endocrine system Flashcards
overview
- regulates growth, reproduction, metabolism
- glands and tissues secrete hormones which travel in blood to target cells
- bind to receptors + change cell activity
where can receptors be found
- on the cell membrane
2. intracellular (nuclear)
Hormone types: water soluble hormones
peptides, proteins, catecholamine
steps of water soluble hormones
a. hormone binds to cell membrane receptors
b. hormone-receptor complex activates membrane proteins
c. G-proteins then activate 2nd messenger systems
examples using cAMP as 2nd messenger
a. hormone binds to cell-surface receptor and activates G-proteins
b. G-protein activates adenylate cyclase
c. adenylate cyclase converts ATP to cAMP
d. cAMP activates protein kinases (in cytosol)
e. protein kinase acts on other proteins to alter activity
why use 2nd messenger systems
a. hormone cant enter cell (water soluble)
b. rapid acting (enzymes already present)
c. 1 hormone molecule - many enzyme molecules activated
d. limited - messenger broken down or removed
lipid soluble hormones
- steroids and thyroid hormones
- trigger protein synthesis which takes time, slow
lipid soluble hormone steps
- enter target cell and bind to intracellular receptors in cytosol nucleus
- hormone-receptor complex binds to a specific region on DNA
- mRNA attaches to ribosomes to produce proteins (translation)
what are the three types of stimuli that triggers endocrine glands to manufacture and release hormones
- humoral
- neural
- hormonal
stress
- any extreme external or internal stimulus e.g. surgery, infections, strong emotions
- triggers a set of body changes called general adaptation syndrome
- all co-ordinated directly or indirectly by the hypothalamus
what are the phases of stress
1: alarm reaction
- immediate = NS
- CNS (detects change) - hypothalamus (raises alertness) - SNS, then goes to organs and adrenal medulla - epinephrine
2: resistance reaction
- long term - endocrine
- permits recovery from 1. or
- hypothalamic hormones initiates phase 2
3: exhaustion
- results from:
a. depletion of body resources
b. loss of K
c. damage to organs
how does alarm reaction effect NS and hormones
a. raises blood glucose
b. raise HR, forces contraction
c. raise respiration rate
d. lowers blood flow to skin
e. lowers digestion, urine production
the release of hormones in the resistance reaction causes
a. raise blood glucose: liver stimulated to produce new glucose from fats. used by NS. metabolism of non-nervous tissue directed to fats for energy. if stress continues, inhibits growth hormone to release proteins
b. inhibition of: immune system, bone formation, formation of CT
c. release of aldosterone + antidiuretic hormone which reduces salt + water loss at kidney to maintain blood vol.
what are the functions of testosterone
- development of organs of male reprod. tract
- stimulates bone growth at epiphyseal plate
- promotes protein anabolism
- directly stimulates spermatogenesis
female reproductive hormones
- FSH
- LH
- stimulates estrogen production from theca granulosa - Estrogen
- requires ovulation - Progesterone
- from corpus luteum
- prepares uterus for pregnancy
ovarian/uterine cycle (28 days)
- days 1-14
a). ovary: follicular phase
- uterus: same time as a)
-menstrual phase, stratum functionalis sheds
- proliferative phase (6-14)
repair + proliferation of stratum functionalis (mitosis in stratum basalis) - day 14: ovulation
- due to LH surge
-triggers:
completion of mitosis
rupture of vesicular follicle to release 2 oocyte - days 15-28
a. ovary: luteal phase
b. uterus: secretory phase - if fertilization occurs
a. placenta secretes human chorionic gonadotropin
b. corpus luteum
c. FSH, LH inhibited by high P - if NO fertilization
a. corpus luteum - corpus albicans `
contraceptives
- oral
- high E+P
- no follicle maturation, no ovulation - implants e.g. progestin
- morning after pill
- high E and progestin or progestin only
- prevents implantation, ovulation or fertilezation
placenta
-formed from chorion and endometrium
- blood vessels of mother and fetus in close proximity
functions:
- exchange site for gases nutrients hormones antibodies
2. secretes hormones
- E+P
- hCG which is detected by pregnancy tests and stim. testosterone
