Problem 7 Flashcards
ghrelin
Neuropeptide which is released when the stomach is empty
Glucoseprivation
A dramatic fall in the level of glucose available to cells; can be caused by a fall in the blood level of glucose or by drugs that inhibit glucose metablosim
Lipoprivation
A dramatic fall in the fatty acids available to cells; usually caused by drugs that inhibit fatty acid metabolism
CEPHALIC PHASE
® Begins with sight, smell or thought of food and ends with food starting to be absorbed into bloodstream.
® Insulin released in anticipation of glucose arrival in blood.
® Digestive phase – Food entering
stomach causes release of gut hormones and stimulates pancreas to release insulin.
ABSORPTIVE PHASE
Period where the energy absorbed into bloodstream meets body’s immediate energy needs
Glucodetectors – Enter liver to detect glucose entering bloodstream and signal pancreas to release insulin ->Minimizes high levels of bloodborne fuels by using, storing them.
FASTING PHASE
Period where all unstored energy from previous meal has been used and body is withdrawing energy from its reserves to meet immediate energy requirements.
® High levels of glucagon and low levels of insulin in blood.
Osmometric thirst
Happens when the solute concentration of the interstitial fluid increases, draws water out of the cells and they shrink in volume
o The detectors respond to this change
Osmoreceptors
neurons whose firing rate was influenced by the level of hydration, when they shrink they firing less, located in the OVLT SFO and the supraoptic nucleus of the hypothalamus
Hypolimnetic thirst
refers to the measuring of the volume of the blood plasma (Hypovolemia)
o The kidneys recognize lack of water and secrete an enzyme renin which becomes to the enzyme angiotensinogen which then tells the kidneys to conserve water and sodium
median preoptic nucleus
a fiber bundle that connects the amygdala and anterior temporal lobe, acts as integrating system for most or all of the stimuli for osmometric and volumetric thirst
digestive behaviour
Regulatory system of the body for e.g. isotonic
system variable
A variable that is controlled by regulatory mechanisms, for example, temperature in a heating system
Set point
the optimal value of the system variable in a mechanism
Detector
In a regulatory process, a mechanism that signals when the system variable deviates from its set point
correctional mechanisms
In a regulatory process, the mechanism that is capable of changing the value of the system variable (restores the value to the set point)
Negative feedback
When the value falls below or above the given set point it signals this to the Detector
Satiety mechanisms
A brain mechanism that causes cessation of hunger and thirst, produced by adequate and available supplies of nutrients or water
o Stops the correctional mechanism and so protects the body against to much water or food
Interstitial fluid
The fluid that bathes the cells filling the space between the cells (seawater) (has to be kept at a precise limit)
Intravascular fluid (blood plasma)
the fluid found within the blood vessels (has to be kept at a precise limit)
Isotonic
The solution of both cell fluids is the balanced
Hypertonic
The characteristic of a solution that contains enough solute that it will draw water out of a cell placed in it, inhibits the function of the cell
Hypovolemia
Reduction of the volume of the blood caused by a lack of water
Brian parts involved
• The brain stem contains neural circuits that detect hunger and satiety
• The medulla receives taste information from the tongue and a variety of sensory information from the internal organs, including signals from detectors in the stomach, duodenum and stomach
all this goes to the forebrain where the eating and metabolism is regulated
Hypothalamus
o Lateral hypothalamus eating and drinking behaviour
o Ventromedial hypothalamus satiety and hunger control
Neuropeptides
signalling substance
Leptin
Produced in fat cells – Once produced, it is secreted into the bloodstream by these cells.
Signals current long-‐term energy stores in fat.
FUNCTION
-> Brain monitors leptin levels to measure and regulate body’s energy reserves in form of fat.
Ghrelin
produced by cells of the stomach and duodenum – Once produced, released into bloodstream by endocrine cells.
Provides ‘fasting’ signal – Indicates to arcuate system that digestive system is empty ® Increase appetite.
Circulating levels rise during fasting and drop after meal is eaten.
Powerful appetite stimulant.
PYY
produced in In cells of the ileum (= small intestine) and colon and then it is secreted into the circulation.
Provides rapid signal that food has been consumed, prompting arcuate system to suppress appetite.
Acts on hypothalamic appetite control mechanisms to suppress appetite.
CCK
produced in he cells of the duodenum and then it is secreted into the circulation after ingestion of food high in protein and/or fat.
Signaling molecule in the brain
Suppresses appetite via direct action on vagus nerve (cranial nerve X)
Insulin
produced in cells of the pancreas and then it is secreted into the circulation
Provides appetite controller with information about blood glucose level
Melanin-Concentrating-Hormone
produced in a system of lateral hypothalamic neurons that stimulate appetite and reduce metabolic rate.
Regulating changes
in skin
pigmentation in fish and other non-mammalian vertebrates.
Orexin
produced in system of lateral hypothalamic neurons that stimulate appetite and reduce metabolic rate.
Keeping the brain’s sleep-‐waking switch in the ‘waking’ position.
Plays role in regulation of sleep cycles
Homeostasis
Process by which the body’s substances and characteristics (e.g. temperature and glucose level) are maintained at their optimal level
