Apologia Advanced Biology Module 7 Lecture 2

Front 1

depolarization

Back 1

stimulation of the neuron causes Na+ gates open allowing Na+ to rush in.

Front 2

repolarization

Back 2

+ channels close and K+ channels open causing K+ to flow out. This process returns positive charge to the area just outside the membrane, thus restoring the resting polarity.

Front 3

If the potassium channels in an axon's membrane are open, is the potential difference becoming more positive or more negative?

Back 3

The potential difference is becoming more negative. Potassium channels are open in the repolarization phase, where the potential difference is decreasing from +30 mV to -85 mV.

Front 4

At a given instant in time, an axon has a high concentration of sodium ions inside the cell and a high concentration of potassium ions outside the cell. What will happen next?

Back 4

the sodium-potassium exchange pump to move the potassium back into the cell and move the sodium back out so that the neuron is ready for another action potential

Front 5

threshold stimulus

Back 5

a stimulus is strong enough to trigger the action potential

Front 6

subthreshold stimulus

Back 6

the stimulus does not reach the threshold and will not produce an action potential.

Front 7

local potential

Back 7

when those few sodium ions got into the cell, the potential difference did change a bit

Front 8

absolute refractory period

Back 8

no matter how strong the stimulus, no action potential can occur

Front 9

relative refractory period

Back 9

the neuron is not really ready to create an action potential but, if the stimulus is strong enough, it will do so.

Front 10

unmyelinated axon

Back 10

When a Schwann cell encases several axons

Front 11

myelinated axon

Back 11

when several Schwann cells encase one axon

Front 12

continuous conduction

Back 12

Each action potential stimulates the response of the next little section of the axon.

Front 13

saltatory conduction

Back 13

When an action potential occurs on one node, it stimulates a response on the next node over. It “leaps” from one node to another

Front 14

A perfectly healthy neuron does not respond to a stimulus. Based on what you know now, there are two possible reasons for this. What are they?

Back 14

the stimulus is subthreshold or the neuron is in its absolute refractory period

Front 15

Suppose you are in a dimly-lit room and then suddenly someone shines a bright light in your eyes. What changes occur in the action potentials being sent from your eyes to your brain?

Back 15

The change is the frequency of action potentials

Front 16

Often, doctors ask you whether the pain you feel is a dull ache or a sharp pain. Thinking about what you have learned in this section of the module, what can your answer to that question tell the doctor?

Back 16

The answer to this question can help the doctor determine whether or not the nerve that the pain signal is traveling on is myelinated or unmyelinated

Front 17

pre-synaptic neuron

Back 17

first neuron in line that carries signals to the synapse

Front 18

post-synaptic neuron

Back 18

the second neuron in line to carry the signal after it has passed through the synaptic cleft.

Front 19

neuromuscular junction

Back 19

a neuron-to-muscle synapse

Front 20

synapse

Back 20

a neuron-to-neuron synapse

Front 21

inhibitory synapses

Back 21

Synapses that stop information from passing to the next neuron

Front 22

excitatory chemical synapse

Back 22

one action potential will not create an action potential on the postsynaptic neuron. several action potentials on the presynaptic neuron will be required in order to create one action potential on the postsynaptic neuron

Front 23

inhibitory synapses

Back 23

the neurotransmitter binds to receptors which open potassium channels rather than sodium channels

Front 24

temporal summation

Back 24

In an excitatory synapse, then, an action potential can be created in the postsynaptic neuron by having a single axon carrying several action potentials within a small amount of time

Front 25

spatial summation

Back 25

an action potential in the postsynaptic neuron can also be made if many axons all carry an action potential to the same neuron all at once, because the subthreshold stimuli are all coming from different points in space.

Front 26

hyperpolarization

Back 26

it goes even further away from the threshold.

Front 27

converging circuit

Back 27

It has more than one pre-synaptic neuron and one final post-synaptic neuron. As a result, the messages all go one way

Front 28

diverging circuit

Back 28

one input but, because it diverges, it connects to two different neurons and spreads thru out body

Front 29

oscillating circuit

Back 29

a neuron sends a signal along but also sends it back to itself

Front 30

after-discharge response

Back 30

it prolongs the effect of a stimulus

Front 31

At one point in the axon, there is a high concentration of potassium ions outside of the cell and a high concentration of sodium ions inside the cell. Is the neuron at rest?

Back 31

The neuron is not at rest

Front 32

At one point in the axon, there is a high concentration of sodium ions outside of the cell and a high concentration of potassium ions inside the cell. Is the neuron at rest?

Back 32

you cannot tell

Front 33

A stimulus creates a change in the potential difference between the inside and outside of the
cell, but no action potential is created. What is this called?

Back 33

subthreshold stimulus

Front 34

What is the 1st step in creating an action potential?

Back 34

Step 1 - Sodium and potassium gates are closed. Sodium ions are concentrated outside the cell, potassium ions are concentrated inside the cell

Front 35

What is the 2nd step in creating an action potential?

Back 35

Step 2 - Sodium gates open, and potassium gates begin to open. Sodium ions rush into the cell according to the dictates of diffusion.

Front 36

What is the 3rd step in creating an action potential?

Back 36

Step 3 - Sodium gates close and potassium gates fully open. Potassium rushes out of the cell according to the dictates of diffusion.

Front 37

What is the 4th step in creating an action potential?

Back 37

Step 4 - Sodium and potassium gates are closed. Sodium-potassium exchange pump brings the system back to its original state.

Front 38

What keeps an action potential on an axon from stimulating another action potential which will travel back towards the cell body?

Back 38

The absolute refractory period

Front 39

Why do myelinated axons carry action potentials faster than unmyelinated axons?

Back 39

Myelinated axons allow saltatory transmission

Front 40

When you cut yourself, you feel an instant, sharp pain followed later by a dull ache. Why do you get these two different pains, and why do they come in that order?

Back 40

The difference in pain and timing is due to the signal traveling on myelinated or
unmyelinated axons.

Front 41

If you press your finger lightly against an object, you feel a certain amount of pressure.
Pressing harder against that same object causes you to feel more pressure. What is the difference between the action potentials in these two situations?

Back 41

frequency of the action potentials.

Front 42

A signal needs to travel a long, long way in the body. It needs to have exactly the same properties at its destination as it did when it started. Should this signal be sent along a very long axon or a few shorter axons which are connected by synapses?

Back 42

a long axon should be used

Front 43

The potential difference in a postsynaptic neuron changes from -85 mV to -95 mV at the point of a synapse. What has happened?

Back 43

An inhibitory postsynaptic potential has occurred

Front 44

What can you say about the relative amounts of potassium and sodium ions outside of the membrane during an inhibitory postsynaptic potential?

Back 44

potassium ion concentration will be higher than for the resting state outside of the membrane. The sodium ion concentration will be unchanged

Front 45

Twelve action potentials are traveling down an axon in a very short time period. They reach a synapse, and the postsynaptic neuron sends only two action potentials down its axon. Is this an excitatory synapse or a inhibitory synapse?

Back 45

excitatory synapse