week 1

Question 1

levels of research

Answer 1

1. basic: fundamental questions about how neurons work
2. translational: testing hypothesis about disease and potential therapies in the most appropriate animal models
3. clinical: testing potential therapies in humans

Question 2

6 electrical properties of neurons

Answer 2

1. have negative membrane potentials (voltages) at rest
2. Vrest is usually around -70mV but varies across cell types
3. generate AP to transmit electrical signals (not all neurons make APs tho)
4. APs an all of nothing event and always the same size
5. Vrest and AP are controlled by the activity of ion channels in the cell membrane
6. Ion channels come in many forms (diff combos of ion channels lead to diff signaling patterns in diff types of neurons)

Question 3

the Nernst equation

Answer 3

Question 4

simplified Nernst equation

Answer 4

Question 5

Goldman-Hodgkin-Katz (GHK) equation

Answer 5

Question 6

Feedback Cycles:

Answer 6

• responsible for membrane potential changes during an AP
• POSITIVE feedback loops create the AP
  
  • Na+ channel inactivation terminates the AP
  • later, large K+ currents return cell to Vrest
  • hyperpolarization removes inactivation from Na+ channels preparing neuron for next AP

Question 7

2 types of refractory periods and how they work:

Answer 7

ABSOLUTE REFRACTORY PERIOD
- time window after AP where no amount of stimulation can evoke another AP
1. inactivation of Na+ channels
2. slow deactivation of K+ channels (large outward current acting to hyperpolarize cell)
RELATIVE REFRACTORY PERIOD
- time window where another AP can be initiated with sufficiently large depolarization input currents
- amt required to override residual K+ current slowly decreases back to normal threshold as the K+ deactivates
- imposes a limit of how many AP/sec a neuron can produce (rate limit is about 1000 APs/sec)

Question 8

What are the main differences between electrical and chemical synapses?

Answer 8

Electrical:
- faster, inflexible, and more short term
- support synchronized firing of neurons in network
- common in invertebrates bc great for predetermined bx in short-lived organisms
- CANNOT support learning
Chemical:
- slower, more flexible, and longer effects
- REQUIRED for learning
- iontotropic or metabotropic

Question 9

2 types of neurotransmitter receptors

Answer 9

Question 10

2 types of post synaptic potentials

Answer 10

Excitatory Post Synaptic Potentials (EPSPs)
- goal is to convert chemical signal to graded electrical potential that may or may not cause an AP in the receiving neuron
Inhibitory Post Synaptic Potentials (IPSPs)
- when a NT causes a HYPERpolarization

Question 11

Inhibitory Post Synaptic Potentials (IPSPs):

Answer 11

• usually rely on ionotropic chloride ion channels
• when open they slightly hyperpolarize the membrane but mainly make it very difficult for a neuron to be excited by other inputs (suppress or prevent neural activity)
• GABA and Glycine are the most common inhibitory NTs (act on ionotropic Cl- ion channels in the post-synaptic membrane)

Question 12

Integration (summation)

Answer 12

• most neurons integrate many inputs from both excitatory and inhibitory synapses onto their dendrites

Question 13

2 types of neurotransmitters

Answer 13

small molecule transmitters
large molecule peptide transmitters

Question 14

small molecule transmitters:

Answer 14

1. amino acid transmitters: Glutamate, GABA, Glycine
   a. two types of ionotropic glutamate receptors (AMPA- and NDMA- type) plus 3 groups of metabotropic glutamate receptors (mGluR 1-8)
   b. GABA(a) and Glycine are ionotropic and GABA(b) is metabotropic
2. Acetocholine (nAChR-ionotropic and mAChR-metabotropic)
3. Biogenic amines: Norepinephrine (NE), 5-HT(seratonin), Dopamine (DA), Histamine
   - mostly metabotropic; broad actions throughout brain that influence arousal and motivation
4. ATP: the purines (purinergic) synapses:
   - two types P(2x) ionotropic and P(2Y) metabotropic
5. Gases: Nitric Oxide (NO) and Carbon Monoxide (MO)
6. Endocannabinoids: 2-AG and anandamide

Question 15

Large molecule Peptide Transmitters:

Answer 15

• short amino acid sequences
• all metabotropic
• > 60 amino acids or longer
• ex: substance P, orexin, opioids, oxytocin, vasopressin

Question 16

Structure of nicotinic Acetocholine receptors (nAChR)

Answer 16

• ligand-gated ion channel is compromised of 5 individually transcribed protein units
• channel is assembled in the membrane from subunits
• a-subunit contains the extracellular binding site for ACh

Question 17

Ionotropic GABA receptors:

Answer 17

• GABA(A) receptor
• same design as nAChR (5 subunits)
• binding sites for many clinically important molecules