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Gabriela Samson P:1 Endocrine - Coggle Diagram
Gabriela Samson P:1 Endocrine
Major functions of the endocrine system
There are specialized cells in various other organs that produce hormones, but are mainly part of other systems: liver, heart, and gastrointestinal tract
The Nervous and Endocrine Systems
Major endocrine glands include the pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, pineal gland, reproductive glands (ovaries and testes), kidneys, and thymus gland
There are similarities and differences in how the nervous and endocrine systems communicate with cells
Endocrine Glands of the Body
Both the nervous and endocrine systems are precise in their action on specific target cells
The body has 2 major types of glands, exocrine (secretes products into ducts, outside the internal environment) and endocrine (secrete hormones into body fluids to affect target cells)
The endocrine system communicates with cells using hormones (slow); the nervous system uses neurotransmitters (fast)
Certain glands secrete messenger molecules that never reach the bloodstream, so they are not true hormones; they are called “local hormones,” and include paracrine secretions (affect neighboring cells) and autocrine secretions (affect only the secretory cells)
Endocrine glands and their hormones regulate a number of
metabolic processes within cells, and the whole body
Hormones diffuse into the bloodstream to act on specific target cells some distance away
Hormone Action
Organs are not anatomically adjacent to each other
Structurally, there are 2 types of hormones:
The endocrine system is made up of cells, tissues, and organs called endocrine glands, that secrete hormones into body fluids
Steroids or steroid-like substances, which are derived from
cholesterol
The endocrine system works with the nervous system to maintain homeostasis
Nonsteroids: amines, peptides, proteins, or glycoproteins,
which are produced from amino acids
Introduction to the Endocrine System
Homeostatic mechanisms of hormone regulation (negative and positive feedback)
Posterior Pituitary Hormones 3
Oxytocin (OT):
By this mechanism, hormone levels remain fairly constant, fluctuating within a normal average range
Plays a role in childbirth by contracting muscles in the uterine wall, and in milk-letdown by forcing milk into ducts from the milk glands
When the concentration of the hormone then drops below its normal level, the inhibition is removed, and the gland begins secreting more hormone again
Stretching of the uterus in the latter stages of pregnancy
stimulates release of oxytocin
As hormone level rises, the hormone exerts its effects, further secretion is inhibited by negative feedback, and then hormone secretion decreases
Suckling of an infant at the breast stimulates release of oxytocin after childbirth
In a negative feedback system, a gland is sensitive to the concentration of the substance it regulates
Release is controlled through positive feedback
Commonly, negative feedback mechanisms control hormone release
Negative Feedback Systems
Control of Hormonal Secretions
Hormone levels are very precisely regulated
Negative feedback control mechanisms:
Release of hormones from the hypothalamus controls
secretions of the anterior pituitary, and anterior pituitary hormones affect the activity of other endocrine glands
The nervous system influences certain endocrine glands directly
Other glands respond directly to changes in the internal fluid
composition
Diseases associated with the endocrine system
Calcium Regulation and Parathyroid Disorders
Calcitonin and PTH maintain proper blood calcium concentration
Depending on cause of disease, either hypothyroidism or hyperthyroidism may lead to formation of a goiter, an enlarged thyroid that appears as a bulge in the neck
Calcitonin and PTH exert opposite effects in regulating calcium ion levels in the blood
May lead to eye protrusion (exophthalmia)
Calcitonin decreases blood calcium when it is too high
Causes high metabolic rate, restlessness, overeating in adults
PTH increases blood calcium when it is too low
Hyperthyroidism: Overactivity of the thyroid gland
Parathyroid hormone disorders:
In infants, causes cretinism: poor growth and bone formation, abnormal mental development, sluggishness
Hypoparathyroidism: deficiency of PTH, due to surgical removal or injury to glands, which results in a decrease in blood calcium
Causes low metabolic rate, fatigue and weight gain in adults
Hyperparathyroidism: excess of PTH, perhaps due to
parathyroid tumor, which results in an increase in blood calcium
Hypothyroidism: Underactivity of the thyroid gland
Thyroid Disorders
Diabetes Mellitus
A metabolic disease due to lack of insulin or the inability of cells to recognize insulin
High blood glucose harms eyes, heart, kidneys, peripheral nerves
Causes disturbances in metabolism of carbohydrates, fats, proteins
Glucose entry into body cells is impaired
Symptoms: hyperglycemia, glycosuria, polydipsia, polyphagia, acidosis
Type 1 diabetes mellitus (insulin-dependent diabetes mellitus, IDDM) is an autoimmune disorder, in which beta cells are destroyed, so insulin production decreases or stops
Type 2 diabetes mellitus (noninsulin-dependent diabetes mellitus, NIDDM) is when insulin is produced but is not recognized by cells
Compare and contrast steroid vs. non-steroid hormones and list the hormones for each
category
The hormone-receptor complex binds with the DNA and activates specific genes that, in turn, direct the synthesis of specific proteins
The new protein may function as an enzyme, transport protein, or hormone receptor; it carries out the effects of the steroid hormone
Protein receptors for steroid hormones are located inside the
target cell
Nonsteroid Hormones
Carried in the bloodstream weakly bound to plasma proteins
Nonsteroid hormones combine with receptors in target cell membranes; the receptors have a binding site and an activity site
Steroid hormones are lipid-soluble, so they can pass through cell membranes
The hormone is called the first messenger
Steroid Hormones
The chemicals in the cell that respond to binding of the hormone, and cause changes in the cell, are called second messengers
Nonsteroids: amines, peptides, proteins, or glycoproteins,
which are produced from amino acids
The cascade of biological activity through the cell membrane to the inside, beginning with the binding of the hormone, is called signal transduction
Steroids or steroid-like substances, which are derived from
cholesterol
Other proteins are activated and they carry out the effects of the hormone
Structurally, there are 2 types of hormones:
Hormone Action
Major endocrine glands/organs and their functions (separate by region/ body cavity)
Specific anterior pituitary cells are then stimulated to release or stop releasing their hormone
Posterior pituitary control:
These hormones are carried in the bloodstream directly to the anterior pituitary by hypophyseal portal veins
The posterior pituitary stores hormones made by the hypothalamus
Releasing and inhibiting hormones from the hypothalamus control the secretion from the anterior pituitary
The posterior pituitary releases these hormones into the blood in response to nerve impulses from the hypothalamus
Anterior pituitary control:
The hypothalamus controls the activity of the pituitary gland
Anterior Pituitary Hormones
Growth Hormone (GH):Stimulates body cells to grow and reproduce
Control of the Pituitary by the Hypothalamus
Speeds the rate at which cells use carbohydrates and fats
Consists of axons of neurons of the hypothalamus
Growth hormone-releasing hormone (GHRH) from the hypothalamus increases the amount of GH secreted, GH inhibiting hormone (GHIH,somatostatin) inhibits its secretion
Part of the nervous system
Nutritional status also affects the release of GH; more is released when glucose is low, or when certain amino acids increase
Posterior pituitary (posterior lobe):
GH imbalances:Pituitary dwarfism: Due to GH deficiency during childhood
Arranged around blood vessels and enclosed in a capsule of collagenous connective tissue
Gigantism: Due to GH oversecretion during childhood
Consists mostly of glandular epithelial tissue
Acromegaly: Due to GH oversecretion in adulthood
Anterior pituitary (anterior lobe):
Prolactin (PRL):Promotes milk production following the birth of an infant
The pituitary gland (hypophysis) is attached to the hypothalamus by a stalk called the infundibulum:
Controlled by prolactin releasing factor (PRF) and prolactin inhibiting hormone (PIH) from the hypothalamus
Pituitary Gland
There is no known normal physiological role in males
Major endocrine glands/organs and their functions (separate by region/ body cavity)
Neurons in the hypothalamus produce antidiuretic hormone
(ADH) and oxytocin (OT), which are stored in the posterior pituitary
Impulses from the hypothalamus release the hormones from the posterior pituitary gland
Posterior Pituitary Hormones
These hormones travel down the axons of the hypothalamus to their storage area in the posterior pituitary gland
In males, LH is also known as interstitial-cell stimulating hormone (ICSH).
Even though these 2 hormones are synthesized in the
hypothalamus, they are called posterior pituitary hormones, because they are released into the blood there
Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) affect the male (testes) and female (ovaries) gonads
Antidiuretic hormone (ADH or vasopressin):
Gonadotropins (FSH and LH):
Stress can also increase release of CRH, which increases ACTH secretion
Causes the kidneys to conserve water, and reduces amount of water excreted in the urine
The hypothalamus regulates the secretion of ADH, based on the amount of water in body fluids
Regulated by corticotropin-releasing hormone (CRH) from the hypothalamus
Osmoreceptors detect changes in osmotic pressure in body
fluids, and adjust amount of ADH secretion
Controls the secretion of certain hormones from the adrenal cortex
At high level, also causes vasoconstriction of blood vessels,
which helps to maintain blood pressure in conditions of dehydration
Adrenocorticotropic hormone (ACTH):
Diabetes insipidus is a condition resulting from insufficient ADH
As blood concentration of thyroid hormones increases, secretions of TRH and TSH decrease
Oxytocin (OT):Plays a role in childbirth by contracting muscles in the uterine wall, and in milk-letdown by forcing milk into ducts from the milk glands
Thyrotropin-releasing hormone (TRH) from the hypothalamus stimulates the release of TSH
Stretching of the uterus in the latter stages of pregnancy
stimulates release of oxytocin
Controls the secretion of hormones from the thyroid gland
Suckling of an infant at the breast stimulates release of oxytocin after childbirth
Thyroid-stimulating hormone (Thyrotropin or TSH):
Release is controlled through positive feedback