SM145 Hypothalamus Physiology Flashcards
Differences between Nervous and Endocrine systems?
Nervous is faster, response declines more rapidly, and is more targeted. Endocrine is slower, response persists, and is generally widespread.
Are the pituitary hormones activated or inhibited normally? Exception? What would happen if you cut the pituitary stalk?
Activated normally. Prolactin is the exception, dopamine inhibition predominates. If you cut the stalk you see the opposite (inhibition for most, activation for PRL).
ACTH regulation?
Activated by AVP and CRH. Major stress hormone. Largely regulated by the RAAS system.
LH/FSH regulation?
Activated by GnRH
GH regulation?
Activated by GHRH, inhibited by SS. Stimulates liver/bone to produce IGF-1. Stress hormone. Levels rise during puberty growth spurt.
TSH regulation?
Activated by TRH, inhibited by SS. Stimulates thyroid to produce T3 and T4. Levels decrease in response to stress.
PRL regulation?
Stimulates breast growth. Activated by TRH and VIP, inhibited by DA (DA inhibition predominates). DA antagonists will increase PRL levels. High estrogen in pregnancy stimulates release. Stress hormone.
Characteristics of hormone release?
Varies by time of day (example: cortisol is highest in the morning and lowest at night), and release is pulsatile (rises and falls over shorter periods of time). ACTH has the “strongest” diurnal variation.
What happens if you give a continuous infusion of a hypothalamic hormone (vs. a pulsatile infusion)?
Shuts down the release of the pituitary hormones. Pulsatility is needed for proper regulation.
What do stress hormones inhibit?
Insulin release. Increase blood glucose.
What hormone stimulates the epiphyseal growth plates? What closes them?
IGF-1 stimulates, estrogen closes them.
Role of thyroid hormone, insulin, and androgens on growth?
Hypothyroid kids are stunted. Insulin deficient kids are stunted. Androgens need to be at the right level (deficient kids or kids taking hydrocortisone for asthma can both be stunted).
Menstrual cycle basics?
Estradiol rise causes surge of LH and FSH, which induces ovulation. Egg implants. If not fertilized, corpus luteum makes progesterone which suppresses estradiol, LH, and FSH, and you get menstruation.
Vasopressin actions?
Reduces urinary water excretion by promoting reabsorption in the collecting tubule. Causes insertion of aquaporins into the luminal nephron membrane. Causes less urine flow and higher urine concentration.
Pathology of very high vasopressin levels?
Increased release of Factor VIII and vWF, contraction of smooth muscle
