Topic 7: Endocrine System Flashcards by Denver Jackson

What are “1st messengers” in a signaling cascade?

The first step
Includes peptides, proteins, catecholamines

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What type of hormones are steroids?

Lipid soluble hormones

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What is the mechanism of action for protein synthesis?

Enter target cell and bind to intracellular receptors in cytosol or nucleus

Hormone-receptor complex binds to specific region in DNA ~> starts gene transcription, producing mRNA

mRNA attaches to ribosomes to produce proteins (translation)

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What acts as a Humoral stimulus for hormone release?

Changes in the concentration of a particular ion or nutrient in the blood

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When the blood glucose increases after eating carbs, how does the endocrine system respond to this humoral stimulus?

Pancreatic B-cells (of Islets of Langerhans) detect glucose and release insulin to decrease the blood glucose

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How can a neural stimulus cause the heart rate to rise?

(This means moving out of homeostasis in a controlled manner)

Resting
SNS - preganglionic directly to
Adrenal medulla
(sends epinephrine or NE)
Increases HR and force of contraction

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How does the endocrine system act to correct the hormonal stimulus of low metabolism?

-Low metabolism
-Hypothalamus: thyrotropin-releasing hormone (TRH)
-Ant. Pituitary: thyroid-stimulating hormone (TSH)
-Thyroid gland: thyroxin (T4)
-T4 to T3 (in target tissue or liver)
Increased metabolism

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What coordinates, either directly or indirectly, the physiological response to stress?

Hypothalamus

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What is the immediate process of the alarm reaction (phase 1)?

CNS (sensory input/change)
Hypothalamus (RAS increases alertness)
SNS
(Organs) & Adrenal medulla:
E + NE (prolongs fight/flight response)

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What are the effects of the SNS and endocrine system during the alarm phase of stress?

+ blood glucose
+ HR
+ respiration rate
— blood flow to skin, abdominal viscera
— digestion, urine production

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What are the long term effects of the resistance reaction?

— weight
+ bp
+ HR
+ immune suppression (cortisol)
— bone density
+ risk of type 2 diabetes

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What causes the exhaustion phase?

Depletion of body resources

Loss of K+ (aldosterone effect)

Damage to organs (heart, liver, kidneys)

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What is the role of each in the male reproductive systems:

Hypothalamus:

Anterior Pituitary:

Testes:

Hypothalamus: gonadotropin releasing hormone (GnRH)

Ant. Pit.: LH & FSH

Testes:
LH~>testosterone (leydig cells)
FSH~>spermatogenesis (seminiferous tubules)

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What are 4 functions of testosterone?

-Development of organs of reproductive tract and secondary sex characteristics

-Stimulated bone growth at epiphyseal plate

-Promotes protein anabolism

-Directly stimulates spermatogenesis

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What is the female hormone function of FSH?

Stimulates primary to become secondary follicle

Inhibited by progesterone (therefore FSH increases when progesterone decreases & vice versa)

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What is the female hormone function of LH?

Stimulates estrogen production from theca and granulosa cells of follicle

Surge causes ovulation and the formation of corpus luteum

In follicular phase: estrogen from secondary follicle rises

Luteal phase: progesterone inhibits LH release

What is the overall female hormone function of progesterone?

From corpus luteum

Prepares for uterus for pregnancy

What are the 2 main functions of the placenta?

Serves as an EXCHANGE SITEfor gasses, nutrients/waste, hormones, antibodies, drugs, viruses

SECRETES HORMONES, namely estrogen+progesterone and hCG (maintains corpus luteum for ~6 weeks post-fertilization, detected by pregnancy tests)

What is the endocrine system largely responsible for?

Regulates growth, reproduction, and metabolism (lang-term events)

Cells of an effector tissue/organ that have specific receptors for that hormone

Target cells

Where can receptor proteins be found?

On the cell membrane

Intracellular (nuclear)

These are not able to cross the hydrophobic areas of the phospholipid bilayer, so they must bind to receptors on the cell membrane

Water soluble hormones

What is the mechanism of action of water soluble hormones?

Hormone binds to cell membrane receptors
Hormone-receptor complex activates membrane proteins
Membrane proteins (like G-proteins) then activate 2nd messenger systems (eg. cAMP, Ca++)

Explain the example of using cAMP (cyclic adenosine monophosphate) as a 2nd messenger

Hormone binds to cell-surface receptor and activates G-protein
G-protein activates adenylate cyclase (membrane protein)
Adenylate cyclase converts ATP to cAMP, increasing cAMP concentration in the cytosol
cAMP activates protein kinases
Protein kinase acts on other proteins (phosphorylates) to alter their activity, therefore changing cell activity

Why do water soluble hormones use 2nd messenger systems?

a) Hormones can’t enter cell b) Rapid acting (enzymes just need to be activated) c) 1 hormone molecule activates many enzyme molecules, which multiplies the signal d) Limited: messenger broken down or removed

Explain how the humoral stimulus of low blood Ca++ is addressed by hormones: _______ gland detects low Ca++ and releases ______ hormone. Blood Ca++ is raised because of bone breakdown caused by decreased _______ activity and increased _______ activity.

Parathyroid, parathyroid, osteoblast, osteoclast

What is the pathway of hypothalamic hormones in the resistance reaction?

1. Hypothalamus sends [GHRH] and {corticotropin releasing hormone (CRH)} to the ant. pituitary 2. Ant. pituitary releases [GH] and {adrenocorticotropic hormone (ACTH) which goes to adrenal cortex} 3. Adrenal cortex releases {cortisol}

What are the phases of the General Adaptation Syndrome?

Phase 1: Alarm reaction Phase 2: Resistance reaction Phase 3: Exhaustion

What are the functions of the hormone estrogen?

- required for ovulation - development of secondary sex characteristics - stimulates growth and maintenance of the endometrium - stimulates bone growth during and after puberty

Briefly describe how each of these contraceptive methods work Oral contraceptives Implants Morning after pill

Oral contraceptives: high estrogen & progesterone inhibits GnRH secretion, therefore low FSH and LH (mimics luteal phase) ~> no follicle maturation, *no ovulation* Implants: eg. progestin ~> similar to oral contraceptives Morning after pill: high estrogen and progestin or progestin only, prevents implantation, ovulation, or fertilization

What occurs in the uterus during days 1-14 of the uterine cycle?

*Menstrual phase* (days 1-5): stratum functionalis shed, denuded areas bleed ~> menstrual flow *Proliferative phase* (days 6-14): Estrogen ~> repair & proliferation of stratum functionalis

What occurs in the ovary during days 1-14 of the ovarian cycle?

*Follicular (preovulatory) phase*: - early on: low progesterone ~> LH & FSH secreted, some 1st degree follicles then 2nd degree follicles - follicles secrete estrogen ~> blood estrogen rises - later on: usually 1 2nd degree follicle becomes vesicular follicle

What occurs on the 14th day of the ovarian/uterine cycle?

Ovulation • due to LH surge • LH triggers completion of meiosis and rupture of vesicular follicle with release of 2nd degree oocyte

What occurs during the Luteal phase of the ovarian cycle? (days 15-28)

High progesterone from corpus luteum inhibits GnRH (meaning LH & FSH) ~> no follicles develope

What occurs in the uterus during days 15-28 of the uterine cycle?

Secretory phase Progesterone from corpus luteum: - prepares endometrium for implantation (becomes vascular, thick, and stores glycogen) - inhibits uterine contractions

What happens to the hormones if fertilization occurs?

• Placenta secretes human chorionic gonadotropin (hCG) ~> maintains corpus luteum (similar to LH) • Corpus luteum produces P&E for ~6 weeks, then placenta takes over • FSH, LH inhibited by high progesterone (no new follicles)

What happens to the hormones if fertilization does NOT occur?

• Corpus luteum becomes corpus albicans (no hCG, low LH) • Low progesterone and estrogen: no longer maintains endometrium = menstruation