Nervous and Endocrine Systems in Reproduction

A Comprehensive collection of vocabulary cards covering the endocrine and nervous regulation of reproduction, anatomy, physiological cycles, and assisted reproductive technologies.

Simple neural reflex

A pathway where sensory afferent neurons detect a stimulus, deliver it to the spinal cord, and efferent neurons release neurotransmitters at the target tissue for a response (e.g., ejaculation).

Neuroendocrine reflex

A reflex involving the hypothalamus releasing neurohormones into the blood to trigger pituitary hormone release, resulting in broader and longer-lasting effects (e.g., suckling reflex).

Hypothalamic-pituitary portal system

A network of blood vessels crucial for the regulated release of $GnRH$ from the hypothalamus into the anterior pituitary gland.

Surge center

A hypothalamic nucleus unique to females that enables the cyclic release of $GnRH$ triggered by high estradiol levels to induce the $LH$ surge for ovulation.

Tonic center

A region in the hypothalamus responsible for the basal, pulsatile secretion of $GnRH$ in both males and females.

Paraventricular nucleus (PVN)

The hypothalamic nucleus responsible for the production of oxytocin and other neurohormones.

Follicle-stimulating hormone (FSH)

An anterior pituitary hormone that promotes ovarian follicle development in females and spermatogenesis in males.

Luteinizing hormone (LH)

An anterior pituitary hormone that triggers ovulation and corpus luteum formation in females and testosterone production in males.

Negative feedback

A mechanism where high levels of one hormone (e.g., progesterone) suppress the release of another (e.g., $GnRH$) to maintain homeostasis.

Glycoproteins

Reproductive hormones (like $FSH$, $LH$, and Inhibin) composed of two polypeptide chains with carbohydrates that provide stability and resistance to degradation.

Steroids

Lipid hormones derived from a cyclopentanoperhydrophenanthrene nucleus; they are lipophilic and can enter cells directly (e.g., Estrogen, Progesterone, Testosterone).

Adenylate cyclase

An enzyme activated by $G-proteins$ in the protein hormone mechanism that converts $ATP$ into cyclic $AMP$ ($cAMP$).

Aromatase

The enzyme responsible for converting testosterone into estradiol, found in the brain (for defeminization) and in granulosa/Sertoli cells.

Broad ligament

A double layer of peritoneum that supports the female reproductive tract, divided into the mesometrium, mesovarium, and mesosalpinx.

Cervix

An anatomical barrier producing sialomucin ($low-viscosity$) and sulfomucin ($high-viscosity$) to filter sperm and protect the uterus from infections.

Ovarian cortex

The outer region of the ovary housing oocytes, follicles, corpora lutea, and corpora albicans (except in mares, where it is internal).

Folliculogenesis

The maturation process of ovarian follicles starting from primordial follicles through to mature Graafian follicles.

Zona pellucida

A glycoprotein layer that forms around the oocyte during the primary follicle stage and is essential for sperm binding.

Antrum

The fluid-filled cavity characteristic of tertiary and Graafian follicles.

Alpha-fetoprotein

A protein in female fetuses that binds to estradiol, preventing it from crossing the blood-brain barrier and resulting in the feminization of the hypothalamus.

Defeminization

The process in male fetuses where testosterone enters the brain, is converted to estradiol, and inhibits the formation of the $GnRH$ surge center.

Leptin

A peptide hormone produced by adipocytes that signals nutritional adequacy to $GnRH$ neurons, facilitating the onset of puberty.

Polyestrus

Animals (e.g., swine, cattle) that exhibit a uniform distribution of estrous cycles throughout the year.

Seasonally polyestrus

Animals that cycle only during specific seasons: short-day breeders (sheep/goats) in fall and long-day breeders (mares) in spring.

Luteolysis

The breakdown of the corpus luteum, primarily induced by $PGF2\text{α}$, leading to a drop in progesterone and the restart of the estrous cycle.

2-Cell, 2-Gonadotropin model

The mechanism where $LH$ stimulates theca interna cells to produce testosterone, which then diffuses to granulosa cells to be converted to estradiol by $FSH$.

Collagenase

An enzyme activated by progesterone after the $LH$ surge that breaks down follicle wall collagen to create the stigma for ovulation.

Large luteal cells (LLC)

Luteal cells derived from granulosa cells that undergo hypertrophy and produce oxytocin, relaxin, and progesterone.

Small luteal cells (SLC)

Luteal cells derived from theca interna cells that undergo hyperplasia and contribute to progesterone production.

Countercurrent heat exchange

The mechanism in the pampiniform plexus where cooler venous blood absorbs heat from arterial blood to maintain lower testicular temperatures.

Sertoli cells

Cells in the seminiferous tubules that nourish developing sperm and produce androgen-binding protein ($ABP$) and inhibin.

Blood-testis barrier

A structure formed by tight junctions between Sertoli cells that protects haploid germ cells from the immune system.

Pampiniform plexus

A network of veins in the spermatic cord that regulates testicular temperature and enables the recirculation of testosterone.

Epididymis

An excurrent duct system where sperm acquire motility and fertility; divided into the head, body, and tail (storage).

Spermiogenesis

The differentiation phase of spermatogenesis where round spermatids transform into mature spermatozoa.

Acrosome

A cap-like structure on the sperm head containing enzymes like acrosin and hyaluronidase for penetrating the zona pellucida.

Capacitation

The biochemical changes in the female tract (uterus/oviduct) that remove inhibitory seminal proteins to make sperm capable of fertilization.

Cortical reaction

The release of cortical granules after sperm-oocyte fusion to create a zona block and vitelline block, preventing polyspermy.

Syngamy

The fusion of the male and female pronuclei to form a single diploid zygote.

Extraembryonic membranes

The four specialized membranes (yolk sac, amnion, allantois, and chorion) that support the developing fetus.

Interferon tau ($IFN-τ$)

The biochemical signal for maternal recognition of pregnancy in cows and ewes that inhibits oxytocin receptor synthesis to prevent luteolysis.

Parturition trigger

The activation of the fetal $hypothalamus-pituitary-adrenal (HPA)$ axis, leading to increased fetal cortisol and the removal of the progesterone block.

Colostrum

The first mammary secretion after parturition, rich in immunoglobulins to provide passive immunity to the neonate.

Placentome

The placental unit of attachment in ruminants, consisting of a fetal cotyledon and a maternal caruncle.

Epitheliochorial placenta

The least invasive type of placenta (sows, mares) where all maternal and fetal tissue layers remain intact.

Hemochorial placenta

The most invasive placenta (primates, rodents) where the chorionic epithelium is directly bathed in maternal blood.

Spermogram

The evaluation of semen based on number (concentration), quality (morphology), and motility to assess fertility potential.

Cryopreservation

The process of freezing semen at $-196^{\text{o}}C$ in liquid nitrogen using cryoprotectants like glycerol to prevent ice crystal damage.

MOET (Multiple Ovulation and Embryo Transfer)

An assisted reproductive technology used to increase offspring from genetically superior females through superovulation and embryo flushing.

Superovulation

The administration of exogenous gonadotropins (like $FSH$) to stimulate the ovaries to produce a higher than normal number of mature follicles.