Chapter 11: Your Neurons and their Electrical Activity
1. What do parenchyma cells do?
Perform the function of an organ
2. What do stroma cells do? Support the parenchyma
3. What are the parenchyma cells of the nervous system? Neurons
4. Describe the neuron cell body:
Other parts of the cell extend outward from here
Contains single large nucleus
No centrioles—therefore it cannot divide
Rough ER is abundant – “chromatophilic substance” or “Nissl bodies”
Intermediate filament is neurofilament
Mitochondria in large numbers
5. Describe the dendrites
Cytoplasmic extensions from the cell body
Term dendrite means “branches” –very numerous and highly branched
(several hundred per cell)
Contain organelles
Large amounts of intermediate filaments give strength
6. Describe the axon:
Only one per neuron
Can be long
Plasma membrane is “axolemma”
Cytoplasm is “axoplasm”
7. What does a nerve fiber consist of?
Axon or dendrites and the myelin surrounding them
8. What is the difference between CNS and PNS?
CNS – central nervous system – brain and spinal cord
PNS – peripheral nervous system – all other nervous tissue
9. What are two types of stroma cells in the nervous system and
what do they do?
Oligodendrocytes – provide support to axon or dendrite of CNS
Neurolemmocytes – provides support to axon or dendrite of PNS
“Schwann cell”
10. How does the neurolemmocyte work?
Wraps layers of its membrane around the axon or dendrite until 20-30
layers have built up. Then it wraps its cell body around the myelin sheath,
this is called a neurolemma.
11. How does the oligodendrocyte work differently than the
neurolemmocyte?
They do not wrap their cell body around the myelin sheath
Each oligodendrocyte wraps portions of its membrane around several
nerve fibers, not one
12. How does the above effect nerve damage?
Axon can regrow if protected by neurolemma
Axon cannot regrow if protected by oligodendrocyte (damage to CNS
cannot be repaired
13. Compare continuous conduction to saltatory conduction.
Continuous – conduction in nonmyelinated fiber, action potential travels
like a wave
Saltatory – conduction in myelinated fiber, action potential skips along fiber
(gaps in myelin every mm or so). This is faster
14. Why does using an ice pack reduce pain?
Pain travels along sensory nerve fibers. When cooled, the message
travels slower, and therefore the brain receives fewer impuses
15.
Type of neuron
Sensory
Motor
Interneuron
Type of fiber
Direction of travel
Afferent fibers
From receptor to
CNS for
interpretation
Efferent fibers
Carry impulses
away from CNS to
effector
--------------------
Interconnect with
other neurons in
CNS (brain)
Make sure you saw the slides
Labeling of different neuron structures:
a. Bipolar
B. Unipolar
C. Multipolar
“Nerves” – bundles of axons
Nodes of Ranvier – short region of exposed axon between Schwann cells
on neurons of the peripheral nervous system
Bipolar Neurons – cell body has 2 processes (1 axon, 1 dendrite) found in
eyes, nose, ears
Unipolar Neurons – cell body has 1 process extending from it, which
divides. One branch associated with dendrites near peripheral body part, other
branch is entering brain or spinal cord
Multipolar Neurons – many processes from cell body (1 axon, others are
dendrites) found in brain, spinal cord
Astrocytes – star shaped, found between neurons and blood vessels,
provide support and aid metabolism, responds to injury of the brain, makes scar
tissue
Ependymal cell – cuboidal or columnar, have cilia, form inner lining of
spinal cord and form membrane covering inside of spaces within brain
Microglia – scattered through the CNS, phagocytize bacterial cells and cell
debris, increase in number if brain or spinal cord is injured