Graded Potentials

Question 1

What is the function of graded potentials?

Answer 1

depolarise cells to the threshold of -55mV and allow an action potential to be fired

Question 2

Where are graded potentials?

Answer 2

At sensory receptors

When sensory receptors respond to stimuli of interest (pain, pressure) stimuli causes ion channels to open and depolarizes cell threshold to fire an action potential

At Synapses

neurotransmitter released from presynaptic terminal, diffuse across synaptic cleft and then bind to receptors on surface of postsynaptic cell membrane
This opens other channels which can then depolarise the cell to threshold and fire action potential

At end plate potentials

At neuromuscular junction

for muscle cell to contract, needs to have action potential evoked in cell membrane

Question 3

Where are pacemaker potentials?

Answer 3

In pacemaker tissues

Question 4

What happens when a small stimulus occurs?

Answer 4

small response- small no. mechanosensitive ion channels to open and a small depolarisation

Question 5

What happens when stronger stimulus occurs?

Answer 5

large response- large no. mechanosensitive ion channels open and large depolarisation

Question 6

Why are graded potentials decremental?

Answer 6

Become smaller as they travel along the membrane, positive ions leaking out of cell membrane
Graded potentials are therefore only useful over very short distances
This is why graded potentials are also called local potentials

Question 7

Describe an excitatory post synaptic potential? (post synaptic cell membrane)

Answer 7

depolarising cell and bringing close to cell threshold

Question 8

Describe an inhibitory postsynaptic potential?

Answer 8

neurotransmitter binding to different receptors and opening different channels which are then de polarising cell
brings cell away from threshold (inhibiting cell)

Question 9

What method would mean a cell is likely to be depolarised to threshold?

Answer 9

If two individual graded potentials happen at the same time, they can add to together to make bigger graded potential

Question 10

What channels do we need to open to depolarise cell?

Answer 10

Sodium- pulled into cell down its massive concentration gradient
electrical gradient also pulling sodium into cell as the resting membrane potential is negative and sodium is positive

Question 11

What channels to hyperpolarise cell?

Answer 11

chloride channels- if negatively charged chloride flows into cells- cells more negative