Endocrine System Flashcards
Hormone
an organic chemical produced by one set of cells that affect a different set of cells
Chemical messengers that influence the metabolism of the recipient cell
Hormone
has a specific organ/origin, and a target organ/gland or organs/Glands
And a specific action
Many hormones are proteins that are coded for by genes and synthesized within the cytoplasm by ribosomes
What happens to synthesized hormones?
they eventually get packaged into vesicles by the Golgi apparatus and secreted at the plasma membrane.
What are the two main categories of hormones
Peptides and steroids
Peptide hormones
can be derived from proteins, peptides, and catecholamines
act relatively quickly but are short lived
Steroid hormones
Derived from cholesterol by a series of metabolic reactions
Act more slowly because it takes time to synthesize new proteins than to activate enzymes that are already present in the cell
Where are steroid hormones stored
Fat droplets in the cytoplasm until their release at the plasma membrane
Which hormone can enter the cell and nucleus freely?
Steroid hormones can enter freely and do NOT need to interact with cell surface receptors
Once inside the cell, steroids bind to receptors and create a hormone complex
The complex activates specific genes that lead to protein synthesis
Which hormone type has a longer sustained effect on metabolism?
Steroid hormones do because the create new proteins for a cells
Endocrine glands
These are ductless and secrete their hormones in the bloodstream to be distributed throughout the body.
Exocrine glands
Have ducts and secrete their contents directly onto epithelial tissue
ex. salivary glands
Primary endocrine glands
Secrete hormones that chemically regulate body functioning
Hypothalamus, pituitary gland, pineal gland, thyroid gland, parathyroid gland, adrenal glands, and pancreas
Secondary Endocrine glands
The heart, kidneys, gonads (testes and ovaries), thymus
negative feedback loop
This functions like a thermostat and is how most hormones are regulated.
Homeostasis has a set-point or range it requires to maintain proper functioning
If something falls below the range, it triggers it to turn on like a thermostat. It will run until it is slightly above optimal range, and then shut off. It will turn on again if the levels detected are below the set-point.
How does ADH use a negative feedback loop?
Its action is dilute blood. Once the blood is dilute, the hypothalamus detects dilute levels and shuts off the release of ADH
positive feedback system
This enhances or increases the amount of hormone that is regulated
Oxytocin works in a positive feedback system during childbirth
Hypothalmus
The part of the brain that regulates the internal environment and homeostasis.
It controls heart rate, body temperature, water balance, and glandular secretions of the pituitary gland
pituitary gland
lies just below the hypothalamus and has an anterior and posterior portion.
Posterior pituitary
connected to the hypothalamus by a stalk-like structure. Overlap between the nervous and endocrine systems – store nuerosecretory - cells that respond to neurotransmitters and produce hormones that are stored in the posterior pituitary
Neurosecretory
nuerons in the hypothalamus that respond to neurotransmitters and produce hormones that are stored in the posterior pituitary.
The hormones pass from the hypothalamus through axons that terminate in the posterior pituitary
What two hormones are stored in the posterior pituitary from the axons endings?
ADH ( antidiuretic hormone also called vasopressin) and oxytocin
ADH
promotes the absorption of water from collecting ducts which receive urine produced by the kidneys
As blood becomes dilute, the hormone is no longer released until it is needed again.
Oxytocin
Made by the hypothalamus and stored in the posterior pituitary
Triggers uterine contractions during labor AND stimulates milk production in mammary glands for nursing
Anterior Pituitary gland
Three tiered relationship between the hypothamlus, anterior pituitary gland, and other endocrine glands
They hypothalamus produces hormones that travel to the APG, and then trigger the APG to make specific hormones that control the thyroid, adrenal cortex, and gonads
Then those glands make hormones using a negative feed back system that regulate the secretion of the appropriate hypothalamic hormone
what hormones does the endocrine system secrete?
Growth Hormone (GH)
Prolactin
Melanocyte stimulating hormone (MSH)
Thyroid stimulating hormone (TSH)
Andrenocorticotropic hormone (ACTH)
Follicle stimulating hormone (FSH)
Luteinizing Hormone (LH)
Growth Hormone
dramatically affects physical appearance)
the amount of this hormone determines height and bone structure of a person
Causes cell growth, cell division, and protein synthesis
impacts changes on skeletal muscles, liver, and bones
promotes growth of cartilaginous plates and causes osteoblasts to form new bone
Too much or too little GH cause what?
Too little - pituitary dwarf
too much - pituitary giant
Acromegaly
Too much growth hormones in adults that causes feet, hands and part of the face ( eyebrow ridges, chin, and nose) to become overly large
Prolactin
produced only during pregnancy, childbirth, and nursing
causes mammory glands to develop and produce milk
and plays a role in carbohydrate and fat production
Melanocyte Stimulating hormone
stimulates melanocytes (cells found in skin) to increase the synthesis of melanin – what makes the skin darker in the sun
Thyroid Stimulating hormone
stimulates the thyroid gland to produce T3 and T4
Often grouped together and BOTH contain Iodine - iodine is actively transported into the thyroid gland and can reach concentrations of more than 25 times greater than the blood.
Adrenocorticotropic Hormone (ACTH)
stimulates the adrenal cortex to produce cortisol
Gonadtropic hormones: FSH and LH
Stimulates the gonads - testes in males and ovaries in females
FSH- causes the development of a follicle on the ovary to mature before ovulation. ALSO increases estrogen production
LH- acts on the ovary to cause ovulation. ALSO triggers the release of progesterone
What does Luteinizing Hormone also trigger
the production on progesterone to increase potential for fertilization of egg and pregnancy
Thyroxin (T4)
the anterior pituitary produces TSH which stimulates the thyroid to produce thyroxin in a negative feedback loop
Increases thyroxin exerts feedback control over anterior pituitary, which ceases to make TSH
Goiter
When iodine is lacking in the diet the thyroid gland enlarges - caused by a relationship between the thyroid and anterior pituitary
When thyroxin is low, Anterior pituitary continues to make TSH, the thyroid responds by getting larger (goiter), but is isn’t effective because thyroxin can not be produced without iodine
Roles of Thyroxin
Increases metabolic rate in all cells
increases respiratory enzymes and oxygen uptake
NECESSARY for proper growth and delvelopent
congenital hypothyroidism
occurs in people who have low thyroid (hypo) function since birth.
Causes reduced skeletal growth, sexual immaturity, abnormal protein metabolism - this can lead to intellectual disabilities
Calcitonin
Tyroid releases calcitonin as well as thyroxin.
this hormone lowers levels of calcium in the blood and deposits them onto bones (osteoblasts)
** Opposes the action of the parathyroid hormone (PTH) which increases calcium levels in the blood and phosphate levels decrease.
Parathyroid gland
4 glands embedded on the surface of the thyroid gland
Produces Parathyroid Hormone
This hormone increases calcium levels in blood and decreases phosphate
How does the parathyroid work to increase calcium?
Stimulates increased absorption in the intestine
retains calcium by excreting phosphate at the kidneys
these work with osteoclasts - demineralizing the bones and increasing calcium in the blood. When calcium levels reach the appropriate level, PHT shuts off via negative feedback system.
Tetany
Caused by PTH not being produced in response to low calcium levels in the blood
a person shakes from continuous muscle contractions
Happens due to low blood calcium levels which causes increase excitability of nerves which fire spontaneously
Adrenal Glands
Located above each kidney
Each has an inner portion called medulla and outer portion called cortex
These have no physiological connection with each other other than hormonal
Adrenal medulla
Not essential to life and can be removed
secretes epinephrine and norepinephrine directly in the blood stream in times of stress
flight or fight reaction
blood glucose and metabolic rate increase, as do breathing and heart rate
increased circulation causes the muscles to have more stamina than usual
Epinephrine is used to stimulate a person in cardiac arrest
adrenal cortex
Essential to life
It makes glucocorticoids and mineralocorticoids
releases a small amount of male hormones and an even smaller amount of female hormones
Cortisol
the glucocorticoid responsible for the most activity
Under control of the Anterior pituitary hormone ACTH
Raises blood glucose levels in opposition to inulin
counteracts inflammatory response
Inflammation cause pain and swelling and cortisol can ease symptoms and and reduce inflammation
Aldosterone
mineralocorticoid that is not under control of the anterior pituitary
regulates sodium and potassium ions in the blood
primary target organ is the kidneys
promotes renal absorption of sodium and renal excretion of potassium
melatonin
produced primarily at night
receives nerve impulse to the pineal gland via optic tract
melatonin and the pineal gland are involved in daily cycles Called circadian rhythms ( people get sleepy at dark and wake with the light)
Nigh shifts, and travel can disrupt this
What two types of tissues are in the pancreas?
Exocrine tissue produces and secretes digestive juices via ducts into the small intestine
Endocrine tissue called pancreatic islets - produces and secretes insulin and glucagon directly into the blood stream.
Glucose
main energy source for cells and body and needs to remain in normal limits
insulin
secreted into beta cells of the pancreas when there is high blood glucose level which occurs right after eating
3 purposes of insulin
1) Stimulates liver, fat, amino acids to take up and metabolize glucose.
2) stimulates the liver and muscles to store glucose and glycogen
3) promotes the build up of fats and proteins and inhibits their use as an energy source.
What else does insulin do?
Insulin is a hormone that promotes the storage of nutrients so they are hand durning times of low blood glucose levels
Glucagon
is secreted by the pancreas by alpha cells in between eating and its effects are opposite of insulin
Stimulates the breakdown of nutrients and causes blood sugar to rise
Erythropoietin
the kidneys make this hormone that acts on bone marrow to release bed blood cells into the bloodstream.
without erythropoietin people can become anemic
People with kidney disease are often anemic
what hormones do the testes produce?
androgens - testosterone
what hormone do the ovaries make?
estrogen and progesterone
What controls the sex hormone secretions?
The hypothalamus and the pituitary gland control the hormonal secretions of the ovaries and testes through FSH, and LH
what are some functions of testosterone?
essential for normal development and functioning of the sex organs in males
necessary for the maturation of sperm
stimulates the growth of penis testes during puberty
responsible for muscular strength in males
causes growth of facial, body hair
Effects of estrogen and progestogen
at puberty stimulates the growth of the uterus and vagina
necessary for egg maturation in the ovary
responsible for secondary sex characteristics of female body hair and fat distribution
pelvic girdle enlarges
responsible for breast development and regulation of uterine cycle
“all sex hormones”
both males and females produce all sex hormones however the ratios are different.
Adrenal glands are responsible for making the opposite hormones that the gonads of the individual do not make
Thymus
reaches it largest size and is most active during childhood
With age it becomes less active and
