamus


Circulating thyroid hormones decrease TSH and TRH secretion

Target Cell:

Thyroid gland/cells


Increase thyroid secretions

adrenocorticotropic hormone acth
Adrenocorticotropic hormone (ACTH)


Corticotropin-releasing hormone (CRH) from hypothalamus

Target Cell:

Adrenal cortex


Increase adrenal cortex secretions

follicle stimulating hormone fsh
Follicle-stimulating hormone (FSH)


Gonadotropin-releasing hormone from hypothalamus

Target Cell:

Gonads (testes in males and ovaries in females)


Female- maturation of egg; secretion of estrogen

Male- development of sperm

lutenizing hormone lh
Lutenizing hormone (LH)

Also called Interstitial cell stimulating hormone (ICSH)


Gonadotropin-releasing hormone from hypothalamus

Target Cell:

Gonads (testes in males and ovaries in females)


Female- release of mature egg from ovary (ovulation)

Male- development of interstitial cell; secretion of male sex hormones

other hormones of the anterior pituitary
Other hormones of the Anterior Pituitary

Growth Hormone (GH)


GH-releasing hormone from hypothalamus


GH release-inhibiting hormone

Target Cell: Somatic cells (non-sex cells)


Enhances movement of amino acids across cell membrane; speeds up rate of carbohydrate utilization

other hormones of the anterior pituitary1
Other hormones of the Anterior Pituitary

Prolactin (PRL)

Stimulates breast development necessary for lactation

Stimulates breast to secrete milk after birth

posterior pituitary
Posterior Pituitary

Antidiuretic hormone (ADH)


Nerve Impulse from hypothalamus when osmoreceptors sense dehydration

Target Cell: kidneys


Kidneys produce less urine to conserve water

Oxytocin (OT)

Stimulates contraction of the pregnant uterus

Stimulates “let-down” of milk

thumbs up thumbs down
Thumbs Up, Thumbs Down

TSH is released by thyroid gland


Most pituitary-released hormones are controlled/stimulated by hypothalamus


Prolactin stimulates gonad development


Oxytocin helps uterus to contract during labor


ADH prevents you from becoming dehydrated by preventing your kidneys from making urine



Quick Review of Pituitary control

  • Location: attached to front of trachea
  • Contains follicles
  • Follicles have hollow center cavity filled with colloid
thyroid cont
Thyroid (cont)

Follicular cells of thyroid secrete two hormones:

1) Thyroxine (tetraiodothyronine) - T4

2) Triiodothyronine - T3 (much more potent)

Increases metabolism of carbohydrates, lipids, and proteins

Extrafollicular cells of thyroid secrete calcitonin

Lowers blood calcium level by inhibiting osteoclasts (bone cells)

Makes kidney secrete more calcium in urine

parathyroid glands
Parathyroid glands

Located on the thyroid in four patches

Highly dense, secretory cells

Secrete Parathyroid hormone (PTH)

Raises blood calcium levels

Inhibits osteoblasts

Stimulates osteoclasts

Makes kidneys conserve calcium

Increase absorption of calcium in intestine

Opposite of calcitonin

adrenal glands
Adrenal glands

Very closely related to kidneys

Located/Sit on top of kidneys

Consists of two parts:

Adrenal cortex

Adrenal medulla

adrenal cortex
Adrenal Cortex

Three layers:

Outer, middle, and inner

Closely packed masses of epithelial tissue

Makes up bulk of adrenal glands

Well-supplied with blood

outer layer of cortex
Outer Layer of Cortex

Outer (glomerulosa)

Mineralocorticoid (MC)- regulate mineral electrolytes

Ex: Aldosterone hormone

Stimulated by decrease in blood levels of sodium, increase in potassium in blood levels, or decrease in blood pressure

Cause kidneys to retain sodium and secrete potassium into urine

Indirectly, water is retained – IMPORTANT!

adrenal cortex cont
Adrenal Cortex (cont)

Middle (fasciculata)

Glucocorticoids- affects glucose metabolism

Ex: Cortisol or hydrocortisone hormones

Increase gluconeogenisis (glucose synthesis)

Inhibition of protein synthesis

Promotion of fatty acid release from adipose tissue

Produce state of stress

adrenal cortex cont1
Adrenal Cortex (cont)

Inner (reticularis)

Secretes sex hormones

Produces androgen hormones

Can be used to synthesize female sex hormones like estrogens

adrenal medulla
Adrenal Medulla

Irregularly shaped cells

Well supplied with blood

Composed of modified neurons

Secrete epinephrine (adrenaline) and norepinephrine (noradrenaline)

Important in “Fight or Flight” response

Directly innervated by sympathetic nervous system


Structure and Location:

Elongated, somewhat flattened

Posterior to stomach

Duct joins pancreas to intestine

Dual function:

1) Exocrine gland: secretes digestive juices

2) Endocrine gland: releases hormones

Contains groups of cells closely related to blood vessels

Called islets

pancreatic islets islets of langerhans
Pancreatic Islets (Islets of Langerhans)

Made of two types of secretory tissues/cells:

Alpha cells

Secrete hormone: glucagon

Accelerates process of gylcogenolysis

Beta cells

Secrete hormone: Insulin

Increases movement of glucose inside of cells for metabolism

Stimulates liver to produce glycogen

exit slip
Exit Slip

1) T3 is released by what gland?

2) Which hormone (cortisol or T4) produces a state of stress?

3) The pancreas has a duct/tube which connects it directly to what digestive system organ?


1) Thyroid

2) Cortisol

3) Intestines

  • Located in mediastinum cavity
  • Secretes hormones called thymosins
  • Important function in development of immune system
pineal gland
Pineal gland

Releases hormone melatonin

Regulates body clock and sleep cycle

female sex glands
Female Sex Glands


Ovarian follicles

Corpus luteum

We will discuss these (and their hormones) in the reproductive chapter!

male sex glands
Male sex glands


Interstitial cells produce testosterone

Testosterone stimulates sperm production

  • Provides nutrients to embryo/fetus while developing
  • Secretes chorionic gonadotropins
    • Pregnancy tests test for the presence of this hormone
  • Prevents dissolution of corpus luteum (prevents menstrual cycle)
other hormones
Other hormones


Wall of Atrium:

Secretes AtrialNatriuretic hormone

Regulates fluid and electrolyte balance

How? By increasing removal of sodium and water

Various Digestive Glands (will discuss in Digestive chapter)


Erythropoietin- red blood cell growth hormone

  • Hormone Review:
  • Type in “hormones” in search bar!
stress and the endocrine sys
Stress and the Endocrine Sys.

Stress: A factor that can stimulate an increase in the sympathetic division of your PNS

Causes increase in secretion of adrenal gland (and other) hormones

Homeostatic mechanisms become threatened

Due to change in internal/external environmental factors

Ex: Lack of sleep, death of family member, depression, danger

yes no maybe so
Yes/No/Maybe So

Your thymus gland is connected to your immune system.


The placenta provides nutrients to embryo and also can start a menstrual cycle.

NO! – prevents menstrual cycles

Your heart can release hormones!


types of stress
Types of Stress

Physical factors:

Ex: exposure to extreme heat/cold, decreased oxygen concentration, infections, injuries, prolonged heavy exercise, loud sounds

Physiological factors:

Ex (unpleasant): thoughts about real/imagined danger, personal loss, unpleasant social interactions, anxiety, depression, guilt

Ex (pleasant): feelings of joy/happiness, sexual arousal, friendly social contact

stress response
Stress response

Physiological factors affect hypothalamus

Occurs in two stages:

1) Immediate “alarm” stage

Hypothalamus prepares for “fight or flight”

Include: raise in blood glucose; increase heart rate/blood pressure; increase epinephrine secretion from adrenal

stress response cont
Stress response (cont)

Physiological factors affect hypothalamus

Occurs in two stages:

2) Longer “resistance” stage

Hypothalamus release CRH (stimulates anterior pituitary to secrete ACTH)

Increases cortisol secretion (cortisol supplies cells with biochemicals required to deal with stress)

endocrine system disorders
Endocrine System Disorders


Over-activity of thyroid cells

Causes elevated metabolic rate, restlessness, overeating, eye protrusion, goiter (enlarged thyroid gland)


Cretinism: stunted growth, abnormal bone formation, mental handicaps, sluggishness

Often, weight gain/puffiness in face, hands and feet is associated with hypothyroidism

endocrine system disorders1
Endocrine System Disorders

Diabetes Mellitus

Metabolic issue caused by lack of insulin (or inability for cells to recognize insulin)

Reminder: Insulin helps glucose cross cell membranes

In diabetics, glucose doesn’t move into fat and skeletal muscle tissue


Glucose in urine increases, causing excessive urine output

Dehydration and extreme thirst

Muscles use proteins (instead of glucose) for energy

Stunted growth, wounds don’t heal properly, exhaustion

endocrine system disorders2
Endocrine System Disorders

Diabetes Mellitus, cont.

Two types:

Type 1:

Insulin-dependent (juvenile diabetes)

Usually appears before age 20

Auto-immune disease (destroys beta cells of pancreas)

Treatment: Give insulin (inject several times day/week)

Type 2:

Non-insulin dependent (maturity-onset)

85-90% of people with diabetes have Type 2

Beta cells produce insulin but body cells don’t recognize it

Develops gradually after age 40

Milder symptoms, controlled by diet (usually)

Blood sugar animation