Exam 1: Slide 3

Question 1

Neurons

Answer 1

• cells that are specialized for the reception, conduction and transmission of electrochemical signals.
• convert electrical signals to chemical signals and then back to electrical signals.

Question 2

Electrical Energy

Answer 2

-created by the flow of charged particles through the selective plasma membrane
-flows from high to low charge or “potential”. This is just like a battery with + and – ends.
Potential is expressed in volts

Question 3

Cations

Answer 3

sodium (Na+), potassium (K+), and calcium (Ca2+)

Question 4

Anions

Answer 4

chloride (Cl-)

Question 5

LArge Proteins

Answer 5

(A-)

Question 6

Ions High Inside the Neuron

Answer 6

K+ and A-

Question 7

Ions Hight Outside the Neuron

Answer 7

Na+ , Ca2+, and Cl-

Question 8

The Resting Membrane Potential

Answer 8

• The basis of neuronal signaling is the fact that neurons are negative charged relative to the outside of the cell by about -40 to -90mV
• occurs because of a difference in how ions are distributed between the inside and outside and when they are allowed to move
• For a neuron to communicate with another neuron, this has to become more positive

Question 9

Potassium K+ and the Resting Membrane Potential

Answer 9

-essentially the only ion that moves in a resting neuron, thus the resting membrane potential is almost entirely due to these ions
-At rest, these ions have a net movement from inside of the neuron to outside
The inside of the neuron loses positive ions as a result, making the inside more negative relative to the outside

Question 10

What channels are open and which channels are closed when a neuron is in rest

Answer 10

Potassium leak channels are always open, allowing for free potassium movement
Ion channels for the remaining ions are closed at rest so the other ions cannot move.

Question 11

Voltage Gated Channels

Answer 11

– a change in the membrane potential causes the channel to open and let selective ions through

Question 12

Ligand Gated Channels

Answer 12

– a chemical binding causes the channel to open and let semi-selective ions through

Question 13

Do Voltage and Ligand Gated Channels require energy?

Answer 13

These require no energy; ions simply move based on two passive forces: concentration and electrical gradient

Question 14

Sodium Potassium Pump

Answer 14

• This active movement requires energy, usually the energy is ATP
• Neurons use this to maintain resting potential.
• pumps three sodium ions (Na+) out for every two K+ ions pumped in.
• creates a specific ionic environment for the neuron at rest
• These pumps move ions against their concentration

Question 15

Concentration Driving Force

Answer 15

Diffusion causes ions to flow from areas of high to low concentration

Question 16

Electrical Driving Force

Answer 16

causes ions to flow towards oppositely charged areas. Think “opposites attract” or “like repels like”

Question 17

Electrochemical Driving Force

Answer 17

-These two forces can “push” ions in the same direction or opposite directions, and what the ion does is a net summation of the forces

Question 18

The Nernst Equation

Answer 18

• predicts the potential (i.e. electrical force) needed to counterbalance the concentration force pushing an ion across a membrane.
• Each ion has a specific potential value (in mV), called the equilibrium potential, and based on what the potential of the overall cell is, you can predict ion movement. This is stated as Ex, where x is the relevant ion.
• takes in to account the temperate, concentrations of a given ion inside and outside of the cell, the Faraday constant and the valence (i.e. charge) of the ion into account

Question 19

The Neuron’s State

Answer 19

the sum of all the individual potentials of the ions that are moving at that moment

Question 20

The Goldman Equation

Answer 20

allows you to predict the neuronal potential with multiple ions

Question 21

Equilibrium’s of K, Na, CL

Answer 21

Potassium Ek=-94mV
Chloride Ecl= -70mV
Sodium Ena= +60mV

Question 22

Threshold Potential

Answer 22

If the neuron becomes depolarized beyond a certain potential an action potential is triggered

Question 23

Action Potential

Answer 23

a large enough change will trigger the key electrical event needed to get a neuron to signal with another neuron.

Question 24

The Receptor Potential

Answer 24

-a way for sensory neurons to “fire” an action potential.
0Ion channels on neurons will open and depolarize/hyperpolarize the neuron in response to a sensory stimuli
-This can cause the neuron to reach a threshold potential

Question 25

The Synaptic Potential

Answer 25

a way for all other neurons to produce an action potential in another neuron

Question 26

Receptor Potential Gates

Answer 26

various ligand, voltage-gated and mechanically-gated channels that let in/out different ions (Na+, K+, Ca2+, and/or Cl-)

Question 27

Synaptic Potential Gates

Answer 27

various ligand and voltage-gated channels that let in/out different ions (Na+, K+, Ca2+, and/or Cl-)

Question 28

Action Potential Gates

Answer 28

Voltage-gated Na+ channels and voltage-gated K+ channels

Question 29

EPSP

Answer 29

If the ion channels that open make the cell depolarized, it is called an excitatory post synaptic potential (EPSP)

Question 30

IPSP

Answer 30

If the ion channels that open make the cell hyperpolarized, it is called an inhibitory post synaptic potential (IPSP)

Question 31

How do EPSP/IPSP get to the axon?

Answer 31

• As these EPSPs/IPSPs occur at the dendrite, they trigger adjacent voltage gated channels to open, sending this EPSP/IPSP event down the dendrite to the axon
• With enough EPSPs summating together, they trigger voltage gated sodium channels at the axon hillocks

Question 32

How are the Action Potential’s regions distinct? What mv must the membrane be around?

Answer 32

• This region is distinct because of the massive amount of voltage gated sodium channels, and their activation causes a large change in the membrane potential that travels down the axon
• For an action potential to occur, the depolarization must cause the membrane to become around –40 mV, which is termed the threshold potential
• All-or-none . This means the neuron fires at full amplitude or not at all

Question 33

Why can action potentials only occur on the axon?

Answer 33

• Only the axon has clusters of voltage gated sodium and voltage gated potassium channels down its length
• This clustering allows for large membrane potential changes that are not possible anywhere else on the neuron

Question 34

When do voltage gated sodium channels open?

Answer 34

Voltage gated sodium channels open around -40mV (i.e. depolarization) but then have a separate mechanism that blocks the channel even though the cell is depolarized

Question 35

When do voltage gated potassium channels open?

Answer 35

Voltage gated potassium channels open around 0mV and take much longer to close

Question 36

The Undershoot Phase

Answer 36

-Because potassium channels are slow to respond to voltage and open, they similarly are slow to close as well. -The extra time potassium channels are open more than they should be takes the membrane potential past the neuronal resting membrane

Question 37

Myelin and Action Potentials

Answer 37

• exists because it allows the action potential to be generated at the node of Ranvier, and then passive charge transfer is enough to depolarize the next node.
• saltatory conduction

Question 38

Absolute Refractory Phase

Answer 38

—time when no action potentials are produced because all channels are open

Question 39

Relative Refractory Phase

Answer 39

—time when only strong stimulation can produce an action potential because the inactivation of sodium channels can be removed

Question 40

Multiple Sclerosis

Answer 40

• a immune-mediated condition that attacks myelin, with women 2-3X more likely to develop MS compared to men
• The age of onset 20-50s, average age 34 years old
• Symptoms of MS vary widely – mild symptoms to severe disability, and there is no cure
• Common symptoms include fatigue, numbness, headache, coordination problems, bladder and bowel problems, vision problems, dizziness, sexual dysfunction, pain, cognitive dysfunction, emotional changes, and spasticity.
• Relatives of those with MS have 1-3% chance of developing MS
• Identical twins have 30% chance of developing MS

Question 41

What does Multiple Sclerosis Target?

Answer 41

In particular, the myelin produced by oligodendrocytes in the CNS is the target.
Lack of myelin leads to abnormal action potential propagation and dysfunctional signaling

Question 42

Theories of Multiple Sclerosis

Answer 42

• One theory as to what causes an attack on the oligodendrocytes are T cells that recognize oligodendrocytes myelin-specific antigens.
• T cells cross the blood-brain barrier and secreter pro-inflammatory cytokines, which destroy the myelin cells

Question 43

Hodgkin and Huxley

Answer 43

Knowing the exact process of an action potential was the result of monumental studies done primarily by a pair of scientists in the 1950s

Question 44

Voltage Clamping Method

Answer 44

• hH used this method to maintain the neuron at a specific potential (i.e. voltage) while measuring changes in ionic flow (called ‘current’).
• This method allowed them to study the properties of the ion channel at any voltage/potential they wanted in order to see what causes each channel to open/close and what their properties were

Question 45

How did Hodgkins and Huxley test sodium?

Answer 45

1) To test this, they removed sodium from the outside of the neuron. Now, the concentration inside was higher than outside.
2) Instead of flowing inside the cell during depolarization, sodium should flow out down its concentration gradient. This is exactly what they found—sodium had a slight outward current with depolarization.
3) The outward current was _unaffected by changing external sodium, indicating another ion was responsible for that outward current.

Question 46

YOU GOT THIS SHIT BITCH

Answer 46

HELL YEAAAAAAAHHHHH

Question 47

Drug Proof for Potassium

Answer 47

Tetraethylammonium (TEA) blocks potassium current without blocking sodium current. When TEA is applied to during a membrane depolarization, you lose the late outward current, proving potassium is responsible.