C 2.2 neural signaling

1. What are the two internal communication systems?

Endocrine system + nervous system.

2. What cells transmit nerve impulses?

Neurons.

3. What are the two types of neuron fibers?

Axons (long) and dendrites (short).

4. What is resting membrane potential?

About –70 mV.

5. Why is the inside of a neuron more negative?

More positive ions outside than inside.

6. What maintains resting potential?

Sodium‑potassium pump, K⁺ leak channels, negative proteins.

7. What does the Na⁺/K⁺ pump do?

Pumps 3 Na⁺ out and 2 K⁺ in.

8. What is an action potential?

Temporary change in membrane potential enabling nerve impulse transmission.

9. What happens during depolarization?

Voltage‑gated Na⁺ channels open → Na⁺ flows in → potential rises to +40 mV.

10. What happens during repolarization?

Na⁺ channels close → K⁺ channels open → K⁺ flows out → membrane becomes negative again.

11. What is the refractory period?

Brief hyperpolarization while pump restores resting potential.

Resting:

–70 mV (Na⁺ pumped out, K⁺ pumped in).

Depolarization

Na⁺ in (–70 → +40 mV).

Repolarization

K⁺ out (+40 → negative).

Refractory

Pump resets ions.

16. What increases impulse speed?

Myelination + larger axon diameter.

17. What is saltatory conduction?

Action potential “jumps” between Nodes of Ranvier.

18. What forms the myelin sheath?

Schwann cells.

19. What is a synapse?

Junction between neurons or neuron → muscle/gland.

20. What molecules transmit signals across synapses?

Neurotransmitters.

21. What opens when an action potential reaches the presynaptic terminal?

Voltage‑gated Ca²⁺ channels.

22. What does Ca²⁺ influx trigger?

Vesicles fuse with membrane → neurotransmitter released by exocytosis.

23. What happens at the postsynaptic membrane?

Neurotransmitter binds receptors → ion channels open → potential changes.

24. How is the signal stopped?

Neurotransmitters broken down or reabsorbed.

25. What happens after acetylcholine binds?

Broken into acetate + choline.

26. What happens to choline?

Reabsorbed for recycling.

27. What is threshold potential?

About –55 mV.

28. What are local currents?

Na⁺ diffusion to adjacent axon regions → brings them to threshold → propagates action potential.

29. Why is saltatory conduction fast?

Ion channels concentrated at nodes → AP jumps → up to 1000× faster.

30. Neonicotenoids:

Bind insect acetylcholine receptors irreversibly → paralysis.

31. Cocaine:

Blocks dopamine reuptake → dopamine buildup → overstimulation.

32. What is summation?

Combined effect of excitatory + inhibitory inputs.

33. What does GABA do?

Inhibitory neurotransmitter → makes membrane more negative.

34. When does a postsynaptic neuron fire?

When excitatory input exceeds inhibitory input.

35. Pain perception:

Stimulus → sensory neuron AP → spinal cord → cortex → conscious pain.

36. Consciousness:

Emergent property from many neurons processing inputs simultaneously.