Pituitary and Hypthalamic Hormones Flashcards
What is a hormone?
A substance secreted by a gland or tissue into the blood that binds to receptors in other tissues where they affect specific physiological processes.
Chemically hormones fall into 3 main categories. They are:
peptides, steroids, or amines (and their derivatives)
Insulin and growth hormone are examples of what type of hormone? (peptide, steroid, or amine)
peptide hormones
Estrogen, testosterone, and cortisol are examples of what type of hormone? (peptides, steroids, or amines)
steroids
Epinephrine and thyroxine are examples of what type of hormone? (peptide, amine or steroid)
amines
What is a neurohormone?
A subclass of hormones secreted by neurons.
Name 2 neurohormones.
Vasopressin and oxytocin
Describe the steps of peptide synthesis.
- genes encoding peptides transcribed to mRNAs 2. mRNAs translated on ribosomes to make preprohormone (which has a signal peptide) 3. Signal peptide directs transport to the endoplasmic reticulum where signal peptide is cleaved leaving a prohormone. 4. Prohormone transported to Golgi apparatus, where it is sequestered into secretory vesicles. 5. Within the vesicles, prohormone is further cleaved into the final active form of the hormone. 6. Secretion occurs when the contents of these vesicles are released.
What is preprohormone?
A peptide hormone precursor that includes a signal peptide.
What is prohormone?
A peptide hormone precursor that was a preprohormone but now has the signal peptide cleaved off. Prohormone is transported to the Golgi apparatus and is sequestered there into secretory vesicles.
What are steroid hormones synthesized from?
From cholesterol.
Where does the body get the cholesterol it needs to make steroid hormones?
It gets it from dietary cholesterol or synthesizes it de novo from acetyl coA
What are the major steroid hormones?
cortisol aldosterone testosterone (and other androgens) estradiol (and other estrogens) progesterone.
Where are cortisol and aldosterone synthesized?
adrenal cortex
Where is testosterone produced?
by the testes
Where are estradiol and progesterone synthesized?
in the ovaries
What is the basic action of hormones?
They are secreted into the blood by endocrine glands or tissues. When they reach their target tissues they bind to membrane or nuclear receptors, initiating a chain of events that ultimately results in the phsyiologic effects of the hormone.
Which hormones readily enter the target cell?
steroid hormones (testosterone, estradiol, porgesterone), thyroid hormone and vitamin D. They are all lipophilic and readily cross the lipid bilayer. Once inside the cell they bind to their nuclear receptors and intitiate gene transcription.
How to peptide hormones and catecholamines get into the cell?
They do not. They bind to membrane receptors like heteromeric G proteins, initiating a cascade of events involving generation of or inhibition of production of second messengers such as cAMP, cGMP, and IP3. These second messengers are what activate or induce transcription factors and cellular function.
What is an autocrine hormone?
A hormone that is secreted by a gland, circulates through the blood and then acts upon autocrine receptors on that same cell.
What is a paracrine hormone?
a hormone that is released from a gland and acts locally on cells near the one that released it.
Define neuroendocrine.
Neuroendocrine is the joining of both the neuro and and endocrine system. A neurotransmitter in the brain that acts on the pituitary gland in the brain is a neurohormone. The neurotransmitter response is fast. Once a hormone leaves the pituitary it is an endocrine hormone which acts much slower for a sustained effect.
What two structures in the brain regulate the function of much of the endocrine system?
The hypothalamus and the pituitary
The hypothalamus is located in the ______ _______ and is connected by the _________ to the pituitary gland.
ventral diencephalon; pituitary stalk (infundibulum)
The pituitary sits in a bony cavity in the sphenoid bone called the _____________.
sella tursica
How many lobes does the pituitary have?
- The anterior pituitary and the posterior pituitary
one lobe of the pituitary is continous with the hypothalamus, and contains axons originating from the hypothalmic nuclei. Which lobe?
Posterior
The posterior pituitary stores and secretes which 2 hormones?
ADH (vasopressin) and oxytocin
Where are oxytocin and vasopressin (ADH) synthesized?
In the supraoptic nucleus and paraventricular nucleus of the hypothalamus.
How are vasopressin (ADH) and oxytocin carried to the posterior pituitary?
By axonal transport
Which lobe of the pituitary is NOT directly connected to the hypothalamus?
The anterior pituitary
How is the anterior pituitary connected with the hypothalamus?
The anterior pituitary is conneced to the hypothalamus by the vessels of the hypophyseal portal circulation.
If not directly connected to the hyothalamus, aside from by blood supply, how does the hypothalamus work to get the anterior pituitary to release hormones?
They hypothalamus synthesizes and releases both hypothalmic releasing and inhibitory hormones that are carried through the hypophyseal portal veins to the anterior pituitary and regulate the release of trophic hormones.
What did Dr. Lumpkin mean when he said hormonal activity in the body had a ‘cascading’ effect?
Starting with the neurtransmitter that acts on the pituitary gland, the action is quick and a little bit of neurotransmitter is released to act on the pituitary. As the pituitary responds it releases a larger amount of hormone, and the action lasts longer. As the hormone released acts on the glands of the body, even more hormone is released and lasts even longer than the previous two steps. More hormone, lasting longer and long.
peptide hormones are polar or nonpolar?
polar. they cannot readily cross the lipid bilayer of the cell membrane.
What type of hormone is thyroxine? (peptide, steroid or amine)?
amine
What is unique about thyroid hormone?
It is structurally derived from the amines but it is more lipid soluble than water soluble so it crosses the cell membranes and bind to thryoid receptors in the chromatin
Name 4 hormones that the ovaries release into the body.
estrogens, progestins, inhibin, relaxin
Name 3 hormones released by the pancreatic islets.
insulin,glucagon, and somatostatin
Name 5 of the most common hormones released form the digestive tract.
gastrin, secretin, CCK, GIP, motilin
Name a hormone released by the thymus.
thymopoietin Remember, the thymus disappears in adulthood
Name 3 hormones released by the thyroid gland.
T4 (thyroxine), T3 (triiodothyronine), and calcitonin
Name the hormone released from the pineal gland.
Melatonin
Name 2 hormones released by the testes?
androgens (especially testosterone), and inhibin
What hormone is released from fat?
Leptin
Name 3 hormones released from the kidney.
erythropoietin (EPO), calcitriol, and renin
The adrenal gland is divided into 2 regions, they are:
the adrenal medulla and the adrenal cortex