course 2

Question 1

What are the types of neuronal electrical signals?

Answer 1

-receptor potential: changes in the membrane of sensory receptor cells in response to stimuli( light, sound, touch)
-Synaptic potential
-action potential

Question 2

what the hyperpolarizing pulses produce?

Answer 2

passive potential

Question 3

What are the passive properties of a neuron?

Answer 3

-Related to the resting state
-Membrane resistence: resistance to the flow of ions(ion channels and membrane properties), which determines how easily the membrane can be depolarized
-Membrane conductance: measures the movement of charge across the membrane.
-the capacitance: allow the neurons to store electrical charge, it affects how quickly the membrane potential can change in response to inputs
-leakage of charges: the passive potential decreases in amplitude over both time and distance as they spread along the dendrites and cell body of a neuron

Question 4

What are the active properties of a neuron?

Answer 4

• Action potential
• Excitability
  -Treshold
  -All or none response
  -Refractory period

Question 5

who responsible for the movement of ions across the neuronal membrane?

Answer 5

-Active transporters: Actively move selected ions against their concentration gradients, creats ions concentration gradients
-Ion channels: Allow ions to diffuse down the concentration gradients,they are selectively permeable to certain ions.

Question 6

What is an electrochemical?

Answer 6

determines the direction that ions will flow through an open ion channel and is a combination of two types of gradients: The chemical gradient, or difference in solute concentration across a membrane. The electrical gradient, or difference in charge across a membrane.

Question 7

How the potential membrane is generated?

Answer 7

due to the different ions content inside and outside the cell

Question 8

What is the Nernst equation?

Answer 8

defines the relation between the concentrations of an ion on either side of a membrane that it perfectly selective for that ion and the potential difference (voltage) that will be measured across that membrane under equilibrium conditions.

Question 9

How Electrical Potential influences Ionic Movements?

Answer 9

The ions always move to reach their potantial equilibrium:
- when the battery is off the K+ flow from inside to outside( according to their concentration gradient)
- when the initial membrane potential at the potential equilibrium of k+ there is no net flux of k+
- When the membrane potential is more negative than the K+ potential equilibrium, the K+ flow from outside to inside(against their concentration gradient)

Question 10

What is the goldman equation?

Answer 10

calculates the membrane potential based on the electrochemical gradient of all permeant ions (usually Na+, K+, Cl- and sometimes Ca2+ ) and the permeability of the membrane to each ion

Question 11

What is the relationship between the potential membrane and the K+ concentration?

Answer 11

When we plotted the relation we found that the splot is 58 mV, which means that for every tnfold increase in the external K+ concentration, the resting membrane potential will shift by 58 mV in the positive direction or in the negative direction if the concentration outside decreases

Question 12

hich ion has greater net driving forces K+ or Na+?

Answer 12

Na+ has much larger net driving forces bacause:
- K+ has chemical driving force out of cell, but electrical driving force into cell.
-Na+ ions has both chemical driving force and electrical driving force into cell.

Question 13

Why a relativel small net driving forces for K+ drives a current equal and opposite to the Na+ current driving by the much larger net driving forces?

Answer 13

the aggregate conductance of the K+ channels is much greater than that of the Na+ channels because they are more numerous

Question 14

what is a steady state?

Answer 14

neither Na+ nor K+ is in equilibrium but the net flux of charges is null

Question 15

what is the role of Na+?

Answer 15

Although amplitude of the action potential is quite sensetive to the external concentration of Na+, the resting membrane is little affected by changing the concentration of this ion

Question 16

What are the phases of action potential?

Answer 16

-Rising phase
-Overshoot phase
-Falling phase
-Undershoot phase

Question 17

What is the voltage clamp Method?

Answer 17

It is called a voltage clamp because it controls or clamps, membrane potential at any level desired, it permits the simultaneous measurement of the current needed to keep the cell at a given voltage. This current is exactly equal to the amount of current flowing across the neuronal memberane. Therefore, thid device can indicate how membrane potential influences io,s current flow across the membrane

Question 18

what a hyperpolArazition OF THE MEMBRANE POTENTIAL produces?

Answer 18

very brief capacitive current

Question 19

what a depolarization of the membrane produces?

Answer 19

A brief capacitive current followed by a longer lasting but transient phase of inward current and a delayed but sustained outward current

Question 20

What is the potential equilibrium of K+?

Answer 20

-90 mV

Question 21

What is the equilibrium potential of Na+?

Answer 21

+55 mV

Question 22

What is the relationship between the potential membrane and current amplitude?

Answer 22

The late outward current increases w²ith increasing the depolarization, whereas the early inward current firstly increases in magnitude but decreases and reverses to outward current at about of +55 mV

Question 23

What the inward current?

Answer 23

positive charge is moving inward < SODIUM

Question 24

What is the outward current?

Answer 24

positive charge is moving ouward < POTASSIUM

Question 25

How the action potential propagates?

Answer 25

Depolarization opens the Na+ channels locally and produces an action potential, the resulting inward current flows passively alog the axon, depolarizing the adjacent region.

Question 26

What is the refractory period?

Answer 26

Voltage-gated Na+ channels have two gates that respond in opposite ways to depolarizition. On replarizition the the inactivation gate open and the activation gate is closes as the channel returns to the resting state.

Question 27

why the myelin sheet faster the propagation of action potential?

Answer 27

The presence of myelin prevents the local curent from leaking across the internal membrane

Question 28

What is the multiple sclerosis?

Answer 28

Multiple sclerosis (MS) is a potentially disabling disease of the brain and spinal cord (central nervous system). In MS , the immune system attacks the protective sheath (myelin) that covers nerve fibers and causes communication problems between your brain and the rest of your body.