Reproductive Regulation

Nervous and endocrine

The reproductive system is regulated by interplay between what two systems?

Neural control

Which type of reproductive regulation is fast acting?

Nervous system

Transduces external stimuli into neural signals which brings about a change in reproductive organs and tissues

Simple Neural reflexes

Nerves release neurotransmitters directly onto target tissues; direct innervation of the target tissue by neuron

Neuroendocrine reflexes

A message released by a neuron (neurohormone) enters the blood and acts on the target tissue; no direct innervation

Pineal gland

Which endocrine gland is involved with seasonal breeders?

Pituitary gland

Which endocrine gland is located at the base of the brain?

Parturition

The adrenal cortex is highly involved with hormones for what stage of reproduction?

Placenta

Which component of the reproductive system produces a lot of different hormones towards the end of gestation?

Neural

Which type of control is faster acting? Neural or endocrine?

Simple neural reflex

Which type of reflex has direct innvervation and involves the use of neurotransmitters?

Neuroendocrine reflex

Which type of reflex has no direct innervation and involves the use of neurohormones?

The message is slower because it has to travel all the way to the brain and the signal comes through the blood

What is different about an neuroendocrine reflex compared to a simple neural reflex?

Simple neural reflex

Muscles for sexual behavior and ejaculation, muscles for scrotal tone, and scrotal sweat glands are all controlled by what type of reflex?

Neuroendocrine reflex

Sperm movement into the ductus deferens and milk ejection are controlled by what reflex?

Simple neural reflexes

Nerves release messages directly onto target tissue and utilize direct innervation

Neurotransmitter

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

Neuroendocrine reflexes

A substances is released by a neuron and enters the blood to act on target tissue; doesn’t involve direct innervation

Excitatory Neurons

Increase the probability of a nerve firing

Inhibitory Neurons

Decrease the probability of a nerve firing

Postsynaptic action potential

Firing of a nerve

Hypothalamus

Neural control center for reproductive system; complex portion of the brain consisting of clusters of nerve cell bodies

Hypothalamic Nuclei

Clusters of nerve cell bodies in the brain

Surge center, tonic center, and periventricular nucleus

What are the three hypothalamic nuclei involved in reproductive regulation?

Third ventricle

What is the landmark to find the hypothalamus?

Surge center

Nerve center responsible for triggering massive release of gonadotropin releasing hormone which will ultimately drive ovulation

Tonic Center

Region that controls continuous secretion of gonadotropin releasing hormone in regular, low amplitude pulses

Periventricular nucleus

Region responsible for oxytocin production

Ventricular system

Filled with cerebrospinal fluid that continually circulates through ventricles of subarachnoid spaces of the central nervous system

Lateral ventricles, third ventricle, fourth ventricle, central canal

What are the components of the ventricular system involved in reproductive regulation?

Hypothalomo-Hypophyseal Portal System

Responsible for carrying hypothalamic hormones specifically to the anterior pituitary without dilution in the systemic blood

Allows rapid response

Little dilution of peptide hormones

Peptide hormones have a short half life

What are special characteristics of the hypothalamo-hypophyseal portal system that wouldn’t be possible in systemic blood?

Specific hypothalamic nuclei secreting releasing or release inhibiting factors

What controls the release of pituitary hormones?

LH and FSH

What does GnRH stimulate the release of?

Median Eminence

What controls tonic (consistent) LH release?

Hypothalamic-Pituitary-Gonadal Axis

Regulates all of reproduction from a hormonal side of things

Gonadotropes, Somatotropes, Lactotropes, Corticotropes, and Thyrotropes

What are the five cell types in the anterior pituitary gland?

Check and balance system

In the HPG Axis, what do steroid hormones act as?

GnRH

In the HPG Axis, what does the hypothalamus release that goes to the anterior pituitary gland?

LH

In the HPG Axis, what does the anterior pituitary release that goes to the gonads?

Steroid hormones

In the HPG Axis, what do the gonads release that goes back to the hypothalamus?

Negative feedback

In the HPG Axis, what type of feedback is involved from the gonads to the hypothalamus?

Gonadotrophs

specialized endocrine cells in the anterior pituitary gland that synthesize and secrete the gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH)

Corticotrophs

specialized basophilic cells in the anterior pituitary gland that produce and secrete pro-opiomelanocortin (POMC), which is cleaved into adrenocorticotropic hormone (ACTH), lipotropin, and melanocyte-stimulating hormone (MSH)

Lactotrophs

specialized endocrine cells in the anterior pituitary gland that synthesize and secrete the hormone prolactin

Somatotrophs

specialized endocrine cells in the anterior pituitary gland that synthesize and secrete growth hormone (GH), also known as somatotropin

Thyrotrophs

pecialized endocrine cells in the anterior pituitary gland that produce and secrete thyroid-stimulating hormone (TSH)

Alpha subunit

What has to combine with a specific beta subunit to create a specific hormone?

Periventricular nucleus

What component of the hypothalamus is associated with the posterior pituitary gland?

Hormone

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

Yes

Can a hormone be active in the same tissue which it is produced?

Endocrine control

Which type of control is slow acting?

Autocrine

a cell (tissue) produces a hormone that acts on the same cell (tissue)

Paracrine

a cell (tissue) produces a hormone that acts on a nearby cell (tissue)

Endocrine

a cell (tissue) produces a hormone that acts on a remote cell (tissue); Generally enters blood to get there

Half-life

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

By source, mechanism of action, and biochemistry

What are the three ways that hormones can be classified?

Protein, steroids, and prostaglandins

What are the three types of biochemical classifications for hormones?

Act in minute quantities

Short half-lives

Bind to specific receptors

Regulate intracellular biochemical reactions

What are the four main characteristics of reproductive hormones?

Receptors on target tissue

For a hormone to act, what must it interact with?

Peptide, protein, and glycoprotein

What are the three types of protein hormones?

Peptide hormone

Less than 20 amino acids, only contains peptide bonds, mainly come from hypothalamus, small so can’t go very far before they’re broken down

Protein hormone

Made up of long chains of amino acids, only contains peptide bonds, comes from the anterior pituitary

Glycoprotein hormone

Protein hormone comprised of a common alpha subunit and a unique beta subunit, amino acids have carbohydrate molecules attached to them, must break down hydrogen bonds, Van der Waals forces, covalent bonds, and peptide bonds

Steroid hormones

Synthesized from cholesterol which is derived from acetate, comprised of 4 acetate rings, cholesterol converted by enzymes

Cyclopentanoperhydrophenanthrene nucleus

What is the core of all steroid hormones?

27

How many carbons are in cholesterol?

21

How many carbons are in progesterone?

19

How many carbons are in testosterone?

18

How many carbons are in estradiol-17 beta?

Agonist

Binds to a receptor and elicits the same biological effect as a native hormone

Antagonist

Binds to a receptor but does not elicit the same biological effect as a native hormone

Long half life in blood system, not degraded in liver as quickly

Can be given orally (implant)

Have strong affinity for receptors

What are some characteristics of agonists of various steroid hormones?

Estrogenic

Agonists of estrogen

Progestins

Agonists of progesterone

Diethyllstilbestrol

Zeranol

Testosterone Propionate

Estradiol Benzoate

What are some examples of estrogenics?

Norgestomet

Melengestral Acetate

What are some examples of progestins?

Prostaglandin hormones

Derived from fatty acids and phospholipids, base compound of all is arachidonic acid, 20-carbon unsaturated hydroxy fatty acids, rapdily degrade in the blood

Prostate gland

Where were prostaglandins first believed to come from?

Prostaglandins

What is one of the most ubiquitous, physiologically active substances in the body?

Produced by all tissues of body

Can have local effect on tissues (same tissue which produced it)

Rapidly degrade in lungs

What are some general characteristics of prostaglandins?

Prostaglandin E2

Causes vasodilation of blood vessels, maintains CL during ovulation and embryo implantation

Prostaglandin F2 alpha

Causes vasoconstriction of blood vessels, effects luteal cell of CL with lutalyse causing CL to regress, involved with ovulation, parturition, and sperm transport

Protein hormones

Which type of hormone has a half-life of minutes to hours?

Steroid hormones

Which type of hormone has a half-life of hours to days?

Prostaglandins

Which type of hormone has a half-life of seconds to minutes?

Glycoprotein (45% carbon)

What type of hormone is eCG, and if applicable what percent carbon is it?

Steroid (18 carbons)

What type of hormone is estradiol-17 beta, and if applicable what percent carbon is it?

Steroid (19 carbons)

What type of hormone is testosterone, and if applicable what percent carbon is it?

Prostaglandin

What type of hormone is PGE2, and if applicable what percent carbon is it?

Steroid (19 carbons)

What type of hormone is progesterone, and if applicable what percent carbon is it?

Protein

What type of hormone is ACTH, and if applicable what percent carbon is it?

Peptide

What type of hormone is oxytocin, and if applicable what percent carbon is it?

Peptide

What type of hormone is GnRH, and if applicable what percent carbon is it?

Glycoprotein (8% carbon)

What type of hormone is FSH, and if applicable what percent carbon is it?

Protein

What type of hormone is Prolactin, and if applicable what percent carbon is it?

Steroid (26 carbons)

What type of hormone is estradiol cypionate, and if applicable what percent carbon is it?

Prostaglandin

What type of hormone is PGF2 alpha, and if applicable what percent carbon is it?

Glycoprotein (2% carbon)

What type of hormone is LH, and if applicable what percent carbon is it?

Glycoprotein (30% carbon)

What type of hormone is hCG, and if applicable what percent carbon is it?