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ASCI 341 > CH 5 Regulation of Reproduction - Nerves, Hormones, and Target Tissues > Flashcards

CH 5 Regulation of Reproduction - Nerves, Hormones, and Target Tissues Flashcards

1
Q

What are simple neural reflexes?

A

Nerves release messages (neurotransmitters) directly onto target cells

Direct innervation of the target tissue by a single neuron (neurosecretory cell)

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2
Q

What are neuroendocrine reflexes?

A

A substance (message) released by a neuron (a neurohormone) enters the blood and acts on the target tissue.

No direct innervation

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3
Q

Order of neural reflex

A

Sensory (afferent nerves) –> synapse –> interneurons in spinal cord –> synapse –> efferent nerves –> neural action –> target tissue

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4
Q

What is a neurotransmitter?

A

Substance of small molecular weight which is released from nerve terminals that causes other nerves to “fire” or causes contraction of smooth muscle that stimulates reproductive tract

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5
Q

Order of neuroendocrine reflex

A

Sensory (afferent) nerves –> synapse –> interneurons in spinal cord –> synapse –> efferent nerves –> synapse –> hypothalamus –> hormonal action –> target tissue

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6
Q

What is postsynaptic action potential?

A

“fixing of a nerve”

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7
Q

What do excitatory neurons do?

A

Release excitatory neurotransmittors

^ probability of nerve “firing”

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8
Q

What do inhibitory neurons do?

A

Release inhibitory neurotransmitters
v probability of a nerve “firing.”

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9
Q

What types of neurons do neuroendocrine reflexes utilize?

A

excitatory neurons

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10
Q

What is the hypothalamus?

A

Neural control center for reproductive hormones

Complex portion of brain consisting of clusters of nerve cell bodies (hypothalamic nuclei)

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11
Q

What do hypothalamic nuclei surround?

A

Surround cavity in the center of the brain - 3rd ventricle

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12
Q

What 2 groups are important in reproduction?

A
  • surge center
  • tonic center
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13
Q

What is the hypothalamo-hypophyseal portal system?

A

Axons from surge center and tonic centers extends into pituitary stalk - nerve endings terminate on a highly specialized capillary network

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14
Q

Where is another center located and what does it produce?

A

Periventricular nucleus (PVN)

Produces oxytocin

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15
Q

What does surge center and tonic center produce?

A

These secrete gonadotropin-released hormone (GnRH)

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16
Q

How does endocrine control work (fast or slow)?

A

“slow acting”

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17
Q

What is a hormone?

A

A substance produced by a gland that acts on a remote tissue (target tissue) to bring about a change in tissue

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18
Q

What is the half-life?

A

Time required for one-half of a quantity of a hormone to disappear from the blood or from the body

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19
Q

What are the characteristics of reproductive hormones?

A
  • act in minute quantities
  • short half-lives
  • bind to specific receptors
  • regulate intracellular biochemical reactions
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20
Q

What must a hormone do to act?

A

For a hormone to act, must interact with a RECEPTOR. So, in order to a hormone to act on a specific target tissue, that tissue MUST contain a RECEPTOR. Binding of a HORMONE to its RECEPTOR induces a series of changes to the cell containing the RECEPTOR. These changes result in the cell performing a function.

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21
Q

What are hormones classified by?

A

Hormones can be classified by source, target tissue, and primary actions

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22
Q

Where to reproductive hormones originate from?

A
  • hypothalamus
  • anterior and posterior pituitary
  • gonads
  • uterus
  • placenta
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23
Q

Where are hypothalamic hormones produced? What is their function?

A

Produced by neurons in the hypothalamus

Cause release of other hormones by the anterior pituitary gland

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24
Q

What are hypothalamic hormones also referred to as? What size are they?

A

Also called neuropeptides.

Generally less than 20 amino acids

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25
Q

What is an example of hypothalamic hormones?

A

Gonadotropin-releasing hormone (GnRH)

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26
Q

Where are pituitary hormones released?

A

Released into blood from anterior and posterior pituitary glands

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27
Q

What are examples of pituitary hormones?

A

Follicle Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
Prolactin
Oxytocin (primary hormone from posterior pituitary)

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28
Q

Where do gonadal hormones originate from and what is their function?

A

Originate from the gonads

Affect function of hypothalamus, anterior pituitary, and tissues of the reproductive tract. Induce secondary sex characteristics.

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29
Q

Examples of ovary hormones

A

estrogens, progestogens, inhibin, some testosterone, oxytocin, and relaxin

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30
Q

Examples of testes hormones

A

testosterone and other androgens, inhibin, and some estrogens

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31
Q

Examples of uterus hormones

A

Prostaglandin F2a

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32
Q

Examples of placenta hormones

A

progesterone, estrogen, equine chorionic gonadotropin (eCg), humane chorionic gonadotropin (hcG)

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33
Q

What are the 3 ways in which hormones can act?

A
  1. Autocrine - a cell (tissue) produces a hormone that acts on the same cell/tissue
  2. Paracrine - a cell (tissue) produces a hormone that acts on a nearby cell
  3. Endocrine - a cell (tissue) produces a hormone that acts on a remote cell tissue. Generally enters blood to get there.
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34
Q

What do reproductive hormones function as?

A
  • neurohormones
  • releasing factors for other hormones
  • gonadotropins
  • steroids (sexual promoters)
  • pregnancy maintenance hormones
  • luteolytic hormones
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35
Q

What are neurohormones?

A

Synthesized by neurons and released directly into blood. Cause a response in target tissues elsewhere in the body

Ex: oxytocin

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36
Q

What are releasing hormones?

A

Synthesized by neurons and cause release of other hormones from the anterior pituitary. Can also be classified as neurohormones.

Ex: GnRH

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37
Q

What are gonadotropins?

A

Released by gonadotrope cells of the anterior pituitary gland

“tropin” - having an affinity for
So, affinity for the gonads

Ex: FSH and LH

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38
Q

FSH

A

causes follicular growth in ovary

stimulates sertoli cells in the testis (spermatogenesis)

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39
Q

LH

A

causes ovulation and stimulation of CL in the ovary

causes testosterone production in the tesis

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40
Q

What are steroids?

A

Sexual promotors -
Produced by gonads to stimulate reproductive tract, to regulate function of the hypothalamus and anterior pituitary, and to regulate reproductive behavior

Cause development of secondary sex characteristics

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41
Q

What are pregnancy maintenance hormones?

A

High concentrations during pregnancy

Ex: equine chorionic gonadotropin (eCG), human chorionic gonadotropin (hCG), and placental lactogen (mammary gland development)

42
Q

What are luteolytic hormones?

A

Cause destruction of the CL - “lytic” = lysis

Prostaglandin F2a (PGF2a)

43
Q

What are general metabolic hormones?

A

Promote metabolic well-being
Exert indirect effect on reproduction

Ex: Growth hormone - helps regulate growth, lactation, and protein metabolism

44
Q

What are the 3 types of hormone biochemical classifications?

A
  • protein hormones
  • steroids
  • prostaglandins
45
Q

What are peptides?

A

Protein hormones

< 20 amino acids

46
Q

What are glycoproteins?

A

polypeptide hormones which contain carbohydrate moietis

Much larger - 70 kD

47
Q

What are glycoproteins composed of?

A

can be composed of two side-by-side polypeptide chains with carbohydrates attached to each chain

48
Q

What increases half-life of glycoproteins?

A

^ amount of carbohydrate = ^ half-life

49
Q

What are chains of glycoproteins?

A

a and B chains

a –> common
B –> unique

50
Q

Anterior pituitary glycoproteins

A

Hormones all contain the same a-subunit but a unique B-subunit

51
Q

What is the half life of glyocproteins?

A

minutes to hours

52
Q

What are steroids synthesized from, and what are they composed of?

A

Synthesized from cholesterol

Composed of 4 acetate rings

53
Q
A

Cholesterol

54
Q
A

Progesterone

55
Q
A

Testosterone

56
Q
A

Estradiol

57
Q

What is the half-life of steroids?

A

hours to days

58
Q

What are prostaglandins? What are they synthesized from?

A
  • First believed to come from prostate gland, thus the name
  • First only found in mammalian nsemen
  • One of the most ubiquitous, physiological active substances in the body

Synthesized from arachidonic acid

59
Q
A

Arachidonic acid

60
Q
A

PGF2a

61
Q
A

PGE2

62
Q

Why don’t all organs respond to the hormone if hormones travel through the blood and all organs are exposed?

A

In order to respond, the cells within that organ must have specific receptors for that hormone - organs or tissues with these cells are called target tissues

Receptors have specific affinity (attraction) for its hormone

63
Q

Where are protein hormone receptors?

A

Receptors are part of plasma membane

64
Q

What are the 3 different regions (receptor domains)?

A
  • Extracellular domain –> site which binds to specific hormone
  • Transmembrane domain –> changes its configuration and activates other protein hormones (GProteins) in response to hormone binding at the extracellular domain
  • Intracellular domain –> function unclear
65
Q

Steps of protein hormone action

A
  • Hormone-receptor binding
  • Adenylate cyclase activation
  • Protein kinase activation
  • Synthesis of new products
66
Q

What is hormone receptor binding?

A

Fitting to adjacent pieces of a puzzle

Specific geometric configuration of receptor fits specific geometric configuration of hormone

Affinity varies among hormones

67
Q

What is adenylate cyclase activation?

A

Hormone-receptor complex activates a membrane-bound enzyme –> adenylate cyclase

This is mediated by a membrane-bound protein –> GProtein

Activation of adenylate cyclase –> causes conversion of ATP to cAMP within cytoplasm of cell
cAMP is called a “secondary messenger”

68
Q

How does synthesis of new products work?

A

Products made by cell are generally secreted by the cell

Ex: FSH and LH bind to follicle cells and induce them to synthesize estadiol

69
Q

How are steroid hormones transported?

A

Due to lipid solubility - steroids are passively transported through the cell membrane and bind to receptors within the nucleus of target cells, only

70
Q

Steps of steroid hormone action

A
  • steroid transport
  • movement through the cell membrane and cytoplasm
  • binding of steroid to nuclear receptor
  • mRNA synthesis and protein synthesis
71
Q

What is steroid transport?

A

Steroids are lipids so are not water soluble - can’t be transferred as free molecules

Must attach to molecules that are water soluble

Some have specific carrier proteins. Carrier proteins transport steroids in the blood to the cell membrane of target cells

72
Q

What is movement through the cell membrane and cytoplasm?

A

When carrier protein-steroid complex reaches the cell membrane of target cell, steroids dissociate and diffuses through plasma membrane because of lipid solubility. Diffuses through the cytoplasm and into the nucleus

73
Q

What is binding of steroid to nuclear receptor?

A

Steroid binds to nuclear receptor - if target cell like protein hormones, steroid mist “fit” receptor

Steroid receptor complex induces DNA transcription

74
Q

What is mRNA synthesis and protein synthesis?

A

Newly synthesized mRNA leaves nucleus and attaches to ribosomes where it directs protein synthesis

75
Q

What does physiological activity of a hormone depend on?

A
  • Pattern and duration of secretion
  • Half-life
  • Receptor density (# of receptors)
  • Receptor-hormone afifnity
76
Q

What is hormone potency influenced by?

A
  • Receptor density
    Up-regulation - promote synthesis of receptor
    Down-regulation - inhibit synthesis of receptor
  • Hormone receptor density
77
Q

What is the difference between agonists and antagonists?

A

An agonist is a drug that binds to the receptor, producing a similar response to the intended chemical and receptor. Whereas an antagonist is a drug that binds to the receptor either on the primary site, or on another site, which all together stops the receptor from producing a response.

78
Q

Where are steroid hormones metabolized?

A

In the liver

79
Q

What are the two methods of steroid metabolism in the liver?

A
  1. Double bonds within the steroid become saturated - leads to double bond reduction and inactivity of the hormone
  2. Attachment of sulfate or glucuronide residue - makes water soluble, allows hormone to be secreted in urine and feces
80
Q

Where are protein hormone degraded?

A

Degraded in the liver and kidneys

81
Q

How does the liver degrade protein hormones?

A

Removal of glycosylation sites (polysaccharide side chains)
- Allows molecule to bind to liver cells
- Internalized and degraded in cytoplasm

82
Q

How do the kidneys degrade protein hormones?

A

Glycoprotein hormones <55,000 Daltons filtered through glomerulus
- Secreted into urine and elimated

83
Q

Why can protein hormones not be given orally?

A

Degraded by digestive tract

84
Q

What are the two methods hormones can be detected in physiologic fluids?

A
  1. Radioimmunoassay - RIA
  2. Enzyme-linked immunosorbent assay - ELISA
85
Q

What is Radioimmunoassay - RIA?

A
  • Radioactive hormones compete with native hormone (non-reactive)
  • Amount of radioactive hormone that binds is inversely proportional to the concentration of unlabeled hormone in the animal’s blood
86
Q

What is Enzyme-linked immunosorbent assay - ELISA?

A
  • Similar to RIA
  • Advantage of no radioactivity
  • Series of well-controlled steps to determine presence or absence of hormone
  • Can also determine quantity of hormone present
  • Relatively inexpensive

Ex: pregnancy test in hormone

87
Q

What is the hypothalamo-hypophyseal portal sytem?

A

Carries hypothalmic hormones specifically to the anterior pituitary without dilution in the systemic blood

  1. Allows rapid response
  2. Little dilution of peptide hormones
  3. Peptide hormones
88
Q

What does GnRH stimulate?

A

Preovulatory LH surge is controlled by Gonadotropin Resleasing Hormone from the surge center. GnRH stimulates release of LH and FSH

89
Q

What is tonic LH release controlled by?

A

Median Eminence (ME)

90
Q

What is unique about synthetic hormones?

A

Long 1/2 life in blood system, not degraded in the liver as quickly
- can be given orally
- have strong infinity

91
Q

What is the general 1/2 life rude for steroid hormones?

A

Hours - days

92
Q

What are the agonists of estradiol?

A

Zeranol
Diethystibesterol
Estradiol benzoate

93
Q

Characteristics of lipid hormones / prostaglandins

A
  1. Produced by all tissues in the body
  2. Can have local effect on tissues (same tissue which produced it)
  3. Rapidly degraded in lungs
94
Q

What are general roles of PGE2?

A
  • causes vasodilation of blood vessels
  • maintain CL ovulation, embryo implantation
95
Q

What are general roles of PGF2a?

A
  • causes vasoconstriction of blood vessels
  • effects luteal cell of CL. Luralyse causes CL regression
  • Involved with ovulation, paturition, sperm transport
96
Q

What are lipid hormones/prostaglandins derived from?

A

Arachidonic acid

97
Q

What is the location of receptor for protein and peptide hormones?

A

Receptor is in plasma membrane

98
Q

What is the location of receotors for steroid hormones?

A

Receptor is in nucleus

99
Q

What is the location of receptors for prostaglandin hormones?

A

Receptor is in the plasma membrane

100
Q

What are the 3 types of hormone release?

A

Episodic –> associated with hormones under nervous control

Basal –> hormone stays low but fluctuates with amplitude pulses

Sustained –> hormone remains elevated but in a relatively steady fashion for a long period of time

ASCI 341 (13 decks)

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