Cells In The Nervous System

Question 1

What are the 2 main types of glial cells (including the subgroups for one type)

Answer 1

Macroglia
- astrocytes
- radial glia
-oligodendrocytes
-Bergmann glia
- ependymal cells
- tanycytes
- Schwann walls

Microglia

Question 2

Give some features of astrocytes

Answer 2

1. They have end feet which connect to blood vessels and neurons acting as an intermediary which can increase the neurons blood supply when needed
2. Different types of astrocytes are in different places eg. Fibrous astrocytes are present in white matter tracts, the spinal cord and optic nerve

Question 3

Give Some features of radial glial cells

Answer 3

1. They have two main processes between the ventricle wall and the developing brain
2. They act as scaffolding for developing brains and disappear once it is fully constructed

Question 4

Where would you find bergmann cells

Answer 4

They are present in the cerebellum, cell body and in pukinjie layer but some processes extend outside of the cerebellum

Question 5

What is and Where would you find the muller cell

Answer 5

It is a type of glial cell
Present in the retina

Question 6

What do ependymal cells do

Answer 6

They line the ventricles (which are fluid filled holes in the brain) and release cerebrospinal fluid

Question 7

Where are tanycytes found and what do they do

Answer 7

They line the 3rd ventricle wall and extend very long processes into the hypothalamus and they regulate food uptake

Question 8

Where are opigodendrocytes found

Answer 8

In white matter and they wrap around axons

Question 9

Where are microglia found and what do they act as

Answer 9

Microglia are found throughout the whole nervous system and act as immune cells for the nervous system

Question 10

What do Schwann cells do

Answer 10

There are 2 types of Schwann cells
1. Mylinating the entire cell wraps around and mylinates an axon above 1 micrometer in length
2. Non-mylinating this ensheathes multiple axons below 1 micrometer in length forming bundles

Question 11

What is the composition of myelin

Answer 11

70% fat and 30% protein

Question 12

How are oligodendrocytes and myelin related

Answer 12

Oligodendrocytes send out projections called myelin lamellae that can wrap around multiple axons

Question 13

How do myelin lamellae wrap around an axon

Answer 13

They underweave themselves so the newest myelin is always nearest the axon, due to the trapezoid shape of myelin lamellae the increase in thickness decreases with each wrap

Question 14

What is the name of the protein between myelin sheathes and the nodes of ranvier and what do they do

Answer 14

Anchoring proteins and they hold the myelin wrap in place

Question 15

What 2 values determine the length constant and what values maximise the length constant

Answer 15

1. Membrane resistance
2. Axiomatic resistance
   Increase in membrane resistance and decrease in axoplasmic resistance

Question 16

What would we do to conduction velocity of axoplasmic resistance decreases

Answer 16

Conduction velocity increases

Question 17

What is the g ratio

Answer 17

The ideal ratio of axon diameter too axon and myelin diameter (usually around 0.75 for all CNS axons)

Question 18

How big are most neurons cell bodies

Answer 18

Generally they are somewhere between 10-50 micrometers long

Question 19

What do microtubules in neurons do

Answer 19

They move proteins up and down the axon of a neuron with help from a protein called kinesin

Question 20

What are some of the different pieces of information used to classify neurons

Answer 20

1. The way the axon is projected
2. The dendritic pattern
3. The number of processes that they are involved in
4. Where they connect too

Question 21

What does a neurons cytoskeleton do

Answer 21

Provides structure
Aids in protein transport

Question 22

What is another name for the sodium pump

Answer 22

Na+/K+ ATPase

Question 23

What is the equation for membrane potential (Em)

Answer 23

Membrane potential = inside voltage (Vi) - outside voltage (Vo)

Question 24

Which two types of gradients affect movement of ions across membranes and what is the name of the equilibrium between these two gradients

Answer 24

Concentration gradient
Electrical gradient
The point of equilibrium between these two is called electrochemical equilibrium

Question 25

What is another word for equilibrium potential

Answer 25

Reversal potential/Ex

Question 26

What is the Nerst equation (to calculate reversal potential)

Answer 26

Ex = RT/ZF x log10([x]0/[x]1)
Where:
R = gas constant 8.315
T = temperature in kelvin
Z = valence of the ion
F = faradays constant 96500
[x]0 = extra cellular conc
[x]1 = intracellular conc

Question 27

When would you use the Nerst equation and when would you use the Goldman-Hodgkin-Katz equation

Answer 27

Nerst’s equation should be used when a membrane is only permeable to one ion the GHK equation should be used the rest of the time

Question 28

What are the differences between chemical and electrical synapses

Answer 28

1. Chemical use neurotransmitters electrical use ions
2. Chemical use exocytosis and post synaptic receptors electrical use gap junctions
3. Chemical are one way electrical are two way
4. Chemical are slower
5. Chemical are used throughout the body electrical are only present in a small number of areas

Question 29

What is the name of the protein used to make gap junctions in electrical synapses

Answer 29

Connexin

Question 30

What are the main differences between neuromuscular junctions and chemical synapses

Answer 30

1. The neurotransmitter is always ACh
2. The receptors are always nicotinic
3. Depolarisation of the muscle tissue is called an end-plate potential which then causes an action potential in the muscle causing it to contract
4. The ACh is broken down into choline (which is reuptaken) and acetic acid (which disperses throughout the body)

Question 31

How do nicotinic receptors function

Answer 31

They are ionotropic so when ACh binds they change in shape and allow molecules (usually Na+ ions) to pass across the membrane

Question 32

What effect are the following combinations likely to have:
1. Axon to dendrite
2. Axon to soma (cell body)
3. Axon terminal to axon terminal

Answer 32

1. Probably excitatory
2. Probably inhibitory with a large effect
3. Presynaptic inhibition (stops the signal ever being sent)

Question 33

How is information encoded in an action potential

Answer 33

Frequency highly stimulating things trigger a lot of action potentials but the size of the action potentials remain the same

Question 34

What are the 2 types of summation and what do they involve

Answer 34

1. Spatial summation - cumulative change in postsynaptic membrane potential because of mutiple, different simultaneous inputs
2. Temporal summation - cumulative change in postsynaptic membrane potential because of repeated inputs from one neuron

Question 35

How does the voltage gated Na+ channels 2 gates work in tandem

Answer 35

The activation gate opens when threshold is reached, at the same time the inactivation gate starts to close but moves relatively slowly