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CPPS 303 > Lectures 1 & 2 Hormones, Signal Trasduction & Sex Differention Jan 08 & 10, 2025 > Flashcards

Lectures 1 & 2 Hormones, Signal Trasduction & Sex Differention Jan 08 & 10, 2025 Flashcards

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1
Q

Gap Junctions

A

facilitate passage of inorganic ions and small molecules (K+, Ca2+, H+, cGMP, IP3, cAMP) from one cell to the other.

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2
Q

Name three types of chemical signals.

A
  • Ions (K+, Ca2+, H+, etc)
  • Hormones (endocrine, paracrine, autocrine)
  • Neurotransmitters

Chemical signals are transmitted via a secondary messenger except steroids that diffuse across the plasma membrane and interact with cytosolic or nuclear receptors

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3
Q

How do steroid hormones interact with cells?

A

They diffuse across the plasma membrane and interact with cytosolic or nuclear receptors.

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4
Q

What is the role of the endocrine system?

A

Integrates organ function through hormones that are secreted from glands into the extracellular fluid.

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5
Q

What happens once a hormone is recognized by its target tissue?

A

It can exert its biological action by a process known as signal transduction.

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6
Q

What are the three classifications of hormones based on their chemical structure?

A
  • Peptides
  • Metabolites of single amino acids
  • Metabolites of cholesterol
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7
Q

How do peptide hormones function?

A

They bind to cell-surface receptors and activate a variety of signal transduction systems.

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8
Q

What is the source of steroid hormones?

A

Cholesterol.

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9
Q

What is the function of amine hormones?

A

They are made from tyrosine and tryptophan and act through surface receptors.

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10
Q

How do thyroid hormones regulate metabolic rate?

A

They bind to intracellular receptors as steroids.

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11
Q

What is the mechanism of dopamine inhibition of prolactin?

A

A) Gαi protein-mediated inhibition of cAMP production.
B) Gβi dimer-mediated:
i) activation of inward rectifier K+ channels and
ii) inhibition of voltage-gated Ca2+ channels

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12
Q

What are class-1 cytokine receptors?

A

Transmembrane receptors found on the surface of cells to which cytokines bind.

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13
Q

What role does cyclic adenosine monophosphate (cAMP) play in cellular signaling?

A

Activates protein kinase A (PKA) by binding to it.

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14
Q

What does receptor dimerization in guanylyl cyclases lead to?

A

Activation of guanylyl cyclase activity, converting GTP to cGMP.

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15
Q

What happens when a ligand binds to receptor serine/threonine kinases?

A

It causes transphosphorylation of type-I subunit at serine and threonine residues.

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16
Q

What is the function of receptor tyrosine kinases (RTKs)?

A

Ligand binding leads to receptor dimerization and activation of tyrosine kinase activity.

Ligand binding to the insulin receptor causes confromational changes in each of the two α:β pairs, which lead to activaition of tyrosine kinases on the β-subunits. The activated β-subunits then phosphorylate each other and downstream effectors.

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17
Q

What initiates the activation of protein kinase A (PKA)?

A

Binding of cAMP to the enzyme protein kinase A (PKA).

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18
Q

What is the result of phospholipase C (PLC) activation?

A

Conversion of PIP2 to IP3 and DAG, leading to an increase in intracellular Ca2+.

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19
Q

What do arachidonic acid metabolites include?

A
  • Prostaglandins
  • Prostacyclins
  • Thromboxanes
  • Leukotrienes
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20
Q

What is the definition of a karyotype?

A

The full set of chromosomes in a cell.

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21
Q

True or False: Hormones can only be peptides.

A

False.

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22
Q

What are chromosomes?

A

Nuclear structures containing a linear thread of DNA which transmit genetic information among other functions.

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23
Q

What is the full set of chromosomes in a cell called?

A

Karyotype.

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24
Q

How many types of chromosomes do humans have?

A

Two types: a single pair of sex chromosomes and 22 pairs of autosomal chromosomes.

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25
What are the sex chromosomes for females and males?
Females have two X chromosomes, while males have one X and one Y chromosome.
26
What is the size and shape of the Y chromosome?
The Y chromosome is small and acrocentric.
27
What type of cell division occurs in somatic cells?
Mitosis.
28
What is the result of mitosis?
Formation of two identical daughter cells with the same number of chromosomes (46 in humans) and same DNA content as the original cell.
29
What are the five phases of mitosis?
* Prophase * Prometaphase * Metaphase * Anaphase * Telophase
30
Why do daughter cells remain genetically identical in mitosis?
No exchange of genetic material occurs between homologous chromosomes.
31
What is the difference between mitosis and meiosis?
Mitosis produces two identical daughter cells; meiosis produces four haploid daughter cells.
32
What are the two divisions in meiosis called?
Meiosis-1 and Meiosis-2.
33
What occurs during meiotic division-1?
Recombination and reduction to the haploid number of chromosomes.
34
What is the genetic sex of a zygote determined by?
The fertilization event when an X- or Y-bearing sperm fertilizes an oocyte.
35
How many spermatids are produced from one spermatogonium?
Four spermatids.
36
How many mature oocytes are produced from one oogonium?
One mature oocyte and two polar bodies.
37
What is an epigenetic modification?
A change in phenotype without a change in genotype.
38
What role do histones play in genetics?
They are major protein components of chromatin and act as spools around which DNA winds.
39
What is DNA methylation?
A process where methyl groups attach directly to DNA strands.
40
What are some factors that influence epigenetic changes?
* Environment * Lifestyle * Age * Disease state
41
What is gonadal dysgenesis?
An abnormal gonadal differentiation.
42
What is Turner syndrome characterized by?
Short stature, primary amenorrhea, sexual infantilism, and other congenital abnormalities.
43
What is the karyotype of individuals with Turner syndrome?
45,XO.
44
What is the testis-determining factor (TDF)?
A single gene located on the short arm of the Y chromosome, also known as SRY.
45
What happens in the absence of a Y chromosome during embryogenesis?
The indifferent gonad develops into an ovary.
46
What is an XX male?
An individual with XX sex chromosomes but a male phenotype.
47
What is the result of abnormal exchange of genetic material between X and Y chromosomes?
An XX male.
48
What defines mixed gonadal dysgenesis?
Individuals have testes and a streak ovary, and a 45,XO karyotype.
49
What is the testis-determining factor (TDF)?
A single gene located on the short arm of the Y chromosome, also referred to as SRY (Sex-determining Region Y).
50
What are pseudohermaphrodites?
Individuals with one type of gonadal tissue but morphological characteristics of both sexes.
51
What do the mesonephric (wolffian) ducts develop into in males?
The vas deferens, seminiferous tubules, and ejaculatory duct.
52
What do the paramesonephric (müllerian) ducts develop into in females?
The oviducts (fallopian tubes), uterus, and upper third of the vagina.
53
True or False: The development of the mesonephric ducts requires testosterone.
True.
54
What hormone causes the regression of the müllerian ducts in males?
Anti-müllerian hormone (AMH).
55
What happens to the wolffian ducts in females?
They degenerate.
56
Fill in the blank: The absence of _______ causes the müllerian ducts to develop in a female pattern.
AMH.
57
What is the role of testosterone in male sexual differentiation?
It promotes the development of the wolffian ducts and the differentiation of external genitalia.
58
What are the three hormones essential for male sexual differentiation?
* Testosterone * Dihydrotestosterone (DHT) * Anti-müllerian hormone (AMH)
59
What is the effect of bilateral removal of the testes on sexual differentiation?
It deprives the embryo of testosterone and AMH, leading to female internal and external genitalia development.
60
What occurs in the absence of testosterone during embryogenesis?
The wolffian ducts remain rudimentary and male internal ductal development does not occur.
61
What is required for normal male development of external genitalia?
The conversion of testosterone to dihydrotestosterone (DHT).
62
What does the congenital absence of 5α-reductase result in?
Normal development of the wolffian duct system but impaired virilization of the external genitalia.
63
True or False: The ovary is required for female duct development.
False.
64
What is congenital adrenal hyperplasia?
A condition that may result in ambiguous genitalia in genotypic females due to adrenal function disorders.
65
What are some enzyme deficiencies associated with congenital adrenal hyperplasia?
* 21α-hydroxylase * 11β-hydroxylase * 3β-hydroxysteroid dehydrogenase
66
What is the primary function of Sertoli cells in male differentiation?
They produce anti-müllerian hormone (AMH) and androgen-binding protein (ABP).
67
What does the absence of adequate androgen production lead to?
Sexual ambiguity.
68
What is the role of dihydrotestosterone (DHT) in male sexual differentiation?
It is crucial for virilization of the urogenital sinus and external genitalia.
69
Fill in the blank: In the presence of both ovaries, testosterone promotes development of the _______ ducts.
Wolffian.
70
What happens to the müllerian ducts in the presence of testosterone?
They regress due to the action of AMH.
71
What can result from disorders of adrenal function?
may result from disorders of adrenal function ## Footnote Includes congenital adrenal hyperplasia.
72
What is congenital adrenal hyperplasia?
A condition involving deficiency of several enzymes in steroid synthesis ## Footnote Includes 21α-hydroxylase deficiency, 11β-hydroxylase deficiency, and 3β-hydroxysteroid dehydrogenase deficiency.
73
Which deficiency accounts for approximately 95% of congenital adrenal hyperplasia cases?
21α-hydroxylase deficiency ## Footnote It reduces the conversion of progesterone and 17α-hydroxyprogesterone.
74
What are the consequences of 21α-hydroxylase deficiency?
Leads to virilization in females and ambiguous genitalia ## Footnote Resulting from hypersecretion of adrenal androgens.
75
What is the adrenogenital syndrome?
A condition in female infants resulting from adrenal steroid precursor shunting into androgen pathways ## Footnote Characterized by ambiguous external genitalia resembling male genitalia.
76
What are the two major roles of androgens in male differentiation?
* Trigger conversion of wolffian ducts to male ejaculatory system * Direct differentiation of urogenital sinus and external genitalia
77
What is testicular feminization syndrome?
A condition where genetic males fail to descend testes due to androgen deficiency ## Footnote Associated with 5α-reductase deficiency and complete androgen resistance.
78
What is male pseudohermaphroditism?
A syndrome where individuals have a normal male karyotype but ambiguous external genitalia ## Footnote Caused by defects in androgen action mechanisms.
79
What is the role of 5α-reductase?
Necessary for converting testosterone to dihydrotestosterone (DHT) ## Footnote Deficiency may lead to ambiguous genitalia in males.
80
How does dihydrotestosterone (DHT) compare to testosterone in binding affinity?
DHT binds to androgen receptors with an affinity about 100-fold greater than testosterone ## Footnote DHT-receptor complex binds more tightly to chromatin.
81
What is the function of the androgen receptor?
Acts as a transcription factor that binds to hormone-response elements on DNA ## Footnote Functions as a homodimer (AR/AR).
82
What hormone do Sertoli cells produce?
Antimüllerian hormone (AMH) ## Footnote Also known as müllerian-inhibiting substance (MIS).
83
What is the effect of antimüllerian hormone (AMH)?
Inhibits the development of the Müllerian duct ## Footnote Responsible for the formation of female reproductive structures.
84
What are the receptors associated with steroid hormones?
* GR: Glucocorticoid receptor * MR: Mineralocorticoid receptor * PR: Progesterone receptor * ER: Estrogen receptor * AR: Androgen receptor * VDR: Vitamin D receptor * THR: Thyroid hormone receptor * RAR: Retinoic acid receptor
85
What happens when steroid hormones bind to their receptors?
Stimulates transcription of appropriate genes by binding to steroid response elements (SREs) ## Footnote Hormones enter target cells by simple diffusion.
86
What is the difference between endocrine and paracrine signaling?
Endocrine signaling involves hormones acting on distant tissues, while paracrine signaling acts on neighboring cells ## Footnote Autocrine signaling refers to a cell acting on itself.

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