Lecture 7

Question 1

Neurons

Answer 1

Can be classified by:
- Their function (sensory, motor, interneurons…)
- Their shape (unipolar, monocular, bipolar)
- The neurotransmitter they express
- Their gene expression patterns
- …

Question 2

Dendrites

Answer 2

• Branching projections of the neuron that collect information from other neurons
• Input
• Have neurotransmitter receptors

Question 3

Soma

Answer 3

• Cell body
• Contains the nucleus and integrates information from the dendrites
• Integration

Question 4

Axon

Answer 4

• Conducts the neural signal across a long distance
• Conductance
• Can vary from millimeters to many centimeters long

Question 5

Glia Cells

Answer 5

• Cells that are not neurons
• Estimated to be about half of the cells in the brain
• Do not fire action potentials

Question 6

Astrocytes

Answer 6

Provide structural support to the neuron/blood vessel, balance chemical concentrations outside neurons, injury repair

Question 7

Oligodendrocytes

Answer 7

Wrap neurons with myelin (myelination), speeding up neuronal electrical signaling

Question 7

Microglia

Answer 7

Provide immune defense by consuming and destroying foreign bodies in the brain; smaller than astrocyte

Question 8

Synapse

Answer 8

• Spaces between the axon terminals of one neuron and the dendrites of another neuron
• Where neurotransmitters are released between pre-synaptic to post-synaptic neurons

Question 9

Voltage

Answer 9

Difference in electric potential between two points (water dam as an example)

Question 10

Resting Potential

Answer 10

• Voltage of a neuron at rest; before the action starts
• ~-70mV for neurons
• Is determined by ion concentrations

Question 11

Important Ions

Answer 11

Na+, K+, Cl-, Ca2+

Question 12

Chemical Forces

Answer 12

Ions move from high to low concentration

Question 13

Osmosis

Answer 13

The spontaneous net movement or diffusion of solvent molecules through a selectively-permeable membrane from a region of high water potential to a region of low water potential, in the direction that tends to equalize the solute concentrations on the two sides

Question 14

Electrical Forces

Answer 14

Ions are repelled by ions with the same charge and attracted to those with opposite charges

Question 15

Na+/K+ Pump

Answer 15

• Protein that sits in between the membrane of a neuron
  Ejects 3 Na+ ions and pulls in 3 K+ ions
• Energy (ATP) is needed for this process
• Results in net negativity inside the neuron

Question 16

Action Potential Steps

Answer 16

1. Depolarization above threshold ~-55mV opens voltage-gated Na+ channels
2. Sodium rushes into the cell due to concentration gradient resulting in further depolarization
3. At peak voltage ~30mV, Na+ channels close, this stops depolarization and starts repolarization
4. Starts refractory period, lasting about 1ms
5. The high voltage opens voltage-gated K+ channels
6. K+ leaves the cell strengthening repolarization
7. Hyperpolarization slowly closes K+ channels (afterhypoerpolarization)
8. inactivated sodium channels cause a refractory period where a new AP cannot be initiated
   - Speed of action AP’s is ~1000AP/s

Question 17

Depolarization

Answer 17

• Membrane potential becomes less negative

Question 18

Hyperpolarization

Answer 18

• Membrane potential becomes more negative

Question 19

Neuron Doctrine

Answer 19

Established by Ramon y Canal, states that the brain is made of many small, discrete cells

Question 20

Terminal branches/axon terminals

Answer 20

• Releases information to dendrites of other neurons
• Output
• Voltage-gated Ca2+ channels are found here

Question 21

All-or-None Principle

Answer 21

Action potential either happens or does not, there are no partial action potentials

Question 22

Why are Pufferfish Poisonous?

Answer 22

• Contains lethal tetrodotozin (TTX)- a Na+ channel blocker
• Blocks action potentials
  -Causes paralysis and respiratory failure

Question 23

Lidocaine and Novocaine

Answer 23

• Local anesthetics
• Block Na+ channels, preventing action potentials in pain-sensitive neurons, blocking signaling to the brain
• Used to relieve pain

Question 24

Axon Hillock

Answer 24

- Where AP is generated - Between soma and axon - The depolarizing current formed by the Na+ influx flows down the neuron, depolarizing the next part of the neuron - Na+ channel inactivation prevents action potential reversal

Question 25

Nodes of Ranvier

Answer 25

a gap in the myelin sheath of a nerve, between adjacent Schwann cells.

Question 26

Saltatory Conduction

Answer 26

describes the way an electrical impulse skips from node to node down the full length of an axon, speeding the arrival of the impulse at the nerve terminal in comparison with the slower continuous progression of depolarization spreading down an unmyelinated axon

Question 27

Myelin

Answer 27

- Fatty substance wrapped around axons - Like insulation around electrical wire - In CNS formed by oligodendrocytes; in PNS: schwann cells - Speeds up AP from 2m/s to 120m/s

Question 28

Multiple Sclerosis

Answer 28

- Disease in which the myelin around neurons degrades - Symptoms include vision problems, muscle weakness, trouble with movement and coordination, cognitive impairments

Question 29

Neurotransmission/Neurotransmitter Release Steps

Answer 29

- Release of a neurotransmitter from a pre-synaptic to a post-synaptic neuron 1. Arrival of the action potential opens voltage gated Ca2+ channels 2. Ca2+ rushes into the neuron 3. Vesicles release neurotransmitter into synaptic cleft 4. Neurotransmitter binds to postsynaptic receptors

Question 30

Pre-Synaptic Neurons

Answer 30

- Neuron firing the signal

Question 31

Post-Synaptic Neurons

Answer 31

- Neuron receiving the signal

Question 32

Synaptic Cleft

Answer 32

- Space in between 2 neurons where neurotransmission occurs

Question 33

Vesicles

Answer 33

- Small lumps of neurotransmitter

Question 34

Ionotropic Receptors

Answer 34

- Causes an opening of an ion channel upon neurotransmitter binding onto post-synaptic neuron -

Question 35

Metabatropic Receptors

Answer 35

a type of membrane receptor that initiates a number of metabolic steps to modulate cell activity

Question 36

EPSP

Answer 36

- Excitatory post-synaptic potential - Causes depolarizations - Makes post-synaptic cell more likely to fire an AP

Question 37

IPSP

Answer 37

- Inhibitory post-synaptic potential - Causes hyperpolarizaiton - makes postsynaptic cell less likely to fire and AP

Question 38

Post-Synaptic Potentials

Answer 38

Ion entry/exit following neurotransmitter binding onto receptors changes membrane potential