Endocrine ii online

Copyright © 2011 Pearson Education, Inc.

ORGANS OF THE ENDOCRINE SYSTEM

Pituitary gland

Thyroid gland

Parathyroid gland

Adrenal gland

Pineal gland

Pancreas

Gonads


The Pituitary Gland

• “Hypophysis” = master gland / pituitary gland

• Pea sized gland

• In hypophyseal fossa of sphenoid

• Connect to hypothalmus via infundimulum

• Secretes several hormones


The Pituitary Gland

• Two lobes:

1. Posterior pituitary (lobe):

• Composed of nervous tissue

• Connected to hypothalmus

2. Anterior pituitary (lobe) (adenohypophysis)

• Glandular tissue

Anterior lobe

Posterior lobe


Posterior Lobe• Posterior lobe

• A downgrowth of hypothalums

• Hypothalums = emotional center


Posterior Lobe - Hormones

• Produced by hypothalamus…released by posterior lobe

• Oxytocin

• Stimulates contractions in childbirth

• Causes release of breast milk

• Antidiuretic hormone (ADH)

• Causes kidneys to reabsorb water


Anterior Lobe• Controlled by hypothalmus

• Secretes several hormones into blood stream


Anterior Pituitary Hormones

1. Growth hormone (GH)

2. Thyroid-stimulating hormone (TSH) or thyrotropin

3. Adrenocorticotropic hormone (ACTH)

4. Follicle-stimulating hormone (FSH)

5. Luteinizing hormone (LH)

6. Prolactin (PRL)

• Know names and abbreviations


Anterior Pituitary Hormones

• All are proteins (water soluble)

• Use cAMP to cause changes in cell

• TSH, ACTH, FSH, and LH are all tropic hormones

• Tropic hormones regulate other endocrine glands


Growth Hormone (GH)

• Targets bone and skeletal muscle

• Helps increase body mass

• Promotes protein synthesis

• encourages fat use


Imbalances of Growth Hormone

• Hypersecretion

• In children results in gigantism

• In adults results in acromegaly

• Hyposecretion

• In children results in pituitary dwarfism

gigantism

acromegaly


• Stimulates the activity of the thyroid

• Negative feedback controls production

Thyroid-Stimulating Hormone (Thyrotropin)


Adrenocorticotropic Hormone (Corticotropin) (ACTH)

• Stimulates the adrenal gland to release corticosteroids

• Such as epinephrine

• External factors alter release

• fever, hypoglycemia, and stressors


Gonadotropins

• Regulate gamete production in gonads

1. Follicle-stimulating hormone (FSH)

2. Luteinizing hormone (LH)

• FSH stimulates gamete (egg or sperm) production

• LH promotes production of gonadal hormones

• Present after onset of puberty


Prolactin (PRL)

• Stimulates milk production

• Blood levels rise toward the end of pregnancy

• Suckling stimulates PRH release and promotes continued milk production


THYROID GLAND

Metabolism control

•Thyroid hormone

•Calcitonin


Thyroid Gland

• Located in the throat inferior to Adam’s apple

• produces thyroid hormone

• To make thyroid hormone you need iodine

• thyroglobulin + iodine = thyroid hormone


Thyroid Hormone

• Major metabolic hormone

• Increases metabolic rate and heat production

• Plays a role in:

• Maintenance of blood pressure

• Regulation of tissue growth

• Development of skeletal and nervous systems

• Reproductive capabilities


Synthesis and Regulation of Thyroid Hormone

• Cells require iodine to synthesize TH

• Regulated by negative feedback

• TH inhibits TSH production


Homeostatic Imbalances of TH

• Hyposecretion in adults — goiter formation

• Enlarged thyroid

• Caused by lack of iodine

• Iodine fortified salt

• Hypersecretion — Graves’ disease

• Antibodies mimic TSH

• Too much TH produced

• Protruding eyes.

Copyright © 2011 Pearson Education, Inc. Figure 15.10

goiter


Calcitonin

• Also produced by thyroid

• Lowers blood calcium (Ca2+ )

• Inhibits osteoclasts

• Causes calcium absorption into urine

• Production triggered by high blood Ca2+


PARATHYROID GLANDS


Parathyroid Glands

• tiny glands embedded in posterior thyroid

• Secrete parathyroid hormone (PTH)

• PTH — important in Ca2+ levels


Parathyroid Hormone (PTH)

• Functions opposite to calcitonin

• Produced when low blood Ca2+ levels

• Stimulates osteoclasts

• digest bone release Ca2+

• Kidneys resorb Ca2+

• Negative feedback regulation:

• rising Ca2+ inhibits PTH release


ADRENAL GLANDS


Adrenal Glands

• Location: suprarenal = above the kidneys

• Two main regions

• Adrenal cortex — glandular tissue

• secrete corticosteroids

• Adrenal medulla — nervous tissue

• Sympathetic nervous system

• Secrete epinephrine


Corticosteriods

• Three types produced:

1. Mineralocorticoids – Aldosterone

2. Glucocorticoids – cortisol / cortisone

3. Gonadocorticoids – sex hormones


Mineralocorticoids

• Regulate electrolytes (primarily Na+ and K+)

• blood volume, blood pressure

• Aldosterone potent mineralocorticoid

• Na+ reabsorption / water retention by kidneys

Glucocorticoids

• Cortisone and cortisol

• Helps resist stressors

• Helps regulates blood sugar


Imbalances of Glucocorticoids• Hypersecretion —Cushing’s syndrome

• Depresses the immune system

• Promotes changes in cardiovascular, neural, and GI function

• Preparing for stress

• weight gain

• Hyposecretion — Addison’s disease

• Weight loss, severe dehydration, and hypotension


Gonadocorticoids

• Sex hormones = androgens (male sex hormones)

• In tissues converted to testosterone or estrogens in females

• Contribute to:

• Onset of puberty

• Secondary sex characteristics


Adrenal Medulla

• Secretes epinephrine and norepinephrine

• hormones cause “fight or flight”

• Blood diverted to brain, heart, and skeletal muscle

• glucose levels rise

• Blood vessels constrict

• heart beats faster


PINEAL GLAND AND PANCREASE


Pineal Gland

• Small gland hangs from roof of third ventricle

• Secretes melatonin…derived from serotonin

• Melatonin affects

• sexual maturation

• Day/night cycles

• body temperature, sleep, appetite


Pancreas

• Has exocrine and endocrine cells

• Produce pancreatic juice for digestion (exocrine)

• Produce hormones (endocrine)

• Regulate blood sugar

• cells produce glucagon

• when “glucose is gone”

• cells produce insulin

• When blood glucose is high


Glucagon / Insulin

• Glucagon targets liver:

• Gluconeogenesis — produces glucose from glycogen stores

• Releases glucoses into blood

• Insulin targets tissues

• Causes uptake of glucose into cells

Copyright © 2011 Pearson Education, Inc. Figure 15.18

Liver

Liver

Tissue cells

Stimulates glucose uptake by cells

StimulatesglycogenformationPancreas

Pancreas

Insulin

Bloodglucosefalls tonormalrange.

Stimulatesglycogenbreakdown

Bloodglucoserises tonormalrange.

Glucagon

Stimulus Bloodglucose level

Stimulus Bloodglucose level

GlycogenGlucose

GlycogenGlucose

Glucagon / Insulin


Diabetes Mellitus

• Low insulin signaling

• Low levels of production or low activity of insulin

• Symptoms

• Polyuria —huge urine output

• Polydipsia —excessive thirst

• Polyphagia —excessive hunger

• Hyperinsulinism:

• Too much insulin; hypoglycemia, can cause unconsciousness


GONADS

Ovaries, placenta and testes


Ovaries and Placenta

• Ovaries produce estrogens and progesterone:

• Maturation of female reproductive organs

• Female secondary sexual characteristics

• Breast development and mensturation

• Placenta secretes estrogens, progesterone, and human chorionic gonadotropin (hCG)

• Pregnancy tests look for hCG


Testes

• Produce testosterone

• Maturation of male reproductive organs

• Male secondary sexual characteristics

• Needed for sperm production


Other Organs Produce Hormones

• Kidneys

• Erythropoietin red blood cell production

• Adipose tissue

• Leptin appetite control

• Thymus

• Lymph cell development

• Heart

• Blood pressure and volume

• GI cells

• Stimulate digestion

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Endocrine ii online