1: Neurons & Nervous Systems

Question 1

What is the CNS?

Answer 1

Central Nervous System

• All parts of the nervous system w/in the bone
• -Brainstem, spinal cord, thalamus, cortex etc
• Dermatomes = skin slices
• C1-C8, T1-T12, L1-L5, S1-S5

Question 2

What is the PNS?

Answer 2

Peripheral Nervous System

• All parts not w/in the bone
• -Spinal nerves, cranial nerves

Question 3

How are Neurons Similar to Other Cells?

Answer 3

• Enclosure: lipid bilayer membrane

- Organelles: nucleus, mitochondria etc

Question 4

How do Neurons Differ from Other Cells?

Answer 4

• Unique morphology
• -Dendrites: receive sigs from other neurs
• -Axons: send sigs to other neurs
• –Only neurons have an axon.. other cells can have AP but aren’t neurons

Question 5

What is Morphological Variation?

Answer 5

-Variation in the morphology of different cell types

Question 6

What are 3 Important Glial Cells?

Answer 6

Astrocyte
-Maintain ionic enviro (CSF)

Oligodendrocyte
-Myelinate neurons in CNS

Microglia
-Scavenge cellular debris

Question 7

What are the 4 Neuroscience Rules?

Answer 7

Symmetry
-Brain looks like a mirror image; can’t tell which side of the brain is which b/c of symmetry

Localization of Function

• Diff brain areas are responsible for diff functions
• Diff functions depending on area of the nervous system

Contralaterality
-Things get crossed in order to send movements down most of the time

Topography
-Neighbouring parts of the world map onto/ activate neighbouring parts of the nervous system

Question 8

Why is the Resting Potential Negative?

Answer 8

1. K concentration is greater inside that outside the neuron b/c of the action of the Na/ K pump
2. At rest, the neuron is primarily permeable to K b/c of the membranes leaky K chas
3. K diffuses out of the cell, making the inside negative
   - It’s flow is to leave b/c there are more K on the inside than the outside
   - -Follows its concentration gradient

Question 9

How do Neurons Pass Through the Impermeable Membrane?

Answer 9

Active Transport: Ion Transporters

• Actively move selected ions against their conc grad & create ion conc grads
• Requires energy (ATP)

Passive Transport: Ion Channels

• Selectively permeable to specific ions
• Some open under specific conditions, some are always open
• Allow ions to diffuse down their concentration gradient

Question 10

What is the Function of the Na/ K Pump?

Answer 10

-To restore resting potential by expelling 3 Na & taking in 2 K

Question 11

What is Electrochemical Equilibrium?

Answer 11

• The potential for 0 net flow of an ion

- -Assuming that the neuron was only permeable to the one ion

Question 12

What is Equilibrium Potential?

Answer 12

• The NUMERICAL potential at which the net flow os an ion would be 0
• -The numerical potential at which an ion is in electrochemical equilibrium

-Is unattainable however & can never be reached b/c a neuron will never be permeable to a single ion

Question 13

What 2 Things Establish Equilibrium Potential?

Answer 13

Diffusion

• K diffuses out of the cell, down its conc grad
• -Inside therefore loses charge & becomes more negative
• Stops when K doesn’t wanna leave anymore b/c out & in are pretty much even
• -This means no net flow, still random flow though

Electrostatic Force

• Opposite charges attract
• Coulomb Force Law: force of attraction b/w 2 targets
• K diffuses out & inside becomes - compared to outside, K is then attracted to the - inside

Question 14

What Does the Nernst Equation Calculate?

Answer 14

-Equilibrium potential for any ion, X