1. homestasis Flashcards
describe the homeostatic control system
controlled variable- the homeostatic variable that the system is trying to keep in a steady state
sensor- detects changes in the controlled variable
integration centre- comparison between detected level of the homeostatic variable to the set point/normal range. if difference is detected info to fix it can be sent via communication pathways
effector- the actions of the effectors restores the homeostatic variable back within normal range
what is the difference between negative and positive feedback?
negative- control system acts to make deviation from the set point smaller
positive- control system makes to act deviation from the variable bigger
what are feedforward systems and what are some examples of their responses
they respond to a change in the environment which is likely to cause a change in the homeostatic variable. they act before the controlled variable has changed to prevent it from changing.
ie physiological- smelling or thinking about food stimulates saliva
behavioural- putting on extra clothes if the weather forecast is cold
what is the osmolarity of both the ICF and the ECF?
275-300mosmol/L
what are the values for the body fluid compartments?
ECF= 1/3 of TBW–> 1/5 of ECF= plasma, 4/5 of ECF= interstitial fluid
ICF= 2/3 of tbw
which compartment is water gained and lost from first?
ECF, it is a transitional compartment
what are some functions of the plasma membrane?
-encloses contents of a cell
-regulates movements of substances in and out of the cell
-anchorage site
-protein signalling
what are the two classes of membrane protein?
integral- integrated into the membrane. transmembrane proteins are a type of integral. they cover the span of the membrane
peripheral- located on the surface of the membrane. only associated with one side of the membrane, many have important anchoring roles
what are the two circumstances required for diffusion to occur?
1- a driving force
2- the membrane must be permeable to the substrate
what is flux?
the amount of substance moving across a membrane per unit of time
how can you change the concentration of water?
adding solute lowers the water concentration
more solute added= less water concentrated
what do molecules bound my covalent bonds do in water vs molecules joint by ionic bonds?
covalent bonds= they do not dissociate in water
ionic bonds= dissociate in water ie conc= 100mmol of NaCl osmolarity= 100mosmol Na, 100mosmol Cl= 200 mosmol NaCl
charactaristics of a hyposmotic solution
less solute molecules per L
lower osmolarity
higher water concentration.
characteristics of a hyperosmotic solution
more solute particles per L
higher osmolarity
lower water concentration
water will move here as it moves to a higher osmolarity.
osmolarity vs tonicity
osmolarity describes how much stuff is in the water whereas tonicity is the effect that a solution has on the cell volume
what occurs to the cells in a hypotonic, isotonic vs hypertonic solution
hypotonic- cell would swell as water moves in. osmolarity inside is higher then outside the cell, water conc is lower inside then outside.
isotonic- cell remains the same size, no water movement
hypertonic- cells shrink as water moves out. osmolarity higher outside than inside of cell, water conc is lower
simple diffusion vs facilitated diffusion
simple- faster. moves directly across the phospholipid bilayer, flux only limited by conc gradient
facilitated diffusion- only occurs with channel or transporter. Flux limited by number of avaliable transporters.
primary vs secondary active transport
primary- directly uses energy (ATP) to maintain electrochemical gradient. Na out K in using ATP
secondary- indirectly uses energy by switching one in (against its conc gradient) and one out (with its conc gradient)
what are the three forms of endocytosis
phagocytosis- engulfing bacteria or debris
pinocytosis- solutes and water
receptor mediated endocytosis- binding of an extracellular molecule to a receptor in the plasma membrane triggers the process
