Action Potential (AP)

What does it mean that the action potential is all or nothing?

A neuron either fires completely or doesnt fire at all.

Example of an action potential

Ex. a light switch, it's either on or not there are no in between, a neuron works the same way; If the neuron reaches the threshold (the minimum amount of stimulation), it fires an AP at full strength. If it doesn't reach the threshold, nothing happens

Ion Voltages

- Open and close to let ions (Na+ or K+) move in and out of the neuron.

- Only open when the neuron reaches a certain voltage (electrical charge)

- Their opening and closing is what creates an AP

Sodium Gates

- Use energy (ATP) 3 Na ions out and 2 K ions in

- Their job is to restore and maintain the resting state of the neuron after firing

- They keep the inside of a neuron more negative and ready to fire again

Difference Between Sodium Gates and Ion Voltages

I.V. -

- Na+ and K+ out (passive)

- Faster

- No energy required

S.G. -

- Don't create AP

- Restore

-Slower

- Energy required

- Na+ and K+ (active)

Spatial

- Multiple neurons sending signals to one neuron at the same time

- Their combined effort can push the neuron to fire

Temporal Summation

- 1 neuron sends repeated signals very quickly, causing them to build up over time until threshold is reached

Four things that can happen to a NT's that are released into the synapse (BRED)

Bind receptors on the post-synpatic neuron

Reuptake by the presynaptic neuron

Enzymes break it down

Diffusion away from the synapse

Describe the transmission of a signal from one neuron to the next

At the synapse the pre-synaptic neuron releases NT from synaptic vesicles. These bind to receptor sites on the post-synaptic neuron. Excitatory signals open Na channels, inhibit any signals do the opposite. The neuron uses summation to add all signals and if it reaches the threshold it fires.

What do receptor cells (Sensory Neurons) transduce? From what to what?

- Transduce physical energy (pressure, heat, light) into AP

- Sensory Neurons to nerves (bundles of axons) to interneurons in spinal cord to motor neurons to muscles (spinal reflex)

What do motor neurons do?

synapse with muscle fiber at terminal end

What do motor neurons release at the neuromuscular junction?

Releases acetylcholine (ACh)