Chapter 16 - The Endocrine System Flashcards Preview

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Flashcards in Chapter 16 - The Endocrine System Deck (46)
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Exocrine Glands

Produce saliva, milk, HCl, for example.


Endocrine Glands

Release hormones into the blood and lymph nodes. Include following glands:



Chemical substances secreted by cells. They regulate metabolic funtions


Amino Acid based Hormones

Most of the hormones in the body.
-AA Derivatives: Catecholamines like epinephrine, dopamine, thyroid hormones, and melatonin.
-Peptide Hormones: Ex, ADH, oxytocin, GH, and prolactin



Lipid Derivatives. Structurally related to cholesterol.



Lipid derivatives, include prostaglandins.


Target Cell Specificity

Hormones only target specific cells which have the correct receptors on their membrane. The hormones then change the activity of the target cell.


Factors Influencing Target Cell Activation

1. The blood levels of the hormones.
2. The number of receptors on the target cell
3. The affinity of the hormone and the receptor


Mechanisms of Hormone Action

1. Produce a chance in the plasma membrane permeability or electrical state.
2. Synthesize proteins and enzymes
3. Produce enzyme activation or deactivation.
4. Induce secretion


Second Messenger System

Nearly all water soluble hormones cannot pass through the lipid membrane of a cell so they act through a second messenger. The hormone binds to a receptor on the membrane, which delivers a signal to an enzyme. The activated enzyme is the second messenger which converts ATP to cyclic AMP and this initiates a cascade of chemical reactions


Direct Gene Activation

Lipid soluble hormones, such as steroids, can pass right though the membrane and bind to receptors within the cytoplasm or nucleus. This interacts with chromatin where the hormones bind to the DNA protein and turns on DNA transcription of RNA to direct protein synthesis


Third Messenger

If calcium levels are changed by the second messenger system, it then acts as a third messenger.


Hormone Regulation

Synthesis and release of hormones is regulated by negative feedback where rising hormone levels inhibit further hormone release.


Hormonal Stimuli

Pituitary gland secretes ACTH hormone which stimulates glucocorticoid hormone secretion by the adrenal cortex. Once secreted, glucocorticoid influences various organs. Once the organs are influenced, it exerts a negative feedback on the adrenal cortex inhibiting ACTH production.


Humoral Stimuli

Level change of certain ions and nutrients which stimulates hormone release.


Neural Stimuli

Nerve fibers that actually stimulate hormone release.


Nervous System Control

Stimulus and feedback inhibitions can be moderated by the nervous system. The hypothalamus releases regulatory hormones into the blood to influence the activity of the anterior pituitary glad.


Pituitary Gland

Consists of 2 lobes. The posterior which is a storage area that receives hormones from the hypothalamus. The anterior which is the glandular part, it manufactures and releases 6 hormones. 4 are tropic, and control other endocrine glands, the other 2 on non endocrine targets. All work via second messenger systems.


Growth Hormone

Release by the anterior pituitary. Protein hormone whose main targets are the bones and skeletal muscle. Promotes protein synthesis, use of fats, and conservation of glucose. Hypersecretion causes giantism or enlargement of boy areas. , hyposecretion causes pituitary dwarfs.


Thyroid Stimulating Hormone

Released by the anterior pituitary. A stimulating hormone, it stimulates normal development and activity of the thyroid gland.


Adrenocorticotropic Hormone Releasing Hormone

Released by the anterior pituitary. Stimulates adrenal cortex to release corticorsteroid hormones to help resist stressors



Released by the anterior pituitary. Follicle stimulating hormone, FSH, and luteinizing hormone, LH. THey regulate the function of the ovaries and the testes.



Released by the anterior pituitary. A protein hormone, it stimulates milk production.



Stored in the posterior pituitary. A strong stimulant of uterine contractions and milk production.


Antidiuretic Hormine

Stored in the posterior pituitary. Chemical substance that inhibits and prevents urine formation. Can be inhibited by alcohol. Diabetes insipidus and diabetes mellitus can be caused by ADH mis production


Thyroid Gland

Locaed in the anterior throat. It's composed of hollow follicles that produce the glycoprotein thyroglobulin.The thyroid gland is unique because it has the ability to store and slowly release its hormones as needed. Thyroid hormone affects every cell in the body except for the brain, spleen, and uterus.


Thyroid Hormone

Major metabolic hormone. Actually 2 hormones, thyroxine (T4) and triiodothyronine (T3). Thyroxine is the major hormone, but it's all eventually converted into triiodothyronine.


Synthesis of Thyroid Hormone

1. Thyroblobulin forms on the ribosomes of follicle cells and is discharged into the lumen and stored.
2. Iodine from blood attaches to tyrosine, an AA, forming part of the thyroglobulin colloid.
3. Thyroglobulin is taken back into the cell by endocytosis and combined with a lysosome before being released into the blood


Thyroid Gland Diseases

Graves Disease - hyperthyroidism
Myxedema - hypothyroidism
Cretinism- severe hypothyroidism



Calcitonin. It's most important role is to control calcium levels.