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PHPY 303 > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

Main functions of gonads:

A

Producing gametes - spermatogenesis/oogenesis

Producing sex hormones - testosterone/estrogen and progesterone

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2
Q

Prostate gland:

A

Secretes milky, slightly acidic fluid that makes up 50-75% of semen.

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3
Q

pH of semen:

A

Despite large acidic component from prostate, semen is overall alkaline to neutralize low vaginal pH.

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4
Q

March of the semen:

A

Spermatozoa are formed in seminiferous tubules. They flow to the rete testes and then to the efferent ductules, epididymis, and vas deferens.

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5
Q

Seminiferous tubule:

A

An epithelium formed by Sertoli cells. Immature spermatogonia live at the periphery, and mature spermatozoa live near the lumen.

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6
Q

Where are Leydig cells?

A

Interstitial space around seminiferous tubules.

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7
Q

Where does maturation of spermatids into spermatozoa occur?

A

Epididymis.

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8
Q

Hypothalamic pituitary axis:

A

Produces neurohormones called hypothalamic releasing hormones. Releasing hormones stimulate or inhibit pit gland hormone release. Also regulates circadian rhythm, sleep, fatigue, body temperature, hunger/thirst.

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9
Q

Pathway of hypothalamic releasing hormones:

A

From hypothalamus to anterior lobe of pit gland (adenohypophysis) through long portal vessels. From ant pit to other endocrine organs.

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10
Q

Post pit gland pathway:

A

ADH and oxytocin from hypothalamus go to post pit gland through median eminence and pituitary stalk. ADH and oxytocin then go to rest of body.

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11
Q

Hypothalamic control of adrenal medullae:

A

Preganglionic (sympathetic) motor fibres tell adrenal glands when to secrete epinephrine and norepinephrine.

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12
Q

GHRH: target cell, corresponding ant pit hormone, effect

A

Somatotrophs in liver. GH.

Stimulates IGF-1 production in somatic tissues, especially liver.

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13
Q

TRH: target cell, corresponding ant pit hormone, effect

A

Thyrotrophs. TSH.

Stimulates thyroid follicular cells to make corticosteroids.

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14
Q

CRH: target cell, corresponding ant pit hormone, effect

A

Corticotrophs. ACTH.

Stimulates fasciculata and reticularis cells in the adrenal cortex to make corticosteroids.

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15
Q

GnRH: target cell, corresponding ant pit hormone, effect – FSH.

A

Gonadotrophs. FSH.
Stimulates ovarian follicular cells to make estrogens and progestins. Stimulates Sertoli cells to initiate spermatogenesis.

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16
Q

GnRH: target cell, corresponding ant pit hormone, effect – LH.

A

Gonadotrophs. LH.

Stimulates Leydig cells to make testosterone.

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17
Q

LH-targeting GnRH is inhibited by:

A

Dopamine.

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18
Q

GnRH: target cell, corresponding ant pit hormone, effect – PRL.

A

Lactotrophs. PRL.

Stimulates mammary glands.

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19
Q

Effect of vasopressin:

A

Increases water permeability of renal collecting duct.

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20
Q

Effect of oxytocin:

A

Regulates uterus and breast.

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21
Q

Male hypothalamic pituitary axis:

A

Controls spermatogenesis in seminiferous tubules and androgen biosynthesis in Leydig cells.

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22
Q

Spermatogenesis and male hyp pit axis:

A

GnRH stimulates synthesis, storage, and secretion of gonadotropins (FSH and LH) by gonadotrophs in ant pit.

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23
Q

Where are GnRH neurons?

A

Dispersed through hypothalamus but localized in arcuate nucleus and preoptic area.

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24
Q

Synthesis and activation of GnRH:

A

Synthesized as inactive prohormone. Activated by cleavage.

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25
Q

Gonadotropin (LH/FSH) interaction with GnRH:

Which pathway?

A

Gonadotropins have cell surface receptors with high affinity for GnRH. Receptors are coupled to G-protein G-alpha-q, which activates PLC.

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26
Q

PLC pathway:

A

PLC -> IP3 -> (Ca2+) and DAG -> PKC -> effect.

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27
Q

Releasing hormones that use PLC pathway:

A

TRH, GnRH

28
Q

Releasing hormones that use AC pathway:

A

CRH, somatostatin - increased.

Somatostatin again, GHRH - decreased.

29
Q

GnRH secretion pattern:

A

Pulsatile! Means that LH and FSH are also pulsatile.

30
Q

Dopamine signalling pathway through median eminence:

A

Decreased AC, increased K+, decreased Ca2+

31
Q

LH feedback loop in hyp pit axis:

A

LH stimulates Leydig cells to synthesize (T).

(T) inhibits GnRH, which inhibits LH release.

32
Q

FSH feedback loop in hyp pit axis:

A

FSH stimulates Sertoli cells to synthesize ABP, aromatase, growth factors, inhibin.
Inhibin inhibits FSH release.

33
Q

Glycoprotein hormone family members:

A

LH, FSH, hCG, TSH.

34
Q

Structure of glycoprotein hormones:

A

Alpha and beta polypeptide chains.
Alpha: all the same.
Beta: confer unique characteristics.

35
Q

LH vs hCG:

A

Beta subunits are almost identical - hCG has 24 extra AAs and extra glycosylation at C terminus.

36
Q

Where is hCG secreted?

A

Mainly placenta, also small amounts in testes and pit gland.

37
Q

Immune reaction to fertilized egg:

A

hCG is responsible. Stops egg from implanting.

38
Q

FSH/LSH, pre/post puberty: who dominates?

A

FSH before puberty.

LH after puberty.

39
Q

Preference of male GnRH:

A

Prefers LH in adult human male.
Mature testes produce inhibin (inhibits FSH).
Pit gets more sensitive to gonadal steroid production (need less FSH).

40
Q

LH in testes:

A

LH stimulates Leydig cells to synthesize and release (T). Primary source of (T). Leydig cells use steroid biosynthesis pathway to synthesized androgens from cholesterol.

41
Q

LH in ovaries:

A

LH stimulates Theca cells to secrete (T). Granulosa cells convert testosterone to estrogen.
LH stimulates luteal function.

42
Q

AC pathway:

A

G-protein -> AC -> cAMP -> PKA -> effect.

43
Q

Signalling pathway of LH:

A

AC.

44
Q

LH and SCP:

A

LH stimulates synthesis of sterol-carrier protein (SCP). SCP-2 helps transport cholesterol from outer mitochondrial membrane to inner mitochondrial membrane. On the inner mitochondrial membrane, cholesterol sidechain is cleaved to begin stereogenesis (pregnenolone).

45
Q

LH and SAP:

A

LH stimulates synthesis of sterol-activating protein (SAP). SAP also activates stereogenesis.

46
Q

Molecule that inhibits testosterone transcription:

A

Actinomycin D.

47
Q

FSH endgame:

A

Stimulate Sertoli cells to synthesize and release ABP, inhibin, and aromatase.

48
Q

ABP: secreted where? function?

A

Secreted into luminal space of seminiferous tubules. Keeps local (T) high.

49
Q

Aromatase: where? function?

A

(T) diffuses into Sertoli cells from Leydig cells. Aromatase converts (T) into estradiol.

50
Q

Growth factors and spermies:

A

Supports sperm cells and spermatogenesis. Increases number of spermatogonia, spermatocytes, and spermatids in testes. Possibly increases sperm motility.

51
Q

Inhibin: family? structure? source?

A

Member of transforming growth factor beta (TGF-beta) gene family.
Glycoprotein heterodimer (alpha and beta) covalently linked.
Primary source: Sertoli cells and granulosa cells.

52
Q

Crosstalk between Sertoli and Leydig cells:

A 
Sertoli converts (T) to estradiol and diffuses into Leydig. Sertoli produces growth factors to increase LH receptors on Leydig cells.
(T) diffuses from Leydig to Sertoli.
53
Q

LH/FSH balance:

A

For every LH/FSH released, another is synthesized and stored.

54
Q

Conditions for optimal spermatogenesis: (5)

A

Leydig cells (1) and LH (2) produced testosterone (3). Sertoli cells (4) and FSH (5) produce inhibin and growth factors and nurse developing sperm.

55
Q

Therapeutic use of hCG:

A

Initiate spermatogenesis in oligospermic men.

56
Q

LH during puberty:

A

Produces androgens to make you a MAN

57
Q

FSH during puberty:

A

Preferential release to control inhibitory effect on pit gland (using inhibin)

58
Q

Where Leydig cells come from:

A

Mesenchymal tissue that surrounds testicular cords.

59
Q

Converting cholesterol to testosterone in Leydig cells: 4 possible pathways. Gimme the best one.

A
  1. Mitochondria. Cytochrome P-450 side chain cleavage (SCC) enzyme slaves long chain off of cholesterol to make pregnenolone. Rate-limiting step. LH increases enzyme affinity for cholesterol and stimulates SCC enzyme synthesis.
    Then it’s the chart you already know. (: (:
60
Q

Tissues that can convert cholesterol to active hormone:

A

Adrenal cortex: cortisol, aldosterone, androgens.

Gonad: testosterone, progesterone/estrogen.

61
Q

Transport of (T):

A

Almost never alone. Only free hormone is active!
45% of plasma (T) is bound to sex hormone-binding globulin (SHBG), aka TeBG.
55% is bound to corticosteroid-binding globulin (CBG).
2% is free.

62
Q

What do ultrasounds look for to predict sex?

A

If DHT is present, it’s a dude!

63
Q

Secondary sex characteristics are dependent on [DHT or (T)?]

A

DHT! Not (T)!

64
Q

(T) and aging: MENopause.

A

(T) declines with age. Decreased bone formation, muscle mass, facial hair, appetite, libido. (T) therapy can treat issues.

65
Q

Metabolism of testosterone:

A

Liver: converts androgens to 17-ketosteroids.
Prostate: converts androgens to DHT.
Degradation products are excreted as water-soluble sulfuric acid or glucuronic acid conjugates, through urine or feces. Very little (T) gets through without metabolism.

66
Q

Testicular descent: when? what happens?

A

Occurs in final month of fetal life.
Testes descend into scrotum to regulate sperm temp.
- Phase 1: testes move into inguinal region.
- Phase 2: abdominal wall herniates to gubernaculum (ligament between testes and labioscrotal fold).
- Phase 3: gubernaculum draws testes into the scrotum.

67
Q

Cryptochidism:

A

Abnormal retention of testes in abdominal cavity. Can damage seminiferous tubules.

PHPY 303 (8 decks)

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