EXAM 4: Animal Reproduction: Lab Endocrinology

What is endocrinology?

Study of stucture and function of endocrine glands and the role of their secretions (hormones).

What is an endocrine gland?

Organs or groups of cells which produce hormones and secrete them into the vasculature

What is a hormone?

A chemical messenger which travels via the circulation to reach target organs and subsequently elicit a specific effect

Hormone Characteristics

- Present in circulation in LOW amounts

- Inhibit or accelerate reactions in cells

- Are not secreted at constant rates

- Require a specific receptor

Inhibin

Inhibits secretion of FSH from anterior pituitary

Endocrine: Mode of Transmission

Circulation via bloodstrem. (Hormones transported by the blood to act on a distant organ)

Neuroendocrine: Mode of Transmission

Hybrid; Nerve secretes its chemical messenger, is taken into a capillary and carried to many cells.

Paracrine: Mode of transmission

Hormones simply diffuse directly to neighboringtarget cells, by-passing the circulatory system.

Autocrine: Mode of Transmission

A given cell may respond to its own hormone secretion.

Releases hormone and the hormone binds to receptor on the same cell

Neuroendocrine communication Examples

GnRH / CRH

Neural Communication Example

Acetylcholine / Norephinephrine

Endocrine Communication examples

FSH / LH

What cellular organelle is responsible for converting Cholesterol into pregnenolone?

The Mitochondria

Steriod hormones diffuse through what?

Cell membranes

Steriord hormones are all synthesized from what?

Cholesterol

What is the chemical difference between testosterone and estrogen?

One Carbon difference

Steriods: Cholesterol is converted to what?

Pregnenolone

Through enzymatic conversion, pregnenolone is converted to what?

Progesterone which converts to testosterone through enzymatic conversion as well

Testosterone steriod is converted to what with aromatase enzyme?

Estradiol

Rough ER is responsible for

Protein synthesis and membrane production

GnRH is what kind of hormone?

Peptide hormone (Protein)

Prostaglandins

Modified fatty acids that are produced by a wide range of cells.

What prostaglandins are we concerned with?

F2 alpha , E during

Can prostaglandins pass through the cell membrane

Yes, so there wil typically be receptors inside the cell

Asprin inhibits what?

The conversion into prostaglandin synthase.

Prostaglandin causes inflamation/pain

Steriod Hormone Pathway

1. Duffusion through capillary wall

2. Diffusion through plasma membrane

3. Steroid binds to receptor inside cell

4. Initiation of transcription

5. Cell responds by synthesizing new proteins

Protein Hormone Pathway

1. Transport across capallary wall

2. Binds to plasma membrane receptor on outside of cell

3. Initiation of signal transduction cascade

4. Initiation of transcription

5. Cell responds by synthesizing new proteins

Thecal Cell Stimulate what?

Well LH binds to the cells, it stimulates the coversion of cholesterol, progesterone, and testosterone

Granulosa Cell stimulate what

When FSH binds the cells, it stimulates the conversion of testosterone to estrogen that then diffuses into circulation of blood stream

GnRH (Gonadotropin Releasing Hormone)

- Decapeptide (Structure)

- Hypothalamus (Origin)

- Anterior Pituitary Gland (Target)

- Stimulates the release of FSH and LH (Function)

LH (Luteinizing Hormone)

Structure: Glycoprotein

Orgin: Anterior Pituitary

Targets:

1 (M). Testis (leydig cells)

2(F). Ovaries (Techal and luteal cells )

Function: 1(M).Stimulates testosterone production

2(F). Induces formation of the CL as well as progesterone secretion

FSH ( Follicle Stimulating Hormone):

Structure: Glycoproteins

Origin: Anterior Pituitary

Targets:

1.(M): Testeris (Sertoli Cells wall of seminiferial tubials)

2.(F): Ovaries (Granulosa Cells)

Functions:

1.(M): Sertolic cell function and spermatogenesis

2.(F): Follicular Development, and Estradioal Synthesis

Prolactin

Structure: Glycoprotein

Origin: Anterior Pituitary

Targets: Mammary Glands

Function: Stimulates milk production

Oxytocin (OT)

Structure: Octapeptide

Origin: Synthesized in Hypothalamus and stored in posterior pituitary

Targets:

1(M): Smooth muscle of the epidimal tail, vas deferens, and ampulla

2(F): Myometrium, endometrium, and mammary gland

Functions:

1(M): Stimulates PGF2a synthesis

2.(F): Leads to muscle contraction around the milk, suckling

Estradiol (E2) Estrogen

Structure: Steriods

Origin:

1.(M): Testis (Sertoli cells)

2.(F): Follicles (granulosa cells)

Target:

- Hypothalamus & Pituitary

- Entire Reproductive Tract

Function:

- Regulate GnRH release

- Elevate Secretory activity

- Sexual Behavior (Heat)

Progesterone (P4)

Structure: steroid

Origin: Corpus Luteum & Placenta (species specific)

Targets: endometrium, myometrium, hypothalmus, & mammary glands

Function: maintenance of pregnancy, inhibit GnRH release, mammary growth and secretion

*CIDRs utilize progesterone to synchronize estrus

Testosterone (T) - Male

Structure: Steroid

Origin: Testis (leydig cells)

Tragets:

Sertoli cells, Accessory Sex gland

Brain and skeletal muscle

Function:

Spermatogenesis

Accessory Gland Secretion

Secondary Sex characteristics

Testosterone (T) Female

Structure: Steroid

Origin:

Follicles (thecal cells)

Target:

Follicles (granulosa cells)

Function:

Substrate for E2 stynthesis

Hypothalamic-Hypophyseal Gonadal Axis

The relationship between the hypothalamus - hypophysis (Pituitary Gland) and the gonads (ovaries or testes). Disruption at any level can result in disease.

True or False:

Most hormones rely on negative feedback mechanism to limit their production and secretion in order to maintain the appropriate concentration circulating through the body

True

True or False:

Both testosterone and estradiol are produced by males and females and play important roles in regulating reproductive function and behavior

True