Cell 16

Front 1

What are the 3 main categories of neurons?

Back 1

1) sensory (afferent) neurons
2) motor (efferent) neurons
3) interneurons (connect sensory and motor within CNS)

Front 2

What are the 3 regions of a cell?

Back 2

1) cell body (soma)
2) dendrites
3) axons

Front 3

What are the peripheral neuroglia?

Back 3

- Schwann cells
- Satellite cells

Front 4

What do Schwann cells do?

Back 4

- surround axons, secretes myelin to insulate nerve

Front 5

What do Satellite cells do?

Back 5

- surround some of ganglia, no myelin, maintain environment

Front 6

What is the structural unit of the nervous system?

Back 6

The Neuron

Front 7

What are 2 properties of all neurons?

Back 7

1) irritability (receive stimulus)
2) conductivity (convey information as an impulse)

Front 8

What are the 3 types of neurons according to their number of axons/dendrites?

Back 8

1) Unipolar
2) Bipolar
3) Multipolar

Front 9

Unipolar Neurons

Back 9

- sensory
- part of process is the 'axon' part is the 'dendrite'
- soma is near the CNS

Front 10

Bipolar Neurons

Back 10

- 1 axon/1 dendrite
- Found in the retina II, olfactory mucosa I, and ganglion of the vestibulcochlear

Front 11

Multipolar axons

Back 11

- motor neurons and interneurons
- 1 axon and many dendrites

Front 12

What are microglia?

Back 12

- in the CNS
- macrophages
- mononuclear phagocytic system and role in inflammation (lysosomes, inclusions, vessicles)
- derived from mesenchyme

Front 13

What are oligodendrocytes?

Back 13

- myelinate many axons in the CNS

Front 14

What is myelin from?

Back 14

- cytoplasm of Schwann cells or Oligodendrocytes

Front 15

What are myelinated areas of the axon called?

Back 15

- internodal segments

Front 16

What are unmyelinated areas of the axon called? (between myelinated areas)

Back 16

- nodes of Ranvier

Front 17

What are ganglia?

Back 17

- collection of nerve cell bodies in the PNS

Front 18

What are some properties of axons?

Back 18

- 1 per neuron
- branch at right angles
- maintain consistent caliber
- no RER/ribosomes
- vessicles/mitochondria at synhapse
- contain more neurofilaments than microtubules
- can travel far
- convey impulse away from soma

Front 19

What are some properties of dendrites?

Back 19

- many per neuron
- branch at acute angles
- caliber varies, large near soma
- not myelinated
- many organelles, but no Golgi
- more microtubules than neurofilaments
- close to soma
- conveys impulse towards soma

Front 20

What is the functional unit of the nervous system?

Back 20

- circuit of neurons

Front 21

What are the 3 connective tissues that surround peripheral nerves and ganglia?

Back 21

- endoneurium
- perineurium
- epineurium

Front 22

Endoneurium wraps around?

Back 22

- individual axons
- delicate collagen, few fibroblasts

Front 23

Perineurium wraps around?

Back 23

- clusters of axons with endoneurium
- thick collagen, semipermeable layer

Front 24

Epineurium wraps around?

Back 24

- clusters of perineurium
- dense connective tissue with vessels

Front 25

Parts of a chemical synapse?

Back 25

- synaptic bulb (terminal button)
- synaptic cleft
- post-synaptic membrane

Front 26

What comprises the blood-brain barrier?

Back 26

- tight junctions (zona occludans) which prevent leaking into ECM
- end feet of protoplasmic and fibrous astrocytes also create barrier

Front 27

What happens in PNS injury and regeneration?

Back 27

- macrophages remove all axons anterograde the injury
- schwann cells proliferate and create a column
- axon produces sprouts
- sprouts try to find schwann column
- reaches effector organ
**return of motor function more likely if NOT an interneuron

Front 28

What occurs in chromatolysis?

Back 28

- nissle dissolution
- increase volume of the perikaryon (cytoplasm around nucleus)
- nucleus moves to the periphery

Front 29

Why does chromatolysis occur?

Back 29

- wounded nerve in the PNS, retrograde changes

Front 30

What are the central neuroglia?

Back 30

- microglia
- astrocytes
- oligodendrocytes
- ependyma cells

Front 31

What are the 2 components of all nervous tissue?

Back 31

1) Neurons
2) support cells (neuroglia)

Front 32

What are astrocytes?

Back 32

- CNS
- high number of projectiosn, cover vessel/neuronal process, contains bundles of intermediate filament, GFAP

Front 33

What are the 2 types of astrocytes and where are they located?

Back 33

1) protoplasmic (grey matter)
2) fibrous (white matter)

Front 34

Describe an electrical synapse

Back 34

-passage of ions between neurons for electron coupling
- no neurotransmitter release
- not polarized, flows both ways
- Smooth and cardiac muscles
- gap junction (connexon and connexins) form channels

Front 35

What is the ependyma?

Back 35

- CNS
- single layer of columnar cells that line ventricle and spinal canal
- apical surface has microvilli and cilia
- cells can be modified to produce CSF

Front 36

What are peripheral nerves?

Back 36

- bundles of nerve fibers held together by connective tissue

Front 37

What are the 2 types of axonal transport systems?

Back 37

- Anterograde (cell body to terminal synapse)
- Retrograde (terminal synapse to cell body)

Front 38

Describe anterograde axonal transport systems

Back 38

- kinesin, uses ATP
- 2 speeds
1) Fast: membrane organelles
2) Slow: growth

Front 39

Describe retrograde axonal transport systems

Back 39

- dynein, uses ATP
- only fast

Front 40

What are the 4 regions where schwann cell cytoplasm is extruded out of the schwann cell?

Back 40

1) outer collar cytoplasm
2) inner collar cytoplasm
3) Schmidt-Lanterman cleft (between schwann cell layers)
4) Perinodal cytoplasm (between schwann cell and node of ranvier)

Front 41

Describe chemical synapses

Back 41

- conduction of impulses depends on the release of a chemical substance across the cleft
- other substances can interrupt/ block the neurotransmitter
- polarized direction of impulse

Front 42

Where are electrical synapses found?

Back 42

- smooth and cardiac muscle

Front 43

What intermediate filament does microglia contain?

Back 43

- vimentin

Front 44

What is the relationship between oligodendrocytes and multiple sclerosis?

Back 44

- oligodendrocytes mylinate many axons, when they are injured many axons are affected which is what occurs in multiple sclerosis

Front 45

What are 2 areas in the PNS where neurons regularly regrow?

Back 45

1) olfactory mucosea: bipolar neurons replaced monthly
2) autonomic ganglia: replaced 'as needed'

Front 46

Why can PNS regenerate but not CNS?

Back 46

- injured axons have a difficult time regenerating sprouts that would be able to go through glial scarring
- lack paths/guid channels to get to the right spot
- CNS myelin inhibits axon regeneration
- if reconnections are incorrect, all of CNS is thrown off

Front 47

What are factors that favor return of function

Back 47

- cut/crush injury
- limited loss of internodeal tissue
- high neural sprouting
- purely motor/sensory nerve
- low scarring/blood loss
- no infection
- low axon damage