W2

Question 1

How are signals able to move from one neuron to another

Answer 1

diffusion of chemicals would be too slow - an electrical signal which is an action potential

Question 2

what is the resting membrane potential an example of

Answer 2

electrical excitability

Question 3

what is resting membrane potential

Answer 3

when the neuron is not active (passive state) and energy is expended to maintain an unstable state

Question 4

what is an action potential

Answer 4

as neuron is in unstable state then a trigger and release stored up energy and it is the release of this energy which causes an electrical signal

Question 5

what is the cell membrane of a neuron made of and why is that important?

Answer 5

lipid bilayer (2 layers of fatty molecules) - RMP depends on this as ions (charged molecules) dont pass through easily = barrier therefore creases disparity in constitution of the liquid inside and outside N = unstable RMP

Question 6

so this cell membrane is a barrier but what is inside it and what function does it have?

Answer 6

proteins
1 - ion transporter = inside cell surface of neurons is sodium potassium exchange transporter which moves Na ions out N and in exchange moves K in (both cations +ve)
2 - chloride (anion -ve) also involved
= outside +ve and inside -ve as more sodium out then potassium in
diff = -70mV

Question 7

what are the important forces at work in the RMP?

Answer 7

1 - electrostaticv pressure = charge of ions - same charge = ions repel each other and diff charge they attract each other
2 - diffusion = ions move from their areas of high concentration to areas of low concentration - lipid bilayer acts as barrier
3 - transporter = moves specific ions - uses large amounts of energy to maintain RMP

Question 8

What does does it look like at rest?

Answer 8

• low sodium but it enters due to ESP and D
• high potassium that cant move
• low chloride that cant move
• negatively charged

Question 9

AP - stage 1 & 2

Answer 9

At rest membrane is polarised but will start to depolarise at around -55mv - voltage gated channels mean that sodium channels open and membrane becomes more permeable to sodium so sodium ions move in due to D and ESP and the membrane potential is less neg

Question 10

AP - stage 3 & 4

Answer 10

membrane potential turns positive so potassium cations can leave the cell due to D and ESP then at +40mV sodium channel closes so just K leaves so the inside is less +ve and the membrane repolarises

Question 11

AP - stage 5

Answer 11

potassium cations continue to leave cell even beyond the membranes resting potential of -70mV = membrane hyperpolarisation

Question 12

AP - stage 6

Answer 12

evential potassium channel closes and other processes restore balance to the resting membrane potential

Question 13

what does the Myelin Sheath do?

Answer 13

it allows the action to move across a neuron really quickly

Question 14

what does 1 neuron have to do to another to transmit its information?

Answer 14

cause the other neuron to depolarise

Question 15

size of ‘chemical’ synapse

Answer 15

20 nm

Question 16

what is a PSP (post synaptic potential)?

Answer 16

when released NT bind to receptors on the PoSN which then opens ion channels - this then changes the postsynaptic potential as it causes the neuron to depolarse

Question 17

what are the different types of PSPs?

Answer 17

1. EPSPs - hypopolarisation which is depolarisation of the membrane caused by opening of cation channels - excitatory PSP - increases liklihood of AP
2. IPSPs - hyperpolarisation cause by opening on anion channels - inhibitory - less likely to inhibit an AP

Question 18

what happens in an electical synapse?

Answer 18

2 neurons fuse together directly so ions can move directly = electrical potential transfers dirctly - no directionality with this