Endocrine Sytem Flashcards
consists of several endocrine glands and many hormone-secreting cells in organs
Endocrine System
considered to be ductless; hormone is secreted via the interstitial fluid then into the bloodstream and towards the different target organs
Endocrine glands
In contrast to the nervous system, which controls body activities through the release of neurotransmitters at synapses
Endocrine System
Functions of Hormones (5 items)
EXPLAIN
- Reproduction: can be seen in the function of ovaries and testes
- Growth and development: growth hormones are responsible for growth and development of the body
- Mobilization of body defenses: involves immune activities
- Maintenance of homeostasis
- Regulation of metabolism
T or F
Hormones affect only specific target cells that have the specific protein receptors to bind to a given hormone
Chemically, hormones are either lipid-soluble or water-soluble
True
act on receptors inside the cell which directly activate genes; affect the cell function by altering gene expression (e.g. steroid & thyroid hormones)
Lipid-soluble hormones:
alter cell function by activating the plasma membrane receptors which elicit production of a second messenger that activates various proteins inside the cell (e.g. modified amino acids, proteins, peptides; all amino acid-based hormones except thyroid hormones)
Water-soluble hormones
Mechanism of Action of Lipid-Soluble Hormones
a free lipid-soluble hormone molecule diffuses from the blood, through interstitial fluid, and through the lipid bilayer of the plasma membrane into a cell.
If the cell is a target cell, the hormone binds to and activates receptors located within the cytosol or nucleus. The activated receptor–hormone complex then alters gene expression: It turns specific genes of the nuclear DNA on or off.
As the DNA is transcribed, new messenger RNA (mRNA) forms, leaves the nucleus, and enters the cytosol. There, it directs synthesis of a new protein, often an enzyme, on the ribosomes.
The new proteins alter the cell’s activity and cause the responses typical of that hormone.
Most common stimulus
Endocrine organs are activated by other hormones
Example: Anterior pituitary hormones travel to target glands, such as the thyroid gland, to prompt the release of a particular hormone, such as thyroid hormone
Hormonal
The stimuli that activate endocrine glands fall into three major categories:
Hormonal
Humoral
Neural
Endocrine Gland Stimuli
Changing blood levels of certain ions and nutrients stimulate hormone release (Humoral indicates various body fluids, such as blood and bile)
Example:
Parathyroid hormone and calcitonin are produced in response to changing levels of blood calcium levels
Insulin is produced in response to changing levels of blood glucose levels
Humoral
Nerve impulses stimulate hormone release
Most are under the control of the sympathetic nervous system
Example: The release of norepinephrine and epinephrine by the adrenal medulla
Nerve impulses stimulate hormone release
Most are under the control of the sympathetic nervous system
Example: The release of norepinephrine and epinephrine by the adrenal medulla
secretes at least nine hormones; said to be described as a pea on a stalk; the stalk, infundibulum (pituitary stalk), connects the gland to the hypothalamus; has two major lobes
Pituitary gland (hypophysis)
composed largely of neural tissue such as pituicytes; releases neurohormones received ready-made from the hypothalamus; considered as a hormone-storage area and not a true endocrine gland that manufactures hormones
Posterior pituitary lobe (neurohypophysis)
composed of glandular tissue; manufactures and releases a number of hormones
Hormone release in the anterior pituitary gland is stimulated by releasing hormones and suppressed by inhibiting hormones from the hypothalamus
Anterior pituitary lobe (adenohypophysis)
Anterior Pituitary Gland Hormones (7)
Growth Hormone (Somatotropin)
Prolactin (PRL)’
Adrenocorticotropic Hormone (ACTH)
Thyrotropic Hormone (TH)
Follicle-Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
Melanocyte-Stimulating Hormone (MSH)
Posterior Pituitary Gland Hormones (2)
Oxytocin
ADH (Antidiuretic Hormone or Vasopressin)
It is butterfly-shaped and is located just below the larynx (voice box), conjoined with the thyroid cartilage/adam’s apple
It is butterfly-shaped and is located just below the larynx (voice box), conjoined with the thyroid cartilage/adam’s apple; it secretes the thyroid hormones:
Hormone secreted by the thyroid Gland (3)
EXPLAIN
Thyroxine (T4 or tetraiodothyronine): contains four atoms of iodine
Triiodothyronine (T3): contains 3 atoms of iodine
Calcitonin: secreted by parafollicular cells
It is composed of right and left lateral lobes, one on either side of the trachea that are connected by an isthmus
Thyroid Gland
They regulate oxygen use and metabolic rate, cellular metabolism, and growth and development
Controls the rate of oxidation of glucose
Secretion is controlled by TRH from the hypothalamus and TSH from the anterior pituitary gland
Thyroid Hormones
can lower the blood level of calcium by causing calcium deposition in the bones; its secretion is controlled by the level of calcium in the blood; an antagonistic response to the parathyroid hormone
Calcitonin
thyroid gland enlarges because of lack of iodine; salt is iodized to prevent goiters
Goiters
caused by hyposecretion of thyroxine; results in dwarfism during childhood
Cretinism
caused by hypothyroidism in adults; results in physical and mental sluggishness
Myxedema
caused by hyperthyroidism; results in increased metabolism, heat intolerance, rapid heartbeat, weight loss, and exophthalmos
Graves’ Disease:
Partially embedded in the posterior surface of the lateral lobes of the thyroid gland
Parathyroid Gland
regulates the homeostasis of calcium, magnesium, and phosphate by increasing blood calcium and magnesium levels, and by decreasing blood phosphate level
Parathyroid Hormone:
HORMONES SECRETED BY THE Parathyroid Gland
Parathormone (PTH)
LFT
LIP
RIP
RSP
Also known as suprarenal glands
Adrenal Gland
The adrenal cortex is divided into three zones:
EXPLAIN
Outer zone (zone glomerulosa): produces mineralocorticoids
Middle zone (zone fasciculata): produces glucocorticoids
Inner zone (zone reticularis): produces gonadocorticoids
Hormones of the Adrenal Cortex
Hormones of the Adrenal Cortex
Glucocorticoids
Gonadocorticoids/ Androgens
results from hyposecretion of all adrenal cortex hormones; characterized by bronze skin tone, muscle weakness, burnout, and susceptibility to infection
Addison’s Disease:
may result from an ACTH-releasing tumor; excess water and sodium are retained, leading to high blood pressure and edema
Hyperaldosteronism
results from a tumor in the middle cortical area of the adrenal cortex; manifestations include “moon face”, “buffalo hump” on the upper back, high blood pressure, hyperglycemia, weakening of bones, and depression
Cushing’s Syndrome:
results from hypersecretion of sex hormones; manifestations include beard and male distribution of hair growth
Masculinization:
Hormones of the Adrenal Medulla
Epinephrine (adrenaline)
Norepinephrine (noradrenaline)
Hormones of the Adrenal Medulla
Epinephrine (adrenaline)
Norepinephrine (noradrenaline)
Aging And The Endocrine System
Although some endocrine glands shrink as we get older, their performance may or may not be compromised.
Production of human growth hormone, thyroid hormones, cortisol, aldosterone, and estrogens decrease with advancing age.
With aging, the blood levels of PTH, TSH, LH, FSH rise.
The pancreas releases insulin more slowly with age, and receptor sensitivity to glucose declines.
After puberty, thymus size begins to decrease, and thymic tissues are replaced by adipose and areolar connective tissue.
almost any disturbance; heat or cold, environmental poisons, toxins given off by bacteria, heavy bleeding from a wound or surgery, or a strong emotional reaction
Stressor
The male gonads, the testes, are oval glands that lie inside the scrotum and produce:
Inhibin:
Testosterone:
regulates production of sperm and stimulates the development and maintenance of masculine characteristics such as beard growth and deepening of the voice
Testosterone
T or F
Female sex hormones regulate the menstrual cycle, maintain pregnancy, and prepare the mammary glands for lactation
They also help establish and maintain the feminine body shape
True
protein hormone that inhibits secretion of FSH
Inhibin
acts with estrogen to bring about the menstrual cycle;
helps in the implantation of an embryo in the uterus;
Fertilization of the egg before it is implanted in fallopian tube
helps prepare breasts for lactation
Progesterone
stimulate the development of secondary female characteristics (enlargement of breast, wider pelvis, higher pitch of voice)
Estrogen
The female gonads, the ovaries, are paired oval bodies located in the pelvic cavity and produce:
Estrogen
Progesterone
Inhibin
Located posterior to the sternum
Largest in infants and children
Produces thymosin
Matures some types of white blood cells
Important in developing the immune system
Thymus Gland
A small endocrine gland attached to the roof of the third ventricle of the brain at the midline
One hormone secreted by the pineal gland is melatonin, which contributes to setting the body’s biological clock
More melatonin is released under dim light
Higher amount of melatonin is observed in babies or children and then decreases as one ages
Pineal Gland
The pancreas is considered to be both an endocrine and exocrine gland because it secretes both hormones and digestive enzymes
The exocrine portion consists of two ducts: the duct of Wirsung and the duct of Santorini (accessory gland) (have ducts)
Pancreatic Islets
—- cells: secrete glucagon
—-cells: secrete insulin
Alpha cells: secrete glucagon
Beta cells: secrete insulin
released when blood glucose levels are high; increases rate of glucose uptake and metabolism by body cells (endocrine)
Insulin
released when blood glucose levels are low; stimulates the liver to release glucose in blood, thus increasing blood glucose levels (endocrine)
Glucagon
Secreted by the accessory pancreatic duct for digestive purposes
Pancreatic Juices (exocrine)
