Hormones and Their Mechanisms

Questions and Answers

What type of hormone is epinephrine classified as?

Peptide/protein

Lipid soluble

Intracellular

Water-soluble (correct)

Where are the receptors for water-soluble hormones located?

In the cell nucleus

On the intracellular membranes

In the cytoplasm

On the cell surface or plasma membrane (correct)

Which second messenger is associated primarily with ADH's action?

Inositol-triphosphate (IP3)

Diacylglycerol (DAG)

cAMP (cyclic adenosine monophosphate) (correct)

Tyrosine kinase

What is the primary mechanism of action for lipid-soluble hormones?

They diffuse through the membrane and bind to intracellular receptors Signup and view all the answers

Which one of the following hormones utilizes the second messenger inositol-triphosphate (IP3)?

Catecholamines (α receptors) Signup and view all the answers

Which class of hormone typically binds to receptors on the cell surface?

Peptide/protein hormones Signup and view all the answers

What outcome occurs when a second messenger is activated in a target cell?

Activates or deactivates enzyme activity Signup and view all the answers

Which hormone is secreted from the pituitary and acts through tyrosine kinase?

Insulin Signup and view all the answers

What is a characteristic symptom of prolactin excess?

Osteoporosis in females Signup and view all the answers

How does ACTH influence the adrenal cortex?

Increases cellularity and vascularity Signup and view all the answers

What is the half-life of adrenocorticotrophic hormone (ACTH)?

5-15 minutes Signup and view all the answers

Which hormone primarily regulates the release of ACTH?

Corticotropin-releasing hormone (CRH) Signup and view all the answers

What is a possible cause of excess ACTH production?

Pituitary tumors that secrete ACTH Signup and view all the answers

Which factor does NOT stimulate ACTH release?

High cortisol levels Signup and view all the answers

What effect does corticotropin releasing hormone have on the pituitary?

Stimulates ACTH secretion Signup and view all the answers

What effect does ACTH have on skin pigmentation?

Increases pigmentation Signup and view all the answers

What is NOT a symptom of prolactin excess?

Increased appetite Signup and view all the answers

Which hormone released by the anterior lobe of the pituitary stimulates the release of thyroid-stimulating hormone?

Thyrotropin releasing hormone Signup and view all the answers

What is the primary role of somatostatin in relation to the pituitary gland?

Inhibits GH secretion Signup and view all the answers

What type of connection exists between the hypothalamus and the posterior pituitary?

Neural connection Signup and view all the answers

Which of the following hormones is stored and released by the posterior pituitary?

Oxytocin Signup and view all the answers

What effect does prolactin inhibiting hormone have on the pituitary?

Inhibits PRL secretion Signup and view all the answers

Which hormone is responsible for stimulating both luteinizing hormone and follicle-stimulating hormone secretion?

Gonadotropin releasing hormone Signup and view all the answers

What is the primary difference between the anterior and posterior lobes of the pituitary gland?

The anterior lobe synthesizes hormones, while the posterior lobe stores hormones. Signup and view all the answers

Which hormone accounts for about 95 percent of all glucocorticoid activity?

Cortisol Signup and view all the answers

What is the primary role of cortisol in carbohydrate metabolism?

Causes hyperglycemia through anti-insulin actions Signup and view all the answers

What effect does cortisol have on protein stores in the body?

Reduces protein stores in all cells except liver Signup and view all the answers

What is the primary effect of cortisol on fat metabolism?

Enhances fat mobilization and ketone body formation Signup and view all the answers

Which enzyme converts cortisol to cortisone in the body?

11β-Hydroxysteroid dehydrogenase (Type 1) Signup and view all the answers

What percentage of cortisol in plasma typically binds to cortisol-binding globulin?

90 to 95 percent Signup and view all the answers

Which of the following hormones requires cortisol for its calorigenic effects?

Catecholamines Signup and view all the answers

What is the half-life of cortisol?

60-90 minutes Signup and view all the answers

Which condition is associated with increased secretion of angiotensinogen?

Cushing's syndrome Signup and view all the answers

What is a key characteristic of Addison's disease?

Hyperpigmentation Signup and view all the answers

What is the primary cause of primary adrenal insufficiency?

Tuberculosis or autoantibodies Signup and view all the answers

What symptom is a result of cortisol deficiency?

Muscle weakness Signup and view all the answers

Which hormone accounts for about 90 percent of all mineralocorticoid activity?

Aldosterone Signup and view all the answers

Which of the following is a symptom of adrenal insufficiency?

Severe gastrointestinal upset Signup and view all the answers

What change in the central nervous system can occur due to excess cortisol?

Rapid EEG rhythm Signup and view all the answers

What defines an Addisonian crisis?

Circulatory collapse due to stress Signup and view all the answers

Study Notes

Hormones and Their Receptors

Hormones can be classified as water-soluble or lipid-soluble.
Water-soluble hormones (e.g., amine epinephrine, peptide/protein hormones) bind to receptors on cell surfaces.
Lipid-soluble hormones (e.g., thyroid hormones, steroids, Vitamin D) have receptors located intracellularly.

Mechanism of Action of Hormones

Water-soluble hormones do not cross the lipid bilayer and bind to surface receptors.
Binding activates membrane-bound enzymes, producing second messengers (e.g., cAMP).
Second messengers alter cell functions by activating or deactivating various enzymes.

Second Messenger Systems

Receptors for water-soluble hormones found on the plasma membrane are coupled to second messenger systems.
Key second messengers include:
- cAMP: involved with hormones like ADH (V2 receptor), LH, FSH, TSH, ACTH, PTH, calcitonin, glucagon, catecholamines (β receptors).
- Tyrosine Kinase: involved with oxytocin, growth hormone, prolactin, insulin, and erythropoietin.
- Inositol-triphosphate (IP3), diacylglycerol (DAG), and calcium: involved with GnRH, TRH, catecholamines (α receptors), angiotensin II, and ADH (V1 receptor).

Hypothalamic Hormones and Their Effects

Corticotropin-releasing hormone (CRH): Stimulates ACTH secretion.
Thyrotropin-releasing hormone (TRH): Stimulates TSH secretion.
Growth hormone-releasing hormone (GHRH): Stimulates GH secretion.
Somatostatin: Inhibits GH secretion.
Gonadotropin-releasing hormone (GnRH): Stimulates LH and FSH secretion.
Prolactin-releasing hormone (PRH): Stimulates PRL secretion.
Prolactin-inhibiting hormone (Dopamine): Inhibits PRL secretion.

Hypothalamus and Posterior Pituitary Connection

Neural connections exist between the hypothalamus and posterior pituitary.
Posterior pituitary stores and releases hormones (ADH and oxytocin) produced by the hypothalamus.
Anterior lobe synthesizes hormones that regulate other endocrine glands.

Hormones of the Pituitary Gland

Posterior Lobe: Antidiuretic hormone (ADH) and Oxytocin.
Anterior Lobe:
- Adrenocorticotropic hormone (ACTH)
- Growth hormone (GH)
- Thyroid-stimulating hormone (TSH)
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Prolactin (PRL).

Prolactin excess due to pituitary tumors may cause:
- Infertility, amenorrhoea, galactorrhoea, impotence, loss of libido in males, and osteoporosis in females.
ACTH:
- Peptide hormone with a half-life of 5-15 minutes.
- Regulated by CRH with negative feedback from ACTH and cortisol.
- Released in response to stress and exhibits a diurnal rhythm.

Effects of ACTH

Trophic effect leading to increased cellularity and cortisol secretion from the adrenal cortex.
Increases adrenal cortex responsiveness to ACTH.
May cause skin pigmentation effects similar to MSH.

Adrenal Cortex Hormones

Mineralocorticoids: Primarily Aldosterone.
Glucocorticoids: Primarily Cortisol (95% of glucocorticoid activity).
Sex Hormones: Androgens.

Cortisol Function and Disorders

Essential for life, released in response to ACTH.
Causes hyperglycemia and enhances protein catabolism.
Increases fatty acid mobilization; provides permissive effects for catecholamines and glucagon.
Deficiency leads to Addison's disease, causing hyponatremia, hypotension, hyperkalemia, and weight loss.

Aldosterone

Main mineralocorticoid responsible for sodium retention and potassium excretion.
Essential for life and accounts for 90% of mineralocorticoid activity.

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Description

This quiz covers the classification of hormones into water-soluble and lipid-soluble types, detailing their binding mechanisms and receptor locations. It also explains the action of second messengers and their role in cellular responses. Test your knowledge on the specifics of hormone receptors and their interactions within the human body.