Endocrine Secretion - Biology Concepts

What is an endocrine secretion? Endocrine: secretion of chemical messengers into the blood. Exocrine: secretion into a *ductal system* Example: secretion of the salivary gland or exocrine pancreas page6image60535744 Endocrinology is the *study of internal...

What is an endocrine secretion? Endocrine: secretion of chemical messengers into the blood. Exocrine: secretion into a *ductal system* Example: secretion of the salivary gland or exocrine pancreas page6image60535744 Endocrinology is the *study of internal secretions* These secretions are called *hormones\ * Hormones are produced by *ductless* glands Hormones are most often *carried to all cells* of the body by the vascular system anterior pituitary page7image58710528 Modes of Intercellular Chemical Communication 1\. Signaling through cell-cell contact 2. Autocrine\ 3. Paracrine\ 4. Endocrine Each of these forms of intercellular communication requires: 1. signaling cell\ 2. chemical signal\ 3. target cell Signaling through cell-cell contact In this example, there is a direct transfer of signaling molecules through gap junctions that connect the two cells. Example: Granulosa cells in ovarian follicles pass chemical signals to the oocyte in this way.  https://courses.lumenlearning.com/boundless-biology/chapter/signaling-molecules-and-cellular-receptors/ Signaling through cell-cell contact In this example of signaling through cell-cell contact, two cells bind to each other because they each carry complimentary cell-surface proteins. When the proteins bind to each other the interaction changes the shape of one or both proteins, which results in the transmission of a signal. In this case the NK cell is signaled to not attack the healthy cell that is recognized as self. page10image60273408 https://www.khanacademy.org/science/biology/cell-signaling/mechanisms-of-cell-signaling/a/introduction-to-cell-signaling Autocrine Example: prolactin stimulation of human breast cancer cells page11image58609312 Paracrine Example: Histamine, secreted by enterochromaffin-like (ECL) cells in the gut, stimulates nearby parietal cells to secrete HCl.  Paracrine Synaptic signaling is a type of paracrine signaling. Example: Release of neurotransmitters: signal from neuron to neuron, neuron to muscle cell, etc. page13image58681296 Endocrine Example: communication between cells of the pituitary and the thyroid gland page14image58495456 Endocrine communication The nature of endocrine communication is *chemical* Regulated hormone secretion by 'signaling cell' (i.e., signaling cell is the source of hormone)\ Blood hormone concentrations are very low\ Hormones potentially can contact all cells\ Normally not all cells in the body respond to a hormone On/In the target cells, *receptors* are present and bind the hormone with *sensitivity* and *specificity* and generate the intracellular signal  page16image41194416 Senger, 2012 Characteristics of Hormone/Receptor Interactions Sensitivity: the *minimal* hormone concentration able to elicit a cellular response. Normally a biologically relevant hormone-receptor pair has a high sensitivity, often\ within the normal range in blood hormone concentration. Specificity: the narrowness of the range of molecules that a particular receptor will be able to bind. The specificity of a hormone/receptor system is normally quite high (meaning that the range of molecules that a particular receptor can bind is very limited).