Chapter 12- Endocrinology Flashcards
What do endocrine glands do?
How are exocrine glands different
Secrete chemical substances called hormones directly into the circulatory system.
Exocrine= secretion not direct, has to be transported by ducts.
Glands and organs that synthesize or secrete hormones are:
pituitary, hypothalamus, thyroid, parathyroids, adrenals, pancreas, testes, ovaries, pineal, kidneys, gastrointestinal glands, heart, and thymus.
What is the specificity of hormonal action determined by?
The presence of specific receptors on or in the target cells.
Where are the adrenal glands situation what what do they consist of?
They are situated on the top of the kidneys and consist of the adrenal cortex and the adrenal medulla
ACTH
adrenocorticotropic hormone- produced by adrenal pituitary. Stimulates the production of adrenocortical steroids (collective name for more than two dozen hormones, also known as corticosteroids).
Transcortins
What corticosteroids bind to in the bloodstream.
How do corticosteroids exert their mechanism?
They determine which genes are transcribed in the nuclei of their target cells and at which particular rate. Then they change the nature and given concentration of the enzyme, which will affect cellular metabolism.
Glucocorticoids
Cortisol and cortisone– involved in glucose regulation and protein metabolism.
Increase plasma glucose levels and are antagonist to the effect of insulin
How do glucocorticoids raise blood glucose levels?
They promote protein breakdown and gluconeogenesis and decrease protein synthesis.
What do glucocorticoids release?
Amino acids from skeletal muscles and lipids from adipose tissue.
Also promote peripheral use of lipids and have anti-inflammatory effects
Mineralocorticoids
Aldosterone
Regulate plasma levels of sodium and potassium, and the total extracellular water volume.
What does aldosterone cause?
Active reabsorption of sodium and passive reabsorption of water in the nephron of the kindey.
What do the affects of aldosterone result in?
An increase in blood volume and blood pressure.
What does excess production of aldosterone cause?
Excess retention of water- hypertension
What are mineralocorticoids stimulated by?
Angiotensin II
What are mineralocorticoids stimulated by?
ANT (atrial natriuretic peptide)
Cortical sex hormones secreted by adrenal cortex
Secretes small quantities of androgens in both men and women
Effect not great in men
In women, can lead to masculinizing effects
What does the adrenal medulla produce?
Epinephrine (adrenaline) and norepinephrine (noradrenaline).
Catecholamines
Amino-acid derived compounds to which both epinephrine and norepinephrine belong to.
Epinephrine
Increases conversion of glycogen to glucose in liver and muscle tissue, causing an increase in blood glucose levels.
INCREASE in the basal metabolic rate.
Both epinephrine and norepinephrine cause:
Increase the rate and strength of the heartbeat
Constrict and dilate blood vessel in increase supply to:
skeletal muscles
heart
brain
decrease supply to:
kidneys
skin
digestive tract
Also promotes the release of lipids by adipose tissue.
Effects of epinephrine and norepinephrine are known as the :
flight or fight response
Effects of epinephrine and norepinephrine are elicited by:
the sympathetic nervous stimulation to stress
True or false: both epinephrine and norepinephrine are neurotransmitters
True
they are both proteins used by neurons to transmit signals- stimulated by sympathetic preganglionic fibers.
What is the pituitary and where is it located?
Small trilobed gland lying at the base of the brain. Hangs below the hypothalamus and is connected by a slender cord known as the infundibulum.
What are the two main lobes of the pituitary? Are they functionally distinct?
Anterior and Posterior.
Yes they are functionally distinct.
Anterior pituitary synthesizes (2):
Direct hormones
Directly stimulate their target organs
Tropic hormones
Stimulate other endocrine glands to rlease hormones
What are hormone secretions of the anterior pituitary regulated by?
Hypothalamic secretions called releasing/ inhibiting hormones or factors.
What are examples of direct hormones?
Growth hormone (GH, somatotropin) Prolactin
Growth hormone
Promotes bone and muscle growth. Also promotes protein synthesis and lipid mobilization and catabolism.
What can GH deficiency in children cause? What does over production cause.
Dwarfism (growth stunt)
Gigantism
What can GH over production in adults cause?
Acromegaly: a disorder characterized by disproportionate overgrowth of bone, localized especially in the skull, jaw, feet and hands.
Prolactin
Stimulates milk production and secretion in female mammary glands
What are examples of tropic hormones?
Adrenocorticotropic hormone (ACTH) Thyroid-stimulating hormone (TSH) Luteinizing hormone (LH) Follicle-stimulating hormone (FSH) Malanocyte-stimulating hormone (MSH) Endorphins
ACTH
Adrenocorticotropic hormone. Stimulates the adrenal cortex to synthesize and secrete glucocorticoids and is regulated by corticotrophin-releasing factor (CRF)
TSH
Thyroid-stimulating hormone. Stimualtes the thyroid gland to synthesize and release thyroid hormones, including thyroxin.
LH
Luteinizing hormone.
Women: stimulates ovulation and formation of corpus luteum.
Regulates progesterone secretion.
Men: Stimulates interstitial cells of the testes to synthesize testosterone.
FSH
Follicle stimulating hormone.
Women: causes maturation of ovarian follicles that begin secreting estrogen
Men: FSH stimulates maturation of the seminiferous tubules and sperm production.
MSH
Melanocyte-stimulating hormone. Secreted by the intermediate lobe of the pituitary. Function unclear in humans, in frogs, causes darkening of skin.
Endorphins
Neurotransmitters that have pain-relieving properties
Posterior pituitary (neurohypophysis)
Does not synthesize hormones- stores and releases peptide hormones oxytocin and ADH
Oxytocin and ADH are stimulated and produced by?
Stimulated by action potentials descending from the hypothalamus and produced by the neurosecretory cells of the hypothalamus
Oxytocin
Secreted during childbirth- increases muscle contraction
-Also induced by suckling, stimulates milk secretion
ADH
Antidiuretic hormone (vasopressin) Increases permeability of nephron's collecting duct to water
promotes water reabsorption, increases BO.
When is ADH secreted?
When plasma osmolarity increases as sensed by osmoreceptors in the hypothalamus or when blood volume decreases, as sensed by baroreceptors in the circulatory system.
What is hypothalamus and where is it located?
Part of the forebrain and is located directly above the pituitary gland.
What does the hypothalamus receive?
Neural transmissions from other parts of the brain and from peripheral nerves that trigger specific responses from its neurosecretory cells.
Neurosecretory cells.
regulate pituitary gland secretions via negative feedback mechanisms and through the actions of inhibiting and releasing hormones.
Hypothalamic-releasing hormones
Stimulate or inhibit the secretions of the anterior pituitary.
GnRH
Stimulates the anterior pituitary to secrete FSH or LH
Where are releasing hormones secreted into?
The hypothalamic-hypophyseal portal system
hypothalamic-hypophyseal portal system
Circulatory pathway, blood from capillary bed in the hypothalamus flows through a portal vein and into the anterior pituitary, where it diverges into a 2nd capillary network
When plasma levels of adrenal cortical hormones drop, hypothalamic cells release?
ACTH-releasing factor via negative feedback into the portal vein. When the plasma concentration of corticosteroids exceeds the normal plasma level, the steroids themselves exert an inhibitory effect on the hypothalamus
Neurosecretory cells in the hypothalamus synthesize both _____ and ____ and transport them via their _____ into the ______ _______ for ______ and ______
oxytocin and ADH and transport them via their axons into the posterior pituitary for storage and secretion
Thyroid hormones affect the function of:
nearly every organ system in the body
In children, thyroid hormones are important for:
growth and development
In adults, thyroid hormones are important for:
maintenance of metabolic stablility
What the the thyroid hormones and where are they formed?
Thyroxine (T4) and Triiodothyronine (T3). Are formed on the glycoprotein thyroglobulin, which is synthesized in the thyroid cell.
How are active thyroid hormones formed?
Because of the specific tertiary structure of thyroglobulin, iodinated tyrosine residues present in the thyroglobulin are able to bind together.
True or false: T3 is five times more potent than T4
TRUE
What are T4 and T3 transported in the blood by?
The proteins TBG, TBPA, and albumin
What kind of hormone is able to enter a cell and cause a cellular response?
Only hormones that are not bound to proteins
All of the T4 in the body is formed and secreted by the:
Thyroid gland
x% of T3 is produced by the thyroid gland
20%
The majority of T3 is produced by
The conversion of T4 to T3 by the enzyme 5’-monodeiodase, found primarily in the peripheral tissues.
What are T4 and T3 derives from?
The iodination of the amino acid tyrosine.
Hypothyroidism
Thyroid hormones are undersecreted or not secreted at all.
Symptoms of hypothyroidism:
Slowed heart rate and respiratory rate
fatigue
cold intolerance
weight gain
Cretinism
Hypothyroidism in newborn infants- characterized by mental retardation and short stature
Hyperthyroidism
Thyroid is overstimulated, resulting in the oversecretion of thyriod hormones
Symptoms of hyperthyroidism
Increased metabolic rate feelings of excessive warmth profuse sweating palpitations weight loss protruding eyes
Goiters are a result of
Both hypo and hyperthyroidism
Calcitonin
decreases plasma Ca2+ by inhibiting the release of Ca2+ from bone.
Calcitonin secretion is regulated by:
Plasma Ca2+ levels
Calcitonin is antagonistic to the
parathyroid hormone
Pancrease
is both an exocine and endocrine organ.
Exocrine function of the pancreas is preformed by
The cells that secrete digestive enzyme into the small intestine via a serives of ducts
The endocrine function of the pancreas is performed by:
small glandular structures called the islets of Langerhans, which are compused of alpha and beta cells.
Alpha cells
Produce and secrete glucagon
Beta cells
Produce and secrete insulin
Glucagon
Stimulates fat and protein degradation, the conversion of glycogen to glucose and gluconeogenesis- all of which serve to increase blood glucose levels.
Insulin
Protein hormone secreted in response to a high blood glucose concentration
Stimulates uptake of storage by muscle and adipose cells
storage of glucose as glycogen in muscle and liver cells
Underproduction of insulin and insensitivity to insulin causes
diabetes mellitus- characterized by hyperglycemia (high blood glucose levels).
Parathyroid glands
Four small, pea-shaped structures embedded in the posterior surface of the thyroid.
What do the parathyroid glands synthesize and secrete?
PTH (parathyroid hormone) which regulates plasma Ca2+ concentration.
What does PTH do?
Raises Ca2+ concentration in the blood by stimulating Ca2+ release from the bone and deceasing Ca2+ excretion in the kidneys.
Calcium in bone is bonded to:
Phosphate and breakdown of bone releases phosphate as well as calcium. Parathyroid hormone compensates for this by stimulating excretion of phosphate by the kidneys
Renin
Produced when blood volume falls- an enzyme that converts the plasma protein angiotensin to angiotensin I
Angiotensin I is converted to _____, which
angiotensin II, which stimulates the adrenal cortex to secrete aldosterone
What does aldosterone do?
Helps to restore blood volume by increasing sodium reabsorption at the kidney, leading to the increase in water. This removes initial stimulus for renin prodution
Erythropoietin (EPO)
Produced by the kidneys, a glycoprotein that stimulates RBC production. Causes:
Stimulation of stem cells to differentiate into rubriblasts (least mature erythrocyte)
Increased rate of mitosis
Increased release of reticulocytes from the bone marrow
Increased hemoglobin formation
Ingested food stimulates the stomach to release the hormone:
Gastrin
Gastrin
Carried to the gastric glands and stimulates the glands to secrete HCl in response to food in the stomach.
Secretion of pancreatic juice or the exocrine secretion of the pancreas is also under:
hormonal control, the hormone secretin is released by the small intestine when acidic food material enters from the stomach
Chyme
Partially digested food coming from the stomach. Acidic, secretin stimulates the secretion of an alkaline bicarbonate solution from the pancreas that neutralizes chyme.
Cholecystokinin
Hormone released from the small intestine in response to the presence of fats and causes the contraction of gall bladder and release of bile into the small intestine.
Bile in involved in the:
Emulsification and digestion of fats
Pineal gland
A tiny structure at the base of the brain that secretes melatonin
Role of melatonin
Unclear in human, believed to play a role in the circadian rhythms
Melatonin secretion is regulation by
light and dark cycles in the environment.
In primitive vertebrates, melatonin:
Lightens skin by concentrating pigment granules in melanophores.
Antagonist to MSH
Peptide hormones range from:
Simple short peptides such as ADH to complex polypeptides, such as insulin
Peptide hormones act as:
first messengers
Peptide hormones bind to
specific receptors on the surface of their target cells
triggers a series of enzymatic reactions within each cell- first: conversion of ATP to cyclic AMP
Cyclic AMP
acts as a second messenger to relay messages from the extracellular peptide hormone to the cytoplasmic enzymes and initiating a series of successive reactions in the cell (cascade effect)
What is cAMP activity inactivated by?
Cytoplasmic enzyme phosphodiesterase
Steroid hormones belong to a class of:
Steroid hormones belong to a class of lipid-derived molecules with a characteristic ring structure
What are steroids produced by?
Testes, ovaries, placenta, and adrenal cortex
Steroid hormones do what to activates gene expression?
Because they are lipid soluble, they cross the phospholipid bilayer and enter their target cells directly in order to bind to specific receptor proteins in the cytoplasm– which enters nucleus and binds to chromatin
Plant hormones are primarily involved in
regulation of growth
What are plant hormones produced by?
Growing parts of the plant, such as the meristematic tissues in the apical region of shoots and roots. Also produced by leaves and developing seeds
Auxins
Important class of plant hormones associated with several types of growth patterns.
What are auxins responsible for?
Phototropism: tendency of shoots of plants to bend towards the sun.
What happens when light strikes the tip of a plant from one side?
The auxin supply on that side is reduced- hence that side grows slower.
Indole-acetic acid
Example of auxin associated with phototropism
Geotropism
Growth of portions of plants toward or away from gravity.
Negative geotropism
Cause shoots to grow upward, away from acceleration of gravity.
How does negative geotropism affect auxin concentration?
Gravity increases the concentration of auxin in lower side of horizontally placed plant. Auxin on upper side decreases. Lower side elongates faster than cells on upper side, which causes plants to grow vertically.
Positive geotropism
Causes roots to grow toward the pull of gravity.
How does positive geotropism affect auxin distribution?
Horizontally placed roots have the same auxin distribution as horizontally placed stems- but the effect on the root cells in opposite.
Effect on roots cells is opposite. Cells exposed to higher concentration of auxin are inhibited from growing, whereas cells on upper side continue to grow. This causes roots to turn downward.
Auxins produced in the terminal bud of a plant’s growing tip:
move downward in the shoot and inhibit development of lateral buds
Auxins initiate the formation of _____ _____, while they inhibit ______ _______
lateral roots, root elongation
Gibberllins
Stimulate rapid stem elongation, particularly in plants that do not normally grow tall
Inhibit formation of new roots
stimulate production of new phloem cells by the cambium
terminate the dormancy of seeds and buds
How to gibberellins affect some biennial plants?
They induce them to flower during their first year of growth.
Kinins
Promote cell division
Kinetic
Important type of cytokinin
The ratio of kinetin to auxin is important for:
Determining the timing of the differentiation of new cells
The action of kinetic is ______ when auxin is present.
enhanced
Ethylene
Stimulates fruit ripening. Also induces senescence or aging.
Inhibitors
Block cell division.
Important in maintaining dormancy in the lateral buds and seeds of plants during autumn and winter
Abscisic adic
Important inhibitor
Antizuins
Regulate activity of auxins
Indoleacetic acid oxidase
Regulates the concentration of indoleacetic acid. An increase in the acid increases the about of oxidase produced.
