CH 6, Part 1-2 Flashcards
Hormone
chemical messenger released by a cell, travels through the bloodstream, and finds another cell in the body to bind to
- can travel very long distance
- most often released from glands
Endocrine System
anything in the body that releases hormones
- whole system of glands
- glands: epithelial cells that come together and form sort of globular structure
3 stimuli that release hormones
(1) HUMORAL
chemical change (ion/nutrient) in bloodstream that causes tissue to release hormones
(2) NEURAL
if the nervous system is what tells a tissue to release its hormones
(3) HORMONAL
when hormones tell a tissue to release hormone
Tropic Hormone
hormone in which its sole function is to cause the release of other hormones in the body
- ex: thyroid stimulating hormone, adrenocorticotropic hormone, gonadotropins
Hormones released by Anterior Pituitary
THYROID-STIMULATING HORMONE (TSH)
signals thyroid gland to release thyroid hormone
ADRENOCORTICOTROPIC HORMONE (ACTH)
goes to the outer layer of the adrenal glands (adrenal cortex) to stimulate the release of aldosterone and cortisol
GONADOTROPINS
produced by the gonadotropic cells
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
go to ovaries and testes and tell them to release hormones
***next 2 act directly on target tissues
GROWTH HORMONE (SOMATOTROPIC HORMONE) (GH)
goes to liver, binds to liver, and triggers release of insulin-like growth factor-1 (IGF-1)
- similar to GH but has greater magnitude of effect in cause of growth of human body
- stimulates body growth directly in variety of tissues
- stimulates growth indirectly (tropic) by the liver’s secretion of IGF-1
PROLACTIN (PRL)
- goes to glands within breast and stimulates milk production
- not exclusive to women
Hypothalamus
controls the anterior pituitary entirely
- part of brain –> made of neurons
- in-series blood flow between the hypothalamus and anterior pituitary gland—hypothalamic portal vein
- blood vessels go hypothalamus –> anterior pituitary
- neurons within hypothalamus release chemical messengers (hormones) from axon terminal –> bloodstream
- chemical messengers –> anterior pituitary
- hormones released by neurons tell anterior pituitary to release hormones or not
Testosterone/estrogen loop
(1) Hypothalamus release Gonadotrophin releasing hormone (GnRH)
(2) GnRH travel through blood vessels to anterior pituitary
(3) tells anterior pituitary to release FSH and LH
(4) hormones travel to gonads and cause release of testosterone and estrogen
(5) testosterone and estrogen elevate in bloodstream
(6) when there are elevated levels, testosterone and estrogen travel back to hypothalamus
(7) they block neurons to inhibit them from being able to release GnRH
- without GnRH, anterior pituitary will not release FSH and LH
(8) gonads will not release testosterone and estrogen; therefore, their levels will fall and homeostasis will be maintained
(9) if testosterone and estrogen levels are low there is nothing to inhibit the hypothalamus, thus it will begin releasing GnRH
Anterior vs Posterior Pituitary
ANTERIOR
gland made of epithelial tissue that release hormones
- glandular (epithelial tissue) secretes hormones
POSTERIOR
NOT a gland, instead is part of brain
made of neurons that release hormones into the blood
- neurons (nervous tissue) release hormones
Hormones released by Posterior Pituitary
OXYTOCIN
- peptide
- positive feedback loops
- neural stimulus
- “letdown reflex”
- stimulus of sucking on breasts stimulates neurons to travel to hypothalamus and tell these neurons to release milk and oxytocin
- uterine contractions during childbirth
- stretching on uterus activate neurons which go to hypothalamus to release oxytocin to further stimulate more uterine contractions
VASOPRESSIN (ADH)
- peptide
- antidiuretic hormone: less urination to retain more water and slow dehydration
- humoral stimulus
- dehydrated –> high osmolarity of blood (low water, high solute), triggers neurons to release ADH
Different Hormones of Endocrine System
THYROID GLAND
- releases thyroid hormone
- ant. pituitary releases TSH –> thyroid and stimulates it to release thyroid hormone
- humoral stimulus
- hyperthyroidism: high thyroid hormone secreted, metabolism high
- hypothyroidism: low thyroid hormone secreted, metabolism low
- also releases calcitonin: activates osteoblasts and cause more calcium to go into bones
- humoral stimulus (change of calcium in blood)
PARATHYROID GLAND
- releases parathyroid hormone: activates osteoclasts and cause more calcium from bone to go into blood
- humoral stimulus (change of calcium in blood)
ADRENAL GLAND
(1) Adrenal Cortex: outer layer
- releases steroids (adrenal corticoids)
- hormonal stimulus
- ACTH from ant. pituitary –> adrenal cortex and tells it to release adrenal corticoids (stress hormones)
(1) Aldosterone:
- similar to ADH
- causes less urination
(2) Cortisol:
- major stress hormone
- suppresses immune system
- ex: hydrocortisone cream
- also releases androgens
- male sex hormones
- in both males and females, greater degree in males
- not in huge levels
(2) Adrenal Medulla: core, inner layer
- mostly releases epinephrine: fight or flight response (adrenaline) that prepares you for physical activity
- neural stimulus
GONADS
- hormonal stimulus
- Testes
- males
- mostly secrete androgens
- testosterone, & molecules similar to testosterone
- Ovaries
- females
- mostly secrete estrogens and progesterone
- estrogens are made from androgens
- secrete huge quantities of androgens and use aromatase enzyme to convert them to estrogens
PANCREAS
- humoral control
(1) insulin
- secreted by beta cells
- after eating, insulin will uptake glucose from bloodstream so blood sugar will fall
(2) glucagon
- secreted by alpha cells
- blood sugar levels fall –> glucagon will go to liver and tell it to break down glycogen and release glucose into bloodstream/start gluconeogenesis
PINEAL GLAND
- neural stimulus
- releases melatonin in low light –> sleep
- opposite reaction in light
- plays significant role in circadian rhythm
Diabetes
TYPE 1
- juvenile diabetes
- autoimmune disorder
- immune system sees beta cells as foreign and destroys them
- incapable of secreting insulin
- blood sugar remains elevated –> ketoacidosis
- excessive thirst is symptom because brain is activated in order to increase urination to release excess glucose
TYPE 2
- “late onset” but not really
- due to poor diet and lack of exercise
- genetically predisposed
- insulin secretion is not issue; however, insulin is unable to bind to receptor cells and tell body to uptake glucose in bloodstream
- blood sugar levels are elevated
- due to inflammation from obesity
- viscerally obese: excess fat in abdominal area
- resolve by eating healthier diet and exercising
