Membrane potential Flashcards
What are the four classes of neurons?
Unipolar
Bipolar
Pseudo-unipolar
Multipolar
What is the function of glial cells?
Provide support for neurons
What is RMP and how is it formed?
Potential difference across cell membrane in resting condition
Cations and anions arranged along outer and inner surfaces
What molecules have a greater concentration in ECF than ICF?
Na+
Ca++
Cl-
HCO3-
Glucose
PO2
What molecules have a greater concentration in ICF than ECF?
K+
Mg++
PO4—
SO4-
AAs
Lipids
PCO2
How does a membrane potential form?
Separation of charges across cell membrane by leak channels?
What is the Nernst equation and what does it do?
EMF (mV) = (61/z) x log(conc inside/conc outside)
EMF = electromotive force
z = electrical charge of the ion (plus or minus)
It predicts membrane potential for a single ion at 98.6 F
What is the RMP of potassium?
-94 mV
What is the RMP of sodium?
+61 mV
What is the RMP of a neuron?
-70 mV
What maintains the RMP in cells and how?
Na/K ATPase
Pumps 3 sodium out and 2 potassium in against their concentration gradients
What is the Goldman equation
CnaiPna + CkiPk + CcloPcl
EMF (mV) = -61 x log —————————————-
CnaoPna + CkoPk + CcliPcl
What is membrane potential based on when there are multiple ions?
Polarity of each ion
Permeability of each ion
Concentration of each ion inside and outside the cell
How does hypoxia affect membrane potential?
It inhibits Na/K ATPase - causes membrane potential to rise
What is a graded potential?
Local, in response to a stimulus of lesser strength
What is a catelectrotonic potential?
Electrical stimulus evoking a depolarizing response
What is a anelectrotonic potential?
Electrical stimulus that causes hyperpolarization
What are the three properties of a graded potential?
Decremental conduction
Depolarizing or hyperpolarizing nature
Summation
What are the duration and amplitude of an action potential?
1 msec
-70mV to +35mV
What are the 7 stages of an action potential?
RMP
Threshold potential
Depolarization
Overshoot
Repolarization
Hyperpolarization
RMP
What is the absolute refractory period?
Period where another stimulus does not cause another action potential, from depolarization to repolarization
What is the relative refractory period?
During hyperpolarization until back to RMP, another stimulus can result in another AP
When to sodium channels open in relation to potassium channels during an action potential?
Sodium channels open first during repolarization
Potassium channels start to open around the upper peak of the AP, as sodium channels are beginning to close
What factors make propagation faster?
Myelin sheath - saltatory conduction
Increased axon diameter
What are the two types of synapses and their main characteristic?
Chemical - synaptic cleft
Electrical - gap junctions
What are the 8 steps of communication across a chemical synapse?
AP
Voltage-gated Ca channels open
Calcium triggers exocytosis of NT
NT diffuses through synaptic cleft and binds to receptor
Triggers cell response - which is terminated by removing NT from synaptic cleft
NT can be degraded
Re-uptake of NT for presynaptic neuron
Diffusion of NT out of synaptic cleft
What is the class I chemical NT?
Acetylcholine
What are the class II NTs?
Norepinephrine
Epinephrine
Dopamine
Serotonin
Histamine
What are the class III NTs?
GABA
Glycine
Glutamate
Aspartate
What is the class IV NT?
Nitric oxide
What are the two types of NT receptor and the speed of their response?
Ligand-gated ion channel - fast
G-protein coupled - slow
What are the two postsynaptic potentials?
Excitatory postsynaptic potential (EPSP)
Inhibitory postsynaptic potential (IPSP)
What are the stages of an EPSP?
Excitatory transmitter released from presynaptic terminal into synaptic cleft
Acts on postsynaptic receptor
Na influx in postsynaptic neuron
Depolarization
Action potential generated
What are the stages of an IPSP?
Inhibitory transmitter released from presynaptic terminal into synaptic cleft
Acts on postsynaptic receptor
Cl- influx and K+ efflux of postsynaptic neuron
Hyperpolarization
What mediates IPSPs in the brain?
GABA A receptor
What are the two types of summation?
Temporal - one synapse at a time
Spatial - several synapses at the same time
