Nervous System Unit Lesson 2: Nerve Impulses

Question 1

what is voltage

Answer 1

potential difference or “electric pressure”

Question 2

how do nerves transmit signals

Answer 2

they do this through nerves impulses

Question 3

how does an oscilloscope work

Answer 3

it measures the potential difference between two points along a neuron and graphs them as they occur

Question 4

what is the resting potential

Answer 4

the difference in charge between the inside of the cell and the outside of the cell when a neuron is not performing an impulse

Question 5

what is the resting potential measured at and what does that mean

Answer 5

-70mV, and it means that the interior of the cell is more negative than the exterior

Question 6

describe the concentration of sodium ions (Na+) outside of the neuron

Answer 6

it is high

Question 7

describe the concentration of potassium ions(K+) outside of the neuron

Answer 7

it is low

Question 8

describe the concentration of sodium ions(Na+) inside the neuron

Answer 8

it is low

Question 9

describe the concentration of potassium ions(K+) inside the neuron

Answer 9

it is high

Question 10

what happens to the polarity when a nerve impulse fires and why

Answer 10

there will be a rapid changing of polarity because of the separation of charges

Question 11

how is the separation of charge inside and outside the neural membrane accomplished

Answer 11

it is accomplished through channel proteins and sodium-potassium pumps which are closed until there is an impulse

Question 12

what are the sodium-potassium pumps responsible for

Answer 12

they are responsible for pumping sodium and potassium across the membrane, against the concentration gradient

Question 13

when a nerve impulse fires, why is there a rapid changing of polarity

Answer 13

it is because of the movement of ions across the membrane

Question 14

what is action potential

Answer 14

the movement of ions across the membrane/ the change in polarity

Question 15

what are the 4 steps to action potential

Answer 15

1. sodium gates open 2. potassium gates open 3. conduction of action potential 3. synaptic transmission

Question 16

explain the beginning of an action potential(details)

Answer 16

when the sodium gates open, the numerous sodium ions move across the membrane due to the concentration gradient, and this movement causes the potential to rapidly change from -70mV to 35mV

Question 17

what is depolarization

Answer 17

when the total charge of anions in the membrane are now outnumbered by cations due to the potassium ions already in the neuron and the added sodium ions after the first step of action potential

Question 18

what is inside a neuron

Answer 18

a very large concentration of anions and a large concentration of potassium ions

Question 19

explain the second step of an action potential(potassium gates)

Answer 19

the potassium gates open that allows the movement of potassium ions across the membrane to outside the neuron. the low concentration of potassium ions outside the neuron causes movement across the membrane through potassium channels.

Question 20

what is repolarization

Answer 20

it is when the total negative charge inside the membrane is now greater than the positive charge, re-establishing the concentration gradient of charge where outside the neuron is more positive than inside. this happens during the second step of action potential

Question 21

what is the only way action potential be achieved (request potential)

Answer 21

if the request potential is present to begin the depolarization process. the potential must rise from the resting -70mV to roughly -55mV to -50mV

Question 22

what is a refractory period

Answer 22

it is a short period of time where another action potential can occur at the same area

Question 23

describe the refractory period

Answer 23

it is when the sodium-potassium pumps work to re-establish ion concentrations inside and outside the cell membrane

Question 24

what is saltatory conduction

Answer 24

it is when the action potential is said to “jump” between regions on the axon(because of the myelin sheath that covers regions of the axon)

Question 25

what is an axon terminal and where is it located

Answer 25

it is a small bulb-like terminus which is located at the end of each axon. it is extremely close to the neighbouring dendrite.

Question 26

what is a synapse

Answer 26

the region of the axon terminal and the neighbouring dendrite

Question 27

what is a synaptic cleft

Answer 27

the gap between the axon terminal and the neighbouring dendrite

Question 28

what is the presynaptic neuron

Answer 28

the neuron before the synaptic cleft

Question 29

how is the signal that an action potential represents carried across the synapse

Answer 29

using neurotransmitters

Question 30

explain the process of transporting the signal across the synapse

Answer 30

when the action potential reaches the synapse, gated calcium channels open and calcium ions(Ca2+) enter the axon terminal. these ions cause contractile proteins to pull vesicles containing neurotransmitters to the synapse, where they fuse with the membrane and leave via exocytosis