Neurophysiology

Question 1

What the ion concentrations in a cell?

Answer 1

Na+ and Cl- are high concentration outside the cell
K+ is high inside the cell

Question 2

What gradients do we have to consider for ions?

Answer 2

We have to consider both concentration gradients and electrochemical gradients.
-ex: when potassium flows out of the cell, it becomes more negative. This makes it harder for the next potassium to leave the cell.

Question 3

What is the charge inside the cell?

Answer 3

Negative

Question 4

Na+/K+ pump

Answer 4

-uses ATP as energy source
- 3 Na+ out , 2 K+ in
- you lose one particle charge
- inside keeps becoming more negative
- 10 % contribution to membrane potential

Question 5

What are leak channels?

Answer 5

-there job is to stay open so you can’t have too many
-K+ channels: 60% contribution comes from K+ channel ( number one contributor to membrane potential) leaks out
- Na+ channels: 30% contribution to membrane potential. Leaks in

Question 6

What is a patch clamp?

Answer 6

Puts electrode into the cell and another outside to measure voltage difference.
-70 mV

Question 7

Equilibrium potentials

Answer 7

Eion =(61/z) log( [ion]out/[ion]in)
Calculating equilibrium potential for each ion
Example: calculate equilibrium potential of K+
E= (61/+1) log (5mM/150mM) = -90 mV

Question 8

What is the GHK equation?

Answer 8

Considers membrane permeability to each ion. “Contribution” of ion to potential

Question 9

Changes in membrane potential

Answer 9

-Depolarization: inside of membrane becomes less negative
-Repolarization: inside of membrane becomes more negative (returns to resting)
-Hyperpolarization: membrane becomes more negative than resting

Question 10

Graded potential

Answer 10

Presynaptic stimulus comes from first neuron and travels to another post synaptic neuron where it becomes more permeable to Na+ (ligand gated channel)
-like analog signal, so they decay trying to travel really long distances
-need another system to make signal travel all the way (action potential) graded potential alone won’t work

Question 11

What is subthreshold?

Answer 11

Graded potential that is not big enough to trigger action potential

Question 12

What is suprathreshold?

Answer 12

Graded potential that is big enough to trigger action potential (open voltage gated ion channel)

Question 13

Axon hillock

Answer 13

Part of the neuron where it connects the axon and the cell body

Question 14

Conformation of voltage gated Na+ channels

Answer 14

1. At the resting membrane potential, the activation gate closes the channel
2. Depolarizing stimulus arrives at the channel. Activation gate opens
3. Influx of sodium goes through
4. Inactivation gate closes and Na+ entry stops (plug)
5. During repolarization caused by K+ leaving the cell, the two gates reset to their original positions

Question 15

Continuous conduction

Answer 15

Occurs in unmyelinated axons. Slower than saltatory conduction. Action potential is propagated and conducted along the entire length of the axon

Question 16

Saltatory Conduction

Answer 16

Occurs in axon with myelin. Action potential “jumps” to gaps in axon. Faster
-if you destroy myelin signal may not reach the end

Question 17

Refractory period

Answer 17

Time interval required to generate another action potential.
Absolute: no stimulus can trigger another action potential
Relative: only a larger-than normal stimulus can initiate a new action potential

Question 18

Axon terminal

Answer 18

are the fingers that “attach” to other nuerons

Question 19

Neurotransmitters

Answer 19

-like peptide hormones
-released by exocytosis
-bind with a receptor (can be chemically gated or ligand gated)
-can trigger second messenger cascade
-can be excitatory or inhibitory

Question 20

What is the second messenger that triggers release of neurotransmiiters?

Answer 20

Calcium (voltage gated calcium channel)
-action potential reaches axon terminal and stimulates calcium and triggers exocytosis for NT release

Question 21

Acetylcholine

Answer 21

-common NT in brain, motor neuron, and autonomic nervous system
-don’t recycle (too many)
-mostly excitatory

Question 22

Glutamate

Answer 22

-mostly excitatory
-glutamate is released when we learn new things
-problem is that the memory doesn’t last forever
-need repetition for the synapse to stay

Question 23

Norepinephrine

Answer 23

-mostly excitatory
-used in autonomic nervous system (sympathetic)
-recycled
-associated with mood, motivation, and alertness

Question 24

GABA = Gamma-Aminobutyric acid

Answer 24

-when released opens chloride channel
-primarily inhibitory
-When chloride channel is opened it flows into the cell and makes it more negative. it becomes hyperpolarized and harder to generate action potential
-sedative

Question 25

Postsynaptic Potentials (graded potential)

Answer 25

-jobs is to make the graded potential decrease or increase
-EPSP: Excitatory postsynaptic potentials (make graded potential increase)
-IPSP: inhibitory postsynaptic potentials (make graded potential decrease) ex: chloride flows in

Question 26

Temporal summation

Answer 26

sending multiple ESPS and adding them up so that it reaches the threshold and creates an action potential
-one synapse

Question 27

Spatial summation ?

Answer 27

-multiple synapse
-three ESPS are fired and are added to create action potential