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ANSC 222 Exam 2 Lec 2
Cell gradients
27
Physiology
Undergraduate 4
10/11/2011

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Term

Intracellular Fluid

ICF

Definition
  • K+  140 mM
  • Na+  15 mM
Term

Extracellular Fluid

ECF

Definition
  • K+  4 mM
  • Na+  145 mM
Term
Transmembrane Gradient
Definition
concentration of a solute is higher on one side of a membrane than the other
Term
Permeable Ions
Definition

K+

 

Na+

 

Ca+2

 

Cl-

Term
Impermeable Ions
Definition
  • HPO4-
  • Protein-
Term
Outside the cell
Definition
Na+, Ca2+, Cl- are in much greater concentration here
Term
Inside the Cell
Definition
  • K+ and negatively charged molecules such as proteins are in much greater concentration here
  • neg charged proteins are synthesized here
Term
Na+/K+ ATPase
Definition
  • uses active transport of K+ against the concentration gradient
  • for every 3 Na+ out, 2 K+ come in
  • Functions: regulation of cell volume, heat production, and secondary active transport
Term
Resting Membrane Potential
Definition
  • the membrane is polarized at -90 mV
Term
membrane potential
Definition
  • provides passive energy for transport of compounds across the plasma membrane
  • makes cells excitable which allows for nerve impulses
  • allows for muscle contraction
Term
Hyperpolarized
Definition
  • membrane potential becomes more negative
  • further away from zero

cause by: a response to an IPSP;

  • increase in K+ concentration gradient
    • increase in membrane permeability to K+
    • Increase in membrane permeability to Cl-
    • decrease in membrane permeability to Na+
    • increase in extracellular Ca2+ concentrations
Term
Depolarized
Definition
  • membrane potential becomes less negative
  • moves toward zero

caused by:

  • decrease in K+ concentration gradient
  • decrease in membrane permeability to K+
  • Increase in membrane permeability to Na+ or Ca2+
  • decrease in extracellular Ca2+ concentrations
Term
Repolarized
Definition
Membrane potential returns to resting potential
Term
Leaky Channels
Definition
  • non-gated
  • are open all the time allowing slow flux of ions
Term
Voltage-gated ion channel
Definition
  • change in membrane potential causes it to open and close
  • respond to a small voltage change across the plasma membrane
  • common in nervous and muscle tissue
  • generates an action potential
Term
Ligand-gated ion Channel
Definition
  • binding of a specific ligand(neurotransmitter) causes it to open or close
  • have a trigger
  • common in tissues such as nervous and muscle tissue and glands
Term
Ligand
Definition

a molecule that binds to a receptor

ex.-neurotransmitters

Term
receptor
Definition
a protein or glycoprotein that has a receptor site to which a ligand can bind
Term
Mechanically Gated Channel
Definition
  • open when membrane is physically moved due to physical deformation of receptors

ex.- touch receptors and temp receptors

Term
Graded potentials
Definition
  • occur only in dendrites and soma by either depolarization or hyperpolarization
  • are small changes in the resting membrane potential
  • confined to a small area of the plasma membrane
  • spreads a short distance and dies out
  • varies depending on strength of stimulus
  • graded depolarization- cause by increase to MP to Na+
  • graded hyperpolarization- caused by increase in MP to K+ or Cl-
Term
Action Potential
Definition
  • generated by voltage-gated channels when membrane potential crosses a threshold, enough EPSPs reach the axon hillock and voltage-dependent Na+ channels open
  • only happens if a graded potentials' depolarization exceeds a threshold level
  • only occur in axons and axon hillock
  • all action potential have the same stregth
  • is a large change in RMP that spreads over
  • all or none response
  • frequency is directly proportional to stimulus stregth
  • regenerates itself as it travels
Term
Absolute refractory Period
Definition
  • time during an AP when a second stimulus cannot initiate another action potential
  • at this time voltage gated Na+ channels are open and inactivated
Term
Relative Refractory Period
Definition
time when a stonger-than-threshold stimulus can evoke another action potential
Term
subthreshold
Definition
graded potential
Term
threshold
Definition
a single action potential
Term
submaximal
Definition
action potential frequency increases as stimulus strength increases
Term
maximal/supramaximal
Definition
produces a max frequency of action potentials
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