D5 Hormones & Metabolism

Essential Idea: Hormones are not secreted at a uniform rate and exert their effect at low concentrations

By Henry Vandyke Carter - Henry Gray (1918) Anatomy of the Human Body (See "Book" section below)Bartleby.com: Gray's Anatomy, Plate 1180, Public Domain, https://commons.wikimedia.org/w/index.php?curid=567162

By Darren Aherne

Statement

D5 U1 Endocrine glands secrete hormones directly into the bloodstream.

D5 U2 Steroid hormones bind to receptor proteins in the cytoplasm of the target cell to form a receptor–hormone complex.

D5 U3 The receptor–hormone complex promotes the transcription of specific genes.

D5 U4 Peptide hormones bind to receptors in the plasma membrane of the target cell.

D5 U5 Binding of hormones to membrane receptors activates a cascade mediated by a second messenger inside the cell.

D5 U6 The hypothalamus controls hormone secretion by the anterior and posterior lobes of the pituitary gland.

D5 U7 Hormones secreted by the pituitary control growth, developmental changes,reproduction and homeostasis

D5 A1 Application: Some athletes take growth hormones to build muscles.

D5 A2 Application: Control of milk secretion by oxytocin and prolactin.

From IBO Biology Subject Guide, 2014

D5 U1: Endocrine glands secrete hormones directly into the bloodstream.

Endocrine glands are ductless glands that produce hormones and secretes them into the blood. Exocrine glands are glands that secretes its products in ducts which take it to its destination. Hormones are chemical messengers produced by endocrine cells and transported by blood.

Blausen.com staff. "Blausen gallery 2014". Wikiversity Journal of Medicine. DOI:10.15347/wjm/2014.010. ISSN 20018762. - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=28909220

D5 U1: Endocrine glands secrete hormones directly into the bloodstream.

Types of Hormones:

Image from Allott & Mindorff, OUP, p. 694

Type of endocrine hormones Examples

Steroids Testosterone, progesterone

Proteins Insulin, leptin

Tyrosine derivatives thyroxine

Endocrine glands secrete hormones directly into the bloodstream, which carries them to target cells. Target cells have special receptors that react to the hormone as it passes.

Image Removed

D5 U2: Steroid hormones bind to receptor proteins in the cytoplasm of the target cell to form a receptor–hormone complex.

Steroid hormones are derived from cholesterol, so they are lipid soluble. Therefore they diffuse across the cell membrane.

Steroid receptors are generally located in the cytoplasm of the cell.

From Addison, Westley, Longman, 1999, retrieved from https://sites.google.com/site/accessrevision/biology/endocrine-system/types-of-hormones-and-their-interaction-with-receptorsFrom: http://archive.cnx.org/contents/6a9c625b-d5b0-4d6b-af2e-6cd922a7fdec@2/types-of-signal-molecules

1. Steroid passes through plasma membrane & binds to receptor proteins in the cytoplasm

2. Hormone-receptor complex moves into nucleus through nuclear pore

3. And binds to a specific regulator site on the DNA

4. Causing specific genes to be transcribed (or repressed)

5. Since hormones are not released at a continuous rate, the gene is not always active, and the transcribed mRNA & translated polypeptide is not always found in same amounts.

From http://highered.mheducation.com/sites/dl/free/0072421975/196644/steroid_hormone_action.html

D5 U3: The receptor–hormone complex promotes the transcription of specific genes.

Review- The Lac Operon

https://highered.mheducation.com/sites/9834092339/student_view0/chapter15/the_lac_operon.html

From Mr. Anderson at Bozeman Biology: https://www.youtube.com/watch?v=10YWgqmAEsQ

D5 U4: Peptide hormones bind to receptors in the plasma membrane of the target cell.

Peptide hormones are usually hydrophilic, so they cannot easily pass through the hydrophobic part of the plasma membrane.

From: https://courses.lumenlearning.com/ap2/chapter/hormones/

D5 U5: Binding of hormones to membrane receptors activates a cascade mediated by a second messenger inside the cell.

• Water soluble hormone is a primary messenger

• It binds to a hormone receptor on the surface of the plasma membrane.

• Causing a conformational change• Activating a G-protein• Leading to a increase in the

concentration of a secondary messenger, which is often cyclic adenosine monophospate (cAMP).

• Secondary messenger (cAMP) activates a specific enzyme (kinases)

• Which causes a cascade of cellular responses

http://highered.mheducation.com/sites/0072943696/student_view0/chapter10/animation__second_messenger__camp.html

D5 U6: The hypothalamus controls hormone secretion by the anterior and posterior lobes of the pituitary gland.

From: http://www.animationoptions.com/photobphi/hypothalamus-and-pituitary-gland

From: http://www.rickrichards.com/chakras/pituitary_brain2a.jpg

The hypothalamus is located at the base of the brain. It connects the nervous system to the endocrine system. The pituitary gland is located just below it.

http://highered.mheducation.com/sites/0072943696/student_view0/chapter10/animation__hormonal_communication.html

Posterior lobe of the pituitary

• The hypothalamus has neurosecretory cells connected to the posterior lobe of the pituitary.

• The hormones (ADH & oxytocin) are transported through the axons to the posterior lobe and released directly into the blood

Hormone Main target Effect

ADH

(Antidiuretichormone)

kidneys Increases reabsorptionof water in kidneys and hence decreases production of urine and increases blood pressure

Oxytocin Mammary glands, uterus

Stimulates uterine contractions & the release of breast milk

Anterior lobe of the pituitary

• Neurosecretory cells in Hypothalamus produce hormones called releasing factors into capillaries in the hypothalamus.

• The releasing factors travel directly to capillaries in the anterior pituitary through portal veins

• Causing the release of various protein hormones

https://www.youtube.com/watch?v=ZI0u0MoNoz0

Anterior lobe of the pituitary

Hormone Main target Effect

ACTH(adrenocorticotropic hormone)

Adrenal glands Stimulates the adrenal cortex, to release aldosterone and cortisol which increase blood pressure and metabolism respiration

GH (Growth Hormone)

Many tissues Increases height, controls levels of muscle and fat

TSH (Thyroidstimulating hormone

Thyroid Stimulates release of thyroxine which affects metabolism, heart rate, and body temperature

Prolactin Mammary glands

Stimulates production of breast milk

FSH (Follicle stimulating hormone)

Ovaries (women), and testes (men)

Stimulates follicle growth and production of estrogen, stimulates sperm production

LH (Luteinizing hormone)

Triggers ovulation and the formation of the corpus luteum, stimulates the production of testosterone

D5 U7: Hormones secreted by the pituitary control growth, developmental changes, reproduction and homeostasis

Hormones secreted by the pituitary affect the release of hormones from other glands. • Growth: Growth hormone helps to increase height and muscle

mass• Reproduction: FSH & LH, prolactin affect the menstrual cycle and

sperm production, & the production of milk to feed babies. Oxytocin stimulates uterine contractions in childbirth

• Homeostasis: TSH, ACTH, ADH affect metabolism, body temperature, heart rate, & blood pressure

D5 A1: Application: Some athletes take growth hormones to build muscles.

• Growth hormone is known to cause growth in animals• GH can be produced synthetically.• GH injections can help children who do not produce enough• Some athletes inject GH to try to increase muscle mass.• Research is unclear if GH injections in adults cause increases

of muscle mass or strength.• It is illegal in most countries to take without a doctor’s

prescription.• There are side effects to too much GH including growth of

hands, feet, & jaw, sweating, and headaches.• Causes any tumors to grow faster too!• Rewards do not seem to outweigh the risks.

Before: Ronnie Coleman: From: https://www.quora.com/What-happened-to-Ronnie-Coleman-Why-cant-he-walk-anymore

D5 A2: Application: Control of milk secretion by oxytocin and prolactin.

• Producing milk costs a lot of energy and nutrition

• Only produced when needed after childbirth

• Prolactin stimulates the production of milk by the mammary glands

• Estrogen inhibits the production of prolactin

• After childbirth, estrogen levels go down, and prolactin production rises

• Nursing helps to release oxytocin, which helps maintain milk production

https://www.youtube.com/watch?v=cMhgFt1xT7c

Bibliography

20018762, BruceBlaus When using this image in external sources it can be cited as:Blausen com staff “Blausen gallery 2014” WikiversityJournal of Medicine DOI:10 15347/wjm/2014 010 ISSN. English: Pancreatic Tissue. See a Full Animation of This Medical Topic., October 8, 2013. Own work. https://commons.wikimedia.org/w/index.php?curid=28909220.

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http://highered.mheducation.com/sites/dl/free/0072421975/196644/steroid_hormone_action.html.“pituitary_brain2a.jpg (400×385).” Accessed February 6, 2017. http://www.rickrichards.com/chakras/pituitary_brain2a.jpg.Sarah Clifford Illustration. Overview of the Endocrine Function of the Pituitary Gland. Accessed February 6, 2017.

https://www.youtube.com/watch?v=ZI0u0MoNoz0.“The Lac Operon.” Accessed February 6, 2017.

https://highered.mheducation.com/sites/9834092339/student_view0/chapter15/the_lac_operon.html.“Types of Signal Molecules.” Accessed February 6, 2017. http://archive.cnx.org/contents/6a9c625b-d5b0-4d6b-af2e-

6cd922a7fdec@2/types-of-signal-molecules.Weem, Minka Peeters, Christopher Talbot, and Mayhofer. Biology. 4th ed. Australia: IBID Press, 2014.“What Happened to Ronnie Coleman? Why Can’t He Walk Anymore? - Quora.” Accessed February 6, 2017.

https://www.quora.com/What-happened-to-Ronnie-Coleman-Why-cant-he-walk-anymore.