Homeostasis Flashcards
What enters a cell?
nutrients and oxygen
what exits a cell?
waste and carbon dioxide
name some systems that interact with the external environment and expend energy
nervous system, locomotor system and reproductive system
name some systems that interact with the internal environment and help to achieve homeostasis
cardiovascular, respiratory, excretory and alimentary
name some systems that control other systems
nervous system and endocrine system
why is homeostasis important?
cells function most effectively under optimal environmental conditions. basic cellular functions tend to alter their immediate environment. homeostasis operates to correct any changes in the cellular environment
what is the optimum pH for pepsin?
3
what is the optimum pH for trypsin?
7
name the 2 mechanisms of homeostasis control
feedback control and feed-forward control
how does negative feedback work?
a change in the variable activates mechanisms that alter the level of that variable so as to counteract the change
what detects changes in the core body temperature?
thermoreceptors
what part of the brain are the thermoreceptors found?
hypothalamus
what is circadian rhythm?
daily rhythm of things such as body temperature
what is feedforward control?
altering a behaviour before there is an obvious error signal. an anticipatory action
give 3 examples of anticipatory actions
stop eating before full, increasing heart rate, probably learned behaviours
what is positive feedback?
a change in a variable activates mechanism that alter the level of that variable so as to increase the change
where is positive feedback used?
blood clotting, childbirth and action potentials
what type of feedback is it when a small change is amplified and converted to a larger one?
positive feedback
what are extracellular fluids?
interstitial fluids and plasma
what is the difference between extracellular and intracellular fluids?
ionic composition
what can move between intracellular and extracellular fluids?
water and some ions
with regards to ECF and ICF what happens when we drink lots of water?
ECF volume increases and ECF osmolarity decreases
what happens if the ECF is more dilute than the ICF?
water moves from the ECF to the ICF until the osmolarities of ICF and ECF are equal. the extra water is dispersed in ECF and ICF
what is osmosis?
diffusion of water along its concentration gradient
what does hypotonic mean?
red blood cells burst in low concentrations of NaCl
what is isotonic?
neutral concentrations of NaCl
what is hypertonic?
red blood cells shrivel in high concentrations of NaCl
why does homeostasis not keep every variable at a constant level all the time?
there is a delay in operating the control systems and each variable is not maintained at the same value in different individuals
