adrenal gland physilogy Flashcards
1. Where are the adrenal glands located?
On top of the kidneys. Also known as suprarenal glands.
- How many layers does the adrenal cortex have, and what are they?
The adrenal cortex has three layers: Zona glomerulosa, Zona fasciculata, and Zona reticularis.
- What is the composition of the adrenal medulla?
The adrenal medulla is made up of neural tissue.
- What is the role of the juxtaglomerular cells (JG cells) in response to low blood pressure?
JG cells produce renin, which acts on angiotensinogen to produce angiotensin I, leading to the formation of angiotensin II (ATII).
- What is the primary effect of ATII on the adrenal cortex?
ATII stimulates the zona glomerulosa of the adrenal cortex, activating an intracellular cascade that leads to aldosterone synthesis.
- What are the two conditions that constitute a strong stimulus for aldosterone synthesis?
Hyponatremia (low sodium levels) and hyperkalemia (high potassium levels).
- What is the role of ACTH in the stimulation of the adrenal cortex?
ACTH, produced by the corticotropes in the adenohypophysis, stimulates the adrenal cortex, particularly the zona glomerulosa, to produce aldosterone.
- What is the role of CRH in the hypothalamic-pituitary-adrenal axis?
Corticotropin-releasing hormone (CRH) is produced by the paraventricular nucleus of the hypothalamus and stimulates the release of ACTH from the adenohypophysis.
- What is the primary effect of ACTH on the adrenal cortex at the cellular level?
ACTH activates an intracellular cascade, leading to the production of aldosterone in the zona glomerulosa.
- What are the three layers of the adrenal cortex and their respective locations?
Zona glomerulosa (most superficial), Zona fasciculata (in the middle, thickest), and Zona reticularis (the deepest).
- What inhibits the synthesis of aldosterone and under what conditions is it secreted?
Atrial natriuretic peptide (ANP) inhibits aldosterone synthesis and is secreted when blood pressure is high.
- What is the role of ANP in inhibiting aldosterone synthesis?
ANP binds to specific receptors, activating a G inhibitory pathway that results in potassium efflux out of the cell.
- What is the basic unit required for the synthesis of steroid hormones in the adrenal cortex?
Cholesterol serves as the basic unit for the synthesis of steroid hormones in the adrenal cortex.
- What is the enzyme responsible for converting cholesterol to pregnenolone in aldosterone synthesis?
21-hydroxylase converts cholesterol to pregnenolone in aldosterone synthesis.
- How is cortisol transported in the bloodstream, and what proteins does it bind to?
Cortisol is transported by binding to corticosteroid binding globulin (CBG or transcortin) and sometimes to albumin, a protein synthesized by the liver.
- What is the function of sodium-potassium ATPase in the cells of the distal convoluted tubule (DCT)?
Sodium-potassium ATPase pumps 3Na+ out of the cell and 2K+ into the cell, utilizing ATP.
- What is the role of protein channels for Na+ in the luminal membrane of the DCT cells?
These channels bring Na+ from the filtrate into the cell, and from the cell, it goes into the blood in response to the hyponatremia stimulus.
- How does aldosterone influence water reabsorption in the DCT?
Aldosterone, in response to the strongest synthesis, causes “water follows sodium,” enhancing water reabsorption.
- What is the function of protein channels for K+ in the luminal membrane of the DCT cells?
These channels move potassium from the blood into the filtrate to be lost in the urine in response to the hyperkalemia stimulus.
- What are the effects of aldosterone on the distal convoluted tubule (DCT) cells at the molecular level?
Aldosterone activates specific gene sequences, leading to the production of proteins such as sodium-potassium ATPase and ion channels for Na+ and K+.
- What are the two main parts of the adrenal gland, and where are they located in the body?
The two main parts of the adrenal gland are the cortex and the medulla. They sit on top of the kidneys in the abdominal cavity below the diaphragm.
- How many layers does the adrenal cortex have, and what are their names?
The adrenal cortex has three layers: Zona glomerulosa (most superficial), Zona fasciculata (in the middle and thickest), and Zona reticularis (the deepest).
- What type of tissue makes up the adrenal cortex layers?
All layers of the adrenal cortex are mostly composed of glandular cuboidal epithelial tissue.
- What is the adrenal medulla made of, and how many layers does it have?
The adrenal medulla is made up of neural tissue and has only one layer.