Biology Ch 5. The Endocrine System Flashcards
Endocrine signaling
The secretion of hormones directly into the bloodstream, the hormones travel to distant target tissues were they bind to receptors and induce a change in gene expression or cell function
Peptide hormones
Composed of amino acids and are derived from larger precursor proteins that are cleaved during posttranslational modification, are polar and cannot pass through the plasma membrane, bind to extracellular receptors to trigger transmission of a second messenger, exert effects that have rapid onset but are short lived, water-soluble so travel freely in bloodstream without special carrier
Second messenger
Transmitted when peptide hormones bind to extracellular receptors, common examples include cyclic adenosine monophosphate (cAMP), inositol triphosphate (IP3), and calcium
Signaling cascade
The connection between the hormone at the surface and the effect brought about by second messengers within the cell, each step can induce amplification of the signal
Amplification
Increase in signal intensity
Steroid hormones
Derived from cholesterol, or minimally polar and can pass through the plasma membrane, buying two and promote a conformational change in cytosolic or intranuclear receptors, the hormone receptor complex binds to DNA altering the transcription of a particular gene, exert affects that have slow onset butter long lived, or lipid soluble so they cannot dissolve in the blood stream and must be carried by specific proteins
Amino acid – derivative hormones
Modified amino acids, chemistry share some features with peptide hormones and some features with steroid hormones, different amino acid derivatives hormones share different features with these other hormone classes, examples include epinephrine, norepinephrine, triiodothyronine, and thyroxine
Hormone types
Chain hormones, steroid hormones, amino acid derivative hormones
Hormone classifications by target tissues
Direct hormones, tropic hormones
Direct hormones
Have major effects on non-endocrine tissues
Tropic hormones
Have major effects on other endocrine tissues
Hypothalamus endocrine system
Bridge between the nervous and endocrine systems, releases many hormones and is mediated by a number of factors, stimulates the anterior pituitary gland through paracrine release of hormones into the hypophyseal portal system which connects the two organs, interacts with the posterior pituitary via the axons of nerves projected by the hypothalamus
Hypothalamus mediation factors
Projections from other parts of the brain, chemo or baroreceptors in the blood vessels, and negative feedback from other hormones
Negative feedback
The final hormone (or product) of a pathway inhibits hormones (or enzymes) earlier in the pathway, maintaining homeostasis
Gonadotropin-releasing hormone
GnRH - promotes the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
Growth hormone releasing hormone
GHRH - promotes the release of growth hormone
Thyroid-releasing hormone
TRH – promotes the release of thyroid stimulating hormone (TSH)
Corticotropin – releasing factor
CRF - promotes the release of adrenocorticotropic hormone (ACTH)
Prolactin inhibiting factor
PIF or dopamine - inhibits the release of prolactin
Hormones from the hypothalamus
To the anterior pituitary Gonadotropin releasing hormone (GnRH) Growth hormone releasing hormone (GHRH) Thyroid releasing hormone (TRH) Corticotropin releasing factor (CRF) Prolactin inhibiting factor (PIF or dopamine)
To the posterior pituitary
Antidiuretic hormone (ADH or vasopressin)
Oxytocin
Anterior pituitary
Releases hormones in response to stimulation from the hypothalamus
Tropic hormones
FSH, LH, ACTH, and TSH
Direct hormones
Prolactin, endorphins, and growth hormone
Follicle-stimulating hormone
FSH - promotes the development of ovarian follicles in females and spermatogenesis in males, peptide hormone
Luteinizing hormone
LH - promotes ovulation in females and testosterone production in males, peptide hormone
Adrenocorticotropic hormone
ACTH - promotes the synthesis and release of glucocorticoids from the adrenal cortex, peptide hormone
Thyroid stimulating hormone
TSH - promotes the synthesis and release of triiodothyronine and thyroxine from the thyroid, peptide hormone
Prolactin
Promotes milk production, peptide hormone
Endorphins
Decrease perception of pain and can produce euphoria, peptide hormone
Growth hormone
GH - promotes growth of bone and muscle and shunts glucose to these tissues, raises blood glucose concentrations, peptide hormone
Posterior pituitary
Releases two hormones produced in the hypothalamus
Antidiuretic hormone
ADH or vasopressin - secreted in response to low blood volume or increased blood osmolarity and increases reabsorption of water in the collecting duct of the nephron, increasing blood volume and decreasing was osmolarity, peptide hormone
Oxytocin
Secreted during childbirth and promotes uterine contractions, also promotes milk ejection in may be involved in bonding behavior, unusual in that it has a positive feedback loop, peptide hormone
Thyroid
Located at the base of the neck in front of the trachea, it produces three key hormones: triiodothyronine, thyroxine, calcitonin
Triiodothyronine
T3 - produced by follicular cells and contain iodine, increase basal metabolic rate and alter the utilization of glucose and fatty acids, are required for proper neurological and physical development in children, amino-acid derivative hormone
Thyroxine
T4 - produced by follicular cells and contain iodine, increase basal metabolic rate and alter the utilization of glucose and fatty acids, are required for proper neurological and physical development in children, amino acid derivative hormone
Follicular cells
In thyroid, produce triiodothyronine and thyroxine
Calcitonin
Produced by parafollicular cells, decrease plasma calcium concentration by promoting calcium excretion in the kidneys, decreasing calcium absorption in the gut, and promoting calcium storage in the bone, peptide hormone
Parathyroid glands
Release parathyroid hormone, four small structures on the surface of thyroid
Parathyroid hormone
PTH - increases blood calcium concentration, decreases excretion of calcium by the kidneys and increases bone reabsorption directly to increase blood calcium concentration, activates vitamin D which is necessary for calcium and phosphate absorption in the gut, peptide hormone
PTH and vitamin D
PTH promotes reabsorption of phosphate from bone in reduces reabsorption from phosphate in the kidney, but vitamin D promotes absorption of phosphate from the gut, these two affects on phosphate concentration somewhat cancel each other out
Adrenal cortex
Produces three classes of steroid hormones
Glucocorticoids
Increase blood glucose concentration, reduce proteins synthesis, inhibit the immune system, and participate in the stress response, release is stimulated by ACTH age, examples include cortisol and cortisone, steroid hormones
Mineralocorticoids
Promotes sodium reabsorption in the distal convoluted tubule and collecting duct, thus increasing water absorption, one example is aldosterone, steroid hormones
Aldosterone
Promotes sodium reabsorption in the distal convoluted tubule and collecting duct, thus increasing water reabsorption, also increases potassium and hydrogen ion excretion, activity regulated by the renin-angiotensin-aldosterone system, not ACTH, steroid hormone
Cortical sex hormones
Include androgens and estrogens in both males and females
Adrenal medulla
Derived from the nervous system and secretes catecholamines into the bloodstream
Catecholamines
Include epinephrine and norepinephrine, involved in the fight or flight response, promote glycogenolysis, increase the basal metabolic rate, increase heart rate, dilate the bronchi, and alter blood flow, amino acid derivate hormones
Pancreas
Produces hormones that regulate glucose homeostasis such as glucagon, insulin, and somatostatin
Glucagon
Produced by alpha cells and raises blood glucose levels by stimulating proteins and fat degradation, glucogenolysis, and gluconeogenesis, peptide hormone
Insulin
Produced by beta cells and lowers blood glucose levels by stimulating glucose uptake by cells and promoting anabolic processes like glycogen, fat, and protein synthesis, peptide hormone
Somatostatin
Produced by Delta cells and inhibits insulin and glucagon secretion, peptide hormone, stimulated by high blood glucose and amino acid concentration
Gonads - testes/ovaries
Produce hormones that are involved in the development and maintenance of the reproductive system and secondary sex characteristics
Testes hormones
Secrete testosterone, steroid hormones
Ovaries hormones
Secrete estrogen (development and maintenance of reproductive system and secondary sex char) and progesterone (endometrium maintenance), steroid hormones
Pineal gland
Releases melatonin
Melatonin
Helps to regulate the circadian rhythm, peptide hormone
Stomach and intestine hormones
Secretin, gastrin, and cholecystokinin, peptide hormones
Kidneys hormones
Secrete erythropoietin
Erythropoietin
Stimulates bone marrow to produce erythrocytes in response to low oxygen levels in the blood, peptide hormone
Atria of the heart hormones
Secrete atrial natriuretic peptide (ANP)
Atrial natriuretic peptide
ANP - promotes excretion of salt and water in the kidneys in response to stretching of the atria (high blood volume), peptide hormone
Thymus hormones
Secretes thymosin
Thymosin
Important for proper T-cell development and differentiation, peptide hormone
Glands
Organs that secrete hormones
Dimerization
Common conformational change, the pairing of two receptor-hormone complexes
Hypophyseal portal system
A blood vessel that directly connects the hypothalamus and the anterior pituitary
Axes
Three organ systems
Gigantism
Excess of GH during childhood before epiphyseal (growth) plates close
Dwarfism
Lack of GH during childhood before epiphyseal (growth) plates close
Acromegaly
Excess of GH in adulthood after epiphyseal (growth) plates close, long bones are sealed so primarily the feet, hands, and head grows
Hypothyroidism
Thyroid hormones secreted in insufficient amounts, lethargy, decreased body temp, slowed respiratory and heart rate, cold intolerance, and weight gain symptoms
Hyperthyroidism
Excess of thyroid hormones, could result in tumor or thyroid overstimulation
Adrenal glands
On top of kidney, broken into adrenal cortex and adrenal medulla
Renin-angiotensis-aldosterone system
Decreased blood pressure causes the juxtaglomerular cells of the kidney to secrete renin which cleaves an inactive plasma proteins, angiotensinogen, to its active form angiotensin I, which is converted to angiotensin II with angiotensin-converting enzyme in the lungs, angiotensin II stimulates the adrenal cortex to secrete aldosterone
Exocrine tissues
Secrete substances directly into ducts such as digestive enzymes
Islet of Langerhans
Small clusters of hormone producing cells throughout the pancreas, contains alpha, beta, and delta cells
Hypoglycemia
Low blood glucose concentration, can be caused by an excess in insulin
Diabetes mellitus
The result of underproduction, insufficient secretion, or insensitivity to insulin, clinically characterized by hyperglycemia
Hyperglycemia
Excess glucose in the blood
Polyuria
Increased frequency of urination, common in diabetics
Polydipsia
Increased thirst, common in diabetics
Type I diabetes
Insulin-dependent, caused by autoimmune destruction of the beta cells in the pancreas, resulting in lower or absent insulin production, requires injections of insulin to prevent hyperglycemia and permit uptake of glucose into cells
Type II diabetes
Non-insulin-dependent, the result of receptor level resistance to the effects of insulin, partially inherited and partially due to environmental factors such as diet, certain pharmaceutical agents can be taken orally to help the body more effectively use up the insulin it produces
