Anatomy and

Physiology The Endocrine System

The endocrine system includes anything that secretes hormones directly into body fluids.

Endocrine glands include: the thyroid, parathyroid, adrenal, kidney, hypothalamus, pituitary, pineal, pancreas, ovaries, testes, and thymus glands.

The function of the endocrine systems is to regulate metabolic pathways (chemical rxns, electrolyte balance, membrane transport, reproduction, & digestion) by secreting hormones.

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Some terms:

Hormone: a biochemical that affects a specific

metabolic pathway in another cell.

These are secreted into body fluids & blood.

These are mostly steroids and made from

cholesterol but some are amines, peptides,

proteins, and glycoproteins.

Target cells (or organs): cells or organs that receive

the hormone (cell that is affected). These cells have

binding sites (a.k.a. receptors) for specific

hormones.

Hormones are placed in 2 groups: Steroid hormones

and Nonsteroid hormones.

Steroid Hormones: lipid soluble, meaning they easily

pass (diffuse) thru membranes. These are formed

from cholesterol usually.

Nonsteroid hormones must bind to receptors of

target cells (do not diffuse thru membranes). These

are amines, peptides, proteins, and glycoproteins.

Hormonal Secretion Control:

This is done by negative feedback control.

Mechanism that regulates the production of hormones based on the accumulation of another substance along a metabolic pathway.

For example:

The adrenal gland produces chemical A which continues a pathway:

A BC D E

When E is accumulated, it prevents (or inhibits) the adrenal gland from producing A. This is a negative feedback mechanism.

http://faculty.clintoncc.suny.edu/faculty/Michael.G

regory/files/Bio%20102/Bio%20102%20lectures/e

ndocrine%20system/cortisol.gif

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The Endocrine

Glands and

Their Hormones

The Pituitary Gland:

found in the base of the brain

has 2 parts: anterior and posterior (based on the lobe of the brain in which it is found).

controlled by the hypothalamus (by releasing hormones)

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The Pituitary Hormones:

Anterior Pituitary Hormones:

Growth Hormone (GH): stimulates growth of

cells (increase in size & cell division).

Prolactin (PRL): stimulates and sustains the

milk production in new mothers.

Thyroid-Stimulating Hormone (TSH): controls

thyroid gland secretions and is partially regulated by the hypothalamus.

Anterior Pituitary Hormones (cont’d):

Adrenocorticotropic hormone (ACTH):

controls the hormone production of the

adrenal cortex. Stress may increase ACTH.

Follicle-stimulating hormone (FSH) and

luteinizing hormone (LH): are released in the gonads (testes and ovaries). These are

called gonadotropins.

The Posterior Hormones:

Antidiuretic hormone (ADH): decreases urine production by regulating the amount of water the kidneys excrete; therefore, regulating [water] in body fluids.

Oxytocin (OT): considered an antidiuretic; it stimulates the uterine muscles to contract (causing contractions & birth), lactation b/c it stimulates milk-producing glands, and milk ejection.

The Thyroid Gland and its hormones:

This is located on both sides of the larynx and in front of the trachea.

Thyroxine (a.k.a. T4 or tetraiodothyronine) has 4 atoms of iodine and Triiodothyronine (a.k.a. T3) has 3 atoms of iodine (is 5 times stronger). Both regulate the metabolism of carbs (stimulate their use), proteins (stimulate their production), & lipids (stimulate their breakdown).

Calcitonin: not technically a thyroid hormone (b/c of the location of production). This regulates the [Ca] and [phosphate ions] in the blood.

Thyroid

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The Parathyroid Glands and their hormones:

These 4 are found on the thyroid gland.

These secrete parathyroid hormone (PTH): increases blood [Ca++] and decreases blood [phosphate ion], affecting the kidneys, bones & intestines. This works with calcitonin and is regulated by the [ ] of these ions in the blood.

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The Adrenal Glands and their hormones: This is located on top

of the kidneys and

contains 2 portions:

adrenal medulla

(central portion)

adrenal cortex (outer

portion).

http://www.massgeneral.org/cancer/crr/types/endocrine/images/

adrenal_gland.jpg

The Adrenal Cortical Hormones:

Aldosterone: regulates the [mineral] in the blood, stimulating water retention and sustaining b.p. and volume.

Cortisol: a.ka. hydrocortisone, affects glucose, protein & fat metabolism.

Adrenal Sex Hormones: in males, a.k.a. adrenal androgens; in females, a.k.a. estrogens. These supplement sex hormones & stimulate gonad development.

The Adrenal Medulla Hormones:

Epinephrine (a.k.a. adrenaline) and

norepinephrine (a.k.a. noradrenaline) are

released simultaneously. These increase the

heart rate, increase heart contractions,

increase breathing rate, increase b.p.,

increase blood glucose levels, & decrease digestion causing the typical “fight or flight

reaction”

The Pancreas and its Hormones: This is found by the

stomach and has 2 functions: exocrine gland (secretes digestive juices) and endocrine (releasing hormones).

The endocrine section contains groups of cells known as the Islets of Langerhans which contain alpha cells (secrete glucagon) and beta cells (secrete insulin).

http://www.pancreatic.org/atf/cf/%7BA69EE36

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The Pancreatic Hormones:

Glucagon: produced by alpha cells;

stimulates the breakdown of glycogen and

amino acids. It raises [blood sugar] and is

regulated by a low blood sugar

(hypoglycemia).

Insulin: produced by beta cells; stimulates the liver to make glycogen, promotes the

transport of glucose into cells, stimulates protein synthesis and stimulates fat storage;

thus, it decreases [blood sugar] and is

regulated by a high blood sugar

(hyperglycemia).

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Blood

Sugar

Regulation:

Other

Endocrine

Glands

Pineal Glands:

This is found in the brain on the upper portion of the thalamus.

This secretes melatonin which regulates circadian rhythms (response to light and dark conditions of the environment. These rhythms dictate sleep patterns & seasonal cycles of fertility in some mammals.

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pineal_glands.jpg

Thymus Gland:

This is found between the

lungs (shrinks with age).

This secretes thymosins

which regulate the

production &

differentiation of white

blood cells, specifically

T cells (T lymphocytes)

http://www.besthealth.com/besthealth/bodyguide/reftex

t/images/Thymus_spleen.jpg

Reproductive Glands:

Ovaries: produce estrogens & progesterone

Testes: produce testosterone

Placenta: produces estrogens, progesterone

& gonadotropin

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ages/heat.jpg

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ges/female.jpg

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Heart: produces atrial natriuretic peptide

(stimulates urinary Na secretion).

Kidneys: produce erythropoietin (stimulates

the production of rbc’s).

http://www.nhlbi.nih.gov/health/dci/images/heart_interior.gif http://www.healthline.com/blogs/health_observances/upl

oaded_images/kidney-713543.jpg

Stress and Health:

Stress is defined as a condition that causes change in the internal environment (a physiological response that alters homeostasis).

A stressor is a factor that causes stress.

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Stress and Health: There are types of

stressors:

physical which can be temperature changes internally or externally, [O2] changes, injury, illness (infections), exercise, noise, etc.

psychological factors which include emotions, feelings (anger, joy, fear, grief, anxiety, depression, etc.), thoughts, losses, unpleasant and pleasant encounters, and sexual arousals/encounters.

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Response to stress: These are physiological responses, called general stress syndrome, which is an adaptation to general stress.

This is controlled by the hypothalamus which activates fight or flight rxns (increases epinephrine output).

The physical responses include:

Increased [blood glucose] levels

increased heart rate

increased rate of breathing

increased b.p.

air passage dilation http://www.google.com/imgres

Other hormones are increased in output as well: glucagons, GH (both increase use of

energy sources) and ADH (decrease urine

output, conserving water, & maintaining blood volume).

In addition, cortisol is increased which

decreases the # of lymphocytes (increasing

risk of infection/illness by lowering

resistance and increasing the risk of high b.p., GI ulcers and atherosclerosis).

REVIEW:

https://www.youtube.com/watch?v=WVrlHH14q

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Adaptations 2017 This slide show was developed by Dana Halloran,

Cardinal Mooney High School, Sarasota, FL.

Used with her personal permission,

adapted and amended by Rosa Whiting,

Manatee School for the Arts, Palmetto, FL.