A&P Ch 17

You may have heard someone describe a teenager going through puberty as having "thinned out." Which cellular process stimulated by GH directly accounts for the loss of fat tissue: glycogenolysis, lipolysis, or protein anabolism.

Increased lipolysis is caused by growth hormone. This results in loss of stored adipose connective tissue and the "thinning out" experience by many during puberty.

Blood samples from a young woman named Michelle indicate an elevated blood glucose level. This homeostatic imbalance is most likely caused by an insufficient amount or decreased sensitivity to which hormone?

Insulin

What is the relationship of hormone synthesis to the concentration of that hormone in the blood?

When hormone synthesis and release increase, the concentration of hormone in the blood increases. When hormone synthesis and release decrease, the concentration of hormone in the blood decreases.

What is the relationship of CRH, ACTH, and cortisol?

A decrease in cortisol stimulates the hypothalamus to produce and release CRH along the hypothalamo-hypophsyeal tract, then the anterior pituitary is stimulated to produce and release ACTH which then travels by carrier protein to the adrenal glands where ACTH binds within the zona fasciculata of the adrenal cortex to produce cortisol.

How does the hypothalamus control the release of ADH from the posterior pituitary?

A nerve signal is sent from the hypothalamus along the hypothalamo-hypophyseal tract from the paraventricle nucleus causing the release of ADH.

What is the anatomic connection between the hypothalamus and the posterior pituitary?

Axons from groups of neurons extend from the hypothalamus to the posterior pituitary (specifically the pars nervosa). The dendrites and cell bodies of these neurons are within the hypothalamus. Unmyelinated axons from these neurons extend through the infundibulum as the hypothalamo-hypophyseal tract (which includes synaptic knobs) within the posterior pituitary. It is inferior to the hypothalamus.

Is the stimulus for insulin and glucagon release from the pancreas hormonal, humoral, or nervous?

Hormonal; Hormone is released in response to the hormone level in the blood

What effects are seen when hormones act synergistically?

Hormones work together to create a greater effect.

Where are lipid-soluble hormone receptors located? What is the general cellular change that occurs with binding of a lipid-soluble hormone?

Lipid-soluble hormone receptors are located intracellularly (in the cytosol or nuclei). Changes occur at a cellular level due to the binding at the receptor, creating a hormone receptor complex, which binds to DNA which transcribes mRNA causing a change in the cell structure and ultimately synthesis a specific protein. If an enzyme, there is a shift in cell activity.

Why are carrier proteins necessary for lipid-soluble hormones?

Lipid-soluble hormones cannot readily dissolve in the aqueous environment of the blood, and therefore, need transport (the carrier protein) to their target cell.

Describe how local hormones differ from circulating hormones

Local hormones differ from circulating hormones in that they are produced by and bind in the area where they were produced (autocrine) or nearby where they were produced (paracrine). These hormones do not enter the blood. Circulating hormones enter the blood and are transported throughout the body.

How do melatonin levels change throughout the day?

Melatonin production is cyclic. It increases at night, decreases during the day, and is at its lowest around lunchtime.

What is the added benefit of a carrier protein?

The carrier protein acts as a safeguard for the lipid-soluble hormone, preventing damage and prolonging the life of the hormone.

How does down-regulation of cellular receptors change responsiveness to a given hormone?

The number of receptor molecules available for hormone binding directly influences the degree of cellular response to that hormone. Down-regulation reduces the cell's sensitivity to the hormone.

Susan is a 35 yr. old mother of two who works an an admissions officer at the university. Consider the potential challenges she may experience by listing the hormones released by both the posterior pituitary and the anterior pituitary.

The posterior pituitary gland releases oxytocin and antidiuretic hormone. The anterior pituitary releases the trophic hormones: thyroid-stimulating hormone, adrenocorticotropic hormone, growth hormone, luteinizing hormone, follicle-stimulating hormone, and prolactin. All of the processes regulated by these hormones would be affected.

All of the following hormones are released from the hypothalamus to control the anterior pituitary gland except a) GRH b) ADH c) PRG d) CRH

b) ADH

Which of the following are components of intracellular enzyme cascades initiated by water-soluble hormones? a) G proteins b) cAMP c) protein kinase enzymes d) all of them

d) all of them

Which of the following is not a general process controlled by the endocrine system? a) development, growth, and metabolism b) control of reproductive activities c) maintenance of homeostasis of blood composition d) programmed cell death/destruction of aged cells

d) programmed cell death/destruction of aged cells

Glucocorticoids (eg cortisol) are produced in the adrenal cortex to help regulate

glucose levels in the blood

Predict the signs/symptoms that a person with hyperthyroidism would exhibit in each of the following circumstances: (a) high temperature or low temperature (b) elevated pulse or decrease pulse (c) elevated breathing or decreased breathing and (d) plump or thin body

(a) high temperature (b) elevated pulse (c) elevated breathing (d) thin body A person with hypothyroidism will exhibit these symptoms because their body has increase its metabolic rate past the point of homeostasis and is being overworked.

Which of these hormones causes release of glucose into the blood: growth hormone, thyroid hormone, cortisol, insulin, or glucagon?

Growth hormone, thyroid hormone, cortisol and glucagon all cause the release of glucose into the blood.

Identify which of the following hormone categories is lipid soluble (a) reproductive hormones produced in the gonads (b) adrenal cortex hormones (c) thyroid hormone.

Reproductive hormones produced in the gonads (steroids), hormones from the adrenal cortex (steroids), and thyroid hormones (biogenic amines) are all lipid-soluble.

What two events or processes associated with a hormone are influenced by whether a hormone is lipid-soluble or water-soluble?

Solubility is influenced by transport of the hormone in the blood and how it interacts with its target cells.

What two events or processes associated with a hormone are influenced by whether a hormone is lipid-soluble or water-soluble?

Solubility is influenced by transport of the hormone in the blood and how it interacts with target cells.

Diabetes mellitus is noted by sustained high blood glucose levels. Which of the four function of the endocrine system is the most directly affected?

maintain homeostasis of blood composition and volume

George is a 43-year-old construction worker who has developed a swelling in his neck that is painful and continues to grow. He visited the doctor and confided to his clinician that he has also lost weight and has becomes very hyperactive. What gland does the clinician suspect is functioning abnormally?

thyroid

TSH stimulate the

thyroid gland to release its hormone

This hormone's primary function is to regulate metabolism

thyroid hormone (TH)

Hormones released from the anterior pituitary are

GH, PRL, TSH, FSH, LH, ACTH

What are the primary target organs/tissues of TH? Describe the effect on each.

TH travels to all cell especially neurons. This increases metabolic rate and increases the uptake of glucose. TH travels to the liver where it increases glycogenolysis and gluconeogenesis and decreases glycogenesis. TH travels to adipose connective tissues increasing lipolysis and decreases lipogenesis. TH travels to the lungs and heart to increase breathing rate, heart rate, and force of contraction. Overall metabolic rate is increased which is supported by the increased release of stored nutrient molecules and increased delivery of oxygen.

What is the specific role of the protein kinase enzymes in the signal transduction pathway initiated by water-soluble hormone?

The activation of protein kinase enzymes results in the phosphorylation of other molecules which either activates or inactivates those molecules.

What organ releases angiotensinogen, and what is the function of angiotensinogen following its activation?

The liver releases angiotensinogen. It is an inactive hormone that is activated while circulating within the blood. Its effects are meant to work together to keep blood pressure within normal homeostatic limits; these effects are: (1) it constricts blood vessels, (2) it stimulates the thirst center, and (3) it stimulates the kidney to decrease urine output.

Why is the pancreas considered both an exocrine and endocrine gland?

The pancreas has both endocrine and exocrine functions. However, the primary function of the pancreas is not endocrine in nature, therefore, it is considered a mixed gland or endocrine cell. Only one percent of the pancreas is for endocrine function, and the other 99% is for acini cells which facilitate digestion.

After seeing a physician for a sudden weight loss, 19 yr. old Harold is diagnosed with type 1 diabetes, which is a condition in which the beta cells of the pancreas are producing insufficient amounts of insulin or target cells not responding to insulin. Explain to Harold why results from his blood lab report indicate that he has an elevated blood glucose level.

Type I diabetes results in diminished insulin release from beta cells of the pancreas. Insulin is required to stimulate cells of the body to take up glucose, thereby lowering blood glucose levels. Elevated blood glucose levels suggest that adequate levels of insulin are not being produced.

Jelena is late for work and is rushing to get out the door. Her commute to work is slow due to rush-hour traffic, and she begins to become anxious and upset. As she is attempting to park, someone hits her car and she becomes angry. What specific hormones are released during this "emergency"?

epinephrine/cortisol

Insulin increases _______ within hepatocytes to decrease blood glucose.

glycogenesis (Glycogenesis is the synthesis of glycogen from glucose obtained from the blood.)

Adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex to release cortisol hormone. This is an example of what type of stimulation?

hormonal stimulation

What general changes occur to the ability of endocrine glands to produce hormones as we age?

Aging reduces the efficiency of endocrine system functions, and often levels of hormones decrease.

Explain how the hypothalamus oversees and controls endocrine system function of the posterior pituitary.

Axons from groups of neurons extend from the hypothalamus to the posterior pituitary. The dendrites andvcell bodies of these neurons are within the hypothalamus. Unmyelinated axons from these neurons extend through the infundibulum as the hypothalamo-hypophyseal tract. The ends of these axons are located within the pars nervosa. The posterior pituitary stores hormones synthesized in the hypothalamus. The posterior pituitary is stimulated to release either antidiuretic hormone (ADH) or oxytocin in response to nerve signals initiated in the hypothalamus and conducted to the posterior pituitary along the hypothalamo-hypophyseal tract.

Discuss the homeostatic system involving insulin.

Beta cells in the pancreas detect increased levels of blood glucose and respond by releasing insulin. Insulin stimulates target cells to decrease all nutrients (glucose, fatty acids, and amino acids) in the blood and an increase in the synthesis of the storage of these molecules within body tissues. (a) Glycogenesis in hepatocytes is stimulated and both glycogenolysis and gluconeogenesis are inhibited, resulting in glucose molecules being removed from the blood and stored as glycogen within liver cells. (b) Lipogenesis in adipose connective tissue cells is stimulated and lipolysis is inhibited. Fatty acid levels in the 89 blood decrease and the storage of fat is increased as a result. (c) Most cells are stimulated to increase their cellular uptake of (1) amino acids (especially muscle cells), a change that induces cells to increase protein anabolism (synthesis of amino acids into protein), and (2) glucose, especially by the cells of muscle and adipose connective tissue. By decreasing alternative nutrients (fatty acids and amino acids), the cells of the body are more likely to use the available glucose and help return blood glucose to a normal level more quickly. The release of insulin is controlled by negative feedback; as blood glucose levels decrease, less insulin is released from the pancreas.

Identify the three chemical classes of hormones, and give an example of each. Most hormones belong to which class?

Biogenic amines - water-soluble hormones (except for thyroid hormones) derived from modified amino acids Proteins (most hormones) - water-soluble hormones formed from amino acids chains; three subgroups - small peptides, large polypeptides, glycoproteins Steroids - lipid-soluble hormones formed from cholesterol

Explain the function of carrier proteins in transporting lipid-soluble hormones in the blood, and how these hormones interact with cells.

Carrier proteins act as hormone safeguards. The job of a carrier protein is to transport a lipid-soluble hormone from one location of the body to another. This transport helps to prevent damage and prolong the life of the hormone in which it is carrying. Lipid-soluble hormones are able to transverse the cell membrane of a cell and then they bind to a receptor inside the cell. They then cross through the cytoplasma on another transport and are transported to the nucleus where they will attach to DNA and are transcribed by mRNA to make a change at a cellular level. The mRNA synthesis a specific protein.

What are the primary target organs/tissues of cortisol? Describe the effect on each.

Effectors of cortisol: liver → increased glycogenolysis and glyconeogenesis and decreased glycogenesis; adipose connective tissue → increased lipolysis and decreased lipogenesis; all cells → stimulation of protein catabolism (occurs in all cells except heptocyctes) and decrease glucose uptake; high does of cortisol increases Na and H20 retention, decreases inflammation, suppresses the immune system and inhibits connective tissue repair. Overall effect of homeostatic cortisol release is increase of all nutrient molecules in blood.

Body builders have been known to inject insulin to increase muscle bulk. Explain their reasoning. What is the risk of an insulin overdose?

Elevated insulin levels typically results in decreased levels of all nutrients in the blood and an increase in the storage form of these molecules within the cells of the body. Thus, elevated serum insulin leads to protein anabolism in the muscle cells, resulting in increased muscle bulk. An insulin overdose may lead to dangerously low serum glucose levels and ATP levels. If ATP cannot be generated at the rate needed, death could result. It also can result in a potassium imbalance.

What are the major endocrine organs in the human body? What are the organs (or tissues) that have another primary function and continue endocrine cells?

Endocrine Organs: thyroid, pituitary gland, adrenal glands, parathyroid glands, pineal gland Endocrine Cells: (Kitty the hungry hippo skips and sings playing lovely sweet games.) kidneys, thymus, hypothalamus, stomach, adipose connective tissue, small intestine, pancreas, liver, skin, gonads

How do GHRH, GH, and IGFs function together to regulate growth hormone?

GHRH, GH, and IGFs work synergistically by GHRH being released from the hypothalamus, traveling through the hypothalamo-hypophyseal tract to the anterior pituitary to release GH which travels to the liver to bind and release IGFs. GH and IGFs both stimulate cell growth and division within the skeletal and muscular systems. Both are regulated by negative feedback. In response to increased GH and IGFs, the hypothalamus is stimulated to release GHIH. GH can also directly inhibit its own release from the anterior pituitary.

Explain the three mechanisms used to stimulate hormone release from a target cell to initiate an endocrine reflex.

Hormonal stimulation - the secretion of a hormone is stimulate by another hormone (example: TSH stimulated the release of TH) Humoral stimulation - the secretion of a hormone is stimulated in response to a changing level of nutrient molecule or ions (example: the release of glucagon or insulin) Nervous system stimulation - a few endocrine glands are stimulated to release hormone by direct stimulation of the nervous system (example: the adrenal glands stimulated to release epinephrine)

Explain how the hypothalamus oversees and control endocrine system function of the anterior pituitary.

Hormones produced in the hypothalamus are transported through the hypothalamo-hypophyseal portal system to the anterior pituitary gland. Those hormones stimulate specific cells of the anterior pituitary to release their hormones into the general circulation.

What cellular response (up-regulation or down-regulation) would you predict occurs in response to high doses of a drug that binds to a specific hormone receptor? Will more or less of the drug be required for the same response over time? Explain

If a drug binds to a specific hormone receptor of a cell to initiate its affect, the cell will down-regulate receptors. (It's saying, "hey body, I'm here; I have enough; I don't need all these receptors.") Over time, more of the drug will be required for the same response.

What effect would impaired function of the liver or kidneys potentially have on hormone concentration in the blood?

Malfunction of the liver and kidneys can result in an imbalance of hormones within the blood. One would predict an increase in blood concentration of a hormone given the role of the liver and kidneys in eliminating hormones, wastes, and other metabolites. However, if the malfunction was that the liver and kidneys were eliminating too quickly or too much, the concentration of hormone in the blood would be lower.

What is the relationship of TRH, TSH, and TH in regulating metabolism?

TRH is produced in the hypothalamus and travels through the hypothalamo-hypophyseal tract to the anterior pituitary where it is stimulated to permissively release TSH. TSH then moves to the thyroid where it binds with thyroid follicular cells within the gland (lipid-soluble) permitting the release of TH. TH then stimulates target cells.

Henry is a well-informed patient who is interested in understanding how thyroid hormone is controlled by thyrotropin-releasing hormone and TSH. Briefly explain to him the hypothalamic-pituitary-thyroid axis.

TRH is produced in the hypothyalamus when the body detects that more thyroid hormone is needed. TRH travels the hypothalamo-hypophyseal tract into the anterior pituitary which detects TRH and releases TSH. TSH travels to the thyroid where it stimulates the production and release of TH which travels to specific target cells. Controlled by negative feedback.

How does the endocrine system differ from the nervous system with respect to their target cells?

The endocrine system communicates information from specific part of the body to another through hormones while the nervous system uses neurons.

List the four primary functions of the endocrine system.

The endocrine system is responsible for maintaining the body's growth, development, and metabolic rates, maintaining the volume and composition of blood, regulating the reproductive system, and controlling digestive processes.

Describe similarities and differences between the endocrine system and the nervous system in their method of operation and effects.

The nervous system and endocrine system work together, both, responding to stimuli. The nervous and endocrine systems are both responsible for communicating between one area of the body to another. They are also both responsible for reflexes in the body and both bind to cellular receptors in/on target cells to initiate a change. The nervous system exercises control through neurons. The nervous system is a quick, short localized response with short-lived effects while the endocrine system response is widespread and long-lasting. The nervous system uses neurotransmitters, and the endocrine system uses hormone secretion.

What is the primary hormone released from the parathyroid gland? What is its general function?

The primary function of the parathyroid gland is to increase blood calcium. The main hormone is the parathyroid hormone (PTH).

What are the primary target organs/tissues of GH and IGFs? Describe the effect on each.

The primary target organs/tissues are the in the skeletal and muscular systems. They stimulate cell growth and division. GH and IGFs have overlapping functions and all body cells have receptors for them. Binding of the hormones activates second messengers within the target cells, altering enzymatic pathways to increase protein synthesis, mitosis, cell differentiation, or a combination of these. Bone and muscle tissue are particularly affected by these hormones. Hepatocytes are also stimulated by GH to increase both glycogenolysis and gluconeogenesis while at the same time glycogenesis is inhibited.

What are the six primary hormones released from the anterior pituitary? How is the release of each of these hormones regulated by the hypothalamus?

The six primary hormones are: TSH, ACTH, FSH, LH, PRL, GH They are regulated through hormonal stimulation and permissively. The release of hormones by the anterior pituitary is controlled by the releasing of hormones (releasing or inhibiting) in the hypothalamus. Releasing hormones: TRH→TSH; GnRH→FSH and LH; GHRH→GH; CRH→ACTH; PRH→PRL

What is the stimulus, receptor, control center, and effector response to the release of insulin? Indicate what happens to nutrient levels in the blood.

The stimulus is a decrease in blood glucose levels regulated by negative feedback. The alpha cells within the pancreas detect a decrease in blood glucose levels and release glucagon which stimulates the target cells. Glucagon effects the liver by increasing glycogenolysis and gluconeogenesis and decreasing glycogenesis and adipose connective tissue by increasing lipolysis and decreasing lipogenesis. The net effect is that blood glucose and fatty acid levels are increased.

Describe how water soluble hormones interact with cells.

Water-soluble hormones (polar molecules) cannot enter the cell. These hormones must bind to a receptor on the extracellular surface of the membrane, which will transduce the stimulus into the cell and result in the activation of a second messenger system. Formation of second and third messengers (e.g., cAMP, DAG, IP3, Ca2+) either alter protein kinase activity, change a cell's permeability to ions, or both. Ultimately, the action may result in either activation or inhibition of enzymatic pathways, stimulation of growth through cellular division, release of cellular secretions, changes in membrane permeability, and muscle contraction or relaxation.

What is the function of the kidney in the amount of erythrocytes circulating in the blood?

When chemoreceptors within the kidney detect low blood oxygen levels, endocrine tissue within the kidney releases erythropoietin (EPO). This hormone stimulates red bone marrow to increase the production rate of red blood cells.

Have you ever noticed that the salt you buy in the grocery store is "iodized"? What is the function of iodine added to our salt?

Yes, I have. The function is to provide support for the thyroid since the body cannot produce its own iodine; iodine is needed for thyroid hormone synthesis. Iodine is needed to convert T4 to T3.

Glucagon has an _______ effect to insulin on target cells.

antagonistic

The action of water-soluble hormones may include all of the following except a) activation or inhibition of enzymatic pathways b) bind with a hormone responsive element c) muscle contraction or relaxation d) stimulation of cellular secretions

b) bind with a hormone responsive element lipid-soluble hormones bind with intracellular receptors to form hormone-receptor complex, which binds with hormone-responsive elements (components of the DNA).

Stephen is taking a new weight-loss supplement that is known to not only decrease the amount of adipose connective tissue (as advertised) but to also decrease glycogen stores in the liver and causes breakdown of muscle protein (protein catabolism) What substance in this weight-loss supplement is responsible for these changes?

cortisol Cortisol stimulates gluconeogenesis in the liver, and lipolysis in adipocytes. It also causes protein catabolism and release of amino acids from all other tissues.

What is the best diagnostic test to determine if this gland is not function normally?

measuring the amount of radioactive iodine taken up by the thyroid

Leukotrienes from damaged tissue cause smooth muscle in local blood vessels to vasodilate is an example of _________.

paracrine stimulation