Module 2

Question 1

How do neurons send messages?

Answer 1

Electrochemically

Question 2

What gives charge to the cell?

Answer 2

Ions

Question 3

How do we group ions?

Answer 3

Anions: negative
Cations: positive

Question 4

How do ions move in or out of the cell?

Answer 4

Ion channels

Question 5

Inside the cell

Answer 5

• Negative at rest
• Potassium (K+)
  -Proteins (-)

Question 6

Outside the cell

Answer 6

• Positive (+)
• Sodium (+)
• Chloride (-)
• Calcium (+)

Question 7

Voltage

Answer 7

Difference between inside and outside of the cell

Question 8

How do ions move?

Answer 8

Diffusion: Causes ions to spread towards a uniform concentration gradient
Electrostatic pressure: Causes ions to flow towards oppositely charged areas

Question 9

The threshold

Answer 9

Minimum electrical charge needed to trigger an action potential

Question 10

Depolarization

Answer 10

An increase in a neuron’s membrane potential, more positive

Question 11

Hyperpolarization

Answer 11

A decrease in a neuron’s membrane potential, more negative

Question 12

Gated

Answer 12

opens or closes in response to signals

Question 13

Selective permeability

Answer 13

allows k but not na to enter and exit freely

Question 14

Potassium leak channels

Answer 14

always open to k

Question 15

Voltage-gated sodium channels and voltage gated potassium channels

Answer 15

gate is opened when neuron reaches a certain voltage

Question 16

NA+/K+ Pump

Answer 16

Pumps out 3 NA+, brings in 2K+, repolarizing the membrane

Question 17

Steps of the action potential

Answer 17

1) Resting potential
2) Sub-threshold depolarization
3) Depolarization
4) Absolute refractory/repolarization
5) Relative refractory/hyperpolarization
6) Return to rest

Question 18

How do voltage-gated
sodium and voltage-gated
potassium channels
contribute to the different
phases of an action
potential? Be specific.

Answer 18

Depolarization Phase: Voltage-gated sodium channels open, allowing
Na+ ions to flow into the neuron, causing the membrane potential to
become more positive.

Repolarization Phase: Voltage-gated sodium channels close and
voltage-gated potassium channels open, allowing K+ ions to flow out
of the neuron, returning the membrane potential to a more negative
value.

Hyperpolarization Phase: Voltage-gated potassium channels remain
open slightly longer than necessary, causing an overshoot in the
membrane potential to more negative values before stabilizing at the
resting membrane potential.

Question 19

Types of dendritic spines

Answer 19

Stubby: Very small, precursor to other spines
Mushroom: More stable and can last for months, the in between
Filopodia: More than 2 micrometers

Question 20

Electrical synapses

Answer 20

Potential jumps directly to postsynaptic region without using chemicals

Question 21

Neurotransmitters

Answer 21

Chemical messengers that are sent from the presynaptic neuron to the postsynaptic neuron.

Question 22

Synaptic transmission events

Answer 22

1) Action potential arrives at the axon terminal
2) Voltage-gated calcium channels open and CA2+ ions enter
3) Synaptic vesicles fuse with the membrane and release transmitter into the cleft
4) Transmitter crosses the cleft and binds to postsynaptic receptors which opens the ion channels
5) Ion flow creates local EPSP or IPSP in the postsynaptic neuron
6) Transmitter is inactivated by enzymes
7) Transmitter may activate presynaptic auto receptors, decreasing its release

Question 23

Exocytosis is mediated by specialized proteins

Answer 23

SNARES and synaptotagmin

Question 24

Ligands

Answer 24

Fit into receptors binding sites to activate or block them

Question 25

What do the postsynaptic transmitters determine?

Answer 25

The action of the transmitter

Question 26

How do ligands bind ?

Answer 26

Endogenous ligands: Neurotransmitters and hormones produced by the body Exogenous ligands: Drugs and toxins from outside the body

Question 27

Agonists

Answer 27

Drug or toxin that mimics a neurotransmitter, elicits response

Question 28

Antagonists

Answer 28

Drug or toxin that interferes with neurotransmitter, blocks response

Question 29

Ionotropic receptors

Answer 29

Ligand-gated ion channel opens when bound by a transmitter

Question 30

Metabotropic receptors

Answer 30

Activate G proteins when bound by a transmitter

Question 31

EPSPs

Answer 31

Excitatory post-synaptic potentials caused by an influx of cations which depolarizes the membrane leading to an action potential.

Question 32

IPSPs

Answer 32

Inhibitory post-synaptic potentials caused by an influx of anions which hyperpolarizes the membrane making it less likely to fire an action potential. (Results from chloride ions entering the cell, making it more negative).

Question 33

End of synaptic transmission

Answer 33

Degradation—rapid breakdown by an enzyme, e.g., acetylcholinesterase (AChE) breaks down ACh and recycles it. Reuptake—transmitter is taken up by presynaptic receptors called transporters. Autoreceptors on presynaptic membrane bind transmitters; inform the cell about transmitter concentration in the cleft, which can be adjusted.