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Physiology > Endocrine System > Flashcards

Endocrine System Flashcards

0
Q

What does the endocrine system do?

A
  • regulates growth, reproduction and metabolism which are long term events
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1
Q

What is the second major control system?

A

Endocrine System

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2
Q

In the endocrine system, what does the glands and tissues do?

A
  • they secrete hormones which travel in blood to target cells which contain specific receptors for that hormone
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3
Q

When the hormones bind to their designated receptors, what happens?

A

Change in cell activity

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4
Q

In the endocrine system, where are the receptors found?

A
  • cell membrane

- intracellular (nucleus)

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5
Q

What are the types of hormones present in the endocrine system?

A

Water soluble hormones and lipid soluble hormones

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6
Q

What water soluble hormones are present in the first messenger system?

A
  • peptides, proteins, catecholamines
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7
Q

What happens in the first messenger system?

A
  • hormones bind to the cell membrane receptors
  • the hormone-receptor complex then activates membrane proteins such as G-proteins
  • the G-proteins then activate the second messenger system (cAMP, Ca2+)
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8
Q

what does the cAMP stand for?

A

cyclic adenosine monophosphate

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9
Q

Explain in detail how the second messenger system is activated and what happens afterwards?

A
  • hormones bind to cell receptor membrane which activates the G-Protein
  • the G-protein then activates the membrane protein adenylatecyclase
  • which turns ATP to cAMP (therefore cAMP concentration increases)
  • the cAMP activates protein kinases in cytosol
  • protein kinases activates other proteins via phosphorylation to alter their activity
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10
Q

What activates the cAMP on liver cells and what happens after they are activated?

A
  • epinephrine

- this causes the breakdown of glycogen to glucose which is then released to the blood

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11
Q

What use the second system?

A
  • rapid acting (enzymes are are already present they just needed to be activated)
  • hormones can’t enter cell since they are water soluble
  • for 1 hormone molecule, many enzyme molecules are activated which multiplies the signal
  • limited - messenger is broken down or removed (eg. cAMP is broken down by phosphodiesterase)
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12
Q

What do lipid soluble hormones do?

A
  • they trigger protein synthesis, it takes time but it’s a long lasting response
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13
Q

Give examples of lipid soluble hormones.

A

Steroid (cortisol) & thyroid hormones

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14
Q

Explain the steps to lipid soluble hormones

A
  • hormone enters target cell and bind to the intracellular (nuclear) receptors in the cytoplasm or nucleus of the cell.
  • the hormone-receptor complex binds to a specific region of DNA
  • this activates the genes
  • which starts transcription
  • mRNA is produce which attaches to a ribosome to make protein (translation)
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15
Q

Stimuli acting on an endocrine gland can be….

A
  • humoral stimulus
  • neural stimulus
  • hormonal stimulus
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16
Q

What is a humoural stimulus? Give examples

A

when the stimulus is the ions/concentration of bodily fluids like blood.
- when the blood glucose increases after eating carbs, the pancreatic B-cells of Islets of Langerhans detect and release insulin which decreases blood glucose

  • when the blood Ca2+ is decreased, the parathyroid gland detects this change and releases parathyroid hormone (PTH) which increases bone resorption and deceases osteoblast activity (osteoclasts still working to breakdown bone) = as a result, blood Ca2+ increases
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17
Q

What is a neural stimuli? Give an example

A

when the stimuli is coming from the nerves or the nervous system
- when the heart rate is at rest and there’s a surprising event that happens –> Sympathetic Nervous System functions - preganglionic neurone —> nt = AcH –> adrenal medulla –> nt = epinephrine & NE -> increased heart rate + forced contraction

  • this is an example of the nervous system departing from homeostasis in a controlled manner…
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18
Q

What is a hormonal stimuli? Give examples. Are they negative feedbacks or positive feedbacks

A

When the stimuli is a hormone
1) in a low metabolism, the hypothalamus secretes thyrotropin-releasing hormone (TRH) –> anterior pituitary gland secrete thyroid stimulating hormone (TSH) –> thyroid gland secretes thyroxin (T4) –> T4 to T3 (in target tissues or liver) –> increase in metabolism

  • negative feedback

2) in uterine contractions, hypothalamus –> posterior pituitary gland secretes oxytocin –> increases urine contraction
- positive feedback

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19
Q

What is stress? Give examples

A

any extreme internal or external stimulus such as surgery, infections, strong emotions, exams

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20
Q

what does stress do to the body?

A

triggers set of body changes called General Adaptation Syndrome

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21
Q

stress is co-ordinated directly or indirectly by what?

A

hypothalamus

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22
Q

What are the three phases/levels of stress?

A

Phase 1 = alarm reaction
Phase 2 = long term reaction
Phase 3 = exhaustion

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23
Q

What system is mostly working during the phase 1 of stress?

A

Nervous system = Sympathetic Nervous System

24
Q

Explain the mechanism of stress in phase 1

A

CNS receives sensory input and detects change -> hypothalamus secretes RAS which increases alertness in the body –> Sympathetic Nervous System –> organs associated with it work & adrenal medulla secretes (NE + epinephrine) which prolongs flight or fight response

25
Q

What are the effects of Phase 1 of stress

-

A
  • increase in blood glucose because SNS inhibits the production of insulin to breakdown the glucose & the NE, E converts glycogen to glucose in the liver
  • the heart rate increases + forced contraction
  • respiration rate increases
  • decrease blood flow skin and abdominal viscera because they are more available to skel. muscle, cardiac muscle and brain
  • digestion decreases and so does urine production
26
Q

What system is mostly working now in phase 2 of stress?

A
  • endocrine system
27
Q

What happens in phase 2 of stress

A
  • the endocrine system permits recovery from the effects of phase 1 (eg. tissue repair)
  • responds to long term stress
28
Q

Explain the mechanism of the endocrine system during phase 2 of stress

A

hypothalamus
/ \
growth hormone corticotropin releasing hormone (GHRH)releasing hormone (CRH)
\ /
anterior pituitary gland
/ \
growth hormone (GH) adrenocorticotropic
hormone (ACTH)
l
adrenal medulla
l
cortisol (glucocorticoid)

29
Q

What does the GH do in phase 2 of stress?

A

stimulations growth (protein reproduction) and cell reproduction

30
Q

What does the cortisol do in phase 2 of stress?

A
  • it’s released in 30 seconds of stress but response is slow
  • steroid hormones act on nuclear receptors
  • inhibits insulin production
31
Q

Overall what are the effects of the hormones released during phase 2 of stress

A

1) blood glucose increases = due to little insulin (inhibition)
- skel. muscle + adipose tissue aren’t taking glucose very well
- spared glucose is used by NS
- metabolism of non NS directed to use fat as source of energy
- if stress continues, cortisol level increases which then inhibits production of GH, as a result protein is used for energy as well
- OVERALL: the FA blood and AA increase and are used for energy
2) inhibition of immune system. bone & CT formation (delays healing)
3) release of hormones aldosterone and ADH (Antidiuretic hormone) = reduces salt and water loss at kidney to maintain blood volume

32
Q

What are the long term effects of stress during phase 2?d

A
  • weight loss
  • increased risk of type 2 diabetes due to increase of glucose
  • increased blood pressure
  • increased heart rate
  • immune system suppression
  • decreased bone density
33
Q

During phase 3 of stress what happens?

A

exhaustion due to:

  • depletion of body resources (lipid reserves)
  • loss of K+ (aldosterone effect)
  • damage to organs such as heart, liver, kidney
34
Q

Explain hormonal regulation of the male reproductive function. (after puberty)

A
  • at the hypothalamus, Gonadotropin Releasing Hormone is released (GnRH)
  • this stimulates the anterior pituitary gland, which releases the Lutenizing Hormone (LH) & Follicle Stimulating Hormone (FSH)
  • the LH stimulates the testes to secrete testosterone which directly stimulates spermatogenesis in the seminiferous tubules
  • the FSH INDIRECTLY stimulates spermatogenesis
35
Q

What is the role of testosterone?

A
  • directly stimulates spermatogenesis
  • development of organs or reproduction tract & 2 degree sex characteristics
  • stimulates bone growth at epiphyseal plate (converted to E to stop growth = closing of the plate)
  • promotes protein anabolism
36
Q

Why is the hormonal regulation of male reproductive function considered a negative feedback.

A

Because the increase of sperm count (spermatogenesis) inhibits the secretion of hypothalamic GnRH and FSH

37
Q

Explain the steps of the hormonal regulation of the female reproductive function after puberty.

A
  • at the hypothalamus, GnRH or Gonadotropin Releasing Hormone stimulates the anterior pituitary gland to release LH and FSH.
  • Then the LH stimulates ovulation in the ovaries and signals the production of estrogen
  • FSH stimulates the production of follicles (primary and secondary) which then simulates production of estrogen at the signal of LH
38
Q

What is the role of the FSH in the hormonal regulation of the female reproduction function?

A
  • stimulates primary to become a secondary follicle
39
Q

What happens when level of progesterone rises?

A
  • it inhibits the production of FSH and LH
40
Q

What roles does the LH play in the hormonal regulation of the female reproduction function?

A
  • stimulates estrogen production from theca + granulosa cells of follicle
  • in an LH surge, it causes ovulation and formation of corpus luteum from the remnants of the follicle
  • during the follicular phase, the estrogen from the secondary follicle stimulates the release of LH via the GnRH which then stimulates the follicle to create more estrogen (an example of a positive feedback = as a result, LH surge occurs
41
Q

What is the luteal phase?

A

When the rising progesterone levels inhibit the production of LH

42
Q

What is the role of estrogen in the hormonal regulation of the female reproduction function?

A
  • required for ovulation
  • develops secondary sex characteristics
  • requires for bone growth and closure of the epiphysis
  • stimulates growth and maintains endometrium
43
Q

What is the role of progesterone in the hormonal regulation of the female reproduction function?

A
  • prepares uterus for pregnancy
44
Q

Where does progesterone come from?

A

corpus luteum

45
Q

What happens to the ovarian/uterus cycle in day 1-14

A

1) Ovary - goes through follicular phase (preovulatory phase)
- early on, there’s low levels of Progesterone therefore secretion of LH and FSH is high.
- some primary follicle becomes secondary due to lFSH
- the follicles secrete estrogen, therefore estrogen levels in blood increases
- one (usually) secondary follicle becomes a Graafian follicle
2) Uterus
- Menstrual phase (day 1-5)
= the stratum functionalis shed (outer layer of endometrium) & the denuded areas bleed
= therefore, menstrual flow happens = blood, cell + secretions
- Proliferative phase (day 6-14)
= Estrogen repairs and proliferates the stratum functionalis due to the mitosis of stratum basalis

46
Q

What happens in the ovarian/uterine cycle in day 14?

A

Ovulation caused by the LH surge.

  • the LH triggers:
    • completion of meiosis I –> secondary oocyte
    • breakdown of the Graafian follicle to release secondary oocyte
47
Q

What happens during day 15-28 in the ovarian/uterine cycle?

A

1) The ovary goes through:
- Luteal Phase = high levels of P inhibits the GnRH therefore no secretion of LH and FSH = as a result, no follicles are developed

2) The uterus goes through:
- Secretion Phase = the progesterone from corpus luteum prepares the endometrium for implantation = becomes vascular, thick and stores glycogen
= inhibits uterine contraction

48
Q

What happens when fertilization occurs?

A
  • the placenta secretes human chorionoic gonadotropin (hCHG) which maintains corpus luteum
  • for about 6 weeks, the corpus luteum secretes estrogen and progesterone and then the placenta takes over
  • FSH and LH is inhibited the high levels of P so no follicles develop
49
Q

The human chorionic gonadotropin has a similar structure to?

A

Lutenising hormone

50
Q

If no fertilization what happens?

A
  • the corpus luteum becomes corpus albican = no hCG & low LH
  • decrease in progesterone and estrogen = therefore, no inhibition of LH and FSH (so they increase), no longer maintain endometrium = menstruation
51
Q

What are some contraceptives?

A
  • oral contraceptives
  • implants
  • morning after pill
52
Q

What do oral contraceptives do?

A

high secretion of E and P which inhibits the GnRH causing low levels of LH and FSH (mimics fertilization) = no follicle maturation and ovulation

53
Q

Give an example of implants?

A
  • progestin which has a similar mechanism to oral contraceptives
54
Q

What do morning after pills do?

A

they increase Estrogen production and progestin OR progestin alone. It prevents implantation, ovulation and fertilization

55
Q

Placenta is formed from?

A
  • chorion of the fetus and endometrium of the mother
56
Q

Is there blood mixing between the fetus and the mother in the placenta?

A

no

57
Q

What is the role of the placenta?

A

1) exchange site
= gases, nutrients, wastes, antibodies (passive immunity), hormones, viruses, drugs (eg. alcohol, morphine, nicotine)

2) secretes hormones = progesterone and estrogen
= hCG: maintains the corpus luteum for about 6 weeks post-fertilization
- detected by pregnancy test
- stimulates testosterone secretion by fetal testes

Physiology (11 decks)

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