Video Module 3: Neural Communication

Question 1

neurons

Answer 1

• do the functional work of communicating through electrochemical signals
• produce sensation, perception, thought, and behaviour
• about 10% of our brain cells

Question 2

glial cells

Answer 2

• massive support system of brain cells
• guide the development of the NS
• repair cell damage and clean up debris of dead cells
• control nutrient flow
• insulate neurons to facilitate the transmission of electrochemical signals
• astrocytes, microglial cells, oligodendrocytes, ependymal cells
• about 90% of our brain cells

Question 3

soma

Answer 3

cell body of a neuron
- keeps the neuron alive
- contains mitochondria
- contains the cell nucleus

Question 4

dendrites

Answer 4

receive information from neighboring neurons
- have receptors for neurotransmitters

Question 5

axon hillock

Answer 5

• connects the axon to the soma
• where action potentials are initiated
• processes incoming signals and decides whether to send an action potential or not based on the stimuli received

Question 6

axon

Answer 6

transmits action potentials (electric signals)

Question 7

myelin sheath

Answer 7

insulation on the axon to speed up the transmission of signals

Question 8

axon terminal

Answer 8

the end of the axon where the message goes out
- terminal buttons are at the end of the axon and release neurotransmitters into the synaptic junction

Question 9

synapses

Answer 9

gaps between neurons (axon terminals and dendrites) where chemical signals (neurotransmitters) travel across

Question 10

Does the strength of an action potential increase with excitatory stimuli?

Answer 10

No; the strength of an action potential stays the same regardless of the amount of excitatory stimuli.
- Action potentials are all or none; they are either transmitted down the axon or not
- The rate of action potentials over time may change, however neither the strength nor the speed of an action potential can increase

Question 11

Stages of neuronal communication

Answer 11

1) input
2) integration
3) output

Question 12

How does an action potential occur?

Answer 12

An action potential is initiated when excitatory stimuli depolarizes the cell above a certain threshold. The inside of the cell is typically more negative than the outside.
A failed initiation when excitatory input is not strong enough to reach the voltage threshold.
1) Depolarization floods the axon with positive Na+ ions. These channels are time-locked, meaning that they close after ~1ms.
2) The action potential fires.
3) Repolarization causes K+ ions to pump out of the cell membrane.
4) A refractory period occurs where the cell’s interior is more negative than its resting state

Question 13

How do action potentials travel down the axon?

Answer 13

Action potentials travel like ripples or dominoes down the axon.
- ions do not travel down the axon
- there is a ripple of energy down the axon due to the change in voltage across the cell membrane
- once there is depolarization in one segment of the axon, sodium channels in the following segment of that axon are unlocked

Question 14

stages of synaptic transmission

Answer 14

1) Neurotransmitters are released from the axon terminal in vesicles into the synaptic junction
2) Neurotransmitters bind with receptors on the next neuron’s dendrite
—Neurotransmitters do not enter the postsynaptic cell
3) Receptors open channels to allow charged ions in or out of the cell
- positive ions = excitatory
- negative ions = inhibitory

Question 15

excitatory neurotransmitters

Answer 15

• make the receiving neuron more likely to fire an AP
• cause channels for positive ions to open
• depolarize: raise resting potential of the neuron (negative to neutral)
• norepinephrine, glutamate, sometimes acetylcholine and dopamine

Question 16

inhibitory neurotransmitters

Answer 16

• make the receiving neuron less likely to fire an AP
• cause channels for negative ions to open
• lower resting potential of the neuron (more negative)
• GABA, serotonin, sometimes acetylcholine and dopamine

Question 17

Does inhibitory input inhibit all action potentials from firing?

Answer 17

No. Inhibitory input reduces the firing rate of the receiving neuron, however it doesn’t necessarily bring the firing rate to zero.