Neuronal signaling and transmission (Chapters 7, 8)

Question 1

What is the difference between synaptic/receptor potentials, and action potentials?

Answer 1

SP/RPs are slow, local potential changes that can be summed.

APs are brief, and actively propagated over long distances (i.e., from motor cortex all the way down)

Question 2

Describe the characteristics of the cell membrane.

Answer 2

Lipid bilayer with embedded proteins
Made up of polar heads and fatty acid tails (hydrophobic/hydrophilic)
Acts as a capacitor
Semi-permeable
Can be gated in different ways (voltage, transmitter, etc.)
Polarized with a resting potential of ~65 mV
Has selective permeability and active pumping mechanisms that maintain resting potential

Question 3

What different functions is the lipid bilayer of the cell membrane involved in?

Answer 3

Anchoring structural elements
Facilitate movement of non-lipid-soluble nutrients such as glucose
*Regulates passage of ions in and out of the cell

Question 4

Define capacitance, conductance, and resistance.

Answer 4

Capacitance - can store a charge
Conductance - allows flow of charge
Resistance - inverse of conductance, allows only a predictable amount of flow in response to a voltage

Question 5

Describe the three states of ion channels that allow them to act as variable resistors.

Answer 5

Open: low resistance, high conductance
Closed: high resistance, low conductance
Refractory: non-conductant, high capacitance

Question 6

Name different ion channel gating mechanisms.

Answer 6

Voltage-gated
Ligand-gated
Thermal-gated
Mechanic-gated

Question 7

Name an example of mechanic-gated channels.

Answer 7

Cochlear receptors, stretch receptors/baroreceptors.

Question 8

In what two ways can ion channels be selective?

Answer 8

Ion channels can be selective to size and also to specific type of molecule (e.g., Na+)

Question 9

Name the two passive factors that influence movement of ions across the membrane.

Answer 9

Concentration gradients (move from lesser concentration to greater concentration)
Potential gradients (move from negative to positive side)

Question 10

Describe the role of the sodium-potassium pump in maintaining the membrane resting potential.

Answer 10

The sodium-potassium pump /actively/ maintains the membrane resting potential at ~65mV by actively moving Na+ and K+ ions over in response to /passive/ movement of those ions through sodium and potassium channels.

Question 11

What is the difference between temporal and spatial summation?

Answer 11

Temporal summation = signals occurring close together in time but at slightly different times can reinforce each other.
Spatial summation = signals occurring in close proximity can reinforce each other.

Question 12

Describe the 4 steps in an action potential.

Answer 12

1. Cell is depolarized to -50 mV
2. Voltage-gated Na+ channels open and Na+ rushes in, depolarizing the cell
3. Slower voltage-gated K+ channels open and K+ is rushed out to compensate
4. Na+ channels close as K+ efflux continues, restoring steady state

Question 13

Describe saltatory conduction and why it is useful.

Answer 13

Saltatory conduction is useful because it is an efficient way to increase conduction velocity (can’t increase insulation thickness infinitely).
The AP spreads passively along internodes (segments with insulation) and is regenerated at the nodes.

Question 14

What are the five steps in chemical synaptic transmission?

Answer 14

1. Neurotransmitter has to be synthesized in the presynaptic ending or cell body
2. NT is concentrated presynaptically in vesicles for release
3. NT is released into synaptic cleft
4. NT binds post-synaptically to receptor molecules
5. Action of the NT is terminated through reuptake, degradation, or diffusion.

Question 15

Name the different ways that a neurotransmitter can be removed from the synaptic cleft.

Answer 15

Reuptake by the presynaptic terminal
Uptake by nearby glial cells
Enzymatic inactivation (within the cleft)
Uptake by the postsynaptic terminal
Diffusion out of the synaptic cleft

Question 16

What is the feedback system that allows NT production/release to be shut off? What happens if this feedback system isn’t working?

Answer 16

Retrograde signaling (on the presynaptic side - reduces effect of presynaptic action potentials); seizures

Question 17

What are neuropeptides?

Answer 17

Hormones that act as neurotransmitters in the brain (i.e., across the BBB).

Question 18

How does heroin produce a sense of euphoria?

Answer 18

Heroin produces a sense of euphoria by binding to receptors in the nucleus accumbens, which results in increased DA release in the reward pathway by decreasing GABA production (which would normally inhibit DA release).