intro to physiology and pharmacology Flashcards
what 3 fluids is the body’s internal environment made up of
blood plasma, interstitial fluid and intercellular fluid
what are the 3 vital parameters that need to be controlled in the body
oxygen in blood plasma, ATP concentration in intracellular fluid and concentration of ions in all fluids
what are the main ion in extracellular fluid
higher concentration of sodium, chloride and calcium ions than in the intercellular fluid
what are the main ions in intracellular fluid
higher concentration of potassium ions
what is homeostasis
the mechanism of keeping the internal environment of the body stable, it is an active process
what is osmolality
the concentration of particles that are free in a solution measured in millimoles (mOsm)
what is a negative feedback loop
a change that brings the system back to a steady state after it is disrupted
what is the mechanism of a negative feedback loop
- Receptors detect a change in the vital parameter (input) that disrupts the steady state.
- Receptors feed into the control centre (brain: hypothalamus or brain stem) which compares the input against a set value, if the values don’t match they change their output.
- A signal such as a hormone is sent from the control centre to effector.
- The effector (muscle: skeletal, cardiac or smooth) brings about a change that restores the stable state.
what is meant by redundancy (negative feedback loop)
in a negative feedback loop there are multiple mechanisms so if one mechanism fails there is another way to ensure the system returns to steady
how do positive and negative ions move across a cell membrane
cells have a resting voltage of -60 to -70V so positive ions will move into the cell down the electrochemical gradient but negative ions need to move down their concentration gradient
what is a pore (non-gated channel)
A protein that forms a tunnel through the membrane they are used for facilitated diffusion and are always open, they are made up of multiple subunits and require an electrochemical gradient to drive movement
what is a channel (gated pore)
Tunnel with a gate that can open and close to control movement of a solute by facilitated diffusion they are also made up of multiple subunits and require an electrochemical gradient
what is a carrier
the solute has to bind to move through
used for facilitated diffusion
driven by an electrochemical gradient
it has two gates (extracellular and intercellular)
what is a pump
Like a carrier but requires energy from ATPase to allow the solute to move through
what do all channel proteins contain
- A moveable gate consisting of amino acids that shift to open/close it
- A sensor: either voltage, ligand or mechanical
- A selectivity filter: the sequence of amino acids that determines which specific ion is selected and can move through the channel
- An open channel pore that the solute moves through
what are the differences between primary and secondary active transport
- Primary: uses pumps and energy from the hydrolysis of ATP
- Secondary: uses cotransporters and exchangers, uses energy from the electrochemical gradient of another solute
what happens in cotransporters
two solutes move in the same direction, one moves down its electrochemical gradient and the other moves against it
what happens in exchangers
two solutes move in opposite directions
how is the rate of simple diffusion affected
permeability of the membrane (permeability coefficient) and the size of the concentration gradient
the more permeable the membrane and the larger the concentration gradient the faster the rate of diffusion
straight line on a graph
how is the rate of facilitated diffusion affected
number of carriers and the speed by which the carrier can cycle through the steps
the more carriers and the faster the cycle is the quicker the rate of diffusion
curved line on a graph
what is the mechanism of protein carriers
- the carrier is open to the outside and the substrate binds at a binding site
- the outer gate closes and the substrate is concluded
- the inner gate opens and the substrate exits into the inside of the cell
- the inner gate closes and the carrier can receive another substrate
why are protein carriers slow
it takes time for the gates to open and close so they can become saturated easily
what transporters does passive transport use
pores, channels and carriers
what transporters does active transport use
only carrier proteins: pumps, cotransporters and exchangers