Histo - Nerve Flashcards

1
Q

What are the 2 main parts of the Nervous System?

What are the 2 types of cells?

What is the overall function of the Nervous System?

A

2 Parts of Nervous System:

  1. Central Nervous System (CNS)
    • Cerebrum
    • Cerebellum
    • Spinal Cord
  2. Peripheral Nervous System (PNS)
    • Cranial Nerves
    • Spinal Nerves
    • Ganglia

2 Main Cell Types:

  1. Neurons
  2. Glial Cells

Function:

  • Neurons interconnect to process & respond to info
    • Sensory/Afferent
    • Motor/Efferent
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2
Q

What are the characteristics of a Neuron?

What are the 4 types?

A

Basics:

  • Cell body (aka soma or perikaryon)
  • Projections
    • Axon = carries impulses away from soma
    • Dendrites = receive information for soma
  • Large cells
  • Large, euchromatic nuclei
    • Prominant nucleoli

Types of Neurons

  1. Multipolar
    • 2+ dendrites
  2. Bipolar
    • 1 dendrite + 1 axon
  3. Unipolar/Pseudounipolar
    • 1 process that splits into 2
  4. Anaxonic
    • Many dendrites, no axon
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3
Q

What are the characteristics of an Axon?

A

Basics:

  • Generate an action potential (AP)
  • AP begins at axon hillock

Transport of signal:

  • Occurs using motor proteins along Microtubules
    • Kinesin = anterograde (+)
    • Dynein = retrograde (-)
  • Arborize before synapsing
  • Terminate in a synapse or varicosity (release of neurotransmitters)
    • Synaptic bouton or terminal
    • Varicosity or en passant endings
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4
Q

What are the structural components of a neuron?

A
  1. Cell body
    • nucleus
    • nucleolus
  2. Dendrites
  3. Axon
    • Axon hillock
    • Neurolemmocytes (Schwann Cells)
      • myelin sheath
    • Neurofibril Node (Node of Ravier)
    • Terminal arborations + boutons
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5
Q

What are the 2 Types of Synapses?

A

Axons terminate on:

  • another neuron
  • an effector cell

2 Kinds of synapses:

  1. Electrical
    • transfer of ions thru gap junction
  2. Chemical
    • neurotransmitter release from pre-synaptic cell
    • binds to receptor on post-synaptic cell

3 Types of synapses

  1. Axodendritic
    • on a dendritic shaft or spine
  2. Axosomatic
    • on the soma of a neuron
  3. Axoaxonic
    • on an axon
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6
Q

What are the 3 types of Neurotransmitter Vesicles?

A
  1. Small clear (cholinergic)
    • Acetylcholine
  2. Small dense core (adrenergic)
    • Norepinephrine
  3. Large dense core
    • Substance P
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7
Q

What is this?

A

Small clear core

(Cholinergic)

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8
Q

What is this?

A

Small dense core

(Adrenergic)

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9
Q

What is this?

A

Motor Plate Ending

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10
Q

What are Glial Cells?

A

Glial cells AKA: Supporting Cells

Basics:

  • CNS:
    1. Astrocytes
      • support neurons
    2. Oligodendrocytes
      • make myelin
    3. Microglia
      • macrophages
    4. Ependymal cells
      • cover ventricles & central canal
  • PNS:
    1. Satellite cells
      • support neurons in sensory/autonomic ganglia
    2. Schwann cells
      • make myelin
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11
Q

What nervous system is this a part of?

A

Peripheral Nervous System (XS) - Dorsal Root Ganglia

  • Peripheral Nerve in XS:
    • Circular w/ axon in center
    • Myelyin & endoneurium around the whole
  • Peripheral Nerve in LS:
    • Wavy
    • May see nodes of Ranvier & axons (fingers touching)
    • Myelin washed out

Notes:

  • Ganglia:
    • cluster of neurons
    • satellite cells surrounding
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12
Q

What are the 4 structures visible in this image?

A
  • Myelin
    • washed out
  • Axon
    • dark dot

CT Layer around nerves:

  • Endoneurium
    • around a single process (axon)
  • Perineurium
    • around fascicle
  • Epineurium (not in the image)
    • around whole nerve
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13
Q

What is in this image?

A

Epineurium

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14
Q

How does myelination in the PNS occur?

A

Basics:

  • Occurs via Schwann Cells
  • More myelin = faster signal

Process:

  1. Schwann cell = aligned along the axon
    • extendas a wide cytoplasmic process to encircle it
  2. Growing process completely enclosed the axon
    • continuees its spiral extension
  3. Spiral wrappings become compacted layers of cell membrane (myelin)
    • cytoplasm leaves the growing process
  4. Mature Schwann cell myelin sheath has up to 100 lamellae
    • most cytoplasm in the outermost layer of cell body
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15
Q

How are Unmyelinated Axons formed in the PNS?

A

Basics:

  • Smaller in diameter
  • Slower signal (no myelin)
  • Single wrap of Schwann Cell

Process:

  1. Schwann cell starts to envelop multiple axons
  2. No myelin sheath wraps around the axons
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16
Q

What is the role of Oligodendrocytes in the CNS?

A
  • Cause myelation in the CNS
    • 1 oligodendrocytes = wraps many axons
17
Q

What is the Node of Ranvier?

A

Basics:

  • Unmyelinated region
  • Found between 2 schwann cells

Function:

  • Helps speed up the nerve conduction
  • Saltatory conduction
    • contains many Na channels
18
Q

What happens during Nerve Injury and Regeneration?

A

Basics:

  • PNS nerve can regenerate as long as the cell body is intact
  • CNS cannot regenerate!!

Process:

  • 2 weeks:
    • Nucleus peripheral
    • RER decreases
  • 3 weeks:
    • Muscle atrophy
    • Schwann cells proliferate
    • Axon grows
  • 3 months:
    • Both muscle & nerve are regenerated
19
Q

What is a Ganglia?

A

Basics:

  • Groups of neurons
  • Supporting cells (such as satellite cells)
  • Can be:
    • Senory
    • Sympathetic
    • Parasympathetic
20
Q

What can we see in this image?

A

Autonomic ganglion in epicardium

  • Nuclei of satellite cells
  • Axon
    • generally do not have a nucleus
21
Q

What is this?

A

Meissner’s Plexus in Jejunum in the Submucosa

  • Nerves in the GI
    • helps w/ digestion & to move food along
  • Surrounded by dense irregular CT
22
Q

What is this?

A

Auerbach’s Plexus in Ileum

  • Between layers of the muscularis externa
  • Neuron
    • surrounded by smooth muscle in LS & XS
23
Q

What are the components of the CNS?

A
  • Spinal cord
    • White matter
      • axons
      • outer
    • Gray matter
      • cell bodies
      • inner
  • Brain
    • White matter
      • axons
      • inner
    • Gray matter
      • cell bodies
      • outer
24
Q

What is this?

A

Cerebrum (CNS)

  • Gray Matter (LEFT)
    • Neuron Cell Bodies
  • White Matter (RIGHT)
    • Myelinated axons
25
Q

What is this?

A

Cerebellum (CNS)

  • Cerebellum (LEFT)
  • Purkinje cells in Cerebellum (RIGHT)
26
Q

What is this?

A