Anatomy and Physiology: Endocrine hormones

Anterior Pituitary Gland

Location: hanging from hypothalamus in the brain; produces growth hormone, prolactin, follicle-stimulating hormone, luteinizing hormone, thyroid-stimulating hormone, and adrenocorticotropic hormone

Tropic Hormones

hormones that regulate the function of another endocrine gland

growth hormone - GH

target: bones and muscles

action: stim. growth and metabolism

regulated: hypothalamic hormones

prolactin - PRL

target: mammary glands

stim: milk production (lactation)

regulated: hypothalamic hormones

follicle-stimulating hormone - FSH

TROPIC

target: ovaries and testes

stim: production of ova and sperm

regulated: hypothalamic hormones

luteinizing hormone -LH

TROPIC

target: ovaries and testes

stim: ovaries and testes

regulated: hypothalamic hormones

thyroid-stimulating hormone - TSH

TROPIC
target: thyroid

stim: thyroid gland

regulated: thyroxine in blood

adrenocorticotropic hormone -ACTH

TROPIC

target: adrenal cortex

stim: adrenal cortex

regulated: glucocorticoids and hypothalamic hormones

posterior pituitary gland

location: base of brain, below hypothalamus

NOT an endocrine gland

FXN: acts as a storage area for hormones made by neurons in the hypothalamus

Hormones:

• oxytocin: stim. contraction of the uterus and milk letdown for lactation, regulated by the hypothalamus in response to uterine stretching and breastfeeding

• antidiuretic hormone (ADH): water retention of water thru kidneys, regulated by hypothalamus in response to water/salt balance

antidiuretic

chemical inhibiting urine production

causes kidneys to reabsorb water

urine volume decreases and blood volume increases

increases blood pressure

diuresis

urine production

alcohol and ADH

alc inhibits ADH secretion

dry mouth and intense thirst many hours after consuming alcohol

thyroid gland

location: front of neck; butterfly shape

hormones:

• thyroxine: hormones responsible for metabolism are regulated by TSH

• calcitonin: stimulates deposit of calcium salts from the blood into the bone

• thyroid hormone: T3 (active) and T4 (inactive), T3 functions for cell metabolism

metabolism

the chemical processes that occur within a living organism in order to maintain life.

maintenance of homeostasis

goiter belt

caused by iodine deficiency

thyroid enlargement

used to be common in midwest

parathyroid glands

location: on posterior side of thyroid gland (4 pea sized glands)

hormone: PTH produced; stimulates kidneys and digestive system to absorb more calcium ions from urinary filtrate and foodstuffs

PTH

stimulates the deconstruction of bone, therefore, depositing calcium into the blood via negative feedback

calcitonin

stimulates the deposit of calcium salts taken from the blood into the bone

PTH + Calcitonin relationship

when blood calcium levels are low, PTH breaks down bone to add calcium to blood. when bone calcium levels are low, calcitonin deposits calcium from the blood into bones.

adrenal gland - cortex

found on top of kidneys

produces corticosteroids

• mineralocorticoids: regulates mineral content in the blood, regulated by changes in blood volume/pressure

• glucocorticoids: increase blood glucose level and help the body resist long-term stressors (starvation), regulated by ACTH

• sex hormones:

  • estrogen: female sex hormone

  • androgen: male sex hormone

adrenal gland - medulla

center of adrenal gland on top of kidneys

produces catecholamines

• epinephrine + norepinephrine:

  • increased heart rate, blood pressure, blood glucose level, + dilate the passageways of the lungs

  • released when fight or flight of sympathetic nervous system is triggered

FXN: pumps hormones into bloodstream to enhance and prolong effects of neurotransmitters of the sympathetic nervous system

Short-term stress response: increase oxygen and glucose, as well as increase speed of blood to the body organs

pancreas

pancreatic islets: endocrine

pancreatic tissue: exocrine (part of digestive system)

Hormones:

• insulin and glucagon:

  • both regulated by the blood glucose level in the blood

  • insulin fxns to reduce blood glucose level

  • glucagon fxns to increase blood glucose level

• regulated by negative feedback system

• humoral stimuli

pineal gland

location: epithalamus

FXN to secrete melatonin to regulate biological rhythms

Melatonin:

• circadian rhythm: makes people drowsy, raises and falls during the course of the day; establishes body’s sleep-wake style

• coordinates the hormones of fertility: inhibits reproductive system until the body matures

thymus gland

location: upper thorax

dif in ages? adipose tissue replaces thymus gland during adulthood

hormones:

• thymosin: develops T-lymphocytes and immune response

regulated by hormones secreted by the pituitary and hypothalamus

ovaries

location: women’s pelvic cavity

hormones:

• estrogen:

  • stimulates uterine growth

  • develops and maintains secondary sex characteristics

  • controls menstruation

• progesterone:

  • during pregnancy, relaxes uterine muscles to protect baby

  • other secondary pregnancy characteristics

  • controls menstruation

testes

location: scrotum

regulated by the hypothalamic/pituitary/gonadal gland

fxn: production of sperm cells

Hormones:

• testosterone: aids in male development and health

• estrogen: produced in small amounts; aids in hormonal balance and production of sperm

placenta

temporary organ formed in the uterus during pregnancy

fxn: nutrition delivery, respiration, and excretion

hormones-only produced to have a role during pregnancy:

• hCG: stimulates ovaries to produce estrogen and progesterone

• hPL: works simultaneously with hCG to prepare for breastfeeding

• relaxin: causes pelvic ligaments and public symphysis to relax and become more flexible to prepare for birth

stomach

hormone:

• gastrine:

  • stimulates glands to release HCL

duodenum

hormones:

• intestinal gastrin:

  • Stimulates stomach gastric glands and motility

• secretine:

  • stim pancreas to release bicarbonate

  • stim liver: increases bile

  • stim stomach: reduces secreations and motility

kidney

• erythropoietin:

  • targets bone marrow to stim production of red blood cells

• active vitamin D3:

  • targets intestine to stimulate active transport of dietary calcium ions across intestinal cell membranes

heart

atrial natriuretic peptide (ANP):

• stim kidney to inhibit sodium ion reabsorption and renin release

• stim adrenal cortex to inhibit secretion of aldosterone which decreases blood volume/pressure

motility

food processing time

nervous system: messenger system, communication, timing, and body process

messenger system: first messenger

communication: impulses

timing: quickly (sec/millisec)

body process: short term movement in response to stim

endocrine system: messenger system, communication, timing, and body process

messenger system: second messenger

communication: hormones

timing: slower (min/days)

body process: long term controls such as reproduction and homeostasis

hormone function

1. reproduction

2. growth + development

3. body defense mobilization

4. maintenance of homeostasis

5. metabolism regulation

6. controls long term continuous processes

hormone classifications

1. amino acids

2. steroids

3. prostaglandins

two mechanisms in which hormones trigger changes in cells

1. direct gene activation

2. second-messenger system

direct gene activation

LIPID SOLUBLE:

1. steroid hormone diffuses through plasma membrane of target cell

2. hormone enters nucleus

3. hormone binds to receptor protein

4. hormone-receptor complex binds to the DNA

5. complex activates genes to transcribe mRNA

6. mRNA translation results in a new protein (hormone)

Second messenger system

1. hormone binds to embedded receptor protein

2. bond sets off reactions to activate an enzyme

3. enzyme triggers production of a 2nd messenger

4. 2nd messenger oversees intracellular process

* they are many 2nd messengers + possible target cell responses to the same hormone

control of hormone release

• hormone levels in the blood are mostly maintained by negative feedback mechanism

• a stim or low hormone levels in the blood triggers the release of more hormone

• hormone release stops once an appropriate level in the blood is reached

categories of activation types that triggers endocrine glands

(3 ways)

1. hormonal

2. humoral

3. neural

hormonal activation

def: most common, turned on by other hormones (hormone to hormone)

ex: hypothalamic hormones stim the anterior pituitary to secrete hormones

humoral activation

def: changing blood levels of ions and nutrients stimulate hormone release (blood levels to hormone)

ex: PTH released by decreasing Ca levels in the blood

neural activation

def: nerve fibers stimulate hormone release (nerve fibers to hormone)

ex: sympathetic nervous system stimulates the adrenal medulla to release norepinephrine and epinephrine during stress