Lab Exam Three: Histology of Nervous Tissue Flashcards
What does the CNS consist of?
brains and spinal cord enclosed and protected by the cranium and veterbrae column
What does the PNS consist of?
nerves and ganglia
What is a nerve?
a bundle of nerve fibers (axons) wrapped in fibrous connective tissue
What is a ganglion?
knotlike swelling in a nerve, where the cell bodies of neurons are concentrated
List the general coordination steps within the nervous system:
- Receiving
- Processing
- Issuing commands
The CNS processes information received, […] with past […] and determines what […], if any,, is appropriate.
relates it; experiences; response
The CNS issues commands primarily to […] and […] cells to carry out such responses.
muscle; glands
The sensory […] division carries signals from […] to the […].
afferent; receptors: brain
What two divisions are found within the afferent division?
- somatic sensory
2. visceral division
The somatic sensory division carries the signal…
from receptors in the skin, muscles, bones and joints
The visceral sensory division carries the signal…
mainly from the viscera of the thoracic and abdominal cavities
The motor […] division carries signals from the […] to […] and […] cells […] that carry out the body’s responses.
efferent; CNS; gland; muscles; effectors
The somatic motor division carries signals to the…
skeletal muscles
What are the two responses delivered by the somatic nervous system? Are they involuntary or voluntary?
- muscle contraction (voluntary control)
2. somatic reflexes (involuntary control)
The visceral motor division is also known as the….
autonomic nervous system (ANS)
What three places does the ANS carry signals to?
- glands
- cardiac muscle
- smooth muscle
The visceral motor division responses are known as […] these are […] done.
visceral reflexes; unconsiously
What are the two subdivisions found in the ANS (visceral)?
- sympathetic division
2. parasympathetic division
Sympathetic division tends to…
arouse the body for action
Parasympathetic division tends to…
have a calming effect
Neurosoma:
cell body of neuron that contains nucleus and organelles
Dendrites:
branched processes that receive signals from other cells
Neuroglia:
protect and assist the neurons
Structure– On one side of the soma is a mound called the […], from which the […] originates
axon hillock; axon (nerve fiber)
What encloses the axon?
- Schwann cells
2. myelin sheath
Structure– What is a terminal arborization? Where can this be found?
extensive complex of fine branches
found at the distal end of an axon
Structure– Each branch ends in a […] (terminal button), a little swelling that contains synaptic […] full of […] , the swelling also forms a […] with the next cell.
synaptic knob; vesicles; neurotransmitters; junction
What are the types of neurons?
- multipolar
- bipolar
- unipolar
- anaxonic
Have one axon and multiple dendrites:
multipolar neurons
Which type of neuron is the most common?
multipolar
Which type of neuron includes most neurons of the brain and spinal cord?
multipolar
Have one axon and one dendrite?
bipolar
What are some examples of bipolar neurons?
olfactory cells of the nasal cavity, certain neurons of the retina, and sensory neurons of the inner ear
Have only a single process leading away from the soma?
unipolar
An example of unipolar neurons:
neurons that carry sensory signals to the spinal cord
Have multiple dendrites but no axon?
anaxonic
Where can you find anaxonic neurons?
brain, retina, adrenal medulla
Which type of neurons communicate through their dendrites but do not produce action potentials?
axaonic
Glial cells […] together and provide a […] for the nervous tissue.
bind neurons; supportive framework
Whenever a […] is not in synaptic contact with another cell, it is […].
mature neuron; covered with glial cells
What is the purpose of covering mature neurons with glial cells?
prevents neurons from contacting each other except at points specialized for signal transmission
What are the the types of neuroglia?
- oligodendrocytes
- ependymal cells
- microglia
- astrocytes
- Schwann cells
- satellite cells
Which neuroglia are only part of the CNS?
4:
- oligodendrocytes
- ependymal cells
- microglia
- astrocytes
Oligodendrocytes:
(octopus) insulates the nerve fiber from the extracellular fluid (myelin sheath)
Ependymal cells:
resemble a cuboidal epithelium lining the internal cavities of the brain and spinal cord
Microglia:
small macrophages that develop from WBC called monocytes
Astrocytes:
(starlike) are the most abundant and constitute over 90% of the tissue in some areas of the brain
What are the functions of astrocytes?
- they form supportive framework (blood-brain barrier)
2. scar tissue and fill space formerly occupied by damaged neurons astrocytosis/sclerosis
What are the types of neuroglia of the PNS?
- Schwann cells (neurilemmocytes)
2. satellite cells
Schwann cells function:
- produce myelin sheath
2. assist in the regeneration of damaged fibers
Satellite function:
- provide electrical insulation around the soma
2. regulate the chemical environment of the neurons
Satellite cells:
surround the neurosomas in ganglia of the PNS
- *neurosomas = nerve cell bodies
- *ganglia = collection of neurosomas
What is the composition of the myelin sheath?
20% protein
80% lipid
Myelination:
production of the myelin sheath until completion in late adolescence
What are the two factors on the speed of nerve fibers?
- diameter of the fiber
2. presence/absence of myelin
Signal conduction occurs…
along the surface of a fiber NOT deep within its axoplasm
Why do large fibers conduct signals more rapidly?
they have more surface area