Human Physiology: Hormones and Enzymes

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Questions and Answers

What is one of the primary ways hormones increase enzyme activity?

Inhibiting enzyme production

Stimulating enzyme production (correct)

Increasing the size of the enzyme

Decreasing enzyme stability

Which factor does NOT determine hormone levels in the plasma?

Plasma volume changes

Presence of specific vitamins (correct)

Quantity synthesized in host gland

Catabolism or secretion rate into the blood

How does growth hormone (GH) affect carbohydrate metabolism?

Eliminates carbohydrate usage

Slows carbohydrate breakdown (correct)

Initiates carbohydrate synthesis

Increases carbohydrate breakdown

What impact does increased physical activity have on growth hormone secretion?

Stimulates a rise in GH pulse amplitude Signup and view all the answers

Which of the following is a direct action of growth hormone?

Promotes cell division and cellular proliferation Signup and view all the answers

What is NOT a way hormones alter enzyme activity?

Changing enzyme's reaction environment Signup and view all the answers

Which statement correctly describes the relationship between exercise and GH levels in individuals of varying fitness levels?

Both trained and sedentary individuals increase GH concentration with exhaustive exercise Signup and view all the answers

What is one of the roles of growth hormone in terms of protein metabolism?

Stimulates RNA formation Signup and view all the answers

What is the primary function of aldosterone?

Regulates mineral balance in extracellular fluids Signup and view all the answers

Which type of cells in the islets of Langerhans secrete glucagon?

α-cells Signup and view all the answers

Which effect does cortisol NOT have on metabolism?

Increases calcium absorption in the bones Signup and view all the answers

What is the role of catecholamines during increasing intensity cycling?

Stimulate substrate mobilization for energy Signup and view all the answers

What majority percentage of mineralocorticoids is represented by aldosterone?

95% Signup and view all the answers

Following a meal, how does insulin affect blood glucose levels?

Decreases blood glucose levels Signup and view all the answers

What change occurs in Antidiuretic Hormone (ADH) levels with training?

ADH concentration decreases Signup and view all the answers

Which of the following is NOT a function of glucocorticoids like cortisol?

Promoting immune system function Signup and view all the answers

How does training affect plasma cortisol levels during submaximal exercise?

Plasma cortisol levels decrease less in trained individuals Signup and view all the answers

Which of the following hormones is primarily responsible for stimulating sodium ion reabsorption in the kidneys?

Aldosterone Signup and view all the answers

Which hormones are affected by adaptations during exercise training?

Adrenal hormones affecting muscle mass and fatigue resistance Signup and view all the answers

What is the outcome of sympathoadrenal activity in trained individuals compared to untrained during submaximal exercise?

Lower in trained individuals Signup and view all the answers

Which factor does NOT contribute to greater catecholamine output post-training?

Lower substrate demand Signup and view all the answers

How does endurance training influence blood glucose levels during physical activity?

Keeps insulin and glucagon levels closer to resting levels Signup and view all the answers

Which of the following is NOT considered a possible cause of insulin resistance?

Increased insulin release Signup and view all the answers

What is the main action of glucagon in the body?

Stimulates glycogenolysis and gluconeogenesis Signup and view all the answers

What effect does exercise training have on the renin-angiotensin-aldosterone system at rest?

It has no effect on resting levels Signup and view all the answers

How does exercise training affect the hormonal response during physical activity?

It leads to improved target tissue sensitivity Signup and view all the answers

Which of the following is a training adaptation related to adrenal hormone effects?

Increased systemic glucose disposal Signup and view all the answers

Which statement is true regarding growth hormone (GH) and exercise?

Endurance-trained individuals have a lesser rise in GH at the same intensity Signup and view all the answers

What mainly controls the secretion of glucagon?

Plasma glucose concentration Signup and view all the answers

How does exercise training influence thyroid hormone turnover?

Increases thyroid hormone turnover Signup and view all the answers

What effect does endurance training have on the hormonal response during maximal exercise?

Trained and untrained individuals have identical hormonal responses Signup and view all the answers

Which aspect of insulin resistance involves defective cellular mechanisms?

Altered insulin receptors Signup and view all the answers

What are the primary hormones that influence adaptations to resistance training?

Testosterone and growth hormone Signup and view all the answers

How does moderate physical activity affect upper respiratory tract infections (URTI)?

It provides more protection against URTI compared to a sedentary lifestyle. Signup and view all the answers

What effect does prolonged exhaustive physical activity have on the immune system?

It severely depresses the body's first line of defense against infection. Signup and view all the answers

Which of the following factors does NOT independently affect immune status?

Pain management Signup and view all the answers

How does aerobic training impact immune functions in individuals during weight loss?

It enhances natural cytotoxic immune mechanisms. Signup and view all the answers

What aspect of endocrine function is influenced by resistance training?

Changes in hormone clearance rates and secretion Signup and view all the answers

Which statement about the interaction between physical activity and stress is true?

Physical activity can mitigate stress effects on immune function. Signup and view all the answers

What is one potential negative outcome of increased training intensity in relation to immunity?

Decreased efficiency of the immune system Signup and view all the answers

What is a major function of hormones in the endocrine system?

They modify the rate of intracellular protein synthesis. Signup and view all the answers

Which of the following glands is classified as an endocrine gland?

Thymus gland Signup and view all the answers

What role does cyclic AMP play in hormone action?

It functions as a second messenger to activate specific enzymes. Signup and view all the answers

Which factor does NOT affect the activation of a target cell by a hormone?

Type of exocrine gland secreting the hormone Signup and view all the answers

How do steroid-derived hormones differ from amine or polypeptide hormones?

Steroid hormones can pass through cell membranes due to their lipid solubility. Signup and view all the answers

Which of the following correctly describes the hormones produced by the adrenal cortex?

They include glucocorticoids affecting metabolism. Signup and view all the answers

What does the term 'half-life' refer to in the context of hormones?

The time required to reduce a hormone’s concentration by half. Signup and view all the answers

What is one of the effects of chronic physical activity on hormone release?

It stabilizes growth hormone release patterns. Signup and view all the answers

What defines a target cell's specific response to a hormone?

The presence of specific protein receptors for the hormone. Signup and view all the answers

Which of the following statements best describes the action of nonsteroid hormones?

They utilize second messengers to initiate effects inside the cell. Signup and view all the answers

Study Notes

Chapter 20: The Endocrine System: Organization and Acute and Chronic Responses to Physical Activity

This chapter covers the endocrine system, its organization, and how acute and chronic physical activity affects it.
The objectives include understanding endocrine gland locations, hormonal effects on target cells, enzyme activity, and membrane transport.
Additional objectives focus on hormonal, humoral, and neural influences on endocrine gland activity, anterior and posterior pituitary hormones and their functions, and how acute and chronic physical activity affects their release.
Specific objectives for chapter 2 cover thyroid gland hormones, adrenal medulla and cortex hormones, and how exercise affects endocrine functions, including resistance training effects on testosterone and growth hormone release.

Endocrine System Overview and Organization

The endocrine system comprises communicating host organs that release chemical messengers (hormones) acting on target organs.
Endocrine glands are ductless and secrete substances directly into the extracellular spaces.
Exocrine glands have ducts and release substances to a specific surface (e.g., digestive enzymes).
Major endocrine organs include the pituitary, thyroid, parathyroid, adrenal, pineal, thymus, pancreas, gonads (ovaries and testes), hypothalamus, and adipose tissue, among others.

Hormones Produced by Endocrine System

The endocrine system produces numerous hormones, such as thyroid hormones, pituitary hormones, adrenal hormones, and pancreatic hormones.
Each hormone has a specific target tissue and role in maintaining bodily functions.

Endocrine Gland Hormones Travel in the Bloodstream

Hormones travel in the bloodstream, binding to specific receptors on target cells.
The hypothalamus and pituitary gland play critical roles in initiating hormone cascades.

Hormone Types

Hormones include steroid-derived hormones, amine hormones, and polypeptide hormones.
Half-life refers to the time required to reduce the hormone's blood concentration by half.

Hormone-Target Cell Specificity

Hormones influence target cells through modifications—rate of intracellular protein synthesis, enzyme activity, plasma membrane transport, and secretory activity.

Hormone-Receptor Binding

Hormone-receptor binding is the initial step in hormone action.
It depends on hormone concentration, receptor number, and the sensitivity/strength of the hormone-receptor bond.

3'5'-Cyclic Adenosine Monophosphate: The Intracellular Messenger

Cyclic AMP acts as a second messenger within cells, activating specific enzymes.
Three factors determine the sequence of cyclic AMP-mediated reactions within cells: target cell type, target cell-contained enzymes, and the identities of hormones acting as first messengers.

Nonsteroid Hormone Action

Nonsteroid hormones bind to receptors on the plasma membrane.
This activates adenylate cyclase, and produces cyclic AMP to trigger intracellular responses.

Hormone Effects on Enzymes

Enzymes are often altered in activity by hormones by stimulating production, altering the enzymes' shape and effectiveness, or activating inactive enzymes.

Factors That Determine Hormone Levels

Hormone secretion adapts to changing bodily demands based on factors like synthesis quantity, rate of catabolism, transport protein quantities, and plasma volume changes.

Endocrine Gland Stimulation

Endocrine glands are stimulated through hormonal, humoral, and neural mechanisms. This diagram illustrates the pathways for the regulation of cortisol by the anterior pituitary.
This diagram is designed to show the pathways by which some hormonal responses are regulated in the human body.

The Pituitary Gland, Its Secretions, and Targets

The pituitary gland (hypophysis) has anterior and posterior lobes, responsible for releasing various hormones affecting different target organs (e.g., growth hormone).

Growth Hormone: Direct and Indirect Metabolic Actions

Growth hormone (GH) influences metabolism through direct (anabolic) and indirect (somatomedin) actions.
Feedback loops regulate GH release in response to bodily needs.

Growth Hormone (GH)

Growth hormone affects cell division and proliferation.
It enhances protein synthesis by stimulating amino acid transport, RNA formation, and ribosome activity.

Growth Hormone, Physical Activity, and Tissue Synthesis #1 & #2

Physical activity influences GH release and response, affecting various tissues.
Trained individuals often exhibit a different hormonal response compared to untrained individuals.

Thyrotropin

Thyrotropin (TSH) controls thyroid gland secretion and maintains thyroid function.

Thyroid Hormones

Thyroxine (T4) and triiodothyronine (T3) regulate metabolism and other functions, including neural reflex activity, growth and development, and blood pressure.

Feedback System That Controls Thyroid Hormone Release

A feedback system regulates thyroid hormone release in response to metabolic rate changes and pituitary control.

Posterior Pituitary Hormones

Antidiuretic hormone (ADH) primarily regulates water excretion by the kidneys, responding to changes in hydration and physical activity (e.g., sweating)

Adrenal Gland Hormones & Secretions

Adrenal glands produce hormones like catecholamines, mineralocorticoids (e.g., aldosterone), and glucocorticoids (e.g., cortisol), with various functions.

Role of Norepinephrine and Epinephrine in Substrate Mobilization

Norepinephrine and epinephrine, often in response to stress and/or exercise, promote substrate mobilization (breakdown of glycogen in the liver to glucose and fats in adipose tissue).

Catecholamine Response to Increasing Intensity Cycling

Catecholamine levels (norepinephrine and epinephrine) increase with exercise intensity.

Adrenocortical Hormones: Mineralocorticoids

Mineralocorticoids, primarily aldosterone, balance mineral levels in the extracellular fluids.
Aldosterone particularly maintains sodium balance and fluid volume in the blood, impacting the kidneys.

Major Factors Control Aldosterone Release

Various factors influence aldosterone secretion, including blood volume, blood pressure, sodium, and potassium levels.

Glucocorticoids

Glucocorticoids (e.g., cortisol) affect metabolism, including protein, glucose, and fatty acids (FFA).
These actions influence other hormones and suppress the immune system.

Factors That Affect Cortisol Secretions and Its Actions

Secretion of cortisol is influenced by stress, circadian rhythm, and other factors.

Pancreatic Hormones

The pancreas contains both endocrine (islet cells) and exocrine (acinar) tissues.
Islet cells secrete hormones like insulin, glucagon, and amylin, regulating blood glucose levels.

Insulin

Insulin promotes glucose uptake into cells and regulates carbohydrate, protein, and fat metabolism.
With insufficient insulin, glucose levels can rise dangerously and spill into the urine.

Insulin's Primary Functions in the Body

Insulin's primary function is cellular glucose uptake.

Target Tissues and Specific Metabolic Responses to Insulin

Insulin's effects vary across different tissues, impacting glucose and fat metabolism.

Transporters to Facilitate Glucose Entry into Cells

Glucose transporter proteins (GLUTs) facilitate glucose movement into cells in response to blood glucose & insulin levels.

Glucose-Insulin Interaction

Blood glucose levels control insulin secretion; Elevated glucose stimulates insulin release.
This interaction is a form of negative feedback to maintain blood glucose levels.

Plasma Insulin Levels During Cycle Ergometry

Insulin levels decrease somewhat during exercise, reflecting metabolic changes associated with physical activity.

Insulin Actions and Impaired Glucose Homeostasis

Insufficient or ineffective insulin action can lead to conditions like diabetes, characterized by abnormal glucose metabolism.

Normal Insulin-Glucose Interaction and Insulin Resistance

Insulin triggers normal responses in target cells (e.g., glucose uptake), but resistance to insulin can occur with abnormal metabolism.

Glucagon

Glucagon works opposite to insulin and promotes glycogen breakdown and gluconeogenesis and is stimulated by low blood glucose levels.

Glucagon Secretion and Its Actions

Glucagon primarily affects liver and adipose tissue to stimulate glucose and lipid metabolism when needed.

Exercise Training and Endocrine Function

Exercise training can modify the endocrine system's responses to various stimuli.
Hormonal responses to exercise are typically reduced with training.

Growth Hormone and Exercise

Growth hormone is affected by exercise and training interventions.
The magnitude of response to exercise often decreases with endurance training.

Thyroid Hormones and Exercise

Exercise influences thyroid hormone turnover and can affect the relationship between hormones.

Antidiuretic Hormone (ADH)

ADH (vasopressin) levels are not significantly impacted by most types of exercise, nor do they differ between trained and untrained individuals.

Adrenal Hormones and Exercise

The adrenal glands' hormone outputs react to exercise-induced stress. Adaptations to training may influence these responses.

Epinephrine and Norepinephrine and Exercise

Catecholamine levels from adrenal glands react to exercise, especially at greater intensity. Increased output is related to the training regimen and substrate use in physically active states.

Aldosterone, Cortisol, and Pancreatic Hormones and Exercise

These hormones typically respond similarly to exercise in trained and untrained individuals, although there may be differences in the magnitude of the response.

Pre-Post Aerobic Training Differences in Glucagon and Insulin

Training interventions can cause changes in plasma insulin and glucagon levels during exercise.

Resistance Training and Endocrine Function

Resistance training can modify the body's hormonal responses to ensure physical adaptations to exercise. The hormonal adaptations associated with these activities depend primarily on testosterone and growth hormone.

Heavy Resistance Training Enhances Maximal Power and Strength

Heavy resistance training affects hormonal signaling and cellular adaptations, increasing strength and power through various mechanisms.

Physical Activity and Immune Function

Physical activity interacts with stress and illness to impact the immune system, although the relationship is complex.

Theoretical Interrelationships Among Stress, Physical Activity, Illness, and the Immune System

Stress, physical activity, illness, and the immune system have complex relationships and interact in varied ways, impacting the immune system.

Upper Respiratory Tract Infections (UTRI)

Moderate physical activity might benefit immunity against URTI.

Relationship Between Physical Activity Intensity and URTI

Physical activity, at varied levels, has both beneficial and detrimental effects on the immune response including URTIs.

Long-Term Exercise Effects on Immune System Function

Enhanced immune system function may occur with aerobic training, improving various indicators such as T-cell function.

Optimizing Immune Function

Lifestyle factors (activity, diet, sleep, etc.) can influence both immunity and responses to various stresses including both acute and chronic exercise.