Topic 3 - NERVOUS SYSTEM I (Neuronal Physiology - Electrically Excitable Cells | GP to AP)

Question 1

electrically excitable cells

Answer 1

• ONLY muscle and nerve cells
• capable of producing departures from RMP in response to stimuli (=changes in the external or internal environment)

Question 2

electrically excitable cells:

when a neuron is stimulated

name 3 things that happen

Answer 2

1. gated channels open
2. membrane potential changes, producing a graded potential. If the threshold potential is reached
3. triggers an action potential

Question 3

Graded potential

• stimulus causes what? located where? how?

Answer 3

• stimulus causes a small change in membrane potential, usually on dendrite or cell body (no longer at rest) by opening gated channels (changes membrane permeability)

Question 4

what are the 2 possible results of graded potentials?

Answer 4

1. more positive than RMP = depolarization
   
   • ​​e.g. -70mV to -65mV (closer to 0)
2. more negative than RMP = hyperpolarization
   
   • ​​e.g. from -70mV to -75mV

Question 5

name 1/4 characteristics of graded potentials

1

1. 2. graded potentials are short distance signals - die away quickly (short-lived)
2. magnitude and distance traveled by potential varies directly with the strength of the stimulus
3. graded potentials can summate - 1st graded potential present when 2nd stim occurs ⇒ these add (sum) to create the resulting larger graded potential

Answer 5

ions move passively (unlike charges attract (+ & -) = current flow, causing depolarization or hyperpolarization on adjacent membrane

Question 6

name 1/4 characteristics of graded potentials

2

1. ions move passively (unlike charges attract (+ & -) = current flow, causing depolarization or hyperpolarization on adjacent membrane
2. 3. magnitude and distance traveled by potential varies directly with the strength of the stimulus
3. graded potentials can summate - 1st graded potential present when 2nd stim occurs ⇒ these add (sum) to create the resulting larger graded potential

Answer 6

graded potentials are short distance signals - die away quickly (short-lived)

Question 7

name 1/4 characteristics of graded potentials

3

1. ions move passively (unlike charges attract (+ & -) = current flow, causing depolarization or hyperpolarization on adjacent membrane
2. graded potentials are short distance signals - die away quickly (short-lived)
3. 4. graded potentials can summate - 1st graded potential present when 2nd stim occurs ⇒ these add (sum) to create the resulting larger graded potential

Answer 7

magnitude and distance traveled by potential varies directly with the strength of the stimulus

example:

larger stimulus ⇒ larger graded potential that travels further across the membrane

Question 8

name 1/4 characteristics of graded potentials

4

1. ions move passively (unlike charges attract (+ & -) = current flow, causing depolarization or hyperpolarization on adjacent membrane
2. graded potentials are short distance signals - die away quickly (short-lived)
3. magnitude and distance traveled by potential varies directly with the strength of the stimulus
   4.

Answer 8

graded potentials can summate - 1st graded potential present when 2nd stim occurs ⇒ these add (sum) to create the resulting larger graded potential

Question 9

what happens after a graded potential occurs?

Answer 9

repolarization = return to RMP after depolarization or hyperpolarization

Question 10

Graded potential to Action Potential

• Graded potentials are essential in what?
• IF

Answer 10

• essential in initiating a nerve impulse (action potential)
• IF it is depolarized and IF it is large enough or multiple GPs sum to be large enough (if there is a critical stimulus) ⇒ leads to an action potential

Question 11

what are the 3 steps from GP to AP

Answer 11

1. critical stimulus
2. Graded potential reaching threshold
3. action potential

Question 12

GP to AP

the story so far (draw diagram)

Answer 12