Endocrine SystemThe endocrine system is one of the body’s main systems

for communicating, controlling and coordinating the body’s work

Endocrine System• Control system that works along with the nervous system to

regulate body functions and maintain homeostasis.Endocrine System Nervous System

• slower response (minutes to hrs.)• potentially long duration of

effects (hours to days)• works via chemical signals

(“hormones”) which are released through interstitial fluid into blood capillaries

• affects multiple cells throughout the body that have specific hormone receptors (“target cells”) resulting in change of metabolic activities of cells (ex. affects protein synthesis)

• quick response (milliseconds)• relatively short duration of effect• works via electrical impulses

(action potentials) and direct release of chemicals (neurotransmitters) across interstitial fluid to adjacent cells

• affects specific sets of cells (neuron, muscle, gland) resulting in specific responses (ex. muscle contraction or glandular secretion)

Endocrine System Vocabulary• Endocrinology – Science that deals with a group of ductless

glands and the action of their secretions which are transported via the blood stream

• Hormones - chemical messengers carried by the blood from endocrine glands to the cell upon which they act. (target cells)• The word “hormone” is derived from a Greek term that

means to arouse to activity.• Endocrine glands vs. Exocrine glands • Exocrine glands secrete their products through ducts that

lead to an open space• Salivary glands, Sweat glands, Gastric glands, Sebaceous

gland glands • Endocrine glands secrete hormones directly into the bloodstream , no ducts involved• Thyroid gland, Pituitary, Parathyroid, Pancreas, Adrenals…

Endocrine gland

Overview of Endocrine System• Endocrine system includes all endocrine cells,

tissues, and endocrine glands (organs) of the body• System of ductless glands that secrete hormones–

chemical messengers/molecules• Circulate in blood• Act on target cells• Target cells respond to the hormones for which

they have receptors• Effects are dependent on the programmed

response of the target cells• Hormones are just molecular triggers

Overview of Endocrine System• Some organs are primarily endocrine organs/glands

(pituitary, thyroid, parathyroid, adrenal, pineal)

• Many different organs have some endocrine cells/tissues within their structure, but the organ’s primary function is not endocrine (ie: heart, kidney, digestive organs, pancreas, hypothalamus, gonads, thymus)

Classification of Hormones• Hormones classified based on their chemical structure

Steroid Based Non-Steroid BasedSteroids, lipid-like compounds derived from cholesterol• Lipid-soluble can

pass through cell membrane

• requires intracellular receptors (bind to receptors within the cell) and can directly affect the structure or function of the cell, via affect on protein synthesis &/or energy production

Amino Acid Derivatives Peptide hormones Other: Prostaglandins • Local, or tissue,

hormones• Derived from lipid

molecules• Do not travel in the

bloodstream• Target tissues are

located close by• Produced by organs

such asKidneysHeartStomach UterusBrain

• Water soluble and do not enter the cell• requires membrane receptors –(bind to

receptors on cell membrane) triggering a cascade of biological activity

• enzymes catalyzes a reaction that produced a second messenger molecule that oversees additional intracellular changes that promotes a response of the target cell

Secretion, Distribution & Effect of Hormones

Hormones are released on demand – only when needed

Hormone release is primarily regulated by negative feedback mechanisms

changes in ECF (ISF/plasma) concentration/composition

changes in circulating levels of hormone itself or regulating hormones

neural stimuli

Hormones secreted by endocrine cells into interstitial fluid, and distributed through bloodstream

Only cells that posses receptors for that particular hormone can be affected -“target cell/target organ”

Effect of hormones is on the metabolic activity of cells, via activation/inactivation of specific genes, or affecting protein synthesis

Secretion, Distribution & Effect of Hormones

Mechanisms of hormone release• Humoral: substances other than hormones control the secretion of

endocrine glands ( nutrient, ion level)• Neural: nervous system stimulates the endocrine gland to release

hormone• Hormonal: hormones from one gland stimulate the release of hormones

from another gland

Hypothalamus & Pituitary GlandThe pituitary gland, or hypophysis: • is an endocrine gland about the

size of a pea and weighing 0.5 g (0.02 oz.)

• It is a protrusion off the bottom of the hypothalamus at the base of the brain

• rests in a small, bony cavity (sella turcica) of the spheniod bone at the base of the brain

• is connected to the hypothalamus small tube called the infundibular stem (Pituitary stalk).

• has two functional lobes : the anterior and posterior pituitary

• secretes hormones that regulate homeostasis.

Hormones released from the Pituitary Gland

Pituitary Gland – Posterior lobeHormones: released

hormones made by the hypothalamus

• Oxytocin• Contractions uterus• “let down” reflex – milk

ejection

• Antidiuretic Hormone• Retention of water• Vasopressin effect ,

increase BP by constricting arterioles

Pituitary Gland – Anterior lobeGrowth Hormone

• Stimulates cells to grow & divide

• Fat broken down to use as energy

• Maintain blood sugar homeostasis

Insulin-Like Growth Factor - 1

• Bone growth• Protein synthesis

Liver and other tissues

Pituitary Gland – Anterior lobe

Prolactin (PRL)

• Stimulates/maintains milk production• Unknown function in

males

Pituitary Gland – Anterior lobe

Follicle-Stimulating Hormone (FSH) & Luteinizing Hormone (LH) also known as

Interstitial Cell Stimulating Hormone (ICSH)• Regulate hormonal activities of

gonads

Ovaries:Estrogen • Uterine lining growth• Develop/maintain secondary sex

characteristicsProgesterone• Uterine lining growth Testes:Androgens (Testosterone)• Supports sperm and secondary sex

characteristics

Ovary Testicle

Gonadotropic Hormones:

Pituitary Gland – Anterior lobeThyrotrophic hormone or Thyroid Stimulating Hormone

(TSH)• Influences growth & activity of

thyroid

Thyroxine (T4)• Stimulates metabolism

Triiodothyronine (T3)• Stimulates metabolism

Calcitonin• Decrease calcium levels

Pituitary Gland – Anterior lobeAdrenocorticotropic hormone (ACTH)• Regulates activity of adrenal

cortexAndrogensGlucocorticoids• Cortisone & cortisol• Increase blood glucose• Control inflammation• Decrease edema• Reduce pain

Mineralocorticoids/Aldosterone• Regulate water and electrolyte balance

Adrenal medulla

Epinephrine & Norepinephrine• Increase heart rate• Increase blood glucose• Increase BP• Increase metabolic rate

Long-term Stress ResponseShort-term Stress Response

Hormones released from the Pituitary Gland

Pineal Gland/Pineal Body

Also known as the “third eye”Found in roof of the third ventricle of the brainMelatonin• Involved in rhythmic activities

(day/night and seasonal)

Parathyroid glandTiny masses of glandular tissue found on posterior surfaces of thyroid glandParathyroid hormone (PTH) or Parathormone• Increases blood calcium

levels• Stimulates osteoclasts to

break down bone matrix to release calcium into the blood

Thyroid glandParathyroid gland

Thymus Gland

Posterior to sternum, superior to the heartLarge in infants and children, decreases in size throughout adulthoodThymosin• Programs “T” cells (Lymphocytes

– a type of white blood cell)• Plays role in immunity

Pancreas Islets (Islets of Langerhans)

• Formerly known as Islets of Langerhans or islands of Langerhans, irregularly shaped patches of endocrine tissue located within the pancreas

Insulin (released from beta cells)• Reduces blood glucose level• Increases ability of cells to transport

glucose across cell membrane

Glucagon (released from alpha cells)• Raises blood glucose level

Other Hormone Producing Tissue and Organs

PlacentaTemporary organHuman Chorionic Gonadotropin• Stimulates production of

estrogen and progesterone for maintenance of uterine lining

Other Hormone Producing Tissue and Organs

StomachGastrin• Stimulates glands to release

hydrochloric acid (HCl)Duodenum

Intestinal Gastrin• Inhibits HCl secretionSecretin• Aids in functions related to

digestion effecting pancreas, liver and stomach

Cholecystokinin (CCK)• Aids in functions related to

digestion effecting pancreas, gall bladder and duodenum

Other Hormone Producing Tissue and Organs

Kidneys Erythroprotein• Effects bone marrow

stimulates red blood cell production

Vitamin D3 (Calcitriol)• Aids in the active transport of

dietary calcium across intestinal cell membrane

Other Hormone Producing Tissue and Organs

Heart Atrial Natriuretic Peptide (ANP)• Affects kidney by decreasing

sodium reabsorption and releasing renin (enzyme that aid in increasing BP)

• Affects adrenal cortex decreasing secretion of aldosterone

Endocrine gland & Hormone reviewA.

• Name the gland.

• Identify the hormone(s) released from gland.

• Mechanism of stimulus/Regulated by?

Endocrine gland & Hormone reviewB.

• Name the gland.

• Identify the hormone(s) released form gland.

• Mechanism of stimulus/Regulated by?

Endocrine gland & Hormone reviewC.

• Name the gland.

• Identify the hormone(s) released form gland.

• Mechanism of stimulus/Regulated by?

Endocrine gland & Hormone reviewD.

• Name the gland.

• Identify the hormone(s) released form gland.

• Mechanism of stimulus/Regulated by?

Endocrine gland & Hormone reviewE.

• Name the gland.

• Identify the hormone(s) released from gland.

• Mechanism of stimulus/Regulated by?

Endocrine gland & Hormone review

F.• Name the gland.

• Identify the hormone(s) released form gland.

• Mechanism of stimulus/Regulated by?

Endocrine gland & Hormone reviewG.

• Name the gland.

• Identify the hormone(s) released form gland.

• Mechanism of stimulus?

Endocrine gland & Hormone reviewH.

• Name the gland.

• Identify the hormone(s) released from gland.

• Mechanism of stimulus/Regulated by?

Endocrine ReviewMatching I

1. _____ Stimulate development of the follicle in the ovaries2. _____ Stimulates the kidney to reabsorb water from urine3. _____ Stimulates the thyroid gland4. _____ Stimulates the adrenal cortex5. _____ Promotes protein synthesis necessary for growth

A. FSH

B. GH

C. ACTH

D. TSH

E. ADH

Endocrine ReviewMatching II1. _____ Increases blood glucose levels2. _____ Decreases blood calcium levels3. _____Regulates body metabolism4. _____ Increases blood calcium levels5. _____Regulate electrolyte balance

A. Aldosterone

B. Glucagon

C. Thyroxine

D. Calcitonin

E. Parathyroid hormone

Endocrine Review

• Review chart in text pp. 270-271 to review major glands, hormone(s) released, hormone(s) chemical class, their actions and means of regulation.

Continue on to learn about Factors that Affect Endocrine Function

Factors that Affect Endocrine FunctionEveryone's body undergoes changes, some natural and some not, that can affect the way the endocrine system works. Some of the factors that affect endocrine organs include:• aging • illness • stress• the environment• and genetics.

AgingDespite age-related changes, the endocrine system functions well in most older people. However, some changes do occur because of normal damage to cells during the aging process and genetically programmed cellular changes. These changes may alter the following:

• hormone production and secretion

• hormone metabolism (how quickly excess hormones are broken down and leave the body, for example, through urination)

• hormone levels circulating in blood

• biological activities

• target cell or target tissue response to hormones

• rhythms in the body, such as the menstrual cycle

Aging• For example, increasing age is thought to be related to the

development of Type II diabetes. With aging, the target cell response time becomes slower, especially in people who might be at risk for this disorder.

• The signs and symptoms of endocrine system diseases affect many body systems. In elderly persons, they are frequently subtle and may be harder to detect than in younger persons. At times, these signs are incorrectly linked with other causes, such as the changes of normal aging, other medical disorders or conditions, or drug therapy.

• The aging process affects nearly every gland. For example, the hypothalamus is responsible for releasing hormones that stimulate the pituitary gland. During aging, there is either impaired secretion of some hypothalamic hormones or impaired pituitary response. These changes appear to influence the endocrine system's ability to respond to the body's internal environment. As a result, the body cannot respond as well either to internal or external stresses

Aging• With increasing age, the pituitary gland can become smaller

and more fibrous and may not work as well. For example, production of growth hormone may decrease. This may lead to a hormone imbalance that causes problems such as decreased lean muscle, decreased heart function, and osteoporosis.

• Aging can affect a woman's ovaries. These organs eventually exhibit the most common endocrine change related to aging: menopause. In menopause, the ovaries stop responding to follicle-stimulating hormone and luteinizing hormone from the anterior pituitary. Ovarian hormone production of estrogen and progesterone slows down and then stops. Eventually a woman stops having her periods altogether

IllnessIllness may affect endocrine system function in several ways. Acute or chronic conditions may change endocrine functions.Chronic/Acute Conditions• Hormones are cleared from blood during their circulation to

the target tissues. The liver and kidneys are primarily responsible for clearing hormones. Several clearance processes become altered or slowed in individuals who have chronic heart, liver, or kidney disorders.

• Acute physical or mental stressors can trigger a preprogrammed stress response. The stress response is complex and can influence heart, kidney, liver, and endocrine system function.

Endocrine PathologiesEndocrine pathologies can result from the following:

• congenital (birth) or genetic defects

• surgery

• traumatic injuries

• cancerous and non-cancerous tumors

• infection

• autoimmune destruction (the immune system turns against the body's own organs and causes damage)

• In general, endocrine pathologies create a hormone imbalance typified by either hyposecretion (underproduction) or hypersecretion (overproduction) of hormones. The underlying problem may be the endocrine gland itself or a source outside the gland.

StressMany factors can start the stress response, but physical stressors are most important. In order for the body to respond to, and cope with, physical stress, the adrenal glands make more cortisol. If the adrenal glands do not respond, this can be a life-threatening problem. Some medically important factors causing a stress response are as follows:

• trauma (severe injury) of any type

• severe illness or infection

• intense heat or cold

• surgical procedures

• serious diseases

• allergic reactions

• Other types of stress include emotional, social, or economic, but these do not require the body to produce high levels of cortisol in order to survive the stress.

External Factors• An environmental endocrine disruptor (EED) is a substance

outside of the body that may cause adverse effects to normal function of the endocrine system. Some EEDs mimic natural hormone binding at the target cell receptor. These substances start the same processes between body cells that the natural hormone would start. EEDs of this type are referred to as hormone agonists.

• Other EEDs block cellular events associated with hormone binding. These EEDs are called hormone antagonists. Still other EEDs can directly interfere with the production, storage, release, transport, clearance, binding, or elimination of endogenous hormones in the body. This can greatly affect the function of certain body systems.

External FactorsThere are currently over 84,000 commercial synthetic chemical substances in use around the world. At least 30,000 have been introduced into the U.S. environment since 1979. We do not know the extent to which they can interfere with the endocrine system and cause endocrine system diseases. Based on our knowledge of the effects of certain synthetic chemicals, such as DDT, diethylstilbestrol and PCBs, and the increasing evidence that reproductive function in wildlife and humans is changing, scientists are now examining a broad range of chemical effects.EEDs can affect people and animals in many ways:

• disrupted sexual development

• decreased fertility

• birth defects

• decreased hatching in animals

• reduced immune response

• neurological and behavioral changes, including reduced stress tolerance

Genetics• Portions of your endocrine system can be affected by genes. Genes

are units of hereditary information passed from parent to child. Genes contain the instructions for the production of proteins, which are some of the essential components of the body. Genes are contained in chromosomes. The normal number of chromosomes is 46 (23 pairs).

• Sometimes extra, missing, altered, or damaged chromosomes can result in diseases or conditions that affect hormone production or function. The 23rd pair, for example, is the sex chromosome pair. The mother and father each contribute a sex chromosome to the child. Girls have two X chromosomes (one from the mother and one from the father), while boys have one X (from mother) and one Y (from father) chromosome. Sometimes, however, a chromosome or piece of a chromosome may be missing. In Turner syndrome, only one normal X chromosome is present and this can cause poor growth. In another example, a child with Prader-Willi syndrome (PWS) may be missing all or part of chromosome 15, which also affects growth, metabolism, and puberty.

Genetics• Your genes also may place you at increased risk for certain

diseases, such as breast cancer. Taking estrogen can cause breast tissue to grow faster. Cancer usually appears in fast-growing tissue. This is one of the ways that scientists believe that taking estrogen for symptoms of menopause may be related to developing breast cancer. Another idea is that breast tissue breaks down estrogen into chemicals that can bind to DNA (genetic material) and damage it. Damage to DNA is a common cause of cancer. At this time, it is not known exactly why estrogen might cause breast cancer or what role it does play in breast cancer growth.

Cycles of Hormone ReleaseTime appears to affect the release of certain types of hormones. Some hormones have a typical cycling pattern of release. This pattern often fits with daily body rhythms or the sleep-wake cycle.

• Cortisol builds up early in the day, decreases toward evening, rises again toward the end of sleep, and peaks during the morning hours.

• Thyroid-stimulating hormone (TSH) peaks during sleep and reaches its low point three hours after an individual awakens.

• Levels of growth hormone (GH) are high 90 minutes after sleep begins. GH typically increases during the first 2 hours of deep sleep. It also increases if a person is hypoglycemic (low blood sugar), starving, exercising, excited or is a victim of severe injury.

• There is a very definite rise-and-fall pattern to both estrogen and progesterone activity during a woman's menstrual cycle, which lasts an average of 28 days.

Endocrine disorders: Classification of endocrine system disorders

The broad classification of endocrine system diseases is based on the hormonal secretions. • Hypersecretion by endocrine glands (Excessive

secretion of hormones)• Hyposecretion by endocrine glands (Insufficient

secretion of hormones)• Cancer or tumors in the endocrine gland

In summary• The endocrine system includes all of the

glands of the body and the hormones produced by those glands. The glands are controlled directly by stimulation from the nervous system as well as by chemical receptors in the blood and hormones produced by other glands. By regulating the functions of organs in the body, these glands help to maintain the body’s homeostasis.