A&P II Chapter 17.4-17.7 Learning Objectives

Identify the names and basic structures of the chemical classes to which various hormones belong (steroids, monamines, peptides)

Steroids: hormones synthesized from cholesterol

Peptide: most hormones, chains of multiple amino acids

Monoamines: one amino acid

--Includes catecholamines (dopamine, epinephrine, and norepinephrine), melatonin, and thyroid hormone

Compare and contrast the types of receptors that each class binds to

Peptides and catecholamines bind to cell surface receptors linked to second messenger systems

Steroids and thyroid hormone binds to receptors in the chromatin.

Describe how peptide hormones are synthesized and transported to their target organs

Peptides:

-The gene for the hormone is transcribed to form a molecule of mRNA

-Ribosomes translate the mRNA and assemble amino acids in the correct sequence to make the peptide.

-The rough ER and golgi complex further modify the peptide to form the mature hormone

Describe how monoamine hormones are synthesized and transported to their target organs

-Synthesized from the amino acid tryptophan (melatonin) or amino acid tyrosine (all other monoamines)

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Describe how steroid hormones are synthesized and transported to their target organs

Steroids are four fuse rings (based off) synthesized from cholesterol!!

Describe how hormones are transported to their target organ

A hormone must travel in the blood, which is mostly water.

For hydrophilic monoamines and peptides, this is easy.

Steroids and thyroid hormones have to bind to hydrophilic transport proteins (albumins and globulins synthesized by the liver) because they're hydrophobic.

Describe how hormones stimulate their target cells

Hormones stimulate only those cells that have receptors for them- their target cells.

The receptors are proteins or glycoproteins located:

-on the plasma membrane

-in the cytoplasm, or

-in the nucleus.

They act like switches to turn certain metabolic pathways on or off when the hormones bind to them.

Explain the second messenger/G protein coupled receptor system in the adenylate cyclase pathway

Adenylate Cyclase pathway (Fig 17.9a)

- Hormone > receptor > activated G protein >AC converts ATP to cAMP> activates protein kinase

Explain the second messenger/G protein coupled receptor system in the phospholipase C pathway

Phospholipase C pathway (Fig 17.9b)

-Hormone > receptor > activated G protein >Phospholipase C splits PIP2 > DAG & IP3

-DAG > activates protein kinase

-IP3 > increases Ca2+concentration > activates protein kinase

Target cell response depends on:

Hormone concentration

Concentration of receptors

Affinity of receptor to hormone

Influence exerted by other hormones

Permissive, synergistic and antagonistic effects

Note the signal amplification that occurs in the G protein/second messenger systems

Explain up-regulation

A cell increases the number of receptors and becomes more sensitive to the hormone.

Explain down-regulation

The process in which a cell reduces its receptor population and thus becomes less sensitive to a hormone.

Describe how hormones affect each other when two or more of them stimulate the same target cells

-Synergistic effects

-Permissive effects

-Antagonistic effects

Describe synergistic effects

Two or more hormones act together to produce an effect that is greater than the sum of their separate effects

Describe permissive effects

One hormone enhances the target organ's response to a second hormone to come later.

Describe antagonistic effects

One hormone opposes the action of another.

Discuss how hormones are removed from circulation after they have performed their roles

Hormone signals must be turned off when they have served their purpose

--> Most hormones are taken up and degraded by liver and kidney and then excreted in bile or urine

Give a physiological definition of stress

Any situation that upsets homeostasis and threatens one's physical or emotional well-being

Describe the three stages of the stress response

1. The alarm reaction- mediated by norepinephrine from SNS and epinephrine from the adrenal medulla.

2. The stage of resistance- the body provides alternative fuels for metabolism. Dominated by cortisol, which promotes the breakdown of fat and protein into glycerol, fatty acids, and amino acids.

3. The stage of exhaustion- often marked by rapid decline and death. The body relies on protein breakdown to meet energy needs because its fat stores are gone.

List the hormones released during short-term stress and describe their actions

Short term stress: epinephrine and norepinephrine.

Both increase blood glucose levels by stimulating glucose releasing by liver cells. Also increase oxygen availability to cells by increasing the heart rate and dilating the bronchioles

**They prepare the body for a "fight or flight" response by creating a burst of energy

List the hormones released during long-term stress and their actions

The hypothalamus triggers the release of ACTH from the anterior pituitary gland. The adrenal cortex is stimulated by ACTH to release corticosteroids, which turn on transcription of certain genes in target cells.

Two main corticosteroids: glucocorticoids (cortisol) and mineralocorticoids (aldosterone) which target the breakdown of fat into fatty acids in the adipose tissue.

Glucocorticoids stimulate the synthesis of glucose and inhibit the immune system

Mineralocorticoids regulate ion and water balance of the body by stimulating the kidneys to excrete less water and sodium ions in the urine

Discuss how the body adapts to stress through its endocrine and sympathetic nervous systems

SNS signals the adrenal glands to release epinephrine and cortisol.

Endocrine System: hypothalamus signs the pituitary gland to produce cortisol.

What are eicosanoids and how are they produced?

Eicosanoids are important family of paracrines (molecules that signal the functional status of neighboring islet cells)

-Derived from fatty acid called arachidonic acid

Lipoxygenase converts arachidonic acid into leukotrienes

-Leukotrienes are eicasnoids that mediate allergic and inflammatory reactions

What are the functions of eicosanoids

Prostacyclin: inhibits blood clotting and vasoconstriction (produced by walls of blood vessels)

Thromboxanes: override prostacyclin and stimulate vasoconstriction and clotting (ICE)

Prostaglandins (PG): relaxes smooth muscle in the bladder, intestines, bronchioles, and uterus and stimulates contraction of the smooth muscle of blood vessels.

Describe the physiological roles of prostoglandins

-Promote fever and pain (signs of inflammation)

-Mimic effects of TSH, ACTH, etc.

-Alter the release or effects of neurotransmitters in the brain

-Promote ovulation and formation of corpus luteum; induce labor contractons

-Inhibit gastric secretion

-Act as vasodilators and vasoconstrictors

-Constrict or dilate bronchioles

-Promote blood circulation through the kidney, increase water and electrolyte excretion

Explain how steroidal anti-inflammatory drugs like cortisol and corticosterone work and how NSAIDs

What are the general causes and examples of hormone hyposecretion and hypersecretion?

-Tumors or lesions that destroy an endocrine gland or interfere with its ability to receive signals from another cell

Describe diabetes insipidus

-Hyposecretion of Anti-Diuretic Hormone (ADH)

-Uncontrolled glucose-free urinewater loss (frequent urination and thirst)

-Can lead to diabetes mellitus

Describe Gigantism

-Hypersecretion of hGH BEFORE epiphyseal plate closure

-Body grows in proportion but abnormally tall

Describe pituitary dwarfism

too little GH is produced during childhood that results in small stature

Describe endemic goiter

-Enlarged thyroid gland due to a hyperactive thyroid and lack of iodide

-Results in elevated metabolic rate and heart rate, nervousness, sleeplessness, weight loss, bulging eyes, etc

Describe the causes and pathology of diabetes mellitus type 1 in detail

Cause: hyposecretion of insulin

Subjective Signs:

-excessive urine output

-intense thirst

-ravenous hunger

Objective Signs:

-increased blood sugar

-sugar and ketones in urine

*Usually affects younger population*

Pathology:

-basement membrane of blood vessels is thickened --> tissue degeneration, blindness, and renal failure

Describe the causes and pathology of diabetes mellitus type 2 in detail

*Usually affects people over 40 years old*

Cause: hypoactivity of insulin (insulin resistance: unresponsiveness of the target cells to the hormone)

Pathology:

-blindness and renal failure

-nerve damange

-erectile dysfunction, incontinence, and loss of sensation