Endocrine System Chapter 18 Flashcards

Study Notes

Homeostasis & Negative Feedback

Negative feedback stabilizes systems by decreasing function in response to stimuli, crucial for homeostasis.
Example: In the hypothalamo-pituitary axis, ACTH inhibits CRH release to maintain cortisol equilibrium.
Cortisol from adrenal cortex inhibits ACTH from the pituitary and CRH from the hypothalamus to prevent excessive production.
Feedback inhibition is essential for controlling hormone levels.

Nervous vs Endocrine System

Both systems signal effector tissues to maintain homeostasis but differ in speed and duration.
Nervous system is fast, short-lived, and utilizes electrical impulses targeting specific cells.
Endocrine system is slower, has longer effects, and communicates through hormones released into the bloodstream.

Major Organs/Tissues of the Endocrine System

Includes the hypothalamus, pituitary gland, thyroid, adrenal glands, pancreas, pineal gland, parathyroid glands, and thymus.

Hormones

Chemical substances produced by cells and released into the blood, affecting distant cells or organs.

Target Cell

Defined as cells with receptors for specific hormones, drugs, or signaling molecules.

Types of Cell Communication

Direct communication: Via gap junctions linking adjacent cell cytoplasm.
Paracrine communication: Chemical messengers transferring information within a single tissue.
Synaptic communication: Through neurotransmitters across synaptic clefts.
Endocrine communication: Hormones released into extracellular space and absorbed into the bloodstream; target cells must have corresponding receptors.

Hormone Types

Peptide hormones: Chains of amino acids, often synthesized as inactive prohormones that convert to active form post-secretion.
Amine hormones: Small molecules related to amino acids.
Lipid hormones: Two classes—eicosanoids (from arachidonic acid) and steroid hormones (from cholesterol).

Hormone Communication Mechanisms

Peptide and amine hormones typically bind to surface receptors, whereas steroid hormones pass through the cell membrane to bind to intracellular receptors.

Agonists and Antagonists

Agonist: A chemical that binds to a receptor activating it to produce a biological response.
Antagonist: Blocks the action of agonists.
Inverse agonist: Produces an opposite action to that of the agonist.

Up-Regulation vs Down-Regulation

Up-regulation: Increase in cellular components such as receptor numbers.
Down-regulation: Decrease in receptor numbers, reducing cell sensitivity to hormones or neurotransmitters.

Endocrine Reflex

Concept refers to the automatic response of the endocrine system to internal changes, maintaining homeostasis.

Description

Test your knowledge of the endocrine system with these flashcards from Chapter 18. Explore concepts like homeostasis and negative feedback while identifying examples within the endocrine framework. Perfect for quick reviews and deeper understanding.