Lecture 28 - Chapter 16 - Endocrinology Flashcards
What is the difference between endocrine and exocrine glands?
- Endocrine glands are duct-less that produce chemical messengers called hormones.
- Exocrine have ducts that carry secretion to membrane surface. They produce nonhormonal substances like : sweat and saliva
The hypothalaums is a neuroendocrine organ. What does that mean?
That is has some endocrine and exocrine functions.
Besides the hypothalamus, what other organs/tissues produce hormones?
- Adipose cells
- Thymus
- Cells in walls of small intestine
- Stomach
- Kidneys
- Heart
BLANK are long distance chemical signals that travel in the blood or lymph.
Hormones
What are the two classes of hormones?
- Amino acid-based (Oxytocin & ADH)
- Steroids (made from cholesterol; they’re gonadal and adrenocortical hormones)
Hormones will only affect cells that have a receptor for a specific type of hormone. What is the hormone action on target cells? What happens to a cell once a hormone binds to its hormone receptor?
Hormone A will interact with receptor A. Hormone A will NOT interact with receptor B
Possibilities are:
* Alter plasma membrane permeability and/or membrane potential by opening or closing ion channels
* Stimulate synthesis of enzymes or other proteins
* Activate or deactivate enzymes
* Induce secretory activity
* Stimulate mitosis
Hormones act in one of two ways, depending on their chemical nature and receptor location. What are the two ways?
- Water-soluble hormones (all amino-acid based hormones except thyroid hormones)
* Act on plasma membrane receptors
* Act via G-protein secondary messengers
* CAN NOT ENTER THE CELL - Lipid-soluble hormones
* Act on intracellular receptors that directly activate genes
* CAN ENTER THE CELL
What is the main secondary-messenger system for amino-acid based hormones?
Cyclic AMP
Image of Lipid-soluble hormones (Steroid and Thyroid hormones) acting on intracellular receptor.
Blood levels of hormones are controlled by negative feedback systems. What does this mean?
Increased hormone effects on target organs can inhibit further hormone release.
What causes hormones to be released?
Two ways
- Endocrine gland stimuli
- Nervous system modulation
Endocrine gland stimuli can be triggered by three different ways. What are they?
- Humoral stimuli: changing blood levels of ions and nutrients directly stiumlate secretion of hormones
- Neural stimuli: nerve fibers stimulate hormone release (Sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines)
- Hormonal stimuli: hormones stimulate other endocrine organs to release their hormones
What is the hypothalamic-pituitary-target?
This involves the hormonal stimuli of endocrine glands.
Hormones from final target organs inhibit the release of anterior pituitary hormones.
Without this, hormones will keep sending a positive feedback loop to the anterior pituitary. This tells it to stop sending out the hormone.
What is the nervous system modulation?
- The nervous system can make adjustments to hormone levels when needed
- Can override normal endocrine controls (Ex. under severe stress, hypothalamus and sympathetic nervous system override insulin to allow blood glucose to increase aka prepare for fight or flight)
Like we mentioned, hormones will only bind to their specific target cell receptors. But there are three factors that determine if the hormone will actually activate the target cell. What are the three factors?
- Blood levels of hormone
- Relative number of receptors on/in target cell
- Affinity (strength) of binding between receptor and hormone
Image of comparison between Lipid and Water soluble hormones
Oxytocin and ADH are each made up of nine amino acids but they differ in two of them. What are the two amino acids that are different?
Image of Oxytocin and ADH comparison
