Homeostasis Continued Flashcards
two states signal a need for water:
- high extracellular solute concentration stimulates
… - low extracellular volume from a loss of bodily fluids stimulates …
osmotic thirst
hypovolemic thirst
occurs when the extracellular fluid becomes too salty
this results from 1) obligatory water loss (respiration and urination) or 2) eating salty foods
- in both cases, solute concentration increases, so water Is drawn out of cells by osmosis
osmotic thirst
… in the brain (including cicumventricular organs) detect the increased concentration of extracellular fluid
osmosensory neurons
are specialized brain structures that can monitor fluid balance, due to their location next to the ventricles
circumventricular organs
salt is actually very important!
- if there was no salt and only pure water outside cells, the water would be pushed into cells and they would burst
- retaining salt in the extracellular space (and kidneys) is especially important for …
retaining water
low extracellular volume from a loss of bodily fluids stimulates … the concentration of the fluid has not changes – salt and ions are also lost
hypovolemic thirst
in blood vessels and the heart detect a drop in pressure
- the sympathetic nervous system causes arteries to constrict, and several hormone systems are activated
- the brain activates responses such as thirst and salt hunger (drinking water alone does not fix it)
baroreceptors
peptide hormone from the posterior pituitary; acts on the kidneys to slow production of urine and increase water absorption; constricts blood vessels to increase blood pressure
vasopressin (AVP)
A steroid hormone from the adrenal glands; stimulates kidneys to conserve sodium; contributes to increased salt appetite
aldosterone
chemicals required for function, maintenance, and growth of the body
nutrients
breaking down food – is controlled by the nervous system, which also anticipates future requirements
digestion
there are also mechanisms that tell us when to stop, but they can be overcome by …
social factors
is the principle sugar used for energy
glucose
is glucose stored in the liver and muscles for the short-term, a process regulated by the pancreatic hormone insulin
glycogen
when glucose levels drop, the hormone… converts glycogen back into glucose
glucagon
for longer-term storage… molecules are stored in adipose tissue
- under prolonged foods deprivation, fat can be converted into glucose and ketones, which can be used as fuel
lipid (fat)
the majority of food energy is used for… heat production, maintenance of membrane potentials, and life sustaining processes
- metabolism is tricky: you can reduce the number of calories you bring in, but your body will often reduce your metabolism as well, so your body weight may not decreases drastically
basal metabolism
the body needs … to help glucose transporters import glucose from the blood into most cells
insulin
results from the failure of insulin to induce glucose absorption
diabetes mellitus
in … diabetes, the pancreas does not produce insulin
type 1 (juvenile-onset).
… diabetes is caused by greatly reduced tissue sensitivity to insulin
- the brain can still use glucose, but the body can’t; it gets energy from fatty acids, while glucose builds up in the blood and can damage tissues
type 2 (adult-onset)
… phase of insulin release is mediated by the brain in response to seeing, smelling or tasting food
the cephalic
insulin is released again in the … phase, when food enters the digestive tract
digestive
in the … phase specialized liver cells called glucodetectors signal the pancreas to release even more insulin
absorptive