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Principles of Neuronal Function and Dysfunction > Neurons: Design Principle > Flashcards

Neurons: Design Principle Flashcards

1
Q

Different neuron types have different ?

A

Number of processes extending from the soma, reflecting evolutionary and functional differences

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2
Q

What are some types of neurons ?

A
  • Unipolar
  • Bipolar (Information conveying)
  • Multipolar
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3
Q

Neurons are just like other cells, but ?

A

With ‘specialisation’ for rapid communication

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4
Q

What are two particular specialisations that neurons have ?

A
  • Morphological features

- An electrically excitable membrane

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5
Q

The contents of a neuron are contained within?

A

A plasma membrane

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6
Q

This plasma membrane is a lipid bilayer structure which forms a hydrophobic barrier. This is comprised of ?

A

Amphipathic lipids –eg.phospholipids - and proteins (~20% of membrane composition)

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7
Q

Is this plasma membrane stable ?

A

It is stable but fluid structure, where phosphate head groups face the aqueous environment and fatty acid tails face each other

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8
Q

What does this plasma membrane act as ?

A

The membrane acts as a barrier to water-soluble ions and charged molecules

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9
Q

What is the only way that they can cross the plasma membrane ?

A

Via membrane-spanning proteins

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10
Q

The cytoplasm is the contents of the inside of the cell. What can this be sub-divided into ?

A
  1. Cytosol
    Aqueous component of the cytoplasm
  2. Everything else:
    Cytoskeleton, membranous organelles and vacuolar apparatus (Golgi, tubules, vesicles, lysosomes, endoplasmic reticulum).
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11
Q

The cytoskeleton determines?

A

Cell shape

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12
Q

What are three main components of cytoskeleton?

A
  • Microtubules: long scaffolds involved in cell stability and transport mechanisms; dynamic
  • Neurofilaments: bones of the cytoskeleton and structural support for axons – shorter; numerous and stable
  • Actin: much shorter and concentrated at peripheral structures – for example, synapses where they can influence function; dynamic
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13
Q

Explain the processes of active transport for transporting proteins and organelles ?

A

SLOW: Cytoskeletal elements (e.g.actin), enzymes and some proteins move anterogradely at 0.2-2.5 mm/day. Involves mechanisms including microtubule slipping.
FAST: Membranous organelles (vesicles, mitochondria etc.) are moved both anterogradely and retrogradely at >400mm/day requiring ATP and molecular motors on microtubules

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14
Q

Name some transport proteins and explain ?

A

Ion channel:
Allows the passive flow of ions through the membrane
Ion pump:
Moves ions across the membrane against a concentration gradient
Other transporters:
Facilitates transfer of molecules across the membrane

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15
Q

What special proteins allows passive diffusion of ions ?

A

Ion channels

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16
Q

What is ion flow determined by?

A

Electrochemical driving forces

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17
Q

What are leakage channels ?

A

Some channels which are open all the time

18
Q

Most channels are gated, meaning ?

A

They can be opened or closed

19
Q

How is Gating achieved ?

A

By a conformational change in the structure of the protein

20
Q

What is transport protein that uses energy to move ions across the membrane ?

A

Ion pumps

21
Q

In Ion pumps, ions do not flow freely but ?

A

Can be actively transported against their electrochemical gradient and used to establish a high concentration of ions on one side of the membrane

22
Q

Name some signalling proteins and explain ?

A

Receptors:
- Binds a signalling molecule and initiates a neuronal response
G Proteins:
- Initiates a cascade of biochemical reactions triggering a neuronal response when triggered by a signalling molecule
Other enzymes:
- Catalyses biochemical reactions associated with signalling

23
Q

Name some binding proteins and explain ?

A

Adhesion proteins:
- Anchor the neuron to other cells
Cytoskeletal binding proteins:
- Anchor the cell membrane to the internal cytoskeleton

24
Q

Explain how Glial cells are similar to neurons in a number of ways:

A
  1. Electrical potential across their membrane which can be varied
  2. Respond to various chemicals
  3. Some have a similar structure with a cell body and neurite branches
25
Q

What is a difference between Glial cells and neurons ?

A

They do not show active electrical responses (an ‘action potential’) like those exhibited by neurons

26
Q

What are the four main classes of Glial Cells ?

A
  1. Microglia
  2. Oligodendrocytes
  3. Schwann Cells
  4. Astrocytes
27
Q

What are Microglia ?

A

They are small and mobile with a defensive function, consuming cellular debris

28
Q

What do both Oligodendrocytes and Schwann Cells generate ?

A

Myelin, the insulating material that allows rapid conduction of electrical signals

29
Q

What do single oligodendrocytes do to axons compared to Schwann Cells ?

A

Single oligodendrocytes wrap many axons, Schwann Cells wrap only one

30
Q

Is Myelin continuous ?

A

Myelin is not continuous but separated by unmyelinated gaps, called nodes of Ranvier

31
Q

In nodes of Ranvier, the density of Na+ channels is much higher which means ?

A

That the nodes are more easily excited

32
Q

What does this high density mean for the nerve impulses?

A

That they can travel much more quickly in myelinated axons because it jumps between nodes - a process called saltatory conduction

33
Q

What is the number of myelin layers proportional to ?

A

The axon diameter and small axons do not have myelin at all

34
Q

What is the shape of Astrocytes ?

A

Star-shaped glia: they are probably present in similar numbers to neurons in the brain

35
Q

Where do Astrocytes have an important role at ?

A

They have a much more important role in brain function

36
Q

What kind of roles fo Astrocytes have ?

A

Homeostatic and buffering roles

37
Q

Astrocytes have large numbers of thin processes that ?

A

Enfold brain blood vessels and ensheath synapses meaning they can control extracellular ions, neurotransmitter etc,. particularly at their end feet structures

38
Q

What is one role of the Astrocytes ?

A

One role is K+ buffering allowing the excitability of neurons to be modulated

39
Q

What can Astrocytes also regulate ?

A

Astrocytes also regulate neurotransmitter concentrations in the brain. For example, high-affinity transporters located in the astrocytes plasma membranes rapidly clear the neurotransmitter glutamate from the synaptic cleft; similar effects occur through degradation of dopamine, serotonin and others, and help to mop up toxic oxygen free radicals

40
Q

Through their associations with blood vessels, astrocytes also roles in ?

A

Mopping up macromolecules that might otherwise cross the blood-brain barrier

Principles of Neuronal Function and Dysfunction (15 decks)

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