Graded Potentials

Question 1

For an open channel what factors determine in which direction ions move through the channel?

Answer 1

• concentration gradient
• electrical gradient
• both - the electrochemical gradient

Question 2

What is the value for the typical resting membrane potential

Answer 2

-70mv

Question 3

For which cation is there the greatest amount of leakage across the resting plasma membrane

Answer 3

• Na+

- K+

Question 4

What are the Excitable tissues

Answer 4

-Nerve and muscle are excitable tissues that can undergo rapid changes in their RMP (resting membrane potential).

Question 5

There are two kinds of potential change in excitable tissues what are they

Answer 5

• graded potentials (GPs) which serve as short distance signals
• action potentials (APs) which serve as long distance signals

Question 6

What is the fastest way to move ions across cell membrane

Answer 6

Through ion channels

Question 7

What does the opening of ion channels allow

Answer 7

Ions to flow across membrane

Question 8

Ion channels are what

Answer 8

• Pores in cell membrane
• Selective for particular ion
• Passive as in no energy is required so ions flow down their electrochemical gradient
• gated

Question 9

What are the types of changes in membrane potential

Answer 9

Depolarisation
Repolarisation
Hyperpolarisation
Resting potential

Question 10

Describe the changes in membrane potential

Answer 10

…

Question 11

What is the function of the neuron

Answer 11

Function is to transport impulses around the body allowing communication

Question 12

What are the same structures in the neuron which are in other cells of the body

Answer 12

Plasma membrane
Nucleus
Endoplasmix reticulum and golgi apparatus
Mitochondria etc

Question 13

What are the the ways the neuron is specialised for its function

Answer 13

• axon
• dendrites
• myelin sheath

Question 14

Draw the structures of the different neurons and label them

Answer 14

Draw sensory neuron interneuron and motor neuron

Question 15

How does a neuron send signal to another neuron

Answer 15

1) stimuli are received by the dendrites and cell body
2) synaptic stimuli are summed at the axon hillock where an action potential is triggered if the sum of the arriving signals is high enough
3) action potentials are conducted to the axon terminal where they cause the release of neurotransmitters.
These bind to receptors on the postsynaptic cell membrane creating a new signal in the postsynaptic neuron

Question 16

What are graded potentials

Answer 16

Short lived localised changes in RMP
It is triggered by changes in environment which cause opening of gate ion channels
They may be either hyper or depolarisation

Question 17

Depolarisation in graded potentials

Answer 17

Initial stimulus depolarises small area of membrane

Question 18

Spread of depolarisation in graded potentials

Answer 18

Local currents created depolarise adjacent membrane areas ; wave of depolarisation spreads

Question 19

Describe the magnitude in graded potentials

Answer 19

Magnitude declines with distance
Magnitude of GPs varies directly with the magnitude of the stimulus and the magnitude can be up to 15mV.
Examples include:
-Excitatory postsynaptic potentials EPSPs
-Inhibitory postsynaptic potentials IPSPs
-Receptor potentials
-Pacemaker potentials