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Study Guide - Endocrine -
What type of hormone can directly bind to DNA and alter its expression (transcription of genes)?
Answer: Steroid hormones (and thyroid hormones).
Explanation: Steroid hormones are lipophilic and can pass through the cell membrane. Once inside, they bind to intracellular receptors, which can then interact with DNA to regulate gene transcription.
Phospholipase C splits PIP2 into what two chemicals?
Answer: Inositol trisphosphate (IP3) and diacylglycerol (DAG).
Explanation: Phospholipase C cleaves the membrane lipid PIP2 into two secondary messengers: IP3, which triggers calcium release from the endoplasmic reticulum, and DAG, which activates protein kinase C.
A drop in blood calcium causes the release of PTH. This would be classified as what type of stimulus?
Answer: Humoral stimulus.
Explanation: Humoral stimuli refer to changes in the blood levels of ions or nutrients that trigger hormone release. A drop in blood calcium levels is an example of this.
What is the function of phosphodiesterase?
Answer: Phosphodiesterase breaks down cyclic AMP (cAMP) into AMP.
Explanation: Phosphodiesterase deactivates cAMP, which is a secondary messenger in signal transduction, thus terminating the signal pathway.
Epinephrine and aldosterone are both released by what gland?
Answer: Adrenal gland.
Explanation: Epinephrine is released by the adrenal medulla, and aldosterone is released by the adrenal cortex, both of which are parts of the adrenal gland.
Which two hormones are released from the neurohypophysis?
Answer: Oxytocin and Antidiuretic hormone (ADH).
Explanation: The neurohypophysis, or posterior pituitary, releases oxytocin (involved in childbirth and lactation) and ADH (regulates water balance in the body).
7. Name three functions of hormones and be able to explain them.
Regulation of metabolism: Hormones like thyroid hormones control the body's metabolic rate, affecting how fast cells convert nutrients into energy.
Growth and development: Growth hormones and sex hormones regulate growth, development, and puberty. For example, growth hormone promotes bone and muscle growth.
Homeostasis: Hormones maintain a stable internal environment. For instance, insulin regulates blood sugar levels to keep them within a healthy range.
8. Name the three types of endocrine stimulation and be able to explain them.
Humoral stimuli: Hormone release is triggered by changes in blood levels of ions or nutrients. For example, a drop in blood calcium levels stimulates the release of parathyroid hormone (PTH).
Neural stimuli: Hormone release is triggered by nerve impulses. For example, the release of epinephrine from the adrenal medulla is triggered by nerve signals during stress (fight-or-flight response).
Hormonal stimuli: One hormone triggers the release of another hormone. An example is the hypothalamus releasing hormones that signal the pituitary gland to release other hormones like thyroid-stimulating hormone (TSH).
9. Explain how steroid-based hormones affect target cells.
Steroid hormones are lipophilic (fat-soluble), allowing them to pass through the cell membrane easily. Once inside the target cell, they bind to intracellular receptors in the cytoplasm or nucleus. The hormone-receptor complex then interacts with DNA, promoting or inhibiting gene transcription. This process leads to changes in protein synthesis, which can alter cell function.
10. Name the three types of hormone interaction and be able to explain them.
Synergistic interaction: Two or more hormones work together to produce a greater effect. For example, glucagon and epinephrine both increase blood glucose levels, and their combined effect is greater than if either acted alone.
Antagonistic interaction: One hormone opposes the action of another. For instance, insulin lowers blood glucose, while glucagon increases it. These hormones have opposing effects to maintain glucose homeostasis.
Permissive interaction: One hormone enhances the action of another hormone. For example, thyroid hormones are required for the full effect of growth hormone. Without thyroid hormones, growth hormone cannot exert its full action on growth.
11. Name three ways that water-soluble hormones affect target cells, and be able to explain them.
Activation of second messengers: Water-soluble hormones like adrenaline bind to receptors on the cell membrane, activating second messengers like cAMP. This cascade of signals leads to changes in the cell’s activity.
Activation of enzymes: Water-soluble hormones can activate enzymes inside the cell. For example, binding of a hormone to its receptor can activate protein kinases, which phosphorylate proteins and change their function.
Changes in gene expression (via secondary messengers): Some water-soluble hormones can initiate a signaling pathway that leads to changes in gene transcription, although they don't directly enter the nucleus. This process involves secondary messengers like IP3 or DAG.
12. Explain the difference between up-regulation and down-regulation, and be able to explain why they happen.
Up-regulation: The target cell increases the number of receptors for a hormone in response to low hormone levels or prolonged exposure to low levels. This makes the cell more sensitive to the hormone. For example, during a period of low thyroid hormone, the thyroid gland may increase the number of receptors for thyroid-stimulating hormone (TSH).
Down-regulation: The target cell decreases the number of receptors for a hormone in response to high hormone levels or prolonged exposure to high levels. This makes the cell less sensitive to the hormone. For example, if a person has chronically high levels of insulin, the body may decrease the number of insulin receptors, leading to insulin resistance.
13. Explain how hormones are moved between an endocrine gland and its target cells.
Hormones are secreted into the bloodstream and travel to target cells with specific receptors, triggering internal responses. Example: Insulin regulates glucose uptake in muscle and fat cells.
14. How does the endocrine system differ from the nervous system with respect to their target cells?
Endocrine system: Releases hormones into the bloodstream, affecting distant cells with slower, longer-lasting responses.
Nervous system: Uses electrical impulses for rapid, localized communication to specific target cells.
Diabetes mellitus is noted by sustained high blood glucose levels. Which function is most directly affected?
Answer: Homeostasis.
Explanation: Diabetes disrupts the regulation of blood glucose levels, leading to hyperglycemia due to insufficient insulin or resistance to it.
1. Explain how hormones are moved between an endocrine gland and its target cells.
Hormones are secreted into the bloodstream by endocrine glands. Once released, they travel through the blood to reach various target cells throughout the body. The target cells have specific receptors for each hormone. Hormones only affect cells that have receptors for them, allowing them to bind to the receptor and trigger a response inside the target cell. For instance, insulin from the pancreas travels through the bloodstream to muscle and fat cells, where it binds to receptors to help regulate glucose uptake.
2. How does the endocrine system differ from the nervous system with respect to their target cells?
Endocrine system: The endocrine system releases hormones into the bloodstream, which circulate throughout the body. This system typically affects target cells that are distant from the gland and the response is usually slower but longer-lasting. The hormones travel to cells that have specific receptors for them, which can be on a variety of cell types throughout the body.
Nervous system: The nervous system uses electrical impulses and neurotransmitters to transmit signals directly to target cells (usually specific cells like muscle cells or neurons). The signals are transmitted very quickly, and the responses are generally shorter-lasting compared to those of the endocrine system. The nervous system is more localized in its effect, with communication occurring between specific neurons and their target cells.
3. Diabetes mellitus is noted by sustained high blood glucose levels. Which of the four functions listed is the most directly affected?
Answer: Homeostasis.
Explanation: Diabetes mellitus primarily affects the homeostatic regulation of blood glucose levels. In a healthy individual, the body maintains a stable blood sugar level through the actions of hormones like insulin. In diabetes, either insufficient insulin is produced (Type 1) or the body's cells become resistant to insulin (Type 2), leading to an inability to regulate blood glucose levels effectively, resulting in high blood glucose (hyperglycemia).
4. What are the major endocrine organs in the human body? What are the organs (or tissues) that have another primary function and contain endocrine cells?
The major endocrine organs in the human body are:
Pituitary gland
Thyroid gland
Parathyroid glands
Adrenal glands
Pancreas
Gonads (ovaries and testes)
Organs or tissues that have another primary function but contain endocrine cells include:
Heart (secretes atrial natriuretic peptide)
Liver (produces insulin-like growth factors)
Kidneys (release erythropoietin)
Stomach and intestines (secrete various digestive hormones)
5. Adrenocorticotropic hormone (ACTH) stimulating the adrenal cortex to release cortisol is an example of ____
Answer: hormonal stimulation. This is because the release of cortisol is triggered by the action of a hormone (ACTH) on the adrenal cortex.
6. Identify which of the following hormone categories are lipid-soluble: (a) reproductive hormones produced in the gonads, (b) adrenal cortex hormones, and (c) thyroid hormone. Lipid-soluble hormones:
(a) Reproductive hormones produced in the gonads (e.g., estrogen, progesterone, and testosterone) are lipid-soluble.
(b) Adrenal cortex hormones (e.g., cortisol, aldosterone) are lipid-soluble.
(c) Thyroid hormone (e.g., thyroxine) is also lipid-soluble.
Lipid-soluble hormones can easily pass through the cell membrane because they are not charged and can diffuse through the lipid bilayer of the cell membrane.
7.The two events or processes influenced by whether a hormone is lipid-soluble or water-soluble are:
Mechanism of action: Lipid-soluble hormones can directly enter cells and bind to intracellular receptors, often influencing gene expression, while water-soluble hormones bind to receptors on the cell surface, triggering intracellular signaling pathways.
Transport in blood: Lipid-soluble hormones require carrier proteins in the blood for transport, whereas water-soluble hormones typically travel freely in the bloodstream.
8.The action of prostaglandins from damaged tissue causing smooth muscle in local blood vessels to vasodilate is an example of_____
Answer: Paracrine stimulation. Paracrine signaling refers to the action of hormones on nearby cells, and in this case, the prostaglandins affect the smooth muscle cells of the local blood vessels. Autocrine stimulation would involve the hormone acting on the same cell that secreted it, which is not the case here.
9. Why are carrier proteins necessary for lipid-soluble hormones?
Answer : Carrier proteins are necessary for lipid-soluble hormones because these hormones are not water-soluble, and therefore cannot dissolve in the blood, which is primarily water-based. Carrier proteins help transport lipid-soluble hormones through the bloodstream by binding to them and facilitating their movement to target cells.
10. What is the added benefit of a carrier protein?
Answer: The added benefit of a carrier protein is that it helps prolong the lifespan of lipid-soluble hormones in the bloodstream. Since lipid-soluble hormones are not easily broken down by water in the blood, they can remain in circulation longer when bound to a carrier protein, allowing for a more sustained effect over time.
11. What is the relationship of hormone synthesis to the concentration of that hormone in the blood?
The relationship between hormone synthesis and hormone concentration in the blood is that the rate of hormone synthesis directly influences the concentration of that hormone in the blood. When more of a hormone is produced and secreted by an endocrine organ, the concentration in the bloodstream increases. Conversely, when hormone synthesis decreases, the concentration in the blood decreases. The body's feedback mechanisms also regulate this process to maintain homeostasis, ensuring hormone levels remain within a certain range.
12. Where are lipid-soluble hormone receptors located? What is the general cellular change that occurs with binding of a lipid-soluble hormone?
Answer : Lipid-soluble hormone receptors are located inside the target cells, either in the cytoplasm or nucleus. Since lipid-soluble hormones can easily pass through the cell membrane, they bind to intracellular receptors.
The general cellular change that occurs upon the binding of a lipid-soluble hormone is that it typically results in the activation of gene expression. The hormone-receptor complex acts as a transcription factor, which binds to specific regions of DNA, causing the transcription of certain genes and leading to the synthesis of new proteins that can alter cellular activity.
13.What is the specific role of the protein kinase enzymes in the signal transduction pathway initiated by water- soluble hormones?
The specific role of protein kinase enzymes in the signal transduction pathway initiated by water-soluble hormones is to phosphorylate target proteins. This process adds phosphate groups to proteins, which can activate or deactivate these proteins, triggering various intracellular responses. Protein kinases play a crucial role in amplifying the signal within the cell and coordinating cellular changes in response to the hormone binding to its receptor on the cell surface.
14. How does down-regulation of cellular receptors change responsiveness to a given hormone?
Down-regulation of cellular receptors decreases the responsiveness of a cell to a given hormone. This occurs when a cell decreases the number of receptors available for hormone binding, often in response to prolonged or excessive hormone exposure. As a result, even if the hormone concentration remains high, the cell becomes less sensitive or responsive to the hormone, as there are fewer receptors for it to bind to.
15. What effects are seen when hormones act synergistically?
When hormones act synergistically, their combined effects are greater than the sum of their individual effects. In other words, when two or more hormones work together, they enhance each other's actions, leading to a more potent or effective response in the target cells or tissues. An example is the action of epinephrine and glucagon, which both increase blood sugar levels, and when acting together, they have an even greater effect than when acting alone.
16. What is the anatomic connection between the hypothalamus and the posterior pituitary?
The anatomic connection between the hypothalamus and the posterior pituitary is through the hypothalamo-hypophyseal tract. This is a direct neuronal connection between the hypothalamus and the posterior pituitary, allowing for the transport of hormones (such as ADH and oxytocin) that are synthesized in the hypothalamus and then stored and released from the posterior pituitary.
17. How does the hypothalamus control the release of ADH from the posterior pituitary?
The hypothalamus controls the release of ADH (antidiuretic hormone) from the posterior pituitary through neural signals. When the hypothalamus detects changes in blood osmolality (e.g., dehydration), it sends nerve impulses down the hypothalamo-hypophyseal tract to the posterior pituitary, which releases ADH into the bloodstream. ADH then acts on the kidneys to promote water retention and reduce urine output, helping to restore proper fluid balance.
18. 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 released from the anterior pituitary are:
Growth hormone (GH)
Thyroid-stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Prolactin (PRL)
Each of these hormones is regulated by the hypothalamus through releasing or inhibiting hormones:
GH: Regulated by Growth hormone-releasing hormone (GHRH) and somatostatin (inhibiting).
TSH: Regulated by thyrotropin-releasing hormone (TRH).
ACTH: Regulated by corticotropin-releasing hormone (CRH).
FSH and LH: Regulated by gonadotropin-releasing hormone (GnRH).
Prolactin: Regulated by prolactin-releasing hormone (PRH) and inhibited by dopamine.
19. How do GHRH, GH, IGFs function together to regulate growth?
GHRH (Growth Hormone-Releasing Hormone), GH (Growth Hormone), and IGFs (Insulin-like Growth Factors) function together to regulate growth by working in a sequential and synergistic manner:
GHRH from the hypothalamus stimulates the anterior pituitary to release GH.
GH then stimulates the liver and other tissues to produce IGFs, which promote growth, especially in bones and cartilage.
The IGFs stimulate cell division and differentiation, leading to overall growth and development. Additionally, IGFs play a role in metabolic processes, helping to increase protein synthesis and promote the growth of various tissues.
20. What are the primary target organs/tissues of GH and IGFs? Describe the effect on each.
GH primarily targets bones, muscles, and liver. It stimulates the growth of bones (especially long bones) and cartilage, increases protein synthesis in muscles, and encourages the liver to produce IGFs.
IGFs primarily target bones and cartilage by promoting cell proliferation and differentiation, contributing to longitudinal bone growth and the growth of other tissues like muscle and connective tissue.
21. Describe the anatomic relationship of follicular and parafollicular cells, and identify the specific hormone released by each.
The follicular cells and parafollicular cells are both found in the thyroid gland but have different locations and functions:
Follicular cells are located in the walls of the thyroid follicles, which are spherical structures in the thyroid gland. These cells produce and release thyroid hormones (T3 and T4) in response to TSH (Thyroid-stimulating hormone) from the anterior pituitary.
Parafollicular cells, also called C cells, are located in the spaces between the thyroid follicles. These cells secrete calcitonin, which helps regulate calcium levels in the blood.
22. What is the relationship of TRH, TSH, and TH in regulating metabolism?
The relationship of TRH (Thyrotropin-releasing hormone), TSH (Thyroid-stimulating hormone), and TH (Thyroid hormones) in regulating metabolism is as follows:
TRH, produced by the hypothalamus, stimulates the anterior pituitary to release TSH.
TSH then stimulates the thyroid gland to produce and release thyroid hormones (T3 and T4).
Thyroid hormones (T3 and T4) regulate metabolism by increasing the metabolic rate in tissues throughout the body. They enhance protein synthesis, increase the breakdown of fats for energy, and stimulate the generation of heat. This process is known as thermogenesis.
23. What are the primary target organs and tissues of TH? Describe the effect on each.
The primary target organs and tissues of thyroid hormones (T3 and T4) include:
Most body cells: They increase the basal metabolic rate (BMR) by stimulating mitochondria to produce more ATP, thereby increasing the overall energy expenditure and heat production.
Heart: Thyroid hormones increase heart rate and force of contraction, helping to regulate blood circulation and oxygen delivery.
Muscles: They promote protein synthesis and increase muscle growth and strength.
Liver: Thyroid hormones increase glucose production and stimulate fat metabolism.
Nervous system: They promote normal brain development and function, affecting mood and cognitive processess
24. Does calcitonin decrease or increase blood calcium? Explain.
Calcitonin decreases blood calcium levels. It does so by inhibiting osteoclast activity in bone (which would normally break down bone and release calcium into the bloodstream) and stimulating osteoblast activity, which promotes the deposition of calcium in bone. This helps to lower calcium levels in the blood, particularly in response to high blood calcium concentrations.
25. Which hormone is produced by the zona fasciculata of the adrenal cortex?
The zona fasciculata of the adrenal cortex produces cortisol, a glucocorticoid hormone involved in stress response, metabolism, and immune function regulation.
26. What is the relationship of CRH, ACTH, and cortisol?
Corticotropin-releasing hormone (CRH) is released by the hypothalamus and stimulates the pituitary gland to secrete adrenocorticotropic hormone (ACTH).
ACTH then stimulates the adrenal cortex, specifically the zona fasciculata, to release cortisol.
Cortisol acts to regulate the body's stress response, metabolism, and inflammation.This forms the HPA axis (Hypothalamic-Pituitary-Adrenal axis), and cortisol, through a negative feedback loop, inhibits CRH and ACTH production to maintain balance.
27. What are the primary target organs/tissues of cortisol? Describe the effect on each.
Liver: Stimulates gluconeogenesis (glucose production from non-carbs) and glycogen storage, increasing blood glucose levels.
Muscles: Promotes protein breakdown (catabolism), releasing amino acids for gluconeogenesis, which can result in muscle wasting with prolonged exposure.
Adipose tissue (Fat): Increases lipolysis (fat breakdown), releasing fatty acids into the bloodstream, while also promoting fat deposition, particularly in the abdominal area.
Immune System: Suppresses immune function by inhibiting pro-inflammatory cytokines and immune cell activation, reducing inflammation, but making the body more susceptible to infections with chronic high cortisol.
Bone: Inhibits bone formation (osteoblast activity) and increases bone resorption, leading to potential bone loss over time.
Kidneys: Enhances sodium retention, helping to maintain blood pressure and fluid balance.
Brain: Impacts mood and cognitive function, enhancing memory in acute stress, but prolonged high cortisol can impair memory and contribute to mood disorders such as anxiety or depression.
28. Why is the pancreas considered both an exocrine gland and an endocrine gland?
The pancreas functions as an exocrine gland by producing digestive enzymes that are secreted into the small intestine through the pancreatic duct, aiding in digestion. It also operates as an endocrine gland by releasing hormones such as insulin and glucagon directly into the bloodstream to regulate blood sugar levels.
29. Is the stimulus for insulin and glucagon release from the pancreas hormonal, humoral, or nervous?
The stimulus for insulin and glucagon release from the pancreas is considered humoral. For instance, a rise in blood glucose levels stimulates the release of insulin, whereas a drop in blood glucose levels stimulates the release of glucagon.
30. What are the stimulus, receptor, control center, and effector response to the release of insulin? Indicate what happens to nutrient levels in the blood.
Stimulus: High blood glucose levels.
Receptor: Beta cells in the pancreas detect increased glucose levels.
Control Center: Pancreas (specifically, the beta cells).
Effector Response: Release of insulin into the bloodstream.
Effect on Nutrient Levels: Insulin promotes the uptake of glucose by cells, decreases blood glucose levels, and helps store excess glucose as glycogen in the liver and muscle.
31. Which of these hormones causes release of glucose into the blood: growth hormone, thyroid hormone, cortisol, insulin, or glucagon?
Glucagon causes the release of glucose into the blood. It stimulates the liver to convert stored glycogen into glucose and release it into the bloodstream, increasing blood sugar levels.
32. How do melatonin levels change throughout the day?
Melatonin levels follow a circadian rhythm, typically increasing in the evening as it gets dark, peaking during the night (around 2-4 AM), and decreasing in the early morning as daylight approaches. This helps regulate the sleep-wake cycle by promoting sleepiness at night and wakefulness during the day.
33. What is the primary hormone released from the parathyroid gland? What is its general function?
The primary hormone released from the parathyroid glands is parathyroid hormone (PTH).
Function: PTH regulates calcium levels in the blood by increasing calcium release from bones, increasing calcium reabsorption in the kidneys, and activating vitamin D to enhance calcium absorption from the intestines. It helps maintain calcium homeostasis in the body.
34. What is the function of the kidney in regulating erythrocyte concentration within the blood?
The kidneys regulate erythrocyte (red blood cell) concentration by releasing erythropoietin (EPO) in response to low oxygen levels in the blood. EPO stimulates the bone marrow to increase the production of red blood cells, which enhances the blood's ability to carry oxygen.
35. What organ releases angiotensinogen, and what is the function of angiotensinogen following its activation?
Angiotensinogen is released by the liver.
When activated by the enzyme renin (secreted by the kidneys), angiotensinogen is converted into angiotensin I, which is further converted into angiotensin II in the lungs by the enzyme angiotensin-converting enzyme (ACE).
Function: Angiotensin II increases blood pressure by constricting blood vessels and stimulating the release of aldosterone from the adrenal glands, which promotes sodium and water retention by the kidneys, thus increasing blood volume and pressure.
36. What general changes occur to the ability of endocrine glands to produce hormones as we age?
As we age, endocrine glands often experience a decline in hormone production or a reduced responsiveness to hormones. This can lead to various age-related changes in bodily functions. Some key changes include:
Decreased production of certain hormones: For example, levels of growth hormone (GH) and sex hormones (like estrogen and testosterone) tend to decline with age, leading to changes in muscle mass, bone density, and reproductive function.
Reduced hormone sensitivity: Tissues and organs may become less responsive to hormones like insulin, leading to increased risk of conditions like type 2 diabetes.
Thyroid function: The thyroid may produce fewer hormones (like T3 and T4) with age, which can contribute to symptoms of hypothyroidism, such as fatigue and weight gain.
Adrenal function: The adrenal glands may produce less cortisol and aldosterone, which can affect the body's response to stress and fluid balance.
NoteStudied by 44 peopleNoteStudied by 8 peopleNoteStudied by 2 peopleNoteStudied by 35 peopleNoteStudied by 18 peopleNoteStudied by 19 people