Hormone Action Overview

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Questions and Answers

What is the primary role of receptors in hormone action?

  • To act as inhibitors for hormone interactions.
  • To produce hormones in the cytoplasm.
  • To directly transport hormones into the cell.
  • To maintain homeostasis by responding to specific hormones. (correct)

Which of the following hormones primarily uses the mobile receptor mechanism for its action?

  • Cortisol (correct)
  • Growth hormone
  • Antidiuretic hormone (ADH)
  • Oxytocin

Which statement accurately describes the fixed membrane receptor mechanism?

  • It allows hormones to freely diffuse through the plasma membrane.
  • It predominantly functions with lipid-soluble hormones.
  • It involves hormone-receptor complexes entering the nucleus.
  • It utilizes cyclic AMP as a secondary messenger after hormone binding. (correct)

What occurs when a water-soluble hormone binds to its receptor?

<p>Cyclic AMP is produced as a secondary messenger. (A)</p> Signup and view all the answers

What is the consequence of cyclic AMP (cAMP) activation within a target cell?

<p>Activation of several enzymatic reactions. (C)</p> Signup and view all the answers

Which hormone mechanism primarily regulates gene expression?

<p>Binding to intracellular receptors. (B)</p> Signup and view all the answers

What happens to cyclic AMP after it has acted in a target cell?

<p>It is deactivated by phosphodiesterase. (C)</p> Signup and view all the answers

How do amino acid derivative hormones typically function within cells?

<p>By passing through cell membranes to activate intracellular receptors. (B)</p> Signup and view all the answers

Flashcards

Hormone Action: Homeostasis

Hormones maintain the body's internal balance, a state called homeostasis.

Hormone Receptors

Receptors are specific proteins that bind with hormones, acting like locks and keys.

Receptor Sensitivity

The sensitivity and responsiveness of a receptor depend on the number of receptors and their affinity for the hormone.

Receptor Location

Some hormones bind to receptors on the cell membrane, while others bind to receptors inside the cell.

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Fixed Membrane Receptor Mechanism

Water-soluble hormones like proteins and amines can't enter cells. They bind to membrane receptors and trigger a chain of events inside the cell.

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Mobile Receptor Mechanism

Lipid-soluble hormones, such as steroids and fatty acids, can pass through the cell membrane and bind to receptors inside the cell.

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Hormone-Receptor Complex: Gene Expression

The hormone-receptor complex activates DNA transcription, leading to protein synthesis.

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Hormone Action Mechanisms: Two Types

The mechanism of hormone action is categorized into two main types: Fixed Membrane Receptor and Mobile Receptor.

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Study Notes

Hormone Action

  • Hormones maintain homeostasis in the body.
  • Hormone receptors are specific to each hormone.
  • Receptor sensitivity depends on receptor number and affinity.
  • Receptor location varies: cell membrane (e.g., protein hormones, catecholamines), cytoplasm (e.g., steroid hormones), or nucleus (e.g., thyroxine).
  • Hormone types include peptides, polypeptides, proteins, steroids, iodothyronines (thyroid hormones), and amino acid derivatives.
  • Membrane-bound receptor hormones don't enter cells; they trigger second messengers to change cell metabolism.
  • Intracellular receptor hormones regulate gene expression or chromosome function by interacting with the genome.

Mechanism of Hormone Action

  • Two main mechanisms:
    • Fixed membrane receptor mechanism
    • Mobile receptor mechanism

Fixed Membrane Receptor Mechanism

  • Water-soluble hormones (amines, proteins) use this mechanism.
  • These hormones can't pass through the lipid cell membrane.
  • They bind to cell membrane receptors.
  • Binding activates adenyl cyclase, producing cAMP (cyclic AMP).
  • cAMP acts as a secondary messenger, activating enzymes to alter biochemistry.
  • Phosphodiesterase deactivates cAMP.

Mobile Receptor Mechanism

  • Lipid-soluble hormones (e.g., fatty acids, steroids) use this mechanism.
  • These hormones can easily pass through the plasma membrane.
  • They bind to intracellular receptors.
  • This hormone-receptor complex activates enzymatic activity, initiating changes.
  • The hormone-receptor complex initiates DNA transcription.
  • mRNA is translated into proteins causing cellular biochemical changes.

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