chapter 5 Flashcards
what creates diffusion potentials?
ion concentrations and charges
nernst potential
the diffusion potential across a membrane that opposes net diffusion of a particular ion
what positive ions diffuse OUT of a cell to make it more negative?
K+
what positive ion diffuse into the cell to make it more positive?
Na+
what negative ions diffuse into the cell to make it more negative?
Cl-
efflux
leaving the cell
influx
entering the cell
what is the resting membrane potential value?
-70mV
Na+/K+ pump (ATPase pump)
3 Na+ OUT, 2 K+ IN
step 1 of membrane potentials
Na+/K+ pump occurs. K+ then leaves cell through leak channels
what is the mV value after Na+/K+ pump?
-4mV
what is the mV value after K+ leaves through leak channels?
-68mV
step 2 of membrane potentials
positive ion enters to summate to threshold
step 3 of membrane potentials
threshold is reached by Na+ in through voltage gated channels & Na+ channels close at peak
step 4 of membrane potentials
K+ channels open to start repolarization. K+ re-exits cell
step 5 of membrane potentials
hyperpolarization is reached when K+ channels close
temporal summation
2 or more presynaptic inputs arrive at postsynaptic cell in rapid succession
spatial summation
2 or more presynaptic inputs arrive at postsynaptic cell simultaneously
depolarization
process of making the membrane potential less negative by influx of positive ions
hyperpolarization
process of making the membrane potential more negative by the efflux of positive ions
threshold potential
the membrane potential where an action potential is created
overshoot
the portion of the action potential when the membrane potential is a positive value
undershoot/hyperpolarization
the portion of the action potential where the membrane potential is more negative than resting value
absolute refractory period
no matter how great the stimulus, another AP cannot be generated
relative refractory period
another AP can be generated but requires a larger stimulus
what causes a sustained hypopolarization of a cell membrane?
hyperkalemia
conduction velocity
the speed APs are conducted along a nerve or muscle fiber
saltatory conduction
the process of an AP jumping from node to node
what is the most common NT released into synaptic cleft?
ACH (acetylcholine)
types of synapses
one-to-one synapse, one-to-many synapse, excitatory postsynaptic potentials, + inhibitory postsynaptic potentials
one-to-one synapse
neuromuscular junctions
many-to-one synapse
rare, renshaw cells of spinal cord
excitatory postsynaptic potentials
cause depolarization of postsynaptic cell. glutamate/ACH
inhibitory postsynaptic potentials
cause hyperpolarization of postsynaptic cell. GABA
Chemical gradient
Concentration gradient, kinetic or thermal energy
Electrical gradient
Charges want to neutralize. The negative proteins inside the cell attract pos ions in and repel neg ions
Goldman equation
The membrane potential of an excitable membrane is determined by the nernst potentials of each of the ions that the membrane is selectively permeable to
What factors affects the Goldman equation?
The polarity of the electrical charge of each ion, the permeability of the membrane to that ion, concentration of each ion on the inside of the membrane vs the outside
Accommodation
Stuck in absolute refractory period bc the membrane does not return to resting level and Na+ channels cannot be reset
What does accommodation result in?
Slow depolarization or hypo-polarized state
Alpha-1 adrenergic receptors
For constriction of blood vessels or contraction of a smooth muscle
Beta-1 adrenergic receptors
For the heart SA node and cardiac muscle
Beta-2 adrenergic receptors
For dilation of vessels and bronchi
Small motor units
1 neuron innervates only a few muscle fibers. For fine dexterous control
Larger motor units
1 neuron innervates many muscle fibers. For gross muscle activity
