Chapter 3: Signalling And Neuronal Communication

Question 1

What cells have membrane potential?

Answer 1

All cells (even plant cells!)

Question 2

What is membrane potential?

Answer 2

The separation of charges across the plasma membrane due to differences in concentration and permeability of key ions

Question 3

What ions move across the membrane and what is their permeability levels?

Answer 3

• Na+ ( 1 permeability level)
• K+ ( 50-70 permeability level)

Question 4

What are the other ions present in the ICF and ECF?

Answer 4

• Cl- in the ECF (only moves when one nerve is signaling)
• HCO3- in ECF (doesn’t move)
• Anions (A-) (stuck in the ICF

Question 5

What is the job of the NaK pump?

Answer 5

Bring ions back to their original position/concentration
- 3Na for every 2 K
- primary active transport

Question 6

What are the 4 types of Gated Channels (GC)?

Answer 6

1) Voltage GC - detect small mV change
2) Chemically GC - chemicals can come in e.g. neurotransmitters
3) Mechanically GC - touch
4) Thermally GC - hot or cold

Question 7

What are the two types of potential change?

Answer 7

1) graded potential
2) action potential

Question 8

What are the 6 characteristics of graded potential?

Answer 8

1) short distance
2) variable strength (bigger rock = bigger splash)
3) local changes due to Na+ ions
4) local current flow = depolarization
5) decremental because ions leak and it causes cytoplasmic resistance
6) body functions

Question 9

What are the four body functions of graded potential?

Answer 9

1) post synaptic potential (psp)
2) receptor potential
3) endplate potential
4) pacemaker

Question 10

What is action potential dependent on?

Answer 10

1) positive feedback to peak
2) double gated voltage channels
3) delayed opening of the K+ channels
4) 2 types of movement
5) refractory (two types)

Question 11

What are the characteristics of action potentials?

Answer 11

1) long distance
2) dependent

Question 12

What are the two types of movement in action potentials?

Answer 12

1) Contiguous (touch) conduction
- used more energy
- eg internal organ digestive
2) Saltatory (jump) conduction
- faster (50x)
- myelinated
- eg skeletal muscles

Question 13

Where is myelin formed?

Answer 13

• CNS myelin is formed by the oligodendrocytes
• PNS myelin is formed by the Schwann cells

Question 14

What are the two types of refractory in action potentials?

Answer 14

1) absolute refractory
- Na+ channels closed
- K+ channels still open (refluxing)
2) relative refractory
- big stimulus
- Na+ reset
- few K+ are open

Question 15

What are the three types of Post Synaptic Potential (PSP)?

Answer 15

1) excitatory psp
- eg nak pump
2) inhibitory psp
- hyper polarized K+ is effluxing (leaking) or Cl- influx (ECF - ICF)
3) Summation (Grand psp)

Question 16

What is no summation?

Answer 16

Excitatory doesn’t reach threshold so no action potential occurs

Question 17

What is temporal summation?

Answer 17

Two of the same excitatory signals cause threshold to be met so action potential occurs

Question 18

What is Spacial Summation?

Answer 18

Two different excitatory signals cause threshold to be met so action potential occurs

Question 19

What happens when there is an inhibitory signal and an excitatory signal

Answer 19

Inhibitory and excitatory cancel each other out