Lecture 4 (anatomy, cells, resting potential)

Question 1

What are the 3 main parts of the neuron?

Answer 1

1. Soma
2. Axon
3. Terminal

Question 2

What are the parts of the soma and its function?

Answer 2

1. dendrites (receive electrochemical signals)
2. spines (^^)
3. receptors (on the ends of D&S)

Question 3

What are the parts of the axon and its function?

Answer 3

1. axon hillock
2. myelin
3. nodes of ranvier
   Electrochemical signals move across the axon into the terminal

Question 4

What are the parts of the terminal and its function?

Answer 4

1. Vesicles
2. NTs
   The ec signal reaches the terminal, then moves through the membrane to the synapse to bind to the next neuron

Question 5

3 types of glial cells?

Answer 5

1. astroglial cells
2. oligodendroglial cells
3. microglial cells

Question 6

Astroglial cells –> job? how?

Answer 6

Job: form and maintain the blood brain barrier
How: surrounds blood vessels in the brain, plugs/patches holes

Question 7

Why is the blood brain barrier important?

Answer 7

Prevents bad things (bacteria, etc.) from getting into the brain. They stay in the blood vessels to get filtered out by the kidneys/liver

Question 8

Oligodendroglial cells –> job? how?

Answer 8

Job: form and maintain the myelin layer/sheath around the axons of neurons
How: they wrap around, coating the axon

Question 9

Why is myelin important?

Answer 9

1. insulating layer
2. Facilitates quicker transmission/communication between neurons
3. allows electrical impulses to transmit quickly
4. it is interrupted at the nodes of ranvier

Question 10

Microglial cells –> job? how?

Answer 10

Job: ‘immune system’ or ‘cleaners’ of the brain
eliminate foreign substances OUTSIDE of
neurons (floating in the brain)
How: they form macrophages
Phagocytosis: a cell ingests or engulfs other cells, particles, or bacteria to dispose of them

Question 11

Why are microglial / macrophages important?

Answer 11

Central role in protecting against infection in the brain

Question 12

3 states of a neuron:

Answer 12

1. Resting
2. Excited
3. Inhibited

Question 13

Define propagation:

Answer 13

the movement of signals between neurons

Question 14

Define resting potential

Answer 14

Electrical charge of the cell when it’s doing nothing

Question 15

What is the charge? Characteristics of RP?

Answer 15

-70mV

• unequal distribution of ions inside and outside
• inside is MORE NEGATIVE than outside

Question 16

Ions higher in concentration INSIDE the neuron? (resting)

Answer 16

High concentration of K+

also lots of proteins (A-)**
**proteins cannot move through channels, they’re too big

Question 17

Ions higher in concentration OUTSIDE the neuron? (resting)

Answer 17

High concentration of:
Na+
Cl-

Question 18

3 forces responsible for ion distribution?

Answer 18

1. concentration gradient
2. electrical gradient (electrostatic pressure)
3. Na+ / K+ pump

Question 19

Concentration gradient?

Answer 19

Want the same # of ions inside and outside

Question 20

Electrical gradient?

Answer 20

Want equal electrical charge inside and outside
Refers to opposite charges attracting each other

Question 21

Concentration gradient for K+ ?

Answer 21

• some K+ channels are open during resting potentials
• b/c there’s a high concentration of K+ inside, K+ moves OUT
• neuron loses + charges!!
  –> becomes more negative

Question 22

Electrical gradient for K+ ?

Answer 22

• when K+ leaves the cell (due to concent. grad.), cell becomes even more negative
• electrical gradient wants to balance in and out
• elect. grad. pulls K+ back IN

Question 23

Na+ / K+ pump?

Answer 23

• Na+ leaks in due to elect. grad. wanting more positive charge
• can’t have too much Na+ because the cell needs to be at -70mV to function at RP
• Na+ / K+ pump replaces Na+ for K+

3Na+ OUT –> 2 K+ IN

** it just needs to pump out something positive, its irrelevant why its Na+
** the pump has channels that allow movement for both Na+ and K+ –> most channels only allow movement for 1 ion

Question 24

What would happen if a toxin blocked the Na+ / K+ pump?

Answer 24

The cell would become too positive, it wouldn’t stay at -70mV, it wouldn’t be able to function at resting potential

Question 25

Given that there is a higher concentration of Ca++ outside the neuron than inside (at resting potential), how do the chemical and electrical gradients affect it?

Answer 25

• the chemical gradient would pull the Ca++ inside the neuron to have the same number of ions in/out
• this would make the neuron more positive
• the electrical gradient would pull the Ca++ back outside to keep the charge of the neuron at -70mV