Unit 1 - Membrane Pysiology Flashcards
All plasma membranes contain:
- lipids
- proteins
- carbohydrates
2-layers of phosolipids
Hydrophilic heads - polar
Hydrophobic tails - nonpolar
What substance maintains the fluidity of a plasma membrane?
cholestoral
fluidity allows movement of proteins
Peripheral proteins - where
appendages loosely bound to the surface of the membrane
Integral proteins
- penetrate the hydrophobic core of the lipid bilayer
- often are transmembranous
Who proposed the Fluid Mosaic Model of membrane structure?
S. Singer & G. Nelson in 1972
glycolipids
- formed by carbohydrate groups that join with lipids
- on external surface
- function as identity markers
glycoproteins
- formed by carbohydrates that join with proteins
- on external surface
- function as identity markers
Functions of Cell Membranes
- regulate passage of substances into & out of cell & between cell organelles & cytosol
- detect chemical messengers arriving at surface
- link adjacent cells together by membrane junctions
- anchor cells to EC matrix
Major functions of proteins in plasma membrane:
- transport solutes across membrane
- enzymatic activity
- signal transduction
- cell-to-cell recognition
- intercellular joining
- attachment to cytoskeleton & ECM
osmotic pressure
- a “pulling” pressure
- measure of a tendency for flow of water into a solution b/c of its relative concentration of non penetrating solutes & water
hydrostatic pressure
- pressure exerted by a standing (or stationary) fluid on an object.
- when osmotic & hydrostatic pressure are equal, osmosis will stop
hyperpolarization
a change in a cell’s membrane potential that makes it more negative. It is the opposite of a depolarization.
tonicity
measure of whether water will enter or leave a cell
What contributes to the Resting Membrane Potential (RMP)?
- 20% - Na+/K+ pump
- 80% - membrane’s great permeability (Pk+) to K+
- non-diffusibility of proteins (A-)
[diffusion!]
Na+/K+ pump
- pumps 2 Na+ out & brings in 2 K+ cells
- unequal pumping makes outside of cell more positive than inside
Nernst Equation
- calculates Equilibrium Potentials for cells
* E = 61 * log [concentration of outside/concentration of inside)
Equilibrium Potential of:
- Na+
- K+
- +61 mv
2. - 90 mv
Where are leak channels found on a neuron?
cell body
dendrites
axon
They operate at resting membrane potential
Where are CHEMICALLY GATED channels found on a neuron?
cell body
dendrites
They operate during a graded potential.
Where are VOLTAGE-GATED channels found on a neuron?
axon
They operate during an action potential.
suprathreshold stimulus
Is stronger than the threshold stimulus
subthreshold stimulus
a stimulus that fails to take the MP to the TP
Characteristics of voltage-gated Na+ channels
- found along axon
- important for action potential
- opened and closed gates
What are the states that a VG Na+ channels could be in?
- inactivated, but capable
- open/activated
- inactivated & incapable
What channels are open when the membrane is at -70 mv?
only leak channels
polarization
any time there is a - or + charge on a membrane
depolarization
membrane becoming less negative, as in an action potential
repolarization
the cell becoming more negative as it re-establishes the polarization of its membrane
hyperpolarization
membrane becoming more polarized; the inside becoming more negative than at its RMP
Which cells form the myelin sheath in the:
PNS?
CNS?
PNS - Schwann cells
CNS - oligodendrocytes
Two types of synapses. Which is there more of?
- Electrical - charge carrying ions pass between them.
- Chemical - chemical messenger transmits information one way
95% of synapses are CHEMICAL
EPSP
Excitatory Post-Synaptic Potential
- due to increased Na+ permeability
IPSP
Inhibitory Post-Synaptic Potential
- due to increased K+ or Cl- permeability
GABA
- the brains main’s inhibitory neurotransmitter
- Gamma amino butyric acid
grand postsynaptic potential (GPSP)
a composite of all EPSPs and IPSPs occurring around the same time
temporal summation
Caused by increasing the number of action potentials on an axon in a given period of time
spatial summation
Increasing the number of synapses from different neurons
absolute refractory period
- Caused by closure & inactivation of the VG Nq+ channels that opened to depolarize the membrane.
