Test 4 Flashcards
What is homeostasis?
Process by which body’s substances and characteristics (such as temperature and glucose level) are maintained at their optimal level
What is ingestive behaviour?
Eating or drinking
What is a system variable?
variable that is controlled by a regulatory mechanism
- Ex: temperature in a heating system
What is set point?
optimal value of the system variable in a regulatory mechanism
What is a correctional mechanism?
In regulatory process, mechanism that is capable of changing value of system variable
- Provides negative feedback: process whereby the effect produced by a correctional mechanism serves to diminish or terminate the corrective action
What is a satiety mechanism?
brain mechanism that causes cessation of hunger or thirst, produced by adequate and available supplies of nutrients or water
When does thirst occur?
- Not enough blood circulating in the body (volumetric thirst)
- There is too much salt in the blood (osmometric thirst)
What is hypovolemia?
• When there is not enough blood circulating in the body
What does low blood flow cause?
Causes the release of renin, which triggers a hormone signalling cascade that promotes thirst, among other things, by activating hypothalamic neurons near the anteroventral tip of the third ventricle (the AV3V region), where the blood brain barrier is weak
- Hormones in the blood can seep into the CSF
What is tonicity?
The relative concentration of dissolved solutes (ex: salt) on either side of a semipermeable membrane
- It is used to describe the direction and extent of water diffusion across the membrane
What is an isotonic solution?
similar solute concentrations are present inside and outside the cell
- The cell will neither gain nor lose water
What is a hypotonic solution?
solute is less concentrated outside the cell than in, so water will enter the cell
- Because only water can move, water begins to enter the cell to try to equilibrate the concentration
What is a hypertonic solution?
solute is more concentrated outside the cell than in, so water will leave the cell
- Water will leave the cell to try to dilute the solution outside the cell
What are osmoreceptors?
neurons that detect changes in cell size, which corresponds to interstitial solute concentration
- The membrane potential and release of NT from osmoreceptor cells relates to the volume of these cells
What is glycogen?
Polysaccharide referred to as animal starch
- constitutes the short-term store of nutrients
What is insulin?
Pancreatic hormone that facilitates conversion of glucose into glycogen, entry of glucose and amino acids into cells of the body, and transport of fats into adipose tissue
What is glucagon?
Pancreatic hormone that promotes conversion of liver glycogen into glucose and conversion of adipose triglycerides into fatty acids
What is a triglyceride?
Form of fat storage in adipose cells (fat cells)
- Constitutes the long-term store of nutrients
What is glycerol?
Substance (also called glycerine) derived from breakdown of triglycerides, along with fatty acids
- Can be converted by liver into glucose
What is a fatty acid?
Substance derived from breakdown of triglycerides, along with glycerol
- Can be metabolized into sugars by most cells of body except for brain
What is grehlin?
Peptide hormone released by the empty stomach that increases eating
- also produced by neurons in the brain
What is the duodenum?
First portion of small intestine attached directly to the stomach
- the presence or absence of food in the duodenum regulates the release of grehlin from the stomach
What is leptin?
A circulating hormone that is secreted by adipocytes (fat cells)
- Thought to signal the size of peripheral energy stores in the body
- As fat cells grow, there is a concomitant increase in leptin levels in the blood stream
- The leptin provides a negative homeostatic feedback signal that decreases hunger
- Exogenous administration of leptin temporarily decreases meal size in healthy people
What is glucoprovation?
Dramatic fall in amount of glucose available to cells (detected in liver and brainstem)
- Can be caused by excess insulin signalling or by drugs that inhibit glucose metabolism
- Creates intense hunger