Endocrine System
Gluccocorticoid secretion is regulated by a negative feedback system. what happens?
-A fall in glucocorticoid levels in the blood causes hypothalamic neurosecretory cells to secrete corticotropin-releasing hormone (CRH) into the hypophyseal bloodstream. -CRH targets corticotroph cells in the anterior pituitary gland, stimulating the release of adrenocorticotrophin hormone (ACTH) into the blood. -ACTH circulates in the blood and stimulates cells of the zona fasciculata to synthesize and secrete glucocorticoids.
Insulin lowers blood glucose level by:
-Accelerating glucose uptake into cells. -Accelerating the conversion of glucose into glycogen by hepatocytes (glycogenesis). Increasing amino acid uptake and protein synthesis. -Accelerating fatty acid synthesis (lipogenesis). -Slowing the conversion of glycogen into glucose by hepatocytes (glycogenolysis). Slowing the conversion of lactic acid and amino acids into glucose (gluconeogenolysis).
Glucagon raises blood glucose level by:
-Accelerating the conversion of glycogen into glucose by hepatocytes (glycogenolysis). -Accelerating the conversion of lactic acid and amino acids into glucose (gluconeogenesis). -Stimulating hepatocytes to release glucose into the blood.
Activin
-Activin is a protein hormone that acts as the functional antagonist of inhibin. -It stimulates FSH release from the anterior pituitary, promoting follicular development
Activin
-Activin is a protein hormone that acts as the functional antagonist of inhibin. -It stimulates FSH release from the anterior pituitary, promoting spermatogenesis
Corpus luteum
-An ovarian follicle develops into a corpus luteum once it has released a secondary oocyte during ovulation. The corpus luteum acts as a temporary endocrine gland. -Synthesizes and secretes estrogens, progesterone, relaxin, and inhibin.
Transport proteins
-As previously mentioned, lipid-soluble hormones circulate in the blood bound to transport proteins. Transport proteins increase the solubility of lipid-soluble hormones in the blood, enabling them to be transported around the body. Molecules of lipid-soluble hormones are released from transport proteins near to their target cells, allowing them to diffuse out of capillaries and bind to specific receptors in order to exert their effects.
how do the adrenal glands help Resistance to stress
-By increasing levels of circulating glucose, glucocorticoids provide tissues with a ready supply of ATP, which enables them to overcome the stress of extreme conditions such as inhospitable temperatures, high altitude, fright, exercise, fasting, surgery, trauma, infection, and disease. -Glucocorticoids also indirectly elevate blood pressure by enhancing the vasoconstrictive effects of the hormone epinephrine; an effect essential for counteracting a fall in blood pressure due to blood loss. Maintenance of blood pressure is essential in ensuring nutrients are distributed rapidly to active cells
Antidiuretic hormone (ADH)/vasopressin principle actions?
-Causes the kidneys to reabsorb more water and return it to the blood, which increases blood volume and decreases the volume of urine expelled from the body. Therefore, ADH controls the body's water balance, preventing dehydration or water overload. -Alcohol inhibits ADH secretion, which is why frequent and excessive urination is a common effect of alcohol consumption. -ADH also decreases water loss through sweating and triggers vasoconstriction, which increases blood pressure.
Corticotrophs
-Corticotrophs synthesize and secrete: -Adrenocorticotropin hormone (ACTH): Targets the suprarenal cortex and stimulates the secretion of glucocorticoid hormones. -Melanocyte-stimulating hormone (MSH): The exact role of melanocyte-stimulating hormone (MSH) in humans is unknown, however it is thought that it may influence brain activity. An excess of MSH has been known to cause darkening of the skin.
Releasing hormones include which 5 hormones?
-Corticotropin-releasing hormone (CRH): Stimulates adrenocorticotropic hormone secretion from corticotrophs. -Growth hormone-releasing hormone (GHRH): Stimulates human hGH secretion from somatotrophs. -Prolactin-releasing hormone (PRH): Stimulates prolactin secretion from lactotrophs. -Thyrotropin-releasing hormone (TRH): Stimulates TSH secretion from thyrotrophs. -Gonadotropin-releasing hormone (GnRH): Stimulates the secretion of LH and FSH from gonadotrophs.
Oxytocin (OT)'s principle actions are?
-During labor, oxytocin stimulates and enhances the contraction of uterine smooth muscle cells until the baby is outside the birth canal. -After birth, circulating oxytocin stimulates milk ejection in women that are actively producing milk in response to prolactin; this is known as the letdown reflex. Oxytocin is also released in response to the mechanical stimulation of an infant suckling, and targets myoepithelial cells surrounding milk producing glands, again stimulating milk ejection, in a process known as the suckling reflex. -In males and non-pregnant, non-lactating females, it is thought that oxytocin may be involved in the development and maintenance of nurturing and affectionate behavior, and the feeling of sexual arousal and satisfaction brought about by sexual intercourse and orgasm.
Capsule
-Each suprarenal gland is enclosed by a thick capsule, comprising collagen fibers and a rich blood supply. -Each capsule provides a protective layer, as well as providing a good blood supply to the rest of the gland.
Endocrine glands
-Endocrine glands are ductless, they are made up of hollow spherical follicles lined with secretory epithelial cells. Each follicle is surrounded by an extensive capillary network -They produce hormones which are secreted into interstitial fluid and diffuse into the surrounding capillaries. These hormones are transported in the blood to their target organ, tissue, or cells located elsewhere in the body. -Pituitary gland, pineal gland, thyroid, parathyroid, and adrenal glands.
Exocrine glands
-Exocrine glands consist of a glandular portion, lined with secretory epithelial cells and a duct portion, lined with simple cuboidal or columnar epithelial cells. -They secrete their non-hormone products via ducts to a target organ, body cavity, or tissue surface. -ex) Sweat glands, mucous glands, digestive glands, and sebaceous or oil glands.
Gonadotrophs
-Follicle-stimulating hormone (FSH) : Targets the gonads. In the ovaries, follicle stimulating hormone (FSH) initiates the monthly development of ovarian follicles and stimulates the secretion of estrogens from follicular cells.In the testes, FSH promotes sperm production and stimulates development of the seminiferous tubules. -Luteinizing hormone (LH): In the ovaries, luteinizing hormone (LH) triggers ovulation, the monthly release of a secondary oocyte from an ovary. After ovulation, LH stimulates formation of the corpus luteum in the ovary and triggers it to secrete progesterone, preparing the breasts for milk production. In the testes, LH stimulates the secretion of testosterone.
Germ cells
-Germ cells, known as spermatogonia, are the immature, undifferentiated cells that give rise to gametes. They congregate along the walls of the seminiferous tubules. -Germ cells produce sperm cells through proliferation (cell division) and differentiation, in a process known as spermatogenesis.
Glucagon
-Glucagon is a very potent polypeptide hormone synthesized and secreted by alpha cells of the islets of Langerhans. It is secreted in response to a fall in blood sugar levels, or a rise in amino acids in the blood, and targets hepatocytes (liver cells).
Glucocorticoids
-Glucocorticoids are steroid hormones, secreted by cells of the zona fasciculata. Glucocorticoids circulate in the blood, targeting almost all body tissues and ultimately raising blood glucose levels. -They control carbohydrate metabolism, thus increasing blood sugar. -Cortisol, corticosterone, and cortisone are examples
how is Metabolism controlled by the adrenal glands
-Glucocorticoids target liver cells, stimulating gluconeogenesis, the conversion of amino acids or lactic acid (or any non-monosaccharide substrate) to glucose. Circulating glucose may then be used for ATP production. -Glucocorticoids target tissues such as muscle, stimulating the breakdown of proteins into free amino acids, thus increasing levels of amino acids in the blood. Circulating amino acids may then be used for ATP production, as building blocks for repair of damaged tissue, or for the synthesis of new enzymes to be used in metabolic processes. -Glucocorticoids target adipose tissue, stimulating lipolysis, the breakdown of triglycerides into glycerol and fatty acids. The increased circulating levels of fatty acids are used for energy production and glycerol may be used as a substrate for gluconeogenesis. -Glucocorticoids conserve glucose by inhibiting its uptake in muscle and adipose tissue, thus increasing levels of glucose in the blood.
Gonadotropin-releasing hormone (GnRH)
-Gonadotropin-releasing hormone (GnRH), released by the hypothalamus, stimulates LH and FSH secretion from the anterior pituitary gland. -GnRH release is inhibited by estrogens during childhood.
Ghrelin
-Grehlin is a peptide hormone synthesized and secreted by the epsilon cells of the pancreas and the cells lining the fundus of the stomach. - Targets the brain -stimulated hungar
Somatotrophs
-Growth hormone (hGH): Targets the liver, skeletal muscle, cartilage, bone, and other body tissues. Human growth hormone (hGH), also known as somatotrophin, stimulates the secretion of insulin-like growth factors (IGFs), or somatomedins, ultimately regulating protein, lipid, and carbohydrate metabolism, and stimulating growth and repair of body tissues and cellular reproduction.
Inhibiting hormones
-Growth hormone-inhibiting hormone (GHIH): Inhibits secretion of hGH from somatotrophs -Prolactin-inhibiting hormone (PIH): Inhibits secretion of prolactin from lactotrophs.
how does the adrenal gland provide Anti-inflammatory actions
-High levels of glucocorticoids cause inhibition of the white blood cells involved in inflammatory responses. -High levels of glucocorticoids suppress cartilage and bone formation and therefore suppress tissue repair, leading to insufficient wound healing. -High levels of glucocorticoids cause immune responses to be suppressed.
Humoral stimuli
-In some cases, changes in the chemical composition of the blood may trigger endocrine glands to secrete their hormones. -The cells of some endocrine glands simply monitor the concentration of certain elements within the blood and release their hormones in response to a particular change in concentration. -Examples: Parathyroid glands secrete parathyroid hormone in response to a decrease in calcium concentration in the blood. -Secretion of insulin from the pancreas.
Neural stimuli
-In some cases, nerve fibers stimulate endocrine glands to secrete their hormones. -Examples:Stress activates the sympathetic nervous system, causing it to send neural signals to the adrenal medulla, stimulating the release of epinephrine and norepinephrine. -Nerve impulses from the hypothalamus stimulate the release of oxytocin and antidiuretic hormone (ADH).
Inhibin
-Inhibin is a protein hormone synthesized and secreted by Sertoli cells when sperm count is high. -It exerts negative feedback, inhibiting FSH release from the anterior pituitary and inhibiting GnRH release from the hypothalamus
Inhibin
-Inhibin is a protein hormone synthesized and secreted by granulosa cells with a small rise in FSH and estrogen levels. It is also secreted by the corpus luteum after ovulation. -Inhibin exerts negative feedback, inhibiting FSH release from the anterior pituitary and GnRH release from the hypothalamus.
Androgens
-Male sex hormones (androgens) and female sex hormones (estrogens) are secreted in small amounts in both sexes by cells of the zona reticularis of the suprarenal cortex. Hormones from the testes and ovaries usually mask their effect. -Dehydroepiandrosterone (DHEA) is an example
Hormonal stimuli
-Often, endocrine glands will secrete their hormones in response to regulatory hormones released from other endocrine glands. -Hormone release is controlled by a feedback loop; as the blood concentration of hormones secreted from target endocrine glands increases, the release of regulatory hormones is inhibited. -Examples: Thyroid-stimulating hormone released from the hypothalamus travels down the infundibulum (pituitary stalk) in the portal circulation and stimulates the release of thyroxine from the anterior pituitary gland. As the blood concentration of thyroxine increases, secretion of thyroid-stimulating hormone is inhibited.
How does the posterior pituitary gland control the release of antidiuretic hormone
-Osmoreceptors in the macula densa of the kidneys detect changes in solute and water concentrations in the blood and if solutes become too concentrated (blood water content is too low), they depolarize, transmitting excitatory impulses to neurons in the SON of the hypothalamus, which synthesize and release ADH. -ADH is released into the portal blood in the posterior pituitary gland and is transported in the blood to the kidneys, where it targets kidney tubule cells. As a result, kidney tubule cells reabsorb more water, thus increasing blood volume and decreasing the volume of urine produced and expelled from the body. -As solute concentrations return to an ideal normal value, osmoreceptors stop depolarizing and ADH release is suppressed.
Oxyphil cells
-Oxyphil cells are larger and paler than chief cells and are found in clusters at the center and periphery of each parathyroid gland. -The function of oxyphil cells is unknown
Principal actions of progesterone
-Progesterone also stimulates growth of the uterus lining, preparing for the arrival of a developing embryo in case of fertilization. -Progesterone also stimulates growth of the mammary glands and stops uterine contractions.
Lactotrophs
-Prolactin (PRL): Targets the mammary glands (breasts). Prolactin is only present in females, stimulating and maintaining milk production and secretion. Mammary glands must first be primed by estrogens, progesterone, glucocorticoids, human growth hormone, thyroxine, and insulin before prolactin can have an effect.
Principal actions of relaxin
-Relaxin is a peptide hormone secreted by the corpus luteum of the ovary. -The level of relaxin rises for about 14 days after ovulation and then declines when fertilization doesn't occur, triggering menstruation. -During pregnancy, relaxin is released from the placenta. It increases the flexibility of the pubic symphysis, and promotes dilation of the uterine cervix during labor and as the newborn passes through the birth canal.
Renin
-Renin, also known as angiotensinogenase, is an enzyme and peptide hormone synthesized and secreted by specialized granulosa cells of the juxtaglomerular apparatus in the kidneys. It is secreted in response to decreased arterial blood pressure, decreased chloride levels in the urine, and sympathetic stimulation. - targets the bloodstream and ultimately the kidneys -Targets angiotensinogen, which causes vasodilation of arterioles and the suprarenal cortex to produce aldosterone
The pancreas has two important functions:
-Specialized cells in the pancreas produce the hormones glucagon and insulin. These hormones control blood sugar levels by initiating the conversion of glycogen to glucose and vice versa. -The pancreas also has a function in digestion, producing an enzyme-rich pancreatic juice which helps break down proteins to amino acids, starch to maltose, and fats into fatty acids and glycerol.
Hypocalcemia
-Stimulus: Decreased blood Ca2+ levels -Receptor: Chief cells of the parathyroid gland detect decreased Ca2+ levels Control center Chief cells secrete increased quantities of parathyroid hormone (PTH) into the blood -Effectors 1. PTH stimulates an increase in osteoclastic activity in bone releasing Ca2+ into the blood 2. The level of Ca2+ reabsorption in the kidney increases
Hypercalcemia
-Stimulus: Increased blood Ca2+ levels -Receptor: Parafollicular cells of the thyroid gland detect increased Ca2+ levels Control center Parafollicular cells secrete increased quantities of calcitonin into the blood -Effectors 1. Calcitonin stimulates an increase in number and activity of osteoblast cells in bone preventing calcium release into the blood 2. The level of Ca2+ reabsorption in the kidney decreases
Principal actions of testosterone?
-Testosterone is responsible for the development of the secondary sexual characteristics during puberty, such as the deepening of the voice, growth of facial hair, and muscle development. -It stimulates and maintains maturation of the male reproductive organs and secretory glands, and stimulates the production and development of sperm -It has metabolic effects, stimulating protein synthesis and muscle growth, and is associated with the development of aggressive behavior.
Zona fasciculata
-The zona fasciculata is the middle and the widest of the three zones. It consists of large secretory cells -Cells of the zona fasciculata synthesize and secrete glucocorticoid hormones, which play a role in regulating glucose homeostasis.
Zona glomerulosa
-The zona glomerolosa is the outermost zone, lying beneath the connective tissue capsule. It is tightly packed with small secretory cells, arranged in spherical clusters. Its cells are basophilic and have well-established smooth endoplasmic reticulum for synthesizing steroids. -Cells of the zona glomerulosa synthesize and secrete mineralocorticoid hormones, which help regulate mineral homeostasis.
Zona reticularis
-The zona reticularis is the innermost zone, with rounded secretory cells arranged in branching, anastamosing cords or columns. -Cells of the zona reticularis synthesize and secrete small amounts of weak androgens, which have masculinizing effects.
Thyrotrophs
-Thyrotrophs synthesize and secrete: Thyroid-stimulating hormone (TSH): Targets the thyroid gland and controls the synthesis and secretion of the thyroid hormones triiodothyronine (T3) and thyroxine (T4).
The fight-or-flight response includes the following: (6)
-dilation of airways. -conversion of glycogen into glucose (in the liver). -increased heart rate and strength of contraction, dilation of the blood vessels of the heart, lungs, brain, and skeletal tissues. This increases offloading of glucose and oxygen to organs most active in overcoming the stressor, including the heart, lungs, brain, and skeletal muscles. constriction of blood vessels of most -viscera and skin, causing suppression or cessation of non-essential body functions, including digestive, urinary, and reproductive activities. -reduction of blood flow to the kidneys, promoting the release of renin and thus activating the renin-angiotensin-aldosterone system. This ultimately leads to water retention and elevated blood pressure. -sweating.
Human chorionic gonadotropin (hCG))
-hCG is a glycoprotein hormone synthesized and secreted by fetal trophoblast cells of the placental syncytiotrophoblast. -Targets the Corpus luteum of the ovaries (blocks LH receptors). -Prevents disintegration of the corpus luteum and therefore maintains the production of estrogen and progesterone for pregnancy
The paraventricular nucleus (PVN) is
-is a collection of neurosecretory cell bodies -The lateral region of the PVN contains the cell bodies of specialized neurosecretory cells, known as magnocellular neurons, that project down to the posterior pituitary. - The medial region of the PVN contains the cell bodies of specialized neurosecretory cells, known as parvocellular neurons, that project down to the median eminence of the hypothalamus and the infundibulum of the pituitary gland.
Triiodothyronine (T3) is
-synthesized and secreted by thyroid follicular cells, but is also synthesized from T4 in various target tissues. -Triiodothyronine, the more potent thyroid hormone, consists of two linked tyrosine amino acids and three bound iodine atoms. -Works similarly to thyroxine, but its effects are not as immediate.
Thyroxine (T4) is
-the principal hormone synthesized and secreted by thyroid follicular cells. -Thyroxine consists of two linked tyrosine amino acids and four bound iodine atoms and therefore follicular cells require iodine and tyrosine for its production.
The sequence of events can be summarized in the following 5 points:
1. A water soluble hormone binds to a cell surface receptor, forming a hormone-receptor complex. 2. The hormone-receptor complex activates a G protein associated with the cell surface receptor. 3. The G protein stimulates the activity of the membrane bound enzyme adenylate cyclase, which converts ATP into cAMP. 4. cAMP activates protein kinases, which use phosphate groups from ATP to phosphorylate other proteins within the cell, activating them. 5. The activated phosphorylated proteins mediate a wide range of reactions within the target cell, producing the physiological responses associated with the stimulating hormone.
The following 14 steps describe the synthesis, secretion, and transport of thyroid hormones T3 and T4:
1. Iodide trapping, 2. Oxidation to iodine, 3. TGB synthesis and storage, 4. TGB packed into vesicles, 5. Sugar residues added to TGB in the Golgi complex, 6. TGB packed into secretory vesicles, 7. Vesicles undergo exocytosis, 8. TGB stored in the colloid, 9. Iodination of tyrosine, 10. Coupling of T1 and T2, 11. TGB colloid pinocytosis, 12. Cleavage of T3 and T4, 13. Secretion of T3 and T4, 14. Transport of T3 and T4 in the blood
HOMEOSTASIS OF THE STRESS RESPONSE: Receptor
1. Physical stressors may activate specific receptors. For example, significant blood loss would activate baroreceptors in the aortic arch and carotid sinuses. 2. Psychological stressors do not necessarily activate classical sensory receptors. Instead, activity in the neurocircuitry responsible for the perception and interpretation of these stressors will input either directly or indirectly into the hypothalamus. The perception of anxiety for example, is associated with the amygdala and hippocampus. Both these regions provide numerous inputs into the region of the hypothalamus related to the stress response.
The pancreas is a
12-15 cm long, leaf-shaped organ that lies horizontally, deep to the stomach, and is covered in front by peritoneum.The pancreas is a yellow, lobular gland that lies in the curve of the duodenum and stretches to the left horizontally as far as the spleen.
Hormones produced by the gonads have a number of important functions: 3
1: The regulation of the menstrual cycle and stimulation of the production of oocytes in females. 2: The maintainance of pregnancy in females. 3: The promotion of puberty and the development of secondary sex characteristics in males and females.
The suprarenal glands have a number of important functions: (4)
1:The regulation of mineral homeostasis. 2: The regulation of glucose homeostasis. 3: The promotion of puberty. 4: The triggering of the 'fight-or-flight' response.
Parathyroid capsule
A capsule surrounds the outside of parathyroid tissue, defining each parathyroid gland and differentiating it from surrounding thyroid tissue
Thyroid capsule
A capsule surrounds the outside of thyroid tissue, defining the thyroid gland, and differentiating it from parathyroid tissue.
Basement membrane
A thin basement membrane surrounds each follicle, supporting the outside of each follicular cell and holding it in place.
The activated protein kinases catalyze the conversion of
ATP to adenosine diphosphate, known as ADP, during which the ATP donates a phosphate group to an inactive cellular protein.
___accounts for about a third of parathyroid tissue mass.
Adipose tissue
Skin
Along with its function as a protective cushion and an insulator, supporting the external surface of the body and underlying structures, the skin has sensory and endocrine roles.
Secondary plexus i drained by?
Anterior hypophyseal veins that eventually drain into the cavernous sinus below.
The effects of the thyroid hormones T3 and T4 are widespread; they exert their effects by binding to specific receptors exhibited by most cells throughout the body. what are five main effects?
Basal metabolic rate (BMR), Synthesis of sodium-potassium pumps, Maintenance of normal body temperature, Up regulation of beta receptors, Acceleration of body growth
Corticotropin-releasing hormone (CRH)
CRH stimulates the release of adrenocorticotrophic hormone (ACTH) from the anterior pituitary gland. ACTH travels in the bloodstream to target cells in the adrenal (suprarenal) cortex, where it stimulates the release of cortisol.
Calcitriol
Calcitriol is the active form of vitamin D, synthesized and secreted by cells of the proximal tubule of the nephron in the kidneys. - targets the intestines -Absorption of calcium and phosphorus from digested food.
The suprarenal cortex consists of three zones, each anatomically and functionally distinct:
Capsule, Zona glomerulosa, Zona fasciculata, Zona reticularis
Chief cells
Chief cells are the principal cells of the parathyroid glands. They are smaller and more numerous than oxyphil cells and are found throughout parathyroid tissue. -Chief cells work independently of oxyphil cells and go through cycles of activity and inactivity depending on blood calcium levels. When active, their Golgi complexes increase in size and they gain numerous secretory granules -Chief cells synthesize and secrete parathyroid hormone.
Chromaffin cells
Chromaffin cells are large basophilic secretory cells with secretory granules contained within their cytoplasm. Preganglionic sympathetic neurons synapse onto the surface of chromaffin cells. -Chromaffin cells function similarly to postganglionic sympathetic neurons, synthesizing, storing, and releasing the catecholamines noradrenaline (also known as norepinephrine) and adrenaline (also known as epinephrine) into the blood.
Antidiuretic hormone (ADH)/vasopressin's target organ is?
Collecting ducts in the kidneys to retain water and smooth muscle in blood vessels to cause mild vasoconstriction.
Resistance reaction (endocrine response) is initiated by what three hormones?
Corticotropin-releasing hormone (CRH), Growth-hormone-releasing hormone (GHRH), Thyrotropin-releasing hormone (TRH)
Resistance reaction (endocrine response) Stress responses for cortisol
Cortisol stimulates lipolysis (the breakdown of triglycerides into fatty acids), gluconeogenesis (the generation of glucose from non-carbohydrate substrates), and protein catabolism (from amino acids). Free circulating fatty acids, glucose, and amino acids are then used to produce ATP for energy, or for the repair of damaged cells. Cortisol also causes the sensitization of blood vessels and the suppression of inflammation.
Epidermal growth factor (EGF)
EGF is produced and secreted by cells of submaxillary salivary glands. It stimulates proliferation and differentiation of a variety of cells including neurons, astrocytes, fibroblasts, and epithelial cells, and inhibits gastric acid secretion and the activity of some cancer cells.
Erythropoietin (EPO)
EPO, also known as hematopoietin, is a glycoprotein hormone synthesized and secreted by endothelial cells of the peritubular capillaries of the kidneys and liver. - targets red bone marrow -Triggers an increase in red blood cell production.
what does Eicosanoids target?
Eicosanoids target various body cells, binding plasma membrane receptors, and stimulating or inhibiting the synthesis of associated second messengers, one example being cyclic AMP
The actions of hormones are classified according to how far they travel from their site of secretion and the target cells they act upon:
Endocrine actions, Paracrine actions, and Autocrine actions
Neurosecretory fiber terminals
Enlarged terminal endings of about 50,000-100,000 unmyelinated neurosecretory axons, arising from the SON and the PVN of the hypothalamus, synapse on sinusoidal capillaries in the posterior pituitary. Neurosecretory fiber terminals are filled with numerous membrane-bound neurosecretory granules containing either antidiuretic hormone (ADH), also known as vasopressin, or oxytocin.
10. Coupling of T1 and T2
Enzymes within the colloid mediate the linking of T1 and T2. The joining of two molecules of T2 forms T4 and the joining of one molecule of T2 and one molecule of T1 forms T3.
What are six different types of growth factors?
Epidermal growth factor (EGF), Platelet-derived growth factor (PDGF), Fibroblast growth factor (FGF), Nerve growth factor (NGF), Tumor angiogenesis factors (TAFs), Transforming growth factors (TGFs)
Estrogens and progesterone
Estrogen is synthesized by the follicles; estrogen and progesterone are synthesized by the corpus luteum.
Estrogens
Estrogens are steroid hormones synthesized and secreted by the placental syncytiotrophoblast. Secretion of estrogens increases towards the end of gestation. - targets Uterus and Mammary glands. -Uterus: stimulate growth of the myometrium and antagonize the suppressive activity of progesterone, ultimately preparing the uterus for childbirth. -Mammary glands: stimulate ductal and alveolar growth in preparation for milk secretion. -Estrogens also inhibit LH and FSH secretion from the anterior pituitary.
Principal actions of estrogens
Estrogens stimulate growth of the uterus lining during ovulation and menstruation. -Estrogens are responsible for the development of secondary sexual characteristics during puberty, such as the development of the mammary glands (breasts), broadening of the pelvis, and maturation of the female reproductive organs.
Fibroblast growth factor (FGF)
FGF is found in the brain and pituitary gland and has multiple effects on multiple cell types. It stimulates the proliferation and differentiation of many cells including fibroblasts, smooth muscle cells, chondrocytes, adrenocortical cells, and endothelial cells. Proliferation and differentiation of endothelial cells ultimately leads to angiogenesis, the formation of new blood vessels.
Follicle-stimulating hormone
Follicle-stimulating hormone (FSH), released by the anterior pituitary gland, indirectly stimulates the development of sperm (spermatogenesis) by priming cells for the actions of testosterone.
Follicle-stimulating hormone
Follicle-stimulating hormone (FSH), released by the anterior pituitary gland, promotes follicle growth and maturation, and stimulates follicle cells to secrete estrogen.
Follicular cells
Follicular cells are epithelial cells with microvilli on their luminal surface. Inactive follicular cells vary in shape from cuboidal to squamous, but once actively secreting, they take on a taller, more columnar shape. -Synthesize and secrete thyroid hormones T3 and T4.
___ glands are embedded in the posterior surface of the thyroid gland.
Four parathyroid
Growth-hormone-releasing hormone (GHRH)
GHRH stimulates the release of human growth hormone (hGH) from the anterior pituitary gland, which in turn stimulates the secretion of insulin-like growth factors (IGFs) by the liver.
Gonadotropin-releasing hormone (GnRH)
Gonadotropin-releasing hormone (GnRH), released by the hypothalamus, stimulates LH and FSH secretion from the anterior pituitary gland. -GnRH release is inhibited by testosterone.
what are the three types of ovarian follicles layers?
Granulosa cells, Thecal cells, Corpus luteum
CONTROL OF HORMONE SECRETION
Hormones are secreted from endocrine glands upon stimulation. Secretion occurs in frequent bursts, increasing the amount of hormone circulating in the blood. It is important that hormone secretion is regulated in order to prevent over or under secretion, thus maintaining homeostasis.
Amine hormones
Hormones classed as amines are simply modified amino acids. examples include: Epinephrine, Norepinephrine, Dopamine, Histamine, Serotonin
Eicosanoid hormones
Hormones classed as eicosanoids are active lipids released from cell membranes that act as local chemical signals, affecting only nearby cells. They act upon multiple target cells and trigger responses such as raising blood pressure, increasing uterine contractions, stimulating blood clotting, mediating pain and inflammation, and allergic reactions. two examples: Prostaglandins, Leukotrienes
Peptide hormones
Hormones classed as peptides are constructed from short chains of amino acids. examples include: Antidiuretic hormone (ADH), Oxytocin, Human growth hormone, Insulin
Steroid hormones
Hormones classed as steroid hormones are derived from cholesterol and include gonadal and adrenocortical hormones.
Thyroid hormones
Hormones classed as thyroid hormones are derived from iodine and the amino acid tyrosine. They are synthesized in the thyroid gland.
Paracrine actions
Hormones that act locally by diffusing from their source into a neighboring target cell are said to have paracrine actions.
Autocrine actions
Hormones that act on the same cell that produced them are said to have an autocrine action.
Endocrine actions
Hormones that are distributed in the blood and bind to a target cell elsewhere are said to have endocrine actions.
EXHAUSTION
If the resistance reaction fails to combat the stressor, the body eventually becomes depleted of all resources and is forced into a state of exhaustion.
Granulosa cells
In a primordial follicle (immature ovarian follicle), a single layer of follicular cells exists surrounding the primary oocyte (immature egg). In a late primary follicle (ovarian follicle in early development), these cells undergo cell division and develop into several layers of granulosa cells. -Synthesize and secrete estrogens and inhibin
11. TGB colloid pinocytosis
In the presence of TSH, inactive follicular cells become active secretory units, ingesting droplets of colloid from the follicle lumen by pinocytosis. -Once inside the cell, the iodine-bound and linked tyrosines, still part of the thyroglobulin colloid, merge with lysosomes.
Thyroxine (T4) principle actions?
Increases oxygen consumption and body metabolism; increases heart rate and blood pressure; increases sensitivity to sympathetic stimulation; stimulates RBC development; increases protein and lipid catabolism and glucose uptake; essential for skeletal, muscle and nervous development. It has immediate effects.
Epinephrine and norepinephrine are powerful vasopressors, meaning they increase blood pressure. They do this by:
Increasing contractility of cardiac muscle, Increasing heart rate, Triggering vasoconstriction
The posterior plexus supplied?
Inferior hypophyseal arteries that divide into medial and lateral branches and anastamose across the midline, forming an arterial ring wrapping around the infundibulum. The inferior hypophyseal arteries branch from the cavernous part of the internal carotid artery (the meningohypophyseal trunk).
Epinephrine and norepinephrine increase blood glucose and circulating fatty acids for use in energy production by:
Inhibiting insulin secretion and stimulating glucagon secretion from the pancreas Stimulating glycogenolysis in the liver and muscle Stimulating glycolysis in muscle Stimulating ACTH secretion from the pituitary gland Stimulating lipolysis in adipose tissue
Insulin
Insulin is a peptide hormone composed of two chains of amino acids. It is synthesized and secreted by beta cells of the islets of Langerhans and targets most cells in the body, but has a key influence on hepatocytes, adipocytes, and myocytes.
Resistance reaction (endocrine response) Stress responses for insulin-like growth factors
Insulin-like growth factors stimulate lipolysis and glycogenolysis (the breakdown of glycogen into glucose).
2. Oxidation to iodine
Iodide ions are negatively charged and cannot bind to the tyrosines constituting thyroglobulin (TGB) until they undergo oxidation. -During oxidation, the removal of electrons changes iodide (I-) into the more readily binding iodine (I2). As oxidation occurs, iodine molecules pass through the membrane into the lumen of the thyroid follicle.
Leukotrienes (LTs)
LTs mediate inflammation by stimulating the attraction of white blood cells to a chemical stimulus, also known as chemotaxis.
Leptin
Leptin is a peptide hormone synthesized and secreted by adipocytes of mainly white adipose tissue. - targets the Hypothalamus of the brain. -Suppresses appetite, reduces body weight, and stimulates energy expenditure. It is also thought to increase the activity of the hormones FSH and LH.
What are three types of eicosanoids?
Leukotrienes (LTs), Prostaglandins (PGs), Thromboxane (TX)
Leydig cells
Leydig cells, also known as interstitial cells, reside within the interstitial fluid filled spaces between the seminiferous tubules. -Leydig cells synthesize and secrete androgens, and, most importantly, testosterone.
what is unique about lipid soluble hormones?
Lipid-soluble hormone molecules bound to transport proteins cannot pass through the filtering system in the kidneys and therefore, are not so freely lost in the urine.
LIPID-SOLUBLE HORMONES
Lipid-soluble hormones are able to diffuse through the lipid bilayer of the plasma membrane of a cell, in order to exert their effect by binding to intracellular receptors in the cytosol or nucleus. Due to their insolubility in water, they must bind to transport proteins in order to circulate in the blood. Lipid-soluble hormones include steroid and thyroid hormones and gaseous hormones such as nitric oxide.
Secondary plexus is supplied by the?
Long hypophyseal portal veins arising from the primary plexus above.
Primary plexus is drained by?
Long hypophyseal portal veins that pass down the outside of the infundibulum, connecting the primary plexus to a secondary plexus.
Luteinizing hormone
Luteinizing hormone (LH), also known as interstitial cell-stimulating hormone, released by the anterior pituitary gland, stimulates Leydig cells to secrete testosterone.
Luteinizing hormone
Luteinizing hormone (LH), released by the anterior pituitary gland, promotes follicle growth and maturation. A surge in LH triggers ovulation and the formation of a corpus luteum.
Control of relaxin is control by 5 hormones.
Luteinizing hormone, Follicle-stimulating hormone, Gonadotropin-releasing hormone (GnRH), Inhibin, Activin
Control of testosterone is done with 5 different mechanisms what are they?
Luteinizing hormone, Follicle-stimulating hormone, Gonadotropin-releasing hormone (GnRH), Inhibin, Activin
12. Cleavage of T3 and T4
Lysosomal enzymes break down the thyroglobulin colloid, cleaving off free T3 and T4.
The paraventricular nucleus (PVN) function?
Magnocellular neurons of the PVN synthesize oxytocin and anti-diuretic hormone (ADH) that are secreted from axon terminals in the posterior pituitary, while parvocellular neurons synthesize releasing and inhibiting hormones that control the release of anterior pituitary hormones.
what is the function of the supraoptic nucleus?
Magnocellular neurons of the SON synthesize and secrete ADH. In response to a stimulus, they release ADH into their axons, which is ultimately secreted from axon terminals in the posterior pituitary.
Antidiuretic hormone (ADH)/vasopressin is secreted from:
Magnocellular neurons of the posterior pituitary (arising from the PVN and the SON).
Oxytocin (OT) is secreted from?
Magnocellular neurons of the posterior pituitary (arising from the PVN).
Mineralocorticoids
Mineralocorticoids are steroid hormones secreted by cells of the zona glomerulosa. Mineralocorticoids circulate in the blood, targeting the kidneys and ultimately increasing blood pressure and blood volume -They help to control blood volume and blood pressure by regulating the levels of reabsorbing sodium (Na+), secreting potassium (K+) and excreting hydrogen (H+) ions in urin that are in the blood. -Aldosterone is an example
Endocrine cells of the suprarenal glands synthesize and secrete four different classes of hormones, each with different actions
Mineralocorticoids, glucocorticoids, and androgens are secreted from the suprarenal cortex, while epinephrine and norepinephrine are secreted from the suprarenal medulla.
14. Transport of T3 and T4 in the blood
Most T3 and T4 are transported in the blood bound to the plasma protein thyroxine-binding globulin (TBG).
Nerve growth factor (NGF)
NGF is a small protein produced and secreted by cells of submaxillary salivary glands and the hippocampus of the brain. It causes embryonic axonal growth and is essential for the survival and maintenance of the sympathetic nervous system and sensory neurons.
Agonist hormones
Natural hormones are agonists. They bind freely to their receptors, forming a hormone-receptor complex, which in turn triggers a cascade of events to occur inside a target cell.
Platelet-derived growth factor (PDGF)
PDGF is produced by blood platelets. It stimulates proliferation and differentiation of a number of cells including fibroblasts, smooth muscle cells, and neuroglial cells. It promotes wound healing and has been linked to the development of atherosclerosis.
Prostaglandins (PGs)
PGs have various regulatory roles, including the alteration of: muscle contraction, blood flow, platelet functioning, glandular secretion, respiratory and reproductive processes, transmission of nerve impulses, lipid metabolism, and immune responses. Prostaglandins are also involved in enhancing inflammation, fever, and pain.
Intestines
PTH indirectly increases Ca2+ absorption in the intestines by increasing vitamin D activation in the kidneys. Vitamin D targets the intestines, enhancing their ability to absorb Ca2+.
PTH regulations on Bone
PTH targets osteoclasts, increasing their number and activity and therefore increasing their capacity for bone resorption. During bone resorption, Ca2+ and HPO42- ions are released into the blood.
Kidneys
PTH targets the kidneys, exerting three different effects: 1. Slows the rate of Ca2+ and Mg2+ loss in the urine: PTH slows the rate of Ca2+ and Mg2+ loss in the urine by enhancing their reabsorption by the kidneys, which increases the concentration of Ca2+ and Mg2+ ions in the blood. 2. Increases loss of HPO42- in the urine: PTH increases loss of HPO42- in the urine, which decreases the concentration of HPO42- in the blood. 3. Promotes synthesis of calcitriol: PTH promotes synthesis of calcitriol (the active form of vitamin D), which increases the absorption rate of Ca2+, Mg2+, and HPO42- from food in the gastrointestinal tract into the blood.
Pancreatic polypeptide
Pancreatic polypeptide is a polypeptide hormone synthesized and secreted by F cells of the islets of Langerhans. It targets D cells, pancreatic acinar cells, and smooth muscle cells of the gallbladder.
Some of the ways in which hormones interact are: (4)
Permissive hormones, Synergistic hormones, Agonist hormones, and Antagonist hormones
The posterior plexus drained by?
Posterior hypophyseal veins that eventually drain into the cavernous sinus below.
Progesterone
Progesterone is a steroid hormone synthesized and secreted by the placental syncytiotrophoblast -targets the Uterus and Mammary glands. -Uterus: supports the endometrium and suppresses contractility of uterine smooth muscle, for maintenance of pregnancy. -Mammary glands: inhibits lactation during pregnancy. -Progesterone also inhibits LH and FSH secretion from the anterior pituitary, which prevents ovulation from occurring during pregnancy.
HOMEOSTASIS OF THE STRESS RESPONSE: Effectors
Regions of the hypothalamus send out nerve impulses along the sympathetic division of the autonomic nervous system, leading to the release of fight-or-flight hormones from the adrenal gland. In addition, a range of hormones are released from the anterior pituitary gland.
PARATHYROID HORMONE (PTH)
Regulates the concentration and distribution of calcium (Ca2+), magnesium (Mg2+), and phosphate (HPO42-) ions in the body.
Relaxin
Relaxin is a peptide hormone also released by the corpus luteum. - targets Pubic symphysis and uterine cervix. -Increases the flexibility of the pubic symphysis and promotes dilation of the uterine cervix during labor and as the newborn passes through the birth canal.
Parafollicular cells
Secretory parafollicular cells, also known as C cells, are distributed sparsely among follicular cells and in the spaces between the follicles. They have a pale-staining cytoplasm. -Synthesize and secrete the peptide hormone calcitonin.
Sertoli cells function?
Sertoli cells provide structural support to developing sperm cells. They also form the blood-testis barrier, a diffusion barrier protecting developing sperm cells from harmful blood-borne substances. -They secrete a protein-rich fluid into the lumen of the seminiferous tubules, which provides developing sperm cells with nutrients and aids their transport through the seminiferous tubules
Each testis is divided up into a series of lobules, comprising tightly coiled seminiferous tubules. Three main types of cells comprise the testes:
Sertoli cells, Leydig cells, and germ cells
Sertoli cells
Sertoli cells, also known as sustentacular cells, are the supportive cells that form the walls of the seminiferous tubules. Their cytoplasmic projections, rich in lysosomes, project into the lumen of the seminiferous tubules, enveloping immature sperm cells. -They also secrete inhibin and activin, hormones that regulate FSH secretion.
____ spread throughout each parathyroid gland, meandering between secretory chief cells.
Sinusoid capillaries
Somatostatin
Somatostatin, also known as growth hormone-inhibiting hormone (GHIH), or somatotropin release-inhibiting factor (SRIF), is a peptide hormone synthesized and secreted by delta cells of the islets of Langerhans. It targets alpha cells, beta cells, and cells of the GI tract.
Antagonist hormones
Some circulating molecules act as antagonists against hormones; they bind hormone receptors, blocking agonist binding. As long as the antagonist is bound to the receptor, the hormone cannot form a hormone-receptor complex and thus cannot trigger signal transduction inside a target cell. Antagonists are often used as drugs to block the actions of specific hormones.
Permissive hormones
Some hormones are permissive; they act as a secondary hormone, promoting the effect of a primary hormone. A primary hormone sometimes requires simultaneous or recent exposure to a second hormone in order to be effective; a permissive (secondary) hormone acts as a primer, paving the way for a primary hormone. A permissive hormone may work by either stimulating the expression of receptors specific to the primary hormone, thus increasing hormone binding, or by promoting the synthesis of a specific enzyme needed for the primary hormone's intracellular cascade of reactions to occur.
Synergistic hormones
Some hormones are synergistic, whereby two hormones act together in order to create an effect greater than if one were to act alone.
HOMEOSTASIS OF THE STRESS RESPONSE: control center
Specialized regions of the hypothalamus receive the various inputs and co-ordinate an appropriate response.
Thecal cells
Stromal cells distributed around the outside of the ovarian follicle develop into thecal cells. -In a secondary follicle, the internal layer of thecal cells secretes estrogens.
5. Sugar residues added to TGB in the Golgi complex
Sugar residues are added to the molecules in the Golgi complex.
Primary plexus is supplied by?
Superior hypophyseal arteries that arise from the posterior communicating artery (a branch of the internal carotid artery).
Synthesis of Eicosanoids
Synthesis occurs by the oxidation of 20-carbon essential fatty acids, clipped from membrane phospholipid molecules. The precursor 20-carbon fatty acid is known as arachidonic acid, from which leukotrienes (LTs) and prostaglandins (PGs), both eicosanoids, are produced.
Maintenance of normal body temperature
T3 and T4 also play an important role in the regulation of normal body temperature. The production and consumption of ATP by cells generates heat, causing body temperature to rise. This is described as the calorigenic effect.
13. Secretion of T3 and T4
T3 and T4 are lipid soluble and therefore diffuse through the plasma membrane, across interstitial fluid, and enter the bloodstream. -Greater quantities of T4 are secreted, although T3 is the more potent hormone and therefore most T4 is converted to T3 by the removal of an iodine atom, once it enters a cell.
Basal metabolic rate (BMR)
T3 and T4 increase basal metabolic rate, the base (resting) rate at which oxygen is used to produce ATP. -By increasing BMR, T3 and T4 stimulate protein synthesis and cellular metabolism of glucose and fatty acids, thus increasing ATP production. -By stimulating lipolysis and increasing cholesterol excretion, T3 and T4 also reduce levels of cholesterol in the blood.
Acceleration of body growth
T3 and T4 play an important role in the acceleration of growth. They stimulate the growth of tissues throughout the body, especially that of the nervous and skeletal system.
Synthesis of sodium-potassium pumps
T3 and T4 stimulate the synthesis of sodium-potassium pumps (Na+/K+ ATPase). -Sodium-potassium pumps use ATP as an energy source, to actively pump Na+ ions from the cytosol into extracellular fluid at the same time as pumping K+ ions from extracellular fluid into the cytosol.
Up regulation of beta receptors
T3 and T4 stimulate the up regulation of beta receptors, targeted and bound by the catecholamines norepinephrine and epinephrine. -Effects of enhanced norepinephrine and epinephrine beta receptor binding are increased heart rate and contractility and increased blood pressure.
Tumor angiogenesis factors (TAFs)
TAFs are produced and secreted by both normal and cancerous cells, stimulating the growth of new blood vessels in normal and cancerous tissues or tumors. TAFs also promote proliferation and differentiation of cells for organ regeneration and wound healing.
6. TGB packed into secretory vesicles
TGB is packed into secretory vesicles to be transported to the cell surface.
8. TGB stored in the colloid
TGB is stored in the colloid lumen.
Transforming growth factors (TGFs)
TGFs exist in two forms: TGF-alpha and TGF-beta. TGF-alpha is produced and secreted by macrophages, brain cells, and keratinocytes, and stimulates proliferation and differentiation of epithelial cells. TGF-beta exists in three subtypes, all playing a role in tissue regeneration, cell differentiation, embryonic development, and immune responses. They are also known to inhibit the proliferation of many cell types.
Thyrotropin-releasing hormone (TRH)
TRH stimulates the release of thyroid-stimulating hormone (TSH) from the anterior pituitary. TSH travels in the bloodstream to target cells in the thyroid gland, where it stimulates the secretion of thyroid hormones.
Thromboxane (TX)
TX is a modified PG that triggers vasoconstriction and stimulates platelet activation.
what are some examples of steroid hormones?
Testosterone, Estrogen, Progesterone, Aldosterone, Cortisol,Androgen,Calcitriol
F cells
The F cells are classed as a more minor cell type, synthesizing and secreting pancreatic polypeptide.
What is the function of the pituitary gland?
The anterior lobe functions solely as an endocrine organ, while the posterior lobe also has nervous functions and is intrinsically connected to the hypothalamus.
Endocrine glandular epithelial cells (5 types)
The anterior pituitary gland is rich with various types of endocrine glandular epithelial cells. There are five main types: thyrotrophs, corticotrophs, somatotrophs, lactotrophs, and gonadotrophs; each secretes different hormones into surrounding sinusoidal capillaries.
Sinusoidal capillaries
The anterior pituitary has an extensive network of sinusoidal capillaries constituting the secondary hypophyseal plexus. Sinusoidal capillaries are wide and meandering, with large fenestrations in the endothelial cells that make up their walls. They have large intercellular clefts and an incomplete outer basement membrane, enabling secreted hormones to pass from surrounding endocrine cells into the bloodstream.
Beta (B) cells
The centrally located beta cells synthesize and secrete insulin.
7. Vesicles undergo exocytosis
The contents of the vesicles are released into the fluid-filled colloid.
what is the second messenger?
The cyclic AMP produced from the ATP serves as a second messenger.
Many other organs and tissues secrete hormones within the endocrine system but are not classified exclusively as endocrine glands. Functions of the endocrine system include what?
The endocrine system affects almost every aspect of life, controlling and regulating many body functions. -Co-ordination It co-ordinates the general functioning of systems throughout the body through feedback loops. -Homeostasis It helps to maintain a constant, balanced internal environment. -Glandular secretion: It regulates the secretion of hormones from glands throughout the body. -Metabolism: It alters metabolism, controlling the body's energy balance. -Behavior : It plays a key role in the development and influence of behavior. -Growth and development: It regulates the growth and development of body tissues. -Physical appearance: It stimulates the development of certain physical characteristics. -Reproduction: It influences the body's reproductive state. -Digestion: It regulates the operation of digestive organs. -Circadian rhythm: It is involved in the establishment of circadian rhythms. -Body fluids: It regulates the volume and composition of body fluids. -Immune response: It regulates the body's immune response. -Mood and emotions: It controls many aspects of mood and influences emotional states. -Hunger: It initiates hunger cravings and satiety.
Exocrine glands
The exocrine region of the pancreas is composed of clusters of pyramid-shaped secretory cells called acini, which secretes a fluid mixture called pancreatic juice. These regions play an important role in the digestive process. -Pancreatic juice includes a number of digestive enzymes and bicarbonate, which neutralizes acidic chyme in stomach acid, and aid in the breakdown of proteins carbohydrates and lipids.
Fight-or-flight (neuroendocrine) response
The fight-or-flight response quickly mobilizes the body's metabolic substrates, supplying specific tissues with sufficient resources to cope with the demands of the immediate physical activity necessary to combat the stressor.
GROSS ANATOMY OF THE HEART
The heart is located directly on top of the diaphragm behind the sternum. It is positioned in the middle mediastinum, between the left and right lungs. It is roughly cone-shaped with a broad base and a blunt apex. It consists of two upper chambers known as atria, and two lower chambers known as ventricles. The ventricle walls are much thicker than the atria, especially those of the left ventricle, as it must push blood at high pressure around the entire body.
what is the function of the hypothalamus?
The hypothalamus plays an important role in the co-ordination of various homeostatic mechanisms, behavioral patterns, and neuroendocrine outputs.
Fight-or-flight (neuroendocrine) response is initiated by..
The hypothalamus responds immediately to stressors by sending nerve impulses to the sympathetic division of the autonomic nervous system, which activates the adrenal (suprarenal) medulla, causing it to release epinephrine and norepinephrine, which in turn, elicits the fight-or-flight response.
Infundibulum
The infundibulum is continuous with the median eminence of the hypothalamus and consists mainly of neural axons of neurosecretory fibers projecting down from the hypothalamus to the pars nervosa. Capillaries, astrocytes, and glial cells can also be seen here.
Endocrine glands
The islets of Langerhan form approximately 1-2% of the overall mass of the pancreas. These regions are comprised of four different types of hormone secreting endocrine cells: alpha (A) cells, beta (B) cells, delta (D) cells, and F cells. The islets of Langerhan have a vast capillary network surrounding them, and the hormones released by each of these cells are secreted directly into the blood flow
How the posterior pituitary gland control Oxytocin?
The letdown reflex and the suckling reflex controlling oxytocin release are positive feedback mechanisms, where deviation from an ideal normal value is increased in order to promote the original stimulus. When the original stimulus ceases, so does hormone production.
9. Iodination of tyrosine
The newly formed iodine molecules bind to the tyrosine amino acids that form TGB, a reaction that takes place at the apical (colloid-facing) plasma membrane colloid junction and is mediated by the enzyme thyroid peroxidase. -Tyrosine with one bound iodine atom is monoiodotyrosine (T1) and tyrosine with two bound iodine atoms is diiodotyrosine (T2). Iodine-bound TGB accumulates as colloid in the lumen of the thyroid follicle.
4. TGB packed into vesicles
The newly synthesized molecules are then transferred to the Golgi apparatus within vesicles.
Pars distalis
The pars distalis is inferior to the pars tuberalis and constitutes the main body of the anterior pituitary gland. It consists of cords of endocrine glandular epithelial cells lined with basal laminae, which run alongside the basal laminae of sinosoidal capillaries. Small spaces exist between the two types of laminae known as the precapillary spaces, containing fibroblasts, fibrocytes, and unmyelinated neuronal axons.
Pars nervosa
The pars nervosa is the main body of the posterior pituitary gland. It consists of a network of sinusoidal capillaries, surrounded by many neurosecretory fiber terminals supported by pituicytes.
Pars tuberalis
The pars tuberalis is the more superior portion of the anterior pituitary, enveloping the anterior part of the infundibulum (pituitary stalk).
Alpha (A) cells
The peripherally located alpha cells synthesize and secrete glucagon.
Delta (D) cells
The peripherally located delta cells synthesize and secrete somatostatin.
Pituicytes
The pituicytes are elongated or stellate-shaped specialized neuroglial cells surrounding neurosecretory axons. They provide structural and metabolic support to the axons they make contact with.
Fenestrated capillaries
The posterior pituitary has a small but extensive network of fenestrated capillaries that constitutes the posterior hypophyseal plexus.
Oxytocin (OT)'s target organ is?
The pregnant uterus and mammary glands (breast).
Resistance reaction (endocrine response)
The resistance reaction, or endocrine response, prolongs the stress response in order to give the body a better chance of combating the stressor and returning the body's internal environment to within normal physiological limits.
Secondary plexus
The secondary plexus of the hypophyseal portal system, also known as the portal system of the anterior pituitary, or adenohypophysis, extends throughout the anterior lobe of the pituitary gland between cords of endocrine epithelial cells.
what is different about the endocrine system compared to the nervous system in respect of time on target cells?
The speed of influence of the endocrine system on the body's functions is much slower than that of the nervous system as it does not act directly on the target organ. The duration of the effect of the hormone on the body, however, is generally longer lasting than that of a nerve signal, sometimes even causing permanent changes.
Medulla
The suprarenal medulla consists of specialized cells called chromaffin cells, arranged in columns with interconnected fenestrated capillaries running between them.
1. Iodide trapping
The thyroid gland contains a major portion of the body's iodide, which is an essential component of T3 and T4 and therefore must be readily available. -In order to maintain and replenish the supply of iodide, follicular cells are constantly accumulating iodide from the blood. Follicular cells contain over 30 times more iodide than the blood, meaning iodide must travel against the concentration gradient. For this reason, 'iodide trapping' depends on active transport by a sodium iodide symporter or 'iodide trap'.
Thyroid follicles
The walls of each follicle are tightly packed with specialized thyroid epithelial cells, called follicular cells, that have villi-like processes extending into the lumen of the follicle.
HOMEOSTASIS OF THE STRESS RESPONSE: stimulus
There are myriad stimuli that can initiate a stress response. These may be physical (e.g. blood loss or infection) or psychological (e.g. anxiety).
Gases
There are very few known gaseous signaling molecules in the human body. Nitric oxide (NO) is one, acting as both a neurotransmitter and as a local hormone secreted from endothelial cells of blood vessel walls. It is synthesized in the presence of nitric oxide synthase enzymes.
HOMEOSTASIS OF THE STRESS RESPONSE: response
These hormones have multiple effects, which may enable the individual to respond to a real or perceived stressor in a way to alleviate the impact of the stressor. As with most homeostatic mechanisms, this forms a negative feedback loop, with the response permitting a reduction in stimulus. Furthermore, each hormone involved also acts via its own negative feedback loop to reduce further secretion.
Resistance reaction (endocrine response) Stress responses for thyroid hormones
Thryoid hormones stimulate ATP production from glucose in order to supply extra ATP to metabolically active cells during the stress response.
3. TGB synthesis and storage
Thyroglobulin is a large glycoprotein synthesized on the ribosomes of rough endoplasmic reticulum.
Colloid
Thyroid follicles are filled with colloid, a protein-rich store of the thyroid hormone precursor thyroglobulin. It serves as a reservoir of materials for thyroid hormone production and as a store of thyroid hormones themselves, storing an average of a 100-day supply.
The five different types of endocrine glandular epithelial cells constitute the anterior pituitary gland, each synthesizes and secretes different hormones. The five endocrine cells found in the anterior pituitary gland secrete seven different hormones. what are the 5 different ones?
Thyrotrophs, Corticotrophs, Somatotrophs, Lactotrophs, Gonadotrophs
what are two examples of Thyroid hormones?
Thyroxine (T4), Triiodothyronine (T3)
Hormone-receptor complex
When a lipid-soluble hormone, acting as a first messenger, binds its receptor at a hormone binding domain, it triggers a conformational change. This forms an active hormone-receptor complex capable of altering gene expression within the nucleus. This is known as receptor activation.
Stress is
a change in the environment, either external or internal, that pushes on the homeostatic balance within the body.
The supraoptic nucleus (SON) is
a collection of large neurosecretory cell bodies curved over the optic chiasma.
The endocrine system consists of
a collection of widely scattered glands and specialized cells that secrete hormones into the bloodstream.
The placenta is
a disc-shaped organ that forms a connection with the fetus via the umbilical cord.
The anterior pituitary consists of
a mass of endocrine glandular epithelial cells that form continuous cords around an extensive network of sinusoidal capillaries.
The placenta has two sections:
a maternal layer and fetal layer
The pineal gland is
a small endocrine organ mainly associated with the regulation of sleep-wake cycles and the maintenance of the internal body clock.
Each endocrine gland releases
a specific hormone, or number of hormones, that have a defined role in the control of bodily functions.
The resulting hormone-receptor complex then
activates another membrane protein closely associated with the receptor, called a G protein.
As a result, the phosphorylated protein becomes
active and begins to mediate reactions such as glycogen decomposition or the breakdown of triglycerides; ultimately producing physiological responses associated with the hormone that acted as the first messenger.
The anterior pituitary gland is also known as the
adenohypophysis and accounts for about 75% of the total weight of the whole pituitary gland.
This G protein in turn activates
adenylate cyclase, an enzyme that catalyzes the conversion of adenosine triphosphate, known as ATP, into cyclic adenosine monophosphate, known as cyclic AMP (cAMP). This reaction occurs in the cytosol of the cell.
The suprarenal glands, also known as ____, are...
adrenal glands; small, yellow, lobular glands that lie superomedial to the kidneys. They lie behind the peritoneum and are surrounded by fat. They produce several hormones in response to corticoproteins produced by the pituitary gland.
A stress response may be
agreeable or disagreeable, depending on the stressor, and the response may vary person to person depending on the individual's threshold to stress.
Water-soluble hormones include
amines, peptides, and eicosanoids.
The hypothalamus is
an anterior region of the brain, the size of an almond, located below the thalamus and above the brainstem. It constitutes a large number of neurosecretory cell bodies, divided up into a number of small nuclei, with varying functions.
The cell's response to the hormone is also stopped when
an enzyme called phosphodiesterase inactivates cAMP. Similarly, this decreases the activity of adenylate cyclase, suppressing the hormone response.
Each ovary is made up of
an inner medulla and an outer cortex.
Glucose homeostasis is vital for normal physiological function. Glucagon and insulin act
antagonistically to regulate blood glucose levels. The amount of these hormones secreted depends on whether an individual is hyperglycemic (high blood glucose) or hypoglycemic (low blood glucose).
The pituitary gland is structurally and functionally divided into
anterior and posterior lobes, often referred to as separate entities: the anterior pituitary gland and the posterior pituitary gland.
TRH travels in the hypophyseal bloodstream, to the
anterior pituitary, where it stimulates thyrotrophs to secrete thyroid-stimulating hormone (TSH).
Excess levels of glucocorticoids have significant...
anti-inflammatory and anti-immune effects.
As mentioned previously, chromaffin cells of the adrenal medulla function in a similar way to postganglionic sympathetic neurons; they are innervated by preganglionic sympathetic neurons but lack
axons and release hormones rather than neurotransmitters. The hormones they release are epinephrine (adrenaline), and norepinephrine (noradrenaline).
The activation of a target cell by a specific hormone is dependent upon three factors:
blood levels of the hormone, the relative numbers of specific receptors on the target cell, and the affinity of the hormone-receptor bond.
The process begins when the water-soluble hormone diffuses from the
blood within the capillary, through the interstitial fluid, and binds to a specific receptor. This receptor is a transmembrane protein spanning the plasma membrane of a target cell.
Parathyroid hormone (PTH) regulates blood calcium, magnesium, and phosphate levels through its effects on
bone, the kidneys, and the intestines.
PTH and calcitonin are integral to....
calcium homeostasis whereby the opposing actions of PTH and calcitonin regulate levels of calcium in the blood. Both these hormones are regulated by negative feedback.
The parathyroid glands constantly monitor
calcium levels of the blood.
The muscular walls of the heart, known as cardiac muscle or myocardium, comprise cells known as
cardiomyocytes, cardiac myocytes, or cardiac muscle fibers. These cells are adapted to contract without any stimulation and to never tire.
Epinephrine and norepinephrine are
catecholamines, hormones that help regulate the sympathetic division of the autonomic nervous system. They are synthesized and secreted by the adrenal medulla continuously in small amounts, however, during times of excitement, danger, or emotional stress, their secretion is increased, triggering the 'fight-or-flight' response.
What is ANP's action on the kidneys?
causes vasodilation of glomerular arterioles, increasing sodium and water excretion, therefore decreasing blood volume. Also inhibits renin secretion, which in turn inhibits the renin-angiotensin system.
It has a ___ duct, the main pancreatic duct, that ...
central branching; drains each lobule of the pancreas like the veins of a leaf.
The change in the pattern of gene transcription and translation caused by a hormone leads to
changes in cellular activities, which results in a response typical for that specific hormone in that specific cell type.
Hormones are
chemical messengers that circulate in the blood and act upon specific target cells to bring about specific changes in cellular function.
The parathyroid glands are made up of two types of epithelial cells:
chief cells and oxyphil cells.
The umbilical vessels from the fetus reach the
chorion and branch to form convoluted networks which lie within the chorionic villi.
Nutrients and oxygen from the maternal blood move across the walls of the
chorionic villi and into the fetal circulation, while waste products move from the fetal circulation out of the chorionic villi and into the maternal blood.
Hormones are chemical messengers that either...
circulate in the blood, acting upon specific target cells throughout the body, or diffuse through interstitial fluid, acting locally on nearby cells.
Increased T3 and T4 secretion may also be triggered by
cold, hypoglycemia, high altitude, and pregnancy; conditions that increase the body's metabolic rate (increase demand for ATP).
The thicker inner dermis contains two types of fibers:
collagen fibers, which provide the skin with its tensile strength and resistance to stretching forces, and elastic fibers, which provide its recoil properties.
This duct joins with the
common bile duct in the head of the pancreas, which opens into the duodenum at the hepatopancreatic ampulla. There is often an accessory duct that opens into the duodenum independently.
The hypodermis is not classified as a skin layer but lies below the dermis. It is composed of
connective tissue that contains fat, blood vessels, and sensory receptors.
Each kidney consists of an outer ___ and an inner ___. The renal cortex contains ___. The renal medulla contains the_____.
cortex, medulla; arcuate and interlobular arteries and veins. renal pyramids.
A stress response is the body's attempt to
counteract a stressor, using homeostatic mechanisms to maintain an internal environment within normal physiological limits.
Translation is the process of
creating new proteins from the strands of mRNA that were produced during transcription. The mRNA strands bind to their associated ribosomes and act as templates for the synthesis of specific proteins.
lipid soluable hormons bind Intracellular receptors reside either in the
cytosol or the nucleus.
During development, the placenta is formed of a single-cell inner layer of fetal tissue called the ____ and a thicker outer layer called the _____.
cytotrophoblast, syncytiotrophoblast
Water-soluble hormones circulate freely in the blood but cannot
diffuse through the lipid bilayer of the plasma membrane of a cell. Therefore, they must bind to a cell surface receptor in order to trigger an effect inside their target cell.
The pancreas functions as both an
endocrine and exocrine gland, with 99% of its activity centered around exocrine secretion of digestive enzymes and sodium bicarbonate.
The parathyroid glands are so named due to their proximity to the thyroid gland, however, the two
endocrine organs have clearly distinguishable functions.
The skin is composed of two layers, the outer ___ and deeper ___, which rest on the___.
epidermis, dermis, hypodermis
A tube-like structure known as the ___ arises from the superior aspect of each testis and descends to the...
epididymis; tail at the base of the testis where it forms the ductus deferens and ascends into the body.
Three key hormones are synthesized and secreted by cells of the kidneys:
erythropoietin, calcitriol, and renin.
The main female sex hormones are
estrogens and progestins (mainly progesterone), which are steroid hormones produced in the ovary.
There are two types of stress:
eustress, meaning 'good stress', which enhances the functional ability of the body, and distress, the more commonly-referred to type of stress, which is harmful to the body.
Two types of secretory glands exist in the body:
exocrine glands and endocrine glands.
Fat, also known as adipose tissue, is made up of
fat cells, also known as adipocytes. Adipose tissue functions mainly as an energy store and insulator of organs throughout the body. It also has a small endocrine role, secreting the hormone leptin.
The two testes are separated in the midline by
fibrous tissue, known as the median raphe.
The fimbrae are the
finger-like projections of tissue that surround the openings of the uterine tubes; they sweep the oocyte into the uterine tube on its release from the ovary during ovulation.
Water-soluble hormones functions as a___ that acts to stimulate a ____ inside the cell, triggering ...
first messenger, second messenger; a cascade of events that causes a specific hormone-stimulated response.
The parathyroid glands are
four, structurally separate endocrine glands with the common function of synthesizing and secreting parathyroid hormone that regulates the concentration of certain ions throughout the body. -The four, rice-sized parathyroid glands, two superior and two inferior, lie on the posterior surface of the lobes of the thyroid gland. They are functionally distinct from the thyroid gland.
A microscopic structure known as the juxtaglomerular apparatus, residing between the renal corpuscle and the renal tubule, regulates
glomerular blood flow and filtration rate.
The thyroid gland affects the
growth, development, and functioning of various body systems
The seven hormones secreted from the hypothalamic-pituitary axis are integral to the regulation of
growth, development, metabolism, and homeostasis.
Human chorionic somatomammotropin (hCS)
hCS, also known as human placental lactogen (HPL), is a polypeptide hormone synthesized and secreted by the placental syncytiotrophoblast. - targets Mammary glands and various maternal cells -Stimulates development of the Mammary glands in preparation for lactation. -It also regulates maternal metabolism, maintaining a sufficient energy supply to the fetus during pregnancy.
Binding of a lipid-soluble hormone to the binding site of its intracellular receptor forms a
hormone-receptor complex.
Feeding promotes
hyperglycemia as the products of digestion are absorbed from the digestive tract into the blood stream.
Continued fasting results in
hypoglycemia as the supply of available glucose in the body falls.
The hypothalamus and the pituitary gland are connected by an extensive capillary network known as the
hypophyseal portal system.
The pituitary gland, also known as the ___, is...
hypophysis, is a small, pea-sized gland that lies at the base of the brain within the pituitary fossa (hypophyseal fossa) of the sphenoid bone. It is suspended from the hypothalamus by a thin stalk, the infundibulum, that passes posterior to the optic chiasma.
The stress response is under ____control, a region that receives information from almost all parts of the brain.
hypothalamic
The hypothalamus and the pituitary gland work together as a functional unit known as the
hypothalamic-pituitary axis, where neural signals are integrated into hormonal outputs in the form of seven different hormones that enter the bloodstream, targeting other endocrine glands throughout the body.
The thyroid and parathyroid glands are situated
in the neck, anterior to the trachea.
The thyroid gland plays a key role
in the regulation of metabolism.
They target almost all body tissues, ultimately
increasing blood pressure, raising blood glucose levels, and concentrating blood flow to skeletal muscle and the heart; responses that are essentially the same as direct sympathetic nervous stimulation.
The primary plexus of the hypophyseal system, also known as the portal system of the median eminence, surrounds the
infundibulum of the pituitary gland and extends upwards to the median eminence (part of the inferior border of the hypothalamus), where it receives regulatory hormones secreted from hypothalamic neurosecretory fibers.
what is ANP's action on the Suprarenal glands:
inhibits aldosterone release by the suprarenal cortex, and therefore reduces sodium reabsorption and water retention, thus decreasing blood volume.
Endocrine action of pancreatic polypeptide
inhibits gallbladder contraction.
Paracrine action of somatostatin?
inhibits insulin and glucagon release from alpha and beta cells.
Paracrine actions of pancreatic polypeptide
inhibits somatostatin secretion from delta cells and inhibits secretion of digestive enzymes by pancreatic acini.
Calcitonin (CT)
is a polypeptide hormone produced by parafollicular cells, also known as C cells. -Calcitonin (CT) opposes the effects of parathyroid hormone, acting to lower levels of calcium in the blood. -If levels of calcium (Ca2+) in the blood become too high, parafollicular cells of the thyroid gland are stimulated, resulting in increased CT secretion.
Approximately 99% of the specialized cells of the pancreas are exocrine, and produce a number of enzymes, which help in the digestive process. The remaining regions of the pancreas are known as the
islets of Langerhans and contain specialized cells responsible for the endocrine role of the pancreas
The outer epidermis is rich in a tough protein called
keratin and does not contain any blood vessels.
The thyroid gland is one of the ___ in the body. It synthesized and stores __, that do what?
largest endocrine glands in the body. It synthesizes and stores thyroid hormones that influence heart rate, blood pressure, body temperature, energy production, and overall body metabolism, ultimately affecting the development and functioning of the organs throughout the body.
The parathyroid glands control
levels of calcium fixed within bones and circulating in the blood.
Eicosanoids and growth factors are classed separately from other hormones; they are
local hormones with autocrine or paracrine actions.
The effects of adrenal androgens are insignificant in___, but they play an important role in ___, promoting...
males; females: libido (sexual drive) and being converted by other body tissues into feminizing estrogens. The source of all post-menopausal estrogens is adrenal androgens.
Arteries and veins from the mother enter the
maternal layer of the placenta and fill the space between the chorionic villi, known as the intervillous space, with maternal blood.
The suprarenal glands consist of an inner ___ and an outer ____, which are....
medulla, cortex; embryologically and functionally separate.
The cortex forms
most of the volume of the ovary. It is composed of a series of stromal cells (connective tissue cells) within a network of collagen fibers, housing the ovarian follicles. Ovarian follicles comprise layers of cells, depending on their stage of development.
Chronic exposure of the body to high levels of the hormones produced during the stress response causes negative effects, such as
muscle wastage, pancreatic beta cell failure, and suppression of immune system functioning. If the resistance reaction is further prolonged, detrimental pathological changes may occur.
As the BMR rises to within normal limits, the elevated level of T3 triggers
negative feedback inhibition of TRH and TSH secretion.
Synthesis and release of most hormones is regulated by
negative feedback systems, in which endocrine glands are stimulated to secrete their hormones by neural stimuli (nervous system), humoral stimuli (chemical changes in the blood), and hormonal stimuli (regulatory hormones).
Secretion of anterior pituitary hormones that do not have associated inhibiting hormones is controlled by
negative feedback. As blood levels of the hormones secreted by target glands rises above an ideal normal value, secretion of associated hormones from the anterior pituitary is suppressed, thus inducing a negative effect on target glands, bringing hormone levels back to an ideal normal value. This system is known as a negative feedback loop: the secretory activity of thyrotrophs, gonadotrophs, and corticotrophs is controlled in such a way.
Within the kidney are millions of ---, the functional units of the urinary system
nephrons;
Vesicles containing OT and ADH are stored in axon terminals until
nerve impulses trigger their release into nearby sinosoidal capillaries by exocytosis.
It works alongside the
nervous system to regulate all aspects of body function.
A portal system is a
network whereby blood travels through two capillary networks before returning to the heart. This direct vascular link is essential for the neurohormonal control of the secretory activity of the hypothalamic-pituitary axis.
The posterior pituitary gland, also known as the____ , it includes the....
neurohypophysis, includes the infundibulum or pituitary stalk that attaches the pituitary to the hypothalamus, and more inferiorly, the pars nervosa.
OT and ADH are synthesized in
neurosecretory cells in the PVN and SON of the hypothalamus. They are packed into secretory granules and transported down axons that form the hypothalamohypophysial tract, to axon terminals in the posterior pituitary.
Each hormone-receptor complex turns into a ___ which is capable of doing what?
now a functional transcription factor, binds nuclear DNA at one of a range of DNA binding domains and switches specific genes on or off. Different hormone-receptor complexes bind to a different range of genes.
The cyclic AMP activates
one or more protein kinases. Protein kinases are enzymes that phosphorylate other enzymes and proteins.
The suprarenal glands consist of a thin inner medulla, dark red or grayish in color, which makes up about ___ glands, and a yellowish outer cortex, which forms the ___ gland.
one-tenth of the; majority of each
The __ is the primary organ of the female reproductive system; it is shaped like...
ovary; an almond and is located in the ovarian fossa close to the lateral pelvic wall.
The posterior pituitary is not capable of hormone synthesis, it does however store and release two hormones,
oxytocin (OT) and antidiuretic hormone (ADH), also known as vasopressin.
When these levels are low, they produce...
parathyroid hormone (PTH), which triggers calcium to be leached from the bones and released into the blood. When calcium levels return to normal, they stop producing the hormone.
The two main hypothalamic nuclei involved in the hypothalamic-pituitary axis are the
paraventricular and supraoptic nuclei. They synthesize and secrete the neurohormones involved in the regulation of the anterior and posterior pituitary glands.
The maternal layer is composed of
part of the endometrium
OT and ADH enter the portal system of the posterior pituitary, from where they
pass into the posterior hypophyseal veins and are distributed to distant target cells.
Other organs and tissues with endocrine functions include the... (8)
pineal gland, thymus gland, gastrointestinal tract, placenta, kidneys, heart, skin, and fat
Atrial natriuretic peptide (ANP), also known as atrial natriuretic factor (ANF), atrial natriuretic hormone (ANH), or atriopeptin, is a
polypeptide hormone synthesized and secreted by cardiac myocytes (heart muscle cells) in the atria of the heart. It is secreted in response to atrial stretch, caused by high blood pressure and angiotensin II. - targets Suprarenal glands, kidneys, blood vessels, and adipose tissue.
For example, exercise is usually a
positive stressor, helping to strengthen and condition the body, but it can also be a negative stressor, when over-exercising results in injury and illness.
They also regulate the
pressure, volume, pH, and salt balance of the blood.
The hypophyseal portal system is formed by a
primary and secondary plexus and supplies the anterior pituitary gland. The posterior pituitary gland is drained by a posterior plexus
The fetal layer is formed by
processes known as chorionic villi, which extend into the endometrium from a fetal membrane known as the chorion.
Adrenal androgens play an important role in males and females during
puberty, promoting growth spurts and stimulating growth of axillary and pubic hair.
Hormones act through...
receptors expressed either on the surface of a target cell, spanning the plasma membrane, or inside a target cell. Binding of a hormone to its specific receptor causes a cascade of reactions to occur inside the target cell, ultimately affecting its function.
Hormones interact with other hormones in different ways in order to
regulate various physiological responses.
Secretion of anterior pituitary hormones is controlled by regulatory hormones, known as
releasing hormones and release-inhibiting hormones, released from parvocellular neurons of the PVN into the primary portal system of the median eminence. These hormones then travel in the portal blood to their target cells in the anterior pituitary. -Releasing hormones stimulate the secretion of specific anterior pituitary hormones, while inhibiting hormones suppress secretion of specific anterior pituitary hormones.
Found inside the renal cortex is the first part of the nephron, the...
renal corpuscle. It consists of a tubular capsule wrapped around a tight network of capillaries, the glomerulus.
The next part of the nephron, the ____, connects the renal corpuscle to the ____, which gather up the urine from several different nephrons.
renal tubule, collecting ducts
The ____ suprarenal gland is pyramid-shaped, whereas the___ has a flatter appearance and is slightly larger.
right, left
All these contain
secretory endocrine cells that synthesize and secrete various hormones that mediate the functioning of specific processes within the body.
Hormones of the posterior pituitary gland are stored in
secretory granules in axon terminals until nerve impulses stimulate the neurosecretory cells, triggering exocytosis and release of the hormone into interstitial fluid, and ultimately, into the bloodstream.
It is best to think of the anterior and posterior pituitary as separate entities in terms of the hormones they secrete as...
separate entities in terms of the hormones they secrete and how they are regulated. Not only are they anatomically separate, but there are also clear functional differences.
Hormones of the pituitary gland are therefore classified according to the lobe from which they are released. There are ___ hormones released into the blood from the anterior pituitary and____ released from the posterior pituitary.
seven, two
Normal levels of glucocorticoids stimulate
several different metabolic processes that ultimately maintain levels of glucose in the blood and provide resistance to stress.
Eicosanoids are
signaling molecules, present in almost all body cells except red blood cells, that exert complex control over various body systems. Eicosanoids have a short half-life, due to rapid inactivation, and so only small quantities can be measured circulating in the blood.
The posterior plexus, more commonly known as the portal system of the posterior pituitary or neurohypophysis, is
slightly less developed than that of the anterior pituitary and as the name suggests, is situated within the body of the posterior lobe of the pituitary gland. Hormones secreted from hypothalamic neurosecretory fibers enter the bloodstream via this posterior plexus.
When the G proteins are no longer stimulated by the binding of hormones to cell surface receptors, they
slowly inactivate. This decreases the activity of adenylate cyclase and dampens the hormone response.
Endocrine action of somatostatin
slows absorption of nutrients from GI tract
Just as neurons are the functional units of the nervous system, ___ cells and ___ are the functional units of the endocrine system.
specialized secretory and glands
Juxtaglomerular cells are
specialized smooth muscle cells in the wall of the afferent arteriole supplying the glomerulus. They synthesize and secrete the hormone renin.
The thyroid gland is made up of numerous
spherical thyroid follicles, surrounded by a vast capillary network extending throughout the thyroid gland.
The heart is a
strong muscular pump essential in the delivery of oxygen to the millions of cells of the body and in the removal of their waste products. It pushes deoxygenated blood to the lungs and around the entire body.
Placental cells derived from these layers do what?
synthesize and secrete large quantities of a number of different hormones
The___ are the primary organs of the male reproductive system.
testes; They are ovoid in shape and are suspended outside the body in the scrotum.
The main male sex hormone is
testosterone, which is an androgen produced by the testes.
It occurs in three stages:
the fight-or-flight response occurs immediately, followed by a longer-lasting resistance reaction, and finally, if the resistance reaction fails, the body enters a state known as exhaustion.
If BMR drops below a certain limit, or the levels of T3 and T4 in the blood become low what happens?
the hypothalamus is stimulated, resulting in the secretion of thyrotropin-releasing hormone (TRH) into the hypophyseal portal system.
As part of the hypothalamic-pituitary axis, the hypothalamus provides
the important link between the nervous system and the endocrine system.
Cholecalciferol is
the inactive form of vitamin D, structurally similar to steroid hormones. It is synthesized and secreted by the skin in the presence of ultraviolet light of a specific wavelength. - targets Hepatocytes of the liver, where it is turned into calcifediol, and ultimately, cells of the proximal tubule of the nephron in the kidneys, where it is turned into calcitriol. -Stimulates the production of calcitriol, the most active, circulating form of vitamin D.
In both males and females, sex hormones are also responsible for
the increased activity of sweat glands and sebaceous glands, and the growth of pubic and armpit hair.
Gonads are
the organs responsible for gamete production; testes produce spermatocytes in the male and ovaries produce oocytes in the female. The gonads also synthesize and secrete hormones known as sex hormones.
It is often described as having two distinctive parts
the pars tuberalis and the pars distalis.
If a gene is switched off by the transcription factor, what happens?
the rate of transcription of that gene is inhibited or halted.
Stressors?
the stimuli that disturb the balance, cause a stress response. These can be as simple as a change in air temperature or the ingestion of a meal. Alternatively, they may be severe, as in the tissue damage and blood loss that accompanies an injury. Psychological stressors, including intense emotional reactions that result in anxiety, also alter the homeostatic balance.
TSH travels in the bloodstream to the
thyroid gland, where it stimulates the activity of thyroid follicular cells, promoting the synthesis and release of T3 and T4 into the blood
Thyroid follicular cells produce two different hormones:
thyroxine, also known as tetraiodothyronine or T4, and triiodothyronine, also known as T3.
The kidneys function to
to filter the blood by excreting waste and excess water as urine.
The thyroid gland sits in front of the __. It consists of a
trachea at the level of C7-T1. right and left lobe, which sit on either side, connected by a central strip called the isthmus.
If a gene is switched on, that section of DNA is
transcribed. During this process strands of new messenger RNA (mRNA) are produced using the DNA of that gene as a template. This mRNA then exits the nucleus, relocating to ribosomes within the cytosol.
Structurally, these two hormones are very similar as they are both constructed from
two linked tyrosine amino acids, but they differ in their iodine content.
It has four parts, the
uncinate process, head, body and tail.
Growth factors are?
usually protein or steroid hormones, are naturally occurring mitogenic substances that stimulate tissue development, growth, and repair through cell division
The __ covers the medial surface and the ___ cover the lateral surface.
uterine tube, fimbrae
The medulla is highly ___ and comprises __. It provides...
vascular; loose connective tissue, blood vessels, and nerves. It provides structural support along with a rich blood supply for hormone and nutrient transport.
What is ANP's action on the blood vessels?
vasodilation (relaxes vascular smooth muscle).
Hormones are usually classified either as
water-soluble hormones or as lipid-soluble hormones. These two main groups of hormones exert their effects differently due to a difference in their chemical structure.
Amino acid-based and other non-steroid hormones are classified as
water-soluble hormones.
