Intracellular Fluid

ICF

• K+  140 mM
• Na+  15 mM

Extracellular Fluid

ECF

• K+  4 mM
• Na+  145 mM

K+

Na+

Ca+2

Cl-

• HPO4-
• Protein-

• K+ and negatively charged molecules such as proteins are in much greater concentration here
• neg charged proteins are synthesized here

• 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

• the membrane is polarized at -90 mV

• provides passive energy for transport of compounds across the plasma membrane
• makes cells excitable which allows for nerve impulses
• allows for muscle contraction

• 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

• 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

• non-gated
• are open all the time allowing slow flux of ions

• 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

• 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

a molecule that binds to a receptor

ex.-neurotransmitters

• open when membrane is physically moved due to physical deformation of receptors

ex.- touch receptors and temp receptors

• 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-

• 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

• time during an AP when a second stimulus cannot initiate another action potential
• at this time voltage gated Na+ channels are open and inactivated