2 Divisions of the Nervous System
Components of CNS
Brain and Spinal Cord
Components of PNS
Cranial, spinal, peripheral nerves and ganglia
What are the 2 types of cells in the CNS and PNS?
2. Glial Cells
Features of a Multipolar Neuron (x6)
- Dendrites (2 or more)
- Cell Body
- Axon (one) - goes off into periphery
- Located in spinal cord
- Motor Neurons and CNS interneurons
- Most Neurons
Features of Bipolar Neuron (x4)
- Dendrite (1)
- Cell Body
- Axon (1)
- Sensory neurons of the retina, olfactory mucosa, and inner ear
Features of Unipolar Neurons
- Axon - Peripheral Process, Central Process
- Cell Body w/ Single short process
What are the types of neurons based on their functional role?
- Motor (efferent)
- Sensory (afferent)
- Interneuron (more than all other neurons combined)
Are Nissl bodies acidophilic of basophilic?
Basophilic –> lots of ribosomes (acid)
Why does the peikaryon have a euchromatic nucleus, very prominent nucleolus, and Nissl bodies?
Making lots of proteins
What is the Axon Hillock?
The thicker extension of the axon closest to the cell body
What maintains the structure of the neuron?
Neurofilaments (aka intermediate filaments) and neurotubules (aka microtubules)
What are the functions of the cytoskeleton in a neuron? (x2)
- Mechanical Support
2. Intracellular Trafficking
Where are neurotransmitters made? Where do they go? How do they get there?
- NT’s are made in the cell body
- They are stored in synaptic vesicles at the terminal end of the axon.
- They get there by traveling down the axon using the cytoskeleton (neurofilaments and neurotubules)
Is transport in the axon unidirectional or bidirectional?
What are the names for the modes of transportation up and down an axon?
- Anterograde Transport
2. Retrograde Transport
What is the plasma membrane of the axon called?
What is the cytoplasm of the axon called?
What does the axoplasm contain?
* Think MMR*
* No protein synth is made here - no ribosomes/rER
What are dendrites?
Elongated processes specialized to receive stimuli from other neurons at contact sites known as synapses
Which is longer, dendrite or axon?
Which process will be more numerous, dendrite or axon?
What is the dendritic spine?
The site of synaptic contact w/ other neurons
What is the purpose of dendrites and the dendritic spines?
Increase surface are to receive as much stim as possible
What happens when a neuron receives an impulse?
- An electrical impulse travels from the dendrite spine to the dendrite
- Then to the cell body
- Down the Axon
- NT is released
What does the NT do after it is released?
- Travels across the synaptic cleft
- Binds to a receptor on the post synaptic membrane
- Causes an effect
How to best see axons and dendrites on a microscopic image?
can also use basophilic stains like hematoxylin
What is in the space between neuronal cell bodies?
- Glial Cells
2. Glial and Neuronal Process (axons/dendites)
What are the major types of glial cells in the CNS?
- Ependymal Cells
What are the major types of glial cells in the PNS?
- Schwann Cells
- Satellite Cells
* oligodendrocytes and schwann cells have similar functions
Purpose of oligodendrocytes?
Form the myelin sheath in the CNS
Purpose of schwann cells?
Form the myelin sheath in the PNS
How can impulses down the axons travel faster?
Myelin sheath insulates parts of the axon and makes the impulse “jump” from node to node (of ranvier)
What is the primary component of myelin?
What glial cell myelinates parts of several axons in the CNS?
Where are schwann cells located and how are they different from oligodendrocytes?
- In the PNS
- Multiple schwann cells wrap themselves around a single axon, where as oligodendrocytes can myelinate several axons at the same tie
Compare the location of white matter to grey matter in the cranium
- White matter is located more centrally
2. Grey matter is located near the cortex
What is the main component of grey matter?
- Neuronal cell bodies
Compare the location of white matter to grey matter in the spinal cord
- White matter is located around the outside of the spinal cord
- Grey matter makes up the middle of the spinal cord
What is the most abundant glial cell in the CNS?
Features of astrocytes
- Very little cytoplasm
- Elongated or oval nuclei
- Numerous cytoplasic processes (star shaped = astro)
- Part of the BBB
Main functions of astrocytes?
- Regulate extracellular ion concentration
- Metabolic support for neurons
- Modulate Synaptic transmission
- Nervous system repair
* “Helps Mets Modulate Nerves”*
What are the perivascular feet and what are their function?
- Processes of the astrocyte that attach to blood supply
- Helps maintain the BBB
- Helps regulate local CNS blood flow
What cells line the Ventricles and Central Canal?
What are ependymal cells?
*similar to epithelial cells
Features of ependymal cells
- Ciliated - move fluid through the NS
- Have branches that go to parynchyma of the spinal cord
- Capable of division and migration into neuropil to form new neurons
How to tell ependymal cells apart from epithelial cells?
Ependymal cells do not have a basal lamina or basment membrane to anchor to
Functions of the microglia
- Clear away dying cells and help repair neuronal damage
* evenly distributed in grey and white matter*
What are “nerves” composed of?
Where are ethe cell bodies of the axons w/in a peripheral nerve located?
*ganglia are in the PNS
Features of the Dorsal Root Ganglion
- Contains Sensory (afferent) neurons
2. Have neuronal cell bodies - unipolar neurons
Features of satelite cells
- Restricted to ganglia
- Cover and support large neuronal cell bodies
- Located in PNS
What is in a peripheral nerve?
- Myelinated Axon
- Unmyelinated Axon
- Schwann Cell
- Connective tissue
What layer covers the entire nerve?
Why are nerve fibers wavy?
When you stretch, there is no damaging tension on the nerve