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DAT - Biology > Chapter 16 - Endocrine System > Flashcards

Chapter 16 - Endocrine System Flashcards

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1
Q

What does the endocrine system do?

A

Acts as a means of internal communication, coordinating the activities of the organ systems

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2
Q

What do the endocrine glands synthesize?

A

Chemical substances (hormones) directly into circulatory system

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3
Q

What do the exocrine glands secrete?

A

Substances transported by ducts

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4
Q

What glands and/or organs are included in the synthesizing and secreting hormone(s) process?

A
  • Pituitary
  • Hypothalamus
  • Thyroid
  • Parathyroid
  • Adrenals
  • Pancreas
  • Testes
  • Ovaries
  • Pineal Gland
  • Kidneys
  • Gastrointestinal glands
  • Heart
  • Thymus
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5
Q

What determines specificity of hormone action?

A

Presence of specific receptors on or in the target cells

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6
Q

Where are the adrenal glands located?

A

On top of the kidneys and consists of the adrenal cortex and the adrenal medulla

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7
Q

In response to stress, what occurs in the adrenal cortex? What occurs in the blood stream?

A 
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)
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8
Q

How do corticosteroids exert their action?

A

Determining which genes are transcribed in the nuclei of their target cells and at what rate

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9
Q

What are the 3 major classes of corticosteroids? Describe each:

A

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

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10
Q

What does the adrenal medulla do?

A 
Produces epinephrine and norepinephrine
- Belongs to class of amino acids known as catecholamines
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11
Q

What does epinephrine do (in adrenal medulla)?

A

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

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12
Q

What do both epinephrine and norepinephrine do?

A

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

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13
Q

What does pituitary gland look like and where is it located?

A

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
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14
Q

What does the anterior part of the pituitary gland to? What are the hormonal secretions regulated by?

A

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)

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15
Q

Describe the 4 tropic hormones of the anterior pituitary:

A

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

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16
Q

Describe the 4 direct hormones of the anterior pituitary:

A

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

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17
Q

What does the posterior pituitary do?

A

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

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18
Q

What is hormone secretion stimulated by n the posterior pituitary?

A

By AP descending from the hypothalamus

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19
Q

What is oxytocin? What is it induced by?

A

Secreted during childbirth to increase strength and frequency of uterine muscle contractions
- Induced by suckling; stimulates milk secretion in mammary glands

20
Q

What is anti-diuretic hormone? What is it induced by?

A

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

21
Q

Where is the hypothalamus located and what does it do?

A

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

22
Q

How does the hypothalamus interact with the anterior pituitary?

A

Hypothalamic releasing hormones stimulate or inhibit secretions of the anterior pituitary
- Ex. GnRH stimulates AP to secrete FSH and LH

23
Q

How does the hypothalamus interact with the posterior pituitary?

A

Neurosecretory cells in the hypothalamus synthesize oxytocin and ADH and transport them via axons into PP for storage/secretion

24
Q

What does the thyroid do?

A

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
25
Q

What are the thyroid hormones?

A
  • Thyroxine (T4)
  • Thriiodothyronine (T3)

Both formed from thryroglobulin which is synthesized in the thyroid cells

26
Q

Describe the characteristics of the thyroid hormones:

A
  • T3 is 5x more potent than T4
  • T3 and T4 are transported via plasma proteins; 99.5% are bound to proteins but an unbound hormone may enter a cell and elicit a cellular response
  • All T4 is formed and secreted by thyroid gland; 20% of T3 is produced by thyroid gland
  • Majority of T3 is produced by conversion of T4 to T3 by enzyme-5’-monoodeiodase which is mainly found in the peripheral tissues
27
Q

What is hypothyroidism? Symptoms? In newborns?

A

Undersecretion or no secretion of thyroid hormones

Symptoms:

  • Slowed HR
  • Slowed RR
  • Fatigue
  • Cold intolerance
  • Weight gain

Newborns:

  • Cretisism
  • Mental retardation and short stature
28
Q

What is hyperthyroidism? Symptoms?

A

Overstimulation of thyroid hormones

Symptoms:

  • Increase MR
  • Excessive warmth
  • Profuse sweating
  • Palpitations
  • Weight loss
  • Protruding eyes
29
Q

What is an enlarged thyroid called?

A

Goiter = bulge in the neck

30
Q

How is hypothyroidism treated?

A

Supplementation of thyroid hormones via synthetic or animal derived products

31
Q

How is hyperthyroidism treated? What happens after?

A

Anti-thyroid hormones that suppress thyroids release of excess hormone or ablation of thyroid via radiation
- After ablation, thyroid no longer produces thyroid hormone and patient must take supplements for entire life

32
Q

What is calcitonin? Regulated by? Antagonist to?

A

Decreases plasma Ca concentrations by inhibiting released of Ca from the bone

  • Regulated by plasma Ca levels
  • Antagonistic to parathyroid hormone
33
Q

What type of organ is the pancreas? Describe each function:

A

Endocrine AND exocrine organ

  • Exocrine function = cells that secrete digestive enzymes not small intestine via a series of ducts
  • Endocrine function = small glandular structures (Islets of Langerhans) composed of alpha (produce/secrete glucagon) and beta (produce/secrete insulin) cells
34
Q

Describe the 2 endocrine hormones of the pancreas:

A

1) Glucagon: Stimulates protein and fat degradation, conversion of glycogen to glucose, and gluconeogenisis
- Serves to increase blood glucose levels
- Glucagon is antagonistic to insulin

2) Insulin: Protein hormone secreted in response to high blood glucose concentration
- Stimulates uptake of glucose by muscle/adipose cells and the storage of glucose in muscle/liver cells to lower blood glucose levels
- Stimulates synthesize of fats from glucose and uptake of amino acids
- Antagonistic to glucagon and glucocorticoids
- Underproduction = diabetes mellutus = hyperglycermia (high blood glucose levels)

35
Q

What are the parathyroid glands?

A

Four small, pea-shaped structures embedded in the posterior surface of the thyroid

36
Q

What does the parathyroid gland synthesize and secrete? What does it do?

A

Parathyroid hormone (PTH) which regulates plasma Ca concentrations

37
Q

How does PTH work?

A

Raises the Ca concentration in the blood by stimulating Ca release from the bone and decreasing Ca excretion in the kidneys

38
Q

In relation to the parathyroid hormone, what is calcium in the bone bonded to? How is it released? How does PTH compensate for this?

A

Phosphate

  • Breakdown of the bone results in released of phosphate and calcium
  • PTH compensates for this by stimulating excretion of phosphate via kidneys
39
Q

What is produced when blood volume falls? What is the glycoprotein produced?

A

The kidneys produce renin (an enzyme that converts plasma protein angiotensinogen to angiotensin I

  • Angiotensin I is then converted to angiotensin II which stimulates the adrenal cortex to secrete aldosterone which helps restore the blood volume by increasing Na reabsorption by the kidneys thus leading to increased fluid retention
  • Removes initial stimulus for renin production

Erythropoietin (EPO)

  • Stimulates RBC production
  • Normally produced in kidneys
40
Q

What does EPO cause?

A

1) Stimulation of stem cells to differentiate into rubriblasts (least mature erythrocytes)
2) Increased rate of mitosis
3) Increased release of reticulocytes from the bone marrow
4) Increase hemoglobin (HgB) formation, which results in the critical HgB concentration necessary for RBC maturity to be reached at a more rapid rate

41
Q

How is the stomach stimulated? What hormone?

A

Ingested food stimulates the stomach to release hormones

  • Gastrin: Carried through gastric glands and stimulates the glands to secrete Hal in response to food in the stomach
  • Pancreatic juice is secreted (exocrine portion of pancreas)
  • Secretin: Released by small intestine when acidic chyme enters stomach; secretin stimulates secretion of alkaline bicarbonate solution from the pancreas that neutralizes acidity of the chyme
  • Cholecystokinin: Released by small intestine in response to the presence of fats and causes contraction of the gallbladder and release of bile into the small intestine
  • Bile: NOT a hormone; involved in emulsification and digestion of fats
42
Q

What is the pineal gland? What does it do?

A

Tiny structure at the base of the brain that secretes melatonin
- Circadian rhythm

43
Q

What are the mechanisms of hormone action?

A

Hormones are classified on basis of their chemical structure into two major groups:

1) Extracellular receptors
2) Intracellular receptors

44
Q

Describe peptide hormones:

  • First messenger?
  • Second Messenger?
  • Cascade effect?
  • Inactivation of cyclic AMP?
A

Range from simple to short peptides (ADH), to complex polypeptides (insulin)

  • Act as first messengers; bind to specific receptors on surface of target cells and trigger a series of enzymatic reactions within each cell (the first may be conversion of ATP to cyclic AMP which is then catalyzed by enzyme adenylate cyclase)
  • Cyclic AMP acts as a second messenger; relays messages to extracellular peptide hormone to cytoplasmic enzymes and initiating a series of reactions in the cell
  • Cascade effect = With each step, hormones effects are amplified
  • Cyclic AMP activity is inactivated by cytoplasmic enzyme phosphodiesterase
45
Q

What are steroids?

  • Produced by?
  • Are they lipid soluble? What does this provide?
  • What does the receptor-hormone complex do? Induces what?
A

Hormones (i.e. estrogen, aldosterone) that belong to a class of lipid derived molecules with a characteristic ring structure

  • Produced by testes, ovaries, placenta, and adrenal cortex
  • Lipid soluble; cross phospholipid bilayer and enter target cells directly in order to bind to specific receptor proteins in the cytoplasm
  • Receptor-hormone complex enters nucleus and directly activates expression of specific genes by binding to receptors on the chromatin which induces change in mRNA transcription and protein synthesis

DAT - Biology (16 decks)

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