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Hormone Classification and Action
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Hormone Classification and Action

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Questions and Answers

What are two benefits of having a portal system that connects the hypothalamus with the anterior pituitary gland?

One benefit is that it ensures that the controlling hormones will be delivered directly to the target cells. Secondly, hormones go directly to their target cells without passing through general circulation, so they are not diluted.

A given hormone generally has the same effect on different target tissues.

False

What normally stops hormone action?

Hormones are degraded by enzymes and eliminated in the urine.

How does the embryological origin of the two distinct parts of the pituitary gland relate to the control of secretion?

<p>The posterior pituitary is an extension of the brain that secretes neurohormones synthesized in the hypothalamus, while the anterior pituitary is glandular and regulated by hypothalamic hormones.</p> Signup and view all the answers

What is hypothyroidism?

<p>Hypothyroidism results from the thyroid gland producing lower than normal amounts of thyroid hormones.</p> Signup and view all the answers

Name two typical sources of testosterone.

<p>Adrenal glands and testes.</p> Signup and view all the answers

What is the condition of decreased thyroid hormone secretion called?

<p>Hypothyroidism.</p> Signup and view all the answers

What type of reflex pathway is involved in the secretion of adrenal hormones triggered by a pituitary hormone?

<p>Long-loop negative feedback</p> Signup and view all the answers

What are the two similar explanations for the resulting pathology in diabetes mellitus and diabetes insipidus?

<p>Diabetes mellitus can result from lack of insulin secretion or lack of response of insulin receptors. Diabetes insipidus can result from lack of ADH secretion or lack of responsiveness of ADH receptors.</p> Signup and view all the answers

How does dexamethasone affect patients with hypercortisolism?

<p>Dexamethasone suppresses the pituitary's activity and ACTH secretion, which may normalize cortisol levels in some patients.</p> Signup and view all the answers

Match the following hormones to their corresponding sources and effects of a tumor.

<p>Corticotropin-releasing hormone = Hypothalamus, decrease Adrenocorticotropic hormone = Anterior pituitary, decrease Cortisol = Adrenal cortex, increase</p> Signup and view all the answers

Fill in the names of the hypothalamic hormone that triggers a pituitary hormone causing the release of an adrenal hormone.

<p>Corticotropin-releasing hormone</p> Signup and view all the answers

If a tumor in the adrenal cortex resulted in hypercortisolism, how would this affect relative levels of hormone produced from each source?

<p>Corticotropin-releasing hormone and adrenocorticotropic hormone would decrease, while cortisol would increase.</p> Signup and view all the answers

What is the endocrine consequence of eliminating cholesterol from the diet?

<p>It is not realistic because cholesterol is produced by the liver and is essential for cell membranes and steroid hormone production.</p> Signup and view all the answers

What does hypercortisolism indicate and how can it be identified?

<p>Hypercortisolism indicates excessive cortisol production, which can be identified by monitoring ACTH levels.</p> Signup and view all the answers

Which patient's cortisol secretion level falls to normal after receiving dexamethasone?

<p>Anika</p> Signup and view all the answers

What may be wrong with Candace, who has elevated testosterone and no uterus?

<p>Candace may have testes instead of ovaries, suggesting androgen insensitivity syndrome.</p> Signup and view all the answers

What is one general principle of hormone action indicated by the number of insulin receptors per fat cell?

<p>Hormones exert their effects at very low concentrations.</p> Signup and view all the answers

Which of the following is NOT a method of hormone action?

<p>All are methods of hormone action.</p> Signup and view all the answers

When a catecholamine or peptide hormone binds to receptors on the surface of a cell, what occurs?

<p>A second messenger appears in the cytoplasm.</p> Signup and view all the answers

The link between a first messenger and a second messenger in a cell that responds to peptide hormones is usually:

<p>A G protein</p> Signup and view all the answers

When adenylyl cyclase is activated, what is formed?

<p>cAMP is formed.</p> Signup and view all the answers

Typically, when steroid hormones bind to their receptors, what may occur?

<p>Gene transcription may increase or decrease.</p> Signup and view all the answers

Steroid hormones are synthesized in the ________ of the cell.

<p>Smooth endoplasmic reticulum</p> Signup and view all the answers

Each of the following statements concerning peptide hormones is true except one. Identify the exception.

<p>Peptide hormones in the bloodstream are always bound to carrier proteins.</p> Signup and view all the answers

Each of the following hormones is an amino acid derivative except one. Identify the exception.

<p>Thyroid-stimulating hormone</p> Signup and view all the answers

The majority of hormones in the body are:

<p>Peptide hormones.</p> Signup and view all the answers

The most complex endocrine responses involve the:

<p>Hypothalamus.</p> Signup and view all the answers

The posterior pituitary gland secretes:

<p>ADH (Vasopressin).</p> Signup and view all the answers

The pituitary hormone that controls the release of glucocorticoids from the adrenal cortex is:

<p>ACTH.</p> Signup and view all the answers

The pituitary hormone that controls hormone synthesis and release from the thyroid gland is:

<p>TSH.</p> Signup and view all the answers

The pituitary hormone that stimulates milk production by the mammary glands is:

<p>Prolactin.</p> Signup and view all the answers

The pituitary hormone that stimulates cell growth and metabolism in many tissues is:

<p>Somatotropin.</p> Signup and view all the answers

What type of hormone is a lipophobic molecule that interacts with receptors on the cell surface?

<p>Peptide hormone</p> Signup and view all the answers

What is the site of vasopressin synthesis?

<p>Hypothalamus</p> Signup and view all the answers

What is the true endocrine gland of epithelial origin?

<p>Anterior pituitary</p> Signup and view all the answers

Which hormone cannot be stored in secretory vesicles?

<p>Steroid hormone</p> Signup and view all the answers

What are derivatives of tyrosine called?

<p>Amino acid-derived hormones</p> Signup and view all the answers

What is the storage and release site for oxytocin?

<p>Posterior pituitary</p> Signup and view all the answers

Match each hormone with its primary source: adrenal medulla.

<p>Epinephrine</p> Signup and view all the answers

Match each hormone with its primary source: pancreas.

<p>Insulin</p> Signup and view all the answers

Match each hormone with its primary source: thyroid.

<p>Calcitonin</p> Signup and view all the answers

Match each hormone with its primary source: anterior pituitary.

<p>Prolactin</p> Signup and view all the answers

Match each hormone with its primary source: adrenal cortex.

<p>Aldosterone</p> Signup and view all the answers

Match each hormone with its primary source: pineal.

<p>Melatonin</p> Signup and view all the answers

The study of hormones is known as the field of __________.

<p>Endocrinology</p> Signup and view all the answers

The __________ of a hormone is an indicator of how long a hormone is active in the body.

<p>Half-life</p> Signup and view all the answers

A circulatory route that has two sets of capillaries is known as a __________.

<p>Portal system</p> Signup and view all the answers

The posterior pituitary gland is also known as the ________.

<p>Neurohypophysis</p> Signup and view all the answers

The anterior pituitary gland is also known as the ________.

<p>Adenohypophysis</p> Signup and view all the answers

The sex hormones that regulate the male and female reproductive organs are collectively called ________.

<p>Gonadotropins</p> Signup and view all the answers

________ is a decrease in the number of receptors of target cells in order to dampen the effects of excess hormone.

<p>Down-regulation</p> Signup and view all the answers

The ________ gland sits along the superior border of the kidney.

<p>Adrenal</p> Signup and view all the answers

The outer layer of the adrenal gland is called the ________.

<p>Adrenal cortex</p> Signup and view all the answers

The inner portion of the adrenal gland is called the ________.

<p>Adrenal medulla</p> Signup and view all the answers

The adrenal cortex produces a steroid hormone called ________ that controls Na+ and K+ homeostasis and another steroid hormone called ________ that controls blood glucose levels.

<p>Aldosterone, cortisol</p> Signup and view all the answers

The term for two hormones that have additive effects is ________.

<p>Synergists</p> Signup and view all the answers

The term that describes the need for one hormone to be present for a second hormone to produce a full effect is called ________.

<p>Permissive</p> Signup and view all the answers

Two hormones that have opposing effects are called ________.

<p>Antagonists</p> Signup and view all the answers

When an organ or gland shrinks due to lack of use, that condition is referred to as ________.

<p>Atrophy</p> Signup and view all the answers

The term for any hormone that controls the secretion of another hormone is a ________.

<p>Trophic hormone</p> Signup and view all the answers

The hormones of the anterior pituitary are controlled by trophic hormones from the ________.

<p>Hypothalamus</p> Signup and view all the answers

The trophic hormones reach the pituitary through the ________.

<p>Hypothalamic-hypophyseal portal system</p> Signup and view all the answers

________ pathologies arise in the last endocrine gland in a reflex.

<p>Primary</p> Signup and view all the answers

A ________ is a problem with one of the tissues producing trophic hormones.

<p>Secondary pathology</p> Signup and view all the answers

Chemical signals released into the blood by neurons are called ________.

<p>Neurohormones</p> Signup and view all the answers

When stimulated by a particular hormone, there is a marked increase in the activity of G proteins in the membrane. The hormone is probably:

<p>A steroid</p> Signup and view all the answers

After a hormone has exerted its effects, it typically:

<p>Is inactivated or removed from the blood.</p> Signup and view all the answers

Hormones are not typically considered to be cytokines because hormones are ________ like cytokines.

<p>Synthesized in advance and stored, not</p> Signup and view all the answers

In a simple endocrine reflex, the endocrine cell is the:

<p>Sensor and integrating center.</p> Signup and view all the answers

Synergism occurs when:

<p>Hormones working together produce a larger effect than predicted.</p> Signup and view all the answers

Hormones acting through signal transduction pathways elicit a ________ response compared to hormones that produce genomic effects.

<p>Faster</p> Signup and view all the answers

A cell's or tissue's response to a hormone primarily depends on ________ and ________.

<p>Cell receptors, signal transduction pathways</p> Signup and view all the answers

The signal molecule produced by one animal that may affect the behavior of another animal of the same species is called the ________.

<p>Pheromone or ectohormone</p> Signup and view all the answers

A signal molecule that is secreted into the external environment, instead of into the blood, is called a(n) ________.

<p>Ectohormone or pheromone</p> Signup and view all the answers

Study Notes

Hormone Classification and Action

  • Peptide hormones: lipophobic, interact with cell surface receptors, synthesized as prohormones, short half-life, not bound to carrier proteins in bloodstream.
  • Steroid hormones: lipophilic, synthesized in smooth ER, cannot be stored in secretory vesicles, affect gene transcription.
  • Amino acid-derived hormones: derivatives of tyrosine (e.g., thyroid hormone, epinephrine, norepinephrine, melatonin). Thyroid-stimulating hormone is an exception; it's a peptide hormone.
  • Most hormones are peptide hormones.
  • Hormone action methods: control of electrical signaling pathways, ion/molecule transport across membranes, enzymatic reaction rates, gene expression/protein synthesis.
  • Second messengers in peptide hormone action: usually G proteins, cAMP, calcium.
  • Adenylyl cyclase activation leads to cAMP formation.
  • Steroid hormone binding to receptors may increase or decrease gene transcription.

Hormone Release Control

  • Hypothalamus: central role in complex endocrine responses.
  • Posterior pituitary gland: secretes ADH (Vasopressin).
  • Anterior pituitary gland: true endocrine gland of epithelial origin, secretes various hormones (TSH, ACTH, FSH, LH, prolactin, somatotropin).
  • TSH controls thyroid hormone release.
  • ACTH controls glucocorticoid release from adrenal cortex.
  • Prolactin stimulates milk production.
  • Somatotropin stimulates cell growth and metabolism.

Endocrine Glands and Hormones

  • Adrenal gland: located superior to kidney, consists of cortex and medulla.
  • Adrenal cortex: produces aldosterone (Na+, K+ homeostasis) and cortisol (blood glucose control).
  • Adrenal medulla: produces epinephrine.
  • Pancreas: produces insulin.
  • Thyroid: produces calcitonin.
  • Pineal gland: produces melatonin.
  • Anterior pituitary: produces prolactin.

Hormone Interactions

  • Synergism: hormones produce a larger effect together than individually (e.g., epinephrine and glucagon on blood glucose).
  • Permissiveness: one hormone is needed for another to exert its full effect (e.g., reproductive hormones and thyroid hormone).
  • Antagonism: hormones have opposing effects (e.g., glucagon and insulin).

Endocrine Pathologies

  • Down-regulation: decrease in receptor number due to excess hormone.
  • Atrophy: shrinkage of organ/gland due to lack of use.
  • Primary pathologies: arise in the final endocrine gland in a reflex pathway.
  • Secondary pathologies: problems in tissues producing trophic hormones.

Other Key Concepts

  • Endocrinology: study of hormones.
  • Half-life: indicator of hormone's active duration.
  • Portal system: circulatory route with two capillary beds (e.g., hypothalamic-hypophyseal portal system).
  • Neurohypophysis: posterior pituitary gland.
  • Adenohypophysis: anterior pituitary gland.
  • Gonadotropins: sex hormones regulating reproductive organs.
  • Trophic hormone: controls secretion of another hormone.
  • Neurohormones: chemical signals released into blood by neurons.
  • Ectohormones/pheromones: signals secreted into external environment.

Pituitary Gland and Hormone Secretion

  • The posterior pituitary, an extension of the hypothalamus, secretes neurohormones synthesized in the hypothalamus. Secretion is triggered by hypothalamic signals.
  • The anterior pituitary, derived from the roof of the mouth, is glandular epithelium. Its hormone secretion is regulated by hypothalamic releasing and inhibiting hormones.
  • Hormone type and secretion regulation depend on the pituitary tissue type (neurosecretory vs. glandular).

Evolutionary Conservation of Hormone Activity

  • Hormone structure and function are highly conserved across vertebrate evolution.
  • This explains the effectiveness of animal-derived hormones (e.g., insulin from pigs or cows) in treating human diseases like diabetes. Before the availability of animal-derived insulin, diabetes diagnosis often resulted in death.

Hypothalamic-Pituitary-Adrenal (HPA) Axis and Feedback

  • Corticotropin-releasing hormone (CRH) from the hypothalamus stimulates adrenocorticotrophic hormone (ACTH) release from the anterior pituitary.
  • ACTH then stimulates cortisol release from the adrenal cortex.
  • A tumor in the adrenal cortex causing hypercortisolism would increase cortisol, but decrease CRH and ACTH levels due to long-loop negative feedback.

Endocrine Pathologies: Diagnosing Hypercortisolism

  • Dexamethasone, a drug suppressing ACTH, can differentiate between primary (adrenal) and secondary (pituitary) hypercortisolism.
  • If cortisol levels normalize after dexamethasone, hypercortisolism is secondary (pituitary).
  • If cortisol levels remain elevated, hypercortisolism is primary (adrenal), also known as Cushing's syndrome.

Anterior Pituitary Hormones

  • Anterior pituitary hormones aren't neurohormones because the anterior pituitary is not neuronal tissue.
  • The term "trophic" accurately describes these hormones as they stimulate other glands to produce hormones.
  • Hypothalamic releasing hormones trigger anterior pituitary hormone release.

Hypothyroidism Diagnosis

  • Hypothyroidism is characterized by low thyroid hormone production.
  • Blood tests measuring T3, T4, and TSH levels differentiate between primary (thyroid) and secondary (hypothalamic/pituitary) hypothyroidism.
    • Elevated TSH indicates primary hypothyroidism.
    • Decreased TSH indicates secondary hypothyroidism.

Androgen Insensitivity Syndrome

  • Androgen insensitivity syndrome presents as a female phenotype (breasts, pubic/axillary hair) despite the presence of testes and elevated testosterone.
  • The lack of masculinization is due to tissue unresponsiveness to testosterone.
  • A lack of uterus is indicative of a genetic male. Chromosomal analysis (karyotyping) confirms this diagnosis.

Cholesterol and Hormone Synthesis

  • It's impossible to eliminate all cholesterol from the body because the liver produces it, and cholesterol is vital for cell membranes and steroid hormone synthesis.
  • Completely eliminating cholesterol would be fatal due to consequences on endocrine function.
  • Decreasing thyroid hormone production with age is associated with decreased responsiveness to thyroid-releasing hormone (TRH) and increased responsiveness to thyroid hormone.
    • The decreased response to TRH may be due to reduced receptor availability in the anterior pituitary.
    • The increased response to thyroid hormone may be due to upregulation of receptors in target cells or reduced hormone metabolism.

Diabetes Mellitus and Insipidus

  • Both diabetes mellitus (glucose regulation failure) and diabetes insipidus (water regulation failure through ADH malfunction) result from either hormone deficiency or receptor dysfunction.

Insulin Receptor Density and Hormone Action

  • A single fat cell has approximately 104 insulin receptors and 1010 phospholipid molecules.
  • There are 106 phospholipid molecules per insulin receptor.
  • This low receptor density supports the principle that hormones act at very low concentrations.

Blood Glucose and Insulin Levels During Fasting and Feeding

  • During prolonged fasting, blood glucose is low, insulin is low, and insulin receptor concentration in skeletal muscle is high (increased sensitivity).
  • After a meal, blood glucose and insulin are high, and insulin receptor concentration is low (decreased sensitivity).

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Description

Explore the fascinating world of hormones with this quiz on their classification and action mechanisms. Understand the differences between peptide, steroid, and amino acid-derived hormones, along with their roles in cellular processes. Test your knowledge on how hormones interact with the body and their methods of action.

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