Exercise Physiology Chapter 5

The statement is true because T3, also known as triiodothyronine, is a thyroid hormone that contains three iodine atoms.

Steroid hormones are lipid soluble because they are derived from cholesterol, which is a lipid molecule. Being lipid soluble allows these hormones to easily cross cell membranes and enter target cells, where they bind to specific receptors in the cytoplasm or nucleus. This binding activates gene expression, leading to various physiological responses. The lipid solubility of steroid hormones also enables them to be stored in fatty tissues and have a longer half-life compared to water-soluble hormones.

G proteins are indeed membrane-bound proteins. They are a family of proteins involved in signal transduction pathways. These proteins are attached to the inner surface of the cell membrane and play a crucial role in transmitting signals from cell surface receptors to the inside of the cell. G proteins act as molecular switches, alternating between an inactive GDP-bound state and an active GTP-bound state. This activation allows them to interact with various downstream effector molecules and initiate intracellular signaling cascades. Therefore, the statement "G protein is a membrane-bound protein" is true.

ADH, or antidiuretic hormone, plays a role in regulating blood pressure. It does this by increasing blood volume. When ADH is released, it signals the kidneys to reabsorb water, reducing urine production and increasing the amount of fluid in the bloodstream. This increase in blood volume leads to an increase in blood pressure. Therefore, the statement that ADH can raise blood pressure by increasing blood volume is true.

Adenylyl cyclase is an enzyme that catalyzes the conversion of ATP (adenosine triphosphate) to cAMP (cyclic adenosine monophosphate). This process is known as adenylyl cyclase activation. Therefore, the statement "Activated adenylyl cyclase catalyzes the conversion of ATP to cAMP" is true.

When the plasma glucose and amino acid levels increase, the pancreas detects this and releases insulin. Insulin helps regulate blood sugar levels by allowing cells to take in glucose from the bloodstream. Therefore, an elevation in plasma glucose and amino acids will indeed increase insulin secretion to maintain proper glucose balance in the body.

Cortisol, growth hormone, and thyroxine are slow-acting hormones because they have long-lasting effects on the body and take time to produce their desired effects. These hormones are involved in various physiological processes such as metabolism, growth, and stress response, which require gradual and sustained changes rather than immediate effects. Therefore, it is true that cortisol, growth hormone, and thyroxine are slow-acting hormones.

Low levels of T3 and T4, which are thyroid hormones, can interfere with the body's ability to mobilize fuel for exercise. T3 and T4 play a crucial role in regulating metabolism, including the breakdown of carbohydrates, fats, and proteins for energy. When these hormones are low, the metabolic processes slow down, making it difficult for the body to efficiently utilize fuel during exercise. This can lead to fatigue, decreased endurance, and reduced performance. Therefore, it is true that low levels of T3 and T4 can interfere with other hormones' ability to mobilize fuel for exercise.

When epinephrine/norepinephrine binds to the beta1 receptor, it stimulates the heart to increase its rate and force of contraction. This is because the beta1 receptors are primarily located in the heart and when activated, they increase the production of cyclic adenosine monophosphate (cAMP) within the cardiac cells. This leads to an increase in calcium influx, which in turn enhances the heart's ability to contract more forcefully and at a faster rate. Therefore, the statement "If epinephrine/norepinephrine binds to the beta1 receptor, the heart rate and force of contraction increases" is true.

FFA mobilization refers to the release of free fatty acids from adipose tissue into the bloodstream. This process is dependent on the activity of hormone sensitive lipase (HSL), an enzyme that breaks down triglycerides into free fatty acids. Therefore, it is true that FFA mobilization is dependent on HSL.

When blood volume increases, there is more blood circulating in the blood vessels. This increased volume of blood puts more pressure on the walls of the blood vessels, leading to an increase in blood pressure. Therefore, increasing blood volume will indeed increase blood pressure.

Aldosterone is a hormone produced by the adrenal glands that helps regulate the balance of potassium (K+) and sodium (Na+) in the blood. When the blood potassium levels are high, it stimulates the release of aldosterone. This hormone acts on the kidneys to increase the reabsorption of sodium and the excretion of potassium, thereby helping to lower the blood potassium levels. Therefore, the statement "Stimuli for Aldosterone is high K+ in the blood" is true.

Sweat rate can indeed affect hormone concentration levels by reducing blood volume. When we sweat, we lose fluid from our bodies, which can lead to a decrease in blood volume. This decrease in blood volume can then affect the concentration of hormones in the bloodstream. Hormones are typically transported in the blood, so any changes in blood volume can impact their concentration levels. Therefore, it is true that sweat rate may affect hormone concentration levels by reducing blood volume.

T3 being more active than T4 means that T3 is more energetic, dynamic, or involved in action compared to T4. This could refer to various contexts, such as the activity levels of different thyroid hormones or the activity of different technical devices. Without further information, it is difficult to determine the exact meaning of T3 and T4 in this context. However, based on the given statement, the correct answer is True, indicating that T3 is indeed more active than T4.

Thyroid T3 (triiodothyronine) plays a crucial role in regulating metabolism, including the breakdown of fats stored in adipose tissue. Epinephrine, also known as adrenaline, is a hormone that can stimulate the release of fatty acids from adipose tissue. However, without the presence of thyroid T3, the effects of epinephrine on the mobilization of free fatty acids are significantly reduced. Therefore, it is true that without thyroid T3, epinephrine has little effect on the mobilization of free fatty acids from adipose tissue.

Non-Steroid hormones are indeed formed by amino acids. These hormones, such as insulin and glucagon, are made up of chains of amino acids. They are synthesized and released by various glands in the body, including the pancreas and the pituitary gland, and they play crucial roles in regulating various physiological processes. Unlike steroid hormones, which are derived from cholesterol, non-steroid hormones do not require any specific carrier proteins to travel through the bloodstream and exert their effects on target cells. Therefore, the given answer "True" is correct.

Growth hormone is known to increase the oxidation of free fatty acids (FFA) and gluconeogenesis in the liver. This means that it promotes the breakdown of stored fats and the production of glucose from non-carbohydrate sources in the liver. These actions help to increase the availability of energy and nutrients in the body, which is important for growth and development. Therefore, the statement that growth hormone increases FFA oxidation and gluconeogenesis in the liver is true.

Both T4 and T3 are thyroid hormones that are produced by the thyroid gland. These hormones are not soluble in water and therefore require transport proteins to be carried in the bloodstream to their target cells. These transport proteins help to bind and carry the hormones through the bloodstream, ensuring their safe delivery and effective functioning in the body. Therefore, it is true that both T4 and T3 require transport proteins for their transportation.

The rate of excretion of a hormone can serve as an indicator of the rate of secretion during exercise because when the body is engaged in physical activity, hormone production and secretion increase to support the body's energy needs. As a result, the excretion of hormones through urine or other bodily fluids can reflect the heightened secretion rate. Monitoring the rate of hormone excretion can therefore provide insights into the body's physiological response to exercise and help assess the effectiveness of training or activity levels.

Cortisol, a hormone released by the adrenal glands, is known to promote the breakdown of protein into amino acids for energy. This process, known as protein catabolism, occurs when the body needs additional energy and there is a limited supply of carbohydrates. Cortisol stimulates the enzymes responsible for breaking down proteins, allowing the body to utilize amino acids as a fuel source. Therefore, the statement that cortisol promotes the breakdown of protein to amino acids for energy is true.

Excessive water retention and dilution of sodium can lead to hyponatremia. Hyponatremia is a condition characterized by low levels of sodium in the blood. When the body retains too much water, it can dilute the sodium concentration, causing an imbalance. This can occur due to various reasons such as excessive fluid intake, certain medications, certain medical conditions, or hormonal imbalances. Hyponatremia can have serious consequences, including neurological symptoms and even coma or death in severe cases. Therefore, it is important to monitor and maintain proper sodium and fluid balance in the body.

Hypertrophy refers to the increase in size or volume of muscle cells due to an increase in the size of individual muscle fibers. This occurs as a result of resistance training or exercise, where the muscle fibers undergo microscopic damage, leading to an inflammatory response and subsequent repair and growth. The process of hypertrophy involves an increase in the number of contractile proteins within the muscle fibers, leading to an overall increase in muscle size and strength.

T3 and T4 are not pancreas hormones. They are actually thyroid hormones produced by the thyroid gland. The pancreas produces hormones such as insulin and glucagon, which are involved in regulating blood sugar levels. Therefore, the statement is false.

Insulin is a hormone produced by the pancreas that plays a crucial role in regulating blood sugar levels. One of its main functions is to promote anabolic reactions in the body. Anabolic reactions refer to the processes that build up larger molecules from smaller ones, such as the synthesis of proteins, glycogen, and fatty acids. Insulin stimulates these anabolic reactions by facilitating the uptake of glucose and amino acids into cells, promoting their conversion into larger molecules. Therefore, the given statement that "Insulin initiates anabolic reactions" is true.

The thyroid gland produces mainly T4, also known as thyroxine. T4 is the primary hormone secreted by the thyroid and plays a crucial role in regulating metabolism and growth in the body. It is converted into T3, the more active form of thyroid hormone, in various tissues. While the thyroid also produces a smaller amount of T3, T4 is the dominant hormone produced. Therefore, the statement "The thyroid produces mainly T4" is true.

An increase in the sympathetic nervous system can lead to a decrease in insulin levels. The sympathetic nervous system is responsible for the body's fight-or-flight response, which is activated during times of stress or danger. When this system is activated, it releases stress hormones such as adrenaline, which can inhibit the release of insulin. Insulin is a hormone that helps regulate blood sugar levels, so a decrease in its production can lead to higher blood sugar levels and potentially contribute to conditions such as diabetes. Therefore, the statement is true.

Training at higher altitudes can lead to an increase in the number of red blood cells. This is because when the body is exposed to lower oxygen levels at higher altitudes, it tries to compensate by producing more red blood cells. This increase in red blood cells helps to improve the oxygen-carrying capacity of the blood, allowing the body to adapt to the lower oxygen levels and perform better at higher altitudes. Hyperplasia refers to the increase in the number of cells in a tissue or organ, which is exactly what happens in this case.

Glucagon is a hormone that is responsible for increasing blood sugar levels. It stimulates the liver to convert stored glycogen into glucose and release it into the bloodstream. The correct answer is alpha cells of the pancreas because these cells are specifically responsible for producing and secreting glucagon. The pancreas contains both alpha and beta cells, but beta cells secrete insulin, which has the opposite effect of glucagon and lowers blood sugar levels.

cAMP (cyclic adenosine monophosphate) is the secondary messenger for the Adenylyl cyclase mechanism. Adenylyl cyclase is an enzyme that catalyzes the conversion of ATP to cAMP. cAMP then acts as a secondary messenger, relaying signals from various hormones and neurotransmitters to activate Protein Kinase A (PKA). PKA is responsible for phosphorylating and activating various target proteins, leading to a cascade of intracellular signaling events. Therefore, cAMP plays a crucial role in mediating the Adenylyl cyclase mechanism and transmitting signals within cells.

Constricting blood vessels and arteries actually increases blood pressure, not decreases it. When blood vessels and arteries constrict, the space for blood flow decreases, causing an increase in pressure within the vessels. This can lead to hypertension or high blood pressure. Therefore, the statement is false.

Insulin and glucagon are both required to maintain plasma glucose levels. Insulin helps to lower blood glucose levels by promoting the uptake of glucose into cells and the storage of excess glucose as glycogen. Glucagon, on the other hand, increases blood glucose levels by stimulating the breakdown of glycogen into glucose and the production of glucose by the liver. ADH (antidiuretic hormone) does not play a direct role in regulating glucose levels, but instead helps to regulate water balance in the body.

Training causes a reduction in E, NE, glucagon, and insulin responses to exercise. This means that with regular training, the body becomes more efficient at regulating these hormones during physical activity. The reduction in E and NE (epinephrine and norepinephrine) suggests that the body becomes less stressed during exercise. Additionally, the decrease in glucagon and insulin responses indicates that the body becomes better at managing blood sugar levels during exercise. Overall, this reduction in hormone responses is a positive adaptation to training and can lead to improved performance and metabolic health.

The adrenal medulla is innervated by sympathetic nerves, not parasympathetic nerves. The sympathetic nervous system is responsible for the "fight or flight" response, which involves the release of adrenaline and noradrenaline from the adrenal medulla. The parasympathetic nervous system, on the other hand, is responsible for the "rest and digest" response and does not directly innervate the adrenal medulla. Therefore, the statement that there is no parasympathetic nerve to the adrenal medulla is true.

GH stands for growth hormone, which is produced by the anterior pituitary gland. The target organ of GH is the liver. GH stimulates the liver to produce insulin-like growth factors (IGFs), particularly IGF-1. These IGFs play a crucial role in promoting growth and development in various tissues and organs throughout the body. Therefore, the liver is the main target organ for the actions of GH.

Glycogen breakdown in muscle is primarily regulated by the hormone epinephrine, which activates the cyclic AMP pathway. However, in addition to this pathway, calcium ions (CA++) and calmodulin also play a role in controlling glycogen breakdown. When calcium ions bind to calmodulin, it activates enzymes that ultimately lead to glycogen breakdown. Therefore, the correct answer is CA++ Calmodulin.

Insulin and growth hormone do not use secondary messengers. Secondary messengers are molecules that relay signals from the cell surface to the inside of the cell, amplifying and transmitting the signal. Insulin and growth hormone, on the other hand, use different mechanisms to transmit their signals. Insulin binds to insulin receptors on the cell surface, initiating a cascade of intracellular events that regulate glucose uptake. Growth hormone binds to specific receptors on target cells and activates signaling pathways directly, without the need for secondary messengers. Therefore, the correct answer is False.

Growth hormone and insulin do not have similar actions. Growth hormone is responsible for stimulating growth, cell reproduction, and regeneration in the body, while insulin helps regulate blood sugar levels by facilitating the uptake of glucose into cells. While both hormones are involved in metabolism, their actions and functions are distinct and not similar.

T4 and T3 are hormones produced by the thyroid gland, and one of their primary functions is to regulate metabolism and body temperature. These hormones play a crucial role in increasing heat production in the body, which helps to maintain a stable internal body temperature. Therefore, the statement that the primary function of T4 and T3 is heat production is true.

Insulin and GH both use the mechanism of tyrosine kinase. Tyrosine kinase is an enzyme that adds a phosphate group to tyrosine residues in proteins. This mechanism is essential for the signaling pathways of insulin and GH, as it allows for the activation of downstream signaling molecules and the regulation of various cellular processes. By utilizing tyrosine kinase, insulin and GH are able to exert their effects on glucose metabolism, growth, and other physiological functions.

A false statement about the stimuli to release epinephrine is that it is caused by para-sympathetic nerves. Epinephrine is typically released in response to exercise, mental stress, and hypoglycemia, but not through para-sympathetic nerves. The release of epinephrine is primarily regulated by the sympathetic nervous system, which is responsible for activating the body's fight-or-flight response.

Aldosterone is not a glucocorticoid. It is a mineralocorticoid hormone that is produced by the adrenal glands. Glucocorticoids, on the other hand, are a class of steroid hormones that are involved in various metabolic processes and have anti-inflammatory effects. While aldosterone and glucocorticoids are both produced by the adrenal glands, they have different functions and effects in the body. Therefore, the statement that aldosterone is a glucocorticoid is false.

Hypersecretion of cortisol can lead to muscle breakdown, Cushing's disease, and bone breakdown. However, it does not lead to hypoglycemia. Cortisol is a hormone that helps regulate blood sugar levels, and hypersecretion of cortisol actually leads to hyperglycemia, or high blood sugar levels. Hypoglycemia, on the other hand, is characterized by low blood sugar levels, which is not caused by excessive cortisol production.

During exercise at 60% VO2max, the body's demand for energy increases. This leads to an increase in growth hormone secretion, as growth hormone helps to mobilize stored energy sources such as fat. At the same time, insulin levels decrease because insulin promotes the uptake and storage of glucose, which is not the body's preferred fuel source during exercise. Therefore, growth hormone increases while insulin decreases to facilitate the utilization of stored energy and promote the breakdown of fats for fuel.

A low ratio of insulin and glucagon means that the level of insulin is lower compared to glucagon. Insulin promotes anabolic reactions, which are processes that build up molecules and store energy. On the other hand, glucagon promotes catabolic reactions, which involve the breakdown of molecules to release energy. Therefore, a low ratio of insulin and glucagon would favor catabolic reactions, indicating that the body is more focused on breaking down molecules and releasing energy rather than storing it.

T3 and T4 are needed for all the above functions. T3 and T4, also known as triiodothyronine and thyroxine respectively, are hormones produced by the thyroid gland. They play a crucial role in regulating the body's metabolism, including the normal function of growth hormone (GH), lipid synthesis, and oxygen consumption. Therefore, all the options mentioned in the question are correct, as T3 and T4 are required for all of these functions.

GLUT4 is the correct answer because in the Tyrosine mechanism, glucose enters the cell through the GLUT4 transporter. GLUT4 is a glucose transporter protein that is mainly found in adipose tissue and skeletal muscle. It is responsible for insulin-regulated glucose uptake into these cells. When insulin is present, it activates the Tyrosine Kinase receptor, which then triggers the translocation of GLUT4 from intracellular vesicles to the cell membrane, allowing glucose to enter the cell. This process helps regulate blood glucose levels and is important for maintaining normal glucose homeostasis.

The adrenal cortex secretes mineralocorticoids and glucocorticoids. Mineralocorticoids, such as aldosterone, regulate electrolyte and water balance in the body. Glucocorticoids, such as cortisol, regulate metabolism, immune responses, and stress responses. Therefore, the correct answer is B and C.

The anterior pituitary gland secretes six hormones. These hormones include growth hormone (GH), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL). Each of these hormones plays a crucial role in regulating various functions in the body, such as growth, metabolism, reproduction, and lactation.

Glucagon is a hormone released by the pancreas that increases plasma fuel levels, particularly glucose. It does this by stimulating the breakdown of glycogen into glucose in the liver, and by promoting the release of glucose into the bloodstream. Therefore, the statement that glucagon will decrease plasma fuel levels is incorrect.

The adrenal medulla secretes 80% epinephrine and 20% norepinephrine, not 70% epinephrine and 30% norepinephrine.