Histo - Nerve Flashcards
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?
2 Parts of Nervous System:
-
Central Nervous System (CNS)
- Cerebrum
- Cerebellum
- Spinal Cord
-
Peripheral Nervous System (PNS)
- Cranial Nerves
- Spinal Nerves
- Ganglia
2 Main Cell Types:
- Neurons
- Glial Cells
Function:
- Neurons interconnect to process & respond to info
- Sensory/Afferent
- Motor/Efferent
What are the characteristics of a Neuron?
What are the 4 types?
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
- Multipolar
- 2+ dendrites
- Bipolar
- 1 dendrite + 1 axon
- Unipolar/Pseudounipolar
- 1 process that splits into 2
- Anaxonic
- Many dendrites, no axon
What are the characteristics of an Axon?
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
What are the structural components of a neuron?
- Cell body
- nucleus
- nucleolus
- Dendrites
- Axon
- Axon hillock
- Neurolemmocytes (Schwann Cells)
- myelin sheath
- Neurofibril Node (Node of Ravier)
- Terminal arborations + boutons
What are the 2 Types of Synapses?
Axons terminate on:
- another neuron
- an effector cell
2 Kinds of synapses:
- Electrical
- transfer of ions thru gap junction
- Chemical
- neurotransmitter release from pre-synaptic cell
- binds to receptor on post-synaptic cell
3 Types of synapses
- Axodendritic
- on a dendritic shaft or spine
- Axosomatic
- on the soma of a neuron
- Axoaxonic
- on an axon
What are the 3 types of Neurotransmitter Vesicles?
-
Small clear (cholinergic)
- Acetylcholine
-
Small dense core (adrenergic)
- Norepinephrine
-
Large dense core
- Substance P
What is this?
Small clear core
(Cholinergic)
What is this?
Small dense core
(Adrenergic)
What is this?
Motor Plate Ending
What are Glial Cells?
Glial cells AKA: Supporting Cells
Basics:
-
CNS:
- Astrocytes
- support neurons
- Oligodendrocytes
- make myelin
- Microglia
- macrophages
- Ependymal cells
- cover ventricles & central canal
- Astrocytes
-
PNS:
- Satellite cells
- support neurons in sensory/autonomic ganglia
- Schwann cells
- make myelin
- Satellite cells
What nervous system is this a part of?
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
What are the 4 structures visible in this image?
-
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
What is in this image?
Epineurium
How does myelination in the PNS occur?
Basics:
- Occurs via Schwann Cells
- More myelin = faster signal
Process:
- Schwann cell = aligned along the axon
- extendas a wide cytoplasmic process to encircle it
- Growing process completely enclosed the axon
- continuees its spiral extension
- Spiral wrappings become compacted layers of cell membrane (myelin)
- cytoplasm leaves the growing process
- Mature Schwann cell myelin sheath has up to 100 lamellae
- most cytoplasm in the outermost layer of cell body
How are Unmyelinated Axons formed in the PNS?
Basics:
- Smaller in diameter
- Slower signal (no myelin)
- Single wrap of Schwann Cell
Process:
- Schwann cell starts to envelop multiple axons
- No myelin sheath wraps around the axons
What is the role of Oligodendrocytes in the CNS?
- Cause myelation in the CNS
- 1 oligodendrocytes = wraps many axons
What is the Node of Ranvier?
Basics:
- Unmyelinated region
- Found between 2 schwann cells
Function:
- Helps speed up the nerve conduction
- Saltatory conduction
- contains many Na channels
What happens during Nerve Injury and Regeneration?
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
What can we see in this image?
Autonomic ganglion in epicardium
- Nuclei of satellite cells
- Axon
- generally do not have a nucleus
What is this?
Meissner’s Plexus in Jejunum in the Submucosa
- Nerves in the GI
- helps w/ digestion & to move food along
- Surrounded by dense irregular CT
What is this?
Auerbach’s Plexus in Ileum
- Between layers of the muscularis externa
- Neuron
- surrounded by smooth muscle in LS & XS
What is this?
Cerebrum (CNS)
- Gray Matter (LEFT)
- Neuron Cell Bodies
- White Matter (RIGHT)
- Myelinated axons
What is this?
Cerebellum (CNS)
- Cerebellum (LEFT)
- Purkinje cells in Cerebellum (RIGHT)
What is this?
