Lecture 16- Hunger + Thirst Flashcards
Homeostasis:
Process by which substances in the body (e.g., sugar) and characteristics of the body (e.g., temperature) are maintained at an optimal level
What is:
-System behaviour
-Set point
-Correctional mechanism?
-System behaviour: variable controlled by regulatory system (heating system..)
-Set point: optimal value of system variable (near, above, below set point)
-Correctional mechanism: mechanism of regulatory process that controls regulated system, variable.
What are the 2 ways we monitor water?
- not enough water inside cells (osmometric thirst) and
- not enough blood/fluid in our circulatory system (volumetric thirst)
Relating to osmometric thirst, explain:
Isotonic solutions
Hypotonic solutions
Hypertonic solutions
Isotonic solution: similar concentrations of solute on either side of the membrane. The cell will neither gain nor lose water.
Hypotonic solution: solute is more concentrated inside the cell than out, so water will enter the cell.
Hypertonic solution: solute is more concentrated outside the cell than in, so water will leave the cell.
What solution causes cellular dehydration, and which neurons detect changes in cells size?
-Hypertonic solutions
-Osmoreceptors: (The membrane potential and release of neurotransmitter from osmoreceptor cells relates to the volume of these cells. )
What is volumetric thirst? How is thirst triggered?
-When there is not enough blood circulating in the body, which is called hypovolemia. The heart needs a certain amount of blood to keep beating.
-Kidneys monitor low blood flow, triggers hormone cascade that promotes thirst.
What is glycogen?
-A polysaccharide, often referred to as animal starch, that constitutes our short-term store of nutrients It is stored in liver and muscle cells
What is insulin?
Pancreatic hormone that facilitates
1) entry of glucose into cells of the body for immediate use
2) conversion of glucose into glycogen for short-term storage
3) storage of fatty acids in adipose tissue for long-term storage
What is glucagon
Pancreatic hormone that promotes
1) conversion of liver glycogen into sugar for immediate use
2) conversion of adipose triglycerides into fatty acids
(which will be taken up by cells of the body and converted to sugar for immediate use)
What is the difference between insulin signalling and glucagon signalling
insulin: promotes the storage of fatty acids as triglycerides in adipose tissue.
glucagon: promotes the breakdown of triglycerides into fatty acids.
What is the main factor that influences feelings of hunger?
- Empty stomach is communicated to the brain by the stomachs release of a peptide called ghrelin.
What is ghrelin, what is duodenum how does it work with ghrelin?
Ghrelin: Peptide hormone released by the empty stomach that increases eating
Duo: First portion of small intestine, attached directly to stomach. The presence or absence of food in the duodenum regulates the release of ghrelin from the stomach
What are factors that stop you feeling hungry?
-Gastric factors that swell the stomach, reduces hunger and bloating feeling.
-Regulators of the digestive process, makes the gallbladder release digestive enzymes.
When are emergency hunger circuits activated?
When a specific critical need to eat or not eat overrides energy homeostasis circuitry.
-Dangerously low blood glucose (glucoprivation)
-Dangerously low levels of fatty acids (lipoprivation)
What are the 4 emergengy cascade effects when the brain sense that it does not have enough glucose:
-Suppresses insulin secretion to keep sugar in the blood
-Triggers glucose production in the liver
-Slows energy expenditure (basal metabolic rate), halting growth and reproductive systems
-Promotes a potent and sustained feeling of hunger
