Importance of the Endocrine System

8.1

the system of glands that produce endocrine secretions (hormones) that help to control bodily metabolic activity

What is the Endocrine System?

Chemical regulators produced by cells in one part of the body that affect cells in another part of the body (“to excite or set into motion” speed up or slow down processes)◦ Endocrine hormones: chemicals secreted by endocrine glands

directly into the blood.◦ Nontarget hormones: no specific destination affects many

cells throughout the body. Classified according to their activation site.

Growth hormone (GH) or somatotropin (STH) regulates development of long bones.

Insulin: regulates blood sugar by increasing the permeability of cells to glucose

Epinephrine (adrenaline): produced in times of stress. ◦ Specific hormones affect specific cells or target tissues

Parathyroid hormone: regulates calcium levels Gastrin: stimulates cells of stomach to produce digestive enzymes.

Hormones

Nervous system + Endocrine System controls function of organs and tissues.◦ Nervous system: quick adjustments to

environment◦ Endocrine system: maintain control over a longer

duration. GH and sex hormones: regulate and sustain

development for many years.

Chemical Control Systems

Division between the nervous system and endocrine system is most subtle in the hypothalamus. ◦ Hypothalamus: regulates pituitary gland through

nerve stimulation.◦ Endocrine glands: stimulated by pituitary: secrete

chemicals that affect the nerve activity of the hypothalamus.

The Hypothalamus

Serve as regulators: speed up or slow down certain bodily processes.

Hormones

Mering & Minkowsky: 1889◦ Pancreas responsible for regulation of blood sugar?◦ Removed pancreas from dogs

weight loss & fatigued (symptoms of diabetes). ants gathered in kennels with sick dogs.

Urine of sick dogs contained glucose◦ Insulin (regulation of blood sugar) produced by pancreas.◦ Typical experimental method: gland/organ removed

effects monitored animal injected with varied amounts chemical extracts from organ monitored.

Problems: concentrations of other hormones increase to compensate for

disorder. Extra glands removed (ex. Thyroid & parathyroid) Hormone concentration varies throughout the day.

The Relationship between Chemical Messengers and activity of Organ systems

Radioactive tracers: recent technological advance◦ Enables scientists to follow messenger chemicals

from organ in which they are produced to target cells.

◦ Discern how chemical messengers are broken down into other compounds and removed as wastes.

Radioactive Tracers and the Endocrine system

Hormones are very specific◦ Cells may have receptors for only one hormone◦ Different types of cells may have a different

number of receptor sites for the same hormone (this all depends on how active the cell is in the process in question).

Specificity of Hormones

Steroid hormones◦ Modified cholesterol (_______________)

Composed of complex rings of C, H, and O (solubility?)

Male and female sex hormones Cortisol (AA glucose by liver)

Protein hormones◦ Chains of __________ varying in length.

Soluble in water. Insulin GH

Steroid vs. Protein Hormones

Capillaries interstitial fluid target cells (diffusion!)◦ Within cytoplasm, SHs combine with receptor

molecules.◦ Hormone-receptor complex (HR complex) moves

into nucleus◦ HR complex attaches to segment of chromatin(?)

that has a complimentary shape◦ HORMONE ACTIVATES A GENE SPECIFIC

PROTEIN IS SYNTHESIZED.

Steroid Hormones

THE DIAGRAM IN THE TEXTBOOKIS CONFUSING/MISLEADING.ACCORDING TO THE FORMER INFORMATION, HOW WOULD YOUDEPICT THE ACTION OF STEROIDHORMONES?

Capillaries interstitial fluid cell membrane◦ Protein hormones (PHs) combine with receptors

on the cell membrane. PH + receptor activates production of enzyme

which causes cell to convert ATP to AMP. AMP: CYCLIC ADENOSINE MONOPHOSPHATE:

secondary chemical messenger that directs the synthesis of protein by ribosomes Activates enzymes in cytoplasm to carry out NORMAL

functions.

Protein Hormones

The two main types of hormones are ______________and ______________ hormones.

Steroid hormones:◦ Steroids are a type of ___________. They can diffuse through the

__________________.◦ While in the cytoplasm, a SH may combine with a _______________

molecule. This complex moves into the _____________ where it attaches to ________ which will then activates a gene and consequently produce a specific ___________________.

Protein hormones:◦ Proteins are made up of ___________. Many of these may be polar.

Therefore, they cannot easily diffuse through the ______________. ◦ PHs combine with receptor sites on the target cell’s

________________. ◦ PH + receptor site reaction inside of the cell.

ATP _____________ AMP activates ___________________ to carry out normal functions.

Main ideas so far...

TSH = thyroid-stimulating hormone Attaches to receptor sites in the cells of the

thyroid gland AMP is produced within cells specific enzymes are activated thyroxine is produced increases metabolism & growth regulated

Thyroxine: increases rate of metabolism and regulates growth.

Example of a Protein Hormone

Controls most other endocrine glands. Connected to the hypothalamus

◦ Pituitary + hypothalamus: interconnected. Pituitary gland: produces and stores hormones. Hypothalamus: stimulates the release of hormones

by the pituitary gland by way of nerves.

The Pituitary Gland: The Master Gland (1)

Two lobes:◦ Posterior:

stores and releases hormones like ADH and oxytocin (oxytocin uterine contractions during labour).

both produced by the hypothalamus. Posterior lobe does not produce hormones hormones sent to

pituitary via. specialized nerve cells. ◦ Anterior:

Produces its own hormones. Rich with nerves from hypothalamus regulates release of

hormones from anterior pituitary. Hypothalamus releasing factors: inhibit secretion of hormones from

anterior lobe Dopamine: inhibits secretion of prolactin (stimulates milk production) Somatostatin: inhibits secretion of somatotropin (growth of long bones)

The Pituitary Gland: The Master Gland (2)

Pituitary Hormones

Understanding Concepts

Pancreas◦ Contains two types of cells

1) produces digestive enzymes 2) produces hormones

Located in structures called the islets of Langerhans Thousands of islets containing thousands of cells each

responsible for production of insulin and glucagon. Alpha and beta cells

INSULIN (beta cells): secreted with blood sugar levels are high

GLUCAGON (alpha cells): promotes conversion of glycogen to glucose when blood sugar levels are low

8.2 – Hormones that Affect Blood Sugar

Produced in beta cells After a meal, blood sugar levels increase Appropriate amt. Of insulin released Insulin causes cells of muscles, liver, and

other organs to become permeable to glucose◦ Liver: glucose converted to glycogen:

_____________________________________. therefore, blood sugar levels _______________.

Insulin

Produced by alpha cells Periods of fasting blood sugar levels are

low glucagon released Promotes conversion of glycogen to glucose

(liver) which is released into blood. ◦ therefore, blood sugar levels ______________.

Glucagon

Chronic disease No cure Affects more than 2 million Canadians Overall: insufficient production or use of

insulin. Can cause blindness, kidney failure, nerve

damage, and nontraumatic limb amputation.

Diabetes(1)

Without insulin, blood sugar levels __________ rapidly after meals. ◦ Hyperglycemia: high blood sugar.

Kidneys unable to reabsorb all blood glucose: glucose in urine.

High concentrations of glucose in nephrons draw water out of blood/interstitial fluid unusually large volumes of urine, often thirsty.

◦ Low energy levels: cells are not permeable to glucose. Cells turn to other sources of energy: fats and proteins

acetone (intermediate of excessive fat metabolism) may build up.

How Diabetes ‘works’

Type 1◦ Early degredation of beta cells in islets of Langerhans◦ Diagnosed in childhood◦ About10% of cases

Type 2◦ Decrease production/ineffective use of insulin◦ Diagnosed in adulthood controlled by diet, exercise, oral

drugs. ◦ About 90%

Type 3◦ Gestational diabetes: temporary◦ Occurs in 2-4% of pregnancies; increase of diabetes in

mother and child.

Types of Diabetes Mellitus

Read sections “Research in Canada...” and “Frontiers of Technology”, starting on page 379.

Answer the following questions in your notebook:1) What problem does extracting hormones from the pancreas

present?2) Briefly describe the procedure and results from Banting and

Best’s experiments.3) What is the second leading cause of blindness in Canada?

What are some other side effects of this disease?4) What could possibly reverse the effects of diabetes? What is

the main barrier keeping this medical procedure from occuring?

5) Briefly describe the Edmonton Protocol. Why is the liver used?6) What is the challenge with the Edmonton Protocol? What is it

that is currently providing insulin-producing cells?

Independent Reading

Located above each kidney. 2 glands encased in one shell

◦ Adrenal medulla: core of adrenal gland Produces epinephrine and norepinephrine Controlled by nervous system

◦ Adrenal Cortex Hormone regulated

Adrenal Glands

Epinephrine: also known as adrenaline. Norepinephrine: also known as

noradrenaline.

Both released from adrenal medulla into blood in times of stress. ◦ Glycogen converted to glucose blood sugar rises

Greater energy reserve available right away. ◦ Increase of heart rate, breathing rate, and cell

metabolism. Blood vessels dialate, iris of eye dilates.

Epinephrine & Norepinephrine

Produces glucocorticoids: three different TYPES of hormones◦ Designed to help body meet demands of stress. ◦ Cortisol (most important):

increases levels of amino acids in blood in attempt to help body recover from stress. AAs Converted to glucose by liver, raising blood sugar. AAs not converted: available for protein synthesis

repair damaged cells. Fats and adipose tissue broken down into FAs

source of energy

Adrenal Cortex

Hypothalus sends a releasing hormone to the anterior lobe of the pituitary

Corticotropin (adrenocorticotropic hormone, ACTH) released adrenal cortex secretes hormones like cortisol target cells in liver and muscles as cortisol levels rise, cells within hypothalamus and pituitary decrease production of regulatory hormones cortisol decreases.

Long-term stress Response

Regulated by adrenal medulla secretes epinephrine & norepinephrine.

Short-term stress Response

A mineralocorticoid. Increases sodium retention and water

reabsorption by kidneys maintain body fluid levels.

Aldosterone (again)

Page 383#1-7

Seatwork/Homework

What is metabolism, again? Three glands which affect metabolism are:

◦ Thyroid gland Produces three major hormones

◦ Parathyroid glands Produces the parathyroid hormone

◦ Anterior pituitary gland Produces the growth hormone along with many other

regulatory hormones

8.3 – Hormones that Affect Metabolism

Located at the base of the neck, in front of the trachea

Two important thyroid hormones:◦ Thyroxine (T4)

65% of thyroid secretions◦ Triiodothyronine (T3)

Thyroid Gland

Have you ever wondered why some people seem to consistently eat a lot of food, and not gain any weight?

This is partially due to the hormone thyroxine.

Metabolic Rate and YOU

High levels of thyroxine means increased metabolic rate◦ 60% of the energy of glucose metabolized is

released as heat People with a ‘high’ metabolic rate usually feel

warm.◦ 40% is transferred to ATP not to fat.

These people do not tend to gain weight.

High levels of Thyroxine

Those with low levels of thyroxine do not tend to break down sugars very quickly.

Excess blood sugar is eventually converted to liver and muscle glycogen. ◦ Once glycogen stores are filled, excess sugar is

converted into fat.

Low levels of Thyroxine

Not all weight gain is due to low thyroid secretions.

In many cases, it reflects a poor diet.

Important note:

Accomplished through negative feedback If metabolic rate decreases receptors in

hypothalamus nerve cells secrete thyroid-releasing hormone (TRH) TSH released from pituitary carried through blood to thyroid gland release of thyroxine

THYROXINE: increases metabolism by stimulating increased sugar utilization by body cells.

High levels of thyroxin inhibits release of TRH from hypothalamus negative feedback!

Control of Thyroid Hormones (Thyroxine)

Iodine: important component of thyroid hormones. ◦ Normal component in the blood◦ Actively transported from blood to follicle cells of

the thyroid. Goiter: inadequate amounts of iodine in diet.

◦ Without iodine, thyroid production and secretion of thyroxine drops.

◦ What effect would this have on the production of TSH: ______________________. Thyroid stimulated more and more cells develop thyroid enlarges.

Thyroid Disorders

In many countries, iodine is added to table salt to prevent this condition.

Four small parathyroid glands in the thyroid gland. ◦ Surgeons removed enlarged thyroid glands tetanus in

patients abnormal calcium levels. Parathyroid glands maintain homeostasis by

responding directly to chemical changes in immediate surroundings. ◦ Low calcium levels release of parathyroid hormone (PTH)

calcium levels in blood increase & phosphate levels decrease Kidneys: retain calcium while promoting calcium release from

bone (98% of calcium storage). Bone cells break down and calcium separated from phosphate ion Calcium into blood Phosphate excreted with urine

Parathyroid Glands(1)

Once calcium levels elevated, release of PTH inhibited◦ What dangers would be associated with

abnormally high levels of PTH? ___________________________________________________________________________________________________.

Parathyroid Gland (2)

Partially activated by PTH Helps in absorption of calcium. Too little calcium improper bone

development.

Vitamin D

Somatotropin: growth hormone! Dwarfism: low secretions during childhood Gigantism: high secretion during childhood. Physical signs are most pronounced in

cartilage and bone cells. ◦ If production of growth hormone continues after

cartilaginous growth plates are fused, other bones respond. Long bones can no longer increase in length, only in

width acromegaly

Growth Hormone (1)

GH causes cells of soft tissues and bones to grow by increasing:◦ Number of cells: hyperplasia◦ Size of cells: hypertrophy

Does this by promoting protein synthesis while inhibiting protein degredation. ◦ AA uptake increases◦ Ribosomes follow genetic instructions.

Aging: GH production declines & protein replaced by fat: change in body shape.

Growth Hormone (2)

Seatwork/Homework: Page 387, # 1-8.

The two systems in our bodies which control the functions of organs and tissues are the ________________ system and the _______________ system.

8.4 – Adjustments to Stress

Psychology: the science that investigates mental processes and behaviour.

Physiology: the study of the function of living systems.

Are the two related? Intertwined?

Stress...

Of course!

Like any other human, you are affected by both physiological and psychological factors.

How?1) The exterior environment2) Your internal environment (bodily functions)

NERVOUS SYSTEM ENDOCRINE SYSTEM

Nervous system: increases heart rate and diverting blood to more important parts of the body. (Immediate & short-lived)

Endocrine system: slower in response, but provide a more sustained response to stimulus. (Not as immediate but sustained).

Adjusting to Stress

Overall, stress hormones provide more _______ in order to cope with elevated ______ requirements brought on by stress.

Response to stress:

Primary stimulus for insulin secretion is a rise in blood glucose

Blood Glucose◦ Insulin release is inhibited during a stress response

if not, elevated blood glucose would not be sustained to deal with continued stress.

Blood pressure/volume◦ Renin-angiotensin-aldosterone pathway (increase

fluid volume)◦ Stress activates hypothalamus: release of ADH

(increase water reabsorption, and therefore, _____________________).

Stress Hormones

Problems with Long-term Stress

Read pages 389-391, and answer the following questionsa) How does the body compensate for strenuous exercise?b) How is caffeine similar to epinephrine?c) Define “anabolic steroid.” How do they enhance performance?

What are some limitations?d) What are a few of the health risks of using these drugs?e) What kinds of drugs have sharpshooters and archers used in the

past? Why?f) What is EPO? How would these drugs affect an endurance athlete?

(read chapter opener)g) What are some side effects of prolonged anabolic steroid use in

males and females?h) Choose three of the drugs in Table 3 and outline

a) Name of drugb) Advantagec) Side effects

Independent Reading

Page 392, #1-3.

Seatwork/Homework

Humans:◦ Separate male and female reproductive systems (sexual

reproduction). What is asexual reproduction?

◦ Gonads: both sexes! Males: testes sperm Females: ovaries eggs

Sperm (gamete) + Egg (gamete) (fertilization) zygote

How many haploid chromosomes does one human GAMETE contain? ___________________________________.

Reproductive Hormones (8.5)

Fallopian tubeUterusOvaryCervixVagina

UreterTestisPenisEjaculatory duct

UrethraSeminal vesicleprostate

Male Reproductive System (1)

Testosterone & andosterone:◦ Hormones produced by the interstitial cells of the

testes.◦ Testosterone: Stimulates spermatogenesis:

spermatogonia divide and differentiate into mature sperm cells.

◦ Influences the development of secondary male sexual characteristics (puberty):

Maturation of testes and penis Sex drive increased Facial and body hair Lower voice Stronger muscles Secretion of body oils (acne + body odor) Associated with sex driveHOW ARE EACH OF THESE SECONDARY

CHARACTERISTICS RELATED TO EVOLUTION? (survival of the fittest?)

Male Reproductive System (2)

Hypothalamus + pituitary gland controls the production of sperm/male sex hormones in the testes.◦ (-) feedback ensures that sperm cell count and

testosterone levels are maintained.◦ Gonadotropic hormones: regulate testes function.

Follicle-stimulating hormone (FSH): stimulates the production of sperm cells in the seminiferous tubules.

Luteinizing hormone (LH): promotes production of testosterone by interstitual cells.

Male Reproductive System (3)

Hypothalamus secretes gonadotropin-releasing hormone (GnRH)

GnRH activates pituitary gland FSH and LH secreted FSH stimulates the production of sperm cells in the seminiferous tubules, LH stimulates interstitual cells to produce testosterone testosterone increases sperm production.

High levels of Testosterone inhibits LH production by deactivating hypothalamus (negative feedback) hypothalamus releases less GnRH LH production decreased less testosterone production.

(-) FEEDBACK LOOP FOR SPERM PRODUCTION!

Male Puberty

More complicated than the male reproductive system. ◦ Males: continue to produce sperm cells at

somewhat constant rate◦ Females: one egg matures 1/28 days.

Hormonal levels fluctuate through the reproductive years end at menopause.

Female Reproductive System

Ovaries: fibrous connective tissue and small groups of cells follicles.◦ Follicles: two types of cells

Primary oocyte Contains 46 chromosomes: undergoes meiosis and

transformed into a magur ovum. Granulosa cells

Provide nutrients for the ovum.

Oogenesis and Ovulation (1)

Each ovary contains 400,000 follicles at puberty◦ Usually one single follicle becomes dominant and

reaches maturity. ◦ Between approx. 12-50, about 400 eggs will

mature. ◦ Longer follicles live, the greater chance of

mutation.

Oogenesis and Ovulation (2)

Hormone (produced by pituitary gland) controlled by follicle development◦ Granulosa surrounding primary oocyte begin to divide.

Oocyte undergoes meiosis 1 secondary oocyte (23 chromosomes) Secondary oocyte contains 23 chromosomes and most of the cytoplasm. Polar body receives little cytoplasm and dies.

Secondary granulosa surrounding secondary oocyte develop Fluid-filled cavity is formed mature follicle pushes up against the outer

wall of the ovary outer surface bursts secondary oocyte released. OVULATION

Remaining granulosa remain in ovary and are transformed into the corpus luteum.

Corpus luteum secretes hormones essential for pregnancy Degenerates within 10 days if pregnancy does not occur

Secondary oocyte enters the oviduct and begins meiosis II completed after fertilization Division of cytoplasm and nutrients is unequal: one cell is the mature

oocyte/ovum. Other polar body deteriorates.

Follicle Development

Approx. Every 28 days. Four distinct phases:

◦ Flow phase◦ Follicular phase◦ Ovulatory phase◦ Luteal phase

Menstrual Cycle

Shedding of the endometrium◦ Menstruation◦ Only phase of female

reproductive cycle that is determined externally.

◦ Used to mark the beginning of the menstrual cycle. Approximately 5 days can vary.

◦ Endometrium: thick, blood vessel- rich tissue layer: optimal environment for implantation of blastocyst ( fertilized ovum)

Flow Phase

Development of follicles within the ovary. ◦ Days 6-13 of menstrual cycle. ◦ As follicle cells develop, estrogen is secreted as

follicle continues to develop, [estrogen] in blood increases.

Follicular Phase

Occurs around day 14 Egg bursts from ovary and follicular cells

differentiate into the corpus luteum

Ovulation

Development of the corpus luteum◦ Between days 15-28◦ Estrogen levels begin to decline when oocyte leaves ovary, but

are restored when corpus luteum forms. ◦ Corpus luteum: secretes both estrogen and progesterone

ESTROGEN: female sex hormone that activates the development of female secondary sex characteristics (breasts, body hair, thickening of endometrium)

PROGESTERONE: female sex hormone produced by ovaries that maintains uterine lining during pregnancy. Continues to stimulate endometrium and prepares uterus for an embryo. Inhhibits further ovulation and prevents uterine contractions.

IF FERTILIZATION DOES NOT OCCUR, CONCENTRATION OF ESTROGEN AND PROGESTERONE DECREASES causes weak uterine contractions endometrium pulls away from uterine wall shedding of endometrium = flow phase.

Luteal Phase

Hypothalamus-pituitary complex: regulates the production of estrogen and progesterone (hormones of the ovary).◦ Female Gonadotropins: FSH and LH regulate

control of hormones produced by the ovaries (estrogen and progesterone) Estrogen and progesterone act as negative feedback

regulate gonadotropins.

Hormonal Control of the Female Reproductive System

Signalled by the release of GnRH from the hypothalamus activates pituitary gland (storage of FSH and LH)◦ During follicular phase: ________ phase: FSH to the

ovary follicle development is stimulated follicles secrete estrogen initiates development of endometrium as estrogen levels rise, (-) feedback sent to pituitary gland to turn off FSH follicular phase ended.

◦ Rise in estrogen LH secretion rises and ovulation occurs.

Female Puberty

After ovulation, the remaining follicular cells are under the influence of LH◦ Transformed into a functioning corpus luteum

cells secrete both estrogen and progesterone increases development of endometrium negative feedback FSH and LH inhibited. Without gonadotropic hormones, corpus luteum

deteriorates estrogen and progesterone slowed menstration.

Corpus luteum