Chapter 23: The Endocrine System Flashcards
What does the adrenal cortex secrete
Aldosterone, glucocorticoids, and sex homones
What are the three layers of the Adrenal cortex, and what are their functions
The outer zona glomerulosa secretes only aldosterone, the inner zona reticularis secretes mostly androgens, and the middle zona fasciculata secretes mostly glucocorticoids.
What is the main glucocorticoid secreted by the adrenal cortex?
Cortisol
What does the adrenal medulla secrete?
catecholamines (epinephrine and norepinephrine)
What do all steroid hormones start with
cholesterol
What leads to the crossover effect
Steroid hormones have similar structures and binding sites on their receptors. This can lead one steroid to bind to a receptor for a related molecule
Explain how the body manages the crossover effect in the renal tubule
Aldosterone and cortisol both bind to MRs. The cells in the renal tubule have an enzyme that converts cortisol to a less active form with low specificity, preventing the cross-over effect.
what is the pathway for cortisol secretion called
The hypothalamic-pituitary-adrenal (HPA) pathway
What is the HPA pathway
- hypothalamic corticotropin-releasing hormone (CRH)
- This is secreted into the hypothalamic-hypophyseal portal system and transported to the anterior pituitary
- CRH stimulates release of adrenocorticotropic hormone (ACTH) from the anterior pituitary
- ACTH acts on the adrenal cortex to promote synthesis and release of cortisol
- Cortisol acts as a negative feedback signal, inhibiting ACTH and CRH secretion
What carrier protein carries cortisol
corticosteroif-binding globulin (CBG)
What is the most important metabolic effect of cortisol? How does this work?
Helps prevent hypoglycemia. When blood glucose decreases, it leads to the secretion of pancreatic glucagon (promotes glucogen and gluconeogenesis breakdown). Without cortisol, glucagon can’t respond.
What are the metabolic effects of cortisol
- promotes gluconeogenesis (generation of glucose through nutrients)
- causes the breakdown of skeletal muscle proteins (to provide substrate for gluconeogenesis)
- enhances lipolysis (same reason as above)
- supresses the immune system
- causes negative calcium balence (decreases intestinal Ca2+ absorption and increases renal Ca2+excretion.
- influences brain function
How does cortisol suppress the immune system?
preventing cytokine release and antibody production of WBC. Inhibits inflammatory response by decreasing leukocyte mobility and migration.
What is the CRH family involved in
Inflammation, decrease food intake, onset of labor
What are the two endocrine cell types in the thyroid gland
C cells- secerte calcitonin
Follicular cells- secerte thyroid hormone
Where does the synthesis of thyroid hormones take place
in the thyroid follicles. Hallow section of each follicle is filled with colloid.
Why do T3 and T4 have limited solubility in the plasma
they are lipophobic molecules.
What are the 3 things that IGFs and GH do to stimulate growth
- promote protein synthesis
- increase blood glucose levels
- Act on the bones to increase bone growth
What is required for soft tissue growth
adequate amounts of GH, insulin (by providing glucose), and thyroid hormone (interacts with GH in protein synthesis and nervous tissue development.)
What do osteoblasts do
produce enzymes and osteoids
what do osteoclasts do
secrete acid that dissolves the calcified matrix
How do osteoclasts and osteoblasts lengthen bone
osteoclasts sense damage, and then use acid to breakdown the bone. They die and then osteoblasts start rebuilding
Describe the movement of Ca2+ from the lumen of the nephron or intestine to the ECF as active, passive, facilitated diffusion, and so on.
What 3 compartments divide your total body Ca2+
- Extracellular fluid
- Intracellular CA2+
- Extracellular matrix (bone)
