Action Potentials & Communication

Question 1

Graded potentials?

Answer 1

Short distance communication

Question 2

Action potentials?

Answer 2

Long distance communciation

Question 3

How do neurons communicate?

Answer 3

Most commonly Action potentials

Question 4

Why do action potentials occur?

Answer 4

Opening & closing of ion channels in response to stimuli

Question 5

What is the resting membrane potential?

Answer 5

The RMP is the voltage difference across the plasma membrane of excitable cells that enable electrical flow of ions

Question 6

How does the membrane potential change?

Answer 6

The electrical flow produced by ions change membrane potential

Question 7

What are leak channels?

Answer 7

Potassium and sodium channels that randomly open and close & located in all cells

Question 8

What are ligand-gated channels?

Answer 8

Channels that open and close in response to ligand bindings such as hormones, neurotransmitters & located in dendrites

Question 9

What are voltage-gated channels?

Answer 9

Channels that open and close due to voltage differences & located in axons

Question 10

Variance of RMP?

Answer 10

-40 to -90 mV

Question 11

Typical RMP value?

Answer 11

-70 mV inside more negative than outside

Question 12

Factors affecting RMP?

Answer 12

Unequal distribution of ions across ECF and INCF, stuck anions, Sodium-potassium pump which all decrease RMP

Question 13

Characteristics of graded potentials?

Answer 13

Mainly occurs in dendrites, and cell bodies, amplitude depends on strength of stimulus, travel short distance & die out quickly, and summate potentials

Question 14

What is an action potential?

Answer 14

Sequence of events that decrease and then reverse the RMP to resting state

Question 15

Depolarization?

Answer 15

Decreases RMP from negative to positive

Question 16

Repolarization?

Answer 16

Resting stage that increases RMP back to normal

Question 17

When does action potentials occur?

Answer 17

When axon is depolarized to -55 mV threshold opening sodium channels and generating action potential

Question 18

What does action potentials do?

Answer 18

Generate the sequential opening of sodium and potassium voltage channels

Question 19

Subthreshold stimulus?

Answer 19

Below threshold

Question 20

Supratheshold stimulus?

Answer 20

Above threshold

Question 21

What happens during suprathreshold stimulus in action potentials?

Answer 21

The frequency of potentials increases

Question 22

What happens during depolarization?

Answer 22

During depolarization the NMP decreases and becomes positive, changing the NMP from -55 to + 30 mV, leading to sodium channel domino effect

Question 23

What is the relative refractory period?

Answer 23

When a supra-threshold stimulus is required to enact another action potential

Question 24

What is the absolute refractory period?

Answer 24

No level of stimulus will generate action potential

Question 25

Characteristics of action potentials?

Answer 25

Travel from the trigger zone, are decremental and propagate and need to be regenerated again and again to reach end of terminal

Question 26

Continuous conduction?

Answer 26

Step-by-step depolarization and repolarization of membrane along unmyelinated axons

Question 27

Salutatory conduction?

Answer 27

Action potentials jump along the nodes of ranvier in myelinated axons, faster and more energy efficient

Question 28

Group A fibers?

Answer 28

largest diameter, speed, myelination and lowest refractory period - skeletal muscle motor neurons

Question 29

Group B fibers?

Answer 29

Less diameter, speed, myelination, longer refractory period - sensory impulses

Question 30

Group C fibers?

Answer 30

Smallest diameter and speed, no myelination and high refractory period - autonomic motor fibers

Question 31

Electrical Synapases?

Answer 31

Conduct directly through plasma membrane through gap injunctions through connexons - faster and synchronized potentials

Question 32

Chemical synapses?

Answer 32

Neurotransmitters carry stimulus from pre-synaptic neurons across synaptic cleft to post-synaptic receptors

Question 33

Neurotransmitters?

Answer 33

Can inhibit or excite effectors or neurons

Question 34

Removal of neurotransmitters?

Answer 34

Diffusion - away from receptors, enzyme degradation and reuptake - returned to pre-synaptic neuron by vesicles