Chapter 16 - Endocrine System Flashcards
What does the endocrine system do?
Acts as a means of internal communication, coordinating the activities of the organ systems
What do the endocrine glands synthesize?
Chemical substances (hormones) directly into circulatory system
What do the exocrine glands secrete?
Substances transported by ducts
What glands and/or organs are included in the synthesizing and secreting hormone(s) process?
- Pituitary
- Hypothalamus
- Thyroid
- Parathyroid
- Adrenals
- Pancreas
- Testes
- Ovaries
- Pineal Gland
- Kidneys
- Gastrointestinal glands
- Heart
- Thymus
What determines specificity of hormone action?
Presence of specific receptors on or in the target cells
Where are the adrenal glands located?
On top of the kidneys and consists of the adrenal cortex and the adrenal medulla
In response to stress, what occurs in the adrenal cortex? What occurs in the blood stream?
Adrenocorticotropic hormone (ACTH) is produced by the anterior pituitary which stimulates the adrenal cortex to produce more than 2 dozen different steroid hormones (i.e. adrenocortical steroids or corticosteroids) - In the bloodstream, corticosteroids are bound to transport proteins (transcortins)
How do corticosteroids exert their action?
Determining which genes are transcribed in the nuclei of their target cells and at what rate
What are the 3 major classes of corticosteroids? Describe each:
1) Glucocorticoids
- Ex. cortisol and cortisone
- Involved in glucose regulation and protein metabolism
- Raise blood glucose levels by promoting protein breakdown and gluconeogenesis and decreasing protein synthesis
- Increase plasma glucose levels and are antagonistic to effects of insulin
- Release amino acids from skeletal muscles and lipids from adipose tissue
- Promote peripheral use of lipids and have anti-inflammatory effects
2) Mineralcorticoids
- Ex. Aldosterone
- Regulate plasma levels of Na and K, and the total extracellular fluid volume
- Causes reabsorption of Na and passive reabsorption of H2O in the nephron
- Results in increase in BV and BP
- Excess production results in hypertension (high BP)
- Stimulated by angiotensin II and inhibited by ANP
3) Cortical Sex Hormones
- In men and women, secreted in small quantities of androgens
- Men = produced in testes
- Too much in women = manly characteristics
What does the adrenal medulla do?
Produces epinephrine and norepinephrine - Belongs to class of amino acids known as catecholamines
What does epinephrine do (in adrenal medulla)?
Increases conversion of glucose to glycogen in the liver and muscle tissue, causing increase in blood glucose levels and increase in basal metabolic rate
- Inhibits digestion
What do both epinephrine and norepinephrine do?
Increase rate and strength of heartbeat and dilate/constrict blood vessels such that blood supply is increased to skeletal muscles, heart, and the brain but decreases blood supply to kidney, skin, and digestive tract
- Also, promotes release of lipids from adipose tissue
What does pituitary gland look like and where is it located?
Small, trilobed gland at the base of the brain
- 2 main lobes are anterior and posterior
- Third lobe is the intermediate lobe
- Hands below hypothalamus and is connected to it via the infundibulum
What does the anterior part of the pituitary gland to? What are the hormonal secretions regulated by?
Synthesizes both direct hormones which directly act on target hormones, and tropic hormones which stimulate other endocrine glands to release hormones
- Hormonal secretions are regulated by hypothalamus hormones called releasing/inhibiting hormones (factors)
Describe the 4 tropic hormones of the anterior pituitary:
1) Follicle-Stimulating Hormones (FSH): Causes maturation of ovarian follicles which in turn secrete estrogen in women; stimulates maturation of seminiferous tubules and sperm production in men
2) Luteinizing Hormone: Stimulates ovulation and maintenance of corpus luteum, and regulated progesterone secretion in women; stimulates interstitial cells of testes to synthesize testosterone in men
3) Adrenocorticotropic hormone (ACTH): Stimulates adrenal cortex to synthesize and secrete glucocorticoids and is regulated by corticotropic-releasing facotors (CRF)
4) Thyroid-stimulating hormone (TSH): Stimulates the thyroid gland to synthesize and released thyroid hormone, including thyroxine
Describe the 4 direct hormones of the anterior pituitary:
1) Prolactin: Stimulates milk production in mammary glands
2) Endorphins: Pain relieving neurotransmitters
3) Growth hormone (GH): Promotes bone/muscle growth, promotes protein synthesis and lipid mobilization and catabolism; deficiency in children leads to dwarfism and overproduction leads to gigantism; overproduction in adults leads to acromegaly
4) Melanocyte-stimulating hormone (MSH): Secreted by intermediate lobe of pituitary; unclear function in mammals; darkening of skin via induced dispersion of molecules of pigment in melanophore cells in frogs
What does the posterior pituitary do?
Does not synthesize hormones but stores and released peptide hormones oxytocin, and anti-diuretic hormone which are produced by the neurosecretory cells of the hypothalamus
What is hormone secretion stimulated by n the posterior pituitary?
By AP descending from the hypothalamus
What is oxytocin? What is it induced by?
Secreted during childbirth to increase strength and frequency of uterine muscle contractions
- Induced by suckling; stimulates milk secretion in mammary glands
What is anti-diuretic hormone? What is it induced by?
Increases permeability of nephrons collecting duct to water, promoting H2O reabsorption and increasing BV which increases BP
- Secreted when plasma osmolarity increased sensed by osmoreceptors in hypothalamus or when BV decreases as sensed by baroreceptors in the circulatory system
Where is the hypothalamus located and what does it do?
Located in the forebrain above the pituitary gland - receives neural transmissions from other parts of the brain and peripheral nerves that trigger specific responses from its neurosecretory cells which regulate pituitary gland secretions via a negative feedback mechanism and through actions of inhibiting/releasing hormones
How does the hypothalamus interact with the anterior pituitary?
Hypothalamic releasing hormones stimulate or inhibit secretions of the anterior pituitary
- Ex. GnRH stimulates AP to secrete FSH and LH
How does the hypothalamus interact with the posterior pituitary?
Neurosecretory cells in the hypothalamus synthesize oxytocin and ADH and transport them via axons into PP for storage/secretion
What does the thyroid do?
Affects function of nearly every organ system in the body
- Children = essential for growth and neurological development
- Adults = increase rate of metabolism and maintain metabolic stability
