How do neurons communicate info

Question 1

Electrical signals in the brain - Historical perspective-Galvanni

Answer 1

-Noticed that frogs legs suspended on a wire moved when lightning Struck
- twitching of muscles was due to electrical signal

Question 2

The Resting membrane potential - Neuron

Answer 2

• Has 3 parts: cell body, dendrites (receive info), axon (sends info )
  -Neurons convey electrical signals
• key to process is movement of ions across neuronal memb
  -lon pumps + Ion channels control movement of ions

Question 3

Resting Membrane potential -forces controlling movement of ions

Answer 3

-concentration/diffusion forces =high to low conc
-Electrical forces = neg to pos or pos to neg
-At rest only leak k + ion channels are open
- Higher co- Higher conc of k + in neuron = k + pulled out
- Inside is neg charged = k + pulled in
-Resting pot = -65m V
- The 2 forces are in opposition

Question 4

Resting potential - sodium potassium pump

Answer 4

-Na/ k pump contributes to imbalance of charges by pumping out 3 Na + ions + taking 2 k + ions in
- causes a net loss of 1 and neuron charge is neg
- ATP gives phosphate to the pump (phosphorylation) , causes potassium release
-pump is dephosphorylated

Question 5

The Action potential - Threshold

Answer 5

• If neg current is injected an inhibitory postsynaptic potential (IPSP) occurs = neuron less likely to fire an AP = hyperpolarised memb
  -If pos current injected an excitatory postsynaptic potential ( Epsp) occurs = neuron more likely to fire an Ap=depolarised memb
• ESps must exceed threshold of -50 mV
• If amplitude/duration of ESPs is increased = number of AP increases = spiking rate

Question 6

AP -voltage gated Na + k + channels

Answer 6

• generate AP
• only open when threshold valve is reached + membrane depolarised .
  -Na open first
• Lower conc of Na + inside = pulled in ( conc force + electrical )

Question 7

The Action potential

Answer 7

-Membrane depolarised over threshold = voltage gated Na + ion channels open
-influx of Na + into cell due to concentration + electrical forces
-cell becomes more pos charged (rising phase)
- Na + channels close
-voltage gated k + ion channels open
-Inside cell more pos + K + flows out
-Cell more neg charged (falling phase)
- more K+ leaves neuron = hyperpolarised (more neg)
-overshoot phase due to k + channels staying open longer than they should

Question 8

the Action potential is propagated along axon

Answer 8

-voltage gated channels present at axon hillock-decides whether to fire an Ap( all or nothing )
- When Ap is generated It moves down axon
-voltage-gated channels present at nodes of ranvier where Ap is regenerated
- Axons are surrounded by myelin sheath which helps the conduction of AP

Question 9

Chemical signals in the brain - Loewi Historical perspective

Answer 9

-correctly deduced that nerve transmission occurs by release of chemicals
-chemicals known as NT
-Experiments showed chemicals released by neurons might be important for communication across the whole brain

Question 10

synapse

Answer 10

• Arrival of AP at presynaptic axon terminal sets Off a cascade = releases NT into synapse
  1) Ca enters axon terminal of pre-synaptic neuron
  2) causes NT containing vesicles to release contents into synapse
  3) NT blinds to receptors on post-synaptic neuron
  4) NT open allowing specific ions to move into post-synaptic neuron = potential changes

Question 11

N T receptors in postsynaptic cell

Answer 11

• they are membrane proteins
• Have region for binding NT + ion channel
• NT bind = opens ion channel
• ions flow through =electrical potential of cell changes

Question 12

Drugs + effect on brain

Answer 12

-Agonist drugs = enhance brain activity _ mimic NT + bind to receptor
-Antagoinst = inhibit activity - block NT receptor

Question 13

Removal of NT

Answer 13

• Removed from synapse by : deactivation or uptake, sometimes broken down by enzymes
• some drugs inhibit NT uptake
  -Glutamate terminated by glial cells reuptake which is then recycled revised
  -ProZac prevents reuptake ( treats depression)
  -known as selective serotonin reuptake inhibitors (ssris)

Question 14

summation of postsynaptic potentials

Answer 14

• Nervous system works by correct balance of excitatory + inhibitory signals
  -Excitatory + Inhibitory postsynaptic potentials (ESPS + ISPs) are integrated by neurons)
• summation =multiple impulses come together to cause excitation
• Exi + Inhib = No AP
• E + E = AP
• when multiple excitations combined = AP
  -Temporal summation = 1 neuron fires multiple times close together = AP more likely