Medical Phsiology Nerve Flashcards
Nuerons are special in that they are…
Electrically charged and can change their charge to produce impulses
Anatomy of a Neuron
- body
- axonal hillock
- axon
- synaptic butons
- mylenated axons
- dentrites
Membrane potential
Inside of the cells negative with respect to the outside
Potential = voltage = push =
Ability to do electrical work
Cells are bag if sea water containing…
Na+, Cl-, K+, Ca++
The resting potential is a result of these steps:
1) Diffusion of K+ across the membrane
2) Diffusion of Na+ across the membrane passive Na+ channels
3) Na/K ATPase pump
Passive K channels
- open all the time (not voltage-gated)
- protein channels made membrane permeable to K but not to Na
- K diffuses out along concentration gradient
The diffusion of K+ out of the cell leaves behind…
Negatively charged anionic proteins [A-], creating a cloud of negative charge on inside of membrane.
Electrochemical equilibrium
Force of the fusion pushing K out equals the negative attraction that pulls K back in, resulting in a cloud of K outside the membrane but no further net movement of K.
Membrane is _______, inside ___ when potassium alone defuses out of the membrane
Polarized: -97mV
Na+ wants to go inside so because…
- concentration difference
- negative charge inside membrane
Potassium leaks out _____
more than Sodium
100X
Less negative than normal membrane potential
Depolarized
More negative than normal membrane potential
Hyperpolarized
Movement of sodium inside depolarizes membrane slightly to…
-86mV
Electrogenic pumping by Na/K ATPase pump causes …
Polarizes membrane -4mV, bringing membrane potential back to -90mV
Action potential
Neurons send nerve impulses; is an electrical signal
Action potential works like this:
1) neurons start at rest with membrane potential at -90mV. Both Na+/ K+ gated channels closed.
2) depolarization to -70mV to -50mV causes opening of voltage gated Na channels (activation gate)
3) Na+ rushes in because of electrochemical gradient causing the membrane interior to become more positive with respect to the exterior (overshoot)
3) slowly beginning with depolarization, Na+ gate closes and K+ gates open, stopping inward positive current and allowing K+ to diffuse out. (Repolarization)
