Synapse and Action Potential

Question 1

How are called synapses including the axon of a presynaptic neuron and the dendrite of another?

Answer 1

Axodendritic

Question 2

How are called synapses including the axon of a presynaptic neuron and the axon of another?

Answer 2

Axoaxonic

Question 3

How are called synapses including the axon of a presynaptic neuron and the cell body of another?

Answer 3

Axosomatic

Question 4

How are called synapses including the dendrite of a presynaptic neuron and the dendrite of a postsynaptic neuron?

Answer 4

Dendrodendritic

Question 5

What are the structures that contain neurotransmitters which will be released into the synapse?

Answer 5

Synaptic vesicle (will fuse with the membrane through exocytosis)

Question 6

How are called the larger synaptic vesicles?

Answer 6

Neurosecretory granules

Question 7

What are the presynaptic events?

Answer 7

1. Production of neurotransmitters in the soma - transport through the axon
2. Generation of action potential
3. Fusing of the synaptic vesicles with the membrane and releasing of the contents (exocytosis)

Question 8

What are ionotronic receptors?

Answer 8

receives ions within the extracellular space

Question 9

Ionotronic receptors are often paired with what?

Answer 9

neurotransmitter-gated-ion channels

Question 10

What do neurotransmitter-gated-ion channels do with ionotronic receptors?

Answer 10

In order to let the ions pass, the channel needs to be bound to a neurotransmitter

Question 11

What are metabotropic receptors?

Answer 11

activate a protein when bound to a neurotransmitter, which will influence the functioning of the neuron

Question 12

How are neurotransmitters disposed of after a communication with another neuron? (3 ways)

Answer 12

Diffusion: into the extracellular fluid
Degradation: by enzymes (ex: acetylcholine is broken down by acetylcholinesterase)
Reuptake: by transporters of the neuron that secreted the neurotransmitters at first

Question 13

What are ions?

Answer 13

Electrically charged particles present in the intracellular and extracellular fluids

Question 14

What are cations?

Answer 14

Ions that have a net positive charge

Question 15

What are anions?

Answer 15

Ions that have a net negative electrical charge

Question 16

What is diffusion?

Answer 16

process by which molecules move from an area of high concentration to an area of low concentration

Question 17

What are the concentrations of Na+ and K+ ions in and out of the neuron when it is NOT conducting an action potential?

Answer 17

Na+ is 10 times more concentrated in the extracellular fluid than in the intracellular fluid, and K+ is 20 times more concentrated in the intracellular fluid than in the extracellular fluid

Question 18

What is electrostatic pressure?

Answer 18

phenomenon by which ions are of the same charge repel each other and ions that are of opposite charge attract each other

Question 19

Anions attracted to positively charged electrode become?

Answer 19

Anodes

Question 20

Cations attracted to negatively charged electrode become?

Answer 20

Cathodes

Question 21

What is the resting membrane potential? What value does it have?

Answer 21

the difference in charge (voltage) between the inside and the outside of the neuron when not conducting action potentials
Vm = -70mV

Question 22

What is Vm?

Answer 22

Voltage across the membrane

Question 23

What is mV?

Answer 23

Millivolts

Question 24

What is the equilibrium potential?

Answer 24

the voltage across the membrane (Vm) at which the forces of electrostatic pressure and diffusion counteract each other
• Every ion has its own equilibrium potential (K+ = -90mV, Na+ = +60mV)

Question 25

How are action potentials initiated?

Answer 25

when stimulus to the neuron triggers the opening of Na+ channels

Question 26

What are stretch activated channels?

Answer 26

Na+ channels that can be activated by stretching of the membrane or the displacement of cytoskeletal elements

Question 27

What are voltage-gated Na+ channels?

Answer 27

Have voltage sensors and sensitivity filters (to only certain ions, aka Na+)
Depolarization of the membrane is detected by the voltage sensors causing the channels to open

Question 28

What is depolarization?

Answer 28

to reduce polarity (to make less negative), the inside of the neuron becomes less electrically negative relative to the outside due to Na+ influx
Cause the Na+ channels to open

Question 29

What is the activation treshold?

Answer 29

the minimum amount of depolarization that must occur for an action potential to be initiated, which is about -55 mV

Question 30

What is overshoot?

Answer 30

when the depolarization of the membrane continues well past Vm = 0mV

Question 31

What happens when Vm reaches +30mV?

Answer 31

K+ channels open and K+ ions flow outside of the neuron, causing the voltage of the neuron to repolarize.
Na+ channels close and Na+ cannot enter the neuron anymore

Question 32

What is the absolute refractory period?

Answer 32

the voltage at which further depolarization of the neuron is impossible and another action potential cannot be initiated in that neuron because Na+ channels are still closed

Question 33

What is repolarization?

Answer 33

Potassium exiting the cell, voltage across the neuron membrane drops drastically, even below the resting potential

Question 34

What is the relative refractory period?

Answer 34

period (after-hyperpolarization) where the voltage is below the resting potential and therefore another action potential is possible but more difficult to induce

Question 35

How do we reverse the concentration that we are left with after an action potential so we can start again?

Answer 35

• Sodium-Potassium pumps use an ACTIVE process to restore the original ratios (uses ATP)
Switch Na+ with K+ inside the cell

Question 36

What is the all or none law?

Answer 36

The fact that more stimulation than necessary for the neuron to be depolarized to threshold will not result in a stronger action potential (a punch on the arm vs a stroke on the arm will result in the SAME action potential)

Question 37

How is an action potential communicated through the axon?

Answer 37

During depolarization, Na+ enter the membrane and moves down the axon, which triggers the activation of voltage-gated Na+ channels (causing the depolarization of those other sections)

Question 38

What is orthodromic conduction?

Answer 38

action potentials only move from the soma to the axon terminals

Question 39

What is antidromic conduction?

Answer 39

when an action potential moves in the inverse way (to the cell body)
Can only be achieved in labs

Question 40

What is salvatory conduction?

Answer 40

At the nodes of Ranvier (breaks in the myelin); there is a concentration of Na+ channels which regenerate the action potential