L9 - Neurons and Glia

Question 1

Structure of Neurons:

Answer 1

All have RER, ribosomes, Nucleus, Golgi Apparatus and Mitochondria. RER and ribosomes used for translation. To make more proteins and allow membrane to maintain depolarisation (proton pumps and channels).

Unique to neuron:
Dendritic spine (Increases SA of dendrite and is where most synapses form).
Dendrite (extension of cell body).
Synapse
Axon Hillock (swelling where axon meets cell body).
Axon (myelinated by schwann cell for insulation).

Allows unidirectional passage of information. AP cannot move in more than 1 direction.

Question 2

Schwann Cells Structure:

Nodes of Ranvier:

Saltatory Conduction:

Answer 2

Schwann cells Structure:
Schwann cells wrap its membrane around axon. On top is cytoplasm.

Nodes of Ranvier:
At nodes, if positive inside, action potential. If negative inside then no action potential.

Saltatory Conduction:
AP travels down axon leaping.

Question 3

Nissl Staining and Chromatolysis:

Answer 3

Nissl Staining shows if neuron is damaged or not. Loss of colour as ribosomes fall off from RER so not active anymore. Stain neurons and bind to RER as more translationally active.
Chromatolysis shows that apoptosis will occur.

Question 4

5 types of synapses:

Answer 4

Converts electrical to chemical to electrical energy.

1. Axo-dendritic
2. Axo-somatic
3. Axon-axon hillock
4. Axon-axon terminal
5. Axon-nodes of ranvier

Question 5

Types of Neurons:

Answer 5

Sensory (afferent) - Generate AP towards CNS.

Motor (efferent) - Generate AP away from CNS.

Interneuron - In CNS. Connect one neuron to another.

Multipolar - most neurons in CNS e.g. motor neurons.

Bipolar - e.g. sensory neuron in olfactory system and retina

Unipolar (pseudounipolar - one process splits to two) - neurons with single process. Divide to two branches. e.g. most sensory neurons where one branch extends to CNS and another to periphery.

Primary somatic sensory neuron (PSSN) are pseudounipolar neurons that go to periphery.

Question 6

Convergence and Divergence:

Neural Network:

Answer 6

Convergence and Divergence:
Convergence - many to 1
Divergence - 1 to many

Neural Network:
Can have multiple synapses so cause neural network.
Different neurons are stimulated due to different neuronal pathway so more than 1 pathway of neural network. This produces different responses.

Question 7

Neuroglia: Types

Answer 7

Provide support for neurons. It is the predominant class of non-neuronal cells in the NS.

Major CNS classes:
Astrocytes
Oligodendrocytes
Ependymal cells
Microglia

Major PNS class:
Schwann Cells

No Schwann cells in CNS, only in PNS. Astrocytes and Co. are in CNS and not in PNS.

Question 8

Astrocytes:
Structure:

Homeostatic roles:

Answer 8

Structure: 
Star shaped and most found in brain.
Fill gap between neurons. 
Protect blood brain barrier.
Form glial lamitans (section through cortex). 

Homeostatic roles:
Regulate H20, K+, NT levels.
Inhibit axon regeneration.

Question 9

Oligodendrocytes:

Answer 9

Many branched cells.
Can myelinate more than one axon in CNS.
Inhibits axon regeneration.

Question 10

Ependymal Cells:

Answer 10

Line brain ventricles and spinal cord.
Specialised cells can form choroid plexus which makes CSF.
Have neural stem cells in sub-ependymal zone which make neurons.

Question 11

Microglia:

Answer 11

Specialised macrophages that remove foreign molecules or microorganisms in CNS.

Question 12

Schwann Cells:

Answer 12

They form myelin sheath.
Cause saltatory conduction.
Allow axon regeneration unlike astrocytes and oligodendrocytes.
Can also be phagocytic.