KAAP220 Exam 3 – Endocrine Principles & Hormone Receptors

What is endocrine signaling?

Hormones enter the blood and act on target cells with matching receptors.

What is nervous-system signaling?

Neurons use electrical impulses and neurotransmitters; responses are usually rapid and targeted.

How do endocrine and nervous responses typically differ in duration?

Endocrine effects are often slower and longer-lasting; neural effects are often rapid and brief.

Why is endocrine signaling less spatially specific than neural signaling?

Hormones circulate widely in blood, but only cells with matching receptors respond.

What is an endocrine gland?

A ductless gland that releases hormones into interstitial fluid and blood.

What is an exocrine gland?

A gland that sends its secretion through a duct to a surface or lumen.

What are the three broad chemical hormone classes?

Amino-acid derivatives, peptide/protein hormones, and steroid hormones.

What are amino-acid derivative hormones made from?

Modified amino acids, commonly tyrosine or tryptophan.

Which amino-acid-derived hormones are lipid-soluble?

Thyroid hormones; many other amino-acid derivatives are water-soluble.

What are peptide hormones made from?

Chains of amino acids.

Where do water-soluble hormones usually bind receptors?

On the target cell's plasma membrane.

How do water-soluble hormones commonly affect cells?

They activate membrane receptors and intracellular second-messenger pathways.

What are steroid hormones derived from?

Cholesterol.

How are steroid and thyroid hormones transported in blood?

Usually bound to carrier proteins.

How do lipid-soluble hormones reach intracellular receptors?

They cross the plasma membrane and bind receptors in the cytoplasm or nucleus.

What is the usual effect of steroid/thyroid hormone-receptor binding?

Changes gene expression and protein production, producing cellular responses.

What is a target cell?

A cell with the specific receptor needed to respond to a hormone.

What determines whether a cell responds to a hormone?

Presence and amount of the appropriate receptor, plus the cell's signaling machinery.

What is a permissive hormone interaction?

One hormone enables another hormone to produce its full effect.

What is a synergistic hormone interaction?

Two hormones together produce a greater effect than either alone.

What is an antagonistic hormone interaction?

One hormone opposes or reduces the effect of another.

A hormone blocks another hormone's receptor effect. What interaction is this?

Antagonistic interaction.

A second hormone must be present for another to act fully. What interaction is this?

Permissive interaction.

Two hormones combine to produce a stronger response. What interaction is this?

Synergistic interaction.

Complete the lipid-soluble signaling sequence.

Blood carrier proteins → membrane diffusion → intracellular receptor → altered gene expression → cell response.

Why do lipid-soluble hormones often act more slowly?

They commonly change gene transcription and protein synthesis.

Why do water-soluble hormones not usually cross the lipid bilayer directly?

They do not readily pass through the hydrophobic membrane core.

What is receptor specificity?

Only cells with compatible receptors respond to a particular hormone.