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Flashcards in LEC-1 Neurohistology Deck (71):
1

The CNS is composed of white and grey matter. Which is the cells and which is the fibers?

White matter = fibers

Grey matter = cells

2

What are the major cell types of nervous tissue?

Neurons (FPM's)

Glial cells

Vascular cells

Fibroblasts

3

What are the 3 basic types of neurons?

Multipolar

Pseudounipolar

Bipolar

4

What is the basic type of neuron that is motor, ANS and somatic?

Multipolar

5

What is the basic type of neuron that is sensory, with various endings?

Pseudounipolar

6

What is the function of bipolar neurons?

Special sensory

7

What is the karyon?

Nucleus of a neuron

  • Prominent nucleolus
  • Euchromatin

8

What are the fibers ("processes") that extend from neurons?

Dendrites

Axons

  • Collaterals
  • Synaptic bouton

9

What is Nissl?

RER of a neuron

Makes protein/peptide transmitters

10

What are the cellular inclusions in neurons?

Lipofuscin (yellow/orange)

  • Indigestible debris
  • More with AGE

11

Besides lipofuscin, what is another inclusion seen in neurons?

Melanin pigment

  • Locus ceruleus (blue locus) in Pons
  • Substantia Nigra (black substance) in midbrain

12

True/False: Unidirectional flow is a feature of axons.

True.

13

On an axon, where are many Na+ channels found?

At Nodes of Ranvier

14

Why is saltatory conduction only observed in axons?

They have Nodes of Ranvier

15

What produces the furry appearance of dendrites?

Extensive arborization makes large and small branches (Dendritic spines), e.g. the dendritic tree of a neuron in cerebellum.

16

Describe the two major aspects of anterograde axonal transport.

Fast = 200-400 mm/day (Vesicles, mitochondria)

Slow = 2-4 mm/day (actin, neurofilaments, enzymes)

17

How much Nissl substance is in the axon hillock and axon, relative to the perikaryon?

None.

18

A patient has loss of memory due to degeneration of dendrites which have: 1. Synaptic vesicles, myelinated internodes 2. Anterograde transport, saltatory conduction 3. Golgi apparatus, lipofuschin granules 4. Nissl, spines, many tapering processes 5. Euchromatin, a prominent nucleolus.

4. Nissl, spines, and many tapering processes are features of dendrites.

19

Each oligodendrocyte myelinates (one axon/many axons) in the CNS.

Many axons.

20

Myelin contributes to the "white" appearance of fresh white matter. What does it look like in the Weigert stain?

Myelin stains BLACK with Weigert stain.

21

Myelin is 80% ____ and 20% ____.

80% Lipid

20% Protein (Myelin Basic Protein MBP)

22

Myelin in the CNS is similar to in the PNS. What forms the Major Dense Line?

The cytoplasmic surfaces coming together.

23

Axosomatic synapses are usually (excitatory/inhibitory).

Inhibitory

24

Axodendritic synapses are usually (excitatory/inhibitory).

Excitatory

25

Axoaxonic synapses are usually (excitatory/inhibitory).

Inhibitory

26

What protein causes the clustering of vesicles at the synapse?

Synapsin-1 (phosphorylation moves vesicles to synapse)

27

What neurotransmitter is used between preganglionic synapses onto postganglionic neurons?

Acetylcholine

28

What is the common neurotransmitter at postganglionic sympathetic synapses?

Norepinephrine

29

What is the exception to the rule that norepinephrine is the neurotransmitter of postganglionic sympathetic synapses?

Acetylcholine, not norepinephrine, is the neurotransmitter of postganglionic sympathetic synapses at eccrine sweat glands.

30

What is the most common excitatory neurotransmitter of CNS?

Glutamic acid (glutamate)

31

What is the most common inhibitory neurotransmitter of CNS?

GABA

32

A cluster of neurons outside of CNS is called a ganglion. What is it called inside CNS?

Nucleus

e.g. caudate nucleus, nucleus gracilis

33

The grey matter is composed of a thin layer of cells in the edge of cerebrum and cerebellum (the CORTEX) and where else?

Nuclei (since grey matter is the neuron cell bodies)

34

What are the 3 "famous" motor neurons and where are they?

1. Purkinje (cerebellum)

2. Pyramidal (cerebrum)

3. Alpha motor neurons (spinal cord)

35

Describe interneurons.

They communicate with the CNS between 2 neurons, usually inhibitory (inhibitory interneurons)

36

Describe the Purkinje neurons.

Located in the cerebellum (largest neurons in the cerebellum), they have a fan-shaped dendritic arbor with >10K dendritic spines per Purkinje neuron.

37

Describe pyramidal neurons.

Large motor neurons in the cerebral cortex. Shaped like a pyramid, with a large apical dendrite that projects to the pial surface. Axons are sent (long) to alpha (lower) motor neurons in brainstem or spinal cord.

38

Pyramidal neurons are (upper/lower) motor neurons.

Pyramidal neurons are upper motor neurons.

39

Where is the neuron in the following image located?

Q image thumb

In cerebral cortex

This is a pyramidal motor neuron (Upper motor neuron)

40

Where is the neuron in the following image located?

Q image thumb

In cerebellar cortex

This is a Purkinje motor neuron

41

Where are alpha motor neurons located?

In ventral horn of spinal cord and in brainstem motor nuclei.

42

Where do alpha motor neurons (lower motor neurons) send their axons?

To skeletal muscle.

43

A high school student developed spastic paralysis several weeks after an automobile accident where she suffered loss of upper motor neurons found in her cerebral cortex. These neurons are known as...?

Pyramidal cells

44

What is the location of cell bodies of preganglionic ANS neurons?

Brainstem nuclei

-or-

Lateral horn of spinal cord

45

Where do the axons of preganglionic ANS neurons go?

To "postganglionic" neurons in PNS ganglia.

46

What is the transmitter of Preganglionic neurons?

Acetylcholine (where it is sympathetic OR parasympathetic)

47

Describe the common features of glial cells.

  • 10:1 ratio with neurons
  • Glial cells proliferate (unlike FPM neurons)
  • Some can migrate
  • Communicate via gap junctions
  • They react to injury or disease by increasing number of processes and enlarging cell bodies

48

What are the types of glia in the CNS?

Macroglia (neuroectoderm origin)

1. Astrocytes

  • Protoplasmic (grey matter)
  • Fibrous (white matter)

2. Oligodendroglia (oligodendrocytes)

  • White and grey matter

Microglia (Bone marrow origin)

49

Identify the glial cell in the following image.

Q image thumb

Protoplasmic astrocyte (In grey matter)

50

Identify the glial cell in the following image.

Q image thumb

Fibrous astrocyte (in white matter, note processes on capillary)

51

Identify the glial cell in the following image.

Q image thumb

Microglia (migrate from bone marrow)

52

Identify the glial cell in the following image.

Q image thumb

Oliogodendroglia

53

What is the largest type of glial cell?

Astrocytes

54

Describe astrocytes.

There are protoplasmic and fibrous types.

  • Euchromatic nucleus
  • Usually NO visible nucleolus (unlike neuron)

55

What is the marker for astrocytes?

Glial fibrillary acidic protein (GFAP)

  • 10 nm intermediate filament
  • Increases in amount during reactivity

56

What are the functions of astrocytes?

1. Scavenge for ions and neurotransmitters:

  • K+
  • GABA, Glutamate (prevent excitatory toxosis)

2. Glycogen storage and release (nutritive to neurons)

3. "Tell" endothelial cells to form BBB

4. Glial scar formation (prevents CNS axon regeneration)

5. Produce and secrete cytokines (e.g. S-100b)

57

What is the significance of the vascular end feet of astrocytes that contact capillaries?

They "tell" the endothelial cells to form the BBB

58

Describe oligodendroglia.

  • Few processes
  • Pyknotic nucleus, small cell body, dense cytoplasm
  • Near neurons (like satellite cells)
  • NO basal lamina (unline Schwann cells)
  • Myelinate MANY axons (not all cytoplasm squeezed out)

59

Describe microglia.

  • Migrate and phagocytose
  • Bone marrow origin
  • Infected by HIV
  • Found in grey and white matter
  • MHC-1 and MHC-II (antigen-presenting)
  • Similar to a macrophage, except small, and in brain
  • Crescent to triangular nucleus (pycnotic)

60

What is neuropil?

  • Substance between cells
  • Collection of neuronal and glial processes

61

Describe ependymal cells.

  • Line ventricles (brain) and central canal (spinal cord)
  • Brain-CSF barrier (tight junctions)
  • Ciliated (move CSF)

62

Describe choroid plexus.

  • Pia+ependyma+blood vessel
  • In ventricles
  • Blood-CSF barrier
  • Produces CSF

63

Describe the BBB.

Capillary endothelial cell tight junctions ARE the barrier

  • Astrocytes signal endothelial cells to form tight junctions
  • Fused basement membranes of endothelial cell and astrocytes
  • ABSENT in circumventricular organs (e.g. Pineal gland)

64

What is the function of fibroblasts in CNS?

Make CNS meninges:

  • Pia (simple squamous, adherent to brain)
  • Arachnoid (vessels travel through, spider-web like)
  • Dura (tough outer coat; cranial = periosteal + meningeal)

65

What is the "best" brain tumor to have?

Meningioma. Doesn't invade substance of brain itself. Indentation is dangerous, but these can be removed.

66

Microglia, unlike the other glia, originate in the ________________.

Bone marrow

67

_____________ are the only portion of the CNS capable of infection by HIV.

Microglia

68

What is the result if there is a problem with the Purkinje neurons in the cerebellum?

Ataxia (drunk gait)

Tremors

69

What is the result if there is a problem with the pyramidal neurons of the cerebrum?

Spasticity (excessive muslce contraction)

70

What is the result if there is a problem with the alpha motor neurons of the brain stem or spinal cord?

Muscle twitching

71

What is the perikaryon?

Cell body of a neuron

Organelles, inclusions