Human Biology Endocrine System- Lakeland Community College
What stimulates the endocrine glands?
other hormones, humoral levels of a substance ( such as glucose or calcium), and nerve impulses
What kinds of processes do hormones control?
1. reproduction and growth development
2. mobilization of body defenses
3. regulation of metabolism
What is the function of the Endocrine system?
To secret hormones into the tissue, which secretes into the blood
Where are hormones produced?
by endocrine glands
How do Endocrine glands secrete hormones?
Endocrine glands secrete hormones into extracellular fluids
What are hormones?
chemical signals that affect other glands or tissues
What do hormones do?
regulate activity of cells elsewhere in the body
What are the possible effects of hormones on target cells?
2. growth and development
What are target cells?
cells that hormones act on. They have specific hormone receptors and respond when the hormone binds onto them
Where do hormones travel?
throughout the bloodstream
What are the two hormone categories?
1. amino-acid hormones (peptide hormones)
2. steroid hormones
How are amino-acid hormones different in their function?
amino-acid hormones (first messengers) binds to a receptor on the cell membrane because the hormone cannot enter the cell.
amino-acid hormones are not lipid soluble
How do amino acid hormones signal inside the cell?
They activate an enzyme that produces a second-messenger molecule inside the cell, which has an effect within the cell
How is the release of hormones maintained?
negative feedback system; when appropriate levels are reached, hormone release stops
How do steroid hormones move through the cell?
Diffusion; steroids are lipid-soluble
List the major type of hormones found in the body
What is a second messenger system?
molecules that relay signals received at receptors on the cell surface
Describe the function of an amino acid hormone (peptide hormone)
binds to the receptor protein on the plasma membrane and activates a second messenger system
** this leads to a large cellular response**
What types of hormones are steroids?
sex hormones and adrenal cortex hormones
What do steroid hormones do in the nucleus?
They bind to protein receptors: the receptor and protein then bind to the cell's DNA and activate genes, causing new proteins to synthesize
Describe the action of a steroid hormone
to bind to receptor proteins, this creates a hormone-receptor complex. the hormone receptor complex binds to DNA, activating particular genes. gene activation leads to the production of cellular enzymes that cause cellular changes
Describe hormonal stimulation of Endocrine glands
HINT: 3 different ways
1. humoral - concentration of dissolved substances or ions in the blood
2. by the actions of other hormones that stimulate of inhibit its release
3. the nervous system can make adjustment to maintain homeostasis
What are the major Endocrine glands?
What is the function of the hypothalamus?
The hypothalamus is the link between the nervous and endocrine systems
What is the function of the antidiurectic hormone (ADH)
Inhibits urine production (diuresis) by promoting water reabsorption of the kidneys (decreases urine volume, and increases blood volume) --> blood salt concentration is high
** controlled via negative feedback mechanisms**
location: posterior pituitary
What is another name for vasopressin?
antidiuretic hormone (ADH)
What is the function for oxytocin?
- stimulates uterine contractions during childbirth
- causes milk ejection in nursing women
location: posterior pituitary
What are the two parts of the pituitary gland?
posterior pituitary gland ( neurohypophysis)
anterior pituitary gland ( adenohypophysis)
What are the two hormones made in the hypothalamus, but stored in and released from the posterior pituitary?
2. antidiuretic hormone
Describe an ADH disorder
Diabetes insipidus: a condition which causes polydipsia and hyposecretion of ADH
What specific hormone acts on the anterior pituitary?
thyrotropin (TRH) -- releasing hormone
gonadotropin (GnRH) -- releasing hormone
corticotropin (CRH) -- releasing hormone
growth hormone (GHRH) -- releasing hormone
somatostatin -- inhibiting hormone
dopamine: prolactin inhibiting hormone and neurotransmitter
What inhibits the secretion of ADH?
alcohol --> can cause increased urine output and dehydration
What type of cells make ADH and oxytocin?
What are the six anterior pituitary hormones?
1. tropic hormones : stimulates other endocrine glands
2. growth hormone and prolactin : affect the body directly
3. thyrotropic hormone
4. adrenocorticotropic hormone
5-6. gonadotropic hormones
What is the function of the thyroid stimulating hormone (TSH)?
it influences the growth and activity of the thyroid gland, which stimulates metabolism
What is the function of the adrenocorticotropic hormone (ACTH)?
promotes secretion of the adrenal cortex hormones (stress respondents). Stimulated by corticotropin- releasing hormone from the hypothalamus
location: anterior pituitary
Describe gonadotropic disorders
Hyposecretion of FSH or LH leading to sterility in both males and females but hypersecretion does not appear to cause any problems
What are the two types of gonadotropic hormones?
FSH and LH --> regulation of hormonal activity of the gonads
Differentiate between FSH and LH
FSH: follicle stimulating hormones - stimulate follicle (egg) development in ovaries (secrets estrogens) and stimulates sperm development in testes
LH: luteinizing hormone - triggers ovulation of an egg in females (secrets progesterone) and stimulates testosterone production in males
location: anterior pituitary
What is the function of prolactin (PRL)?
stimulates and maintains milk production following childbirth. it works with oxytocin which allows the release of milk
location: anterior pituitary
What are the three growth hormone disorders?
1. pituitary dwarfism: hyposecretion of GH during childhood. the body proportions are normal, but the person does not grow taller than 4 ft tall
2. gigantism: hypersecretion of GH during childhood. Individual reaches 8-9 ft tall
3. acromegaly: hypersecretion of GH during adulthood. The long bones have stopped growing, which causes enlargement of lower jaw, brow, ridges, feet and hands
What is the purpose of the growth hormone?
determines the final body size by affecting the growth of bones and muscles.
also acts as a general metabolic hormone by promoting protein synthesis, fat breakdown and the maintenance of blood glucose homeostasis
Where is the thyroid gland found?
at the base of the throat
What is a goiter?
homeostatic imbalance when the thyroid gland enlarges due to a lack of iodine-thyroxine, negative feedback fails, thus preventing TSH production
What two hormones does the thyroid gland produce?
1. thyroid hormone
What is the thyroid gland composed of?
thyroxine (T4) - secreted by thyroid follicles
triiodothyronine (T3) - deals with conversion of T4 at target cells
What is the purpose of the thyroid hormone?
it controls the rate at which glucose is converted to body heat and chemical energy
*** every cell is a target***
List disorders of the thyroid hormone
1. congenital hypothyroidism --> the thyroid fails to develop properly occurring at birth. Individuals are usually short and stocky
2. Myxedema --> hypothyroidism in adults. Characterized by lethargy, weight gain, hair loss, slower pulse rate, lowered body temperature, thick and puffy skin
3. hyperthyroidism --> oversecretion of the thyroid hormone
What is an exophthalmic goiter?
edema in eye socket tissues. this causes swelling in the muscles that move the eyes
s/s:hyperactivity, anxiousness and irritability and insomnia
tx: surgical removal or destruction of part of the thyroid by radioactive iodine
What is Graves' disease?
an autoimmune disease characterized by s/s of cardiovascular disease, increased body temperature, fatigue, weight loss, depression, and mental confusion
What is the purpose of calcitonin?
decreases blood calcium levels
causes deposition on bone
**antagonistic to parathyroid hormone**
** production decrease in adulthood**
What is the purpose of the parathyroid glands?
to secrete parathyroid hormone (PTH) to raise calcium levels in the blood
1. stimulates calcium removal from bone
2. stimulates kidneys and intestines to absorb more calcium
3. activates vitsmin D (calcitriol) in the kidneys, which stimulates the reabsorption of calcium in the intestines
What happens if blood calcium levels fall too low?
parathyroid hormones releases PTH into the bones. Bones release calcium into the blood, kidneys reabsorb calcium from kidney tubules, intestines absorb calcium from digestive tract. blood calcium then rises
*hypocalcemia --> tetany (continual muscle spasms) results when there is insufficient secretion of PTH and blood calcium levels are low
What happens if blood calcium levels rise?
thyroid hormone secrets calcitonin in to the blood. bone absorbs calcium from the blood and than blood calcium lowers
*hypercalcemia --> can be due t o PTH oversecretion. causes weakness, abnormal heart rhythms, renal failure, coma and death
Where are the adrenal glands found?
on top of the kidneys
What are the two regions of the adrenal glands?
1. adrenal medulla: outer, glandular region with three layers
2. adrenal cortex: inner, neural tissue region
The adrenal medulla functions under what division of the nervous system?
symphatetic nervous system
What are the hormones of the adrenal medulla?
1. epinephrine (adrenaline)
2. norepinephrine ( noradrenaline)
What are glucocorticoids? What are their functions?
Hormones of the adrenal cortex
1. promote normal cell metabolism
2. help resist long-term stresses by increasing glucose levels
3. help control inflammation and pain
** it is released in response to increased blood levels of ACTH**
What is the purpose of the hormones of the adrenal medulla?
to cuase a "flight or fight" response
What hormone controls the adrenal cortex?
What are the three layer (hormones) of the adrenal cortex?
3. atrial natriuretic hormone
** provide long-term stress response**
Why is angiotensin ll produced?
in response to renin production
When is ANH produced?
in response to high blood volume/pressure
** inhibits the secretion of adolsterone
Describe the regulation of blood pressure and volume
high BP: heart secretes ANH into blood, kidneys excrete sodium and water in urine, thus causing a drop in BP
low BP: kidneys secrete renin into the blood, angiotension II coonstricts and causes the adrenal cortex to release aldosterone. The kidneys reabsorp sodium and water from kidneys tubules. Blood pressure then rises
List two disorders that occur as a result of the malfunctioning of the adrenal cortex
hyposecretion of adrenal cortex hormones. Acth causes increased melanin production. lack of cortisol means that glucose cannot be replenished under stress conditions. lack of adolsterone results in the development of low blood pressure and possibly severe dehydration
** a mild infection can be lethal**
caused by hypersecretion of adrenal cortex hormoes. excess cortisol may lead to diabetes mellitus. excess aldosterone leads to hypertension. edema causes a puffy "moon-shaped" face. increased male sex hormones may cause masculinity in females
What is the Endocrine function of the pancreas?
to maintain blood glucose homeostasis
What is the function of pancreatic islets?
to produce hormones scattered among enzyme-producing exocrine tissues
What does beta cells of islets do?
1. increase the ability to transport glucose across the plasma membrane
2. speeds up oxidation of glucose for energy or conversion to glycogen or fat for storage
What does alpha cells of islets do?
They are antagonistic to insulin. They stimulate the liver to break down glycogen to glucose
Describe the regulation of blood glucose levels
after eating the pancreas secretes insulin into the blood, liver stores glucose from blood as glycogen, muscle cells stores glycogen and build protein, adipose tissue uses glucose from blood to form fat, glucose levels drop
When is glucagon released?
What are the three endocrine tissue cell types?
1. glucagon: secreted by alpha cells
2. insulin: secreted by beta cells
3. somatostatin: secreted by delta cells ** prevents release of insulin and glucagon. prevents large swings of blood glucose levels**
What are the s/s of diabetes mellitus?
What are the two forms of diabetes mellitus?
Type I (IDDM)
Type II (NIDDM)
Type l Diabetes (IDDM)
insulin-dependent diabetes mellitus --> pancreas does not produce insulin. immune cells have destroyed the pancreatic islets due to an autoimmune response. individuals require daily injections of insulin
Type ll Diabetes (NIDDM)
non-insulin dependent diabetes mellitus --> more common than type I. tends to occur in obese individuals. normal or elevated amounts of insulin are present in the blood, but the receptors on the cells do not respond to the insulin
tx: exercise and maintaining normal body weight helps control it
What are the long term complications of diabetes mellitus?
blindness, kidney disease, heart attack, stroke, gangrene --> amputations
Where are the gonads located?
male: in the testes
What are androgens responsible for?
development of sex organs and characteristics --> continuous production of sperm
What stimulates the production of androgens?
anterior pituitary gonadotropic hormones
--> increased testosterone, some form of baldness, acne, body odor, facial, axillary and pubic hair, enlargement of larynx and vocal cords
What groups of hormones do the ovaries produce?
estrogen and progesterone
--> both necessary for breast development and regulation of uterine cycle
--> estrogen is needed for egg maturation, fat distribution, wider pelvic girdle, growth of uterus
What stimulates the production of estrogen and progesterone?
anterior pituitary gonadotropic hormones
Where is the thymus gland located?
posterior to the sternum
What happens to the thymus gland as we enter adulthood?
it decreases in size
What does the thymus gland produce?
What is the function of thymosin?
To help T lymphocytes mature --> this is important in developing the immune system
Where is the pineal gland?
hanging from the roof of the third ventricle in the brain
What does the pineal gland secrete?
** melatonin help the body's wake and sleep cycles. It peaks at night which causes sleepiness
production of red blood cells produced by the kidneys
produced by adipose tissue. signals satiety in the hypothalamus
produced by the stomach. antagonist to leptin, signaling hunger
List and describe several types of growth factors
granulocyte and macrophage colony stimulating factor - stimulates bone marrow stem cells
platelet - derived growth factor - wound healing
epidermal growth factor and nerve growth factor - wound healing
tumor angiogenesis factor - formation of capillary networks; released by tumor cells
What are some of the effects of prostaglandins?
mediate the effects of pyrogens (fever inducers)
reduce gastric secretions
lowers blood pressure
inhibit platelet aggregation (blood clot formation)
How do cells and organs communicate?
by using chemical signals --> hormones, prostaglandins, nerotransmitters, growth factors
Chemical signals between individuals are known as what?
List some of the effects the aging has on the Endocrine system
thyroid disorders (myexedema, Graves disease)
thymus and pineal glands decreases in size
The Endocrine works synonymous with what other system?
Aside from its own vital functions, what other functions does the Endocrine system help regulate?
blood pressure and volume
response to external environment ( "fight or flight")
regulate salt and water balance for blood volume and pressure
regulate carbohydrate, protein and fat metabolism to increase blood glucose levels. secreted in small amounts in both sexes.promotes skeletal growth, changes at puberty, libido
secreted when blood levels are low ( between meals)
** antagonistic to insulin