Class 11 Biology Chapter 19 Chemical Coordination And Integration

Key Concept: Gene Expression Regulation

b) Steroid hormones

[Solution Description] Intracellular receptors are generally found within the cell and are typically involved with steroid hormones and iodothyronines that can pass through the lipid bilayer. These hormones influence gene expression by directly interacting with DNA in the nucleus.

Key Concept: Function Identification

b) Insulin

[Solution Description] Insulin is the hormone produced by the pancreas that helps lower blood glucose levels by facilitating the uptake of glucose into cells.

Key Concept: Hormone Pathway

c) Adrenocorticotropic hormone (ACTH)

[Solution Description] The adrenocorticotropic hormone (ACTH) is produced by the anterior pituitary gland and stimulates the adrenal cortex to secrete cortisol, a glucocorticoid involved in stress response, metabolism, and immune function regulation.

Key Concept: Real-world Application, Diurnal Rhythm Analysis

b) Decreased melatonin causing difficulty in falling asleep

[Solution Description] Bright artificial lighting at night mimics daylight, suppressing melatonin production. This disruption can lead to altered sleep patterns and other related changes due to decreased melatonin levels.

Key Concept: Hormone Effects

b) Secretin

[Solution Description] Secretin is the hormone that specifically targets the exocrine pancreas, causing it to release water and bicarbonate ions. This neutralizes stomach acid entering the small intestine.

Key Concept: Hormonal Category

c) Glycoprotein

[Solution Description] Erythropoietin is classified as a glycoprotein hormone. Glycoproteins are proteins with carbohydrate groups attached, which is characteristic of hormones like erythropoietin.

Key Concept: Gland Functions

c) Secretes insulin

[Solution Description] The pancreas has both exocrine and endocrine functions. As part of the endocrine system, its primary role is to produce insulin, which regulates blood glucose levels.

Key Concept: Hormonal Interactions

b) Inhibits GH release

[Solution Description] Somatostatin is a hypothalamic inhibiting hormone that suppresses the release of growth hormone (GH) from the anterior pituitary gland. This regulatory mechanism ensures balance in hormone levels.

Key Concept: Hormone Regulation

c) Parathyroid Hormone

[Solution Description] The parathyroid hormone (PTH) is primarily responsible for regulating serum calcium levels in the body. When calcium levels drop, PTH is secreted to increase calcium concentration by acting on bones, kidneys, and intestine.

Key Concept: Hormonal Coordination

b) Chemical coordination and integration

[Solution Description] Hormones in invertebrates provide chemical coordination and integration, meaning they help coordinate various physiological processes and integrate responses throughout the organism.

Key Concept: System Interaction

b) By enhancing the fight or flight response

[Solution Description]

During stress, the adrenal glands produce hormones such as adrenaline and cortisol. Adrenaline enhances the fight or flight response by increasing heart rate and energy supplies, while cortisol helps maintain fluid balance and blood pressure, influencing how the neural system manages stress.

Key Concept: Hormone Function

c) Insulin

[Solution Description] Insulin, secreted by β-cells of the pancreas, decreases blood glucose levels by enhancing cellular glucose uptake and glycogenesis.

Key Concept: Hormone Source

c) Kidney

[Solution Description] The kidney is responsible for secreting erythropoietin, which plays a crucial role in the production of red blood cells.

Key Concept: Second Messenger Examples

d) Insulin

[Solution Description] Second messengers are molecules inside cells that act to transmit signals from a receptor to a target. Common examples include cyclic AMP (cAMP), inositol triphosphate (IP3), and calcium ions (Ca²⁺). Insulin, however, is a hormone and not a second messenger.

Key Concept: Gland Functionality

c) Release hormones for metabolic and electrolyte balance

[Solution Description] The adrenal cortex secretes glucocorticoids such as cortisol, which are involved in metabolism regulation, and mineralocorticoids like aldosterone, which help maintain electrolyte balance and regulate blood pressure.

Key Concept: Thyroid Disorders

c) Hypothyroidism

[Solution Description] Hypothyroidism is a condition where there is an insufficient production of thyroid hormones. This results in a decreased metabolic rate, causing symptoms such as weight gain, fatigue, and sensitivity to cold.

Key Concept: Mechanism of Action

c) By enhancing cellular glucose uptake and glycogenesis

[Solution Description] Insulin primarily decreases blood glucose levels by enhancing the cellular uptake of glucose into cells and stimulating glycogenesis, which is the conversion of glucose to glycogen in the liver and muscles. These actions reduce the concentration of glucose in the bloodstream.

Key Concept: Hormone-Receptor Complex

d) Regulation of gene expression

[Solution Description]

Upon entering the cell, a steroid hormone binds to its specific intracellular receptor to form a hormone-receptor complex. This complex translocates into the nucleus and binds to specific DNA sequences to regulate gene expression, leading to biochemical changes in the target tissue.

Key Concept: Endocrine Gland Functions

b) It decreases blood calcium levels.

[Solution Description] Calcitonin, a hormone released by the thyroid gland, lowers blood calcium levels by inhibiting osteoclast activity and promoting calcium uptake by bones. This reduces the concentration of calcium in the bloodstream.

Key Concept: Endocrine System Components

c) It regulates pituitary hormone synthesis and secretion.

[Solution Description] The hypothalamus plays a critical role as it regulates the secretion of pituitary hormones. It produces releasing and inhibiting hormones that control the synthesis and release of hormones from the anterior pituitary gland.

Key Concept: Hormone Effects

b) Regulation of basal metabolic rate

[Solution Description] Thyroid hormones such as T3 and T4 primarily regulate the basal metabolic rate, which involves increasing oxygen consumption and energy production in cells, thereby controlling the body’s metabolism.

Key Concept: Basic Function

b) Production of ova

[Solution Description] The ovaries are responsible for two main functions: producing ova (eggs) and secreting hormones such as estrogen and progesterone.

Key Concept: Gland Location

b) Above the kidneys

[Solution Description] The adrenal glands are located above the kidneys in the human body.

Key Concept: Hormone Function

c) It generates second messengers that lead to cellular responses.

[Solution Description] Protein hormones interact with membrane-bound receptors, leading to the production of second messengers like cyclic AMP. These second messengers initiate various biochemical processes within the cell.

Key Concept: Hormone Identification

b) Thymosins

[Solution Description] The thymus gland secretes a group of hormones known as thymosins. These peptide hormones play a vital role in the development of the immune system by promoting the differentiation of T-lymphocytes.

Key Concept: Hormone Source

d) Heart

[Solution Description] ANF is specially produced by the atrial wall of the heart. This peptide hormone helps regulate blood pressure and fluid balance.

Key Concept: Hormone Interaction

c) Glucocorticoids regulate metabolism and have anti-inflammatory effects; mineralocorticoids maintain electrolyte balance.

[Solution Description] Glucocorticoids, such as cortisol, primarily regulate metabolism of carbohydrates, proteins, and fats and have anti-inflammatory effects, whereas mineralocorticoids, like aldosterone, primarily maintain electrolyte balance by promoting sodium retention and potassium excretion in the kidneys.

Key Concept: Glandular Structure

c) Pars nervosa

[Solution Description] The posterior pituitary gland, known as pars nervosa, does not produce hormones itself. Instead, it stores and releases hormones such as oxytocin and vasopressin (antidiuretic hormone – ADH) that are synthesized by the hypothalamus and transported down nerve fibers to be stored until needed.

Key Concept: Hormone Regulation

d) Blood glucose levels

[Solution Description]

Insulin secretion from the pancreas is primarily regulated by blood glucose levels. When blood glucose levels rise, such as after eating, insulin is secreted to help cells absorb glucose, thereby lowering blood glucose levels.

Key Concept: Hormone-Receptor Complex

a) Hormone-receptor complex

[Solution Description]

When a hormone binds to its specific receptor, it forms a hormone-receptor complex. This complex initiates a series of biochemical changes within the target tissue, leading to the desired physiological effect of the hormone. The formation of this complex is crucial for hormone action.

Key Concept: Detailed Mechanism, Clinical Application

b) Through modulation of insulin-like growth factor (IGF-1).

[Solution Description] Testosterone binds to androgen receptors in muscle tissues, leading to changes in gene expression that promote muscle protein synthesis and growth. Impairment in androgen receptor function may reduce these anabolic effects, potentially causing muscle wasting conditions or reduced muscle strength clinically.

Key Concept: Hormone Interaction

b) By secreting ANF to regulate salt and water balance

[Solution Description] The heart has specialized cells in the atria that release a peptide hormone known as Atrial Natriuretic Factor (ANF). This hormone plays a role in reducing blood volume and pressure by increasing sodium excretion from the kidneys.

Key Concept: Comparative Hormone Function, Hormone and Development

c) Testosterone mainly influences male secondary sexual characteristics; estradiol influences female secondary sexual characteristics

[Solution Description] Testosterone and estradiol are both crucial for the development of secondary sexual characteristics but have different roles based on gender. In males, testosterone promotes the development of male secondary sex characteristics such as increased muscle mass, facial hair growth, and deepening of the voice. In females, estradiol is responsible for the development of female secondary sex characteristics including breast development, widening of hips, and regulation of menstrual cycles. These hormones interact with their respective intracellular receptors and regulate gene expression that drives these developmental processes.

Key Concept: Calcium Balance

c) Increasing renal calcium reabsorption

[Solution Description] The parathyroid hormone (PTH) helps in maintaining calcium balance by increasing blood calcium levels through three main actions: stimulating bone resorption, increasing reabsorption of calcium by renal tubules, and enhancing absorption of calcium from the digestive tract.

Key Concept: Basic Function

c) Promoting glucose uptake and utilization

[Solution Description] Thyroid hormones regulate the metabolic processes in the body including those involved in carbohydrate metabolism. They increase the basal metabolic rate and influence the metabolism of carbohydrates by promoting glucose uptake and utilization for energy production.

Key Concept: Hormone Interaction

d) Adrenocorticotropic hormone (ACTH)

[Solution Description] The anterior pituitary secretes Adrenocorticotropic Hormone (ACTH), which stimulates the adrenal cortex to produce glucocorticoids and mineralocorticoids. This interaction is part of the hypothalamic-pituitary-adrenal axis.

Key Concept: Intracellular Receptor Effects

d) By altering gene expression

[Solution Description] Steroid hormones are lipophilic and can pass through the cell membrane to bind directly to intracellular receptors. These hormone-receptor complexes then act as transcription factors that bind to DNA and influence gene expression, altering protein synthesis and hence regulating various physiological processes.

Key Concept: Hormone Classification

a) Insulin

[Solution Description] Peptide hormones are comprised of amino acids and are typically produced by the anterior pituitary gland, hypothalamus, and other glands. Insulin is a well-known example of a peptide hormone because it is made up of amino acid chains.

Key Concept: Hormone Regulation

b) Low oxygen levels

[Solution Description] Erythropoietin is released in response to low oxygen levels in the blood. The kidneys detect this hypoxia and secrete erythropoietin, which stimulates red blood cell production to increase oxygen transport.

Key Concept: Hormone Interaction Effects

b) Gene expression is altered

[Solution Description] When cortisol binds to its intracellular receptor, the hormone-receptor complex translocates into the nucleus where it interacts with specific DNA sequences to modulate gene expression, often resulting in metabolic changes like gluconeogenesis.