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Membrane potential is due to:
due to differential distributions of ions and charge
of nontransmitting neuron= -65 to -70 mv
- Cl- : 130 mM
- A- : 0.2 mM
- Ca: 2 mm
Principle cation outside
proteins and negative amino acids
principle anion outside
- Cl-: 13 mM
- A-: 65-100 mM
- Ca : 0.0002 mM
Principle cation inside
Principle anion inside
Even though all cells of body have membrane potential, what?
Effect depends on what?
- only neurons and muscle cells/ fibers can change theirs iin response to stimuli
- upon the type of gated ion channel that opens
What is the ballance between diffusion graident and electrical attraction?
- Na+ wants to diffisue into cell, down its concentration gradient
- K+ diffuses out of cell, down its concentration gradient
- Negative charges inside cell attract K+ back in
Explain membrane potential at rest?
- membranes more permeable to K than for Na+
- Therefore, resting MP is most influenced by K+
What does sodium-potassium pump do?
What is the net Result of MP?
- inside relatively negative compared to outside
- negative interior also results from the presence of non-diffusible anions
Explain graded potentials.
- occur at synapses on dendrites and neuronal cell bodies
- Excitatory post-synaptic potentials (EPSPs) and Inhibitory post-synapatic potentials (IPSPs)
Effect of graded potentials?
depends upn type of gated ion channel that opens
occurs if K+ or Cl- channels open
occurs if Na+ channels open (NA+ goes in)
magnitude of change depends on the strength of the stimulus
(-50 to -55 mV) if via graded potentials, a neuron reaches threshold an anciton potential is triggered
rapid change in membrane potential caused by selective opening of voltage-gated ion chanels
Action potentials are __. Explain
- all-or-none; amplitude not affected by strength of stimulus. Once it reaches threshold, it goes to completion (to 40 mV and in same pattern)
- The magnitude/ strength of the stimulus is reflected by the frequency of the AP, not the height of it
- # of APs represents strength of stimulus
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