Neurophysiology and NMJ Flashcards
Neuron
What is the input zone?
dendrites and cell body
part where incoming signals from other neurons are received
Neuron
What is the trigger zone
axon hillock
part where APs are initiated
Neuron
What is the conducting zone?
axon (1 mm to > 1 m long)
part that conducts APs in undiminishing fashion, often over long distances
Neuron
What is the output zone?
axon terminals
part that releases neurotransmitter that influences other cells
What cell types use electrical activity to perform their physiological roles?
neurons
cardiac myocytes
skeletal muscle cells
some secretory cells (ie. pancreatic 𝜷-cells)
What are excitable cells?
electrically active cells
How do excitable cells perform their physiological role?
harness difference in electrical charge between inside and outside of their cell membrane to function
Describe the different in charge between the inside and outside of excitable cells.
more negatively charged on inside than outside (0 mV outside)
electrical potential difference located immediately adjacent to cell membrane
What are the 2 initial conditions required for electrical activity?
- selectively permeable cell membrane
- differential distribution across membrane of electrically charged ions in solution (Na+ and K+)
What is diffusion?
movement of solute (ie. ion) from area of high concentration to lower concentration by random thermal movement (no added energy needed)
How do ions (charged particles) diffuse through the membrane?
FACILITATED DIFFUSION
require path through the bilayer
ion channels in membrane provide path for Na+ and K+, etc.
Why can’t ions (charged particles) diffuse directly through the membrane?
not lipid soluble
What type of process is facilitated diffusion?
passive
Describe facilitated diffusion by means of conformation change.
- molecule to be transported binds to carrier (on binding sites exposed to ECF)
- carrier changes its conformation
- binding sites are now exposed to ICF, and transported molecule detaches from carrier
What is electrical activity in excitable cells important for?
neurons
cardiac and skeletal muscle
What is the distribution of K+ and Na+ inside and outside of the membrane?
K+ inside: 150 mM
K+ outside: 5 mM
Na+ inside: 15 mM
Na+ outside: 150 mM
How do cells concentrate K+ inside, and Na+ outside the cell membrane?
Na+ - K+ ATPase
- pumps 3 Na+ out
- pumps 2 K+ in
(uses ATP –> ADP)
What is the resting membrane potential (RMP)?
-70 mV
What is E_K+ and how is it established?
-90 mV
established by relatively large net diffusion of K+ outward
What is E_Na+ and how is it established?
+60 mV
relatively small net diffusion of Na+ inward neutralizes some of the potential created by K+ alone
Do large intracellular anionic proteins diffuse across the membrane?
no
What is permeability (or conductance)?
ease with which an ion can travel across membrane
How does permeability (P) include membrane voltage (Vm)?
greater P = greater Vm
What is the relative permeability of K+ : Na+ in most cells? Why?
~ 50 : 1
greater # of open K+ channels at rest (K+ leak channels)