Electrophysiology

Question 1

A cation will leave a … potential within the cell as it leaves.
An anion will leave a … potential within the cell as it leaves.

Answer 1

A cation+= - Diffusion potential
An anion- = +diffusion potential

Question 2

Nernst Potential Definition and Equation

Answer 2

The greater the imbalance of the concentrations on the two sides of the cell membrane= the greater the potential has to be to prevent additional net diffusion.

The ions are Na,K, Cl.

EMF: Electromotive Force Z: Electrical Charge K+ is +1

Sign of the potential is positive (+) if the ion diffusing from inside to outside is a negative ion and negative (−) if the ion is positive

Question 3

Goldman Equation

Answer 3

This is used to calculate the diffusion potential when the membrane is permeable to several different ions!

C=Concentration P=permeability i= in o=out

Question 4

~~~

```What is the normal membrane potential difference in a nerve fiber?

Answer 4

94 millivolts

Question 5

What does the Na/K pump do to the membrane potential?

Answer 5

-86 +-4(continous acting)= **-90millivolts

Question 6

Electrogenic Na/K pump, what are the values for three Nas out and 2 Ks in?

Answer 6

Question 7

What’s special about Ks ions and membranes?

Answer 7

K+ leaks! Even in a resting cell. 100x more permeable to K than to Na.

Question 8

Three Stages of Neuron Potential

Answer 8

1.Resting at -90 millivolts
2.Depolarization (Na comes in the cell)
3.Repolarization (Na channels begin to close and K channels open to a greater degree).

Question 9

Nerve/Muscle Impulse

Answer 9

Transmission of the depolarization process along a nerve/muscle fiber

Question 10

What is the threshold for stimulation?

Answer 10

-55 milivolts
*All or nothing process! The ratio of action potential to threshold for excitation but be >1. Called a safety factor.

Question 11

What’s different in the heart in regard to action potentials?

Answer 11

The heart muscle has L-type (slow) sodium channels that **prolong **depolarization.

Question 12

Average nerve trunk contains about twice as many …fibers to …fibers.

Answer 12

Average nerve trunk contains about twice as many unmyelinated fibers to myelinated fibers.

Question 13

What do schwann cells deposit?

Answer 13

Sphingomyelin- electrical insulator that decreases ion flow through membrane

Question 14

Saltatory Conduction

Answer 14

Action potentials only occur at Nodes of Ranvier. Increases speed, conserves energy.

Question 15

Velocity of Conduction in Nerve Fibers

Answer 15

0.25 m/sec (small,unmyel fibers)
**100 m/sec **(large myelinated fibers)

Question 16

Negative vs Positive electric stimuli

Answer 16

decreases/ increases potential across membrane and depolarizes/repolarizes

Question 17

What three ways can excitation of an action potential occur?

Answer 17

1.Mechanical
2.Chemical
3.Electrical Stimuli

Question 18

Absolute refractory

Answer 18

Period during which a second action potential cannot be elicited, even with a strong stimulus

Question 19

Relative Refractory

Answer 19

Period during which the muscle is more difficult to excite than normal but nevertheless can be excited by a very strong excitatory signal

Question 20

Example of chemical/neurotransmitter

Answer 20

Ach, Glutamata, Epinephrine,etc

Question 21

Gap Junctions

Answer 21

Allow free movement of ions from the interior of one cell to the interior of the next cell.
Smooth muscle fibers and cardiac muscle fibers.
Bidirectional transmission: helps coordinate activities of large groups of interconnected neurons.

Question 22

What does the presynaptic terminal have?

Answer 22

Transmitter vesicles and the mitochondria.

Question 23

What do vesicles contain?

Answer 23

Excitatory or inhibitory neurotransmitters

Question 24

Mitochondria do what in the presynaptic term?

Answer 24

Provide ATP for synthesizing new transmitters

Question 25

What type of channels are found in the presynaptic terminals?

Answer 25

Voltage gated Ca2+ channels, that open to allow Ca to flow in where action potential runs through. Quantity of neurotransmitter release is directly proportional to the numbers of voltage gated calcium channels.

Question 26

Ionotropic postsynaptic receptors

Answer 26

Directly open ion channels via ligand binding.
Open and close quickly.
Cation channels= excite neuron.
Anion Channels= inhibit neuron.

Question 27

Metabotropic Postsynaptic Receptors

Answer 27

second messenger system
Prolonged response (memory).
Example: G-protein activates cAMP or cGMP.

Question 28

Excitatory* Post Synaptic* Potentials (EPSP)

Answer 28

Na channels open, depressed conduction through Cl &/or K channels, and either excites cell activity, increases** excit. receptors, or decrerases inhibitory receptors.**

Question 29

Inhibitory Post Synaptic Potential (IPSP)

Answer 29

Opening of chloride Cl- ion channels,increase in K ions out of cell, and change recetors that motivate its intent of inhibition

Question 30

Summation of graded potentials-Spatial

Answer 30

Single terminal isnt enough power to release enough neurots, they need to add to one another to trigger an actional potential.

(When the EPSP becomes great enough, the threshold for firing will be reached)

Question 31

A change in potential in any part of the intrasomal fluid causes what due to a very high electrical conductivity?

In Spatial Summation

Answer 31

Almost exactly equal change in potential at all other points inside the soma.

Question 32

Summation of graded potentials-Temporal

Answer 32

Each time a presynaptic terminal fires= released neuroT opens membrane channels for ~1millisecond, but changed postsynaptic potential lasts up to 15 miliseconds.

A second opening= increases the post synpatic potential to a greater level and the more rapid the rate of stim.

Successive discharges from a single presynpatic terminal, occur rapidly enough, can add to one another or “Summate”.

Question 33

Presynaptic Facilitation/Excitation

Answer 33

Presynaptic release of the transmitter closes** K+ channels= prologation of action potential–>increases calcium Ca2+ influx **into the postsynaptic axon termin and enhances excitatory transmitter release by neuron B at its synpase with the postsynpatic neuron C.

Question 34

Presynaptic Inhibition

Answer 34

Occurs at the terminal before the singal ever reaches the synapse/before their own endings terminate on postsynaptic neuron. Inhibitory transmitter: GABA usually
Generally leads to opening of anion channel.

Question 35

Glycine Amino Acid Neurotransmitter

Answer 35

Spinal Cord, Inhibitory

Question 36

Glutamate Amino Acid Neurotransmitters

Answer 36

Secreted by the presynaptc terminals in many of the sensory pathways entering the CNS + cerebral cortex.
Excitation

Question 37

GABA (Gamma aminobutyric Acid)

Answer 37

Spinal cord, Cerebellum, basal ganglia, cortex.
Inhibition

Question 38

What does acetylcholine split up into and by what enzyme?

Answer 38

Acetate and Choline by cholinesterase (present in the proteoglycan reticulum)