Endocrine System Flashcards
Endocrine system
composed of glands that produce and secrete hormones
-slower, longer lasting effects compared to the nervous system
- affects a broader range of cells
Endocrine glands
secrete hormones (chemical messengers) into bloodstream
Hormones
chemical messenger that has an effect on a specific cell/organ
- Examples: insulin (pancreas), testosterone (testes), adrenaline (adrenal glands), human growth hormone (hGH)
- There are over 200 known hormones in humans
- Hormones are classified based on their composition
- One hormone molecule can trigger release of hundreds-thousands of other molecules
Function of hormones
- Growth
- Metabolism
- Immune response
- Regulate blood pressure
Hormone Action on Target Cells:
- Target cells have receptor proteins
- Hormones are distributed by bloodstream
- Hormones bind to specific receptors
- Target cell receives the chemical message
Lipid based hormones
- made of carbon-hydrogen ring structures (steroid hormones)
Water soluble hormones
- dissolve in water
- contain amino acid-type groups with polar side chains
- protein hormones
- Ex. epinephrine, hGH, thyroxine, and insulin
- Cannot diffuse across cell membrane because it is a large polar molecule
- Binds to receptor protein on surface of target cell
- Triggers a series of reactions that amplifies the signal inside the cell
- Called a cascade
Steroid Hormones
- lipid based hormones (a.k.a. lipid soluble)
- ex. testosterone, estrogen, cortisol
- Can easily diffuse through cell membranes
- Bind to receptor proteins inside the nucleus
- Hormone-receptor activates gene expression and synthesis of specific mRNA
- enter in through cell membrane and target nucleus
How steroid hormones work
Recall transcription produces mRNA for translation to a protein
- Hormone diffuses through membrane because it is lipid soluble
- Hormone binds receptor protein
- Hormone-receptor complex enters nucleus and activates gene (transcription occurs)
4-6. mRNA is translated to protein by the ribosome in cytoplasm
Cascade
One hormone molecule can trigger release of hundreds-thousands of other molecules
- Binds to receptor protein on surface of target cell
- Triggers a series of reactions that amplifies the signal inside the cell
Hormone Amplification
One hormone stimulates the release of many other molecules in the cell, ultimately a target molecule.
Ex. 1 molecule of epinephrine can produce millions of glucose molecules from glycogen storage
cAMP cascade
Epinephrine stimulates liver cells
Converts ATP to cyclic adenosine monophosphate (cAMP)
cAMP triggers an enzyme cascade
-high level of enzyme production
Enzymes breakdown glycogen into glucose, which enters bloodstream
Enzymes deactivate initial signal
Regulation of hormone signals
The Hypothalamus!!!!!!!!
- The hypothalamus receives sensory information from the nervous system
- After receipt of the signal, it secretes releasing hormones
- These are instructions for its neighbour, the pituitary gland, to release certain hormones
- Hypothalamus controls the pituitary gland
- Pituitary gland produces many hormones that stimulate endocrine glands throughout the body
- Called tropic hormones (signaling target glands to release other hormones)
- Together, the hypothalamus and pituitary gland maintain homeostasis
Nervous and endocrine system working together
- Homeostasis depends upon the close relationship of the nervous(CNS/PNS) and endocrine system(Glands, hormones).
- several chemicals act as both hormones and neurotransmitters (e.g., epinephrine)
- Nervous system structures can secrete hormones just as glands do (e.g., hypothalamus)
- Both systems have feedback loops
How the Hypothalamus and Pituitary work together
- The hypothalamus secretes a releasing hormone into the anterior pituitary to telling it to release a hormone
- Anterior pituitary releases 2nd hormone into bloodstream
- Stimulates a target gland somewhere else in the body to release 3rd hormone into blood
- 3rd hormone travels to another cell and produces an effect
- Like many hormones, this system is controlled by negative feedback
- Build up of 3rd hormone prevents further release of 1st two hormones
Controlling rate of metabolism
- The pituitary is controlled by the hypothalamus via releasing hormones. The pituitary itself secretes tropic hormones
- The hormones secreted by the thyroid gland help regulate the metabolic rate of the body through 2 hormones: thyroxine and calcitonin
- This affects growth and development as well
Thyroid Gland
- a.k.a the metabolic thermostat
- turn up: hyperthyroidism
- turn down: hypothyroidism
- Located below the larynx
- Made up of two lobes, one on each side of the trachea
- each corner has parathyroid gland
- anterior and posterior
Pituitary Gland
- Made up of two lobes: anterior and posterior
- 1 cm diameter
- Attached to hypothalamus by neurosecretory cells
- A neurosecretory cell is a neuron that releases a hormone at the final synapse. This hormone diffuses into the bloodstream through the capillaries
Releases tropic hormones for:
- Metabolism
- Growth
- Development
- Reproduction
Anterior Pituitary
- At the front
- Hormone synthesizing gland
- Produces tropic hormones: TSH, ACTH, PRL, hGH, FSH, and LH
- makes its own hormones, stimulating/tropic hormones
- Releasing hormones from hypothalamus go to the anterior pituitary and stimulate/inhibit the release of tropic hormones into the bloodstream
Posterior Pituitary
- At the back
- Part of the nervous system
- Does not produce hormones
- Stores and secretes the hormones ADH and oxytocin, which are produced in hypothalamus
- Antidiuretic hormone (arginine vasopressin) tells kidneys how much water to conserve.
- Oxytocin = love hormone, released during labor/reproductive purposes
Regulating Growth
- Human Growth Hormone (hGH)
- Secreted by anterior pituitary
- Affects almost every body tissue
- Most effects are tropic
- For example, it stimulate liver to secrete growth factor hormones
- Stimulates growth of bone and cartilage, protein production
hGH and growth factors increase…
- Protein synthesis
- Cell division and growth (cartilage, bone, muscle)
- Breakdown and release of fats
Gigantism
Cause: Pituitary gland secretes excessive hGH during childhood
Symptoms:
- large hands/feet
- thickening of toes/fingers
- prominent jaw/forehead
- deafness
- delayed puberty
Treatment: slowing production of hormone
- heart is monitored because it’s too big
Pituitary Dwarfism
Cause: deficiency in hGH production in childhood
Symptoms:
- small body proportions
- slow growth
Treatment: hormone replacement therapy (but not successful)
Acromegaly
Cause: overproduction of hGH in developed adults
- suddenly in adulthood, it can happen
Symptoms:
- softening and widening of bones and soft tissues
- enlarged feet and hands
- thick ribs
- headaches
- enlarged heart/kidneys
Treatment: drugs to lower or block production of hGH
Regulating Metabolism
- The Thyroid Gland a.k.a the metabolic thermostat
- Located below the larynx
- Made up of two lobes, one on each side of the trachea
Negative Feedback with the Thyroid Gland
- Hypothalamus secretes Thyrotropin Releasing Hormone that stimulates the anterior pituitary gland.
- Anterior pituitary releases TSH into bloodstream.
- TSH targets thyroid gland.
- Causes thyroid to secrete thyroxine (T4) into bloodstream which stimulates increased cellular respiration in target cells.
- High levels of thyroxine (T4) cause negative feedback on the pituitary and hypothalamus, shutting
down production of TSH or TRH
Thyroxine (T4)
- the 4 represents the 4 iodine molecules in the structure of thyroxine
- T4 increases metabolism of fats, proteins and carbohydrates
- Increase rate of cellular respiration in heart, skeletal muscles, liver and kidney cells
Hypothyroidism
Due to low production of thyroxine
Hypothyroidism In Adults
- Could be caused by autoimmune disease, radiation therapy, medication
- Weight gain: Thyroid producing less thyroxin, slows metabolism, don’t metabolize the food you eat as efficiently and you wont breakdown your fats in your body as fast as others
Symptoms:
- continually tired, feeling cold
- slow pulse rate
- Puffy skin
- hair loss
- Minor weight gain
Hypothyroidism In Children
- Due to failure of thyroid to properly develop (cretinism)
- Results in stocky, short individuals w/ possible delays in mental development
Hyperthyroidism
- Overproduction of thyroxine
- hypothalamus produces too much tRH
- or anterior pituitary is producing too much tSH
- Thyroxine stimulates metabolism = more ATP
Symptoms:
- Anxiety
- Insomnia
- Heat intolerance
- Weight loss
- Irregular heartbeat
- same in children and aults
Goitre
- Iodine in the diet (salt) is required to make thyroid hormones
- Insufficient iodine = thyroxine is not made and there is no negative feedback signal to the pituitary to stop the secretion of TSH
- this will make hypothalamus always release TRH and anterior pituitary will make more TSH
- Too much TSH = extremely high stimulation of thyroid
- Leads to enlargement of thyroid
- will become inflammed
- Great lake regions lack iodine in soil and water because it is fresh water, oceans have more iodine. Salt refiners add iodine to salt, making it iodized. Dairy and fish also contain iodine
Graves’ disease
- Same symptoms as hyperthyroidism
- Immune system attacks thyroid
- thyroid doesn’t know it’s producing T4, but it is, similar to hyperthyroidism
- Also producing swelling around eyes
- Can be treated with medication or removal of part of thyroid
- The antibodies produced by the immune system act like TSH, and activates the thyroid to produce hormones
Thyroid Gland and Calcitonin:
Calcitonin: Hromone secreted by Thyroid gland to Regulate calcium levels in the blood, which allows for bone cells to uptake the calcium from the blood
- antagonistic hormones are Calcitonin and PTH (if one is high, the other is low, act to reverse, if calcium is high calcitonin is released, is calcium is low, PTH is released)
Functions of calcium
- Bone/teeth formation
- Blood clotting
- Nerve conduction
- Muscle contraction
- vesicles for neurotransmitters
- When blood calcium levels are high, calcitonin is released
- Calcium is stored in the bones
If high blood calcium levels:
- Thyroid gland secretes calcitonin into blood
- Calcitonin allows bones to take in calcium, which is needed for bone development
- Body’s blood calcium levels will decrease back to normal
If low blood calcium levels:
- parathyroid glands secrete PTH (parathyroid hormone)
- PTH will act on bones (to release calcium from them, which can make them brittle, leads to osteoporosis
- Also acts on the kidneys, which help activate Vitamin D (Vitamin D helps the kidneys to absorb calcium so that it doesn’t go into urine and instead, to blood)
- Intestines also absorb calcium with their microvilli
Parathyroid Hormone (PTH)
- Produced and released by parathyroid glands
- 4 small glands on the thyroid
Also regulates blood calcium levels:
- When blood [Ca2+] is low, PTH is released
- stimulates 1) bone to breakdown calcium phosphate, 2) kidneys reabsorb calcium from urine, and 3) intestines to absorb more Ca2+ from the digestive tract
- All of the above increase blood [Ca2+], which turns off PTH production
Over secretion of PTH
Hyperparathyroidism causes bones to soften due to excess calcium released from the bone
- remember: its hyperPARAthyroidism
Under secretion of PTH
Hypoparathyroidism causes muscle cramps due to lack of calcium for muscle contraction, it is all absorbed into bone.
- remember: its hypoPARAthyroidism
- muscles start to cramp because they need calcium to function
- all calcium is being absorbed into bones
The Adrenal Glands
- pair of organs that regulate stress response and blood sugar levels
- Rest on top of the kidneys
- connected to kidneys
- deal with short and long term stress response
- can deal with epinephrine and norepinephrine
- can secrete cortisol
Composed of two layers:
- the adrenal medulla (inner layer) - short term stress
- the adrenal cortex (outer layer) - long term stress
- The medulla and cortex produce hormones that are different in structure and function
Adrenal Medulla (Inner Adrenal Cortex)
- In this case it acts as a hormone when released by the adrenal medulla
- Regulates Short-term Stress Response
- connection between endocrine system and nervous system
- short term stress response affects also the nervous system because since epinephrine and norepinephrine are released, they are hormones and neurotransmitters that affect it
Adrenal medulla produces:
- Epinephrine (adrenaline)
- Norepinephrine (noradrenaline)
- These hormones regulate “Fight, Flight or Freeze ” response
- Cause similar effects to the Sympathetic (autonomic) Nervous System
- Norepinephrine can act as both a neurotransmitter (messenger between neurons) and a hormone (affects activity of cells directly)
When you are jump scared…
- Stimulus occurs, the Amygdala interprets images and sound as stressful, which sends distress signal to hypothalamus
- Hypothalamus activates the sympathetic nervous system via autonomic nerves, carrying signal from hypothalamus to adrenal medulla glands, bypasses pituitary gland and through spinal cord
- Neurons stimulate adrenal medulla to secrete epinephrine and norepinephrine
- remember: adrenal medulla is responsible for making epinephrine and norepinephrine, NOT BRAIN - Triggers stress response – increase body activity
Results:
- Rapid release and effects due to nervous system control
- Effects last many times longer than nervous system effects
Short Term Stress Response
- Increased heartbeat and blood pressure
- Rise in blood glucose levels
- Energized muscles
- Dilated pupils
- ‘Fight, Flight or Freeze’
- Epinephrine is used because:
- Allergic reaction: hypotension low bp, low blood flow. Epinephrine constricts veins, heartrate increases, also relaxes the muscles of the airways so you can breathe
Adrenal Cortex
Regulating Long-Term Stress Response
- NO NERVOUS SYSTEM IMPACTED!!!!!!!
- releases ACTH- adrenal cortex hormone
- This releases glucocorticoids and mineralocorticoids
- Adrenal cortex produces:
- Glucocorticoids (↑ blood sugar)- Helps to maintain energy, too much is stored as fat, which is why there’s a link to weight gain
- Mineralocorticoids (↑ blood pressure)- helps to keep blood flowing because the area that has more minerals will attract water to it, making it more flowy, blood pressure up
- Glucocorticoids cause suppression of calcium absorption, slow wound healing, muscle weakness.
- Mineralocorticoids increase sodium absorption in the blood
- They trigger sustained physiological stress responses
Cortisol
- a glucocorticoid stress hormone
- most abundant glucocorticoid
- may increase chances of diabetes, anxiety
- Produced via the long-term stress response
- Releasing hormone stimulates secretion of adrenocorticotropic hormone (ACTH) from the anterior P.G.
- ACTH is released to stimulate cortisol release
- too much ACTH is long term stress response
- Causes adrenal cortex to release the stress hormone cortisol
- Cortisol breaks down muscle protein into amino acids
- Those Amino acids are then removed from the blood by liver
Then used to make glucose
Glucose is released to the blood - It also breaks down fat cells
Releases glucose - Increased levels of cortisol in the blood causes negative feedback that suppresses ACTH and its release
- Cortisol reduces allergic/inflammatory immune system responses caused from damaged tissues
- Raises blood glucose levels
Cortisone
- Cortisol reduces allergic/inflammatory immune system responses caused from damaged tissues
- cortisone is cortisol that is administered into body as medication
- given in a specific amount so body doesn’t get too much sugar but just enough to reduce inflammation. The energy from the sugar is used for repair and mitosis
- allows for increase of circulation
- Cortisone is a drug given in many instances to reduce inflammation or allergic response
- Cortisone injections are sometimes given to patients with arthritis to help reduce the inflammation.
Aldosterone
- Main mineralocorticoid
- too much minerals in blood is caused by aldosterone, this gets more water from kidneys, which increases blood pressure
- Stimulates kidneys to increase Na+ absorption to blood
- Increase [] of solutes in blood
- Draws more water from kidneys
Addison’s Disease
- Due to damage of adrenal cortex
- cannot make hormones for long term stress response
- Insufficient glucocorticoid and mineralocorticoid secretion
- Results in low blood sugar (hypoglycemia), sodium and potassium imbalances, and weight loss
- low blood pressure
- tired
The Pancreas
- pancreas functions in the digestive system (produces enzymes to breakdown food) and endocrine systems (hormones: insulin and glucagon)
- has beta cells (deals with releasing insulin) and alpha cells (deals with releasing glucagon)
- Connected to the intestines by the pancreatic duct
- Over 2000 clusters of endocrine cells, called the islets of Langerhans, scattered throughout the pancreas
Islets of Langerhans
- Over 2000 clusters of endocrine cells, called the islets of Langerhans, scattered throughout the pancreas
secret antagonistic hormones:
- insulin (secreted by beta cells) lowers blood glucose by making target cells more permeable to glucose
- if blood sugar is too high, happens after eating a meal, beta cells in pancreas release insulin which goes to liver so that it stores extra glucose as glucagon.
- Insulin also goes to muscle cells to uptake extra glucose
- Insulin goes to fat tissue to store extra sugar
- this lowers blood sugar back to normal
- glucagon (secreted by alpha cells) increases blood glucose by stimulating the liver to convert glycogen to glucose
- If blood sugar is too low, alpha cells in pancreas release glucagon, which goes to fat tissue to break it down to glucose
- also goes to liver to break down glycogen
- Recall: calcitonin and PTH are also antagonistic hormones (opposite effects)
Diabetes Mellitus
- beta cells of pancreas deteriorate and fail to produce adequate amounts of insulin
OR - Cells do not properly to react to the insulin and the blood sugar level rises above normal
- This is known as hyperglycemia
There are two forms of diabetes mellitus
- Juvenile
- Adult or late-onset diabetes
Type 1 diabetes
- Juvenile diabetes
- diabetes Mellitus
- before the age of 20 years
- caused by early degeneration of the beta cells in the pancreas
- immune system attacks and destroys the beta cells
- Daily injections of insulin are necessary to replace the missing insulin
- also known as insulin dependent
- Injections are administered by the patient subcutaneously, why?
- since insulin is a protein hormone and would be digested if given orally
Type 2 Diabetes
- Adult or late-onset diabetes
- Diabetes Mellitus
- Around 90% of diabetics develop the condition as adults.
Due to two potential factors:
1.) Cells in the body do not respond properly to insulin, not allowing them to take in glucose for metabolism
2.) Reduced insulin output by the beta cells of the pancreas
- Sulfonamide drugs are also prescribed to stimulate the beta cells to produce a little more insulin.
- Other drugs allow for cells to be more sensitive to insulin and respond properly to the presence of insulin
- Not necessary to give insulin and so this condition is also known as non-insulin dependent diabetes. can increase insulin production by pancreas with drugs
Reproductive System and Sex Hormones
- Male and females both have gonads (testes and ovaries) that produce reproductive cells.
- Males produce sperm
- Females produce eggs
- Sex hormones – control the development and function of the reproductive system or secondary sex characteristics
What type of hormone causes the fastest reaction?
protein/water-soluble hormones
- because the hormone only attaches to a receptor that causes a cascade event
- That’s why epinephrine is used as adrenaline, because it’s so quick
- targets all cells that has that specific receptor on it
Hypothalamus hormones vs. pituitary glands hormones
hypothalamus
- releasing hormones
- goes to pituitary gland
pituitary gland
- releases tropic/stimulating hormones
- goes through blood stream to go to specific glands
- glands release hormones
releasing hormone
GNRH- comes from hypothalamus
- after release, anterior pituitary gland releases: FSH and LH both in males and females
- In males, testes begin sperm production which releases testosterone
- In females, ovaries produce estrogen and progestrogen
