Endocrine system Flashcards
Endocrine organs:
Organs that release chemical signals that circulate in the blood: Hormones and neurohormones.
Major classes of hormones:
Steroid hormones
Protein & peptide hormones
Amine hormones.
Steroid hormones:
Derived from cholesterol.
Not stored within secretory cells and are synthesized on demand.
Hormone-receptor complex:
A transcription factor that regulates the transcription of particular genes.
They regulate protein synthesis.
Protein & Peptide hormone:
Composed of amino acids.
Each P&P hormone is encoded by a gene.
After synthesis, they are modified into pre-prohormones.
Pre-prohormone:
A new synthesized structure that contains a signal peptide that directs synthesis to the endoplasmic reticulum rather than to the cytosol.
What happens if the signal peptide is removed:
The hormone becomes an inactive prohormone.
Inactive prohormone:
They are processed into active hormones within the vesicles and stored inside vesicles until they are released via exocytosis.
Receptors for protein & peptide hormone:
They are embedded in target cell membranes.
Binding activates a secondary messenger inside the target cell.
Receptors for steroid hormones:
Located in the ICF of target cells.
Signal transduction:
Binding activates events inside the cell.
EX: Protein & Peptide hormone.
Amine Hormones:
Derived from either tyrosine or tryptophan.
They are stored (in vesicles) after synthesis, and when the endocrine cell is stimulated.
What determines the strength and response of the target cell:
The concentration of the hormone in the ECF is a primary determinant.
How can you achieve a graded response:
1.) By keeping receptor number constant and changing the hormone concentration. *[more common]
2.) By changing receptor numbers and keeping hormone concentration constant.
Hormone concentration can be changed by:
1.) Altering the rate of release from endocrine cells. This normally varies.
2.) Altering the rate of degradation in the ECF. [Degradtion is normally constant].
The ECF is filled with:
Enzymes that degrade hormones.
Hormone Half-life:
A measure of hormone persistence in the ECF.
The amount of time it takes for half of the hormone molecules to be removed from the ECF.
What can affect the half-life of a hormone:
Carrier proteins can extend the half-life of proteins considerably.
Carrier proteins:
Binds to hormones in the ECF and transports them in the blood.
They prolong hormone half-life, as they protect the from degradation.
Increase the solubility of non-polar hormones in the blood.
Hypothalamus:
A small region within the inferior part of the brain.
Pituitary gland:
Divided into the anterior and posterior lobe.
What connects the hypothalamus to the pituitary gland:
The infundibulum.
Anterior lobe:
Made up of endocrine cells.
Produces 6 different hormones.
Posterior lobe:
Made up of neural tissue.
The posterior lobe consists of:
Axon terminal & capillaries associated with the axon terminal.
The cell bodies of the neurosecretory cells are located:
Within the hypothalamus and are localized in two clusters
Two clusters of the cell bodies:
Supraoptic nucleus [SON].
Paraventricular nucleus [PVN].
PVN & SON produce:
Two peptide hormones:
1.) Anti-diuretic hormones [Vasopressin]
2.) Oxytocin.
ADH & Oxytocin are released:
From the axon terminal within the posterior lobe.
ADH & Oxytocin are made up of:
9 amino acids on chromosome 20.
Direct acting hormone:
Exert their effects on non-endocrine organs.
EX: Prolactin & Growth hormone.
Tropic hormone:
Regulate hormones produced by other endocrine organs.
Growth Hormone:
Regulate metabolism & nutrient utilization.
Prolactin:
Acts on the breast.
Promotes milk synthesis.
LH and FSH affect:
Affects sex hormone and gamete production in the gonads.
Testis & Ovary.
The adrenocorticotropic hormone [ACTH] affects:
Glucocorticoid hormone production in the adrenal cortex.
Thyroid stimulating hormone:
Affects thyroid hormone production in the thyroid glands.
What regulates the hormone production in the anterior lobe:
The hypothalamus.
They are released by neurosecretory cells whose cell bodies are located in the PVN.
Hormones of neurosecretory cells that are located within the hypothalamus are:
Released into a special capillary network that drains into portal veins that carry blood directly to the anterior lobe.
How many hormones are produced in the hypothalamus:
7 hormones, each produced by different neurosecretory cells.
Each neurohormone affects the release of a specific hormone from the anterior lobe.
A high TSH level means:
There are low thyroid hormones.
