Module 4 Flashcards
Hormones play a huge role in ________.
Digestive
What is the number one killer to hormones?
Stress
The nervous system is built for speed, it uses nerve impulses to prod the muscles and glands into immediate action so that rapid adjustments can be made in response to changes occurring both inside and outside the body. On the other hand what does the endocrine system do?
It moves slowly and uses chemical messengers called hormones, which are released into the blood to be transported leisurely throughout the body.
Although hormones have widespread and varied effects, the major processes controlled by hormones are:
Reproductions, growth and development, mobilizing body defences against stressors, maintain electrolyte, water and nutrient balance of blood, regulating metabolism and energy balance.
The endocrine system regulates processes that go on for _____ ____ _______ and, in some cases ___________.
Relatively long periods, continuously
What may hormones be defined as?
A chemical substance secreted by cells into the extracellular fluids, that regulate the metabolic activity of other cells in the body.
Although many different hormones are produced, nearly all of them can be classified chemicallas as either _____ ___-____ _____ (including _______, _______, and ______) or ________.
Amino Acid-Base Molecule (protiens, peptides and amines) steroids.
If we consider the local hormones called prostaglandins we must add a third chemical class why?
Because the prostaglandins are made from highly active lipids found in the cells of plasma membranes.
Where do steroids come from?
Made by the gonads and the hormones produced by the adrenal cortex.
What needs to be in order for a target cells to respond to a hormone?
Specific protein receptors must be present on its plasma membrane or in its interior, to which that hormone can attach.
Only when binding occurs, can the hormone influence the workings of a cell. True or False
True
What do hormones do to the body? Think Greek
They arouse or bring about their effects on the body’s cells primarily by altering cellular activity, by increasing or decreasing the rate of a stimulating a new one.
The precise changes that follow hormone binding depend on the specific hormone and the target cell type, buy typically one or more of the following occurs:
- Changes in the plasma membrane permeability or electrical state
- Synthesis of proteins or certain regulatory molecules (such as enzymes) in the cell.
- Activation or inactivation of enzymes
- Stimulation or mitosis
Despite the huge variety of hormones, there are really only two mechanisms by which hormones trigger changes in cells are?
Steroidal hormones and non-steroidal hormones
Steroidal hormones, being lipid-soluble molecules, the steroid hormones can do 6 things:
- Diffuse though the plasma membranes of their target cells.
- Once inside the steroid hormone enters the nucleus.
- Binds to a specific receptor protein there.
- The hormone receptor complex then binds to specific sites on the cell’s DNA
- Then activating certain genes to transcribe mRNA (messenger RNA).
- The mRNA is translated in the cytoplasm, resulting in the synthesis of new proteins.
Non-steroidal hormones, protein and peptide hormones, are unable to enter the target cells and instead bind to receptors situated on the target cell’s plasma membrane. How does this happen? 4 spets.
- The hormone binds to the membrane receptor
- Setting off a series of reactions that activates an enzyme.
- The enzyme, in turn, catalyzes a reaction that produces a second messenger molecule.
- That oversees additional intracellular changes that promote the typical response of the target cell to the hormone.
What prompts the endocrine system to release or not to release their hormones?
Negative Feedback Mechanisms.
What are negative feedback mechanisms?
The chief means of regulating blood levels of nearly all hormones.
In such systems, hormone secretion is triggered by some internal or external stimulus; then rising hormone levels inhibit further hormone release, even while doing what? And the result is?
Promoting responses in their target organs. As a result, blood levels of many hormones vary only within a very narrow range.
The stimuli that activate the endocrine system fall into three major categories, what are they?
Hormonal, Humoral and Neural
4 points of Hormonal
- is most common
- endocrine organs are prodded into action by other hormones
- hormones produced by the final target glands increase in the blood, they “feed back” inhibit the release of anterior pituitary hormones and thus their own release
- tend to be rhythmic, with hormone blood levels rising and falling again and again
2 points of Humoral
- changing blood levels of certain ions and nutrients stimulated humoral
- chemicals or elements in the blood that simulated the endocrine glands to function.
1 point of Neural
- this is isolated cases, nerve fibres stimulate hormone releases.
All though those three mechanisms (Hormonal, humoral and neural) typify most systems that control hormone release, they by no means explain all of them, and some endocrine organs respond to many different stimuli. True or False.
True
Name as many major endocrine organs as you can, there are 9.
Pituitary, thyroid, parathyroid, adrenal, pinal, thymus glands, pancreas, gonads, hypothalamus.
Why is the hypothalamus, which is part of the nervous system, also recognized as a major endocrine organ?
Because it produces several hormones.
Although the function of some hormone-producing glands (the ____ _____, ________, _______, and __________) is purely endocrine, the function of others (______ and _______) is mixed, both endocrine and exocrine.
The anterior pituitary, thyroid, adrenals and parathyroid. Pancreas and gonads.
Both types of glands are formed from epithelial tissue, but the endocrine glands are ______ glands that produce ________ that they release into the blood or lymph.
Ductless, hormones
Where is the hypothalamus located?
The hypothalamus is a small area in the ventral diencephalon of the forebrain, in the floor of the third ventricle, and is a functional link between the nervous and endocrine system.
How does the hypothalamus control most of the endocrine glands within the body?
Largely through stimulation of the pituitary gland by secretion of neurohormones.
What is a vital regulator of homeostasis, including the thermoregulation?
Hypothalamus.
What are thermoreceptors?
Neurons in the anterior hypothalamus respond to heat by initiating peripheral vasodilation and sweating.
How do neurons in the posterior hypothalamus respond to cold?
By initiating shivering, piloerection (goosebumps) and peripheral vasoconstriction.
What are osmoreceptors?
These receptors respond to an increase in blood osmolarity by releasing Antidiuretic Hormone (ADH) from the supraoptic nucleus which is then secreted by the posterior pituitary and acts to retain water at the kidneys.
What is another thing the osmoreceptors do?
It also stimulates neurons in the thirst centre in the lateral hypothalamus in an attempt to increase water intake.
What does leptin cause?
Satiety
What does ghrelin stimulate?
Appetite
Hypothalamus What are some indirect inputs from the bloodstream include information about?
Temperature, osmotic pressure, hormone concentrations
Hypothalamus What are some indirect nerual inputs?
Uses visceral and somatic sensory neurons, the limbic system and the reticular activating system
Hypothalamus Output: Biological Clock
Light sensed by retina causes stimulation of neurons leading the suprachiasmatic nucleus which stimulates the Pineal gland as a result.
Hypothalamus Output Secretory Neurons
ADH and Oxytocin are released by the supraoptic and paraventricular nuclei cell bodies. The axons descend into the posterior pituitary gland, where they terminate in blood vessels releasing the hormone directly into circulation. Thus the posterior pituitary acts as a storage site and is not a true endocrine gland.
Hypothalamus Outputs Hypothalamic hormones
The hypothalamus releases hormones which have an activating or inhibitory effect on their target organ, hence they are named releasing or inhibitory hormones respectively.
What are some releasing hormones from the hypothalamus? There are five.
Thyrotropin Releasing Hormone (TRH) Growth Hormone Releasing Hormone (GH-RH) Gonadotropin Releasing Hormone (GnRH) Corticotrophin Releasing Hormone (CRH) Prolactin Releasing Hormone (PRL-RH)
What are some inhibitory hormones from the hypothalamus? There are three.
Growth Hormone Inhibiting Hormone aka Somatostatin (GH-IH)
Gonadotrophin Inhibiting Hormone (GnIH)
Dopamine (PRL-IH)
Where does the pituitary gland aka hypophysis sit?
It is elongated appendage of the brain lying within a bony cavity of the sphenoid bone in the base of the skull.
Where does the pituitary gland sit compared to the hypothalamus?
The hypophysis is suspended ventral to the hypothalamus by a thin infundibular stalk.
How is the pituitary gland divided?
It is divided into anterior and posterior, with different embryological origins reflecting a difference in function.
What is the anterior and the posterior gland made of?
Anterior is glandular tissue and posterior nervous tissue.
There are several anterior pituitary hormones that affect many body organs. Tell me six of them.
Two of the six - growth hormone and prolactin- exert their major effects on non-endocrine targets. The remaining four thyrotropic hormone, adrenocorticotropic hormone, and the two gonadotropic hormones are all tropic hormones.
What do tropic hormones do?
They stimulate their target organs, which are also endocrine glands, to secrete their hormones, which in turn exert their effects on other body organs and tissues.
All anterior hormones:
1) are proteins (or peptides)
2) act through second-messenger systems
3) are regulated by hormonal stimuli and, in most cases, negative feedback
Growth Hormone (GH) General Metabolic Hormone
Its major effects are directed to the growth of skeletal muscles and long bones of the body, and thus plays an important role in determining final body size. Also a polypeptide hormone
GH is a protein-sparing and anabolic hormone that causes amino acids to be built into proteins and stimulates most target cells to grow in size and divide. At the same time, it causes _____ to be broken down and used for energy, and spares ________, helping to maintain blood sugar homeostasis.
Fat, glucose
Prolactin (PRL)
Is a protein hormone structurally similar to GH. Its only target is the breast. (pro = for; lact = milk). After birthing, it stimulates and maintains milk production by the mother’s breasts. Its function in males is not known.
Adrenocorticortropic hormone (ACTH) KNOW
Polypeptide hormone made in the pituitary gland. It regulates the activity of part of the adrenal cortex, the production site of important steroid hormones that affect electrolyte and water balance and the metabolism of fats, carbohydrates and proteins.
ACTH is found in vertebrates except for _____ ____, in mammals it contains ___ ________ ____.
jawless fish, 39 amino acids
Overproduction of ACTH is one cause of ______ _______.
Cushing syndrome.
What does T3 and T4 stand for?
Triiodothyronine and thyroxine
T3 and T4: effects on ___ _____ ______ and ______ ___ ______
ALL body systems and stages of life
T3 and T4: development where thyroid hormones are vital during the ____ period and the ____ ___ ____ ______ ______
fetal, and first few months after birth
T3 and T4: also promotes ______, enhances _____ _____ uptake by tissues and enzymatic system involved in protein synthesis. Thus promoting ____ _____.
Growth, amino acid, bone growth
T3 and T4: results in increase _____ ____, increased _____ _________.
Heat production, oxygen consumption.
T3 and T4: helping in metabolic actions such as ____________ ________, as thyroid hormones stimulate glucose uptake, glycogenolysis, gluconeogensis. In fat metabolism they mobilise lipids from adipose stores and accelerate oxidation of lipids to produce _____ (occurs within _________) as well as increasing size and number of ___________.
Carbohydrate metabolism, energy, mitochondria, mitochondria
Thyroid hormones also increase basal metabolic rate (BMR) in all tissues except Brain, spleen and gonads. True or False
True
Some thyroid hormones that have a _________ ________ are to increase cardiac output, heart rate and contractility.
Cardiovascular action
How do the thyroid hormones affect the respiratory system indirectly?
By increasing BMR causing increased demand for oxygen and increased excretion of carbon dioxide.
In the nervous system what are thyroid hormones required for?
They are required for myelination of neurons during development. They also enhance the sympathetic N.S. by increasing epinephrine receptors.
Reproductive system is affected by reduced levels of thyroid hormones by causing?
Irregular cycles and decreased libido.
In the alimentary system thyroid hormones increases ______ and ______ ____, _______ of _______ ______ and increases _______.
Appetite, feed intake, secretion of pancreatic enzymes and motility.
Thyroid - Stimulating Hormone (TSH) or Thyrotropic hormone influences the _____ and ________ of the thyroid gland to release ______.
Growth and activity, thyroxine
The release of thyrotropin is triggered by the action of thyrotropin-releasing factor (TRF), a substance found in the:
Hypothalamus of the brain.
What happens if there is not enough iodine available in the diet?
There is not enough thyroxine to be made and it will shut off the release of thyrotropin.
TRF, once released from the hypothalamus, it travels in the __________ to the anterior pituitary, where it causes the release of _______. This latter substance, a ________, is carried to the thyroid gland by the blood, where it stimulates the uptake of ____, the conversion of _________ to ________, and the secretion of _________ _____ into the bloodstream.
bloodstream, thyrotropin, glycoprotein, iodine, diiodotyrosine to thyroxine, thyroid hormones
Thyroxine inhibits the further release of __________ by interfering with the action of TRF; thus levels of thyroid hormones are regulated.
Thyrotropin
Gonadotropic hormones regulate the hormonal activity of the ____.
Gonads
In mares, follicle stimulating hormone (FSH) stimulates follicle development in the ______. As the follicles mature, they produce _______, and eggs are readied for _______.
ovaries, estrogen, ovulation
In males FSH stimulates _________ ___________ by the ______.
sperm development, testes
Luteinizing Hormone (LH) triggers ______ of an egg from the female ovary and caues the ruptured follicle to become a _______ ____.
ovulation, corpus luteum
LH then stimulates the corpus luteum to produce _________ and some _________.
Progesteron, estrogen
In males LH is also referred to as _______ _____-________ _______ (_____) called this because it stimulates testosterone production by the interstitial cells of the testes.
interstitial cell-stimulating hormone (ICSH)
Hormones of the posterior pituitary, is not an _________ gland in the strict sense because it does not make the peptide hormones it releases and it simply acts as a storage area for hormones made by the __________ ________.
endocrine, hypothalamic neurons.
Oxytocin release in significant amounts only during ______ and in ______.
Childbirth and nursing
Oxytocin stimulates powerful contractions of uterine muscle during _____, _______ relations and when ______ _______. It also causes ______ _______ (______ ______).
labor, sexual, breast feeding, milk ejection, letdown reflex
Antidiuretic Hormone (ADH) is a polypeptide hormone secreted by the _______ ____ ______. Its principal action is to regulate the amount of ______ excreted by the ______.
posterior pituitary gland, water, kidneys
ADH, also known as _______, causes ______ to reabsorb water directly from the renal tubules, thus concentrating the _____ and _____ products in the liquid, which will eventually become _____.
vasopressin, kidneys, slats and waste, urine.
ADH secretion by the pituitary is regulated by neural connections from the ________, which is believed to monitor either the volume of blood passing through it or the concentration of water in the blood. ______ or _____ ____ will raise ADH secretion and water will be retained.
hypothalamus, dehydration or body stress
Despite its insignificant size, the anterior pituitary gland controls the activity of so many other endocrine glands that is has often been called the _____ ____ _______.
Master Endocrine Gland
Why is the anterior pituitary not as all powerful in its control as it might appear?
Because the release of each of its hormones is controlled by releasing and inhibiting hormones produced by the hypothalamus
The hypothalamus liberates these regulatory hormones for the posterior pituitary into the blood of the portal circulation, which connects the blood supply of the hypothalamus with that of the posterior pituitary. True or False
False anterior
What are the two additional hormones the hypothalamus makes and how are they transported?
Oxytocin and antidiuretic hormone, which are transported along the axons of the hypothalamic neuro-secretory cells to the posterior pituitary for storage. They are later released into the blood in response to nerve impulses from the hypothalamus.
Where is the thyroid gland located?
Lies in the neck, in front of the upper part of the trachea
Where are the parathyroid glands located?
They are located dorsally to or within the thyroid gland itself.
What are the two hormones the thyroid makes?
Thyroid hormone and calcitonin.
What is the thyroid hormone referred to as?
The body’s major metabolic hormone
The thyroid hormone is actually two active iodine containing hormones which are?
T4 thyroxine and T3 triiodothryonine
The thyroid hormone regulates the basal metabolic rate and is important in the regulation of ______ of ______, particularly ____ _____. Release stimulated by the TSH from the pituitary,
growth of tissues, nervous tissue
Calcitonin regulates _____ _____ _____ along with the parathyroid hormone and acts to reduce _____ ____ by inhibiting its removal from bone.
blood calcium levels, blood calcium
Thyroid Hormone controls the rate at which glucose is burned, or oxidized and converted to body heat and chemical energy. Since all body cells depend on a continuous supply of chemical energy to power their activities, meaning?
Every cell in the body is a target.
Thyroid Hormone is also important for ____ ____ _____ and _______, especially in the _______ and ________ _______.
normal tissue growth and development, reproductive and nervous system
Thyroid hormones are lipid soluble, thus need a transporting protien in order to travel in the blood. True or False
True
Half-life in the blood is _ day(s) for T3, _ day(s) for T4.
1, 6
How much percentage is the thyroid hormones in circulation are bound?
99%
What is the primary transport protein for thyroid hormones?
Thyroid binding globulin (TBG), which is synthesized in the liver, this protein bind 70-80% of the circulating thyroid hormones.
What is the remainder of thyroid hormones carried by?
Thyroxine-binding pre-albumin or albumin.
Only free T3 and T4 can enter cells to exert their actions. T4 is de-iodinated to T3 in many cells of the body, particularly the _____ and ______.
Liver and kidneys
The thyroid secretes 90% T4, with 50% of this being de-iodinated to T3. The remainder is converted to reserve T3 (rT3). This is an inactive form of T3 and so creation of its regulatory mechanism. More rT3 is created when the body needs to? Then what happens to them?
Reduce the action of T3 and T4. The hormones are further de-iodinated to diiodothyronine and mono-iodothyronine in the liver and kidneys. Iodine is recycled or excreted in the urine.
What does calcitonin or thyrocalcitonin do?
Decreases blood calcium levels by causing calcium to be deposited in the bones.
Calcitonin acts antagonistically to which hormone?
Parathyroid hormone.
Whereas thyroxine is made and stored in follicles before it is released in the blood calcitonin is made by?
Made by the so called C cells found i the connective tissue between the follicles. It is released directly to the blood in response to increasing levels of blood calcitonin production is meager to ceases in elderly adults.
How many parathyroid glands are there?
Generally four
In the horse, there are ‘nests’ of _____ ______ along the neck to the thoracic inlet.
parathyroid tissue
What does ganglion mean?
Nerves
What is an important regulator of calcium ion homeostasis for the blood?
Parathyroid Hormone
What happens when blood calcium levels drop below a certain level?
The PTH will stimulate bone destruction and release calcium into the blood
PTH is a hyper calcemic hormone (that is, it acts to increase hypo calcemic hormone. Which is the hypo calcemic hormone?
Calcitonin.
What happens when blood calcium levels fall too low?
Neurons become extremely irritable and overactive. They deliver impulses to the muscles at such a rapid rate that the muscles go into uncontrollable spasms, which may be fatal.
Where are the adrenal glands located?
They lay cranial to the kidneys within the retroperitoneal space.
Adrenal glands consist of two layers what are they?
Cortex and medulla.
The adrenal cortex is red to light brown in colour and is composed of three zones. From the outer to the inner, the layers are?
- zona glomerulosa
- zona fasciculata
- zona reticularis
The adrenal cortex produce hormones derived from __________, which is abundant in the cells. The adrenal cortex represents ___-____% of the adrenal gland.
cholesterol, 80-90%
What is the adrenal medulla primarily involved in?
Production of catecholamines; epinephrine and norepinephrine
In fetal life, which part of the adrenal plays a role in the automatic nervous system?
Medulla
The adrenal medulla acts as a ____ _____ with the _________ ____ ______ _____.
sympathetic ganglion, postganglionic cells lacking axons
