Anterior pituitary Flashcards
What are cell that have major features of neurons but release hormones into the blood to affect non-neural tissue?
Neuroendocrine cells
What is the endocrine system?
Hormones being secreted into the blood to affect cells at a distance
What is it called when there are receptors on presynaptic cells for the transmitter that the cell releases?
Autocrine
How are hormones classified?
By their chemical structure (e.g. peptide, proteins etc)
What are the 5 different categories of hormones?
- Polypeptides
- Proteins
- Steroids
- Amines
- Thyroid hormones
Thyroid hormones are largely proteinaceous molecules. Why are the classified separately? (hint–what else do they contain)
They contain iodine
What are neuroendocrine hormones?
Chemical released into the bloodstream from a neuron
What is the first step in the synthesis of polypeptide/protein hormones? Is the protein active at this stage?
Preprohormones made from DNA translation. This is not active
What is the next step in peptide hormone synthesis after preprohormone is synthesized?
Preprohormones are cleaved to form prohormones and transferred to the golgi.
What is the next step in peptide hormone synthesis after cleavage to a prohormone and sent to Golgi?
Prehormone is packaged into a vesicle with enzymes that turn it “on”
What is the next step in prohormone synthesis after the peptide hormone is activated in the vesicle from the Golgi?
Vesicle is released via exocytosis in response to some signal
Are peptide hormones soluble? Where in the target cell, generally, do they act?
They are soluble, and act on the cell via effector cells on the membrane
What is the precursor molecule for steroid hormones? Are these stored in vesicles like peptide hormones? What is the consequence of this?
Cholesterol–not water soluble, so not stored in vesicles–just diffuse out once synthesized
Are steroid hormones stored?
No, but their precursors can be
How do steroid circulate in the blood? (hint, they are hydrophilic)
Bound to plasma proteins
Why does it take a longer amount of time for steroid hormones to be filtered from the blood via the kidneys compared to peptide hormones?
Not water soluble, and are bound to proteins. Proteins are not secreted, thus takes longer to be secreted
What are the amine hormones? (hint they are all derived from Tyrosine). Where are they synthesized/secreted?
Dopamine, epinephrine, norepinephrine
Synthesized/secreted from the adrenal medulla
How are catecholamines (amine) stored? Released?
Stored in vesicles and released via exocytosis
Are catecholamines water soluble?
Yes
What is the histological characteristics of cells that synthesize hormones (2)?
Tubular mitochondria
Large lipid stores
How are hormones specific (how do they “know” which cells to go to)? Similarly, how can the same hormone have different effects in different places?
Based on the receptors
Where in the cell do lipid soluble hormones bind?
Receptors in the cytoplasm or the cell nucleus
What are the four major types of hormone receptors?
- Ion channels
- Enzyme linked
- G-coupled
- Intracellular receptors
Where does the thyroid hormone bind/where is its receptor? What does binding allow for?
The receptor is bound on DNA constitutively. Binding stimulates the transcription of genes
Where are the receptors for testosterone/estrogen? What does binding do?
Found in the cytoplasm, and allows for binding of hormone/receptor complex to DNA
What is the pathway that insulin uses to exert intracellular effects?
Binds to an extracellular receptor, a Tyrosine kinase, that phosphorylates other proteins in a cascade
What are the two major types of negative feedback?
Physiological response-driven negative feedback
Endocrine axis- driven negative feedback
What are the three majors loops of negative feedback found in the axis-driven system?
Ultrashort
Short
Long
What is the ultrashort loop of negative feedback in the axial system?
Hypothalamus shuts itself off via hypophysiotropic factor
What is the short loop of negative feedback in the axial system?
Anterior pituitary shuts off the hypothalamus by releasing tropic hormones
What is the long loop of negative feedback in the axial system?
The target organ shuts off the hypothalamus
What is the factor that is released from the hypothalamus that causes the anterior pituitary to release hormones? What is the name of these hormones that the anterior pituitary releases, and where do they go?
Hypothalamic releasing factor
Tropic hormones, go to the effector organ
What is the classic example of positive feedback?
Ovulation
What are the 5 ways that hormones can be cleared from the blood?
- Metabolic destruction by the tissues or by enzymes in the blood
- Binding to the tissues
- Excretion by the liver into the bile
- Excretion by the kidneys in the urine
- If water soluble filtered at the kidney
Where is the hypothalamus located (besides the fact that it is beneath the thalamus)?
Floor and lateral walls of the third ventricle
The hypothalamus is a part of what part of the brain?
Diencephalon
What are the two capillary beds in the pituitary connected by?
Portal hypophysial vessel
What is the connecting structure of the hypothalamus to the pituitary?
Hypophysial stalk
The area of the hypothalamus where the portal vessels arise, and neurons from the hypothalamus secrete signals is called what?
The median eminence
What is the adenohypophysis? neurohypophysis?
Adenohypophysis = Anterior pituitary Neurohypophysis = posterior
What are the two nuclei that have their axons descend into the posterior pituitary?
Supraoptic and paraventricular nuclei
What is the hypothalamic-hypophysial tract?
Axon tracts of the paraventricular and supraoptic nuclei