Nerves 3

Question 1

When is an AP sent?

Answer 1

When the RMP depolarises to threshold at around -55mV

Question 2

What causes the depolarisation of RMP?

Answer 2

External stimuli acting on specific sets of ion channels to create graded potential where the size of potential is related to the size of the stimulus

Question 3

What is a synapse?

Answer 3

A junction between 2 neurones where AP releases transmitter molecules that activate receptor on the second cell which open ion channels creating another graded potential

Question 4

What happens at the NMJ?

Answer 4

Motor neurone depolarises the muscle to threshold by evoking a graded potential known as the endplate potential

Question 5

What are examples of graded potential?

Answer 5

• Generator potentials at sensory receptors
• Postsynaptic potentials at synapses
• Endplate potentials at NMJ (skeletal muscle)
• Pacemaker potential in pace maker tissue

Question 6

What are properties of graded potentials?

Answer 6

• Electronic potentials
• Decremental potentials
• Non-propagated potentials
• Local potentials

Question 7

Why are graded potentials decremental and non-propagated?

Answer 7

As you go further away from the site of stimulus, more current leaks out along the membrane and so a result the membrane potential gets smaller and smaller

Question 8

Where can graded potential signal stimulus intensity?

Answer 8

In their amplitude

Question 9

What is meant by graded potentials being graded?

Answer 9

A stronger stimulus would open more channels, creating a bigger current flow and therefore a bigger potential

Question 10

Why can graded potentials be depolarising or hyper-polarising?

Answer 10

• Firing an AP depends on reaching a firing threshold

- Graded potentials can therefore excite or inhibit a cell

Question 11

What do EPSPs or IPSPs stand for?

Answer 11

• Excitatory postsynaptic potentials

- Inhibitory postsynaptic potentials

Question 12

What do EPSPs or IPSPs depends on?

Answer 12

which ion channels are opened

Question 13

Opening which ion channels would causes hyper-polarisation?

Answer 13

K+ and Cl-

Question 14

What would opening potassium and chlorine channels do?

Answer 14

• Causes hyper-polarisation
• Takes them aways from threshold
• IPSP

Question 15

What would opening Na and Cl channels do?

Answer 15

• Causes depolarisation
• Takes them towards threshold
• EPSP

Question 16

What are ligand-gated ion channels?

Answer 16

Postsynaptic potentials are produced by a neurotransmitter opening or closing ion channels

Question 17

What are voltage-gated ion channels?

Answer 17

Action potentials are produced by depolarisation of the membrane potential opening ion channels

Question 18

Why are graded potentials important in synaptic integration?

Answer 18

Graded potentialis can summate

Question 19

What is temporal summation?

Answer 19

One stimulus that is stimulated again quickly and the second EPSP adds on

Question 20

What is spatial summation?

Answer 20

When 2 separate stimuli add together

Question 21

What is integration?

Answer 21

Looking at all of the inputs and deciding whether or not o send one of those long distance signals (AP)

Question 22

What is synaptic integration?

Answer 22

The process of summing all those imputes in space and time to determine whether or not the initial segment reaches threshold

Question 23

What do IPSPs tend to do?

Answer 23

Stops the cell reaching threshold