Flashcards in Lecture #1 -- Hypothalamus and Pituitary Deck (67):
Dominant portion of the endocrine system?
What glands are regulated by hypoth.-pit
Somatic Growth, Lactation, Water Metabolism
Which Pit is neural?
What is the median eminence?
Upper portion of the neural stalk extending into the hypothalamus
Which Pit is not neural
What connects the hypothalamus to the A Pit
Superior Hypophyseal Artery
What six peptides come from A Pit?
Prolactin, GH, TSH, ACTH, FSH, LH
Difference between a Long Feedback Loop, Fast feedback loop, and a short feedback loop
Short -- A Pit-->Hypo
Fast -- Ultimate Hormone --> A Pit, Hypo
Long -- Ultim. Hor --> A Pit, Hypo, CNS
What type of Hor travels btw Hypo and A Pot
Releasing or Inhibiting Factors
Name the Hypothalamic releasing hormones that stimulate secretion.
CRH, TRH, GHRH, GnRH, PRH
Name the Hypothalamic releasing hormones that inhibit secretion.
Prolactin Inhibiting Hormone (Dopamine)
Describe hypothalamic releasing hormone release
Secretion in Pulses
Effects of stimulatory releasing hormones?
Act on mem receptors to stimulate the release of stored pituitary hormones
Stim synthesis of pit hormones
Stim hyperplasia/hypertrophy of target cells
Unique regulatory activity of releasing hormones?
They regulate their own receptors
Who generates ACTH? What is the hormone target?
Adrenal gland, Adipocytes, Melanocytes
Who generates TSH? What is the hormone target?
Who generates LH, FSH? What is the hormone target?
Who generates GH? What is the hormone target?
All Tissues, Liver
Who generates PRL? What is the hormone target?
Cell type with the first, second and third highest presence in the A Pit
1. Somatotroph (40-50%)
2. Corticotroph (15-20%)
3. Gonadotroph/Lactotroph (10-15% each)
High levels of thyroid hormone can inhibit...
Anterior Pituitary secretions of TSH
Why have feedback?
Restoration of homeostasis
What converts GH to somatomedins?
What do somatomedins do?
They promote somatostatin release from the hypo, thus decreasing A Pit GH release
Two factors that primarily control GH secretion
What neurotransmitter systems stimulate GHRH and/or inhibit somatostatin. (receptor)
Catecholamines (alpha2 adrenergics)
Dopamine (D1 or D2 Receptors)
Excitstory AAs (NMDA and non-NMDA receptors)
The effects of catecholamines on GH would be seen in...
In the GH ultrashort feedback loop....
GHRH and Somatostatin both regulate their own secretion
Relationship of GH and insulin in carbohydrate intake
During carbohydrate intake, GH antagonizes insulin
Blocks Glu uptake to prevent hypoglycemia.
Relationship of GH and insulin during absorptive phase?
GH secretion is inhibited to allow glucose uptake
Relationship of GH and insulin when fasting?
Antagonizes insulin, helps mediate glucose sparing
Why can't normal serum samples to be used to assess GH?
Pulsatile pattern of release
What do you do to test blood for GH then?
Measure after exercise, immediately after sleep
Measure after Insulin-induced hypoglycemia
Measurement of IGF-1 (a somatomedin) to assess GH excess
Cause of Acromegaly and Gigantism?
Eosinophilic Adenomas of Somatotrophs
Difference between a person developing acromegaly or gigantism?
Acromegaly - hypersecretion after end of body growth
Gigantism -- hypersecretion before the end of body growth
Appearance of a patient with acromegaly
Growth of cancellous bones --> protruding jaw, hickenin phalanges, growth over visceral organs
ACTH is produced by proteolytic processing of...
POMC products include...
alpha-melanocyte stimulaitng hormone
ACTH is a key regulator of....
What does ACTH do?
Reulates the adrenal cortex and synthesis of adrenocorticosteroids
What does alpha-melanocyte stimulating hormone do?
Overproduction --> Increased pigmentation
Antipyretic and Antiinflammatory
May inhibit feeding
What is Addison's Disease?
Dysfunctional Adrenal Cortex
No cortisol from zona fasiculata --> Overproduction of ACTH
Skin Color Darkens
What do beta-endorphins do?
They bind to opiate receptors, generating a runner's high
Four factors that stimulate ACTH release?
Corticotropin releasing Hormone
ADH deficiency will lead to what effect on ACTH?
Decreased ACTH release
ADH potentiates CRH at multiple levels and many vasopressinergic neurons also contain CRH, normally causing co-release
Pattern with which ACTH is released?
-- Highest in early morning
ACTH's release pattern is opposite of what hormone?
Two ways in which ACTH is regulated?
1. Cortisol inhibits hypothalamus and pituitary
2. ACTH inhibits hypothalamus
Effects of ACTH on adrenal cortex
Stimulates growth of cortex
Stimulated steroid hormone synthesis
What happens in Adrenogenital syndrome
Block of steroidogenesis, substrates shunted to testosterone
Masculinization of Female Fetus
Glycoprotein Hormones Include...
LH, FSH, TSH, and hCG
Structural similarities and differences of glycoprotein hormones
All have identical alpha subunit
beta subunits are unique
Synthesis and secretion of LH and FSH is stimulated by...
FSH secretion is controlled by...
Describe the secretion pattens of LH/FSH
LH -- biphasic (every minute, then large at the hour)
FSH -- Uniphasic
Differences in the cyclic nature of LH/FSH in males and females
Cyclic in females with LH surge at time of ovulation
Males have constant pulses to maintain testosterone
Negative feedback mechanisms for LH/FSH
- Inhibin from testes/ovaries decreases FSH
- Testosterone inhibits GnRH production from hypo and
down regulates GnTH receptors
- Progesterone suppresses ovulation
- Dopamine, Endorphin, and Prolactin inhibit GnRH release
Overproduction of prolactin via a pituitary tumor can cause...
What do you do?
Shuts off GnRH
Treat w/ Dopamine or tumor removal
LH/FSH uses what positive feedback mechanism?
Estradiol at high plasma concentration in late follicular phase stims GnRH and LH Surge --> Ovulation
How is prolactin typically controlled?
It is tonically inhibited by dopamine
Prolactin releasing hormone is...
thyrotropin releasing hormone
Roles of Prolactin
Stims Breast Dev and Lactogenesis
May help Leydigs develop
Stimulates T cell function
How is Prolactin excess assessed?
Single basal serum PRL
Elevated PRL in a non-pregnant woman indicates...
Lesion that interferes with portal blood flow
Role of oxytocin
Stimulates myoepithelial contraction in uterus+mammary
Describe an example of prolactin becoming uninhibited
Sensory Fibers --> Spine --> PVN -> Cholinergic synapses fire on oxytocin neurons and stimulate release