Polvi lec #7

Question 1

What are neurons?

Answer 1

are nerve cells specialized for communication with other cells in the form of electrical impulses which are formed by chnage sin ion gradients

Question 2

In vertebrates, where are most neurons located?

Answer 2

in the central nervous system

Question 3

What is the neuron structure?

Answer 3

Dendrites- these receive info
Cell body
Nucleus
Axon- conducts outgoing info, covered by myelin sheath
Node of ranvier
Terminal knob (are where impulses are transmitted to the target cell)

Question 4

What is a myelin sheath? What’s it do?

Answer 4

Is a lipid rich membrane, speeds up transport of signals

Question 5

What is membrane potential?

Answer 5

Is a difference in charge across a membrane

Question 6

What is resting potential?

Answer 6

is the membrane potential when a nerve cell is resting

Question 7

What is the inside of nerve cells charge compared to the outside?

Answer 7

negative

Question 8

What is the value of the resting potential for a neuron?

Answer 8

-70 mV

Question 9

What two things contribute to the diff in charge across the neuron membrane, leading to a negative resting potential?

Answer 9

1. Na+/K+ pump- pumps 3 Na+ ions per 2 K+ ions it pumps in, lead sinside of cell to be more neg
2. K+ ions can flow out through potassium leak channels (following their conc gradient as less K+ outside cell)

Question 10

When is equilibrium of a nerve cell obtained?

Answer 10

when a balance is reached between the conc gradient favoring K+ leaving the cell and the electrical gradient favoring K+ staying inside the cell

Question 11

What is an action potential?

Answer 11

Is a change in membrane potential after a stimulus and is the basis for neural communication, it includes depolarization and repolarization phases

Question 12

How long does an action potential take in a squid axon?

Answer 12

5 ms

Question 13

How does the cell behave at resting potential?

Answer 13

the sodium potassium gates are both closed, and potassium leaks out cell through it’s own channels

Question 14

How does the cell behave during depolarization?

Answer 14

a stimulus causes sodium channels to open, which results in sodium entering the cell making it more positive, our voltage is now at 40 mV

Question 15

How big does the stimulus have to be to depolarize the cell?

Answer 15

small stimulus results in no depolarization, the voltage gated sodium channels only open when the depolarization is above a threshhold value of -50 mV

Question 16

How long do sodium channels stay open after a stimulus?

Answer 16

1 ms

Question 17

How does the cell behave during repolarization?

Answer 17

the depolarization of the cell leads to the opening of the potassium channels, sodium channels close, potassium gets pumped out and membrane potential to go to -80 mV which then causes the potassium channels to close back up

Question 18

What changes during the action potential, the membrane potential or the sodium/potassium conc gradients?

Answer 18

The membrane potential, do from -70 to 40 to -80, the concentration gradients of the ions are not affected

Question 19

How does an action potential go down a neuron?

Answer 19

the action potential triggers other action potentials down the portions of the neuron membrane

Question 20

What is continuous conduction?

Answer 20

Occurs in unmyelinated axons, the action potential flows and makes the regions just ahead to become depolarized (positive), this allows the action potential to be propagated without any loss of intensity, involves a refractory period

Question 21

What’s a refractory period?

Answer 21

When portions of the membrane that just experienced the action potential in continuous conduction can’t open their Na+ channels for a few ms, this make sit so that the action potential can only move forward

Question 22

What is saltatory conduction? How does it work?

Answer 22

Occurs in myelinated axons, here potassium and sodium channels are found near unmyelinated regions called nodes of ranvier, an action potential at one node triggers an action potential at the next node, myelinated axons prevent the passage of ions across the membrane (can only flow from node to node)