A&P Chapter 16 Endocrine System

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The body`s second homeostatic control system?

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The body`s second homeostatic control system?

Endocrine System

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What system uses hormones as a control agent?

Endocrine System

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Chemical messengers released into the blood to regulate specific body functions


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Where are hormones secreted from?

Endocrine (ductless) glands and tissues

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The scientific study of hormones and the endocrine organs?


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Which system has these characteristics?


-Action potentials propagated via nerve fibers

-Neurotransmitters released at specific effector(s)

-Nerve impulses are brief (msec/sec), although control can be sustained

-Response of effecters is of relatively short duration(sec/min)

Nervous System

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Which system has these characteristics?


-Hormones released into body fluids; circulated throughout the body in the blood

-All body cells exposed; only target cells with receptors respond

-Hormones persist for seconds/hours/days

-Responses of target cells may last sec/hrs/day even months.

Endocrine System

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What kind of glands have:

-Have extensive capillary blood supply

-Form a discrete structure/organ

All glands

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What type of glands secrete hormones into surrounding tissue fluid by exocytosis and the blood transports them to target cells?

Endocrine Glands

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What type of glands secrete various compounds by exocytosis into a duct system?

Exocrine Glands

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What type of glands has both Endocrine and Exocrine functions?

Mixed glands

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What are the six pure Endocrine Glands?

  1. Pineal

  2. Pituitary

  3. Parathyroid

  4. Thyroid

  5. Thymus

  6. Adrenal Glands (Cortex and Medulla)

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Pancreas and Gonads (ovaries and testies) are a type of what kinds of glands?

Mixed glands

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What are seven types of Endocrine tissue?


2. Intestines

3. Skin

4. Adipose tissue

5. Heart

6. Kidneys

7. Placenta

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What is an example of Neuroendocrine "organs"?

Hypothalamus/Pituitary Glands

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Two types of Chemical Regulators?

Circulation Hormones (endocrines) and Local Hormones

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What is a Circulating Hormone and what does it do?

-Circulating hormone molecules linger in the bloodstream, and exert their effects for minutes or hours.

-Travel via the blood to reach all tissues, and may affect distant target cells

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What is a Local hormone and what does it do?

-Local Hormone molecules are usually short lived, and inactivated quickly.

-Diffuse into local interstitial fluid, reach and affect only local target cells.

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What are two examples of Local Hormones?

Paracrine and Autocrine

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Paracrine hormones do what?

Acts on target cells close to the site of release.

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Autocrine hormones do what?

Acts on the same cell which secreted it.

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How are Circulating hormones inactivated?

Inactivated by enzymes in the target tissues or in the bloodstream or in the liver; some hormones are also eliminated by the Kidneys.

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How would kidney or liver disease cause problems?

From increased hormone levels.

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What are the two main chemical classes of circulating Hormones?

  1. Amino Acid-based

  2. Steroids

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What are three types of Amino acids and what they are?

  1. Amines- From single amino acids

  2. Peptides- Short Sequences of amino acids.

  3. Proteins- Long chains of amino acids.

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What are steroids synthesized from?


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What are the five ways Hormones may alter cell activities and metabolism?

  1. Changing membrane permeability or membrane potential by opening or closing gated ion channels

  2. Synthesis of protein, lipids, or carbohydrates or certain regulatory molecules within the cell.

  3. Enzyme activation or deactivation.

  4. Induction or suppression of secretory activities.

  5. Stimulation of mitosis (and meiosis in the stem cells in the gonads)

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Since amino acid based hormones cannot enter cells, what must happen?

A 2nd messenger must convey the hormone signal inside of the cell (the hormone is the 1st messenger)

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What are 4 types of molecules that serve as second messengers and what are their functions?

  1. Cyclic AMP (cAMP)- Activates protein Kinases.

  2. Cyclic GMP (cGMP)- Inactivates protein Kinases.

  3. Inositol Triphosphate (IP3)- Increases [Ca2+]

  4. Ca2+ ions that bind to calmodulin.

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What are the 5 steps to Cyclic AMP (cAMP) for Hormone A?

  1. Hormone A (excitatory) binds membrane receptor, activating Gs.

  2. Gs stimulates adenylate cyclase (AC)

  3. AC forms cAMP from ATP.

  4. cAMP activates Protein Kinase A

  5. PKA: activates/deactivates other enzymes; stimulates cell secretion; opens ion channels.

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What are the 3 steps to Cyclic AMP for Hormone B?

  1. Hormone B (inhibitory) binds its membrane receptor, activating Gi

  2. Gi inhibits adenylate cyclase

  3. Antagonistic control

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Can two second messengers work together?

Yes, they will have twice as much activation.

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Second messengers activate/trigger what?

Activate Enzymes and triggers other intracellular activities.

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What are the three types of Hormone Interactions at a target?

  1. Permissive

  2. Synergism

  3. Antagonism

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What is a permissive hormone interaction?

One hormone allows another hormone to cause an effect.

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What is a Synergism hormone interaction?

Effect of two hormones acting together is greater than either acting alone.

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What is a Antagonism hormone interaction?

One hormone has an opposite effect to another hormone.

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What are the three types of Control of Hormone Release?

  1. Humoral control/ Autocontrol

  2. Nervous System control

  3. Hormonal Control

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What is hormone control (control of hormone release) and give an example.

-Hormones control the release of other hormones.

EX: Neurohormones from the hypothalamus stimulate the anterior pituitary to release hormones that stimulate the thyroid glands, the adrenal cortex, and the gonads to release hormones.

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What is Humoral control/Autocontrol (control of hormone release) and three examples of it?

-Substance in the blood regulate the release of the hormone.

EX: - Ca2+ levels in blood regulate PTH (Parathyroid hormone) release by the parathyroid gland.

-Glucose levels in blood regulate insulin and glucagon release by the pancreatic islets.

-Na+ and K+ levels in the blood regulate aldosterone release by the adrenal cortex.

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What is Nervous system control (Hormone release)?

Neural input stimulates the release of specific hormones.

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Three examples of Nervous system control hormone release?

  1. Sympathetic ANS stimulation of the adrenal glands cause them to release epinephrine and norepinephrine.

  2. Nerve impulses from the Hypothalamus cause oxytocin release from the posterior pituitary during labor or breast feeding.

  3. Nerve impulses from hypothalamus cause ADH release from the posterior pituitary then water concentration of blood declines.

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What are the two functional components of the Pituitary Gland (Master Gland)?

Anterior Pituitary and Posterior Pituitary

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What does the Anterior pituitary do, what it is made of and whats its other name?

Also called Adenohypophy, it`s primarily glandular tissue and it synthesizes hormones.

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What does the Posterior pituitary secrete, made of and what is its other name?

AKA Neurohypophysis, primarily neuosecretory cells (cell bodies in hypothalamus), secretes peptide hormones and has some support/glial cells.

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What is the Pituitary gland connected to and how?

Connected to the Hypothalamus by the infundibulum superiorly.

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What are the two Vascular linkages of the pituitary gland?

  1. Hypothalamus to the anterior pituitary.

  2. Two capillary beds- the hypophyseal portal system

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What are the two Nervous linkages of the pituitary gland?

  1. Hypothalamus to the posterior pituitary.

  2. Hypothalamic neuron axons

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What two parts of of the pituitary gland that regulates hormone release?

Anterior Pituitary and Posterior Pituitary

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How does the Anterior pituitary regulate hormone release?

Hypothalamic releasing and inhibiting hormones/factors transported via blood in the hypophyseal portal system.

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What are the two ways Posterior pituitary regulate hormone release?

1.Neuroendocrine release from neurosecretory cells

2.Hormones produced in hypothalamus and released from axons end bulbs in the posterior lobe.

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How is Grown Hormone (hGH) release?

-Stimulated by GHRH from the hypothalamus

-Negative feedback regulation by low blood levels of GH

-Inhibited by GHIH (somatostatin) from the hypothalamus.

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What are the actions of Growth Hormones?

-Targets especially liver, muscle, bone, cartilage, also most tissues

-Stimulates growth, mobilizes fats, elevates blood glucose (insulin antagonist)

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What are 2 pathologies of a growth hormone and examples of both?

  1. Hyposecretion- Pituitary dwarfism (Normal trunk/limb proportions)

  2. Hypersecretion:

    -Childhood: Pituitary gigantism

    -Adulthood: Acromegaly

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How is Thyroid stimulating hormones (TSH) released?

Release stimulated by TRH from the Hypothalamus and it is also indirectly stimulated by pregnancy and body temperature.

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How is Thyroid stimulating hormone release inhibited?

Inhibited by negative feedback from the thyroid hormones and GHIH (somatostatin)

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What are two actions of Thyroid stimulating hormones?

-Targets thyroid gland

-Stimulates thyroid hormone release. (T3 and T4)

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What are two pathologies of Thyroid stimulating hormones?

  1. Hyposecretion- hypothyroidism

  2. Hypersecretion- hyperthyroidism

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How is Adrenocorticotropic Hormone (ACTH) release stimulated?

Stimulated by corticotropin releasing hormone (CRH) from hypothalamus

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How is Adrenocorticotropic Hormone release inhibited?

Inhibited by negative feedback by glucocorticoids from adrenal glands (and by chronic use of therapeutic anti-inflammatory steroids)

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What does Adrenocorticotropic hormones target?

The adrenal cortex

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What does Adrenocorticotropic hormones stimulate?

Stimulates the release of glucocorticoids (and to a lesser degree gonadocorticoidss and mineralocorticoids)

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What are two pathologies of Adrenocorticotropic hormones?

  1. Hyposecretion- Addison`s disease

  2. Hypersecretion- Cushing`s disease (Pituitary tumor)

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How is Follicle stimulating hormone release stimulated?

Stimulated by gonadotropic-releasing hormone (GnRH) from hypothalamus

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How is Follicle stimulating hormone release inhibited?

Inhibited by negative feedback

-estrogen and inhibin in females

-testosterone and inhibin in males

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What does Follicle stimulating hormones target?

ovaries and testes

-in females stimulates ovarian follicle to mature and production of estrogen

-in males stimulates sperm production

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In which sex is Luteinzing Hormone found and what is it?

It is a Interstitial cell stimulating hormone found in males.

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How is Luteinzing Hormone release stimulated?

Stimulated by Gonadotropic-releasing hormone.

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How is Luteinzing Hormone release inhibited?

Inhibited by negative feedback:

-Estrogen and progesterone in females (except during Luteinzing Hormone surge)

-testosterone in males

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What does Luteinzing Hormone target?

Ovaries and testes

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What does Luteinzing Hormone stimulate?

In females- Ovulation and production of estrogen and especially progesterone

males- Production of androgens, testosterone

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How is prolactin release stimulated?

Stimulated by an unidentified prolactin releasing hormone (PRH) from the hypothalamus

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How is prolactin release enhanced?

Enhanced by estrogen, birth control pills and breast feeding.

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How is prolactin release inhibited?

Inhibited by dopamine and lack of neural stimulation (no suckling)

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What does prolactin target?

Breast secretory tissue

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What does prolactin stimulate?

Milk production for lactation.

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Six hormones of the Anterior Lobe?

  1. prolactin

  2. Luteinzing hormone

  3. Adrenocorticotropic hormones

  4. Follicle stimulating hormone

  5. Growth Hormone

  6. Thyroid stimulating hormones

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How is Oxytocin released?

Positive feedback:

-Uterine stimulation (stretch) and suckling stimulate the hypothalamus to release Oxytocin from the posterior pituitary.

*Increases feedback for more Oxytocin release

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What does Oxytocin release stimulate?

Uterine contractions and milk ejection/let down

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What does Oxytocin target?

Smooth muscle of the uterus and the breast

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How is Antidiuretic hormone (adh or vasopressin) release stimulated?

Stimulated by impulses from hypothalamus in response to

-Increased osmolarity (dehydration)

-Decreased blood volume or blood pressure


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How is Antidiuretic hormone release inhibited?

Inhibited by adequate hydration or ethanol ingestion

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What two places does Antidiuretic hormones target?

  1. Kidneys (adh effect)

    -Stimulates kidneys tubule cells to reabsorb water

    -NaCl (salt) will be conserved passively to some degree

  2. Vascular smooth muscle to constrict

    -Elevates blood pressure (vasopressin effect)

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Where is the Thyroid gland located?

In the anterior neck, inferior to the larynx (Adam `s apple)

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How many lateral lobes does the Thyroid gland have and what are they connected by?

Two lateral lobes connected by isthmus

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What is the largest pure endocrine gland in the body?

Thyroid gland

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Does the Thyroid gland have no blood supply or a rich blood supply?

Thyroid gland has a rich blood supply

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What kind of follicles does the thyroid gland have, what is it the production site for and what are they lined with?

Spherical follicles, lined with cubodial follicular cells and they are the production site of Thyroid hormones.

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What kind of hormones are produced at the spherical follicles in the Thyroid gland?

-Thyroxine (Tetreiodo-thyronine)


-Amine hormones

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What are they two main structures of the Thyroid gland?

Spherical follicles and Parafollicular (c cells)

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Where is the the Parafollicular located, what is it and what does it produce?

It is located between follicles, it is a protein hormone and it produces calcitonin (thryocalcitonin)

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What does the interior of the spherical follicle contain and what is that used for?

It contains the thyroid "colloid", which is the inactive storage form of thyroid hormones (thyroglobulin)

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What are the 4 hormones found in the Thyroid gland?

  1. Thyroxine

  2. Triiodothyronine

  3. Amine Hormones- unusual in penetrating its target cells to bind with cytoplasmic receptors.

  4. Tyrosine- formed from an amino acid (aa)

  5. *Two linked tyrosines with iodine atoms covalently bound

    -4 Iodine atoms- Thyroxine = Tetraiodothyronine

    -3 Iodine atoms- Triiodothyronine

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What does thyroid hormones target? (5)

Targets all tissues except adult brain, spleen, testes uterus and thyroid gland.

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How is thyroid hormones carried and how are they activated?

Carried in blood attached to a transport protein, only active when freed from the transport protein to diffuse into tissues.

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What does the Thyroid hormone stimulate?

Stimulates glucose metabolism

-Increases basal metabolic rate and body heat.

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What is Thyroid hormone an important regulator of?

helps regulate growth and development with hGH

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What does decreased levels of Thyroid hormone stimulate?


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What does hypothalamic TRH stimulate and what does that cause?

Stimulates the anterior pituitary to release TSH which stimulates the thyroid to release thyroid hormones

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What are the two thyroid gland pathologies and what do they do?


-Adults: Myxedema- lethargic, low metabolism, puffy eyes, mental impairment (If due to a lack of iodine, then a goiter- increased thyroid size)

-Infants: Cretinism- Short, thick body, mental retardation (improper development)

Could be in the thyroid gland or pituitary gland

Graves disease:

-Body produces autoantibodies, stimulates excess thyroid hormone production

-Causes elevated metabolic rate, sweating, rapid heartbeat, bulging eyes (Exophthalimia)

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