Anatomy & Physiology Synapse + Action Potential Quiz Review

What is needed to complete a nerve impulse?

A Neurotransmitter is released at the gap to signal the next neuron

What is a Synapse?

A junction gap between two communicating neurons (can also be called the synaptic cleft)

What is a nerve pathway?

Nerve Impulse travels from neuron to neuron.

What is the steps of the Nerve Pathway?

• Dendrite

• Cell Body

• Along Axon

• Synapse (gap)

• Dendrite

What is a neurotransmitter? 

Chemical messengers that can carry messages from one nerve cell across a space to the next nerve, muscle, or gland and there are two different types of them. 

What is a excitatory neurotransmitter?

Increase membrane permeability, increases chance for threshold to be achieved.

What is inhibitory neurotransmitter?

Decrease membrane permeability, decrease chance for threshold to be achieved.

What is irritability? 

Respond to a stimulus and producing nerve impulse 

What is conductivity?

Transmit impulse to other neurons, muscles, or glands

What is a speed proportional to?

The size of the axon

What do myelinated axons do?

They conduct impulses faster than unmyelinated one

Grater diameter = 

faster impulse 

A nerve impulse has a

Weak electric current, like a wave

What do all cells naturally have?

Membrane potential

What is membrane potential?

Difference in charge between the inside and outside of a cell (ex. -70 mV) due to ions (ex. Na+ and K+) 

Since DNA is negative…

cells are naturally negative

What is concentration gradient?

A difference in concentration of ions on the inside versus the outside of a cell; causes ions to flow through channels to reach equilibrium 

What are voltage-gated channels? 

Require only an impulse to open (K+ and Na+ channels) 

What are sodium-potassium pumps?

Require ATP to open; pump 3 Na+ out and 2 K+ in

What is action potential?

Quick electrical messages that travel; down the axon of a neuron, reversing the charge of the axon from negative to positive: carries the impulse to the next neuron 

During resting potential…

• Na+ and K+ channels are closed 

• “Off” state 

• Inside of axon is negative (-70 mV) 

• More K+ on the inside vs outside 

• Less Na+ on inside vs. outside 

• The little bubble in the graph is at its lowest to the left 

How is the cell during depolarization?

• An impulse comes into the axon, triggering Na+ channels to open 

• Na+ rushes in! 

• Na+ is equal on the inside & outside (no gradient) 

• Rush in of Na+ ions causes the axon to be positive on the inside (+30 mV)

• The graph is kinda high going up the curve 

How is the cell during repolarization?

• Na+ channels close 

• K+ channels open and K+ rushes out 

• K+ is equal on the inside & outside (no gradient) 

• Rush out of K+ ions causes the axon to be negative on the inside (< -70 mV) 

• NO more gradients 

• Little dot on graph is going down the curve to the right 

How is the cell during Refractory Period?

• Na+ and K+ channels are closed 

• To restore concentration gradients sodium-potassium pumps open (requires ATP) 

• Na+ pumped out and K+ pumped in 

• Restore the axon to resting potential state (-70 mV) 

• Limits the number of action potentials that a given nerve cell can produce per unit of time and ensures the unidirectional propagation of the electrical impulse

• Dot on action potenial graph is under the curve completely down on the right side