Endocrine System - Hormones & Glands
Amino acid-based hormones
- Binds to a plasma membrane receptor - Acts through a second messenger such as cyclic AMP
What is involved in direct gene activation by a hormone?
1. The steroid hormone diffuses through the plasma membrane and binds to an intracellular receptor. 2. The receptor-hormone complex enters the nucleus. 3. Thus the receptor-hormone complex binds to a specific DNA region. 4. Binding initiates transcription of the gene to mRNA. 5. The mRNA directs protein synthesis.
What is a target cell?
A cell that has receptors for a particular hormone
infundibulum
A stalk that attaches the pituitary gland to the hypothalamus.
Hormones promote homeostasis by ________ of body cells rather than by _________.
Altering activity; stimulating new or unusual activity
Which hormones are produced by the hypothalamus?
Anterior Pituitary: · Thyrotropin-releasing hormone (TRH) · Gonadotropin-releasing hormone (GnRH) · Corticotropin-releasing hormone (CRH) · Growth hormone-releasing hormone (GHRH) · Prolactin-inhibiting hormone (PIH) Posterior Pituitary: · Oxytocin · Antidiuretic hormone (ADH)
The _________ is called the master endocrine gland because it regulates so many other endocrine organs. However, it is in turn controlled by _____________ secreted by the ___________. This structure identified as hypothalamus is also part of the brain, so it is appropriately called a _________ organ.
Anterior pituitary; Releasing hormones; hypothalamus; neuroendocrine
Choose the correct term. An endocrine/exocrine gland is a ductless gland that empties its hormone into the extracellular fluid.
Endocrine
Endocrine system vs Nervous Sytem
Endocrine System · Initiates responses slowly · Long-duration responses · Acts via hormones released into the blood · Acts at diffuse locations--targets can be anywhere blood reaches · Hormones act over long distances Nervous System · Initiates responses rapidly · Short-duration responses · Acts via action potentials & neurotransmitters · Acts at specific locations determined by axon pathways · Neurotransmitters act over very short distances
Aldosterone
Hormone that stimulates the kidney to retain sodium ions and water
The pituitary gland, also known as the ___________________, is located in the sella turcica of the sphenoid bone.
Hypophysis
A. Hypothalamus B. Pituitary gland C. Adrenal glands D. Ovary (female) E. Testes (male)
Label the human endocrine organs.
The secretion of most hormones is regulated by a ___________ system, in which incrasing levels of that particular hormone "turn off" its stimulus.
Negative feedback system
The various endocrine glands are prodded to release their hormones by nerve fibers (a ________ stimulus), by other hormones (a ________ stimulus), or by the presence of increased or decreased levels of various substances in the blood (a _______ stimulus).
Neural; hormonal; humoral
All cells do not respond to endocrine system stimulation. Only those that have the proper ___________ on their cell membranes are activated by the chemical messengers.
Receptors
Tropic Hormones (tropin) of Anterior Pituitary
TSH, ACTH, FSH, LH
These responsive cells are called the ___________ of the various endocrine glands.
Target cells
Steroid hormones
binds to a receptor in the cell's nucleus is lipid soluble activates a gene to transcribe messenger RNA
target cell
cells that have receptors for a particular hormone
Gonads: Ovaries
estrogen and progesterone
Norepinephrine
helps control alertness and arousal
Prehaps the reason for this is that the endocrine system uses chemical messengers, called ____________, instead of ______________. These chemical messengers enter the blood and are carried throughout the body by the activity of the _________________.
hormones; nerve impulses; cardiovascular system
sella turcica of sphenoid bone
houses the pituitary gland (hypophysis)
function of parathyroid gland
increases blood calcium level
Androgens
male sex hormones
found in the pelvic cavity of the female, concerned with ova and female hormone production
ovaries
a mixed gland, located close to the stomach and small intestine
pancreas
Choose the correct term. Pancreatic islets/ Acinar cells form the endocrine portion of the pancreas.
pancreatic islets
produces the hormones that are stored in the posterior pituitary
parathyroid gland
found in the roof of the 3rd ventricle of the brain
pineal gland
bilobed gland located in the sella turcica
pituitary gland
Major organs of the endocrine system
pituitary gland, thyroid gland, pancreas, adrenal glands, gonads, endocrine tissues in other systems
function of pituitary gland
produces hormones
Proclactin
promotes milk production
function of thyroid gland
regulates metabolism
The endocrine system is a major controlling system in the body. It means of control, however, is much ________________ than that of the _____________, the other major body system that acts to maintain homeostasis.
slower and more prolonged; nervous system
Most hormones are ________ molecules.
steroid or amino acid-based
Chemically, hormones belong chiefly to two molecular groups, the ____ and the _____
steroids and amino acids
function of posterior pituitary (neurohypophysis)
stores and releases ADH and oxytocin
Cortisol
stress hormone
paired glands suspended in the scrotum
testes
Gonads: Testes
testosterone
This gland is rather large in an infant, begins to atrophy at puberty, and is relatively inconspicuous by old age. It produces hormones that direct the maturation of T cells. It is the __________ gland.
thymus
found in the upper thorax overlying the heart; large during youth
thymus
The ______________ gland is composed of two lobes and located in the throat, just inferior to the larynx.
thyroid
located in the anterior neck; produces key hormones for metabolism
thyroid gland
What is the difference between a water soluble hormone and a lipid soluble hormone?
· A water-soluble hormone-- such as amino acids, peptides, and proteins-- cannot cross the plasma membrane. · A lipid-soluble hormone-- such as steroids--can cross the plasma membrane.
These hormones function to regulate the functions of another endocrine gland (tropic)
· ACTH · LH · FSH · ADH
Identify the 3 types of stimuli that cause hormone release and give an example for each.
· Altered levels of specific critical ions or nutrients cause humoral stimulus. Example: Cells of the PTH glands monitor the body's crucial blood Ca^2+ levels and release PTH hormone as needed. · Hormone release is caused by neural input as a result of Neural Stimulus. Example: Stress, in which the sympathetic nervous system stimulates the adrenal medulla to release norepinephrine and epinephrine. · Hormone release is caused by another hormone (a tropic hormone) = hormonal stimulus. For example, hormones released and inhibited by the hypothalamus regulate the secretion of most anterior pituitary hormones and stimulate another endocrine organ to release their hormones.
Identify 3 factors the degree of target cell activation depends on and give specific examples of each.
· Blood levels of the hormone · example: · Affinity (strength) of the binding between the hormone & the receptor · example: having a large number of high-affinity receptors produced a noticeable hormonal effect and having a small number of low-affinity receptors reduces the target cell response or causes outright endocrine dysfunction. · Relative numbers of receptors for that hormone on or in the target cells · example: progesterone down-regulates estrogen receptors in the uterus, thus antagonizing estrogens' actions. p. 608
Explain the importance of the hypothalamus to the secretions of the pituitary gland.
· By alerting the pituitary gland to release certain hormones to the rest of the endocrine system, the hypothalamus ensures that the internal processes of your body are balanced and working as they should.
Non-Tropic Hormones of the Anterior Pituitary
· Growth hormone (GH) · Prolactin (PRL)
What is the difference between a hyposecretion of a hormone and a hypersecretion of a hormone?
· Hyposecretion is the understimulated thyroid hormone · Hypersecretion is the overstimulated thyroid hormone
Pancreas
· Location: behind the stomach and close to the small intestine · function: as both endocrine and exocrine glands; produces enzymes that are important with the regulation of blood sugar levels such as insulin and glucagon
If hormones travel in the bloodstream, why don't all tissues respond to all hormones?
· Only a hormone's "target" cells, which have receptors for that hormone, will respond to its signal. · When the hormone binds to its receptor, it causes a biological response within the cell.
Epinephrine (adrenaline)
· Secreted by the adrenal medulla; · Increases heart rate and blood pressure and dilates airways (sympathomimetic). · It is part of the body's "fight or flight" reaction.
What is stress? Which part of the brain coordinates a short or long-term response to stress?
· Stress is a potential threat to homeostasis-- the body's response to nonspecific stressors. · Short-term stress = the hypothalamus activates the adrenal medulla via neural stimuli. · Example: running from a fire · Long-term stress = the hypothalamus activates the adrenal cortex via hormonal stimuli, thus continuing short-term stress response. · Example: starvation that may lead to muscle loss, altered immunity, and high blood pressure.
These hormones function to control the rate of body metabolism and cellular oxidation
· T3/T4
What is a hormone?
· a regulatory substance produced in an organism and transported in tissue fluids such as blood or sap to stimulate specific cells or tissues into action.
What is a second messenger?
· a substance whose release within a cell is promoted by a hormone and that brings about a response by the cell.
These hormones function to maintain salt and water balance in the extracellular fluid
· aldosterone · cortisol
What macromolecules make up the structure of hormones?
· amino acids · steroids
These hormones function to regulate blood calcium levels
· calcitonin (thyroid gland) · PTH (parathyroid gland)
These hormones function in which are released in response to stressors
· epinephrine (adrenal medulla) · cortisol (adrenal cortex)
These hormones function in which are directly responsible for regulation of the menstrual cycle
· estrogens · progesterone
Glucagon
· function: accelerates the breakdown of glycogen to glucose, stimulates the conversion of lactic acid into glucose, releases glucose into the blood from the liver · target: liver and adipose
Insulin
· function: accelerates the transport of glucose into body cells; promotes glycogen, fat, and protein synthesis · target: most cells of the body
T4 (thyroxine) and T3 (triiodothyronine)
· function: increases basal metabolic rate (BMR); regulates tissue growth and development · target: most cells in the body
parathyroid hormone (PTH)
· function: increases blood calcium levels by stimulating osteoclasts and by stimulating the kidneys to convert vitamin D to calcitriol, which is required for the absorption of calcium in the intestines · target: bones and kidneys
Calcitonin
· function: lower blood calicum levels by bone resorption · target: bones
Glucorticoids
· function: regulate glucose metabolism
adrenal medulla
· function: secretes epinephrine 80% and norepinephrine 20%; mimics the sympathetic nervous system; "fight or flight" response · target: most body cells
TSH (thyroid stimulating hormone)
· function: secretion of thyroid hormone T3 and T4 (anterior pituitary) · target: thyroid gland
Growth Hormone (GH)
· function: stimulates body growth and protein synthesis, mobilizes fat, and conserves glucose · target: liver, muscle, bone, and cartilage
Prolactin (PRL)
· function: stimulates milk production · target: mammary glands in breasts
Oxytocin
· function: stimulates powerful uterine contractions during birth and milk ejection in lactating mothers · target: the uterus and mammary glands
antidiuretic hormone (ADH)
· function: stimulates the kidneys to reabsorb more water, reducing urine output and conserving body water · target: kidneys
FSH (follicle stimulating hormone)
· function: stimulates the secretion of ovarian sex hormones, development of ovarian follicles, and sperm production (anterior pituitary) · target: ovaries and testes (gonads)
LH (luteinizing hormone)
· function: triggers ovulation and stimulates ovarian production of estrogen and progesterone, stimulates testosterone production (anterior pituitary) · target: ovaries and testes (gonads)
These hormones function to regulate blood glucose levels; produced by the same "mixed" gland
· glucagon · insulin
pineal gland
· located in the roof of the 3rd ventricle of the brain · endocrine product is melatonin
adrenal glands (suprarenal glands)
· location: above kidneys · function: produce hormones that help the body control blood sugar, burn protein and fat, react to stressors like a major illness or injury, and regulate blood pressure.
Thymus
· location: superior thorax, posterior to the sternum, and overlying the heart · function: produces peptide hormones such as thymulin, thymosins, and thymopoietins; which are involved in the development of T lymphocytes and the immune response
adrenal cortex
· location: the outer section of each adrenal gland; · function: secretes cortisol, aldosterone, and sex hormones
What are two systems of control for the human body?
· nervous system · endocrine system
The synthesizing gland corresponding to estrogen and progesterone is:
· ovaries
These hormones function directly involved in milk production and ejection
· oxytocin (hypothalamus) · prolactin (anterior pituitary)
The synthesizing gland corresponding to glucagon and insulin is:
· pancreas
Exocrine gland
· produce hormones · lack ducts · release hormones into tissue fluid · vascular & lymphatic drainage input
Although the pituitary gland is sometimes referred to as the master gland of the body, the hypothalamus exerts control over the pituitary gland. How does the hypothalamus control both anterior and posterior pituitary functioning?
· produces "releasing and inhibiting hormones" which control the production and release of anterior pituitary hormones; · form hormones ADH and oxytocin that are transported to the posterior pituitary and later released on nervous stimulation from the hypothalamus
function of anterior pituitary (adenohypophysis)
· produces and secretes tropic hormones: FSH, LH, ACTH, TSH, prolactin, GH, melanotropin (MSH). · "master endocrine gland" due to control of activity of many endocrine glands
Endocrine gland
· produces hormones · have ducts to carry to the surface · release their hormones directly into an extracellular fluid such as the bloodstream or lymph · example: sweat/saliva
melatonin (pineal gland)
· regulates sleep/wake cycles
Give examples of the major functions of hormones.
· reproduction = the ability to produce offspring · growth and development = produce most body's cells · maintenance of electrolyte, water, and nutrient balance of the blood = · regulation of cellular metabolism and energy balance = · mobilization of body defenses = immunity against viruses and bacteria
Hormones
· steroids or amino acid-based molecules are used to arouse the body's tissues and cells via stimulation in metabolic activity · changes lead to growth and development, homeostasis
ACTH (adrenocorticotropic hormone)
· stimulates the release of glucorticoids and androgens (anterior pituitary) · target: adernal cortex
The synthesizing gland corresponding to testosterone is:
· testes
These hormones function to drive development of secondary sex characteristics in males
· testosterone
secretion
· the substance produced by a gland