Lecture 15

Question 1

What are unipolar neurons

Answer 1

primary afferents of some cranial and spinal nerves of vertebrates

Question 2

Where are psuedopolar neurons

Answer 2

sensory neurons in the Dorsal root ganglion (DRG)

Question 3

Where are bipolar neurons

Answer 3

photoreceptors in the retina - rods and cones

Question 4

Where are multipolar neurons

Answer 4

motor neurons
most neurons in CNS and PNS have similar morphology

Question 5

What is a multipolar neuron

Answer 5

nerve cell with one axon and several dendrites extending from its soma

Question 6

What are the structural input zones of a nerve, and its functional property

Answer 6

Dendrites: synaptic connections
Soma: metabolic center

Question 7

What is the conduction zones structural region and functional property

Answer 7

Axon: initiation of action potential
Myelin: increases speed of conduction
Node of Ranvier: voltage gated Na+/K+ channels

Question 8

What is the structural region and functional property

Answer 8

Vesicles: terminal boutons loaded with neurotransmitters
Vesicle-associated proteins: neurotransmitter release
Synaptic cleft: space between two neuron
post synaptic terminal: receptor/ion channel

Question 9

Describe the Electrical activity of Neurons

Answer 9

electrical impulse is generated and conducted along the entire length of its axon

Question 10

How does current flow

Answer 10

Current (I) flows through resistor (R) results in a change in Voltage (V=IR)

Question 11

What factors contribute to membrane potential in neurons

Answer 11

1. unequal ion distribution (Na+; K+;Ca+;Cl-) across neuronal membrane
2. opening and closing of ion gates (channels)
3. Electrogenic nature of the Na+/K+ ATPase

Question 12

Where is the concentration of Na, K, Cl-, Ca and proteins relative to the cell

Answer 12

Na: outside
K+: inside
Cl-: outside
Ca: outside
Protein: inside

Question 13

What are passive properties of neurons

Answer 13

physical and electrical characteristics like resistance, capacitance, and axial resistance
influence electrical signaling without involving active processes like voltage-gated ion channels

Question 14

What does selective permeability do

Answer 14

gives rise to a membrane potential

Question 15

What gives rise to charge separation

Answer 15

when positive and negative charges are physically moved apart within a system, creating areas of imbalance

Question 16

What do ion pumps do for the membrane potential

Answer 16

help maintain the ion concentration across the membrane

Question 17

the N+/K+ is

Answer 17

electrogenic

Question 18

How can the effect of ion flow on membrane potential be quantified

Answer 18

nernst equation

Question 19

What is the membrane potential at room temp and body temp

Answer 19

20* room temp: 58mV
37* body temp: 62mV

Question 20

What is the Goldman equation (GHK)

Answer 20

predicts membrane potential with multiple ions with different permeabilities and concentrations of multiple ions across a neuron’s membrane

Question 21

What factors influence conduction velocity and spread of current

Answer 21

diameter of the conductor
myelination

Question 22

What is the effect of a small neuron

Answer 22

smaller capacitance and therefore charges faster
however: less resistance

Question 23

what is the relationship between resistance and diamter

Answer 23

Resistance is inversely proportional to the diameter of the conductor

Question 24

What does myelination do

Answer 24

increases Rm and reduces Capicitance

Question 25

contrast invertebrate and vertebrate neurons

Answer 25

invertebrate: large diameter neurons that are un-myelinated neurons Vertebrate: smaller diameter neurons that are myelinated

Question 26

What is an action potential

Answer 26

brief voltage change characterized by rising phase that overshooots zero and a falling phase (repolarization) that may be followed by an after-hyperpolarization, or undershoot

Question 27

How do you record action potential

Answer 27

stimulating electrode (I) and recording electrode (V1)

Question 28

What does an ion through the membrane do at any instance

Answer 28

pulls membrane potential to its ion equilibrium potential

Question 29

What do permeability changes do

Answer 29

produce an action potential

Question 30

What are the three phases of ion channels

Answer 30

closed open inactivated

Question 31

Describe the Hodgkin cycle

Answer 31

produces the rising phase of the action potential initial depolarization 1. opening of Voltage-gated NA+ channels increases Pna 2. Increased Na+ flow down its electrochemical gradient 3. further membrane depolarization opening multiple Na+ channels Positive feedback cycle

Question 32

What does myelination allow for

Answer 32

saltatory conduction

Question 33

Why does AP propagates unidirectionally

Answer 33

membrane refractoriness in area behind the action potential

Question 34

What does the Na+/K+ pump do

Answer 34

restores membrane polarity

Question 35

What is the primary function of the myelin sheath

Answer 35

to insulate axons and speed up electrical impulse transmission

Question 36

2. A neuron with one axon and multiple dendrites extending from the cell body is classified as a

Answer 36

Multipolar neuron

Question 37

Which of the following best describes a key characteristic of an excitable membrane

Answer 37

The ability to generate and propagate rapid, transient changes in membrane potential in response to stimuli

Question 38

The resting membrane potential of an excitable cell is primarily determined by the permeability of the membrane to which ion

Answer 38

Potassium (K+)

Question 39

What event initiates an action potential in a neuron's axon?

Answer 39

A graded potential that reaches the threshold potential

Question 40

Which characteristic is not a factor in the Nernst Equation?

Answer 40

Capacitance

Question 41

According to the Goldman equation, the contribution of each ion to the membrane potential depends most on

Answer 41

Its membrane permeability

Question 42

In a cell, the difference in ion concentration between the intracellular and extracellular fluids results from

Answer 42

both active ion transport and passive diffusion of ions

Question 43

During the repolarization phase of an action potential, the membrane potential

Answer 43

Becomes more negative due to the efflux of K+ ions.

Question 44

Graded potentials are distinct from action potentials because

Answer 44

Graded potentials are proportional to the stimulus and can summate, while action potentials are not.

Question 45

Describe Absolute and Relative refractory periods

Answer 45

Absolute: another AP cannot be generated, regardless of impulse strength, because the Na+ channels are inactivated Relative: a stronger-than-normal stimulus can activate the neuron to send another signal because some Na+ channels have been closed/are resting. However K+ channels are still open, raising K+ permeability and hyperpolarized.