Endocrine System

Question 1

What does the endocrine system do (simple)?

Answer 1

regulates growth reproduction and metabolism. works in conjunction with the NS. very spread out. glands and tissues secrete hormones which travel in blood to target cells where they will bind to receptors and change cell activity.

Question 2

What are target cells?

Answer 2

cells of an effector tissue/organ that have specific receptors for a hormone.

Question 3

Where are receptor proteins found?

Answer 3

on the cell membrane, or intracellular (nuclear) - so in the cell.

Question 4

What are some examples of water soluble molecules?

Answer 4

peptides, proteins, catecholamines (norepinephrine and epinephrine).

Question 5

What are the actions of water soluble molecules?

Answer 5

they act as 1st messengers in a signalling cascade. they are not able to cross the hydrophobic areas of the phospholipid bilayer so they must bind to receptors on the cell membrane. a. hormone binds to cell membrane receptors b. hormone-receptor complex activates membrane proteins c. membrane proteins then activate second messenger systems.

Question 6

Explain the signalling cascade of cAMP.

Answer 6

1. hormone binds to cell membrane receptor, hormone-receptor complex activates G-proteins (membrane prots) 2. G-proteins activate adenylate cyclases (memb prot). 3. adenylate cyclase converts ATP into cAMP which is a secondary messenger this increases the cAMP concentration in the cytosol. 4. cAMP activates protein kinases 5. protein kinases phosphorylate other proteins to alter their activity and therefore change the cells activity.

Question 7

Explain the signalling cascade using epinephrine acting on liver cells.

Answer 7

1. hormone bonds to membrane receptor and activates g-proteins 2. g-protein activates adenylate cyclase 3. adenylate cyclase converts atp to cAMP 4. cAMP activates protein kinase A 5. protein kinase A activates metabolic proteins that cause breakdown of glycogen into glucose 6. glucose is released into blood.

Question 8

Why use 2nd messenger systems?

Answer 8

1. hormone cant enter cell bc water soluble 2. rapid acting - enzymes already present just need to be activated 3. 1 hormone molecule activates many enzyme molecules which multiplies the signal. 4. limited - messenger broken down or removed stops the cascade.

Question 9

What are some examples of lipid soluble hormones?

Answer 9

steroids like cortisol and thyroid hormones.

Question 10

What do lipid soluble hormones trigger?

Answer 10

protein synthesis, which is a slow but long lasting response mainly for growth and reproductive systems. end result is creating a protein that elicits a response.

Question 11

What is the mechanism of action of protein synthesis?

Answer 11

1. hormone enters target cell and binds to an intracellular receptor in the cytosol or nucleus. 2. hormone-receptor complex binds to specific region of DNA and activates genes 3. starts gene transcription (copying) and creates messenger RNA. 4. mRNA attaches to ribosomes to produce proteins (translation)

Question 12

What types of stimuli act on endocrine glands (list)?

Answer 12

1. humoral stimuli 2. neural stimuli 3. hormonal stimuli.

Question 13

What is a humoral stimulus>?

Answer 13

a stimulus for hormone release when there is a change in the concentration of a particular ion or nutrient in the blood. (so when the conc of a substance in bl changes, triggers hormone release)

Question 14

Explain the blood glucose example of a humoral stimulus causing hormone secretion.

Answer 14

increase in blood glucose –> detected by pancreatic B-cells (islets of langerhans) which release insulin –> decrease in blood glucose. this is a negative fb mech. stimulus= change in glucose

Question 15

Explain the blood Ca example of a humoral stimulus causing hormone secretion.

Answer 15

decrease in blood Ca –> parathyroid gland detects decrease and releases parathyroid hormone (PTH) –> increase in bone resorption/breakdown (bc bone has lots of ca in it) by decreasing osteoblast (building) activity and increasing osteoclast (breakdown) activity –> increase in blood Ca.

Question 16

What is a neural stimulus?

Answer 16

AP or a neural signal is sent from the NS which triggers an endocrine gland to secrete a hormone.

Question 17

Explain the heart rate example of a neural stimulus releasing a hormone.

Answer 17

resting HR –> surprise –> triggers SNS which sends an AP down a preganglionic neuron (bc its ANS) –> at synapse release ACh onto adrenal medulla –> release epi and NE –> increases HR and force of contraction. Stimulus= preganglionic neuron releasing nt onto endocrine gland ie adrenal medulla. moving out of homeostasis in a controlled manner until stimulus stops.

Question 18

Explain the uterine contractions example of a neural stimulus releasing a hormone.

Answer 18

uterine contractions occur –> signals hypothalamus –> sends signal to posterior pituitary –> releases oxytocin –> increases uterine contractions. stimulus= hypothalamus sending signal to posterior pituitary (endo gland). pos fb mech.

Question 19

What is a hormonal stimulus?

Answer 19

hormone release is stimulated by another hormone.

Question 20

Explain the metabolism example of a hormonal stimulus releasing a hormone.

Answer 20

low metabolism –> hypothalamus releases thyrotropin-releasing hormone (TRH) –> acts on anterior pituitary to release thyroid stimulating hormone (TSH) –> goes to thyroid gland causing it to release thyroxin (T4) –> T4 to T3 in target tissue or liver –> increases metabolism. thyroxin also works to inhibit TRH and TSH release to stop the hormone cascade (neg fb mech). whole thing is a neg fb mech.

Question 21

What is stress?

Answer 21

any extreme internal or external stimulus ie surgery, infections, strong emotions, exams.

Question 22

What is the general adaptation system?

Answer 22

a set of body changes all coordinated directly or indirectly by the hypothalamus. has 3 phases: Alarm reaction, resistance reaction, exhaustion.

Question 23

What happens during Phase 1: alarm reaction (what is the pathway)?

Answer 23

the fight or flight response. immediate, activates NS. CNS gets sensory input (seeing a bear) and detects a change –> sends signal to hypothalamus which has the RAS so increases alertness –> signal sent to SNS –> acts on organs –> also acts on adrenal medulla –> releases E and NE –> prolongs fight or flight response.

Question 24

What are the effects of the SNS and endo syst during phase 1 (so what do they do)?

Answer 24

1. increase bl glucose - SNS inhibits insulin release, E and NE trigger conversion of glycogen to glucose in liver 2. increase HR and force of contraction 3. increase respiration rate 4. decrease bl flow to skin and abdominal viscera (want bl to be more available to skel and cardiac mm and brain bc it brings o2 and glucose) 5. decrease digestion and urine production

Question 25

What happens during Phase 2: resistance reaction (what is the pathway)?

Answer 25

long term, endocrine. permits recovery from the effects of phase 1. so does tissue repair etc. or is a response to longer term stress. hypothalamic hormones initiate phase 2. hypothalamus --> releases growth hormone releasing hormone --> acts on anterior pituitary --> causes release of growth hormone. at same time; hypothalamus --> releases corticotropin releasing hormone --> acts on ant pituitary --> releases ACTH --> acts on adrenal cortex --> releases cortisol

Question 26

What does growth hormone (GH) do?

Answer 26

stimulates growth (protein production) and cell reproduction.

Question 27

What does cortisol do?

Answer 27

released within 30 seconds of the stress but the response not for hours. steroid hormone - acts at nuclear receptors. inhibits insulin release.

Question 28

What does the release of hormones cause in phase 2?

Answer 28

1. increase in blood glucose a) liver stimulated to produce new glucose from fats and later proteins. b) little insulin bc of inhibition, glucose not taken up well, especially by skel mm and adipose tissue therefore glucose is spared for use by NS, metabolism of non nervous tissue directed to use fats for NRG (controlled by GH and cortisol), and if stress continues cortisol inhibits GH release and proteins are then also used. overall; increase in bl FA and aa --> NRG. 2. inhibition of immune syst, bone formation, formation of CT. 3. release of aldosterone and antidiuretic hormone; reduces salt and water loss at kidney to maintain bl volume

Question 29

What are the long term effects of phase 2?

Answer 29

decreased weight, increased bp, increased HR, immune suppression (cortisol), decreased bone density, increased risk of type 2 diabetes (bc of increased bl glucose)

Question 30

What does phase 3: exhaustion result from?

Answer 30

1. depletion of body resources (lipid reserves) 2. loss of K (aldosterone effect - hormone increases secretion of K) 3. damage to organs ie heart liver kidneys.

Question 31

What is the pathway of the testicular reproductive hormones (after puberty)?

Answer 31

Hypothalamus --> releases gonadotropin releasing hormone GnRH --> acts on anterior pituitary --> releases both LH and FSH --> LH stimulates testosterone in leydig cells in testes --> T stimulates spermatogenesis in the seminiferous tubules of the testes --> at same time FSH directly stimulates spermatogenesis in seminiferous tubules. neg fb mech where testost. acts to inhibit LH, FSH, and GnRH. so T is inhibiting to release of more.

Question 32

What are the functions of testosterone?

Answer 32

1. development of organs for reproductive tract and secondary sex characteristics 2. stimulate bone growth at epiphyseal plate (converted to E to stop growth and close plate) 3. promotes protein anabolism (forming proteins) 4. directly stimulates spermatogenesis

Question 33

What is the pathway of the ovarian reproductive hormones (after puberty)?

Answer 33

hypothalamus --> releases GnRH --> acts on anterior pituitary --> releases both LH and FSH --> LH spikes and and increase in E, therefore causing ovulation in ovaries --> at same time FSH causes primary and secondary follicles to develop --> causes increase in E

Question 34

What are the fxns of follicle stimulating hormone?

Answer 34

1. stimulates primary to become secondary follicles 2. inhibited by progesterone (so FSH high means P low vice versa).

Question 35

What are the fxns of luteinizing hormone?

Answer 35

1. stimulates E production in granulosa and theca cells of follicles 2. in follicular phase - estrogen from secondary follicle rises for a few days causing the release of LH via GnRH, which stimulates the follicle to increase the release of E, leading to a surge in LH (pos fb mech). 3. surge in LH causes ovulation and then formation of corpus luteum form remnants of follicle 4. in luteal phase - progesterone inhibits LH release.

Question 36

What are the fxns of estrogen?

Answer 36

1. required for ovulation 2. development of secondary sex characteristics 3. stimulates growth and maintains the endometrium 4. stimulates bone growth during puberty, and later in life closure of epiphyses

Question 37

What is the fxn of progesterone?

Answer 37

forms corpus luteum which prepares uterus for pregnancy.

Question 38

When and where does the follicular (preovulatory) phase happen?

Answer 38

days 1-14 in the ovaries, so before ovulation.

Question 39

What happens during the follicular phase?

Answer 39

Early on: progesterone is low so LH and FSH are secreted - some 1˚ follicles become 2˚ follicles due to FSH. follicles secrete E, therefore bl E rises. later on: one 2˚ follicle becomes the vesicular follicle

Question 40

When and where does the Menstrual phase happen?

Answer 40

days 1-5 in the uterus, so during follicular phase in ovaries.

Question 41

What happens in the menstrual phase?

Answer 41

stratum functionalis (outer layer of endometrium) sheds and the denuded area bleeds. therefore menstrual flow is blood, cells, and secretions

Question 42

When and where is the proliferative phase?

Answer 42

days 6-14 in the uterus, so during the follicular phase in ovaries.

Question 43

What happens during the proliferative phase?

Answer 43

E leads to repair and proliferation of the stratum functionalis due to mitosis in the stratum basalis.

Question 44

What happens during ovulation?

Answer 44

day 14 of the ovarian/uterine cycle. happens due to surge in LH. LH triggers; a. completion of meiosis 1 leading to the devel of a 2˚ oocyte b. rupture of vesicular follicle with release of 2˚ oocyte

Question 45

When and where does the luteal phase happen?

Answer 45

days 15-28 in the ovary. after ovulation.

Question 46

What happens during the luteal phase?

Answer 46

have high P from corpus luteum which inhibits GnRH and therefore LH and FSH, meaning no follicles develop

Question 47

When and where is the secretory phase?

Answer 47

days 15-28 in the uterus. happens at same time as luteal phase in ovaries.

Question 48

What happens during the secretory phase?

Answer 48

P from corpus luteum; prepares endometrium for implantation - becomes vascular ,thick, and stores glycogen. also inhibits uterine contractions.

Question 49

What happens if fertilization occurs?

Answer 49

1. placenta secretes human chorionic gonadotropin hCG which maintains the corpus luteum. 2. corpus luteum secretes P and E for ˜6 wks, then the placenta takes over secretion. 3. FSH and LH are inhibited by high P so no follicles develop.

Question 50

What happens if no fertilization occurs?

Answer 50

1. corpus luteum becomes the corpus albicans so theres no hCG and low LH 2. P and E decreases, therefore no longer inhibit LH and FSH so they increase, and no longer maintain endometrium get menstruation.

Question 51

What do oral contraceptives do?

Answer 51

have high P and E which inhibit GnRH secretion, and therefore LH and FSH secretion (mimics luteal phase), therefore no follicle maturation and no ovulation.

Question 52

What do implants do?

Answer 52

progestin, similar mechanism to oral contraceptives so high E and P.

Question 53

What does the morning after pill do?

Answer 53

high E and progestin or progestin only (plan B). prevents implantation, ovulation or fertilization.

Question 54

What is the placenta formed from?

Answer 54

chorion of fetus, and endometrium of mother. the bvs of the mother and fetus are on close proximity.

Question 55

What are the two fxns of the placenta?

Answer 55

1. exchange site 2. secretes hormones

Question 56

What does the placenta exchange?

Answer 56

gases, nutrients/wastes, hormones, antibodies, drugs, viruses.

Question 57

What hormones does the placenta secrete?

Answer 57

E and P (lvls increase as trimesters pass), hCG which maintains the corpus luteum for ˜6 wks post-fertilization, detected by pregnancy tests, stimulates test secretion by fetal testes.