1. The central nervous system consists of ______.
A. the brain and motor nerves.
B. the brain and sensory nerves.
C. the brain and spinal cord.
D. the motor and sensory nerves.
E. the spinal cord and all nerves.

2. The sympathetic division of the nervous system ______.
A. controls voluntary motor activity.
B. conserves energy.
C. mobilizes body systems.
D. promotes non-emergency functions.
E. includes the sensory nerves.

3. The ________ nervous system carries brain
and spinal cord signals to other organs.
A. autonomic
B. peripheral
C. central
D. craniospinal
E. efferent

4. ___________ 6
4. ___________
___________ 5

5. Membrane Potentials What is a Membrane Potential? Ions in Neurons
Resting Membrane Potential

6. What is a Membrane Potential?
Separation of charges across a cell membrane.
Stated more simply…
Difference in number of cations and anions across a membrane
Membrane + - + - + - + -

7. Charge Separation in a Battery
Membrane potential is analogous to a battery
Battery sends electrical signal down a wire
Neuron sends electrical signal down an axon

8. Neurons have a Membrane Potential
IN CELL OUTSIDE CELL PERMEABILITY
Sodium (Na+) mM 150 Mm

9. Neurons have a Membrane Potential
IN CELL OUTSIDE CELL PERMEABILITY
Potassium (K+) mM mM

10. Neurons have a Membrane Potential
IN CELL OUTSIDE CELL PERMEABILITY
Protein (A-) mM mM

11. Neurons have a Membrane Potential
iNside = Negative
Outside = POsitive

12. And now for some review…
Oh no!!!! Not diffusion again!! AGHHHHHH!!!!!!

13. Diffusion Across a Concentration Gradient
High
Low
Homogeneous
Time 1
Time 2

14. Membrane Potentials What is Membrane Potential? Ions in Neurons
Resting Membrane Potential

15. Plastics Make it Possible!

16. Ions
Plastics Make it Possible!
Ions

17. Ion Diffusion in Neurons
Passive Channel

18. Ion Diffusion in Neurons
Passive Channel
2. Voltage-gated Channel

19. Diffusion of Na+ through Membranes
Low Na+
High Na+
Which way will Sodium move?

20. Diffusion of Na+ through Membranes
Low Na+
High Na+
Ion movement based on concentration gradient

21. Diffusion of Na+ through Membranes
Low Na+ X
High Na+
Ion movement based on concentration gradient

22. Diffusion of Na+ through Membranes
Na+ Ion Channel
Low Na+
High Na+
+60 mV
Ion movement based on concentration gradient

23. Diffusion of Na+ through Membranes
Na+ Ion Channel
Positively charged substances other than Na+ are in the cell
Low Na+
High Na+
+60 mV
Ion movement based on concentration gradient

24. Diffusion of Na+ through Membranes
Na+ Ion Channel
Positively charged substances other than Na+ are in the cell
Low Na+
High Na+
+60 mV
Inward concentration gradient counterbalanced by the outward electrical gradient
Ion movement based on concentration gradient
Ion movement based on electrical gradient

25. Diffusion of K+ through Membranes
High K+
Low K+
Which direction will Potassium move?

26. Diffusion of K+ through Membranes
High K+
Low K+
Ion movement based on concentration gradient

27. Diffusion of K+ through Membranes
High K+ X
Low K+
Ion movement based on concentration gradient

28. Diffusion of K+ through Membranes
K+ Ion Channel
High K+
Low K+
-90 mV
Ion movement based on concentration gradient

29. Diffusion of K+ through Membranes
K+ Ion Channel
As K leaves it creates a negative charge that pulls it back in.
High K+
Low K+
-90 mV
Ion movement based on concentration gradient

30. Diffusion of K+ through Membranes
K+ Ion Channel
As K leaves it creates a negative charge that pulls it back in.
High K+
Low K+
-90 mV
Outward concentration gradient counterbalanced by the inward electrical gradient
Ion movement based on concentration gradient
Ion movement based on electrical gradient

31. Concurrent Diffusion of Na+ and K+
High K+
Low K+
Low Na+
High Na+

32. Concurrent Diffusion of Na+ and K+
High K+
Low K+
Low Na+
High Na+

33. Concurrent Diffusion of Na+ and K+
High K+
Low K+
Low Na+
High Na+
K+ exerts dominating effect on RMP (greater permeability)

34. Concurrent Diffusion of Na+ and K+
High K+
Low K+
Low Na+
High Na+
K+ exerts dominating effect on RMP (greater permeability)
Na+ neutralizes some of the potential created by K+

35. Concurrent Diffusion of Na+ and K+
High K+
Low K+
Low Na+
High Na+
Resting Membrane Potential (RMP) = -70 mV
K+ exerts dominating effect on RMP (greater permeability)
Na+ neutralizes some of the potential created by K+

36. Membrane Potentials What is Membrane Potential? Ions in Neurons
Resting Membrane Potential

37. Movement of Na+ and K+ at RMP
Na+ and K+ are not at equilibrium

38. Movement of Na+ and K+ at RMP
Na+ and K+ are not at equilibrium
Both move DOWN concentration gradient

39. Movement of Na+ and K+ at RMP
Na+ and K+ are not at equilibrium
Both move DOWN concentration gradient
Why doesn’t intracellular K+ concentration continue to fall?

40. Movement of Na+ and K+ at RMP
Na+ and K+ are not at equilibrium
Both move DOWN concentration gradient
Why doesn’t intracellular K+ concentration continue to fall?
Why doesn’t intracellular Na+ concentration continue to rise?

41. Sodium-Potassium Pump
Counterbalances diffusion of Na+ and K+
Diffusion
Na+
Outside
Inside K+

42. Sodium-Potassium Pump
Counterbalances diffusion of Na+ and K+
No net movement of Na+ and K+
Diffusion
Na+
Outside
Inside K+

43. Ion Movement through Resting Neurons
Sodium pumped OUT

44. Ion Movement through Resting Neurons
Sodium pumped OUT
Potassium pumped IN, but diffuses out easily

45. Ion Movement through Resting Neurons
Sodium pumped OUT
Potassium pumped IN, but diffuses out easily
Sets up Ions that are ready to move

46. Summary
Charge separation between the inside and outside of a neuron, referred to as a membrane potential.
Resting membrane potential (RMP) caused by concentration of Na+, K+, and protein anions.
At rest, neurons have a RMP of -70 mV.
Neuron will stay at RMP until stimulated, creating an Action Potential