Neurophysiology

Question 1

Loss of sensation caused by depression of excitation or inhibition of conduction not including loss of consciousness is called what?

Answer 1

Local Anesthesia

Question 2

Abnormal and unpleasant sensation to normal stimuli is called what?

Answer 2

Dysesthesia

Question 3

Excessive pain response to non-noxious stimuli is called what?

Answer 3

Hyperesthesia

Question 4

Decreased sensitivity to stimuli (numbness) is called what?

Answer 4

Hypoesthesia

Question 5

Altered sensation (pins and needles) is called what?

Answer 5

Paraesthesia

Question 6

What are the two types of neurons?

Answer 6

1-Sensory (afferent)- to CNS

2-Motor (Efferent)-from CNS

Question 7

What are the 3 major parts of a sensory neuron?

Answer 7

1-Peripheral process
2-Axon
3-Soma (not involved in impulse transmission but supports metabolically)

Question 8

What is the resting membrane potential voltage?

Answer 8

-70 mV

Question 9

Nerve fibers that insulated the axon by wrapping around the fiber, improving impulse conduction, are called what?

Answer 9

Schwann cells (myelination)

Question 10

The “gaps” caused by constrictions at regular intervals along the myelinated nerve fiber are called?

Answer 10

Nodes of Ranvier

Question 11

Which nerve class and subclass is and afferent sensory nerve for pain, temp and touch?

Answer 11

Class:A
Subclass: Delta

*myelinated, 1-4 um, conduct velocity 5-25

Question 12

Which nerve class and subclass is afferent sensory for various autonomic funcitions as well as pain temp and touch?

Answer 12

Class: C
Subclass: dGammaC

*Unmyelinated, 0.4-1.2 um, conduct velocity 0.1-2.0

Question 13

What are the 4 phases of nerve conduction?

Answer 13

1-Initial phase of slow depolarization
2-Rapid phase (threshold is reached, roughly -50/-60 mV)
3-Reversal of electrical potential (reaches +40 mV)
4-Repolarization (-60/-90 mV)

Question 14

What are the two different gradients that exist?

Answer 14

1-Concentration gradient (physical separation)

2-Electrostatic gradient (electrostatic charge separation)

Question 15

At rest the membrane is _______ permeable to Na+, and ________ permeable to K+ and Cl-

Answer 15

Slightly, Freely

*Ca+ binding facilitates increased Na+ permeability into the cell

Question 16

K+ ions entering the cell during repolarization is a __________ process and Na+ ions being pumped out of the cell is a ______ process

Answer 16

Passive, active (requires ATP)

Question 17

The period during which a cell is unable to respond to another stimulus is called?

Answer 17

Absolute refractory period

Question 18

The period during which a stronger than normal stimulus could trigger another impulse is called?

Answer 18

Relative refractory period

Question 19

The impulse propagation of unmyelinated nerves is like what?

Answer 19

A fuse, each segment setting the following segment up for activation

Question 20

Impulse propagation that is discontinuous, leaping from one node to the next such as in mylenated nerves is called what?

Answer 20

Saltatory conduction

*Each saltatory conduction provides more than enough current flow to activate the next node, if one node is blocked, the sequence can jump

Question 21

How does local anesthetic work?

Answer 21

• Decreases permeability of ion channels to Na+
• Competitive antagonism for Ca++ sites
• Decrease rate of rise of action potential and its conduction velocity

Question 22

What are the 7 events of local anesthetic use? (like trying to light a wet fuse)

Answer 22

1-Ca ions displaced from sodium channel receptors
2-binding of LA to receptor site
3-Na+ channel blockade
4-Decrease Na+ conductance
5-Depress rate of depolarization
6-Failure to reach threshold
7-Lack of propagated action potential known as conduction blockade