Hormonal communication (endocrine system) Flashcards
What is the endocrine system?
A system of ductless glands that secrete hormones directly into the bloodstream to regulate body functions.
What are hormones?
Chemical messengers carried in the blood to target cells with specific receptors.
What is the role of the pituitary gland?
It is the master gland; it secretes hormones that regulate other endocrine glands.
What does the adrenal cortex secrete?
Steroid hormones like cortisol (stress response) and aldosterone (water/salt balance).
What does the adrenal medulla secrete?
Catecholamines like adrenaline and noradrenaline for the fight-or-flight response.
How do peptide hormones act?
They bind to cell surface receptors and trigger second messenger cascades.
How do steroid hormones act?
They enter cells, bind to nuclear receptors, and directly affect gene transcription.
What is excretion?
The removal of metabolic waste products from the body.
What are the main excretory organs?
Lungs (CO₂), kidneys (urea, ions, water), and liver (bile pigments).
What does the liver do in excretion?
It deaminates amino acids and converts ammonia to urea via the ornithine cycle.
What is the role of the kidneys in excretion?
Filter blood to remove urea, excess ions, and water, forming urine.
What happens during ultrafiltration?
Blood is filtered under pressure at the glomerulus; small molecules enter the Bowman’s capsule.
What is selective reabsorption?
Useful substances (e.g., glucose, amino acids) are reabsorbed into the blood at the proximal convoluted tubule.
What is the role of the loop of Henle?
Creates a salt gradient in the medulla for water reabsorption in the collecting duct.
How does ADH regulate water balance?
It increases collecting duct permeability to water by inserting aquaporins, promoting water reabsorption.
