Reproductive Endocrinology Lecture Notes Flashcards
What in the nervous system regulates reproduction?
Simple neural reflexes and neuroendocrine reflexes
What in the endocrine system regulates reproduction?
Hormones
Differentiate neural reflexes from neuroendocrine reflexes.
In neural reflexes, a receptor detects a stimulus, and an afferent neuron transmits that information to the central nervous system, which determines the appropriate response. An efferent neuron then carries the response signal to the target tissue.
Neuroendocrine reflexes happen when a signal is sent from the spinal cord to the hypothalamus, which then releases hormones into the bloodstream, which then go to the target tissue.
What is the endocrine system and what are its three basic components?
An integrated network of multiple organs derived from different embryologic origins that release hormones ranging from small peptides to glycoproteins, which exert their effects either in neighboring or distant target cells. Components: endocrine glands, hormones, and target tissue.
Do endocrine glands have ducts?
No
Which endocrine glands are involved in reproduction?
Hypothalamus, pituitary, pineal, gonads, uterus, placenta
Where is the hypothalamus?
Located in the brain
Where is the pituitary? Describe it.
Located in the brain, composed of the anterior and posterior parts.
Describe the anterior pituitary (structure and function)
Includes the large pars distalis, the pars tuberalis, and the pars intermedia. It produces four tropic hormones that control other endocrine glands, as well as several other peptide hormones.
How does the anterior pituitary release hormones?
The hypothalamus produces releasing hormones (RHs) and inhibiting hormones (IHs), which are delivered to cells in the anterior pituitary by blood flowing through portal blood vessels in the pituitary stalk.
Describe the posterior pituitary (structure)
Includes the infundibular stalk and the pars nervosa.
How does the posterior pituitary release hormones?
Neurosecretory products of oxytocin- and vasopressin-synthesizing neurons are stored in axon terminals of the posterior pituitary, where they are released into the circulation upon neural stimulation.
Describe the function of the pineal gland.
It secretes melatonin during the dark phase of the light/dark cycle (circadian rhythm).
What does the photoneuroendocrine system do?
It integrates environmental cues with intrinsic circadian oscillators and consists of the pineal gland and the suprachiasmatic nucleus of the hypothalamus.
What are the gonadal hormones (there are seven)?
estrogen, progesterone, testosterone, relaxin, activin, inhibin, follistatin
What are the placental hormones (there are five)?
Human chorionic gonadotropin (hCG), equine chorionic gonadotropin (eCG/PMSG), estrogen, progesterone, placental lactogen
What is a hormone?
A chemical messenger synthesized and secreted by an endocrine gland, which circulates in body fluids and produces specific effects on the target tissue.
What are the functions of hormones?
Reproduction and sexual differentiation, development and growth, maintenance of the internal environment (homeostasis), and regulation of metabolism and nutrient supply.
What are the different ways hormones can be classified?
Source of production, biochemical structure, or mode of action
What are the seven different classes of hormones according to biochemical structure?
Peptides, polypeptides, proteins, glycoproteins, steroids, amines, and fatty acids.
Where are peptides synthesized/processed/released?
Synthesized as preprohormones in the ribosomes, processed to prohormones in the ER. Then packaged into vesicles in the Golgi. The vesicles are released from the cell in response to an influx of Ca2+.
What is the process of steroid hormone synthesis?
The StAR and TSPO transport cholesterol from the outer mitochondrial membrane (OMM) to the inner mitochondrial membrane (IMM), where cytochrome P450’s cholesterol side chain cleavage enzyme (P450scc) transforms cholesterol into pregnenolone, which will go to the smooth ER and be converted to progesterone or testosterone.
Describe prostaglandins and how they are synthesized.
Phospholipidases liberate arachidonic acid from membrane phospholipids. Arachidonic acid is then converted into prostaglandin H2 (PGH2) by cyclooxygenase. Other enzymes then create other forms of prostaglandin, which regulate several physiological functions such as contraction of smooth muscles in the reproductive tract, erection, ejaculation, sperm transport, ovulation, luteolysis, parturition, and milk ejection.
Where are peptides, proteins, and monoamines stored? What triggers their release?
They’re stored in secretory granules in endocrine cells. Signaling events triggered by exogenous regulators (termed secretagogues) causes their release.
