3 Endocrine System Flashcards
What are the major communication systems and what do they do?
Nervous system and Endocrine system
They are essential for homeostasis and coordinate and direct the activity of our cells
What are hormones and how do they function?
Hormones are chemical messengers that are secreted by endocrine glands directly into the blood. They bind to receptors on/in target cells
What are the possible effects of hormones binding to cell receptors?
Stimulate or inhibit mitosis or meiosis
Promote or inhibit secretion of a product
Activate or inactivate enzymes
Change plasma membrane permeability or membrane potential by opening/closing ion channels
Turn on or off transcription of certain genes
(SPACT)
How much of a hormone (quantity) is necessary to govern the activities of all the cells in our bodies?
Very small amount, pico amounts (10^-12)
What are some processes that hormones control?
Reproduction (estrogen)
Growth and Development (growth hormone)
Mobilization of body défenses against stressors (glucocorticoids)
Maintenance of much of homeostasis (ex: insulin and glucagon)
Regulation of metabolism (ex: thyroid hormone)
What are the two classes of hormones and how do they differ?
Amino-acid based hormones: most common, made of proteins, peptides amines, function through a second messenger system (exception: thyroid hormone)
Steroid hormones: made from cholesterol, function through direct gene activation
What are the steps to the process of direct gene activation?
- Steroid hormones diffuse through plasma membrane
- Hormone enters nucleus
- Hormone binds to specific protein
- Hormone-receptor complex binds to specific sites on the cells DNA
- Certain genes are activated to transcribe mRNA
- New proteins are made/synthesized
What are teh steps to the process of the second messenger system?
- Hormone (first messenger) binds to a membrane receptor
- Activated receptor sets off a cascade of reactions that activate an enzyme
- Enzyme catalyses a reaction that produces a second-messenger molecule (ex. Cyclic AMP, cAMP)
- Oversees additional intracellular changes to promote a specific response in the target cell
How does the endocrine system regulate itself?
Through positive and negative feedback mechanisms (homeostatic mechanisms)
What are the possible sources of activation of hormone glands? Define each of them.
Hormonal stimuli (most common): the endocrine gland is activated by another hormone
Humoral stimuli: changing blood levels of certain ions and nutrients stimulate a hormonal release
Neural stimuli (rare): nerve fibres stimulate hormone release, but most are under the control of the sympathetic nervous system
What are the function and location of the pineal gland?
Pea shaped gland in the center of the brain
Secretes melatonin and is believed to coordinate fertility hormones in humans and to inhibit the reproductive system until maturity/puberty occurs
What does melatonin do?
Believed to affect/trigger the body’s sleep and wake cycles
Where is the pituitary gland located?
Pea sized
Immediately inferior to the hypothalamus
Located behind the bridge of the nose
Protected by sphenoid bone
What is the pituitary gland divided into?
The anterior (glandular tissue) and posterior (nervous tissue) lobes
What is the function of the posterior pituitary lobe?
It does not produce hormones
Stores and releases peptide hormones produced in the hypothalamus
These hormones are delivered from the hypothalamus to the posterior lobe via neurosecretory cells
What are the hormones that the posterior pituitary gland stores for the hypothalamus? What do they do?
Oxytocin: released during child birth and in breastfeeding women
ADH: Antidiuretic Hormone, stimulates kidneys to reabsorb water into blood vessels away from forming urine
What effect does ADH have?
When more ADH is secreted, more fluid is retained, urine volume decreases, blood pressure increases (because of the constriction of artérioles)
What disease can hypo secretion of ADH cause? What are the symptoms?
Diabetes insipidus
Polyuria (excessive urination)
Polydipsia (excessive thirst)
What hormones control the activity of the anterior pituitary gland?
The releasing and inhibiting hormones released from the hypothalamus into portal circulation to reach the anterior pituitary
What type of hormones does the anterior pituitary release?
Peptide hormones
How are the hormones in the pituitary regulated?
Hormonal stimuli (from the hypothalamus) and through negative feedback
What hormones does the anterior pituitary gland secrete? (Very brief summary)
Growth Hormone (GH): bones and muscles
Prolactin (PRL): mammary glands
Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH): testes and ovaries
Thyrotropic hormone (TH): thyroid
Adrenocorticotropic hormone (ACTH): adrenal cortex
What hormones secreted by the anterior pituitary affect non-endocrine targets and how?
GH: targets growth of skeletal muscle and long bones
-plays a role in determining final body size
-causes amino acids to be built into proteins
-causes fats to be broken down for a source of energy
PRL: stimulates and maintains milk production following childbirth
-function in males in unknown
What are the hormones secreted by the anterior pituitary gland that affect endocrine tissues and what are they called?
FSH: stimulates follicle development in ovaries and sperm development in testes
LH: triggers ovulation of an egg and stimulates testosterone production in men
TH/TSH: stimulates growth and activity of the thyroid gland
ACTH: regulates endocrine activity of the adrenal cortex
These are tropic hormones
What is another name/category for LH and FSH?
Gonadotropic hormones
What are the anterior pituitary disorders we are responsible for? Briefly describe.
Gigantism: abnormally high secretion of GH in childhood
Acromegaly: high levels of GH in adulthood, causes bone to thicken but not lengthen
Pituitary dwarfism: insufficient production of GH in childhood (bones and muscles did not grow)
What are the components of the thyroid gland?
Left lobe
Right lobe
Isthmus (bridge)
Where is the thyroid gland located?
Base of the throat, inferior to the Adam’s apple
What are the hormones produced by the thyroid gland?
Thyroid hormone (major metabolic hormone) ((T4 and T3))
Calcitonin (regulate blood calcium levels)
What does thyroid hormone do?
Controls metabolic rate of oxidation of glucose to make body heat and chemical energy (ATP)
Needed for tissue growth and development
Maintains homeostasis
How does thyroid hormone maintain homeostasis (examples)?
Affects blood pressure
Heart rate
Digestion
Nerve function
Muscle tone
Reproductive function
What are the two hormones of the thyroid gland and their defining characteristic?
Thyroxine (T4)-> secreted by thyroid follicles
Triiodothyronine (T3)-> conversion of T4 at target tissue
They are iodine-containing
What are the steps in the homeostasis of metabolism (from hypothalamus to thyroid)?
- The hypothalamus is activated by a humoral stimulus (of low T3 and T4 levels in the blood) and begins to secrete TRH (Thyrotropin-releasing hormone) which is delivered to the anterior pituitary gland
- The pituitary gland responds by secreting TSH (Thyroid Stimulating Hormone) which bind to receptors in the thyroid gland to stimulate the production of T3 and T4 (thyroid hormones)
- T4 is primarily produced but is less active than T3. It’s converted into T3 in various tissues, especially the liver and kidneys
- T3 is the more active form and almost all cells in the body have receptors for it
What type of feedback loop is the homeostasis of metabolism and why?
Negative feedback loop
If levels of T3 and T4 are high, hypothalamus secretes LESS TRH
If levels of T3 and T4 are low, hypothalamus secretes MORE TRH
What does calcitonin do?
Decreases blood calcium levels by causing calcium deposition on bone
2 fun facts about calcitonin?
Antagonistic to parathyroid hormone
None or very little in adults
What are the disorders of the thyroid gland? Brief description.
Simple goiter: Enlarged thyroid gland, results from a diet deficient in iodine (needed for T3 and T4), can be treated by iodine supplements or administration of TH
Hypothyroidism: Under-secretion of TH, characterized by weight gaining, lethargy, memory loss, intolerance to cold and depression
Hyperthyroidism: Over-secretion of TH, characterized by increased metabolic and heart rate, sweating nervousness, weight loss, exophthalmos (protruding eyes from fluid accumulation)
Cretinism: too little TH in fetal development or infancy, dwarfism and delayed mental and sexual development
Where are the parathyroid glands located?
Four small round masses at the back of the thyroid gland that produce and secrete parathyroid hormone (PTH)
What does parathyroid hormone (PTH) do?
Increases blood calcium levels by:
-stimulating osteoclasts to remove calcium from bone
-stimulating the kidneys and intestine to absorb more calcium into blood vessels
What are two sets of antagonistic hormones?
Insulin and glucagon
Calcitonin and parathyroid hormone
What type of gland is the pancreas?
A mixed gland, has both endocrine and exocrine functions
What cells in the pancreas produce the antagonistic hormones responsible for blood glucose homeostasis?
Pancreatic islets produce insulin and glucagon
Specifically: Beta-> insulin and Alpha -> glucagon
When is insulin secreted and what does it do?
When blood glucose levels are high
Increases the rate of glucose uptake and metabolism by body cells
Lowers blood glucose levels
When is insulin secreted and what does it do?
Released when blood glucose levels are low
Stimulates the liver to release glucose to blood
Raises glucose levels
What are the symptoms of diabetes?
Polyuria (to flush out glucose and ketones)
Polydipsia (to replace H2O from urination)
Polyphagia (mellitus) (unable to use sugars and proteins and fats being lost)
What is diabetes mellitus? Causes and consequences?
Cause: inability to produce or use insulin causing spikes in blood glucose levels to rises dramatically
Consequence: kidneys are not able to reabsorb the glucose back into the blood fast enough so it spills into the forming urine
-water follows the glucose in the urine (osmosis) which creates more urine (polyuria) and causes dehydration (polydispia)
-cells break down fats and proteins to meet energy demands-> weight loss
-breakdown of fat results in acidic ketones->blood acidosis->coma->death
What is type 1 diabetes?
Form of diabetes mellitus, aka insulin dependant diabetes mellitus (IDDM)
Immune system destroys the pancreatic beta cells (no insulin production)
Treatment requires insulin injections
What is type 2 diabetes?
Also a form of diabetes mellitus, aka non insulin dependent diabetes mellitus (NIDDM)
Pancreas produces and secretes insulin but target cells have become less sensitive to insulin
Much more common than type 1
High glucose levels can usually be controlled by diet, exercise and weight loss
Sometimes reversible
What are the components of the adrenal gland?
Adrenal medulla:
-inside/inner layer, produces epinephrine and norepinephrine
Adrenal Cortex:
-outer layer, composed of (from outer layer to inner layer):
Capsule ->mineralocorticoid secreting area -> glucocorticoid secreting area -> gonadocorticoid secreting area
Where is teh adrenal cortex located?
Sits on each kindey
What types of hormones are produced y the adrenal cortex?
Corticosteroid hormones
What type of tissue is the adrenal medulla composed of?
Neural tissue
Whats an example of neural stimulation of an endocrine gland?
The neural tissue in the adrenal medulla
What is the main mineralocorticoid steroid secreted by the adrenal gland and by which part of the gland is it?
Aldosterone from the outer adrenal cortex called the mineralocorticoid secreting area
What does aldosterone do?
Regulates sodium and potassium ion content in blood
Regulated water and electrolyte balance
Targets the kidneys
Basically keeps things right in the kidneys
What are the main glucocorticoids produced by the adrenal glands and what part are they produced by?
Cortisone and cortisol
Middle layer of the adrenal cortex or the glucocorticoid secreting area
What are the main glucocorticoids and what do they do?
Cortisol and cortisone
Help resist long-term stressors by increasing blood glucose levels (providing energy)
Have anti inflammatory properties
Released in response to increased blood levels of ACTH (adrenocorticotropic hormone), the hormonal stimulus secreted by the anterior pituitary
What types of gonadocorticoids are released by the adrenal cortex and from which part?
Androgens and estrogens
Produced in the inner layer of the adrenal cortex aka the gonadocorticoid secreting area
Most of the hormones secreted are androgens but some estrogens are also formed
Small amounts are made throughout life in both male and female
What are some causes of high cortisol levels?
High blood pressure
High blood sugar
Insomnia
Hypothyroidism
Poor digestion
Decreased immune function
Constipation
Under normal conditions, how does the immune system respond to high cortisol levels? Does this occur under different conditions?
It terminates the inflammatory response to allow tissues to heal without further damage (excessive inflammation can cause damage)
If there are consistently high levels of cortisol this does not occur and inflammatory diseases can progress unchallenged
What hormones does the adrenal medulla secrete and what type are they?
Epinephrine and norepinephrine/ adrenaline and noradrenaline
Catecholamines
What stimulates the release of epinephrine and norepinephrine?
Nerve fibers of the sympathetic nervous system
Does the adrenal medulla deal with short or long term stress? Effects?
Short term: fight for flight type
How? Increasing heart rate, blood pressure, blood glucose levels, dilating passageways of lungs
What part of the adrenal gland is responsible for long term stress? What hormones?
The adrenal cortex
Glucocorticoids and mineralocorticoids
