The Hypothalamus and Pituitary Flashcards
What hormones are released from the anterior pituitary glad?
TSH ACTH FSH LH GH Prolactin
What hormones does the posterior pituitary gland release?
Oxytocin Antidiuretic hormone (ADH)
What is the process of the thyroid axis?
The hypothalamus releases thyrotropin-releasing hormone (TRH). This stimulates the anterior pituitary to release thyroid stimulating hormone (TSH). This in turn stimulates the thyroid gland to release T3 and T4.
How to T3 and T4 cause negative feedback?
T3 and T4 levels are sensed by the hypothalamus and anterior pituitary, and they suppress the release of TRH and TSH. This results in lower amounts of T3 and T4. This helps to keep thyroid hormone within its normal limits.
What is the process of the arenal axis?
The hypothalamus releases CRH. This stimulates the anterior pituitary to release adrenocorticotrophic hormone (ACTH). This in turn stimulates the adrenal gland to release cortisol. The adrenal axis is controlled by negative feedback. Cortisol is sense by the hypothalamus and anterior pituitary and surpasses the release of CRH and ACTH.
What is cortisol>
Cortisol is a stress hormone. Cortisol is secreted by two adrenal glands. The release of cortisol is controlled by the hypothalamus. Cortisol is released in pulses and in response to a stressful stimulus. It has diurnal variation. Cortisol peaks in the early morning, triggering us to wake up and get going, and it is lowest in the evening.
What are the actions of cortisol in the body?
- Inhibits the immune system
- Inhibits bone formation
- Raises blood glucose
- Increases metabolism
- Increases alertness
What is the growth hormone axis?
Growth hormone releasing hormone (GHRH) is released from the hypothalamus. This stimulates growth hormone (GH) release from the anterior pituitary. Growth hormone stimulates the release of insulin-like growth factor 1 (IGF-1) from the liver
What are the functions of growth hormone?
- Stimulates muscle growth
- Increases bone density and strength
- Stimulates cell regeneration and reproduction
- Stimulates growth of internal organs
Where is Parathyroid hormone released?
Parathyroid Hormone (PTH) is released from the four parathyroid glands (situated in four corners of the thyroid gland) in response to low serum calcium. It is also released in response to low magnesium and high serum phosphate.
What is the role of parathyroid hormone?
It’s role is to increase the serum calcium concentration.
How does PTH increase the serum calcium concentration?
PTH increases the activity and number of osteoclasts in bone, causing reabsorption of calcium from the bone into the blood thereby increasing serum calcium concentration.
PTH also stimulates an increase in calcium reabsorption in the kidneys meaning that less calcium is excreted in the urine.
Additionally, it stimulates the kidneys to convert vitamin D3 into calcitriol, which is the active form of vitamin D that promotes calcium absorption from food in the small intestine.
These three effects of PTH (increased calcium absorption from bone, the kidneys and the small intestine) all help to raise the level of serum calcium. When serum calcium is high this suppresses the release of PTH (via negative feedback) helping to reduce the serum calcium level.
What is renin?
Renin is an enzyme that acts to convert angiotensinogen (released by the liver) into angiotensin I. Renin is a hormone secreted by the juxtaglomerular cells that sits in the afferent (and some in the efferent) arterioles in the kidney.
What is the role of the juxtaglomerular cells?
They sense the blood pressure in these vessels. They secrete more renin in response to low blood pressure and secrete less renin in response to high blood pressure.
What is the RAAS system? Describe the process?
Renin is an enzyme that acts to convert angiotensinogen (released by the liver) into angiotensin I. Angiotensin I converts to angiotensin II in the lungs with the help of an enzyme called angiotensin-converting enzyme (ACE).
Angiotensin II acts on blood vessels to cause vasoconstriction. This results in an increase in blood pressure. Angiotensin II also stimulates the release of aldosterone from the adrenal glands.
